The Self-Assembly Effect Of Copper Nanoclusters And Its Analytical Application

Among all the luminescent metals,the copper nanocluters(CuNCs)are of immense interest due to the molecule-like properties,unique optical property,good biocompatibility and relative earth abundance.Until now,the development of green and facile synthesis of chemically stable luminescent CuNCs in aqueous solution remains a challenge.Recently,the strategy of aggregation-induced emission(AIE)has recently been exploited to make weak-emitting CuNCs highly luminescent.Based on the understanding of characteristic of the metal NCs and the AIE phenomenon,L-cysteine-templated CuNCs were used as the research objects in this dissertation,we investigated the reversible pH response of luminescence and mophology of CuNCs.Base on the above properties,we developed a facile pH-guided strategy for the fabrication of water-soluble protein/CuNCs hybrid nanostructures,and its possibility of optical detection of glucose in physiological environment.The details are shown as follows:Using L-cysteine as both reducing and capping agent,the synthesized CuNCs showed a good reversible pH-responsive aggregation and dispersion in the solution.The CuNCs formed insoluble macroscopic aggregates with stable red-colored emission(620 nm)when pH was between 1.0 and 4.5,and its emission and aggregation reached the maximum at pH 3.0,but become soluble with weak luminescence at pH<1.5 or pH>4.5.The luminescence,morphology and structure of the CuNCs were characterized by luminescence spectrophotometer,Atomic Force Microscope,Transmission Electron Microscopy and Mass Spectrometer,and finally its reversible pH response and AIE behavior was proved.The AIE-based strategy often requires the CuNCs to form large aggregates with poor solubility and low stability in the aqueous suspension,which would hamper the applications that required the nanomaterials with good solubility.Because the protein(e.g.bovine serum albumin(BSA))show strong adsorption ability to the surface of the metal NPs,and the synthesized CuNCs showed a good reversible pH-responsive aggregation and dispersion in the solution,we here reported a facile pH-guided strategy for the fabrication of water-soluble protein/CuNCs hybrid nanostructures based on AIE.The weak luminescent CuNCs were firstly mixed with proteins under neutral condition(e.g.pH 7.0),followed by tuning the pH to acidic condition(e.g.p H 3.0)to form water-soluble protein/CuNCs hybrid nanostructures with stable and bright luminescence.Characterized by various measurements,we found that the sizes of BSA/CuNCs hybrid nanostructures were much smaller than those of the protein-free macroscopic CuNC aggregates,and it preserved its luminescent property and still maintain good reversible pH-responsive aggregation and dispersion in the solution.Using a biofunctional protein glucose oxidase(GO_x)as an example,we also assembled GO_x/CuNCs using GO_x and CuNCs,and found that the GO_x preserved the catalytic activities even after the self-assembly.The decrease of the GO_x/CuNCs emission intensity responded selectively and was exponentially fitted with increasing concentrations of glucose.The limit of detection(LOD)of glucose was 1.5 ?M based on the 3? criterion.This mild strategy demonstrated here could be easily extended to other types of dispersing agents,which would be a promising new path for the design and fabrication of smart water-soluble luminescent biomolecule/nanoclusters hybrid nanostructures for specific applications.