Synthesis,Optical Properties And Application Of Highly Efficient Lanthanide-Doped Luminescent Materials

In this thesis,we primarily investigated the synthesis,optical properties and application of highly efficient lanthanide-doped luminescent materials.We mainly focused on the preparation,optical spectroscopy and application for light-emitting diodes（LED）of lanthanide-doped white-emitting NaSrBO₃ phosphor.Meanwhile,a preliminary research on the controlled synthesis,single-band emission mechanism and bioapplication of lanthanide-doped KMnF₃ nanocrystals（NCs）has been made.The main contents are as follows:A series of Ce³⁺,Sm³⁺ and Tb³⁺ co-doped NaSrBO₃ phosphors were synthesized via a high temperature solid-state reaction and their luminescent properties were studied.Based on photoluminescence（PL）excitation and emission spectra,an energy transfer between Ce³⁺ and Sm³⁺ was observed in NaSrBO₃ phosphors.The energy transfer mechanism between Ce³⁺ and Sm³⁺ ions was found to be predominantly of dipole-dipole nature and the corresponding critical distance for the doped ions was calculated to be 4.84 A.Upon near ultraviolet（NUV）excitation at 360 nm,tunable emissions from violet to white in visible region were realized in NaSrBO₃:Ce,Sm,Tb phosphors by controlling the dopant concentrations.Thermal quenching effect on the photoluminescence of NaSrBO₃:Ce,Sm,Tb was surveyed over the range of 300-600 K,showing a good thermal stability with an activation energy as high as 0.32 eV for LEDs application.By integrating this single-composition white-emitting NaSrBO₃:Ce,Sm,Tb phosphor with a 360-nm NUV chip,we fabricated a high-performance white LED（WLED）device,which exhibited an excellent color rendering index（CRI）of 80.1 and a correlated color temperature（CCT）of 6731 K with CIE coordinates of（0.311,0.314）.Furthermore,we synthesized monodisperse and size-controllable KMnF₃:Yb,Er NCs via thermal decomposition and high temperature coprecipitation method,respectively.The structures and shapes were characterized by powder X-ray diffraction（XRD）,transmission electron microscopy（TEM）,energy dispersive X-ray（EDX）spectrum,etc.Moreover,the optical properties of Mn2+ in KMnF₃ NCs and the mechanism of single-band upconversion emission of Er³⁺ in KMnF₃:Yb,Er NCs were investigated by temperature-dependent high resolution excitation,emission spectra,and upconversion（UC）spectra.To render these hydrophilic KMnF₃ NCs biocompatible,surface modification was carried out through acid-treated procedure to remove native oleic acid ligands on surface.The successful transferring to hydrophilic NCs was well established by Fourier-transform infrared（FTIR）spectrum and thermogravimetry curve（TGA）analysis of the NCs.