Fabrication Of Composite SERS Substrate Of Nano-silver On Graphene And Quantitative Analysis Of Sulfur Of Thiophene

Sulfur in vehicle gasoline can produces sulfur oxides during the combustion process,which corrode the engine and exhaust system,fail the tail gas catalytic system and it can cause acid rain,haze and other serious environmental problems seriously.The sulfur content in gasoline is strictly limited to 10 mg/L for the national standard?,that is much lower than the detection limit of the commonly method.And the study of new detection methods become very urgent as the implementation of the standard?.Surface-enhanced Raman spectroscopy?SERS?,having the advantages of high detection sensibility,low detection limit and fast analysis speed,is a rising tool for sensing molecules in trace amounts and the key to SERS research is the preparation of active substrates.In this paper,analytical results were obtained that several new nano-silver/graphene composite substrates were prepared for the determination of thiophene sulfur in gasoline.Nano silver/graphene substrate were prepared in the ethanol system?Ethanol+polyvinylpyrrolidone+graphene?and in the carbonyl tungsten system?carbonyl tungsten+oleic acid+oil amine?.A research about effects on the morphology of nano silver/graphene SERS performance were investigated,it was found that the nano-silver formed on the surface of the two layers graphene was uniform and the Raman enhancement effect was strong,and the enhancement factor was 1.45×10⁸,which further optimized the new active substrate and laid the foundation for quantitative analysis.The Au/graphene/silver composite substrate was synthesized by electrochemical method after graphene bonding to the gold electrode by diazotization.The Raman enhancement intensity effects factors including reaction precursors,potential,electrolysis time were investigated by SEM and Raman spectroscopy.The results showed that most of the silver prepared was the face-centered cubic structure in the silver nitrate system?potassium nitrate+silver nitrate+PVP?.When the set voltage is 0.2V?vs.SCE?,the electrolysis time is 1500s,the SERS spectrum showed the enhancement factor is 3.0×10⁸.Furtherly explore the mechanism of the graphene in nano-silver/graphene,the effects of morphology and crystal face on SERS were investigated by combining IR,Raman,UV-vis and XRD,from the aspects of electromagnetic enhancement and chemical enhancement.The composite substrate prepared was used for the determination of thiophene sulfur in n-hexane-thiophene simulated gasoline and gasoline.Then find the linear relationships between the sulfur content and the corresponding peak in the 5⁶0 mg·kg^-1 range of simulated gasoline,y=0.0115x+0.7713,R²=0.985.Thiophene sulfur content of 95#gasoline were 13.29 mg·kg^-1,the average recovery was 102.3%and RSD was 4.12%.The feasibility of surface-enhanced Raman spectroscopy combining nano-silver/graphene substrate with the determination of thiophene sulfur in gasoline was furtherly verified,and it was a green and easy path for determination of trace sulfur.