You missed us!
Here are some abstracts of talks that we have given.

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Chemically Advanced Nanolithography
M. E. Anderson, Department of Chemistry, The Pennsylvania State University, University Park, PA 16802-6300, USA

Chemically Advanced Nanolithography
M. E. Anderson, Department of Chemistry, The Pennsylvania State University, University Park, PA 16802-6300, USA

Chemically Advanced Nanolithography
M. E. Anderson, Department of Chemistry, The Pennsylvania State University, University Park, PA 16802-6300, USA

The Neurochip: An Advanced Nanomaterial for Small Molecule Capture of Biomolecule Binding Partners
A. Vaish, M. Schuster, M. Pishko, P. S. Weiss, and A. M. Andrews, Departments of Chemical Engineering, Chemistry, Physics, and Veterinary & Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have developed coupling chemistries to tether the prototype small molecule neurotransmitter serotonin and its carboxylated precursor, 5-hydroxytryptophan, to “insertion-directed” self-assembled monolayers on Au surfaces thus achieving dilute, non-phase separated ligand coverage. Coupling chemistries are verified by grazing angle FT-IR. Nonspecific binding has been largely eliminated by surrounding the tethered ligands with oligoethylene glycols. Good specificity of the surfaces has been demonstrated by quartz crystal microbalance measurements of specific antibody recognition of serotonin-functionalized surfaces and serotonin membrane receptor recognition of 5- hydroxytryptophan surfaces, the latter mimicking free solution bio-recognition of serotonin. “Neurochip” materials will be used to screen for nucleic acid aptamers, which will be utilized as molecular recognition elements in the construction of novel nanosensors for in vivo neurotransmitter sensing.

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

Nanoscale Patterning via Self- and Directed Assembly
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We combine self-assembly, phase separation, soft lithography, and selective removal/replacement in order to pattern monolayers at the nanometer scale. This is done via tailored intermolecular interactions, selection of processing order and having labile layers that can be displaced. This can also be done by controlling deposition or removal, by taking into account the strengths of the molecule-substrate interactions, the intermolecular interactions, the exposed functionality, and access to the substrate. We discuss a number of applications of these patterned films in biosensing and single molecule devices.

Probing Nanoscale Electronics Using Scanning Tunneling Microscopy
A. M. Moore, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

Understanding and Quantifying the Roles of Substrate-Mediated Interactions in Directing Surface Chemical Reactions
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Long-range intermolecular interactions mediated by the substrate are responsible for many effects on surfaces, including molecular ordering, formation of nanostructures, and aligning reactive intermediates in catalysis. We use scanning tunneling microscopy to probe the perturbations in the local (and extended) electronic structure directly, the resulting substrate-mediated interactions, and the effects of these interactions on the adsorbate structures and motion. We show that these interactions remain important in the placement of adsorbates at elevated temperatures and at ranges of tens of Ĺngstroms. Substrate-mediated interactions can also produce extended strings of intermediates that are not yet covalently bound. The prealignment of reactive intermediates by the substrate-mediated interactions can enhance reaction rates by many orders of magnitude. We describe our efforts in quantifying these interactions by recording both the locations and motion of many thousands of molecules. We describe a series of studies ranging in strength from systems with weak interactions (under 1 kJ/mole/molecule) all the way up to reactive systems.

Precise and Directed Assembly and Chemistry at the Atomic Scale
Sanjini U. Nanayakkara, Department of Chemistry, The Pennsylvania State University, University Park, PA 16802-6300, USA

Phthalocyaninato and Porphyrinato Rare-Earth (III) Double-Decker Complexes for Synthetic Molecular Rotors
Tomohide Takami, Tao Ye, and Paul S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Phthalocyanines and porphyrins are an important class of pigments that have fascinated scientists for their applications in various disciplines. They can form sandwich-type complexes with a range of rare-earth metals. The double-decker complexes have intriguing and unique electronic properties applied for molecular electronics, molecular information storage, and nonlinear optics, and are promising candidates for the controlled functional array of molecular switches and molecular motors. Here, we have shown our studies of the controlled molecular orientation of double-decker complexes at the interface of graphite surface and the 1-phenyloctane solution by scanning tunneling microscopy.

A Physical Model of Axonal Damage Due to Oxidative Stress
P. S. Weiss, A. E. Counterman, T. G. D'Onofrio, and A. M. Andrews Departments of Chemistry, Physics, and Veterinary & Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802-6300, USA

Background: Oxidative damage is implicated in the pathogenesis of neurodegenerative disorders, including Alzheimer’s, Parkinson’s and Huntington’s diseases, and in normal aging.
Objectives: We model oxidative stress in neurons using photogenerated radicals in a simplified membrane-encapsulated microtubule system.
Methods: Using fluorescence and differential interference contrast microscopies, we monitor photochemically-induced microtubule breakdown on the supported region of membrane in encapsulating synthetic liposomes as a function of lipid composition and environment.
Results: Degradation of vesicle-encapsulated microtubules is caused by attack from free radicals formed upon UV excitation of the lipid-soluble fluorescent probe, 6-(9-anthroyloxy)stearic acid. Probe concentration was typically limited to a regime in which microtubule degradation was slow. Microtubule degradation was monitored by changes in the observed protrusion of the membrane surface.
Conclusions: The kinetics of microtubule degradation are influenced by lipid saturation level, fluorescent probe concentration, and the presence of free radical scavengers. This system is sufficient to reproduce some degenerative morphologies found in vivo. We can use this system to investigate the roles of specific lipids and proteins in oxidative stress.

Selecting and Driving Nanoscale Assembly in Monolayer Films through Tailored Intermolecular Interactions
T. J. Mullen and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have developed, applied, and characterized molecules with varied intermolecular interaction strengths that control stability and impart directionality into patterned monolayers. In addition to employing molecules with tailored interactions, we have exploited self- and directed assembly techniques to fabricate, to register, and to functionalize chemical surface structures at the supramolecular 1-100 nm scale. We will highlight specific examples, including applications in molecular electronics and chemical patterning, where specifically tuned molecules were designed, custom self-assembly processing techniques were utilized, and the resulting chemical surface structures were characterized on both the ensemble and the molecular scales.

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
Amanda Moore and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

Quantitative Measurements of Substrate-Mediated Interactions
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Long-range intermolecular interactions mediated by the substrate are responsible for many effects on surfaces, including molecular ordering, formation of nanostructures, and aligning reactive intermediates in catalysis. We use scanning tunneling microscopy to probe the perturbations in the local (and extended) electronic structure directly, the resulting substrate-mediated interactions, and the effects of these interactions on the adsorbate structures and motion. We show that these interactions remain important in the placement of adsorbates at elevated temperatures and at ranges of tens of Ĺngstroms. Substrate-mediated interactions can also produce extended strings of intermediates that are not yet covalently bound. We describe our efforts in quantifying these interactions by recording both the locations and motion of many thousands of molecules. We describe a series of studies ranging in strength from systems with weak interactions (under 1 kJ/mole/molecule) all the way up to reactive systems.

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Quantitative Measurements of Single Molecule Dynamics: Intermolecular Potentials and Functional Properties
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We measure these interactions and the electronic perturbations that underly them using scanning tunneling microscopy. In these and other measurements, we collect substantial data sets in order to generate distributions with the statistics of ensemble-averaging techniques, while still retaining all the single molecule and environmental information. This requires new automated tools for acquisition and analyses. We also use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, once again comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

Investigating conformational switching using scanning tunneling microscopy
Christopher M. Pochas¹, Sanjini U. Nanayakkara¹, Meaghan M. Blake¹, P. S. Weiss¹, James M. Tour², Christine McGuiness³, Orlando Cabarcos³, Austin Flatt³, and David L. Allara⁴
Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA
²Department of Chemistry, Rice University, Houston, TX, USA
³Department of Chemistry, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have observed conductance switching for individual 4-{methyl-[4-(methyl-phenyl-amino)-phenyl]-amino}-benzenethiol (PAPAB) molecules inserted into octanethiolate self-assembled monolayers on Au {111} using scanning tunneling microscopy. Individual PAPAB molecules exhibited an intermediate conductance state between the maximum and minimum states, and showed preferential switch activity at negative tip bias voltages. The bias polarity preference is discussed in terms of the direction of the molecular dipole. Previously, we have shown that conductance switching is a result of a hybridization change at the molecule-substrate interface. In the case of PAPAB molecules, we hypothesize that the intermediate state may be a result of low energy barriers between conformational isomers of the molecule, which are attained by a hybridization change at the tertiary amino groups linking the aromatic rings.

