| Surface-enhanced Raman spectroscopy is playing a very important role to the study of the structure of adsorbed molecules to in the metal electrode, as well as, it is also an important means for the in situ electrochemical reactions (including catalytic reaction) mechanism.Combining the surface chemistry and enhanced Raman spectroscopy meets the need of promoting the scientific development of spectroelectrochemistry! Thus the new surface plasma chemistry science is also becoming a hot branch of surface catalytic chemistry on the basis of that. As surface electron can strongly absorb electromagnetic energy via local surface plasmon resonance (LSPR) when the light radiates the metal nanostructures. So that the excited electrons of the metallic nanostructures can be changed to "hot electrons". This "hot electrons" can be transferred to molecules for overcoming reaction barriers in plasmon-driven chemical reaction. Furthermore, hot electrons generated from plasmon decay can also provide the electrons that the chemical reactions would capture and demand. Because this is a new field of study, so there are a lot of important scientific issues need to be resolved. For example, in a three-electrode electrochemical reaction system, can the hot electrons generated on the rough gold, silver electrode effectively survive in the aqueous environment? Can the density of states (DOS) of hot electrons be manipulated by external acid or alkaline aqueous environment? Is it possible by using sensitive spectroscopy (SERS) to detect these surface reactions? These scientific problems to be solved is the main key issues and contents of this thesis research.If the DOS of hot electrons can be effectively manipulated by the different aqueous environment, then the plasmon-driven chemical reactions can be well controlled. Furthermore, the plasmon-driven chemical reaction at low-cost and large scale applications in an easy way is our goal. All of above are very important issues for the field of plasmon-driven chemistry and have great potential applications.In this paper, we reported the in situ SERS spectra of the4-nitrothioanisole with the changed potentials. We demonstrated and explained the adsorption behavior of molecules, the mechanism of interaction and the catalytic mechanism of the molecule. Our research shows that, under the "hot electrons" inducing, the4-nitrothioanisole molecule is catlyied to dimercapto-azobenzene by applied different potentials, different light intensity and PH values. We also describes the effect of the hot electrons in the catalytic process, meanwhile this research may provide the basis for the theory of SERS enhancement mechanism, which would promote the study of electrochemical surface-enhanced Raman scattering system.It has been generally accepted that the enormous enhancement in SERS occurs from two kinds of mechanisms. One is called electromagnetic (EM). The other is chemical (CHEM) enhancement the former is a major enhancement. However, generally speaking, under most circumstances CHEM and EM mechanism will contribute to SERS enhancement together. Although rather minor contribution from the CHEM mechanism of the metal-adsorbate system was observed, it was often ignored due to its complexity in the electronic transitions at the surface which was very difficult to visualize. So, the understanding of the CT process is still very limited. In this paper, we studied the SERS spectroscopy of pyrimidine molecue and utilized the time-dependent density functional theory (TD-DFT) method to reveal visually CT from metal to molecule, we also revealed the chemically enhanced mechanism of the charge transfer for SERS. |
PDF Full Text Request