Multiple Sensitization Of Paper-based Zinc Oxide And Its Application In Photoelectrochemical Biosensors

Photoelectrochemical sensors have been widely applied in industrial production,disease diagnosis and treatment,and environmental protection,etc.Particularly,photosensitive materials with suitable band gaps and higher carrier mobility play a vital role in obtaining ideal photocurrent signals.Zinc oxide,as a widely used broad band gap semiconductor material,has satisfactory photoelectric performance and good chemical stability.However,zinc oxide with the wide band gap can only be excited under ultraviolet light,and the photo-generated electron-hole pairs are easily recombined,which greatly limits the application of zinc oxide in photoelectrochemical sensing.In order to solve its inherent defects,different semiconductor nanomaterials with narrow band gap are used for the sensitization of ZnO,which could greatly improve the performance of photoelectrochemical sensors.Cellulose paper possess some excellent characteristics,such as high porosity,large surface area,easy modification,and good flexibility.It has been used as a high-affinity matrix for the functionalization of nanomaterials.Based on the basic research of our group in the field of paper-based sensing devices,the paper-based zinc oxide with different morphologies were prepared and further sensitized with multiple photoactive materials.Combining with different photoelectric signal amplification strategies,different paper-based photoelectrochemical biosensing platforms were constructed for sensitive monitoring of tumor markers.This work mainly includes the following aspects:(1)The zinc oxide nanotubes and nanosheets were in situ grown on the surface of paper gold electrode by using electrodeposition technology.The zinc oxide nanomaterials have a large specific surface area,which could provide more active sites for the further multiple sensitization.(2)Based on the origami principle,a simple paper-based detection device was independently designed,and the narrow band gap core-shell quantum dot was employed to sensitize zinc oxide.Using the charge separation and recombination mechanism of core-shell quantum dots and the energy transfer mechanism between gold nanoparticles and cadmium sulfide quantum dots,the signal-switching was realized with the help of the conformation change of triple helix molecular switch,achieving the sensitive detection of prostate-specifc antigen.(3)Based on the hydrophilicity of paper and the hydrophobicity of wax,a hollow channel microfluidic paper-based sensing device integrating different functional areas was designed,and low-toxic copper indium sulfur nanospheres and silver selenide quantum dots were used to sensitize zinc oxide.Benefiting from the formed cascade multiple sensitization structure and the double-cycle amplification strategy,the detection of trace microRNA was realized.