Investigating conformational switching using scanning tunneling microscopy
Christopher M. Pochas¹, Sanjini U. Nanayakkara¹, Meaghan M. Blake¹, P. S. Weiss¹, James M. Tour², Christine McGuiness³, Orlando Cabarcos³, Austin Flatt³, and David L. Allara⁴
Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA
²Department of Chemistry, Rice University, Houston, TX, USA
³Department of Chemistry, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have observed conductance switching for individual 4-{methyl-[4-(methyl-phenyl-amino)-phenyl]-amino}-benzenethiol (PAPAB) molecules inserted into octanethiolate self-assembled monolayers on Au {111} using scanning tunneling microscopy. Individual PAPAB molecules exhibited an intermediate conductance state between the maximum and minimum states, and showed preferential switch activity at negative tip bias voltages. The bias polarity preference is discussed in terms of the direction of the molecular dipole. Previously, we have shown that conductance switching is a result of a hybridization change at the molecule-substrate interface. In the case of PAPAB molecules, we hypothesize that the intermediate state may be a result of low energy barriers between conformational isomers of the molecule, which are attained by a hybridization change at the tertiary amino groups linking the aromatic rings.

Measuring and controlling single molecule motions in supramolecular surface structures
Tao Ye¹, Tomohide Takami^1,2, Jianzhuang Jiang³, James M. Tour⁴, Byung-chan Yu⁴, and P. S. Weiss^1
1Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA
²Visionarts, Inc.
³Shandong University
⁴Department of Chemistry, Rice University, Houston, TX, USA

Measuring and controlling motions, as well as extracting useful work out of single molecules is at the forefront of nanoscale science. To achieve this end, we need to constrain the degrees of freedom of these molecules. We seek to understand and to control rotary motions in supramolecular surface structures of double decker sandwich complexes (DDs), where rings of porphyrin derivatives are connected by a lanthanide center. We control spacings and orientations of DDs using both molecular design and self-assembly. The location of the rotor molecules can be controlled via scanning tunneling microcopy (STM) tip manipulation. STM observations of the DDs in a controlled local environment reveal that the rotary motions proceed via activated hopping. We discuss our efforts to control rotation through photoexcitation, electrochemistry, and chemical binding.

Nanoscale study of heterogeneous brain architectures: Understanding disease mechanisms and devising novel therapeutics
Anne M. Andrews, Mitchell J. Shuster, Amit U. Vaish, and P. S. Weiss, Departments of Chemistry, Physics, and Veterinary & Biomedical Science, The Pennsylvania State University, University Park, PA 16802-6300, USA

In order to investigate central nervous system interneuronal signaling at the length and time scales pertinent the to intrinsically encoded information, and to relate this information to complex behavior, brain disorders, and new treatments and prevention strategies, chemically specific in vivo sensors are required that approach the size of a synapse (ca. 20 nm) and that respond in milliseconds. We have developed methods to tether neurotransmitter molecules to highly optimized biospecific self-assembled monolayer surfaces. We have demonstrated that these surfaces selectively recognize large biomolecule binding partners, including antibodies and receptor proteins. We are using these neurotransmitter-functionalized surfaces to capture and identify high affinity molecular recognition elements, which we will couple to semiconductor nanowire or carbon nanotube platforms to create ultra small, multiplexed sensing devices having high sensitivity and fast response times. This has the potential to revolutionize in vivo sensing. A second overarching goal of this project is to interface multiplexed biospecific neurotransmitter-functionalized surfaces to mass spectrometry for the detection, structural identification, and association of functionally related proteome subsets.

Attraction at a Distance: The Effects of Substrate-Mediated Interactions on Surface Chemistry
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Long-range intermolecular interactions mediated by the substrate are responsible for many effects on surfaces, including molecular ordering, formation of nanostructures, and aligning reactive intermediates in catalysis. We use scanning tunneling microscopy to probe the perturbations in the local (and extended) electronic structure directly, the resulting substrate-mediated interactions, and the effects of these interactions on the adsorbate structures and motion. We show that these interactions remain important in the placement of adsorbates at elevated temperatures and at ranges of tens of Ĺngstroms. Substrate-mediated interactions can also produce extended strings of intermediates that are not yet covalently bound. We describe our efforts in quantifying these interactions by recording both the locations and motion of many thousands of molecules. We describe a series of studies ranging in strength from systems with weak interactions (under 1 kJ/mole/molecule) all the way up to reactive systems.

Assembly and rotary motions of sandwich rare earth complexes
Tao Ye¹, Tomohide Takami^1,2, Jianzhuang Jiang³, and P. S. Weiss^1
1Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA
²Visionarts, Inc.
³Shandong University

We seek to understand and to control rotary motions in supramolecular surface structures of double decker sandwich complexes (DDs), where rings of porphyrin derivatives are connected by a lanthanide center. To achieve this end, we need to constrain their degrees of freedom. We control spacings and orientations of DDs using both molecular design and self-assembly. The location of the rotor molecules can be controlled via scanning tunneling microcopy (STM) tip manipulation. STM observations of the DDs in a controlled local environment reveal that the rotary motions proceed via activated hopping. We discuss our efforts to control rotation through photoexcitation, electrochemistry, and chemical binding.

Quantitative Measurements of Single Molecule Dynamics: Intermolecular Potentials and Functional Properties
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Advances in Molecular Rulers and Chemical Patterning
Nate Hohman and Charan Srinivasan, Departments of Chemistry, Engineering Science & Mechanics, and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

The Neurochip: An Advanced Nanomaterial for Small Molecule Capture of Biomolecule Binding Partners
Amit Vaish, Mitchell Shuster, Michael Pishko, Paul S. Weiss, and Anne Milasincic Andrews, Departments of Chemical Engineering, Chemistry, Physics and Veterinary & Biomedical Science, The Pennsylvania State University, University Park, PA 16802-6300, USA

Selecting and Driving Nanoscale Assembly in Monolayer Films through Tailored Intermolecular Interactions
TJ Mullen and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Physical properties and organization of model cell membranes
Julia J. Heetderks and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

The Neurochip: An Advanced Nanosurface for Small Molecule Capture of Biomolecule Binding Partners
M. J. Shuster, A. U. Vaish, T. J. Mullen, P. S. Weiss, and A. M. Andrews, Departments of Chemistry, Physics, and Veterinary & Biomedical Science, The Pennsylvania State University, University Park, PA 16802-6300, USA

Single molecule placement of serotonin in self-assembled monolayers allows selective recognition by antibodies and native transmembrane receptors
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Quantitative Measurements of Single Molecule Dynamics: Intermolecular Potentials and Functional Properties
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We measure these interactions and the electronic perturbations that underly them using scanning tunneling microscopy. In these and other measurements, we collect substantial data sets in order to generate distributions with the statistics of ensemble-averaging techniques, while still retaining all the single molecule and environmental information. This requires new automated tools for acquisition and analyses. We also use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, once again comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

Advances in the Creation, Development and Application of Patterned Neurotransmitter-Functionalized Surfaces
Mitchell Shuster, Amit Vaish, and TJ Mullen, The Pennsylvania State University, University Park, PA 16802-6300, USA

Tad Daniel Advances in Analytical Tools and Methods: What the JEOL Multitool Can Do for Us

Pengpeng Zhang Nanodevice Fabrication on Si Nanowires Using Assembled Nanostructures

Selecting and Driving Nanoscale Assembly in Monolayer Films through Tailored Intermolecular Interactions
T. J. Mullen and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have developed, applied, and characterized molecules with varied intermolecular interaction strengths that control stability and impart directionality into patterned monolayers. In addition to employing molecules with tailored interactions, we have exploited self- and directed assembly techniques to fabricate, to register, and to functionalize chemical surface structures at the supramolecular 1-100 nm scale. We will highlight specific examples, including applications in molecular electronics and chemical patterning, where specifically tuned molecules were designed, custom self-assembly processing techniques were utilized, and the resulting chemical surface structures were characterized on both the ensemble and the molecular scales.

