The Study In The Mechanism And Properties Of Casein-mediated Copper Nanoclusters

Biomolecule-templated metal nanoclusters have attracted a great deal of attention in chemical sensing,environmental monitoring,biological imaging and clinical diagnosis for their excellent biocompatibility and unique optical properties.Compared with other biomolecules,protein molecules have diverse functional groups and structure,which is considered as one of the most ideal material for synthesis of metal nanoclusters.In this work,casein,a protein found widely in mammal milk,was selected as template for synthesis of copper nanoclusters(Cu NCs).The effect of various reaction conditions on the synthesis of(Cu NCs)and the synthesis mechanism was studied in detail.Furthermore,we preliminarily explore the optical response of as-prepared Cu NCs on environment stimulus,which may lay the basis for further application of Cu NCs in p H sensing.1.To the best of our knowledge,we first used casein as a template for synthesis of Cu NCs.The effect of template concentration,reducing agents,temperature,p H and reaction time on the synthesis of Casein@Cu NCs was investigated systematically.Under the optimal synthesis condition,the as-prepared Cu NCs are 2.1 ± 0.2 nm in size and exhibit excitation/emission peak at 425 and 483 nm respectively with the quantum yield of 14.5%.It was deduced that the –NH2 of amino acid residue of casein may offer the binding sites for copper ions and ?-helix structure of casein provide a local hydrophobic environment,which facilitate the synthesis of Cu NCs.2.In this chapter,explore the optical response of as-prepared Casein@Cu NCs on a variety of environment stimulus,including UV irradiation,heating,heavy metal ions,organic solvent and p H.It was shown that the Cu NCs exhibits high stability.The fluorescence properties of casein@Cu NCs were almost unchanged under UV irradiation(200 W,2 h),temperature(30?-90?)and ionic strength(100– 300 m M Na Cl)variations,the addition of heavy metal ions(0.5 m M)and organic solvent().However,we foud that the fluorescence intensities of casein@Cu NCs were quite sensitive to p H in the range of p H 5-11.