Researches On Synthesis And Luminescence Of Rare Earth Ions Doped Micro/Nano Luminescent Materials Based On Energy Transfer

Over the past decades, the study of nanometric luminescent materials,especially lanthanide ion-doped luminescent nanomaterials, has become one of thehottest topics in nanoscience because of their potential applications in highperformance magnets, luminescent devices, catalysts, and other functional materialsarising from4f electrons. As an important class of inorganic materials with uniqueoptical, electrical properties of nano-and micron material has caused more and moreattention. This paper used solvothermal and high temperature solid state synthesis ofthe different systems of fluorescent material, and were characterized, the maincontents are as follows:1. A novel monodisperse BaCeF5and BaCeF5: Tb³⁺, Sm3+nanocrystals have beensuccessfully synthesized by a simple one step solvothermal synthesis. Uniformlydistributed nanocrystals with spherical morphology and an average diameter of40nm and an octahedral morphology and particle size of75-80nm were observed.X-ray diffraction （XRD）, field emission-scanning electron microscopy （FE-SEM）, photoluminescence （PL） and decay studies were employed to characterize thesamples. The results reveal that Tb³⁺-doped BaCeF₅sample shows strong greenemission centered at546nm corresponding to the⁵D₄–⁷F₅transition of Tb³⁺due toan efficient energy transfer from Ce³⁺to Tb³⁺. The decay lifetime of Tb³⁺monotonically decreases with increase of Tb³⁺concentration. The critical energytransfer distance between Ce³⁺and Tb³⁺was also calculated by methods ofconcentration quenching and spectral overlapping. Experimental analysis andtheoretical calculations reveal that the dipole–dipole interaction should be thedominant mechanism for the Ce³⁺-Tb³⁺energy transfer. Under ultraviolet irradiation,the BaCeF₅: Tb³⁺, Sm³⁺samples exhibit the typical green emission band of the Tb³⁺ions, as well as an orange-red and red emission bands of the Sm³⁺ions in thepresence of Ce³⁺ions. The highly intense orange-red and red emission bands of theSm³⁺ions were attributed to the effective energy transfer from the Tb³⁺to Sm³⁺ions,which has been justified through the luminescence spectra and the fluorescencedecay dynamics. The luminescence colours of BaCeF₅: Tb³⁺, Sm³⁺nanophosphorscan be easily tuned by changing the concentration of Sm³⁺ions. These resultssuggest that BaCeF₅: Tb³⁺, Sm³⁺nanocrystals can be explored for three dimensionaldisplays, white light sources, and so on.2. CeF₃: Er³⁺, Yb³⁺；Tm³⁺,Yb³⁺nanoplates have been successfully synthesized by asolvothermal method with further calcinations. The crystalline phase, size and opticalproperties were characterized using powder X-ray diffraction （XRD）, fieldemission-scanning electron microscopy （FE-SEM）, X-ray photoelectron spectroscopy （XPS）, Energy dispersive spectroscopy （EDS） and upconversion luminescence （UCL）.The CeF₃: Er³⁺, Yb³⁺samples showed blue emission （487nm）, green emissions （523,546nm） and red emission （654nm） under980nm excitation. The main mechanism ofupconversion is attributed to the energy transfer （ET） among Yb³⁺and Er³⁺ions inexcited states. The CeF₃: Tm³⁺,Yb³⁺samples showed blue emissions （450,475nm）and red emission （649nm） under980nm excitation. The main mechanism that allowsfor upconversion is attributed the energy transfer （ET） among Yb³⁺and Tm³⁺ions inexcited states. The results illustrate the large potential of this new class of material forphotonic applications involving optoelectronics devices.3. A novel and tunable upconversion luminescent material GdPO₄: Yb³⁺, Ln³⁺（Ln=Er, Ho, Tm） has been synthesized by conventional solid-state reaction method.Simultaneous red, green and blue （RGB） emissions were obtained after excitation at980nm. Color emission was tuned from multicolor to white light with colorcoordinate （0.328,0.327） matching very well with the white reference （0.333,0.333）.Changes in color emissions were obtained by varying the intensity ratios betweenRGB bands that were strongly concentration dependent because of the interaction ofco-dopants. The color tunability, high quality of white light and high intensity of theemitted signal make these upconversion （UC） phosphors excellent candidates forapplications in white light LEDs and biological fluorescent tags.4. A novel CaEuAl₃O₇phosphor was synthesized by a high temperature solid-statereaction method. the photoluminescence （PL） properties were investigated toexamine its application in the development of white light-emitting diodes （w-LED_s）. The red emission was observed from Eu³⁺ions in the CaEuAl3O7phosphor. TheCaEuAl₃O₇:Eu³⁺/Eu²⁺prepared in a thermal-carbon reducing atmosphere whichshows good absorption ranging from ultraviolet to a blue region centered at445nm.The above results indicate that the CaEuAl₃O₇is a good candidate as red and bluecomponent for near UV-excited w-LED_s...