Applications On The Bismuth-Based Nanomaterials In Electrochemical And Photoelectrochemical Analysis

Chemical sensor is one of the main tools to detect pollutants in the environment at present.They are chemical functional tools,which are made of chemical active materials and combined with appropriate signal converters.Electrochemical sensors and photoelectrochemical sensors have become the representatives of important chemical sensors due to their many advantages.A variety of high-performance nanomaterials have attracted extensive attention in the field of electrochemical sensors and photoelectrochemical sensors due to their outstanding physical and chemical properties for more than a decade.Among them,bismuth（Bi）based nanomaterials have become active materials of electrodes with potential application in the field of electrochemical/photoelectrochemical seneors due to their excellent conductivity and good photoactivity.This thesis mainly focuses on establishing electrochemical and photoelectrochemical（PEC）analysis platform based on Bi-based nanomaterials.The main contents include the establishment of a novel electrochemical analysis platform with bismuth-based nanomaterials to realize the highly sensitive detection of nitrite;additionally,bismuth-based semiconductor heterojunction serve as a photoelectrode to construct an efficient photoelectrochemical sensor for the analysis of azomycin;furthermore,Ag plasma nanoparticle is used as electronic medium to prepare Z-scheme heterojunction,which is developed to PEC analysis platform.The details are as follows:（1）A disposable electrochemical sensor based on Bi₂Se₃/MWNTs-COOH nanocomposite is designed for detecting nitrite.The Bi₂Se₃/MWNTs-COOH nanocomposite is synthesized via one-step hydrothermal method with the oxygen connection between Bi₂Se₃/MWNTs-COOH.Compared to pure Bi₂Se₃,the Bi₂Se₃/MWNTs-COOH nanocomposite possessed effective electron transfer and high electrochemical active surface area,resulting in advanced electrochemical performance.The disposable and portable electrochemical sensor is designed based on the Bi₂Se₃/MWNTs-COOH nanocomposite which presents a strong linear relationship,a wide range（0.01 m M～500μM,0.50 m M～7.0 m M）,a low detection limit（LOD,0.002μM）,good stability and high sensitivity(223μA m M^-1 cm^-2).（2）The previous chapter mainly explored the electrochemical properties of Bi-based nanomaterials.Due to the excellent photochemical activity of Bi-based nanomaterials,the photochemical properties of Bi-based nanomaterials is studied in this chapter.Three-dimensional（3D）heterojunction composed of Bi₂S₃ and Bi₂WO₆ is proposed for azomycin detection via PEC technology.The Bi₂S₃/Bi₂WO₆ photoelectrode is prepared by a facile hydrothermal method,in which Bi₂WO₆ layer can serve as multichannel pathways,sharing and facilitating electron transport from Bi₂WO₆ to Bi₂S₃.Additionally,the result of electrochemical impedance spectras suggests that Bi₂S₃/Bi₂WO₆ heterojunction has not only the faster separation rate of charge carrers but also transfer rate of electrons.Under the optimal experimental conditions,Bi₂S₃/Bi₂WO₆ heterojunction exhibits remarkable PEC activities for azomycin,with a LOD of 0.024μM as well as wider linear interval of 0.1μM to 500μM.Moreover,the 3D Bi₂S₃/Bi₂WO₆ heterojunctions also display very good stability and are reliable to apply for azomycin in the real water.（3）In order to further improve the separation of photogenerated electron hole pairs and redox capability of Bi heterojunction,Z-scheme heterojunction with a unique charge-carrier migration path is designed in this chapter.A visible-light-driven Bi OBr/Ag/Ag Br Z-scheme heterojunction is designed for ultrasensitive detection of nitrite.Bi OBr/Ag/Ag Br heterojunction is fabricated by in situ ion exchange reaction between Bi OBr and Ag NO₃ followed by light reduction.The Bi OBr/Ag/Ag Br could enhance PEC performances due to efficient light harvesting and fast charge transfer.Then,a photoelectrochemical sensor based on Bi OBr/Ag/Ag Br Z heterostructure is constructed for detecting nitrite.Under the optimal conditions,the dual-photosystem sensing platform exhibits the LOD of 8.7×10^-7 M.Furthermore,good reproducibility is realized in real water sample.Importantly,the Bi-based Z-scheme heterojunction strategy provides a referenced analysis platform for detecting nitrite.