Studay On The Aggregation State Control And Up-conversion Luminescence Properties Of The Novel NaLuF₄:Yb³⁺,Er³⁺ And MnF₂ Nanocomposite System

At present,the core-shell coating method commonly used to enhance and regulate up-conversion luminescence has problems such as limitation of component selection caused by lattice mismatch,difficulty in coating,and even fluorescence quenching.Aiming at this problem,this work intends to construct a new non-core-shell composite system composed of NaLuF₄:Yb³⁺,Er³⁺ and MnF₂.Since it can be compounded by adsorption and other methods,This system had the potential to avoid lattice mismatch and component limitation,and could regulate the up-conversion luminescence by adjusting the aggregation state of the composite system.The main research contentsare as follows:1.Preparation of composite components(1)Preparation of NaLuF₄:Yb³⁺,Er³⁺ nanocrystals: The monodisperse,cubic phase NaLuF₄:Yb³⁺,Er³⁺ nanocrystals with a size of about 12 nm were obtained by high-temperature solvothermal method.(2)Preparation of MnF₂ nanocrystals: Two new methods for preparing MnF₂ nanocrystals had been developed.Under optimal reaction conditions,highly dispersed tetragonal MnF₂ nanocrystals of about 20-30 nm could be prepared.2.Research on the new NaLuF₄: Yb³⁺,Er³⁺ and MnF₂ composite system(1)Direct physical mixing of NaLuF₄:Yb³⁺,Er³⁺ and MnF₂ nanocrystals to prepare a composite,and regulated its aggregation state and up-conversion luminescence.Under the best experimental conditions,the up-conversion luminescence intensity of the composite system was obviously stronger than that of NaLuF₄:Yb³⁺,Er³⁺nanocrystals.This method of changing the aggregation state of nanocrystals through simple physical mixing to regulate the up-conversion luminescence was the first report.The luminescence mechanism of the system was clarified.(2)Prepared MnF₂ nanocrystals with solutions containing NaLuF₄:Yb³⁺,Er³⁺ to obtain NaLuF₄:Yb³⁺,Er³⁺-MnF₂ complexes,and regulated their aggregation state and up-conversion luminescence.The up-conversion luminescence intensity and red-green ratio of the composite system were significantly lower than NaLuF₄:Yb³⁺,Er³⁺ nanocrystals.The luminescence mechanism and quenching mechanism of the system were clarified.3.Research on NaLuF₄:Yb³⁺,Er³⁺@nNaLuF₄-MnF₂ composite system The NaLuF₄ inert shell was coated on the NaLuF₄:Yb³⁺,Er³⁺ components of the composite.By studying the up-conversion luminescence performance of the composite system,we intended to further support the speculation about the luminescence mechanism of the composite system.This work provided more evidence for the up-conversion luminescence mechanism in the above-mentioned complexes.