Study On The Preparation Of Bimetallic Gold And Silver Nanoclusters And Its Application In Environmental Detection

Noble metal nanoclusters are widely used in environmental detection,biomedical,chemical analysis and other fields due to their good biocompatibility,fluorescence stability and emission modulation.Among them,gold and silver nanoclusters?Au/Ag NCs?have superior fluorescence performance and stability than gold nanoclusters?Au NCs?,which has higher application value in the field of analysis and detection.In this work,we synthesized BSA-Au/Ag NCs with good fluorescence performance,and used it to establish three simple,fast and sensitive sensing platforms to detect copper ions(Cu²⁺)and alkaline phosphatase?ALP?activity in water.In addition,a selective zearalenone?ZEN?fluorescent immunoassay method was established based on immunological technology.The specific contents are as follows:?1?The BSA-Au/Ag NCs with good biocompatibility and stable fluorescence performance was prepared by optimizing the molar ratio of gold and silver precursor,reaction temperature,reaction time and reaction pH using bovine serum protein as the protective agent and reducing agent.In addition,BSA-Au/Ag NCs was characterized by transmission electron microscopy,fluorescence spectroscopy,X-ray diffraction and X-ray photoelectron spectroscopy.?2?A proportional fluorescent probe capable of detecting Cu²⁺was constructed,based on the catalytic performance of Cu²⁺peroxidase-like.In this experimental system,the non-fluorescent o-phenylenediamine?OPD?can be catalyzed to form a fluorescent?580 nm?oxidation state o-phenylenediamine?DAP?,and the fluorescence peak of BSA-Au/Ag NCs at 690 nm was quenched,because there has internal filtration effect between BSA-Au/Ag NCs and DAP.Based on this fact,a simple and sensitive proportional fluorescent probe was established to detect the concentration of Cu²⁺in water.Under the optimal reaction conditions,the low detection limit of the proportional fluorescent probe was 0.0637 nmol/L,which was lower than the detection limit of Cu²⁺of most existing development techniques.?3?A“turn-on”fluorescent probe capable of monitoring ALP levels was constructed,based on the principle that ascorbic acid?AA?can restore the fluorescence of BSA-Au/Ag NCs quenched by KMnO₄.In this reaction system,the structure of the BSA-Au/Ag NCs protective layer protein was destroyed by KMnO₄ oxidation of the sulfhydryl group in BSA-Au/Ag NCs,and the fluorescence was quenched.ALP-catalyzed AA produced by ascorbic acid 2-phosphate?AAP?can reduce the oxidized sulfhydryl group,which restored the BSA-Au/Ag NCs protective layer protein and restored fluorescence of BSA-Au/Ag NCs.According to the above mechanism,a simple,fast and selective“turn-on”fluorescent probe was established to monitor the ALP level in water.Under the optimal experimental conditions,the low detection limit of the fluorescent probe was 0.00076 U/L.In addition,we have successfully prepared a visualized ALP test strip based on this program.?4?H₂O₂ can oxidize o-phenylenediamine?OPD?to form an oxidation state of o-phenylenediamine?DAP?in presence of horseradish peroxidase?HRP?,and the fluorescence of BSA-Au/Ag NCs was quenched by the presence of an internal filtration effect between DAP and BSA-Au/Ag NCs.Accordingly,the HRP linked to the antibody specifically bound during the immunization was identified,and a sensitive proportional immunofluorescence assay was established to detect the target ZEN.Under the optimal conditions,the low detection limit of the fluorescent immunoassay method was 0.02188ng/mL,and the half-inhibition(I₅₀)concentration is 0.08383 ng/mL.The sensitivity of fluorescent immunity was nearly 4.5 times higher than that of enzyme-linked immunity,and the detection of ZEN samples in the environment has a promising prospect.