Research On Detection Of Noxious Substance Based On Molybdenum Disulfide Quantum Dots Fluorescence Sensor

Nowadays,food and drinking water safety problem has attracted much attention,residues of toxic and harmful substances are the main culprits that threaten food safety,It is of great significance to establish a fast,sensitive and economical detection method.Hydrogen peroxide,catechol,and methyl parathion are widely found in food and drinking water because they are important chemicals in daily life.This paper established three different fluorescence sensors which were based on molybdenum disulfide quantum dots to realize the sensitively and quickly detection of the chemicals.The main work is as follows:(1).Molybdenum disulfide quantum dots with fluorescence properties were synthesized through one-step hydrothermal with sodium molybdate as molybdenum source and glutathione as a sulfur source.The structure,monography,function group and chemical element were charicteristic by transmission electron microscopy,X-ray photoelectron spectroscopy and fourier infrared spectroscopy.a new fluorescence sensor was formed through the mix of molybdenum disulfide quantum dots and manganese dioxide nanosheets.Due to the internal filtering effect and static quenching effect,the fluorescence of the fluorescent sensor is quenched.The addition of hydrogen peroxide can reduce manganese dioxide to divalent manganese ions and release the fluorescence of molybdenum disulfide quantum dots.The fluorescence sensor possesses extremely high selective,the detection range of hydrogen peroxide is 0.1 ?M-150.0 ?M,the detection limit is 0.033 ?M.It was successfully used to detect hydrogen peroxide in milk samples(2).The benzene boric acid functional group modified to the previously synthesized molybdenum disulfide quantum dots.The hydroxyl functional group on the surface of the synthesized molybdenum disulfide quantum dots was amidation with the 3-amino-benzyl boric acid functional group and the benzene boric acid functional group was successfully connected to the surface of the molybdenum disulfide quantum dot.The functionalized molybdenum disulfide quantum dots have adjacent hydroxyl functionalgroups on the surface which can react with the adjacent hydroxyl of catechol.Because of the internal filtering effect and static quenching effect,the fluorescence of phenylboronic acid-modified molybdenum disulfide quantum dots was quenched.This fluorescence sensor has specific detection for catechol,and the detection range is 0.10 ?M-200.0 ?M,the detection limit is as low as 0.025 ?M.Moreover,this fluorescence sensor was successfully applied in drinking water for catechol detection,(3).Hydroxypropyl-?-cyclodextrin was added to the benzene boric acid-modified molybdenum disulfide which was prepared in the previous experiment ? Substitution reaction occurred between the two o-hydroxyl groups of hydroxypropyl-?-cyclodextrin and the o-hydroxyl groups of the benzene boric acid-modified molybdenum disulfide quantum dots to form ?-cyclodextrin modified molybdenum disulfide quantum dots.This quantum dots has a ring cavity of cyclodextrin on the surface which can hold some substances such as p-nitrophenol.After entering the cavity,p-nitrophenol can quench the fluorescence of ?-cyclodextrin modified molybdenum disulfide quantum dots due to the photo-induced electron transfer.Methyl parathion can be hydrolyzed to nitrophenol under alkaline conditions.Based on this,a fluorescence sensor for Methyl parathion was established which was based on ?-cyclodextrin modified molybdenum disulfide quantum dots.This fluorescence sensor detection range of Methyl parathion is0.01 ppm-36 ppm,the detection limit was 3.3 ppb.this fluorescence sensor was successfully applied in apple and cucumber for methyl parathion detection.