Kinetics and Mechanism of Displacement in 1-Adamantanethiolate Self-Assembled Monolayers
H.M. Saavedra, C. M. Barbu, T. J. Mullen, V. H. Crespi, and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have investigated the kinetics of solution-phase displacement of 1-adamantanethiolate self-assembled monolayers on Au{111} by ndodecanethiol molecules using Fourier transform infrared-external reflectance spectroscopy (FTIR-ERS) and scanning tunneling microscopy (STM). The displacement reaction can be divided into three regions: a fast insertion and nucleation of small n-dodenathiolate islands around defects in the 1-adamantanethiolate monolayer; an island growth regime in which the rate of growth is dependent on the perimeter of the island; and a final slow ordering of the n-dodecanethiolate domains leading to denser and more crystalline n-dodenathiolate domains. A study of displacement as a function of concentration revealed that the full displacement of 1-adamantanethiolate monolayers has a [n-dodecanethiol] x time² dependence. An analytical model has been derived to describe the displacement process, and using this model a rate constant has been determined.

Selecting and Driving Nanoscale Assembly in Monolayer Films through Tailored Intermolecular Interactions
A. M. Moore and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have built a scanning tunneling microscope (STM) capable of measuring the response of surfaces excited with microwave frequencies (up to 20 GHz) at sub-nanometer resolution. Two frequencies are applied to the STM tip and the nonlinearity of the tunnel junction mixes the frequencies, generating new signals including at the difference of the frequencies applied. This ultrahigh resolution (<1 nm) profiling tool enhances and complements what is obtained through current metrology tools and will support semiconductor processing as the size scale of devices continues to decrease. It will allow us to study single molecule rotations excited at microwave frequencies and also allow us subsurface properties of thin films and cluster-assembled materials.

Advances in Molecular Rulers and Chemical Patterning
Charan Srinivasan, Departments of Chemistry, Engineering Science & Mechanics, and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Nanopatterning using Molecular Ruler Resists
Charan Srinivasan¹, Mary E Anderson², James N Hohman², Paul S Weiss² and Mark W Horn^1
1Department of Engineering Science and Mechanics
²Departments of Chemistry and Physics
The Pennsylvania State University, University Park, PA 16802, USA

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

Nanoscale assembly and machinery
Tao Ye, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Significant progress has been made in creating synthetic molecules capable of internal conformational changes in response to external stimuli in the solution phase. However, their single molecule properties in technologically relevant environments, such as at interfaces and in nanoscale assemblies remain poorly understood. We have probed and controlled molecular machines down to the single molecule level. I will describe three types of molecular motions, rotary motion by double-decker rare-earth complexes, linear motion by rotaxanes, and light-driven switching motion by azobenzene derivatives. Critical to single molecule observations and control are purposeful molecular design and nanoscale assembly that determine the orientation, spacing and steric interactions of these single molecule machines. Molecules and assemblies can perform desired motion only when they are properly interfaced to their nanoscale environments.

Exploring and Controlling the Atomic-Scale World: Directing Chemical Reactions and Atomically Precise Structures
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Nanoscale assembly and machinery
Tao Ye, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Significant progress has been made in creating synthetic molecules capable of internal conformational changes in response to external stimuli in the solution phase. However, their single molecule properties in technologically relevant environments, such as at interfaces and in nanoscale assemblies remain poorly understood. I will describe our recent efforts in probing and controlling molecular machines down to the single molecule level. Three types of molecular motions will be presented: rotary motion by double-decker rare-earth complexes, linear motion by rotaxanes, and light-driven switching motion by azobenzene derivatives. Critical to single molecule observations and control are purposeful molecular design and nanoscale assembly that determine the orientation, spacing and steric interactions of these single molecule machines.

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Selecting and Driving Nanoscale Assembly through Tailored Intermolecular Interactions
T. J. Mullen and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have developed, applied, and characterized molecules with varied intermolecular interaction strengths that control stability and impart directionality into patterned monolayers. In addition to employing molecules with tailored interactions, we have exploited self- and directed assembly techniques to fabricate, to register, and to functionalize chemical surface structures at the supramolecular 1-100 nm scale. We will highlight specific examples, including chemical patterning and functionalized bioselective surfaces, where specifically tuned molecules were designed, custom self-assembly processing techniques were utilized, and the resulting chemical surface structures were characterized on both the ensemble and the molecular scales.

Molecular Ruler Nanolithography
Charan Srinivasan, Beth Anderson, Nate Hohman, Paul S. Weiss and Mark Horn, Departments of Chemistry, Physics, and Engineering Science & Mechanics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
Paul S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We employ some of these approaches in directed assembly to enable bioselective and biospecific binding. We also selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

Hybrid Strategies in Nanolithography and Chemical Patterning
Charan Srinivasan, Mark Horn, Paul S. Weiss, Departments of Chemistry, Physics, and Engineering Science & Mechanics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use top-down fabrication techniques, such as conventional lithography and softlithography, in conjunction with bottom-up chemical self-assembly and apply it to nanolithography¹ and chemical patterning. Here, we will describe recent advances in molecular-ruler nanolithography, and in three new techniques for chemical patterning which enhance the sophistication and resolution of microcontact printing (µCP) – microdisplacement printing (µDP),² microcontact insertion printing (µCIP),³ and lithography-assisted chemical patterning.⁴

Molecular-ruler nanolithography uses radiation-sensitive polymeric resists in combination with self-assembled multilayers to create nanostructures with sub-30-nm dimensions. This technique is attractive for its parallel processing, high precision, and low capital investment.

Applications of this technology include the fabrication of nanoscale device structures,⁵ creation of nanopatterns on quartz for use as molds in imprint lithography,⁶ and in doubling the spatial density of features created by conventional lithographic techniques.⁷

One of the limitations of µCP is the tendency of the ink molecules to spread across the surface.⁸ Microdisplacement printing circumvents this by utilizing a preassembled, labile self-assembled monolayer (SAM) of 1-adamantanethiol (AD) on the surface. The AD SAM is selectively displaced by the more strongly bound ink molecule from the raised regions of a patterned elastomeric stamp and simultaneously prevents the lateral diffusion of the ink molecule. This improves the fidelity of chemical patterns created by µDP.² Microcontact insertion printing is a new technique for the creation of chemical patterns of inserted molecules at dilute coverages (<10%). This insertion places the ink molecule in defects of the host SAM only in the raised regions of an elastomeric stamp. The surface concentration of inserted molecules can be controlled based on the stamping time and concentration of the ink molecule.³

Lithography-assisted chemical patterning utilizes a robust lithographic resist (LOR) that is capable of withstanding self-assembly deposition conditions to create high-quality chemical patterns. The ability to pattern chemical functionalities without intercalation and parallel processing are some of the unique advantages of this technique.⁴

1. A. Hatzor and P. S. Weiss, Science 291, 1019 (2001).
2. A. A. Dameron, J. R. Hampton, R. K. Smith, T. J. Mullen, S. D. Gillmor, P. S. Weiss, Nano Lett. 5, 1834 (2005).
3. T. J. Mullen, C. Srinivasan, J. N. Hohman, S. D. Gillmor, M. J. Shuster, M. W. Horn, A. M. Andrews, P. S. Weiss, Appl. Phys. Lett. 90, 063114 (2007).
4. M. E. Anderson, C. Srinivasan, J. N. Hohman, E. M. Carter, M. W. Horn, P. S. Weiss, Adv. Mater. 18, 3258 (2006).
5. C. Srinivasan, M. E. Anderson, E. M. Carter, J. N. Hohman, S. S. N. Bharathwaja, S. Trolier-Mckinstry, P. S. Weiss, M. W. Horn, J. Vac. Sci. Technol. B 24, 3200 (2006).
6. C. Srinivasan, J. N. Hohman, M. E. Anderson, P. S. Weiss, M. W. Horn, (submitted for publication).
7. C. Srinivasan, J. N. Hohman, M. E. Anderson, P. P. Zhang, P. S. Weiss, M. W. Horn, (submitted for publication).
8. Y. Xia and G. M. Whitesides, Angew. Chem., Int. Ed. 37, 551 (1998).

