Fabrication Of AIn₂S₄（A=Zn,Cd）/Vacancy-MoS₂ Nanocomposites Based Disposable Photoelectrochemical Aptasensor For Mycotoxins Detection

Aflatoxin B1,ochratoxin A,fumonisin B1 and zearalenone are highly carcinogenic,teratogenic,hepatotoxic or nephrotoxic.Therefore,the development of new rapid and sensitive detection methods is an important way to ensure the quality and safety of food or feed.Photoelectrochemistry（PEC）analysis has great potential in rapid,sensitive and low-cost detection,but it still faces challenges in selectivity,sensitivity,stability and simultaneous detection.In this paper,designed indium tin oxide（ITO）was selected as the working electrode to construct PEC aptasensors based on ZnIn₂S₄/V-MoS₂ or CdIn₂S₄/V-MoS₂ nanocomposites for mycotoxins detection.In addition,electrochemical impedance method（EIS）is an intuitive method to show the change of electron transfer resistance at the electrode interface,especially suitable for label-free detection.Hence,in-situ growth of Aunanoparticles（AuNPs）on designed four-channel chip to construct an electrochemical apatsensor for simultaneous detection of four mycotoxins.The specific research contents are as follows:1.The V-MoS₂ nanosheets were prepared by ultrasonic treatment and H₂O₂ etching.ZnIn₂S₄/V-MoS₂ nanocomposite was prepared by solvothermal method after V-MoS₂ and other precursors were dispersed in ethylene glycol.PEC study showed that the photocurrent intensity of V-MoS₂ nanosheets（etched for 5 min）was 48.0 n A,6.1 times that of MoS₂ nanosheets.The photocurrent intensity of ZnIn₂S₄/V-MoS₂ nanocomposite was 5.6μA,3.2 times that of ZnIn₂S₄/MoS₂ and 5.6 times that of ZnIn₂S₄.The results showed that the introduction of S vacancy can effectively improve the PEC activity of MoS₂ nanosheet and ZnIn₂S₄/MoS₂,and the prepared nanocomposite with type-Ⅱ heterojunction can effectively inhibit the recombination of photogenerated electron hole pairs and improve the intensity and stability of PEC.Using ZnIn₂S₄/V-MoS₂ nanocomposite as electrode sensitive material and AFB1 aptamer as molecular recognition element,a PEC aptasensor was successfully constructed for AFB1 detection.The proposed PEC aptasensor could detect AFB1 as low as 0.016 ng/mL in corn meal samples with a detection range of 0.05-50 ng/mL.2.The chip with three working electrodes was designed to fabricate three-channel aptasensor for simultaneous detection of AFB1,OTA and ZEN.Then through ultrasonic treatment and H₂O₂ etching preparation of V-MoS₂,join other precursor and dispersed in water,CdIn₂S₄/V-MoS₂ nanocomposite was prepared by hydrothermal method.The photocurrent intensity of CdIn₂S₄/V-MoS₂ was 10.02μA,1.53 times that of CdIn₂S₄.The constructed nanocomposites with type-Ⅱ heterojunction can effectively improved the photoelectrical activity and stability of CdIn₂S₄.Using CdIn₂S₄/V-MoS₂ nanocomposites as electrode sensitive materials,the aptamers without modification by functional groups as molecular recognition element were directly combined with flower-like CdIn₂S₄/V-MoS₂ through the van der Waals force adsorption,and the three-channel aptasensor was successfully constructed.The detection range of AFB1,OTA and ZEN were 0.05-50,0.05-250 and 0.1-250 ng/mL,respectively,and the limits of detection were 0.018,0.015 and 0.020 ng/mL,respectively.3.ITO chip with four working electrodes was prepared based on simple laser etching and used as a four-channel electrochemical aptasensor to realize the simultaneous detection of four typical mycotoxins without labeling.Firstly,AuNPs were grew in situ on bare four working electrodes（ITO-AuNPs）.Secondly,the different thiol-modified aptamers were self-assembled to four different working electrodes（ITO-AuNPs-Apt）via Au-S bond as molecular recognition elements,respectively.Finally,6-mercaptohexanol（MCH）was used to block the excess active sites on working electrodes to reduce interference.When the target exists,it will be captured by the corresponding aptamers on the four-channel aptasensor,resulting in changes in the EIS signal.The detection linear ranges of FB1,AFB1,ZEN and OTA were 5-1000 ng/mL,10-250 ng/mL,10-1250 ng/mL,10-1500 ng/mL,respectively.The limits of detection were 2.47 ng/mL,3.19ng/mL,5.38 ng/mL,4.87 ng/mL（S/N=3）,respectively.