Fluorescence Analysis Of Dopamine And Tannic Acid By Molybdenum-based Nanomaterials

The problems of food safety have became more and more serious.However,the traditional analysis can not meet the requirement of efficient,reliable and fast detection of food safety factors.Therefore,numerous simple,fast and versatile analytical technologies have been developed.Thereinto,the rapid development of nanotechnology has provided a novel avenue for the rapid food analysis,and the quantum dots with unique fluorescence properties have been widely applied in the food analysis.Compared with other transitional metals,molybdenum-based nanomaterials possess the properties of non-toxic and high activity,which can be also regulated by controlling their morphology and size,and utilized as promising fluorescent sensors.Therefore,this work realizes sensitive and rapid determination of dopamine and tannic acid in food with molybdenum-based quantum dots as fluoresenct nanoprobes.The main studies and results of this work are as follows:?1?Fluorometric determination of dopamine by molybdenum disulfide quantum dots?MoS₂ QDs?A selective fluorometric analysis of dopamine?DA?was developed based on molybdenum disulfide quantum dots,which was synthesized via an ammonium hydroxide etching method with bulk MoS₂ as raw material.The structure and morphology of MoS₂QDs were tested by various physical characterization methods.The optical properties of MoS₂ QDs and the mechanism of detecting dopamine were investigated.The sensing performance,selectivity and applications in real samples were also evaluated.These results show that the MoS₂ QDs can be facilely synthesized via the ammonium hydroxide etching method within only 2 minutes.The formations of organic molybdate complexes and dopamine-quinone result in strong quenching of the MoS₂ QDs fluorescence.Under the optimum conditions,the sensor shows a wider linear detection range of 0.1 to 100?M,a low detection limit of 10 nM,as well as high feasibility of testing dopamine in real samples.?2?Fluorometric determination of tannic acid by molybdenum oxide quantum dots(MoO_3-x QDs)We constructed a rapid and selective fluorescent assay to realize the detection of tannic acid?TA?based on the molybdenum oxide quantum dots,which was synthesized via a hydrothermal method with molybdenum powder as the raw material.The characterization and optical properties of the MoO_3-x QDs were investigated.Moreover,the feasibility and detection mechanism were also explored.The sensitivity,selectivity and practical application of this sensor were also evaluated.This assay was successfully applied to detect TA in 1 min.Taking advantage of fluorescence change of the MoO_3-x QDs,TA can be linearly detected in the range of 0.1 to 10?M with a detection limit of 30 nM.This sensor not only shows rapid response,high sensitivity and excellent selectivity toward the detection of TA,but also shows satisfied recovery and good reproducibility in the determination of TA in food samples.