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We employ some of these approaches in directed assembly to enable bioselective and biospecific binding. We also selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Patterned Neurotransmitters: Novel Approaches through Soft Lithography
T. J. Mullen, P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Although photolithography has made large advances over the past 40 years and is the workhorse of the semiconductor industry, it is costly, requires specialized facilities, and cannot fabricate reproducible structures with molecular-scale organization. Recently, techniques similar to rubber stamping, called "soft lithography," have been developed to minimize these problems by relying on soft materials, such as polymers, to transfer patterns to surfaces. However, these flexible materials are limited by feature size and the diffusion of the patterned ink. We have utilized and exploited preexisting monolayer films to circumvent these limitations to increase the sophistication and to enhance the precision of a common soft-lithography technique, microcontact printing. We are currently using these advanced soft-lithography techniques to pattern individual small-molecule probes, such as serotonin and other neurotransmitters, to capture large biological molecules selectively from biologically important environments.

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We employ some of these approaches in directed assembly to enable bioselective and biospecific binding. We also selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

FULL ABSTRACT

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales.1-32 We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns,13-29 and to control and to stabilize function.3,4,6,7,9-11 These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales.

We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film.17-19,21-23 We employ some of these approaches in directed assembly to enable bioselective and biospecific binding.28 We also selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means.3-12

Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the individual measurements. We quantitatively compare the conductances of molecule-substrate junctions.30-32 We demonstrate the importance of these junctions in conductance switching of single molecules.3-11

SINGLE-MOLECULE MEASUREMENTS

One of our goals is to obtain sufficient numbers of measurements such that we have statistics comparable to ensemble-averaging measurements, and yet retain all the heterogeneity of single-molecule measurements for further sorting and analysis. We originally developed this methodology for our work in single molecular electronics,3-7,9-11 but have since applied it in other areas such as for quantifying substrate-mediated interactions between adsorbed atoms and molecules.33-35

This work is done with highly stabilized scanning tunneling microscopes (STMs) so that the same area can be watched for days at a time, or so that a single molecule can be measured with high time resolution while keeping the probe tip held fixed. While imaging, we can record switching from the millisecond to the hour and day time scales. While holding the probe tip fixed, we are able to record switching from microseconds to seconds. This gives us a dynamic range of eleven orders of magnitude in time scale.

A particular advantage of these methods has been the ability to vary molecular design to test hypothesized functional mechanisms (vide infra).

SINGLE-MOLECULE SWITCHES

We have been able to design the key chemical functionality into and out of molecules in order to elucidate the mechanism of function.11 In oligophenylene ethynylene oligomers, we have found that changes in the hybridization of the molecule-surface bond as the molecules tilt in response to a locally applied electric field or tilt stochastically are responsible for changes in the conductance of the molecule-surface assemblies.3-11 We have shown that oligoanilines and oligothiophenes switch in a similar manner. By designing molecules with varying dipole moment magnitudes and directions, we have been able to assign the “on” and “off” states as upright (near normal) and tilted, respectively (see Figure 1).7,10,11 This is in contrast both to many other mechanisms proposed and to incorrect assignment of the underlying phenomena responsible for conductance switching.

Figure 1. By designing molecules with dipoles oriented one way or another (left vs. right), the direction of the electric field that switch them can be inverted.10 Note that surrounding monolayer matrices are designed to enable hydrogen bonding interactions to stabilize one or both conductance states.7,10 From the dipole direction and switching, we are able to assign the “on” conductance states for these molecules as near normal to the surface and “off” conductance states as tilted. The hybridization of the molecule surface bond is assigned as being responsible for switching.3-11 If the molecules lack sufficient dipole magnitude, then they switch stochastically, but are not readily switched with applied electric fields. (Graphic from ref. 10.)

One of the underlying questions is the role of the substrate. It is possible and indeed likely that substrate atoms relax when the hybridization of the molecule-surface bond changes. This would affect the conductance of the assembly, as changes in conductance are known to occur when atoms are displaced from their equilibrium positions.36 There is not yet a means to determine the coordination of the atom that makes up the chemical, physical and electronic contact with the substrate, nor the extent of this possible substrate relaxation.

A recent tantalizing result has been that a precise assembly of an inserted dithiol molecule tethering a cluster with a ligand-stabilized Au11 cluster exhibits spectral diffusion when measured repeatedly. For both Au11 and Au101, the consensus (averaged) spectra over a single cluster and also over many like clusters reproduce literature values of ensemble-averaged spectra. However, repeated ultrastable STM measurements at 4 K over single clusters (and thus by definition monodisperse samples) show widely varying energy gaps and spectra that hop and repeat between families of tunneling spectra.

SINGLE-MOLECULE MOTORS

We have also approached the assembly and measurement of single-molecule motors. These motors function on the basis of electric field, photo-activation, ion binding, and electrochemical activation.37-40 We have employed several families of molecules for these purposes: double-decker porphyrins and phthalocyanines,37-39 caltrops, rotaxanes, and hybrids of oligophenylene ethynylenes with other functionalities.

We have developed means to control the spacings of assemblies of motors by controlling the ligand functionality, the mixtures of molecules, and the manipulation of the molecules.37-39 These methods, as well as covalently coupling bases to define separations, will enable us to study the complex interactions between interacting moving molecules.41

ACKNOWLEDGMENTS

We gratefully acknowledge the continuing support of NSF, the Center for Nanoscale Science (a NSF MRSEC), the Penn State node of the NSF-supported National Nanofabrication Infrastructure Network, AFOSR, ARO, DARPA, NIST, ONR, Sigma-Aldrich and Visionarts. This work was performed by many of the students, post-docs, and visitors of the Weiss group and of our long-time collaborators Anne Andrews, Dave Allara, Dennis Arnold, Vin Crespi, Mark Horn, Jim Hutchison, Ken-ichi Sugiura, and Jim Tour.

