Preparation And Application Of Silver Nanoclusters Based On Polymer Template With Multi-chelating Site

Ag nanoclusters(Ag NCs)possess fantastic advantages,such as excellent optical stability,low toxicity,great compatibility,easy to synthesis,readily functionalized and large Stoke shift,which have made the nanoclusters widely used to construct fluorescence probes of detection.In this paper,different water-soluble fluorescent silver nanoclusters(Ag NCs)were prepared using different polymers with multiple chelating sites(acrylic copolymers and polyglutamic acid)as templates.Based on these Ag NCs as fluorescence probes,two different fluorescence sensing systems were constructed for the detection of heavy metal ions copper ions(II)(Cu²⁺)and chromium ions(III)(Cr³⁺)respectively.The main research contents are as follow:(1)Preparation of silver nanoclusters protected by poly(methacrylic acid-co-itaconic)and their application in detection of copper ions(Cu²⁺)Poly(methacrylic acid-co-itaconic)-protected silver nanoclusters(P(MAA-co-IA)-Ag NCs)were prepared by means of UV reduction method,the characterization of their morphology and structure was studied by a series of technologies(including TEM,FTIR,XRD,XPS and TGA).The results indicated that P(MAA-co-IA)-Ag NCs are spherical with good dispersion and size of 2.1 nm.The ratio of Ag(0)to Ag(I)content in P(MAA-co-IA)-Ag NCs was about 13/7.The fluorescence intensity of P(MAA-co-IA)-Ag NCs solution with red-emitting emissions could remain unchanged stored at 4°for four months in the absence of N₂ protection.An analytical method for detecting Cu²⁺was established based on the sensitive fluorescence quenching effect of Cu²⁺on the Ag NCs solution.The method can be used to quantitatively analyze Cu²⁺in the concentration range from 0 to10?M with a limit of detection(LOD)of 6.36 n M.The recovery rate was 97.10?101.20%when the detecting the Cu²⁺in tap water with a relative standard deviations(RSDs)of 1.36?3.21%,which indicated the prepared silver nanoclusters can be used to detect the content of Cu²⁺in real water samples.(2)Preparation of silver nanoclusters protected by polyglutamic acid(PGA)and their application in detection of chromium ions(Cr³⁺)Polyglutamic acid-protected silver nanoclusters(PGA-Ag NCs)with yellow-green fluorescence were prepared by UV reduction method at room temperature and characterized by TEM,XRD,XPS and TGA.The results indicated that PGA-Ag NCs had good dispersibility and the particle size was less than 3.0 nm.The binding energy of Ag(3d_3/2)and Ag(3d_5/2)were close to Ag(0),and the content of Ag is about 56%.Based on fluorescence quenching of Cr³⁺to PGA-Ag NCs solution,a fluorescence probe for the detection of Cr³⁺was constructed.The experimental results showed that the probe could be used for the quantitative detection of Cr³⁺under the concentration range of 0-100?M,with a LOD of 0.38?M.The PGA-Ag NCs solution had good stability and reproducibility for the detection of Cr³⁺.The recovery rate was97.39?102.57%when detecting the Cr³⁺in river water with a RSD of 2.10?4.19%%,which indicated the prepared silver nanoclusters can be to analyze the content of Cr³⁺content in real water samples.