Preparation And Analytical Application Of Fluorescent Silver Nanoclusters

Metal nanoclusters have become more and more popular sensor probes due to their good solubility,biocompatibility,size dependence and catalytic properties.In this paper,silver nanoclusters were synthesized using ammonium sulfate hydrochloride,dopamine,or methionine as ligands,and their properties were characterized by fluorescence spectroscopy,infrared,ultraviolet,XPS and TEM.Based on the change of the fluorescence intensity of nanoclusters,the system for detecting small molecules was established and its mechanism was explored.Chapter 1:We described the properties,synthesis and application of MNCs.On the basis of reading a lot of literature,the research topic of this paper were designed.Chapter 2:A ratiometric fluorescent platform for highly sensitive and selective detection of Oxytetracycline（OTC）was reported using thiamine（VB₁）capped silver nanoclusters（VB₁@AgNCs）as probes.In the presence of OTC,the blue emission of AgNCs was dramatically quenched at 460 nm and a new green emission,appeared and enhanced at520 nm by OTC.Thus,the trail of OTC can be detected by AgNCs based on ratio between the two fluorescent intensities(F₅₂₀/F₄₆₀).The ratiometric F₅₂₀/F₄₆₀ displayed a linear response to OTC concentrations in the range of 0.01μM to 140.0μM with a detection limit of 50.0 nM（S/N=3）.Furthermore,the proposed ratiometric probe was successfully applied in real samples,thereby indicating the probe could monitor OTC in real samples.Chapter 3:Preparation of water-soluble silver nanoclusters（DA@AgNCs）using dopamine（DA）as a template and sodium borohydride as a reducing agent.The research results showed that ethanol solvent can significantly enhance the fluorescence intensity of silver nanoclusters;therefore,ethanol is used as a solvent instead of water to synthesize dopamine-protected silver nanoclusters（DA@AgNCs）with high luminous efficiency.The fluorescence intensity of prepared nanocluster was gradually quenched with increasing the concentration of VB₁₂,is specific to The fluorescence enhancement and quenching mechanism of DA@AgNCs induced by ethanol and VB₁₂was explored.Moreover,a fluorescence detection method for VB₁₂ was established with a linear range of 5.0～80.0μM.The fluorescent probe has good sensitivity and selectivity to VB₁₂,indicating that this method has broad application prospects in the detection of VB₁₂.Chapter 4:we report a novel approach for the synthesis of green emitting silver nanoclusters（AgNCs）using L-methionine as stabilizing agent.The results showed that the synthesized Met@AgNCs with a fluorescence quantum yield of 0.6%.The fluorescence intensity of Met@AgNCs could be efficiently quenched by curcumin（Cur）.The quenching mechanisms were attributed to inner filter effect.The developed sensor exhibited a high sensitivity and selectivity towards Cur in a wide linear range from 2.0-22.0μM and 24.0-40.0μM with a detection limit as low as 200 nM.Moreover,the practice ability of the developed Cur sensor for real sample assay was validated with satisfactory recoveries,indicating this sensing platform with great potential in detecting the content of curcumin in real samples.Chapter 5:We summarized the use of silver nanoclusters synthesized with different ligands as fluorescence probes for detection of small molecules,and the future research work was prospected.