REFERENCES

1. Bumm, L. A.; Arnold, J. J.; Cygan, M. T.; Dunbar, T. D.; Burgin, T. P.; Jones, L.; Allara, D. L.; Tour, J. M.; Weiss, P. S. Science 1996, 271, 1705.
2. Cygan, M. T.; Dunbar, T. D.; Arnold, J. J.; Bumm, L. A.; Shedlock, N. F.; Burgin, T. P.; Jones, L.; Allara, D. L.; Tour, J. M.; Weiss, P. S. J. Am. Chem. Soc. 1998, 120, 2721.
3. Donhauser, Z. J.; Mantooth, B. A.; Kelly, K. F.; Bumm, L. A.; Monnell, J. D.; Stapleton, J. J.; Price, D. W.; Rawlett, A. M.; Allara, D. L.; Tour, J. M.; Weiss, P. S. Science 2001, 292, 2303.
4. Donhauser, Z. J.; Mantooth, B. A.; Pearl, T. P.; Kelly, K. F.; Nanayakkara, S. U.; Weiss, P. S. Jpn. J. Appl. Phys. 2002, 41, 4871.
5. Mantooth, B. A.; Donhauser, Z. J.; Kelly, K. F.; Weiss, P. S. Rev. Sci. Instrum. 2002, 73, 313.
6. Mantooth, B. A.; Weiss, P. S. Proc. IEEE 2003, 91, 1785.
7. Lewis, P. A.; Inman, C. E.; Yao, Y. X.; Tour, J. M.; Hutchison, J. E.; Weiss, P. S. J. Am. Chem. Soc. 2004, 126, 12214.
8. Dameron, A. A.; Ciszek, J. W.; Tour, J. M.; Weiss, P. S. J. Phys. Chem. B 2004, 108, 16761.
9. Moore, A. M.; Mantooth, B. A.; Donhauser, Z. J.; Maya, F.; Yao, Y.; Price, D. W.; Tour, J. M.; Weiss, P. S. Nano Lett. 2005, 5, 2292.
10. Lewis, P. A.; Inman, C. E.; Yao, Y. X.; Tour, J. M.; Hutchison, J. E.; Weiss, P. S. J. Am. Chem. Soc. 2005, 127, 17421.
11. Moore, A. M.; Dameron, A. A.; Mantooth, B. A.; Smith, R. K.; Fuchs, D. J.; Ciszek, J. W.; Maya, F.; Yao, Y.; Tour, J. M.; Weiss, P. S. J. Am. Chem. Soc. 2006, 128, 1959.
12. Smith, R. K.; Nanayakkara, S. U.; Woehrle, G. H.; Pearl, T. P.; Blake, M. M.; Hutchison, J. E.; Weiss, P. S. J. Am. Chem. Soc. 2006, 128, 9266.
13. Bumm, L. A.; Arnold, J. J.; Charles, L. F.; Dunbar, T. D.; Allara, D. L.; Weiss, P. S. J. Am. Chem. Soc. 1999, 121, 8017.
14. Weck, M.; Jackiw, J. J.; Weiss, P. S.; Grubbs, R. H. J. Am. Chem. Soc. 1999, 121, 4088.
15. Hatzor, A.; Weiss, P. S. Science 2001, 291, 1019.
16. Weiss, P. S. Nature 2001, 413, 585.
17. Smith, R. K.; Reed, S. M; Monnell, J. D.; Lewis, P. A.; Clegg, R. S.; Kelly, K. F.; Bumm, L. A.; Hutchison, J. E.; Weiss, P. S. Journal J. Phys. Chem. B 2001, 105, 1119.
18. Lewis, P. A.; Smith, R. K.; Kelly, K. F.; Bumm, L. A.; Reed, S. M; Clegg, R. S.; Gunderson, J. D.; Hutchison, J. E.; Weiss, P. S. Journal J. Phys. Chem. B 2001, 105, 10630.
19. Lewis, P. A.; Donhauser, Z. J.; Mantooth, B. A.; Smith, R. K.; Bumm, L. A.; Kelly, K. F.; Weiss, P. S. Nanotechnology 2001, 12, 231.
20. Donhauser, Z. J.; Weiss, P. S.; Price, D. W.; Tour, J. M. J. Am. Chem. Soc. 2003, 125, 11462.
21. Dameron, A. A.; Charles, L. F.; Weiss, P. S. J. Am. Chem. Soc. 2005, 127, 8697.
22. Dameron, A. A.; Hampton, J. R.; Smith, R. K.; Mullen, T. J.; Gillmor, S. D.; Weiss, P. S. Nano Lett. 2005, 5, 1834.
23. Mullen, T. J.; Dameron, A. A.; Weiss, P. S. J. Phys. Chem. B 2006, 110, 14410.
24. Anderson, M. E.; Tan, L. P.; Mihok, M.; Tanaka, H.; Horn, M. W.; McCarty, G. S.; Weiss, P. S. Adv. Mater. 2006, 18, 1020.
25. Anderson, M. E.; Srinivasan, C.; Hohman, J. N.; Carter, E. M.; Horn, M. W.; McCarty, G. S.; Weiss, P. S. Adv. Mater. 2006, 18, 3258.
26. Mullen, T. J.; Srinivasan, C.; Hohman, J. N.; Gillmor, S. D.; Shuster, M. J.; Horn, M. W.; Andrews, A. M.; Weiss, P. S. Appl. Phys. Lett., 2007, 40, 063114.
27. Fuchs, D. J.; Weiss, P. S. Nanotechnology 2007, 18, 044021.
28. Mullen, T. J.; Dameron, A. A.; Andrews, A. M.; Weiss, P. S. Aldrich. Acta 2007, 40, 21.
29. Smith, R. K.; Lewis, P. A.; Weiss, P. S. Prog. Surf. Sci. 2004, 75, 1.
30. Bumm, L. A.; Arnold, J. J.; Dunbar, T. D.; Allara, D. L.; Weiss, P. S. J. Phys. Chem. B 1999, 103, 8122.
31. Monnell, J. D.; Stapleton, J. J.; Jackiw, J. J.; Dunbar, T. D.; Reinerth, W. A.; Dirk, S. M.; Tour, J. M.; Allara, D. L.; Weiss, P. S. J. Phys. Chem. B 2004, 108, 9834.
32. Monnell, J. D.; Stapleton, J. J.; Dirk, S. M.; Reinerth, W. A.; Dirk, S. M.; Tour, J. M.; Allara, D. L.; Weiss, P. S. J. Phys. Chem. B 2004, 108, 20343.
33. Sykes, E. C. H.; Mantooth, B. A.; Han, P.; Donhauser, Z. J.; Weiss, P. S. J. Am. Chem. Soc. 2005, 127, 7255.
34. Kulawik, M.; Rust, H.-P.; Heyde, M.; Mantooth, B. A.; Weiss, P. S.; Freund, H.-J. Suf. Sci. Lett. 2005, 590, L253.
35. Mantooth, B. A.; Sykes, E. C. H.; Han, P.; Moore, A. M.; Donhauser, Z. J.; Crespi, V. H.; Weiss, P. S. J. Phys. Chem. C 2007, in press.
36. Lang, N. D.; Avouris, Ph. Phys. Rev. Lett. 1998, 81, 3515.
37. Takami, T.; Arnold, D. P.; Fuchs, A. V.; Will, G. D.; Goh, R.; Waclawik, E. R.; Bell, J. M.; Weiss, P. S.; Sugiura, K.-I.; Liu, W.; Jiang, J. J. Phys. Chem. B 2006, 110, 1661.
38. Takami, T. Wang, R.; Jiang, J.; Weiss, P. S. J. Am. Chem. Soc. 2006, 128, 10984.
39. Takami, T.; Ye, T.; Arnold, D. P.; Sugiura, K.-I.; Wang, R.; Jiang, J.; Weiss, P. S. J. Phys. Chem. C 2006, 111, 2077.
40. Ye, T.; Takami, T.; Huang, T. J.; Saha, S.; Stoddart, J. F.; Weiss, P. S. In preparation.
41. Kottas, G. S.; Clarke, L. I.; Horinek, D.; Michl, J. Chem. Rev. 2005, 105, 2181.

Selecting and Driving Nanoscale Assembly in Monolayer Films through Tailored Intermolecular Interactions
TJ Mullen, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have developed, applied, and characterized molecules with varied intermolecular interaction strengths that control stability and impart directionality into patterned monolayers. In addition to employing molecules with tailored interactions, we have exploited self- and directed assembly techniques to fabricate, to register, and to functionalize chemical surface structures at the supramolecular 1-100 nm scale. We will highlight specific examples, including chemical patterning and functionalized bioselective surfaces, where specifically tuned molecules were designed, custom self-assembly processing techniques were utilized, and the resulting chemical surface structures were characterized on both the ensemble and the molecular scales.

