The Study And Application Of Surface-enhanced Raman Spectroscopy (SERS) Based On Gold Nanoparticles

Due to the controllable preparation and unique optical properties, gold nanoparticles become one of the most commonly used active substrates of surface enhanced Raman spectroscopy (SERS). The spectrum information of analyst can be collected by SERS in molecular level because of its high sensitivity. It can also obtain high quality Raman signal of molecular. Therefore, it is widely used to study the adsorption behavior of the surface molecule.In this thesis, gold nanoparticles were assembled as SERS substrate to study molecular adsorption structure in electrochemical process. Density functional theory (DFT) was used as theoretical guidance. Then the shape and structure of gold nanoparticles were expanded. It explored a rapid synthesis method of novel SERS active material with manoeuvrable ultra-thin shell and tunable surface plasma resonance. It studied the influence of theirs variable structure which used for SERS. Lastly they were applied to detection.The main research contents and conclusions of this thesis are listed as follows.(1) Gold nanoparticles can generate strong electromagnetic field to give a large enhancement of absorbed molecules. Therefore, gold nanoparticles were used for SERS to study the adsorption structure of hypoxanthine during electrochemical process. Utilizing DFT technology, we studied keto form and enol form hypoxanthine with gold. Single point energy, charge distribution, molecular orbitals and vibration spectrum of hypoxanthine/gold system were given. Then the energies to form bonds of hypoxanthine/gold cluster were simulated to elect a suitable gold cluster. At last, SERS spectra of different N atoms adsorbed with gold were calculated. Combined with these DFT results, electrochemical surface enhanced Raman spectroscopy (EC-SERS) was applied to research the properties of hypoxanthine/gold interface. The structure of adsorbed hypoxanthine was changed from slightly tilted to upright with negative move of potential. Finally we investigated the surface case in gold-plating process by in-situ technology.(2) In this chapter, the spherical gold nanoparticls were expanded to rods so as to utilize the traits of shell-isolated strategy and further advance the SHINERS technique. It firstly introduced a rapid synthesis method of silica-coating Au nanorods (Au@SiO2 NRs) with manoeuvrable ultra-thin shell. The particles were characterized by extinction spectra, SEM, TEM, electrochemical and zeta potential. The nanorods particles with tunable surface plasma resonance (SPR) wavelength which applied in SERS and excited by different laser presented diverse enhancement effect. The core-shell Au@SiO2 NRs were used to successfully obtain the enhanced signal of malachite green in solution Raman tests, giving a good consequence to semi-quantitative detection.