Fabrication Of A Uniform Surface Enhanced Raman Scattering Substrate And Its Application

Since 1970s, surface-enhanced Raman spectroscopy (SERS) has been applied widely in surface science, analytical science, electrochemistry, biochemistry and materials for its high detection sensitivity. The SERS effect depends not only on the property science due to its extremely high sensitivity. The activity of SERS effect was depended on the nature of the metal as well as the size and shape of the metal microstructure. At present, the poor generality and reproducibility of SERS substrate limited the practical application of SERS technique. Therefore, key issues on the extension of SERS to practical application are how to obtain uniform, stable and reproducible SERS substrates. In this thesis, stable and uniform SERS substrates were fabricated at water/oil interface, and its application was addressed. The main results of this thesis are listed as follows:1) The SiO₂ shell with the thickness of 4 nm was attached onto high SERS active Au core nanoparticles to obtain Au@SiO₂ core shell nanoparticles by the hydrolysis of sodium silicate solution with the boiling water bath. The inert shell of SiO₂ isolated the direct interaction of Au nanoparticles and probe molecules.2) Exploring the function of the organic solvents and additives. The compact Au and Au@SiO₂ nanoparticles films were fabricated at water/oil interface by adding different oil phases and additives. The conditions for the film formation were optimized by changing the solvents and additives. The mechanism of film formation at two-phase interface was proposed.3) Investigating the uniformity, stability, reproducibility and cleanliness of the film substrates by transferring the nanoparticles film from the oil/water interface to a solid substrate. The result revealed that the film was a candidate with high-quality performances for the SERS application. By using the prepared film substrate, the detection on the MBA or melamine solutions with ddifferent concentration, and the adsorption on a single crystal Au surface were performed.4) Investigating the relationship between the SERS activist and the layer numbers of Au@SiO₂ nanoparticles by transferring different layers of Au@SiO₂ film to a same solid substrate. The SERS effect was increasing with the increase of film layers, and it kept in constant as the film was over 5 layers. The screening effect of the film on the underneath SERS signal was investigated. Two layers of Au@SiO₂ film induced a coupling effect which resulted in a maximum SERS signal from the underneath probe molecules. With the increasing the layers of the Au@SiO₂ film, the SERS signal was screened completely.