Study On Preparation Of New Noble Metal Surface Enhanced Raman Base Material

In recent years,SERS and related technologies have been able to detect single molecules of some substances,with enhancement coefficients of up to 8 to 14 orders of magnitude.Preparation of a silica microsphere loaded with noble metal nanoparticles,the preparation method is simple and generates fewer pollutants;optimize the preparation conditions,improve the SERS enhancement ability of the material;under normal circumstances,noble metal nanoparticles have catalytic activity,catalytic chemical reactions At the same time,real-time Raman detection of the catalytic reaction is realized.The purpose of this thesis is to prepare a super-sensitive and catalytically active bifunctional metal SERS substrate to realize the trace level detection of single-molecule analytes and the real-time detection of catalytic reactions.The main research content can be summarized into the following three parts:Silica microspheres with a particle size of about 1.3?m were prepared by the sol-gel method,and silver nanoparticles were grown in situ on the surface to prepare AgNPs@SiO₂ microspheres.The morphology of silver nanoparticles on the surface of microspheres was characterized by high resolution transmission electron microscopy?HRTEM?and scanning electron microscopy?SEM?.Different concentrations of rhodamine 6G solutions were prepared as probe molecules to detect the SERS performance of the substrate.The detection limit was 10^-11mol/L,and the enhancement factor of the substrate could be 10⁷ after calculation.Subsequently,the uniformity and stability of the substrate were tested,and the relative standard deviation was 6.31%.At 20°C,the SERS activity could be stably maintained for about 16 days.By improving the experimental methods and conditions,silica submicrospheres with a particle size of about 100 nm were prepared,and silver nanoparticles were grown in situ on the surface using the same method.Using silver nanoparticles on the surface of silica submicrospheres as a sacrificial template,AuNPs@SiO₂submicrosphere substrates were prepared by metal substitution reaction.Compared with silver nanoparticles,gold nanoparticles have more stable chemical properties and catalytic activity.Ultraviolet spectrophotometer?UV-vis?was used to detect the progress of the replacement reaction.The characterization of HRTEM and X-ray photoelectron spectroscopy?XPS?further confirmed the formation of gold nanoparticles.The research found that AuNPs@SiO₂ submicrospheres have better properties as SERS substrates.The detection limit is 10^-13mol/L,the enhancement coefficient can reach 10⁹,the relative standard deviation is 4.57%,and the temperature at 20°C Under the conditions,SERS activity can be stably maintained for about 160 days.It is also applied to the detection of nitrogen-containing dyes in the printing and dyeing industries such as CV?crystal violet?and MG?malachite green?,with detection limits up to 10^-1111 mol/L.When AuNPs@SiO₂ submicrospheres are used as catalysts for styrene epoxidation,the conversion of styrene can reach 46.7%and the selectivity can reach91.7%.After the catalytic reaction was repeated for 10 cycles,there was no significant change in the conversion and selectivity of the catalytic reaction.AuNPs@SiO₂ was used as a catalyst to catalyze the reaction of 4-Nitrothiophenol?4-NTP?.The influence of different reaction conditions on the catalytic reaction was tested by UV-vis.Finally,based on AuNPs@SiO₂ submicrospheres,real-time detection of 4-NTP catalytic reaction was realized by SERS technology.