Construction And Application Of Photoelectrochemical Sensor Based On Zinc And Tungsten Oxide Composite

In recent years,photochemical（PEC）detection method as a new analytical detection method began to appear and rise rapidly after relaying chemistry,photochemistry and optical analysis.The advantages of PEC sensor are high sensitivity,small background interference and fast response speed.After the chemical or physical interaction between the semiconductor nanomaterials or their composites with photoelectric active substances and the determind,the photocurrent or photovoltage changes,and then the quantitative determination of the determind can be realized.The key to successfully constructing a PEC sensor with excellent performance is the selection and design of highly active PEC nanomaterials and sensing strategies.As commonly used semiconductor nanomaterials,Zinc oxide（ZnO）and tungsten trioxide（WO₃）show superior biocompatibility and detection sensitivity in the construction of sensors due to their unique photoelectrochemical properties.However,in the construction of excellent performance PEC sensors,there are still many difficulties and challenges in how to synthesize green,pollution-free and low-cost active PEC nanomaterials,improve the photoelectric conversion efficiency of the materials,increase the selectivity of the sensor,and improve the detection method of the PEC sensor.In this work,by the modification of ZnO and WO₃,searching for suitable electron donors and designing novel sensor construction strategies,the novel and ultrasensitive PEC sensor was successfully construction,and then explore the application of PEC sensor in the tumor markers detection.（1）A novel and sensitive sandwich-type photoelectrochemical PEC sensor was developed for the quantitative detection ofb-amyloid protein（Ab）.A ITO electrode was sequentially coated with hierarchical porous ZnO microspheres with a large specific area,sensitized with tris（bipyridine）ruthenium（II）ion(Ru（bpy）₃²⁺)to achieve high visible light absorption,and modified with cerium-doped cadmium sulfide（Ce-Cd S）nanoparticles to enhance the PEC response.Under the stimulation of visible light and ascorbic acid（AA）as an efficient electron donor,the photoelectric signal of ZnO/Ru（bpy）₃²⁺/Ce-Cd S was 70 times that of pure ZnO.The amino-functionalized polystyrene（PS）microspheres coated with copper sulfide（CuS）was linked with a detection antibody of Ab（Ab₂）for the first time for the Abdetection by the sensor.The good insulation and steric resistance of the as-prepared polystyrene@CuS-Ab₂（PS@CuS-Ab₂）composite significantly weakened the photocurrent response of the sensor in the specific immune recognition.Under the optimal conditions,the quantitative detection of Aβwas achieved within the range of 0.001-100 ng·m L^-1 with the detection limit of 0.37 pg·m L^-1.（2）A new-type PEC sensor was prepared for supersensitive detection Aflatoxin B1（AFB1）.WO₃ nanoplates modified FTO electrodes were prepared by wet chemical route,and oriented TiO₂ nanoprickles were tightly and uniformly synthesized on the surface of WO₃ by chemical bath deposition（CBD）.The obtained WO₃/TiO₂ composite enhanced the PEC properties of WO₃.Then Ag₂O nanoparticles further formed on the surface of WO₃/TiO₂ composite.WO₃/TiO₂/Ag₂O composite structure materials modified FTO electrode showed wonderful photoelectric signal reaching about 56μA.When the logarithm of AFB1concentration was within the range of 0.005-0.4 ng·m L^-1,the photocurrents showed linear downward trend with a detection limit of 1.67 pg·m L^-1.（3）Using nitrogen-doped carbon quantum dots（NCQDs）and antimony trisulfide（Sb₂S₃）to co-sensitize the hydrangea-shaped tungsten trioxide WO₃,a novel PEC immunosensor was constructed to sensitively detect procalcitonin（PCT）.WO₃ possessed three-dimensional structure with uniform size and large surface area on the indium tin oxide（ITO）electrode.NCQDs had abundant carboxy groups and exhibited excitation-independent PEC behavior which were modified on the surface of WO₃ coating to enhance photochemical activity.Hence,the hydrangea-shaped WO₃/NCQDs/Sb₂S₃ composite was obtained by further modifying well-crystallized Sb₂S₃ nanoparticles on the surface of electrode.The photoelectric signal of WO₃/NCQDs/Sb₂S₃ was about 8 times that of pure WO₃ under visible light excitation.Moreover,the PEC immunosensor showed a large-scaled response(0.001-100 ng·m L^-1)and a low detection limit(0.42 pg·m L^-1).