Preparation And Application Of Silver Nanocluster-based Fluorescent Composites

Nanoscale Science and Technology is one of the key components of modern science,and also an interdisciplinary frontier research field.With the development of society,nanotechnology is put to wide use in many fields such as imaging,sensing,medical diagnosis and treatment,energy and so on.For the past few years,noble metal nanoclusters,as a star member of nanomaterials,have attracted more and more attention in their synthesis and application.As a new category of luminescent nanomaterials,noble metal nanoclusters have the advantage of low toxicity,high fluorescence stability,large stokes shift and tunable emission,which makes it an ideal fluorescent indicator.And among them,the silver nanoclusters show different physical and chemical properties due to their ultra-small size and novel structure,so in this paper,we have carried out the following research contents around the preparation and application of silver nanocluster-based fluorescent composites,the main research is as follows:Firstly,silver nanoclusters in aqueous phase were prepared in one step by microwaveassisted synthesis using branched polyethylenimine as ligand and ascorbic acid as reducing agent.The synthesis process is quite simple,and have the benefit of short preparation time,low cost and excellent repeatability.Silver nanoclusters(PEI-Ag NCs)with uniform size and good stability were obtained through this,and the silver nanoclusters can exhibit green fluorescence through certain excitation.Then we found that the silver nanoclusters can be quenched by copper ions,and within a certain concentration range,the fluorescence intensity of silver nanoclusters correlated linearly with the concentration of copper ions,the LOD is4.5 ?M.Based on this phenomenon,a fluorescent probe for rapid detection of copper ions was developed,and this system show good performance in application.In addition,fluorescent probe with single emission has the deficiency of large error,and it's vulnerable to environmental effects,so we synthesized a kind of dual-emission fluorescent probe based on silver nanoclusters.In this part,we selected histidine and dihydrogen lipoic acid as ligand,synthesized two silver nanoclusters with different fluorescence emission,and the fluorescent nanocomposites with dual-emission were formed by electrostatically assemble(His-Ag NCs@DHLA-Ag NCs).Then we confirmed that one emission peak of the nanocomposites could be selectively quenched by copper ions while another is stable,and with the increase of copper ion concentration,the color of the dualemission fluorescent nanocomposites gradually changed from pink to cyan under UV light.This ratiometric fluorescent sensor has a lower limit of detection(0.04 ppm)and better antiinterference capability,it was successfully applied to the analysis of some water samples with satisfactory results.Finally,on account of the ratiometric fluorescent probe is unfavorable for carrying and preservation,taking polyvinylpyrrolidone and agarose as raw material,we synthesized a kind of polymer film,this polymer film material is almost transparent and has good biocompatibility,and then the ratiometric fluorescent sensor was successfully loaded onto it,consequently enlarges the range of application.