Chemically Advanced Nanolithography
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Self- and Directed Assembly for Advanced Patterning via Soft Lithography
T. J. Mullen, C. Srinivasan, H. M. Saavedra, J. N. Hohman, A. A. Dameron, J. R. Hampton, M. J. Shuster, S. D. Gillmor, A. M. Andrews, M. W. Horn, V. H. Crespi, and P. S. Weiss, Departments of Chemistry, Engineering Science & Mechanics, Physics, and Veterinary & Biomedical Science, The Pennsylvania State University, University Park, PA 16802-6300, USA

Hybrid Strategies for Nanolithography and Chemical Patterning
C. Srinivasan, J. N. Hohman, P. Zhang, M. J. Shuster, A. M. Andrews, M. W. Horn, and P. S. Weiss, Departments of Chemistry, Engineering Science & Mechanics, Physics, and Veterinary & Biomedical Science, The Pennsylvania State University, University Park, PA 16802-6300, USA

Self- and Directed Assembly for Advanced Patterning
H. M. Saavedra, T. J. Mullen, C. M. Barbu, M. Kim, C. Srinivasan, J. N. Hohman, A. A. Dameron, V. H. Crespi, and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Biospecific Recognition of Small Molecules via Insertion-Directed Self-Assembly
M. J. Shuster, A. Vaish, T. J. Mullen, J. E. McManigle, J. M. Hinds, P. S. Weiss, and A. M. Andrews, Departments of Chemistry, Physics, and Veterinary & Biomedical Science, The Pennsylvania State University, University Park, PA 16802-6300, USA

Measuring and Controlling Single-Molecule Motions in Supramolecular Structures
T. Ye, A. Kumar, T. Takami, C. Barbu, V. H. Crespi, T. Huang, J. F. Stoddart, and P. S. Weiss, Departments of Chemistry, Engineering Science & Mechanics, and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA, and Department of Chemistry, UCLA, Los Angeles, CA, USA.

Selecting and Driving Nanoscale Assembly in Monolayer Films through Tailored Intermolecular Interactions
T. J. Mullen, P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have developed, applied, and characterized molecules with varied intermolecular interaction strengths that control stability and impart directionality into patterned monolayers. In addition to employing molecules with tailored interactions, we have exploited self- and directed assembly techniques to fabricate, to register, and to functionalize chemical surface structures at the supramolecular 1-100 nm scale. We will highlight specific examples, including chemical patterning and functionalized bioselective surfaces, where specifically tuned molecules were designed, custom self-assembly processing techniques were utilized, and the resulting chemical surface structures were characterized on both the ensemble and the molecular scales.

Self- and Directed Assembly of Functional Nanoscale Structures
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the films. We employ some of these approaches in directed assembly to enable bioselective and biospecific binding. We develop hybrid strategies to create chemical patterns down to the single-molecule scale.

Measurements and Mechanism of Single Molecule Conductance Switching
A. M. Moore, Z. J. Donhauser, P. A. Lewis, B. A. Mantooth, and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Selecting and Driving Nanoscale Assembly in Monolayer Films through Tailored Intermolecular Interactions
T. J. Mullen, P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have developed, applied, and characterized molecules with varied intermolecular interaction strengths that control stability and impart directionality into patterned monolayers. In addition to employing molecules with tailored interactions, we have exploited self- and directed assembly techniques to fabricate, to register, and to functionalize chemical surface structures at the supramolecular 1-100 nm scale. We will highlight specific examples - microdisplacement printing, microcontact insertion printing, and functionalized bioselective surfaces - where specifically tuned molecules were designed, custom self-assembly processing techniques were utilized, and the resulting chemical surface structures were characterized on both the ensemble and the molecular scales. Traditional microcontact printing is limited to molecules with sufficient intermolecular interactions to prevent lateral diffusion across the surface. To circumvent this problem, we have developed microdisplacement printing where a labile monolayer of 1-adamantanethiolate is utilized to limit diffusion of patterned molecules. With microdisplacement printing, the 1-adamantanethioalte is displaced only where the elastomeric stamp and substrate are in contact and prevents lateral diffusion both during and after patterning. Rather than complete displacement as with microdisplacement printing, we have developed microcontact insertion printing where isolated molecules are inserted into the defects of a preexisting monolayer in regions that are patterned by an elastomeric stamp. By tuning the degree of molecular insertion into and exchange between the patterned molecules and the preexisting self-assembled monolayer, we have precisely controlled the isolation and dilution of the inserted molecules and the molecular composition of the chemical pattern. Finally, we have utilized and employed microcontact insertion printing, to fabricate chemical films with patterned small-molecule probes that are optimally diluted and isolated to resist nonspecific binding and can selectively capture large biomolecules in a competitive environment.

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We employ some of these approaches in directed assembly to enable bioselective and biospecific binding. We also selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We employ some of these approaches in directed assembly to enable bioselective and biospecific binding. We also selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

In Search of Brain Nanobiosensors: Small Molecule Recognition as an Important First Step
Anne M. Andrews, M. J. Shuster, A. Vaish, and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Quantitative Measurements of Single-Molecule Dynamics: Intermolecular Potentials and Functional Properties
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Exploring and Controlling the Atomic-Scale World: Directing Chemical Reactions and Atomically Precise Structures
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Self- and Directed Assembly of Functional Nanoscale Structures
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the films. We employ some of these approaches in directed assembly to enable bioselective and biospecific binding. We develop hybrid strategies to create chemical patterns down to the single-molecule scale.

Exploring and Controlling the Atomic-Scale World: Directing Chemical Reactions and Atomically Precise Structures
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We measure these interactions and the electronic perturbations that underly them using scanning tunneling microscopy. In these and other measurements, we collect substantial data sets in order to generate distributions with the statistics of ensemble-averaging techniques, while still retaining all the single molecule and environmental information. This requires new automated tools for acquisition and analyses. We also use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film.

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Precise Measurements of Atomically Precise Materials
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Molecules that control position and conduction at the nanometer scale have great promise for future devices. Azobenzene molecules having two conformational isomers (trans- and cis-) are well known examples of optoelectronic switches. We study the reversible photo-isomerization of azobenzene functionalized molecules in precisely tailored nanoscale environments with the scanning tunneling microscopy (STM). Matrices are prepared to assemble isolated (0D), linear chains (1D) and islands (2D) of molecules. We report switch-OFF and switch-ON of single azobenzene functionalized molecules from “trans” to “cis” and vice-versa on photoillumination with ultraviolet (~365 nm) and visible (~440 nm) lights, respectively. This is the first direct observation of photo-switching realized by designing the molecular tether and the surrounding matrix in order to suppress surface quenching and steric constraints. We conclude, switching is a result of photo-isomerization, and not tip-induced or stochastic effects and different nanoscale assemblies affect the photo-switching efficiencies.

Structures and displacement of 2-adamantanethiol self-assembled monolayers on Au{111}
M. Kim, J. N. Hohman, and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have determined the structures of self-assembled monolayers (SAMs) of 2-adamantanethiol on Au{111} using scanning tunneling microscopy (STM). These SAMs of 2-adamantanethiol on Au{111} have different structures and rotational domains than 1-adamantanethiol SAMs. There are two dominant domain structures that show different labilities in the presence of dilute n-alkanethiol solutions. The alternating linear structure shows resistance to displacement by alkanethiols, while disordered regions exhibit rapid displacement. Stronger van der Waals interactions between 2-adamantanethiol molecules relative to 1-adamantanethiols result in a striped phase of long-chain alkanethiols after displacement. Co-adsorbed SAMs of 1-adamantanethiol and 2-adamantanethiol on Au{111} enable further control and selection of displacement.

Soft Nanolithography: Tuning Surface Chemistry and Dynamics
J. N. Hohman H. M. Saavedra, C. Srinivasan, E. I. Morin, T. J. Mullen and P. S. Weiss, Departments of Chemistry, Physics, and Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Microcontact printing (µCP) is one of the most important techniques in the area of chemical patterning, thus chemical library extension and capability enhancements are important. Ink concentration, ink molecular weight, and contact time all play roles in determining SAM quality and pattern fidelity. Higher-quality films tend to suffer from poor pattern integrity, due to diffusion of the ink molecules across the surface. Techniques to increase ink diversity, film quality, and pattern integrity have been developed, such as microdisplacement printing (µCP) and microcontact insertion printing (µCIP). To gain comprehensive understanding of how contact time influences both film quality and pattern integrity, we have investigated the printing of commonly used alkanethiol ink molecules on Au using µCP, and on a preformed, labile 1-adamantanethiolate SAM on Au for comparison to µDP. We have characterized the surfaces using lateral force microscopy (LFM), scanning electron microscopy (SEM), and infrared spectroscopy (IR).

