Fabrication And Applications Of Fluorescent Nanocomposites

In recent years,increasing researchers begin to pay attention to novel functional fluorescent nanocomposites.The studies of the preparation method and subsequent application of fluorescent nanocomposites have been developed drastically.Fluorescent nanocomposites are functional nanomaterials,which combines fluorescent material and other materials into one entity.This kind of fluorescent nanocomposite materials has both the excellent properties of fluorescent materials and the unique performance of the combined nanomaterials,such as:biological imaging,fluorescent anti-counterfeiting.This thesis will focus on macroscopic preparation,chemical modification and applications of carbon dots,ultrathin g-C₃N₄ nanosheets and upconversion rare earth nanoparticles.?1?Bulk g-C₃N₄ was prepared by direct pyrolysis of melamine.Then,Ultrathin g-C₃N₄ nanosheets were achieved through the liquid exfoliation of bulk g-C₃N₄ in deionized water.In our proof of concept prototype,citric acid modified multicolored upconversion nanoparticles?cit-UCNPs?were grafted onto the surface of-NH₂/-HN terminated g-C₃N₄ nanosheets via covalent cross-linking.Due to the limitation of the top-down stripping method,the lateral dimension of resulting g-C₃N₄ nanosheets was not uniform,ranging from approximately 100 nm to 1.5?m.Under the excitation of ultraviolet wavelength,the ultrathin g-C₃N₄ nanosheets was a fixed emission wavelength?449 nm?,showing strong blue fluorescence.The novel dual-mode luminescent nanopaper?cit-UCNPs@g-C₃N₄/CS?for anticounterfeiting that simultaneously possessed down-and upconversion photoluminescent properties was successfully achieved via a simple evaporation.With the optimal loading of 40wt%,the luminescent nanopaper?cit-UCNPs@g-C₃N₄/CS?exhibited high optical transmittance?93.8%at 550 nm?and excellent mechanical properties.?2?Carbon dots was prepared by a convenient one-step hydrothermal treatment using citric acid and ethylenediamine,and were subsequently functionalized with sodium chloroacetate to provide them with functional carboxyl groups.After EDC/NHScovalentcrosslinking,thebiocompatibleandnontoxic CDs-COOH@PEA-NFAp conjugates were investigated by carrying out a series of MTT assays with three different cell lines.Furthermore,the bio-nanoplatform was successfully applied for the bioimaging of MCF-7 breast cancer cells.The conjugates with perfect biocompatibility and excellent optical properties can be potentially used as a multifunctional nanoplatform for tissue engineering,bioimaging,and targeted drug or gene delivery applications.