Novel Photoelectric Composites And Their Application In Photoelectrochemical Bioanalysis

Photoelectrochemical（PEC）bioanalysis is a novel detection technology that converts biochemical information into photocurrent or photovoltage signals through photoelectric active materials and biological recognition elements.Due to the different energy forms of the excitation light source and the detection signal,PEC biosensors possess the advantages of low background signal,simple equipment,easy miniaturization,etc.,and exhibit promising prospects in the field of biological analysis.Therefore,the construction of novel high-efficiency PEC biosensing systems to maximize the superiority of the PEC sensors is a very meaningful work in the field of bioanalysis.As a medium for converting light energy into electrical energy,photoelectric active materials are the key to the construction of the sensor due to the performances of them directly affect the detection effects of the PEC sensors.Thus,rational design and preparation of photoelectric active materials with excellent photoelectric conversion efficiency,anti-interference performance,good biocompatibility,and further explore its microscopic mechanism of action are important research directions for constructing PEC biosensors.Moreover,it is a very significant research work in the field of bioanalysis to establish novel PEC system with excellent bioanalytical performance by combining these advanced materials with specific biological recognition elements through reasonable design.This thesis mainly prepared novel photoelectric composites with excellent performance based on cadmium-free and low-toxicity photoelectric active materials,and discussed the mechanism of photoelectric enhancements in depth through experiments and theoretical analysis,which provide theoretical support for the subsequent analytical application of these composites.Finally,though combining with the impact of the specific enzyme-catalyzed reaction process on photoelectric performance,a series of PEC biological detection platforms with high sensitivity and good selectivity were constructed,and realized the high-performance analysis toward alkaline phosphatase（ALP）,glucose oxidase（GOD）and glucose.The specific research works of this thesis mainly were carried out in the following parts:1.OverviewFirstly,this chapter introduced the specific overview of PEC bioanalysis systems based on their basic structure,detection principle and classification;Then,the latest research progresses and development trends of PEC biosensors were discussed combining the types of photoelectric active materials,enhancement mechanism of PEC composites and PEC biosensing modes;Finally,though combining with the above-mentioned development foundation,the starting points and thinking of the research for this thesis were introduced.The origins and ideas of the research for this thesis were introduced by combining with the above-mentioned development foundations.2.PEC biosensor based on Au nanoclusters-Ag@SiO₂ nanocomposites for alkaline phosphatase activity analysis（1）Au nanoclusters-decorated Ag@SiO₂（Au NCs-Ag@SiO₂）nanocomposites with excellent PEC properties were prepared by employing the low-toxicity Au NCs with quantum dots-properties as the photoelectric active materials and plasmonic metal to enhance the photoelectric properties.Particularly,the distances between Au NCs and plasmonic Ag nanoparticles（Ag NPs）were regulated through adjusting the thicknesses of silica shell layers.An optimal photoelectric enhancement effect of 3.8 times was obtained,when the enhancement functions of hot electron transfer,local electric field,light scattering effects relative to the quenching functions of nonradiative energy transfer of plasmonic Ag NPs reached the optimum.Furthermore,an explanation toward the photoelectric enhancement mechanism was provided by comparing the experimental with the theoretical simulation results,which provided some theoretical guidance in designing of plasmonic nanostructures for advisable photoelectric signal enhancement and subsequent bioanalysis research.（2）Based on the above studies,an Au NCs-Ag@SiO₂ nanocomposites-based PEC enzymatic sensor was successfully constructed for the analysis of ALP activity with the help of ALP catalytic substrate generating electron donor（ascorbic acid,AA）in situ to enhance the photocurrent response.The sensitive and selective analysis toward ALP activity was realized due to the excellent photoelectric properties and high sensitivity against AA of the prepared Au NCs-Ag@SiO₂ nanocomposites.Moreover,the research would provide a basis for the application of nontoxic and biocompatible Au NCs in PEC bioanalysis.3.Cathodic PEC biosensor based on ZnAgInS quantum dots-BiOI heterostructures for glucose oxidase and glucose analysis（1）A novel ZnAgInS quantum dots-decorated BiOI microspheres（BiOI-ZAIS）heterostructure was designed based on cadmium-free ZAIS quantum dots and p-type BiOI microspheres.Specifically,the designed BiOI-ZAIS composites displayed significantly enhanced cathodic photocurrent responses compared with individual BiOI microspheres and ZAIS QDs due to its improved charge separation efficiency.Furthermore,the Z-scheme migration mechanism of photoinduced carriers for the BiOI-ZAIS heterostructure was proposed according to the experimental results and energy level analysis.（2）Based on the above studies,a cathodic PEC bioanalysis system was successfully constructed by means of GOD catalyzing the consumption of dissolved O₂ in the solution to suppress the generation of photocurrent.The sensitivity analysis of GOD and glucose was achieved attributed to the excellent PEC performance of BiOI-ZAIS heterostructures and the sensitivity of photocathode toward dissolved O₂.Notably,the fabricated PEC bioanalysis system based on the BiOI-ZAIS heterostructure exhibited satisfactory selectivity due to the favorable anti-interference capability for photocathode toward reducing substances in solution and the specificity of the enzymatic reaction.Moreover,this research was hoped to inspire interest in the design and development of other high-efficiency and nontoxic Z-scheme heterostructures for elegant PEC bioanalysis.