Elucidating the origins, dynamics and mechanism of 1-adamantanethiolate monolayer displacement for advanced patterning
H. M. Saavedra, C. M. Barbu, V. H. Crespi, A. Dameron, T. J. Mullen and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Understanding the nature of 1-adamantanethiolate displacement not only aids in improving the quality and resolution of patterning techniques, such as microdisplacement printing, but also allows us to design new molecules with advantageous properties that can be exploited and thereby to increase the resolution and applicability of chemically patterned films. Therefore, we have investigated the solution-phase displacement kinetics of 1-adamantanethiolate self-assembled monolayers on Au{111} by n-dodecanethiol molecules using infrared spectroscopy, scanning tunneling microscopy, x-ray photoelectron spectroscopy and electrochemical desorption. The displacement reaction can be described by the fast insertion of n-dodecanethiolate at defects in the original 1-adamantanethiolate monolayer, which nucleates an island growth phase and is followed by eventual slow ordering of the n-dodecanethiolate domains into a denser and more crystalline form. Langmuir-based kinetics, which describe alkanethiol adsorption on bare Au{111}, fail to model this displacement reaction. Instead, a Johnson-Mehl-Avrami-Kolmogorov model of perimeter-dependent island growth yields good agreement with kinetic data obtained over a hundred-fold variation in n-dodecanethiol concentration.

Nanoscience Approaches to Chemical and Biological Warfare Defense
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Importance of Contacts in Molecular Electronics
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules. We have developed further spectroscopies and methods to study the buried interface and its dynamics. Consistent with the large perturbation of the substrate surface upon chemisorption, changes in bonding also likely rearrange substrate atoms. The ramifications of these changes will be discussed.

Self- and Directed Assembly of Functional Nanoscale Structures
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Self-Assembly and Control of Molecular Rotors
Tomohide Takami,^1,2 Tao Ye,² Paul S. Weiss,² Dennis P. Arnold,³ Ken-ichi Sugiura,⁴ Jianzhuang Jiang^5
1Visionarts
²Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA
³Queensland University of Technology
⁴Tokyo Metropolitan University
⁵Shandong University

Addressed assembly and arrangement of molecular components on surfaces through bottom-up methods are important steps in creating molecular-scale devices. Making such devices functional is possible by combining these with top-down methods to prepare electrodes and for signal input and output, e.g., driving and detecting the motion of a molecular rotor for “molecular phase memory” 1, as shown in the right figure. Recent synthesis and self-assembly strategies have resulted in increasingly sophisticated supramolecular structures2 and fabricated nano-structures3. Such structures result from balancing between surface-adsorbate and adsorbate-adsorbate interactions. While most studies have focused on controlling 2D structures, a wide range of novel properties, such as controlled rotary motions and the potential to address individual molecules, can be introduced into surface structures if additional complexity is incorporated in the surface normal direction. Interactions in the formation of such 3D structures are not restricted to components in the surface plane; interactions from elevated off the surface may play important roles as well. We have reported the observations of double-decker complexes of phthalocyanine (Pc), porphyrin (Por), and naphthalocyanine (Nc) with scanning tunneling microscopy (STM). 4 Both chemistry and manipulation of the monolayer film structures tuned their properties. We processed the films to slide (like a sliding block, shown in the upper left of the right figure), extract, and fill in single molecules, as shown in the series images in the lower column of the right figure. In this talk, the control of the assembly and arrangement of molecular rotors using bottom-up and top-down methods is discussed for the future of molecular machines.

1) Takami, T.; Sugiura, K.-i. U.S. Patent 6,762,397, July 13, 2004.
2) Kottas, G. S.; Clarke, L. I.; Horinek, D.; Michl, J. Chem. Rev. 2004, 105, 1281.
3) Smith, R. K.; Lewis, P. A.; Weiss, P. S. Prog. Surf. Sci. 2004, 75, 1.
4) Takami, T. et al., J. Phys. Chem. B 2006, 110, 1661; Ye, T. et al., J. Am. Chem. Soc. 2006, 128, 10984; Takami, T. et al., J. Chem. Phys. C, 2007, 111, 2077.

Neurochip project
Ashley Gibb, Department of Chemistry, The Pennsylvania State University, University Park, PA 16802-6300, USA

Neurochip project
Chemically Precise Nanostructures, Department of Chemistry, The Pennsylvania State University, University Park, PA 16802-6300, USA

Investigating the kinetics of vapor annealed self-assembled monolayers using STM
Chris Pochas, Department of Chemistry, The Pennsylvania State University, University Park, PA 16802-6300, USA

Bacterial Relay Race Using quorum sensing to control motility in E.coli
Lucien Weiss, Department of Chemistry, The Pennsylvania State University, University Park, PA 16802-6300, USA

Measurements and Control of Switching in Single and Assembled Molecules
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Constructivist Education at the Interdisciplinary Borders and Frontiers
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

An increasing challenge worldwide is in education in the most exciting interdisciplinary areas in which we do research and to which there are great influxes of students from surrounding disciplines. Among the difficulties are: the rapidly changing fields themselves, the diversity in the educational backgrounds of the students entering the fields, and the diversity of the faculty backgrounds. Because of the rapid evolution and the youth of these fields, there are typically few if any textbooks and any that do exist are rapidly outdated.

Based on experiences spanning the early undergraduate through the graduate level in classes in interdisciplinary science, biologically-inspired computation, molecular biotechnology, and synthetic biology, we have found that team-based constructivist approaches have unique advantages from both student and faculty perspectives. In building on students’ and instructors’ knowledge bases, dialogues are built up and connections are rapidly made between fields. This strategy also leads to constant restructuring based on the backgrounds of those involved. Importantly, knowledge and application of fundamental principles are reinforced. Lessons learned will be discussed in the context of developing general approaches to interdisciplinary education.

Additional barriers arise from administrative structures along the divisions of traditional disciplines. Issues and approaches related to involving the top people from diverse fields will also be discussed.

Hybrid Strategies in Nanolithography and Chemical Patterning
Charan Srinivasan, Mark Horn, Paul S. Weiss, Departments of Chemistry, Physics, and Engineering Science & Mechanics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Selecting and Driving Nanoscale Assembly in Monolayer Films through Tailored Intermolecular Interactions
T. J. Mullen, C. Srinivasan, M. J. Shuster, J. N. Hohman, M. W. Horn, A. M. Andrews and P. S. Weiss, Departments of Chemistry, Engineering Science & Mechanics, Physics, and Veterinary & Biomedical Science, The Pennsylvania State University, University Park, PA 16802-6300, USA

Active chemical surfaces that selectively capture and separate specific analytes from competitive environments are useful for detecting and isolating complex biological molecules as well as small molecules found in chemical weapons and toxic industrial waste. The development of self- and directed assembly strategies is key to the fabrication of molecularly precise structures for such applications. As the dimensions of patterned surface structures have decreased to the sub-100 nm scale, traditional lithographic techniques have not demonstrated the ability to fabricate reproducible structures over larger areas with molecular-scale organization. We have developed, utilized, and evaluated self- and directed nanoscale assembly strategies to fabricate, to register, and to functionalize chemical surface structures at the supramolecular 1-100 nm scale. We will highlight two hybrid soft-lithography strategies - microdisplacement printing and microcontact insertion printing - where monolayers with specifically tuned intermolecular interactions were engineered and the chemical and physical properties of the resulting patterned structures were characterized on both the ensemble and the molecular scales. Additionally, we will demonstrate that these chemical films can be functionalized with small-molecule probes that selectively capture large biomolecules while resisting nonspecific binding.

Dynamics of Molecular Switch Molecules Imaged by Alternating Current Scanning Tunneling Microscopy
A. M. Moore and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have studied oligo(phenylene-ethylene) (OPE) molecules as candidates for molecular electronic switches. We previously determined the switching mechanism to rely on hybridization changes between the substrate and molecule. Here, we have determined which molecules will be more or less active in our samples using a custom-built alternating current scanning tunneling microscope (ACSTM). The polarizabilities of the OPE molecules are observed using the ACSTM magnitude signal. The stability of the ACSTM magnitude correlates to the stability of the switches in our samples. From this, we can determine which molecules are more likely to exhibit motion and/or switching events and which molecules will remain stable in our images.

