Polyelectrolyte becomes more and more popular in electrocatalysis.The understanding of electrode/polyelectrolyte interfaces at the molecular level is important for guiding further the polyelectrolyte-based electrocata...Polyelectrolyte becomes more and more popular in electrocatalysis.The understanding of electrode/polyelectrolyte interfaces at the molecular level is important for guiding further the polyelectrolyte-based electrocatalysis.Herein,we demonstrate an in-situ surface-enhanced Raman spectroscopic method by using a three-electrode spectroelectrochemical cell towards characterizing the electrode/polyelectrolyte interfaces.The Ag/AgCl and Ag/Ag_(2)O electrodes are used as the reference electrode in the acidic and the alkaline systems,respectively.The working electrode is made of a transparent carbon thin film which loads the electrocatalysts.The applications of this method are demonstrated through the in-situ characterizations of the p-methylthiophenol adsorbed on the Au and Pt and the electrochemical oxidation of Au on polyelectrolyte membranes.The potential-dependent spectral features of these two systems show that this method is a powerful tool for investigating the electrode/polyelectrolyte interfaces in electrocatalysis.展开更多
Nanoscale noble metals can exhibit excellent photochemical and photophysical properties, due to surface plasmon resonance(SPR) from specifically collective electronic excitations on these metal surfaces. The SPR effec...Nanoscale noble metals can exhibit excellent photochemical and photophysical properties, due to surface plasmon resonance(SPR) from specifically collective electronic excitations on these metal surfaces. The SPR effect triggers many new surface processes, including radiation and radiationless relaxations. As for the radiation process, the SPR effect causes the significant focus of light and enormous enhancement of the local surface optical electric field, as observed in surface-enhanced Raman spectroscopy(SERS) with very high detection sensitivity(to the single-molecule level). SERS is used to identify surface species and characterize molecular structures and chemical reactions. For the radiationless process, the SPR effect can generate hot carriers, such as hot electrons and hot holes, which can induce and enhance surface chemical reactions. Here, we review our recent work and related literature on surface catalytic-coupling reactions of aromatic amines and aromatic nitro compounds on nanostructured noble metal surfaces. Such reactions are a type of novel surface plasmon-enhanced chemical reaction. They could be simultaneously characterized by SERS when the SERS signals are assigned. By combining the density functional theory(DFT) calculations and SERS experimental spectra, our results indicate the possible pathways of the surface plasmonenhanced photochemical reactions on nanostructures of noble metals. To construct a stable and sustainable system in the conversion process of the light energy to the chemical energy on nanoscale metal surfaces, it is necessary to simultaneously consider the hot electrons and the hot holes as a whole chemical reaction system.展开更多
This work reports the real-time observation of the interlayer lattice vibrations in bilayer and few-layer PtSe_2 by means of the coherent phonon method. The layer-breathing mode and standing wave mode of the interlaye...This work reports the real-time observation of the interlayer lattice vibrations in bilayer and few-layer PtSe_2 by means of the coherent phonon method. The layer-breathing mode and standing wave mode of the interlayer vibrations are found to coexist in such a kind of group-10 transition metal dichalcogenides(TMDCs). The interlayer breathing force constant standing for perpendicular coupling(per effective atom) is derived as 7.5 N/m,2.5 times larger than that of graphene. The interlayer shearing force constant is comparable to the interlayer breathing force constant, which indicates that PtSe2 has nearly isotropic interlayer coupling. The low-frequency Raman spectroscopy elucidates the polarization behavior of the layer-breathing mode that is assigned to have A1 g symmetry. The standing wave mode shows redshift with the increasing number of layers, which successfully determines the out-of-plane sound velocity of PtSe2 experimentally. Our results manifest that the coherent phonon method is a good tool to uncover the interlayer lattice vibrations, beyond the conventional Raman spectroscopy limit. The strong interlayer interaction in group-10 TMDCs reveals their promising potential in high-frequency(~terahertz) micro-mechanical resonators.展开更多
The roles of temperature change in surface-enhanced Raman scattering(SERS)hotspots are important for understanding the plasmon-mediated selective oxidation of p-aminothiophenol in a SERS measurement. Here, we demonstr...The roles of temperature change in surface-enhanced Raman scattering(SERS)hotspots are important for understanding the plasmon-mediated selective oxidation of p-aminothiophenol in a SERS measurement. Here, we demonstrate that the temperature change in hotspots seriously influences the conversion of p-aminothiophenol on Au by employing variable-temperature SERS measurements. The conversion steadily and irreversibly increased when the temperature increased from 100 to 360 K. But the conversion decreased above 360 K, because this conversion was exothermic. This temperature-dependence conversion suggests that the temperature change in hotspots originated from the photothermal effect should be coupled to the hot-electron effect in promoting the selective oxidation of p-aminothiophenol.展开更多
文摘Polyelectrolyte becomes more and more popular in electrocatalysis.The understanding of electrode/polyelectrolyte interfaces at the molecular level is important for guiding further the polyelectrolyte-based electrocatalysis.Herein,we demonstrate an in-situ surface-enhanced Raman spectroscopic method by using a three-electrode spectroelectrochemical cell towards characterizing the electrode/polyelectrolyte interfaces.The Ag/AgCl and Ag/Ag_(2)O electrodes are used as the reference electrode in the acidic and the alkaline systems,respectively.The working electrode is made of a transparent carbon thin film which loads the electrocatalysts.The applications of this method are demonstrated through the in-situ characterizations of the p-methylthiophenol adsorbed on the Au and Pt and the electrochemical oxidation of Au on polyelectrolyte membranes.The potential-dependent spectral features of these two systems show that this method is a powerful tool for investigating the electrode/polyelectrolyte interfaces in electrocatalysis.
