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Kinetic and Mechanistic Investigation of the Photocatalyzed Surface Reduction of 4-Nitrothiophenol Observed on a Silver Plasmonic Film via Surface-Enhanced Raman Scattering
摘要： Hot electrons generated by photo-induced plasmon decay from plasmonic metal surface can reduce 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP). Comparing to the reduction with a reducing agent such as sodium borohydride, Surface-Enhanced Raman scattering (SERS) measurements were performed here to elucidate the complex molecular mechanism of the reduction in presence of halide ions and hydrogen ions. The SERS measurements were performed using a simply prepared silver plasmonic film (AgPF), which enables monitoring of the reaction in different conditions at a solid-liquid surface, and eliminates the need for use of a reducing agent. As the concentration of H+ and Cl- could controlled, the observation of the reaction under a systematic set of condition was possible. Based on the kinetic traces of the intermediates, a reaction mechanism for the 4-NTP to 4-ATP reduction is suggested. Rate constants for the individual reactions are presented that fit the measured kinetic traces, and the role of hydrogen in each reaction step is characterized. This work provides clarification on the molecular transformation directly using protons as hydrogen source and demonstrates an effective method of applying a simple and low-cost silver surface catalyst for SERS studies. Moreover, the monitoring of Cl--concentration-dependent spectra gained insight into the hot-electron conversion process during the photoreduction and strongly support the formation of AgCl for activation of H+.
关键词： in-situ SERS spectra,kinetic rate constants,reaction mechanism,time-resolved measurements,selective surface photocatalytic reaction
更新于2025-09-23 15:19:57
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Time-resolved measurements of two-color laser light emitted from GaAs/AlGaAs-coupled multilayer cavity
摘要： We measured the two-color laser oscillation from a GaAs/AlGaAs-coupled multilayer cavity at 18 °C–42 °C using current injection. We confirmed simultaneous lasing by detecting the sum frequency generation signal generated by the two-color laser light, and performed time-resolved measurement using a streak camera with a spectrometer. From the observed time transient of the spectra at various temperatures, it is clarified that the temperature change of the device, induced by current injection, modulates the effective cavity length. Therefore, the temperature control of the device is a key factor in stable two-color lasing and THz wave generation.
关键词： time-resolved measurements,sum frequency generation,THz wave generation,GaAs/AlGaAs-coupled multilayer cavity,two-color laser
更新于2025-09-19 17:13:59
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Implementation of data-cube pumpa??probe KPFM on organic solar cells
摘要： An implementation of pump–probe Kelvin probe force microscopy (pp-KPFM) is reported that enables recording the time-resolved surface potential in single-point mode or over a 2D grid. The spectroscopic data are acquired in open z-loop configuration, which simplifies the pp-KPFM operation. The validity of the implementation is probed by measurements using electrical pumping. The dynamical photoresponse of a bulk heterojunction solar cell based on PTB7 and PC71BM is subsequently investigated by recording point-spectroscopy curves as a function of the optical power at the cathode and by mapping 2D time-resolved images of the surface photovoltage of the bare organic active layer.
关键词： Kelvin probe force microscopy (KPFM),time-resolved measurements,bulk heterojunctions,organic photovoltaics,pump–probe configuration,photocarrier dynamics
更新于2025-09-16 10:30:52