Optical Properties And Applications Of Fluorescent Metal Nanocluster Composite Structures

Fluorescent metal nanoclusters（NCs）,a new type of fluorescent materials,have more potential for development in ion detection,chemical sensing and biological imaging owing to unique photophysical properties and excellent chemical properties,such as small size,low toxicity,great biocompatibility and other related fields.However,the currently as-prepared NCs have problems such as low photoluminescence intensity,poor selectivity and no high-regularity configuration.In this thesis,a metal-organic framework material or an ionic liquid is introduced to successfully prepare a fluorescent metal nanocluster composite structures that improved above problems.Specific work content includes the following three aspects:（1）Zeolitic imidazolate framework-8（ZIF-8）material was introduced after synthesizing of AuNCs protected by glutathione（GSH）in 80°C water bath.AuNCs/ZIF-8 nanocomposites were synthesized by a two-step method and exhibited strong orange fluorescence.The fluorescence spectrum showed that the emission wavelength of AuNCs/ZIF-8nanocomposites was the same as that of AuNCs,but its fluorescence intensity was twice that of AuNCs.Transmission electron microscopy（TEM）and scanning electron microscopy（SEM）indicated that AuNCs were attached to the out surface of the diamond dodecahedron ZIF-8,and the ZIF-8 was connected by AuNCs.Interestingly,in the presence of interfering ions Hg²⁺and Cu²⁺,AuNCs/ZIF-8 can specifically and selectively detect MnO₄^-with a detection limit of 0.64mmol/L,but AuNCs have no selectivity.（2）In the presence of[Bmim]BF₄ of ionic liquid（IL）,without any reducing agent,CuNCs protected by 2-Mercapto-1-methylimidazole（MMI）were rapidly synthesized in one-pot synthesis at room temperature,emitting strong blue fluorescence.X-ray photoelectron spectroscopy（XPS）indicated that CuNCs@MMI has been successfully synthesized with the participation of IL.The infrared spectrum（FT-IR）and IL-assisted CuNCs@MMI reversible cycling at pH=4-12,indicated that IL was adhered to the surface of CuNCs@MMI through electrostatic interaction.SEM images showed that CuNCs@MMI with the assistance of IL had a triangular supernanostructures with a size of 2.5μm.TEM images indicated that CuNCs@MMI of the triangular supernanostructures were composed of spherical particles with a particle size of 2.84 nm.Moreover,TEM images further found that CuNCs@MMI synthesized in different phases have different morphologies and structures,which shows that IL has a significant effect on the regularity of CuNCs@MMI.（3）Ce-MOF@CuNCs nanocomposites showing orange fluorescence were rapidly synthesized in one step at 60°C.Compared with CuNCs@GSH,fluorescence intensity of the nanocomposite was significantly increased,and the stability was maintained for at least one month.XPS images showed that the nucleation of CuNCs@GSH and the crystallization of Ce-MOF proceed simultaneously.X-ray diffraction（XRD）and SEM images showed that Ce-MOF@CuNCs had the same crystal structure as Ce-MOF,with a snowflake-like morphology and a size of about 3μm.