Preparation And Application Of Bismuth Vanadate Based Photoelectric Chemical Sensor

In recent decades,with the accelerating degree of industrialization in the world,the emergence of various diseases and the aggravation of environmental pollution follow.Therefore,more portable,faster and more sensitive detection methods are required.Emerging photoelectrochemistry（PEC）technology innovatively combines light response with electrochemical analysis,and opens up a new way for chemical and biological monitoring analysis.By using light and photocurrent as excitation source and identification signal respectively,the photoelectric sensor can reduce background noise and achieve higher sensitivity than traditional technology.BiVO₄ has good visible light response（520 nm）,suitable band gap（2.4 eV）and good visible light stability.It is widely used in the degradation of environmental pollutants and photoelectrolysis of water,and is considered as a promising photocatalytic semiconductor material.Meanwhile,it has also attracted more and more attention in the fields of PEC sensing and biosensor.BiOI film was electrodeposited deposited on fluorine doped tin oxide（FTO）,then it was transformed into a nanoporous BiVO₄ film by annealing at 420℃.The BiVO₄/FTO electrode is used as photoelectrochemical（PEC）sensor to detect ascorbic acid（AA）for the first time.Under illumination of low power 20 W LED lamp,the current density of the sensor increases with the increase of AA concentration.The proposed PEC sensor exhibited a sensitive detection for AA in a wide range from 5 μM to 300 μM with a low detection limit of 1 μM（S/N=3）and sensitivity of 293 μA mM-1 cm-2.A portable AA detection device was constructed with a 20W LED lamp as the light source,BiVO₄/FTO electrode as an anode,Pt as a cathode,and ammeter as a photoelectric signal receiver.The concentration of AA detected by this device is close to that measured by the electrochemical workstation（RSD<10%）,which makes the sensor practical and portable.In order to improve the efficiency of photoelectron-hole separation,Polyaniline（PANI）and CdS were deposited on the surface of BiVO₄/FTO electrode by cyclic voltammetry because of the narrow band gap energy of pure BiVO₄,which resulted in the rapid recombination of photoinduced carriers.Glutathione（GSH）was analyzed and studied.The amount of PANI and CdS deposition on the surface of BiV04 electrode and the test voltage were optimized to obtain the best conditions for detecting GSH.GSH solutions of different concentrations were measured under the optimal detection conditions,and the results showed that:The linear detection range of GSH was 0.1-20μM,the linear regression equation was ΔI=0.12+7.43 cGSH（μM）,the correlation coefficient was 0.997,and the sensitivity was 639 μA mM cm-2 under the excitation of the external bias voltage of 0.1V and the LED light source of 20 W.The detection limit for glutathione was as low as 40 nM（S/N=3）,and the selective reproducibility and stability of the sensor were also satisfactory.