Synthesis Of Fluorescent Copper And Silver Nanoclusters And Their Applications

With the size of metal nanoclusters approaching to the Fermi wavelength of electrons,metal nanoclusters exhibit molecular-like properties,including discrete energy levels,HOMO-LUMO transitions and size-dependent fluorescence.Compared with organic dyes,perovskite quantum dots,metal nanoclusters exhibit inherent merits,such as prominent photostability,biocompatibility,large Stokes shift,strong fluorescence and low environmental hazards.Therefore,fluorescent metal nanoclusters have wide and promising applications,in the field of detecting toxic substance,cell labelling,fluorescence imaging,photoelectronic devices and so on.Compared with noble metals,copper is relatively cost-efficient and with wide resources.Due to the low redox potential,copper nanoclusters suffer from oxidation easily,which enhances the difficulty in preparing copper nanoclusters.Besides,most copper nanoclusters obtained in water show low quantum yield and poor stability,which is not beneficial for further cell labelling and other bioapplications.In order to solve these problems,water soluble,green and blue-emitting copper nanoclusters with high quantum yield,good stability and low cytotoxicity were obtained by low temperature hydrothermal method.And they were employed for analytical detection and cell imaging.In contrast to common organic fluorophores with flat conjugated structures that show aggregation-caused quenching(ACQ)phenomenon,luminogens with aggregation-induced emission(AIE)can emit intense light in the aggregated or solid state.Most studies on AIE luminogens are focused on organic molecules,such as tetraphenylethene,rarely focused on metal nanoclusters.Moreover,some metal nanoclusters also exhibit ACQ phenomenon.For this disadvantage,by self-assembly,silver nanoclusters with AIE and special morphologies were achieved.The as-prepared AgNCs@TSA assemblies show nanofiber,nanoribbon and nanosheet morphologies prepared in water and other solvents,with strong orange photoluminescence in aggregated state.The main contents are listed as follows:(1)The green-emitting copper nanoclusters stabilized by PVP(CuNCs@PVP)were prepared,whose relative quantum yield was up to 44.67%,and the reaction conditions were optimized.The as-prepared CuNCs@PVP shows good stability and low cytotoxicity,and used for cell imaging in THP-1 cells,quantitatively detecting toxic trinitrophenol in water and ethanol medium.(2)The blue-emitting copper nanoclusters stabilized by PTMP-PMAA(CuNCs@PTMP-PMAA)were prepared,whose relative quantum yield was up to 37.08%,and reaction conditions were optimized.The as-prepared CuNCs@PTMP-PMAA exhibits strong fluorescence,good stability,and used for the detection of hydrogen peroxide quantitatively.(3)By using thiosalicylic acid(TSA)as a protection and reducing agent,photoluminescent silver nanoclusters(AgNCs@TSA)assemblies with AIE was obtained.The highest absolute quantum yield for AgNCs@TSA assemblies was 13.05%.The structure and morphology of AgNCs@TSA assemblies can be tuned by changing the reaction conditions.Besides,the photoluminescence,structure and morphology were characterized.