Synthesis And Characterization Of Gold Nanoclusters And Their Applications In Environment And Biochemical Analysis

Gold nanoclusters （AuNCs）, composed of a few to a hundred atoms, their sizes arecomparable to the Fermi wavelength of electons, resulting in molecule-like propertiesincluding discrete electronic ststes and size-dependent fluorescence. They have perfectapplication perspectives in nonatechnology field for their ultrasmall size, goodbiocompatibility and excellent photostability and so on. In this dissertation, water-solubleAuNCs including25atoms have been synthesized using bovine serum albumin （BSA） asmacromolecules template. Some novel fluorescence sensors have been designed by means ofexploring the correlations between fluorescence signal of AuNCs with biomolecules as wellas inorganic ions, and the sensing mechanisms and applications have been studied further.（1） A novel fluorometry for the determination of trace cysteine （Cys） has been proposedbase on the fact that the fluorescence intensity of AuNCs could be enhanced throughdecreasing the surface defects of AuNCs modified with Cys. This method with wide linearrange from2.0to800.0nmol mL^-1, high sensitivity (detection limit （LD） was1.2nmol mL^-1)and good selectivity has been utilized to determine Cys content in real samples, and theresults were concordant with those determined by electrochemical biosensor. Simultaneously,the morphological characterizations of AuNCs and AuNCs-Cys were characterized byfourier-transform infrared spectroscopy （FTIR） and high resolution transmission electronmicroscopy （HRTEM）, and the mechanism of the proposed assay for the determination ofCys has been discussed also, promoting the development of AuNCs in biological sciences.（2） The luminescence of BSA-AuNCs quenched when Cu²⁺chelated with glycine in BSAchain and generated BSA-AuNCs-Cu²⁺, while we found that the luminescence ofBSA-AuNCs could restore in the presence of pyrophosphate ion (P₂O₇^4-, PPi). Bearing this inmind, herein we presented a novel BSA-AuNCs-Cu²⁺fluorescent sensor for PPidetermination. This fluorescent sensor possessed wide linear range （0.16-78.1μM） and highsensitivity （LD was0.083μM）, which could also determine PPi in effluent of copper platingwith the results accord with those determined by absorptiometry. Moreover, the PPi determination mechanism was discussed by BSA-AuNCs-Cu²⁺fluorescence sensor.（3） A new AuNCs fluorescence sensor for the determination of S^2- has been designed basedon the sharply quenching of AuNCs fluorescence resulting from the forming Au₂S on thesurface of AuNCs by the reacting between Au+with S^2-. The proposal sensor can be used tovisibly determine the content of S^2- selectively and sensitively （LD was0.029μM） in thepresence of most of high concentration of anions in water sample. And the results agreed wellwith those obtained by Electrochemical Methods, revealing the characteristics ofenvironment-friendly, simplisity, fast response and practicality. Meanwhile, themorphological characterization changes of AuNCs were measured using HRTEM.Furthermore, the mechanism of the proposed assay for the determination of S^2- has beendiscussed.