Single Particle Characterization On Gold/Titania Nanostructures For Water Splitting

Localized surface plasmon resonance(LSPR,collective charge density oscillations that are confined to noble metal nanostructures)in noble metal nanostructures are of great significance in optics and photonics fields.Hot electrons generated by the LSPR can transfer over the Schottky barrier between the metal and the semiconductor,generating a photocurrent.At present,researches on photoelectrochemical reactions(i.e.water splitting)are mainly based on devices containing a large number of nanostructures with different shapes and sizes.The measured photocurrent is the collective contribution of these nanostructures.Herein,we developed a single-particle characterization method and explored the hot electron response of individual gold nanoparticles(AuNPs)with specific shapes and sizes in the photoelectrochemical reaction.The main contents of this thesis are as the following:1.Study on single-particle characterization method for photoelectrochemical reaction(?)Fabrication of photoelectrochemical device for single-particle characterization:The AuNPs were deposited separately on a titanium oxide(TiO2)film prepared by the sol-gel method to form Au/TiO2 nanostructures.(?)Experimental setup for the mapping of photoelectrochemical response:We construct an experimental setup by Lab VIEW programming for the mapping of photoelectrochemical response.(?)Characterization of photoelectrochemical response of single AuNP:The photocurrent increases with the increase of bias voltage,laser power,and particle size,but it is almost not affected by the incident angle of the excitation light.The photocurrent is also related to the interface structure of Au/TiO2.AuNPs that are half-embedded in the film exhibit a nearly doubled photocurrent response when compared with those on the top of the TiO2 film.Negative photocurrent is found in full-embedded cases.2.Analysis of incident photon-to-current conversion efficiency(IPCE)and study on the mechanism of hot electron generationThe IPCE is found to be inversely proportional to the size of AuNPs.Specifically,finite-difference time-domain(FDTD)method is used to calculate the efficiency of the absorption of the incident photons;the efficiency of hot electron generation can be obtained by calculation of surface plasmon damping;we also simulate the temperature of AuNPs by finite element method(FEM,COMSOL Multiphysics)to obtain the the reaction efficiency.Finally,the dependence of conversion efficiency on the size of AuNPs is analyzed and the mechanism of the hot electron generation process is revealed through the comparison between experiment and calculation.The studies in this paper provide a characterization method of photoelectrochemical reaction at the single-particle level,which is beneficial for further studies on the reaction mechanisms of Au/TiO2 water splitting systems.