Fabrication Of Molecularly Imprinted Electrochemical And Photoelectrochemical Sensors Based On Sn₃O₄ And Their Applications In Food Safety Detection

Sn3O4 is a mixed valence tin oxide,which belongs to the n-type inorganic semiconductor nanomaterials.Its thermodynamically stable crystal structure,excellent photoelectric properties and visible light absorbtance made it widely used in photocatalysis and other fields.However,there is little application of Sn3O4 in electrochemical and photoelectrochemical sensors.Molecularly imprinted electrochemical and photoelectrochemical sensors have the advantages of high selectivity,good stability,low background signal and high sensitivity.At present,technologies for food safety detection have many problems,such as high cost,complex structure,cumbersome pretreatment process and time-consuming operation.Therefore,it is very important to develop a rapid,accurate and sensitive technology for the detection of pesticides,antibiotics and other residues in food.Therefore,in this paper,we constructed the molecular imprinting electrochemical and photoelectrochemical sensor for the detection of metronidazole and 2,4-dichlorophenoxyacetic acid,using Sn3O4 as photo/electroactive materials and molecular imprinting as sensing recognition strategy,further studied its application in food safety detection.Part ? A novel metronidazole electrochemical sensor based on surface imprinted vertically cross-linked two-dimensional Sn3O4 nanosheetsA simple one-step solvothermal reaction was applied to fabricate the vertically cross-linked two-dimensional Sn3O4 nanosheets.Sn3O4 nanosheets ars promising as a support for imprinting.Chemical oxidation method was applied to prepare the molecularly imprinted polymer by using metronidazole as the template,pyrrole as the functional monomer.SEM,XRD,XPS and FT-IR were applied to the characterization of the as-prepared MIPPy/Sn3O4.A novel electrochemical sensor for metronidazole detection was constructed by modifying MIPPy/Sn3O4 on the surface of GCE,and parameters affecting the performance of this sensor were thoroughly investigated and optimized.The DPV peak currents produced on the MIPPy/Sn3O4/GCE electrochemical sensor afforded a wide linear relationship among 2.5×10-8-2.5×10-6 mol·L-1 and a detection limit down to 3.2×10-9 mol·L-1(S/N=3).The successful detection of metronidazole in honeybee samples has been acquired.Part ? High sensitive visible light photoelectrochemical sensor based on in-situ prepared flexible Sn3O4 nanosheets and molecularly imprinted polymersSn3O4 nanosheets as the visible light-active species were directly in-situ fabricated on a CFP by a simple one-step solvothermal process.This is the first application of Sn3O4 in the field of photoelectrochemical sensors.2,4-dichlorophenoxyacetic acid as template molecule and pyrrole as functional monomer were directly electropolymerized on the surface of Sn3O4/CFP to form a molecularly imprinted polypyrrole film.SEM,XRD and XPS were applied to the characterization of the as-prepared MIPPy/Sn3O4/CFP.Thanks to the structural advantages of Sn3O4/CFP and the high selectivity of MIP,the linear range of this photoelectrochemiacal sensor for 2,4-dichlorophenoxyacetic acid detection was 5.0×10-11-1.0×10×10-7 mol·L-1,and the detection limit was lower to 1.1×10-11 mol· L-1(S/N=3).It demonstrated excellent stability,selectivity as well as remarkably sensitivity.The 2,4-dichlorophenoxyacetic acid detection has been successfully acquired in bean sprout samples.Part ? High sensitive visible light photoelectrochemical sensor based on in-situ prepared flexible rGO/Sn3O4 nanosheets and molecularly imprinted polymersGraphene oxide prepared by Hummers method was reduced by a simple one-step solvothermal method using trisodium citrate as the reducing agent,and successfully compounded with Sn3O4 on CFP.The rGO/Sn3O4/CFP photoactive electrode was prepared and applied to the construction of photoelectrochemical sensors.Owing to the good electrical conductivity,high specific surface area,high electron mobility and good stability of rGO,its synergistic effect with Sn3O4 can significantly improve the electrochemical and photoelectrochemical properties of Sn3O4,further improving its stability.SEM,FT-IR,XRD,XPS,Raman and UV-vis DRS were applied to the characterization of the MIPPy/rGO/Sn3O4/CFP,which was prepared by electropolymerization.The results showed that 2,4-dichlorophenoxyacetic acid molecularly imprinted photoelectrochemical sensor had better detection sensitivity.The linear detection range was 5.0×10-12-1.0×10-9 mol·L-1,and the detection limit was lower to 1.5×10-12 mol·L-1(S/N=3).The 2,4-dichlorophenoxyacetic acid detection has been successfully acquired in bean sprout samples.