Application Of Metal Oxide/sulfide Composites In Paper-based Photoelectrochemical Sensing

In recent years,photoelectrochemical biosensors have been widely used in the field of disease diagnosis,environmental monitoring and food safety because of its simple operation,good selectivity,high sensitivity and easy miniaturization.Metal oxides are a kind of semiconductor material with virtue of good chemical stability and high electron mobility.However,most of the metal oxides with wide band gap could not be excited by visible light,which limits their application in the field of photoelectrochemical sensing.Exhilaratingly,metal sulfides with narrow band gap are easily excited by visible light,but its output signal is unstable.In this paper,to overcome the defect of single material,metal oxide/sulfide composites were prepared by combining metal oxide with metal sulfide,which could effectively reduce the electron-hole recombination rate and expand the light absorption range and improve the performance of photoelectrochemical sensors.In addition,the development of photoelectrochemical biosensors tend to miniaturization and integration.Nowadays,flexible paper-based biosensor has attracted substantial focus due to its merits of low price and environmentally friendly.Based on the paper-based sensing research work of our research group,different paper-based photoelectrochemical biosensors were designed combined with the photoelectrochemical sensing application of photosensitive materials.The metal oxide/sulfide composites with excellent performance were prepared,and different signal amplification strategies were designed according to the generation mechanism of photoelectrochemical signal to realize the rapid and highly sensitive detection of target biomolecules.The main research work are as follows:(1)The cuprous oxide and titanium dioxide were prepared by electrodeposition technique and liquid phase hydrolysis respectively,which were further sensitized by different metal sulfide nanomaterials with narrow band gap to obtain the metal oxide/sulfide cascaded photosensitive structures.The resulting cascaded photosensitive structures could not only broaden the visible light absorption range but also inhibit the photogenerated electron-hole recombination,thus greatly enhancing the photocurrent response.(2)The cuprous oxide/bismuth sulfide-bismuth vanadate cascade photosensitive structures were assembled on paper electrode and used as the photocathode.By coupling the duplex-specific-nuclease-induced target recycling reaction with multiple branched hybridization chain reaction,the DNA dendrimer was prepared to load hemin and platinum nanoparticles.The resulting DNA dendrimer could efficiently catalyze the decomposition of hydrogen peroxide for in situ generation of oxygen as the electron acceptor,leading to the photocurrent responses enhancement.Thus,the ultrasensitive mi RNA determination was realized.(3)The polypyrrole functionalized paper electrode was prepared by in situ chemical polymerization and used for the assembly of titanium dioxide/zinc indium sulfide photosensitive structures.Bovine serum albumin modified manganese dioxide with double enzyme characteristics were synthesized,which were loaded on the DNA double-stranded cascade structures and used as the signal amplifiers.Based on its intrinsic photoelectric and peroxidase-like properties,the multiple quenching of photocurrent signal was realized.Meanwhile,the bovine serum albumin modified manganese dioxide could catalyze the color reaction due to its oxidase-like properties.Thus,the the visual pre-detection and photoelectrochemical quantitative analysis of mucin-1 were achieved.