| In this paper, we use three different nanomaterials to build three spectral sensors. Nanomaterials were used as colorimetric or fluorescent probes, combined with enzymatic method, UV-visible spectroscopy, and fluorescence quenching method for quantitative analysis of some environmentally hazardous substances(mercury ions, organophosphorus pesticides). These methods are simple, rapid, high sensitive, providing some new ideas for the quantitative detection of hazardous substances.Concrete contents are summarized below:Chapter 1: It described the development of silver nanoparticles, graphene quantum dots, gold clusters, iron oxide nanoparticles, and their common synthetic methods and application researches in the field of analytical chemistry; besides, the theoretical knowledge of ultraviolet-visble spectrum, fluorescence spectroscopy and some of the common means of characterization are also introduced; finally, the outlook of trends of nanomaterials binding with molecule spectroscopy in the field of analysis was presented.Chapter 2: The citrate-capped silver nanoparticles was protected by the reduction of silver nitrate by sodium borohydride. UV-vis spectroscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy were used for the characterization of the morphology of the as-prepared silver nanoparticles and their variation before and after reaction.(1) Acetylcholinesterase can catalyze the substrate acetylthiocholine to form thiocholine, which can induce the aggregation of silver nanoparticles;(2) the bright yellow color of dispersed silver nanoparticles will change to pink when aggregated;(3) organophosphorus or carbamate pesticides can make acetylcholinesterase denatured and inactivated, and then inhibit the variation. Thus the analysis of organophosphorus or carbamate pesticides can be realized based on the mechanism.Chapter 3: Graphene quantum dots were prepared by pyrolysis of citric acid at 200 °C, which can emit blue fluorescence at 450 nm.(1) Positively charged mercury ions will adsorb on the surface of negatively charged graphene quantum dots through electrostatic interaction, which will induce the aggregation of GQDs and fluorescence quenching through charge transfer;(2) In addition of cysteine, heavy metal thiol bond between cysteine and mercury ions can formed, and consequently, the mercury ions tend to separate from the GQDs Thus, the fluorescence of GQDs will be restored and enhanced. The two reaction processes discussed above provide a successful basis for a dual-sensor for the analysis of mercury ions and cysteine.Chapter 4: A magnetic and fluorescent nano-composite was prepared. It comprised of a core of Fe3O4 nanoparticles(NPs), a silica shell and satellitic Au nano-clusters(Au NCs) capped with bovine serum albumin(BSA). 6-MP will adsorb on the BSA–Au NCs, which removed the protection effect of the BSA. Without this protective effect of the BSA, the detached Au NCs coated with thiols, could aggregate. This would lead to the formation of NPs and in addition, the previously existing cross-linked structure was broken and fluorescence was quenched. According to this principle, a fluorescent sensors for 6-mercaptopurine can be constructed.The highlights can be summarized as: 1. Three different nanomaterials were used for quantitative analysis of some environmentally hazardous substances and medicine and acquired satisfactory results with high sensitivity and good selectivity. 2. In comparison with some traditional methods, these methods possess simple operation, rapid detection and convenient practical application. 3. We constructed a dual-sensor for simultaneous detection of Hg2+ and Cys by fluorescence quenching and enhancement. 4. A novel, magnetic and fluorescent composite of Fe3O4 NPs and Au NCs was prepared and characterized. Key Word: Graphene quantum dots; Magnetic nano-composite; Silver nanoparticles; Quantitative detection;... |
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