Application Of Photoelectrochemical Sensor In Detection Of Microcystins

As a novel kind of detection technology,photoelectrochemistry（PEC）combines photochemistry and electrochemistry,separates the excitation signal and the detection signal,reduces the background noise,and decreases the signal-to-noise ratio,effectively improves the selectivity and stability of the sensor.Self-powered sensor is a kind of sensor that does not need external energy,it is simpler and more portable and has attracted much attention of researchers in environment,medicine,food,and many other fields.It has been widely used and has broad prospects.In this paper,two-dimensional lamellar materials graphene and titanium carbide（Ti₃C₂ MXene）were combined with metal semiconductor to prepare a series of functional nanomaterials.Aptamers with specific recognition ability were introduced.Based on these,different photoelectrochemistry aptamers were developed for the detection of microcystins in water sample.These methods are simple,rapid and have good selectivity.The details are as follows:1.Photocurrent sensor based on NGH/Fe₂O₃ nanocomposite for the detection of MC-LR:In this work,a novel visible-light-driven self-powered photoelectrochemical（PEC）platform was designed based on 3D N-doped graphene hydrogel/hematite nanocomposites（NGH/Fe₂O₃）via a facile one-pot hydrothermal route.The coupling NGH with Fe₂O₃ could generate Schottky junction,which promoted the separation of charges.Moreover,Mott-Schottky measurements validated that the carrier concentration achieved by NGH/Fe₂O₃ was about 3400-times in comparison to that of pure Fe₂O₃,which was beneficial for efficient charge transfer.Owing to the carrier density effect and Schottky junction,the photocurrent of the as-fabricated NGH/Fe₂O₃ nanocomposites displayed 6.9-fold higher than that of pure Fe₂O₃.Based on such excellent Schottky junction,an ultrasensitive visible light-induced self-powered PEC aptasensor was developed with the assistance of Microcystin-LR（MC-LR）aptamer.The as-fabricated PEC aptasensor displayed good analytical performance and the linear detection range was 10^-12 mol/L to 5×10^-9 mol/L with a limit of 2.3×10^-13 mol/L（S/N=3）。2.Photovoltage sensor based on Bi₂S₃/Ti₃C₂ photoanode and CuO photocathode for the detection of MC-RR:In this work,we constructed a self-powered dual-photoelectrode sensor consisted with Bi₂S₃/Ti₃C₂ photoanode and CuO photocathode.Based on the differentiation of the Fermi level between these two photoelectrodes,the sensor did not need any external energy.At the same time,with plasmonic Ti₃C₂,the nanocomposites had SPR effect which could generate hot-electron and accelerated electron transport.With the sulfur defect of Bi₂S₃,the charge carrier lifetime extended,more active sites have created and thus the photoelectric property enhanced.The sensitive detection of MC-RR was realized by further coupling with the MC-RR aptamer.The sensor had a linear range from 10^-16 mol/L to 10^-11mol/L,and had a detection limit of 4.7×10^-17 mol/L（S/N=3）.This work provided a promising strategy for the design of dual-photoelectrode sensing platform with high sensitivity and excellent selectivity.3.Light-driven ratiometric power sensor based on Mo S₂/Ti₃C₂nanocomposite for the detection of MC-RR:In this work,we synthesized Mo S₂/Ti₃C₂ nanocomposite by heat treatment,and constructed a ratiometric power sensor driven by light.Power used as the detection signal,instead of the traditional photocurrent or photovoltage,could enhance the signal and improve the sensitivity.The ratio of detection section（DS）and reference section（RS）was adapted as power signal,to effectively eliminate the influence of light intensity.Further introduced potassium persulfate as an electron acceptor,which was benefit for improving electron transport efficiency,hindering electron-hole recombination,and significantly enhancing the performance of the sensor.Based on this principle,the sensitive detection of MC-RR was realized by coupling the MC-RR aptamer.The prepared sensor had good selectivity and sensitivity,could detect actual samples.It had a linear range from 10^-12 mol/L to 10^-6 mol/L,and the detection limit was 5.6×10^-13 mol/L（S/N=3）.