基金financially supported by the National Natural Science Foundation of China(21321062,21373172)
文摘Nanoscale noble metals can exhibit excellent photochemical and photophysical properties, due to surface plasmon resonance(SPR) from specifically collective electronic excitations on these metal surfaces. The SPR effect triggers many new surface processes, including radiation and radiationless relaxations. As for the radiation process, the SPR effect causes the significant focus of light and enormous enhancement of the local surface optical electric field, as observed in surface-enhanced Raman spectroscopy(SERS) with very high detection sensitivity(to the single-molecule level). SERS is used to identify surface species and characterize molecular structures and chemical reactions. For the radiationless process, the SPR effect can generate hot carriers, such as hot electrons and hot holes, which can induce and enhance surface chemical reactions. Here, we review our recent work and related literature on surface catalytic-coupling reactions of aromatic amines and aromatic nitro compounds on nanostructured noble metal surfaces. Such reactions are a type of novel surface plasmon-enhanced chemical reaction. They could be simultaneously characterized by SERS when the SERS signals are assigned. By combining the density functional theory(DFT) calculations and SERS experimental spectra, our results indicate the possible pathways of the surface plasmonenhanced photochemical reactions on nanostructures of noble metals. To construct a stable and sustainable system in the conversion process of the light energy to the chemical energy on nanoscale metal surfaces, it is necessary to simultaneously consider the hot electrons and the hot holes as a whole chemical reaction system.
基金National Natural Science Foundation of China(11874370,61675217)Strategic Priority Research Program of Chinese Academy of Sciences(XDB16030700)+5 种基金Key Research Program of Frontier Science of Chinese Academy of Sciences(QYZDB-SSW-JSC041)Program of Shanghai Academic Research Leader(17XD1403900)Natural Science Foundation of Shanghai(18ZR1444700)Shanghai Rising-Star Program(A type 19QA1410000)Youth Innovation Promotion Association of the Chinese Academy of SciencesHigh-End Foreign Expert Fellowship of the Ministry of Science and Technology of the P.R.China(G20190161002)
文摘This work reports the real-time observation of the interlayer lattice vibrations in bilayer and few-layer PtSe_2 by means of the coherent phonon method. The layer-breathing mode and standing wave mode of the interlayer vibrations are found to coexist in such a kind of group-10 transition metal dichalcogenides(TMDCs). The interlayer breathing force constant standing for perpendicular coupling(per effective atom) is derived as 7.5 N/m,2.5 times larger than that of graphene. The interlayer shearing force constant is comparable to the interlayer breathing force constant, which indicates that PtSe2 has nearly isotropic interlayer coupling. The low-frequency Raman spectroscopy elucidates the polarization behavior of the layer-breathing mode that is assigned to have A1 g symmetry. The standing wave mode shows redshift with the increasing number of layers, which successfully determines the out-of-plane sound velocity of PtSe2 experimentally. Our results manifest that the coherent phonon method is a good tool to uncover the interlayer lattice vibrations, beyond the conventional Raman spectroscopy limit. The strong interlayer interaction in group-10 TMDCs reveals their promising potential in high-frequency(~terahertz) micro-mechanical resonators.
基金financially supported by the National Natural Science Foundation of China (Nos.21872094,21991152,and21991150)a ShanghaiTech University Start-Up grant。
文摘The roles of temperature change in surface-enhanced Raman scattering(SERS)hotspots are important for understanding the plasmon-mediated selective oxidation of p-aminothiophenol in a SERS measurement. Here, we demonstrate that the temperature change in hotspots seriously influences the conversion of p-aminothiophenol on Au by employing variable-temperature SERS measurements. The conversion steadily and irreversibly increased when the temperature increased from 100 to 360 K. But the conversion decreased above 360 K, because this conversion was exothermic. This temperature-dependence conversion suggests that the temperature change in hotspots originated from the photothermal effect should be coupled to the hot-electron effect in promoting the selective oxidation of p-aminothiophenol.
