61 research outputs found
Mechanistic investigations of nanometer-scale lithography at liquid-covered graphite surfaces
Pulse-induced nanometer-scale lithography has been performed on graphite surfaces that were in contact with pure water or other organic liquids. Very reproducible control over the pit diameter was observed in aqueous solutions, and a well-defined voltage threshold (4.0±0.2 V) was also apparent. Near the threshold voltage, 7 Å diameter×2 Å high protrusions were formed, while larger initial pulse voltages resulted in pits of diameter>~20 Å
Atomic resolution imaging of electrode surfaces in solutions containing reversible redox species
Procedures are described for insulating metal scanning tunneling microscope (STM) tips with either glass or polymer coatings. In solutions containing 0.10 M of a reversible redox couple, Fe(CN) - 3/-46 , the faradaic limiting current to polymer coated tips was 200–500 pA and that for glass coated tips was <10 pA. For polymer insulated tips, steady-state currents of 10–100 pA were observed at tip-sample displacements less than 0.3 µm. The suppression of faradaic current achieved by these coating procedures enabled the collection of the first atomic resolution STM images of highly ordered pyrolytic graphite electrodes in contact with redox-active electrolytes. Preliminary data for the in situ electrochemical characterization of these tips are also discussed
Design of a scanning tunneling microscope for electrochemical applications
A design for a scanning tunneling microscope that is well suited for electrochemical investigations is presented. The construction of the microscope ensures that only the tunneling tip and the sample participate in electrochemical reactions. The design also allows rapid replacement of the tip or sample, and enables facile introduction of auxiliary electrodes for use in electrochemical experiments. The microscope utilizes stepper motor driven approach mechanics in order to achieve fully remote operation and to allow reproducible coarse control of tip/sample spacings for electrochemical experiments. Highly ordered pyrolytic graphite images at atomic resolution in air and aqueous solutions can be obtained with this microscope
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Carbon Nanotube Materials for Substrate Enhanced Control of Catalytic Activity
Carbon SWNTs are attractive materials for supporting electrocatalysts. The properties of SWNTs are highly tunable and controlled by the nanotube's circumferential periodicity and their surface chemistry. These unique characteristics suggest that architectures constructed from these types of carbon support materials would exhibit interesting and useful properties. Here, we expect that the structure of the carbon nanotube support will play a major role in stabilizing metal electrocatalysts under extreme operating conditions and suppress both catalyst and support degradation. Furthermore, the chemical modification of the carbon nanotube surfaces can be expected to alter the interface between the catalyst and support, thus, enhancing the activity and utilization of the electrocatalysts. We plan to incorporate discrete reaction sites into the carbon nanotube lattice to create intimate electrical contacts with the catalyst particles to increase the metal catalyst activity and utilization. The work involves materials synthesis, design of electrode architectures on the nanoscale, control of the electronic, ionic, and mass fluxes, and use of advanced optical spectroscopy techniques
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Optimizing Carbon Nanotube Contacts for Use in Organic Photovoltaics: Preprint
This report describes research on optimizing carbon nanotube networks for use as transparent electrical contacts (TCs) in organic photovoltaics (OPV)
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