Construction And Application Of Nano Zinc Oxide Based Photoelectrochemical Biosensor

With the improvement of people's living standard and the changes in lifestyles,some diseases are becoming more prevalent among a younger age group.Early disease screening is crucial for the diagnosis and treatment of diseases.With the rapid development of nanotechnology,electrochemical sensors have been continuously applied in the field of detection.Electrochemical biosensors have the advantages of rapidity,sensitivity and simplicity,especially photoelectrochemical(PEC)biosensors developed on this basis,which further realize the energy conversion of detection signal and excitation signal,and have wide application potential in disease diagnosis.Recently,a variety of new nanomaterials have been designed and prepared to improve the performance of biosensor.Nano zinc oxide(ZnO)material has the unique advantages of photoelectric conversion due to its physical characteristics of high carrier concentration and high mobility,and it has high isoelectric point and good biocompatibility.It plays an important role in the field of photoelectrochemistry and related biosensors.Although ZnO has many excellent properties,the light absorption of ZnO is mainly in the ultraviolet region,which seriously hinders its application in biosensing.In recent years,researchers have done a lot of work around how to improve the photoelectric response of ZnO and how to achieve efficient sensing.There are usually two major problems to solve for improving the photoelectric response of ZnO:(?)how to improve the efficiency separation of electron-hole;(?)how to broaden the light absorption range of ZnO.Based on this,in this paper,ZnO with three-dimensional structure was prepared,metals and semiconductors were further introduced to enhance the photocurrent response of ZnO,and improve the sensitivity of biosensor to realized the sensitive detection of dopamine,glutathione,Escherichia coli and cardiac troponin I.The main research contents are as follows:1.Photoelectrochemical response to glutathione in A u-decorated ZnO nanorod array.It has been reported that the photocurrent will increase after Au modified ZnO.But the coupling enhancement mechanism has not been explained clearly.Our research group found that after Au modified ZnO,Au would enhance the intrinsic emission intensity of ZnO.Inspired by this,in this work,the electrode with Au-ZnO was introducted to the external circuit,and the enhanced photocurrent of Au-ZnO was obtained than ZnO.It means that the excited Au surface plasma transfers to the conduction band of ZnO,forming the circuit current.We designed experiments with two monochromatic beams of 325 nm and 532 nm as light sources to verify the charge transfer process.Moreover,the electromagnetic field simulation was used to analyze the light field distribution at the liquid-solid interface,and a physical model for glutathione detection based on Au-ZnO was further proposed.Subsequently,the rapid detection of glutathione was completed.2.CdS quantum dots/Au nanoparticles/ZnO nanowire array for self-powered photoelectrochemical detection of Escherichia coli 0157:H7.In the last work,we verified the introduction of plasma can improve the photocurrent response of ZnO by theory and experiment.In addition,the photocurrent response can also be improved by widening the light absorption of ZnO.The light absorption of ZnO is mainly in the ultraviolet band,and the introduction of narrow band gap semiconductors can broaden its light absorption range from ultraviolet light to visible light.CdS is a representative narrow band gap semiconductor.Some researches found that the combination of ZnO and CdS could improve the photocurrent response.However,CdS has certain biological toxicity.Therefore,we firstly assembled CdS quantum dots(QDs)with aptamers,and then modified the photoanode interface constructed by ZnO and Au to further enhance the photocurrent response with nice the aptamer activity.In the detection of E.coli,it was found that the sensitivity of the sensor was 1.7 times higher than that of the unmodified CdS QDs.This strategy is also applicable to the construction of other aptamer sensors and has broad prospects in the field of bioanalysis.3.Enhanced photoelectrochemical immunoassay for cardiac troponin I based on NiO/Au NPs/ZnO nanowires and biocatalytic precipitation amplification.In the construction of photoelectrochemical immunosensors,the primary concern is also the construction of photoelectric interfaces.In this work,nickel oxide(NiO)and ZnO are introduced to form a p-n-type heterojunction to enhance the photocurrent response.Although various chemical methods have been used to construct heterojunctions,the interface is not uniformity.Here,the physical deposition methods,including plasma sputtering and magnetron sputtering,were used to achieve the coaxial heterojunctions with good consistency.In addition to affecting the generation of photocurrent through the construction of the photoanode interface,HRP-induced biocatalytic precipitation can also be introduced to form steric hindrance to hinder electron transfer and achieve signal amplification.The prepared photoelectrochemical immunosensor not only has high sensitivity and high specificity,but also shows good repeatability and stability.Since the specific recognition mechanism between antigen and antibody is universal,the proposed photoelectrochemical immunoassay can be used to detect various important biomarkers.4.Reduced graphene oxide@ZIF-8(rGO@ZIF-8)derived from zinc hydroxide nitrate for electrochemical oxidation of dopamine.Electrochemical methods still have unique advantages in detecting small biological molecules such as dopamine.With the rapid development of sensitive materials,the performance of sensors is continuously improved.In recent years,ZIF-8 has received extensive attention in the field of electrochemical sensing due to its excellent structural properties.Meanwhile,some methods have been proposed to obtain ZIF-8 in a fast and low energy way.Here,we obtain ZIF-8 that coverted from Zn-HDS owing to its ion-exchange characteristics.Subsequently,the three-dimensional structure of rGO was combined with ZIF-8 to prepare an electrochemical sensor that analyze oxidation process of dopamine and realize sensitive detection of dopamine.