Research On Plasmonic Catalysis Of Gold Nanoparticles And Their Composite Structures

In light-driven chemical reactions,plasmonic nanostructures have extensive and good tunable optical properties,and the surfaces of nanoparticles have catalytically active sites,which provides opportunities for solar-driven photochemical reactions to proceed.Under the excitation of incident light,noble metal nanoparticles will collectively oscillate,which is called Surface Plasmon Resonance(SPR),which leads to the greatly enhanced local electromagnetic field.Surface plasmons then generate non-radiative decay hot electrons,which can disperse into the excited state of the absorbing molecules and trigger chemical reactions by reducing the activation energy.At present,surface plasmon nanostructures can rapidly improve the reaction rate by using the excitation of resonance light to generate hot electrons to participate in the reaction,thus becoming a new catalytic method in driving catalytic reactions.However,the extremely low production rate and utilization efficiency of hot electrons are the bottleneck restricting the development of catalysis.How to improve the utilization efficiency of hot electrons produced by surface plasmon resonance has become an urgent problem to be solved.In order to perform in-situ monitoring of photochemical reactions,Surface-Enhanced Raman Spectroscopy(SERS)technology has been widely used to study the surface plasmon-catalyzed reaction because it can provide molecular fingerprint informations.Therefore,we used SERS technology to carry out in-situ research on the surface plasmon response of nanoparticles.In this paper,gold nanoparticle is used as the research object,and gold nanoparticle is used as the core to synthesize core-shell nanoparticle structures with different heterojunctions.The samples were characterized and tested by means of Transmission Electron Microscope(TEM),Scanning Electron Microscope(SEM),Ultraviolet-Visible Spectroscopy(UV-Vis).The Finite-Difference Time-Domain(FDTD)was used to simulate the electromagnetic field distribution between particles.The effects of the formation of chemical bonds between plasmonic metals and molecules on improving the utilization efficiency of hot electrons were explored by SERS technology.In addition,the Au@Cd S interface catalytic reaction of metal-semiconductor nanomaterials was discussed.The main research contents are as follows:(1)25 nm and 45 nm Au nanoparticles were prepared by sodium citrate reduction method,120 nm Au nanoparticles were prepared by seed growth method,and the electromagnetic field distribution between particles was simulated by FDTD calculation.At the same time,Au@Si O2 and Au@Cd S core-shell nanoparticles with different shell thicknesses were prepared using gold nanoparticles with different diameters as cores,and their morphology and optical properties were characterized and tested.(2)We selected 120 nm Au nanoparticles and p-nitrothiophenol(p NTP)molecules as the research objects,and studied the ways in which the hot electrons utilization efficiency is higher through different adsorption methods between them.The entire catalytic process is monitored by SERS technology.The selected SERS reinforcement materials are Au and Au@Si O2 nanoparticles.According to the different electron transfer modes,three experiments were designed: physical adsorption of Au and p NTP molecules,chemical adsorption of Au and p NTP molecules,and physical adsorption of Au@Si O2 and p NTP molecules.Different variations of Raman spectra were used to judge the utilization efficiency.The experimental results not only verified the source of hot electrons,but also obtained the highest utilization efficiency of hot electrons when Au nanoparticles and p NTP molecules formed chemical bonds,thus providing an important basis for the selection of photocatalytic mode.(3)We used SERS technology to study the photocatalytic reaction of Au@Cd S nanoparticles with SPR effect and photocatalytic activity.Au@Cd S nanoparticles with different shell thickness were prepared.We used Au@Cd S core-shell nanoparticles with a shell thickness of 4 nm as the photocatalytic material for p NTP.The hot electrons transfer path in Au@Cd S was tracked by the Raman spectrum changes of the p NTP molecules to investigate the catalytic mechanism of the Au core interface with the Cd S shell.At the same time,we found that Au@Cd S also showed strong catalytic activity in photocatalytic degradation of rhodamine(R6G).It was indicated that SPR metal-semiconductor nanocomposite structure was a promising photocatalytic and in situ SERS research material.