Synthesis,Structures And Fluorescent Property Of Silver Nanoclusters Protected By Alkynyl And Bidentate Phosphine Ligands

Silver nanoclusters have attracted much research attention for their ultra-small size and unique fluorescent properties.Such properties provide good platforms to construct luminescent probes for bio-imaging and sensing applications.However,the low stability of silver nanoclusters usually results in the immediate aggregation of the nanoclusters into nanoparticles,which hinders their synthesis and application.In this thesis,alkynyl and bidentate phosphine were selected as capping ligands to synthesize structurally stable silver nanoclusters.A series of silver nanoclusters with new structures were prepared by introducing pyridyl ligands or anionic templates into the synthesis system,supplemented by reduction reaction and solvothermal reaction.The structures of these silver nanoclusters were determined by single crystal X-ray diffraction,and their fluorescent properties were studied.The main contents of this thesis are summarized as follows:(1)Two silver-ethynide clusters:[Ag₈(^tBuC?C)₅(CF₃CO₂)₃]_nand[Ag₁₂(^tBuC?C)₆(CF₃CO₂)₈]·2TEA(TEA=tetraethylammonium ion)were obtained by the reaction of ^tBuC?CAg with CF₃COOAg in different solvents.When 4-aminopyridine and pyridine were introduced as capping ligands in the above reaction system,two pyridyl-protected silver-ethynide clusters:[Ag₃(^tBuC?C)(CF₃CO₂)₂(4-ap)]_nand[Ag₈(^tBuC?C)₄(py)₈]·4BF₄were successfully separated.Single crystal X-ray diffraction analysis proved that the change of solvent system and the addition of two different pyridyl ligands could cause changes in the composition and structure of silver-ethynide clusters.(2)Using MS₄^2-(M=Mo/W)as the anion template,^tBuC?CAg as the precursor and1,4-bis(diphenylphosphine)butane as the ligand,four 58-nuclear silver nanoclusters[(MS₄)@Ag₅₈S₂₄(dppb)₁₂](M=Mo/W)with 8-electron shell closure protected by bidentate phosphine ligands were obtained by reduction method.Their structures and properties were characterized.Single crystal X-ray diffraction analysis showed that the structure of[(MoS₄)@Ag₅₈S₂₄(dppb)₁₂]is similar to that of[(WS₄)@Ag₅₈S₂₄(dppb)₁₂],and both have two different space groups.It is found that the liquid fluorescence intensity of the clusters can be controlled by the interaction between the compounds containing benzene rings and the bidentate phosphine ligands on the surface of the clusters.(3)Two silver-ethynide clusters:[NO₃@Ag₁₈(^tBuC?C)₁₅]·2NO₃and[Br@Ag₁₉(^tBuC?C)₁₁(CF₃CO₂)₇]containing inorganic anion templates were successfully prepared by solvothermal reaction of ^tBuC?CAg with different silver salts.In addition,on the basis of the synthesis of[(MoS₄)@Ag₅₈S₂₄(dppb)₁₂],a mixed valence silver nanocluster[Ag₁₃₀S₅₈(dpppe)₁₈]protected by bidentate phosphine ligand was obtained by changing the type of bidentate phosphine ligand and assisted by solvothermal reaction.It has a core-shell structure of Ag₇(core)@Ag₄₂S₁₄(first shell)@Ag₈₁S₄₄(second shell).The UV absorption peak at 630 nm and the fluorescence emission peak around 450 nm correspond to its high nuclear structure.