Local Chemical Measurements with the Scanning Tunneling Microscope
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We measure these interactions and the electronic perturbations that underly them using scanning tunneling microscopy. In these and other measurements, we collect substantial data sets in order to generate distributions with the statistics of ensemble-averaging techniques, while still retaining all the single-molecule and environmental information. This requires new automated tools for acquisition and analyses. We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules.

Understanding Molecular Exchange on Surfaces: Controlling and Elucidating the Mechanism of 1-Adamantathiolate Monolayer Displacement
H. M. Saavedra, T. J. Mullen, C. M. Barbu, A. A. Dameron, V. H. Crespi, and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We have investigated the solution-phase displacement kinetics of 1-adamantanethiolate self-assembled monolayers on Au{111} by n-dodecanethiol molecules using infrared spectroscopy, scanning tunneling microscopy, x-ray photoelectron spectroscopy and electrochemical desorption. The displacement reaction can be described by the fast insertion of n-dodecanethiolate at defects in the original 1-adamantanethiolate monolayer, which nucleates island growth and is followed by eventual slow ordering of the n-dodecanethiolate domains. Langmuir-based kinetics, which describe alkanethiolate adsorption on bare Au{111}, fail to describe this displacement reaction. Instead, a Johnson-Mehl-Avrami-Kolmogorov model of perimeter-dependent island growth yields good agreement with kinetic data obtained over a hundred-fold variation in n-dodecanethiol concentration. Analysis on a model-free basis suggests that displacement is a scale-free process within this concentration regime. The crucial role of the adsorbate lattice, along with the thermodynamic driving forces, rationalizes the rapid and complete displacement of 1-adamantanethiolate monolayers and explains why other monolayers reach kinetic traps that result in slow and incomplete displacement.

Quantitative Scanning Probe Measurements of Single Atoms, Molecules and Assemblies: Preserving and Understanding Heterogeneity
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Precise Nanogaps Using Self-Assembled Multilayers and Lithographic Resists
C. Srinivasan, M. E. Anderson, J. N. Hohman, P. S. Weiss, and M. W. Horn, Departments of Chemistry, Engineering Science & Mechanics, and Physics, The Pennsylvania State University, University Park, PA 16802, USA

How Can We Impact the Future with New Materials, New Methods, and New Measurements?
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University

Developing Atomic-Resolution Tools to Measure Spectral and Functional Properties
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University

Designing, Measuring and Controlling Molecular- and Supramolecular-Scale Properties for Molecular Devices
P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

We use molecular design, tailored syntheses, intermolecular interactions and selective chemistry to direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measurements of single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood and exploited at unprecedented scales. We look at how these interactions influence the chemistry, dynamics, structure, electronic function and other properties. Such interactions can be used to advantage to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. These nanostructures can be taken all the way down to atomic-scale precision or can be used at larger scales. We select and tailor molecules to choose the intermolecular interaction strengths and the structures formed within the film. We employ some of these approaches in directed assembly to enable bioselective and biospecific binding. We also selectively test hypothesized mechanisms for electronic switching by varying molecular design, chemical environment, and measurement conditions to enable or to disable functions and control of these molecules with predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule measurements in order to develop sufficiently significant statistical distributions, comparable to those found in ensemble-averaging measurements, while retaining the heterogeneity of the measurements. We quantitatively compare the conductances of molecule-substrate junctions. We demonstrate the importance of these junctions in conductance switching of single molecules.

We now apply these strategies to photo-driven, electrochemically-driven, and chemically-driven motion in single molecules and assemblies. This enables us to address how concerted nano-scale motions can be used to drive motion at larger scales. The atomic-scale details provide surprising and useful insight into limitations and opportunities of cooperative motion.

Symposium FF: Synthesis and Surface Engineering of Three-Dimensional Nanostructures

Hybrid Approaches to Nanolithography and Chemical Patterning
C. Srinivasan, J. N. Hohman, M. E. Anderson, P. Zhang, T. J. Mullen, A. M. Andrews, M. W. Horn, P. S. Weiss
Departments of Chemistry, Physics, and Engineering Science & Mechanics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Despite the impressive pace of innovations in photolithography, this technology faces fundamental physical and economic limitations for patterning sub-30-nm features.  We have combined photolithography, a top-down approach, synergistically with bottom-up chemical self-assembly to fabricate nanometer-scale features in a low-cost, scalable process – molecular-ruler nanolithography.^1,2  Here, we describe the strategies that have been developed to integrate this technique with CMOS-compatible materials and processes,³ patterns registered nanometer-scale features on quartz for use as the mold in nanoimprint lithography,⁴ with double the spatial frequency of features created by conventional lithographic techniques.⁵  We also use this methodology to fabricate connected device structures for ultranarrow channel length organic thin-film transistors and aligned metallic and semiconducting nanowires.

One of the limitations of photolithography is its inability to pattern chemical functionality on surfaces; chemically functionalized surfaces have applications ranging from biospecific recognition to molecular electronics.⁶  To address this issue, we developed lithography-assisted chemical patterning.  This technique utilizes a robust lithographic resist (LOR) that is capable of withstanding self-assembly deposition conditions to create high-quality chemical patterns.  The ability to pattern chemical functionalities without intercalation and with registered, parallel processing are some of its unique advantages.^7,8

1. A. Hatzor and P. S. Weiss, Science 2001, 291, 1019.
2. M. E. Anderson, L. P. Tan, M. Mihok, H. Tanaka, M. W. Horn, G. S. McCarty, P. S. Weiss, Adv. Mater. 2006, 18, 1020.
3. C. Srinivasan, M. E. Anderson, E. M. Carter, J. N. Hohman, S. S. N. Bharathwaja, S. Trolier-Mckinstry, P. S. Weiss, M. W. Horn, J. Vac. Sci. Technol. B 2006, 24, 3200.
4. C. Srinivasan, J. N. Hohman, M. E. Anderson, P. S. Weiss, M. W. Horn (submitted for publication).
5. C. Srinivasan, J. N. Hohman, M. E. Anderson, P. Zhang, P. S. Weiss, M. W. Horn, Proc. SPIE 2007, 6517, 65171I.
6. Y. Xia and G. M. Whitesides, Angew. Chem., Int. Ed. 1998, 37, 551.
7. M. E. Anderson, C. Srinivasan, J. N. Hohman, E. M. Carter, M. W. Horn, P. S. Weiss, Adv. Mater. 2006, 18, 3258.
8. C. Srinivasan, T. J. Mullen, J. N. Hohman, M. E. Anderson, A. A. Dameron, A. M. Andrews, E. C. Dickey, M. W. Horn, P. S. Weiss, ACS Nano 2007, 1, 191.

Selecting and Driving Nanoscale Assembly in Monolayer Films through Tailored Intermolecular Interactions
T. J. Mullen and P. S. Weiss, Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA

Active chemical surfaces that selectively capture and separate specific analytes from competitive environments are useful for detecting and isolating complex biological molecules as well as small molecules found in chemical weapons and toxic industrial waste. The development of self- and directed assembly strategies is key to the fabrication of molecularly precise structures for such applications. As the dimensions of patterned surface structures have decreased to the sub-100 nm scale, traditional lithographic techniques have not demonstrated the ability to fabricate reproducible structures over larger areas with molecular-scale organization. We have developed, utilized, and evaluated self- and directed nanoscale assembly strategies to fabricate, to register, and to functionalize chemical surface structures at the supramolecular 1-100 nm scale. We will highlight two hybrid soft-lithography strategies - microdisplacement printing and microcontact insertion printing - where monolayers with specifically tuned intermolecular interactions were engineered and the chemical and physical properties of the resulting patterned structures were characterized on both the ensemble and the molecular scales. Additionally, we will demonstrate that these chemical films can be functionalized with small-molecule probes that selectively capture large biomolecules while resisting nonspecific binding.

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7 February 2016
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