Study On Adsorption Of Self - Assembled Monolayers And Blue Copper Proteins By SERS Spectroscopy

Surface-enhanccd Raman Scattering (SERS) spectroscopy has become animportant means of Surface analysis, is mainly used to obtain information on themolecular adsorption interface structure. Density functional theory (DFT) is a kind ofresearch system of electronic structure of quantum mechanics method, the system canbe used to describe the chemical structure, properties and energy, and its computationcost is low. DFT has gradually be applied to the surface enhanced Ramanspectroscopy.The system of biological molecular monolayer film in the current research fieldssuch as chemical modified electrodes and electrochemical zhongzheng is becomingmore and more attention by the people, has a good application prospect. Azure proteinis a kind of typical mononuclear blue copper protein, play an important role in theorganism (such as REDOX and electron transfer). The azure protein active center iscopper ifve ligand, including histidine, cysteine and methionine and glycinc. Researchreports about azure protein used in SKRS spectra is few, this paper selected the azureprotein and its two activity centers of histidine, cysteine as a research object used inSERS spectra method for the analysis. The research content mainly divided into thefollowing three parts:(1) Cysteine and cysteamine were used for the effective coupling ofself-assembled molecules betweengold nanoparticles and gold base. Two systemscompared for the two kinds of particle size of gold nanoparticles respectively, ifndingSERS effect of50nm gold nanoparticles with coupling structure was better than30nm gold nanoparticles with coupling structure. The coupling structures were formedthrough Au-S and-NH3"1" and between the gold nanoparticles and gold base. Throughelectrochemical SERS spectra analysis of the two kinds of coupling system, findingthat two molecules of coupling structure had both clcctromagnetic enhancement andchemical enhancement.(2) Based on the theoretical calculation of energy analysis of histidine(threetautomer) combined with Ag atom, calculation results showed that the third histidine tautomer combined with silver atom under the condition of solvation was most stable(lowest energy). SERS spectra characteristics of histidine adsorption layer on thesurface of the silver electrode under different electrode potential were discussed：When0mv ifrst negative move to-100mv and negative move to-500mv ifnallynegative moved to-1000mv，histidine molecules were mainly adsorbed on the silverelectrode surface through carboxyl firstly, then it turned into carboxyl and imidazoleirng but the main adsorption site was carboxyl，and turn into carboxyl and imidazoleirng were main adsorption sites, and turn into carboxyl as the main adsorption sitefinally but the spectrum peak strength is low showing that carboxyl relatively faraway from the electrode surface.(3) Electrochemical Redox of SERRS spectra analysis of azuirn fixed on thesurface of mercaptosuccinic acid self-assembled iflm，showing azuirn molecules werefixed on the surface of mercaptosuccinic acid molecules successfully through thecharacteirstic peaks of azurin appeared and showed good electrochemical activity ofSERRS. Wh2en potential near reduction potential(Cu+into Cu+) and oxidationpotential(C2u+into Cu+) from the electrochemical SERRS spectra data, azurinmolecules in space structure and configuration had obvious change, Adsorptionstructure of azuirn molecules from the spectral characterization was in favour ofelectron transfer between active center and the electrode surface.