Synthesis And Analytical Application Of Natural Silk Fibroin-protected Metal Nanoclusters

Metal nanoclusters(MNCs)as a new type of nano-material possess excellent properties such as simple synthetic method,strong light stability,low toxicity,lively chemical properties and high luminous efficiency.As a kind of high performance fluorescent probes,is widely used in chemical,biological sensing and cellular imaging.In this thesis,natural silk fibroin as ligand was used for synthesis of various metal nanoclusters,for example,gold nanoclusters(Au NCs),silver nanoparticles(AgNPs)and copper nanoclusters(CuNCs).And based on the quenching of fluorescence intensity,several detection methods for the detection of organics,ions and pH sensing were developed.Chapter 1: We summarized the research progress on properties,synthesis and applications of MNCs.And we proposed the related research content on this basis.Chapter 2: Silk fibroin(SF)capped gold nanoclusters(SF@AuNCs)were prepared by “one-pot” method in aqueous solution.And high selectively and sensitively for determination of glutaraldehyde had been established(GA)based on the fluorescent SF@AuNCs.The as-prepared SF@Au NCs was effectively quenched by GA,but the other organics showed almost no effects.Related mechanism in the process of experiment was studied in detail.In addition,our proposed method was successfully applied to the determination of GA in the actual water samples,and built a good sensing platform.Chapter 3: In the present study,a simple,green and one-step synthesis approach in aqueous solution was reported for the preparation of the natural silk fibroin(SF)protected silver nanoparticles(SF@AgNPs).The synthetic method was simple and modest,without using any additional reducing agents in synthetic process.Based on the fluorescence quenching mechanism,SF@AgNPs could be used as a novel fluorescent probe for detecting biothiols such as cysteine(Cys),homocysteine(Hcy)and glutathione(GSH).,which may be due to the affinity between thiols and silver.Interestingly,the strong fluorescence of SF@AgNPs was quenched upon the addition of Cu2+ and could then be restored in the presence of PPi.So,pyrophosphate ion(P2O74-,PPi)could be detected by “on-off-on” mechanism.Based on the fluorescence analysis of SF@AgNPs,the probe had been demonstrated by detecting PPi and biothiols in human urine sample.Chapter 4: A one-pot synthesis of natural silk fibroin(SF)-protected fluorescent copper nanoclusters(CuNCs)was homodisperse,it exhibited a fluorescence excitation at 326 nm with blue fluorescence and a fluorescence emission at 420 nm with highly stable properties.The fluorescent SF@CuNCs for reversible pH sensors had been designed based on the distinctly fluorescence enhancing of CuNCs.Meanwhile,the fluorescence intensity of the CuNCs showed a linear relation over the pH ranges of 6.05-10.05 and increased by around 8-fold approximately at high pH values compare with a low pH of 6.108.In addition,the pH sensor was sensitive to different buffer solutions,and also presented a good linear relationship in different buffer solutions.The proposed method was successfully used to detect the pH of real water samples,thereby indicating its potential practical application.Chapter 5: We summarized the research results on metal nanoclusters(MNCs)as a fluorescence probe for applications,and the future research was predicted.