The Preparation And Application Of Gold-silver Bimetallic Nanoclusters

Gold-silver bimetallic nanoclusters（Au-Ag NCs）show many advantages over single metal nanoclusters due to the synergistic effect of Au and Ag,such as enhanced fluorescence intensity,better stability and higher catalytic activity,which broaden the application of Au-Ag NCs in different research fields.In this thesis,N-Acetyl-L-cysteine（NAC）and L-cysteine（L-Cys）were used as ligands to synthesize Au-Ag NCs with good properties.Based on different detection mechanisms,they were used for colorimetric and fluorescence detection of hydrogen sulfide（H₂S）,fluorescence detection of quercetin（Que）and catalytic reduction of nitrophenol,respectively.The main research work includes the following three parts.1.The NAC@Au-Ag NCs with near-infrared emitting and large Stokes shift was prepared by refluxing method and used for fluorescence colorimetric dual-signal detection of H₂S.The synthesized nanoclusters exhibited strong red fluorescence with theλ_em of 700nm and QY of 0.25.Because the formation of metal sulfides can induce the fluorescence quenching of the as-synthesized NCs,NAC@Au-Ag NCs were used for fluorescence detection of H₂S.In addition,the NAC@Au-Ag NCs could be easily attached to test strips,and the color of test strips changed from white to brown-yellow when H₂S was added.Thus,colorimetric detection method of H₂S was established by the color recognition software of smartphone.The linear relationship between the concentration of H₂S and the chroma value of the solution was observed.Fluorescence and colorimetric sensing based on NAC@Au-Ag NCs had been used for cell imaging and monitoring the food spoilage processes.2.L-Cys@Au-Ag NCs with good photostability and aggregation induced luminescence（AIE）were prepared by ultrasonic method and used for the fluorescence detection of Que.The Au-Ag NCs with better luminescence properties were obtained by optimizing the synthesis conditions.The Au-Ag NCs exhibited obvious enhanced fluorescence compared with Au NCs.The properties（optical properties,stability,size,etc.）of L-Cys@Au-Ag NCs were characterized by different analytical methods.Based on the fluorescence quenching effect of Que on L-Cys@Au-Ag NCs,the method for the detection of Que was developed.The optimum detection conditions,quantitative relationship and the feasibility of this method were determined.The synthesized L-Cys@Au-Ag NCs fluorescent material had been applied to the detection of Que in grape juice samples.3.N-Acetyl-L-cysteine stabilized NAC@Au-Ag NCs showed good catalytic activity and stability,which made the as-synthesized NCs could be used as a catalyst to reduce nitrophenol.The successful synthesis and kinetic stability of the nanoclusters were proved by different analytical methods.Based on the catalytic mechanism of Langmuir-Hinshelwood model,the synthesized Au-Ag NCs was used as catalyst for the catalytic reduction of nitrophenol,including 2-nitrophenol（2NP）,3-nitrophenol（3NP）and4-nitrophenol（4NP）.The relationship between the catalytic activity of nanoclusters and catalyst dosage,reaction temperature was investigated.The catalytic rate constants and thermodynamic parameters under different conditions were calculated.And the reproducibility of the nanoclusters as a catalyst was discussed.This method provides a new way for the removal of nitrophenol pollutants.