Fabrication Of Semiconductor Nanocomposite Electrode And Its Applications In Electrochemical Sensing

Signal molecules are essential vital active substances in organisms,and the study of their structure and function is directly related to the development of humans in the fields of early diagnosis,clinical treatment and drug screening.In recent years,the biosensor had become the focus of attention because of its advantages of simplicity and convenience.With the continuous demand for sensor performance and the need for simple equipment,nanomaterials especially semiconductor metal oxide with unique physical or chemical properties were widely applied.Meanwhile,by virtue of the advantages of cheap,easy folding and portable,paper-based material was modified and functionalized to build the portable sensor,which could realize rapid on-site monitoring in the field of medicine,food and environmental protection.In this paper,based on the excellent optical and electrical properties of nanomaterials,several kinds of semiconductor nanocomposite electrodes had been designed and prepared,and three novel photoelectrochemical?PEC?biosensors were constructed by means of the photoelectrochemistry mechanism,achieveing the rapid monitoring of tumor prediction,diagnosis and treatment.The research work has been carried out as follows:?1?Based on the foldable and porous structure of the paper material,a controllable fluid separator with hydrophilic and hydrophobic characteristics was designed as a biomolecule transmission channel.By growing copper oxide nanoflower/graphene complex as an electrode in the working zone of the paper-based PEC sensor and designing sequential reactions of biomolecules in the reaction zone,the spatial steric hindrance caused by multiple modifications on the photosensitive material was avoided,thus achieving cascade amplification of the output signal and obtaining a high photocurrent response.?2?The high-performance Ni:FeOOH/BiVO₄ semiconductor nanocomposite was modified on fluorine-doped tin oxide glass?FTO?by hydrothermal method as a photoanode and combined with the prussian blue?PB?cathode material to construct the photoelectrochemical/simultaneous visual immunosensor.The photocurrent of the sensor was greatly improved by the excellent electron transfer efficiency of the photosensitive material,and output signal was obtained instantly through the digital multimeter.Meanwhile,the cathode material PB accepted the electron to convert to prussian white?PW?,which could return to the initial PB state when connected with the laccase biocathode.This electrochromic reaction provided a more intuitive visual monitoring result.?3?The nanoplate-like WO₃/Fe₂O₃ heterojunction electrode materials was prepared on FTO.Due to its special array structure,the nanocomposite had more excellent photoelectrochemical activity and current response.Based on high biocompatibility characteristic of paper fibre,a dual-functional paper-based biocathode was designed and connected with WO₃/Fe₂O₃ semiconductor nanocomposite electrode to successfully construct the dual-mode aptasensor.By means of the specific recognition effect of DNA on the reaction zone and the colorimetric reaction of 3,3',5,5'-tetramethylbenzidine on the reaction zone,the signal output of dual targets was realized.