The Optical Regulation Of Rare Earth On Conversion Luminescence Materials And Its Preliminary Application Research

Now rare earth upconversion luminescent nanoparticles ?UCNPs?has caused a lot of attention in the field of biomedical research, which has a close relationship with the unique optical properties of UCNPs, such as good chemical stability and optical stability, low autofluorescence interference, non-toxic, low signal-to-noise ratio and the near infrared excitation. Especially NaYF₄:Yb/Er UCNPs, which have been widely used in disease diagnosis, biological sensors and biological detection, etc., but the application of upconversion nanoparticles, especially in vivo, has so far largely been hampered due to the strong tissue absorption of short-wavelength light below 600 nm. Therefore, it is an urgent need to carry out some new selective approaches to increase red emission efficiency. This paper will introduce the transition metal ions (Mn²⁺/Fe³⁺) to NaYF₄:Yb/Er UCNPs in order to improve upconversion red emission. The enhancement in red upconversion luminescence intensity makes UCNPs meet the needs of the biological imaging of deep tissue. And in recent years, environmental problems has caused the attention of both at home and abroad, and photocatalytic technology in solving environmental problems has become an effective way, particularly semiconductor TiO₂ photocatalyst, which is widely used due to the long-term stability, non-toxic, low cost and environmentally friendly. But TiO₂ belongs to wide bandgap semiconductor, which just can make use of the accounts for less UV light in natural light, that is natural light utilization rate is not high. This paper will launch the strong ultraviolet NaYF₄:Yb/Tm and TiO₂ composite, through the principle of fluorescence resonance energy transfer broaden the absorption spectrum of TiO₂, thus improving TiO₂ for the utilization of sunlight, eventually improve the photocatalytic performance of TiO₂. So we have carried out the following main research content:Firstly, we successfully synthesized NaYF₄:Yb3+, Er3+ UCNPs by a facile and straightforward hydrothermal method, on the basis of this method, NaYF₄:Yb3+, Er3+ UCNPs doped with different concentrations of Mn²⁺/Fe³⁺were successfully synthesized. X-ray powder diffraction ?XRD? and the fluorescence spectrum characterization methods proved that the Mn²⁺/Fe³⁺doping for NaYF₄:Yb/Er have a great improvement on the crystal structure and red upconversion emisssion. The UCNPs were tested by scanning electron microscope ?SEM?, transmission electron microscope ?TEM? and Fourier infrared absorption spectrum ?FT-IR?, the results showed that the size and morphology of the prepared UCNPs were uniform and controled. And the surface of UCNPs were modified by amino, thus it is good for further biological imaging applications.Secondly, NaYF₄:Yb/Tm were synthesized by a facile and straightforward hydrothermal method. The experiment found that the kinds of surfactants, rare earth ions doped concentration, reaction temperature and the fluorine source had a great influence on the morphology, crystal structure and luminous intensity. By XRD, SEM and fluorescence spectrum, test results proved that purple emission of the NaYF₄:Yb/Tm has greatly improved. And the synthetic optimum process conditions of NaYF₄.Yb/Tm were obtained, in order to facilitate further TiO₂ composite and fill the blank of the near-infrared light catalysis.Finally, according to the optimum process conditions, we synthesized the strong purple emission NaYF₄:Yb/Tm. Through hydrolysis of tetrabutyl titanate, under hydrothermal conditions, NaYF₄:Yb/Tm/TiO₂ composite were obtained. A series of characterization methods proved that TiO₂ had been successful compounded the surface of NaYF₄:Yb/Tm. At the same time, with xenon lamp as light source, photocatalytic performance of NaYF₄:Yb/Tm/TiO₂ composite materials was verified by the experiments of the degradation of organic dyes. Compared to the homemade TiO₂, NaYF₄:Yb/Tm and the mixture of NaYF₄:Yb/Tm and TiO₂, the photocatalytic performance of composite materials has obvious enhancement, which derived from the compact interface between NaYF₄:Yb/Tm and TiO₂ of composite materials. The energy transfer between NaYF₄:Yb/Tm and TiO₂ of composite materials was more more convenient, thus the photocatalytic performance of composite materials was greatly improved.