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Using a Pt/Si catalytic nanodiode, we externally control the rate of CO oxidation on a Pt nanofilm. The catalytic reaction can be turned on and off by alternating between bias states of the device. Additionally, the reaction rate is sensitive to photocurrent induced by visible light. The effects of both bias and light show that negative charge on the Pt increases catalytic activity, while positive charge on the Pt decreases catalytic activity for CO oxidation. 相似文献
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Giovanetti LJ Ramallo-López JM Foxe M Jones LC Koebel MM Somorjai GA Craievich AF Salmeron MB Requejo FG 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(3):468-473
Polyvinylpyrollidone (PVP)-capped platinum nanoparticles (NPs) are found to change shape from spherical to flat when deposited on mesoporous silica substrates (SBA-15). Transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and extended X-ray absorption fine structure (EXAFS) analyses are used in these studies. The SAXS results indicate that, after deposition, the 2 nm NPs have an average gyration radius 22% larger than in solution, while the EXAFS measurements indicate a decrease in first neighbor co-ordination number from 9.3 to 7.4. The deformation of these small capped NPs is attributed to interactions with the surface of the SBA-15 support, as evidenced by X-ray absorption near-edge structure (XANES). 相似文献
65.
Kaitlin M. Bratlie Yimin Li Ragnar Larsson Gabor A. Somorjai 《Catalysis Letters》2008,121(3-4):173-178
Kinetic measurements at low temperatures (310–360 K) using gas chromatography (GC) for benzene hydrogenation on Pt(100) and
Pt(111) single crystal surfaces have been carried out at Torr pressures. These kinetic measurements demonstrated a linear
compensation effect for the production of cyclohexane. A detailed application of the model of selective energy transfer to
the experimentally obtained results yields the vibrational frequency of the adsorbate leading to reaction. This frequency
is attributed to ring distortion modes. The vibrational frequency of the heat bath, or catalyst, is ascribed to a Pt-H mode.
An approximate heat of adsorption of the reacting molecule is also calculated from the model. 相似文献
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Yeo CT Ungi T U-Thainual P Lasso A McGraw RC Fichtinger G 《IEEE transactions on bio-medical engineering》2011,58(7):2031-2037
The purpose of this study was to determine if augmented reality image overlay and laser guidance systems can assist medical trainees in learning the correct placement of a needle for percutaneous facet joint injection. The Perk Station training suite was used to conduct and record the needle insertion procedures. A total of 40 volunteers were randomized into two groups of 20. 1) The Overlay group received a training session that consisted of four insertions with image and laser guidance, followed by two insertions with laser overlay only. 2) The Control group received a training session of six classical freehand insertions. Both groups then conducted two freehand insertions. The movement of the needle was tracked during the series of insertions. The final insertion procedure was assessed to determine if there was a benefit to the overlay method compared to the freehand insertions. The Overlay group had a better success rate (83.3% versus 68.4%, p=0.002), and potential for less tissue damage as measured by the amount of needle movement inside the phantom (3077.6 mm(2) versus 5607.9 mm(2) , p =0.01). These results suggest that an augmented reality overlay guidance system can assist medical trainees in acquiring technical competence in a percutaneous needle insertion procedure. 相似文献
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Catalysts are essential for the generation of energy carriers like hydrocarbon fuels, hydrogen, and electrical current. The performance of catalysts can be related to their nanostructure (i.e., size and shape) and composition. To rationally design catalysts by tuning these properties, they should be measured in a meaningful way using surface-sensitive spectroscopic tools under reaction conditions. In this perspective, we provide case histories of recently published research aimed at understanding these properties using a spectroscopic strategy under reaction conditions. We limit this perspective to studies whose main focus was to understand how the nanostructure and composition impact the active phase and/or efficiency of catalysts for the generation and conversion of energy carriers. We discuss studies of a Pd/Ga2O3 catalyst for the generation of hydrogen fuel from methanol and water, a PtMo catalyst for the generation of hydrogen fuel from biomass and water, Pt/Rh catalysts for the conversion of hydrogen into electrical current, a CeO x catalyst for the conversion of hydrogen into electrical current, and Fe and Co/CoPt catalysts for the generation of hydrocarbon fuel from carbon monoxide and hydrogen. Each study emphasizes how the use of spectroscopic tools under reactive conditions is beneficial for making rational decisions for improving catalysts. The studies demonstrate how different synthesis methods dictate the nanostructure and distribution of alloy components in the catalyst, certain pretreatment conditions create the active surface phase, while reactions and post-treatments can destroy it, and the nanostructure and composition change the electronic structure and alter the selectivity and activity. 相似文献
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ABSTRACT Modulated operation of the recently described method of laser diode intracavity absorption spectrometry is discussed. A simple driver circuit which can be used for cw or modulated operation of laser diodes is described. Development of a modulated near infrared laser diode intracavity spectrophotometer for absorption measurements is also provided. This modulated operation mode was compared to cw mode as to sensitivity, noise, ease of operation and detection limit. This modulated driver was implemented using an inexpensive 3 mW 750 nm laser diode and an IR3C02A driver circuit. Advantages of modulated laser diodes in spectroscopic applications are also presented. 相似文献