Growth Of Indium-Based Sulfide Materials On Paper Chip And Their Application Research In Photoelectrochemical Biosensing

Photoelectrochemical（PEC）biosensor as an analytical method based on PEC reaction and biological recognition technology,has exhibited great application prospects in food safety and environmental monitoring on account of high sensitivity,low cost and easy miniaturization.In the construction of PEC biosensors,the selection and design of excellent photoelectric materials is the key and prerequisite to improve the photocurrent signal.Indium-based sulfide has showed great development potential owing to its high light absorption coefficient,good sensitization performance and simple synthesis method.However,the application of unmodified indium-based sulfide is restricted due to its low photoelectric conversion efficiency and poor optical stability.The composite material with energy level matching can facilitate the separation of photogenerated electrons and holes to realize the stable output of photocurrent signals,which has become the main research direction in the field of PEC sensing.In this work,cellulose paper is selected as the flexible substrate.Benefiting from the portability,easy functionalization and integration of microfluidic paper chips,a variety of indium-based sulfide are constructed on the surface of paper fibers,and the photoelectric conversion efficiency of nanomaterials is improved by nanostructure design,heterostructure construction and defect engineering.Moreover,novel signal amplification strategy was explored to enhance the transfer and separation efficiency of photogenerated carriers,and a series of paper-based PEC biosensors with excellent performance were successfully constructed to achieve accurate detection of various environmental pollutants.（1）Based on sensitized In₂S₃/WO₃ composite and target-driven self-feedback mechanism of dual-cycle strategy,a label-free PEC biosensor was successfully constructed for the sensitive detection of ochratoxin A.A two-step in-situ growth method was used to modify the In₂S₃/WO₃heterojunction on the surface of cellulose paper.Based on the matching energy level structure and core-shell morphology,the photogenerated carrier separation and PEC performance were greatly improved.A target-induced Exo-III assisted DNA cycle,combined with the PEC-chemical-chemical oxidation-reduction cycle process induced by photogenic holes,was designed to induce multiple amplification of the PEC sensor biological analysis signal and realize the ultrasensitive detection of ochratoxin A.（2）According to the principle of energy level matching,a paper-based Cd In₂S₄/Fe OOH heterojunction was designed and prepared.The Cd In₂S₄/Fe OOH heterojunction was thermally treated with polyvinyl pyrrolidone solution to achieve sulfur vacancies introduction in two-dimensional layered indium cadmium sulfide.Integrating the electric field at the interface of heterojunction and external-magnetic field enhanced spin polarization effect,the separation and transmission of photogenerated electrons and holes in the heterojunction layer are driven cooperatively,which overcomes the bottleneck problem of the rapid recombination of carriers in inorganic semiconductor photosensitive materials,and lays the foundation for the construction of high-performance PEC biosensors.（3）A signal probe labeled Zn Fe₂O₄ with wide spectral response and absorption was designed and introduced as a multiple signal amplifier.With the help of hybrid chain reaction,Zn Fe₂O₄ was loaded on the surface of Cd In₂S₄/Fe OOH paper chip,and a magnetic field assisted“Cd In₂S₄/Fe OOH-Zn Fe₂O₄”competitive multistage signal amplification was constructed.Combined with the peroxide oxidase properties of Zn Fe₂O₄,the enzyme-catalyzed precipitation reaction was introduced on the surface of the electrode,further intensifying the PEC signal attenuation effect,and realizing the ultrasensitive detection of chlorpyrifos.