One-step Reductive Synthesis Of Thiolated Silver Nanoclusters And Its Application In Determination

Noble metal nanoclusters are considered of relatively stable aggregates of a few to hundreds atoms（Pt,Au,Ag,Cu,etc）,which formed by the physical and chemical binding force under the protection of a certain molecular layer.Owing the ultra-small peculiarity with core sizes below 2 nm Noble metal NCs exhibiting distinctively different physical and chemical properties from their larger corresponding nanoparticles（NPs）with core sizes above2 nm.Such intriguing physicochemical properties of metal NCs,not being seen in metal NPs（>2 nm）before,have attracted increasing interest from the research community for both basic and applied studies.In the past decade,significant advances have been made in the field of thiolate capped Ag NCs,including its synthesis,characterization,and biomedical applications.Compared to the synthesis of thiolate capped Au NCs,synthesis of thiolate capped Ag NCs is more challenging because of their relatively poorer stability in solution under atmospheric conditions.However thiolate modified Ag NCs are more attractive for biomedical applications,especially for subcellular imaging,because of their ultrasmall hydrodynamic diameters,facile post-functionalization,strong-emitting,and antibiosis.Therefore,it is of great significance to research and develop economic and simple method to synthesize stable,strong luminescence,biocompatible silver nanoclusters.In this paper,silver nanoclusters modified by thiolate molecular were used as the object of our study.Water-soluble silver nanoclusters were prepared by one-step method.The special optical properties of silver nanoclusters modified by different templates were discussed and a series of analytical methods were established for biochemical analysis.The detection methods were studied based on various measurement techniques.The main contents of this paper are summarized as follows:1.D-Penicillamine（DPA）is a small thiolated molecule containing amines,we synthesized a novel thiolated silver nanocluster capped by Penicillamine.The amount of capping agent,the molar ratio of DPA to Ag,reaction temperature,pH,temperature and other conditions was study for the synthesis of a red emission peak of soluble silver nanoclusters.The synthesized DPA-Ag NCs were characterized by FL,UV-VIS,TEM,FT-IR and other methods.The interaction between-SH and Ag was proved by infrared absorption spectrum.And a fluorescent probe for the detection of Cu²⁺with high efficiency,rapidity and sensitivity was proposed through the strong reaction between bivalent copper ion and amine in penicillamine.In order to research the application value of the novel fluorescent probe,we detect Cu²⁺in tap water.Great accuracy was obtained,our method showed great potential of in biological molecular recognition applications.2.The optimum conditions for the synthesis of hydrosoluble glutathione modified Ag NCs were studied through one-step chemical reduction method using ascorbic acid as an environmental-friendly reducing agent.Ascorbic acid（AA）and arginine（Arg）were detected through fluorescence quenching to fluorescence recovery.A novel fluorescent“turn-off-on”switch sensor was established for detection of AA and Arg respectively.Meanwhile,it is proved that the mechanism of determination is:AA reduces the monovalent silver ions surrounding the silver core,so that the size of the clusters becomes larger thus the silver intensity is quenched.Then the guanidine groups in Arg induced aggregation within silver nanocluster solution which light on the GSH-Ag NCs/AA system.In addition,our method showed great accuracy when employed to detect AA and Arg in human urine and serum,which shows its great potential in biological molecular recognition applications.3.We proposed a one-pot method for synthesis of a strong fluorescence,double-emission,water-soluble Au/Ag NCs modified by glutathione based on the previous research work,through controlling the amount of Au³⁺and the other synthesis conditions.And the effects of different synthesis conditions on the Au/Ag NC were investigated by means of FL and TEM.We discussed the feasibility and mechanism of the detection of arginine（Arg）and cysteine（Cys）by alloy clusters andthe ratiometric fluorescent method was applied to detect the Arg and Cys selectively.The linear ranges were:5-100μm,0.05-50μM,and the detection limits were 0.25μm and 2.5 nM,respectively.In addition,we successfully applied GSH-Au/Ag NCs to the detection of Arg and Cys in human urine and serum,which proved that our method was feasible in bio-sensing.