Application Of Functionalized Copper Nanoclusters In Fluorescent And Electrochemiluminescent Sensing Analysis

Metal nanocluster materials（MNCs）have attracted much attention due to their adjustable optical properties,high biocompatibility,large specific surface area,and high catalytic activity.As one of these,copper nanoclusters（CuNCs）have also developed rapidly.Compared with precious metal clusters,CuNCs possess the advantages of low raw material,good biocompatibility,and diverse synthetic types,and are widely researched in the fields of sensor devices,cell imaging,detection and analysis.However,research is still in the development stage,there are still many problems（such as poor stability and low quantum yield）in the study of CuNCs that need to be improved and overcame.In this paper,starting from the synthesis of functionalized CuNCs,the fluorescent and electrochemiluminescent properties of CuNCs are explored.The research contents areas follows:This article consists of four parts.First,it gives an overview of MNCs,and summarizes the properties,synthesismethods and sensor applications of M NCs.1.Sulfide anion(S^2-)is a common toxic ion,and its excessive accumulation will have an unrecoverable impact on the environment and the human body.In this study,with mercaptopropionic acid as the protective agent and reducing agent,copper nanoclusters(Cu²⁺@MPA-CuNCs)with aggregation induced emission（AIE）induced by Cu²⁺were prepared by a one-step method.The prepared Cu²⁺@MPA-CuNCs exhibited pink fluorescence under 365 nm ultraviolet light,and the fluorescence spectrum had strong fluorescence emission at 610 nm.After adding Cu²⁺to MPA-CuNCs,the quantum yield increased from 0.56%to 4.8%.The presence of S^2-will bond with Cu⁺and Cu²⁺in Cu²⁺@MPA-CuNCs respectively,causing the fluorophore structure to be destroyed and fluorescence quenching.Based on this,a fluorescent probe for S^2-detection was constructed.The fluorescent probe has a good linear relationship with the response of S^2-in the concentration range of0-600μM,and the detection limit is 26.3 nM.In the end,the probe platform successfully realized the selective detection of S^2-in different food additives,which provided new ideas for food safety analysis.2.Enrofloxacin（ENR）as a broad-spectrum fungicide has been widely used in biomedicine.In this study,a simple and novel molecularly imprinted electrochemiluminescent（MIP-ECL）sensor based on mercaptopropionic acid functionalized copper nanoclusters was constructed for the selective detection of ENR.Under optimized conditions,the MIP-ECL sensor achieves a sensitive detection of ENR in the concentration range of 0.1 nM to 1μM,with a detection limit of 27 pM.In the actual analysis of biological and lake water samples,the recovery rate was 89.6-105%.The MIP-ECL sensing platform is simple to operate,has good selectivity,and high sensitivity.It provides ideas for solving the stability problem of CuNCs,and may open up new ways for the development ofnew ECLsystems for biological analysis and environmental watermonitoring.3.As an important reactive oxygen species,hydrogen peroxide（H₂O₂）is an indispensable intermediate product in biological processes and mediates a variety of physiological functions.It is also often used in medicine,industry,agriculture and other fields.In this work,using lipoic acid（LA）and sodium borohydride as protective ligands and reducing agents,respectively,CuNCs were synthesized by one-step method.LA-CuNCs@CS nanocomposites were prepared by wrapping LA-CuNCs with chitosan（CS）.After adding CS,the fluorescence intensity and stability of LA-CuNCs were significantly improved,which might be attributed to AIE of LA-CuNCs caused by CS.When H₂O₂is present in the system,the copper in LA-CuNCs@CS will be oxidized to cause fluorescence quenching.Therefore,a fluorescent probe based on LA-CuNCs@CS was developed for H₂O₂with a detection limit was 47 nM.The fluorescent probe has good selectivity and high sensitivity,which was successfully detected H₂O₂in environmental water samples and provides a newidea for thedevelopment of H₂O₂detection probes.