Preparation Of Highly Stable Copper Nanoclusters And Its Application In Biochemical Analysis

As a novel luminescent nanomaterial,fluorescent metal nanoclusters（including Au nanoclusters,Ag nanoclusters and Cu nanoclusters）possessed many superior properties,such as good biocompatibility,ultra-small nano-size,excellent physical and chemical properties,and strong luminescence.Fluorescent metal nanoclusters have been widely used in many fields such as bioimaging,electrochemiluminescence,biosensing and cell labeling.In comparison with Au nanoclusters and Ag nanoclusters,the presursor(Cu²⁺ions)used for the Cu nanoclusters（CuNCs）was relatively cheap,abundant.At present,many fluorescent CuNCs have been reported based on different types of templates or stabilizers（such as DNA,peptides,proteins,small molecular ligands,polymers and so on）.However,the CuNCs were inherently prone to aggregate and the surface could be easily oxidized on exposure to air,which leading to the poor stability.There are 28cysteine and 20 tyrosine residues in each bovine serum albumin（BSA）molecule,leading to greater protecting and reducing capabilities.BSA stabilized metal nanoclusters often possess pH-insensitive fluorescence properties because of the low degree of exposed hydrophilic groups.In this paper,on the basis of the the excellent properties of BSA,highly stable BSA-stabilized CuNCs（BSA-CuNCs）were synthesized by using BSA as the stabilizers and reducing agents.A simple and sensitive sensing method were developed for the detection of chemical molecules and biomolecules（such as tetracycline,dopamine,sulfide anion）.The main contents are as follows:1.BSA-CuNCs were prepared through one-step reduction method by using BSA as stabilizers and CuSO₄ as copper source.On the basis of the tetracycline induced fluorescence quenching of BSA-CuNCs,a rapid and label-free fluorescent biosensing method has been established for sensitive detection of tetracycline（TC）by using BSA-CuNCs as fluorescence probes.Under the optimum conditions,the strategy realizes the sensitive detection of TC in a linear range from 5.0×10^-8 to 4.0×10^-5 mol/L and with a limit of detection of 5.0×10^-99 mol/L（S/N=3）.In addition,the sensor was successfully applied to determinate the tetracycline content in milk samples.The relative standard deviation is less than 3.3%,and the recoveries are 96.0%to 102.8%.2.A label-free,sensitive and selective fluorescence sensing method was developed for the detection of dopamine（DA）by using BSA-CuNCs as fluorescence probe.DA can be easily oxidized to form the compounds with quinone structure by ambient oxygen at alkaline conditions.The fluorescence intensity of BSA-CuNCs can be quenched through the electrons transfer between the BSA-CuNCs and the compounds with quinone structure,using the compounds with quinone structure as an electron acceptor.With the increasing of DA concentration,the fluorescence intensity of BSA-CuNCs decreased gradually.Under the optimum experimental conditions,the assay showed the sensitive detection of DA in the linear range of 1.0×10^-7 to 6.0×10^-5 mol/L,and with the limit of detection of 3.0×10^-8 mol/L（S/N=3）.Moreover,the method can be used for the determination of DA content dopamine hydrochloride injection samples,and the recoveries are 99.3%to 104.3%.3.On the basis of the S^2-ions induced fluorescence enhance of BSA-CuNCs,a simple,label-free and turn-on fluorescence sensing method has been developed for the sensitive detection of S^2-ions.When S^2-ions are present,the BSA-CuNCs,interact with S^2-ions,leading to the aggregation of dispersed BSA-CuNCs,and the enhancement of fluorescence intensity of BSA-CuNCs.The fluorescent method allows the detection of S^2-ions in the linear range from 1.0×10^-6 to 8.0×10^-5 mol/L,and the limit of detection was 3.0×10^-77 mol/L（S/N=3）.Furthermore,the assay has been successfully applied for the determination of S^2-in water samples with the recoveries from 98.5%to 104.6%.