TiO₂ SERS-active Substrate With The Integrated Detection And Degradation Of Drug Pollutant

Objective Ag simultaneously deposited and doped titanium dioxide nanoparticles（Ag-TiO₂ NPs）were synthesized by a sol-hydrothermal method,as both a sensitive surface-enhanced Raman scattering（SERS）substrate and a superior photocatalyst for the first time.And Ag-TiO₂ exhibits excellent SERS performance and high photocatalytic degradation activity for several drug pollutant molecules.This not only improves the SERS performance of semiconductor TiO₂,expands the application of TiO₂ as SERS active-substrate,but also establishes the research method of drug pollutant detection based on SERS technology.At the same time,the interaction mechanism between the drug molecules and composite substrates and the photocatalytic degradation mechanism of Ag-TiO₂ for residual drug pollutants were explored,and it can provide theoretical and experiental basis for effective monitoring and control of drug pollutant residues in the environment.Methods In this paper,Ag-TiO₂ was synthesized by a sol-hydrothermal method,and it was characterized by relevant means.Then it was used as both a SERS substrate and a photocatalyst to detect and degrade the atandard probe molecule and several quinolone drug residues.Meanwhile,the stability and applicability of the hybrid and the effects of different drug concentration,adsorption time and pH value on the interaction between drug molecule and the substrate were investigated.Results The SERS properities of Ag-TiO₂ substrates were explored by using4-mercaptobenzoic acid（4-MBA）as standard probe molecule.The results show that the Ag-TiO₂ possesses stronger SERS enhancement effect when compared with pure TiO₂substrate,which is attributed to the synergistic contribution of noble metal and semiconductor.On the Ag-TiO₂ substrate,the detection limits of ciprofloxacin,enrofloxacin,dafloxacin,difloxacin hydrochloride and enoxacin were 7.07×10^-11,3.94×10^-11,3.16×10^-11,8.91×10^-12 and 3.15×10^-10 mol/L,respectively,which are far below European Union standard(3.01×10^-7 mol/L).At the same time,the Ag-TiO₂ NPs exhibit high photocatalytic activity for each drug pollutant.Conclusions The SERS performance of semiconductor TiO₂ was improved greatly assisted by the simultaneously deposited and doped Ag,and this expands the application of TiO₂ as SERS active-substrate.The SERS enhancement of Ag-TiO₂ NPs is attributed to the Chemical Enhancement of original“TiO₂-to-molecule”charge transfer and the Electromagnetic Enhancement of plasma resonance contribution of Ag deposited on the surface of TiO₂,as well as the additional SERS enhancement caused by the synergistic effect of noble metal Ag and semiconductor TiO₂.The researches on the detection and degradation of various drug pollutants by the new TiO₂ composite material have achieved good results.This not only expands the application of SERS technology in practical analysis field,but also provides theoretical and experiental basis for effective monitoring and control of drug pollutant residues in the environment.