Studies On The Flourescent Sensors Methods For Determination Of Bromate And Chromate Trace Poisonous Substances In Drinking Water

The water resources have suffered serious pollution with the industry "threewastes" and any discharge of urban living garbage in recent years. However, bromate,hexvalent chromate as cancerogenic substance will cause varying degrees of damageto people’s health. So it is very important to establish rapid and efficient methods forthe determination of trace bromate and chromate ions or other toxic substance inwater.Semiconductor nanocrystals CdTe, gold cluster have many excellent performances,such as their unique optical properties, high luminescence quantum yield, well lightstability and water-solubility, as well as excellent biocompatibility, and widely usedin basic research and applications. In this thesis, CdTe quantum dots and goldnanoclusters were synthesized and used as fluorescent probes to determine bromatedions, chromate ions in water. The main contents are as follows:1、The green synthesis and characterization of CdTe quantum dotsWe have developed a novel, green and aqueous solution synthesis ofTGA-capped CdTe QDs using NaHSO3as reducing agent, tellurium dioxide astellurium source and thioglycollic acid as capping reagent by refluxing in boilingwater at open air. The influence factors including refluxing time, pH, amount of TGAand NaHSO3on the luminescent properties of the obtained CdTe QDs wassystematically investigated, and the optimal conditions were determined. Under theoptimum conditions, the luminescence quantum yield of the QDs is reached70.09%.The properties of the CdTe QDs were characterized by UV/Vis, fluorescence spectrum,FT-IR spectrum and high-resolution transmission electronmicroscopy.2、Determination of bromate ions in drinking water using CdTe quantum dots asfluorescent probesWe have developed a novel method for determining bromate ions in drinkingwater using L-cysteine modified CdTe quantum dots as fluorescent probes, andproposed a new mechanism of fluorescence quenching in the presence of BrO3-.Influencing factors including the size of CdTe QDs, a different modification agent, reaction time and others on the detection of bromate ions were investigated, andthe optimum conditions were determined. Under the optimal conditions, the relativefluorescence intensity of the QDs was linearly proportional to BrO3-anions over aconcentration range from1.0×10-8~1.0×10-4mol·L-1with a correlation coefficientof0.9998and a detection limit of0.4nmol·L-1. The proposed method ccan be appliedto analysis of trace bromate ions in drinking water.3、Ultrosensitive determination of trace bromate ions in drinking water using goldnanoclustersclusters as fluorescent probeWater-soluble gold nanoclustersclusters capped with L-cysteine, which is anon-poisonous and stable performance of light, was prepared and characterized byoptical spectrum analysers. The study found that bromate ions could quench thefluorescence of L-cysteine modifying gold nanoclustersclusters. So a novel methodfor determining bromate ions was established based on the theory of fluorescencequenching. The relative fluorescence intensity of L-cysteine modified goldnanoclustersclusters was linearly proportional to the concentration of bromate ionsfrom1×10-9~1×10-5mol·L-1with a detection limit of0.035nmol·L-1. This fast andsimple method can be applied to determine bromate ions in samples.4、Fast determination of chromium acid radical ion using egg albumen asfluorescence probesA novel method for fast determination of chromium acid radical ion was set upbased on the fluorescence quenched from egg albumen. The influence factors on theanalysis of Cr(VI) anions were investigated, and the optimum conditions for thedetermination of Cr(VI) anions were determined. Under the optimum conditions, therelative fluorescence intensity of the egg albumen was linearly proportional to Cr(VI)anions over a concentration range from1.010-8to1.010-4mol·L-1with a correlationcoefficient of0.9902and a detection limit of5.2nmol·L-1. This is a highly selective,simple and fast method. The proposed method was employed to detect Cr(VI) anionsin water samples with satisfactory.