Preparation Of Fluorescent Copper Nanoclusters And Their Analytical Application

Metal nanoclusters(MNCs)as a new type of fluorescent nanomaterial have excellent properties such as good water solubility,large Stokes shift,strong photostability,low toxicity and high luminous efficiency.MNCs have been widely applied to practical applications in various fields,such as chemical detection,biomarker and cell imaging.In contrast to gold nanoclusters and silver nanoclusters,copper nanoclusters(Cu NCs)have excellent optical properties,good water solubility and low preparation cost.Therefore,the study regarding Cu NCs has been attracting increasing attentions.However,it is more challenging to prepare Cu NCs of high stability and ultrafine size because they are easily oxidized and difficult to control in size.Fluorescent Cu NCs were prepared in this experiment and their analytical applications were studied.Using bovine serum albumin(BSA)as the template and sodium thiosulfate(Na2S2O3)as the reducing agent,BSA-Cu NCs with good water solubility and high stability were synthesized by one-pot approach.The as-prepared BSA-Cu NCs were characterized by X-ray photoelectron spectroscopy(XPS)and transmission electron microscopy(TEM).The maximum excitation and emission wavelengths of BSA-Cu NCs are at 336 nm and 407 nm.The average size of BSA-Cu NCs was about 2 nm.Based on the synthesized BSA-Cu NCs respond sensitively to changes in pH,a sensitive and reversible fluorescent pH sensor was constructed.In the range of pH 6.0?11.0,the fluorescence intensity of BSA-Cu NCs increased linearly and increased by nearly 9-fold about at high pH values compare with a low pH of 6.0.Subsequently,based on the internal filtration effect between BSA-Cu NCs and Cr(?),a new fluorescence analysis method was established for the determination of Cr(?).The linear range of the method is 0.5?1000 ?mol/L,and the detection limit is 0.3 ?mol/L.The Cr(?)in the actual water sample was tested and recoveries were between 96.6%and 103%,indicating that the method can be used for the determination of actual water samples.Using histidine(His)as a template and cysteine as a reducing agent,His-Cu NCs with good water solubility and high stability were synthesized by one-pot approach.The maximum excitation and emission wavelengths of His-Cu NCs are at 443 nm and 525 nm.The as-prepared His-Cu NCs were characterized by XPS and TEM.The results show that the as-prepared His-Cu NCs are composed of copper atoms,and the His-Cu NCs are spherical with the size of about 2 nm.Based on the quenching of His-Cu NCs fluorescence by dopamine,an analytical method for the determination of dopamine was established.The quenching efficiency of His-Cu NCs fluorescence intensity has a good linear relationship with the concentration of dopamine.The linear range is 0.1?10 ?mol/L,and the detection limit is 0.04 ?mol/L.The method was used to detect dopamine in dopamine hydrochloride injection sample,and recoveries were 97.5%and 104%,indicating that the method is accurate and reliable.