Design,Preparation And Performance Study Of SiO₂@Ag-molecular Imprinted Polymers SERS Substrates

Antibiotics are chiefly used for human and animals in disease prevention and treatment.Antibiotics entered natural water will harm and even destroy the ecological balance.Amoxicillin(AMX)is one of the most commonly used?-lactams antibiotics and remains at trace levels in surface water,so detecting amoxicillin at trace level is of important meaning.The phenomena of surface-enhanced Raman scattering(SERS)describe that significantly enhanced Raman signals are obtained when probe molecules are adsorbed on rough surfaces of specific materials.Currently,SERS is an analytical method with simple operation,low detection limits,low manufacturing and testing costs and highly resolvable signal peaks,which can be used for nondestructive rapid detection and is widely used in the field of pollutant detection.However,Ag nanoparticles,the typical metallic materials utilized for SERS will aggregate into larger irregularly shaped particles at the action of high surface energy and the agglomeration can weaken the SERS activity and reduce the sensitivity of SERS substrates.In this study,SiO₂,the inert non-metallic material which is not only excellent in chemical stability,optical properties and morphological controllability but also easy to get cheap starting materials and easy to prepare was introduced into the SERS substrates and the forming of SiO₂@Ag nanocomposites contributed to regulating the distance between Ag particles,which simply and effectively avoided particles from agglomerating,reduced the amount of Ag and the manufacturing cost of SERS substrates and improved the SERS-sensitivity and stability.The average intensity of SERS characteristic peaks collected from SiO₂@Ag was about 1.14 times of that from Ag nanoparticles.After stored at room temperature in centrifuge tubes for 200 days,the SERS-activity of SiO₂@Ag maintained at about 90%of the initial value.SiO₂@Ag could universally detect different kinds of pollutants and the minimum detectable concentration was 100.0 ng/m L for amoxicillin.Molecular imprinting technique(MIT)is a technique for preparing molecular imprinted polymers(MIPs)that can specifically select target molecules that match templates in molecular structure and chemical groups by the cavities formed by removing templates.Traditional SERS substrates are hard to achieve specific detection and integrating SERS and MIT can improve the performances of SERS substrates in many directions.In this research,for detecting amoxicillin in complex samples by SERS,used Gaussian09 software to simulate the molecular imprinting systems and direct the selections of the optimum functional monomers and molar ratios.Simulated results were used to guide the design of MIPs.Coated MIPs layers thinner than 10 nm on SiO₂@Ag and then SiO₂@Ag@MIPs nanocomposites were synthesized as the MIPs-SERS substrates.The existence of MIPs layers helped concentrate specific analyte amoxicillin and the minimum detectable concentration was as low as 1.0 ng/m L on SiO₂@Ag@MIPs.Enhancement factors were 2.97×10⁵ of SiO₂@Ag and 1.63×10⁶of SiO₂@Ag@MIPs,respectively.The results indicated that both SiO₂@Ag and SiO₂@Ag@MIPs had excellent SERS enhancement performance,and could achieve qualitative and semi-quantitative analysis of AMX in aqueous media.