Construction, Photoluminescence And Magnetism Of Rare Earth Fluorides Micro-/Nano-Materials

Rare earth ion(RE³⁺)doped micro-/nano-materials have been attracting considerable research interest of scientists due to their potential applications in optics andoptoelectronicsandbiomedicalfields.Amongthelarge number of luminescent materials,fluoride micro-/nano-materials have some distinct advantages,for instance,low phonon energy,high refractive index and chemical stability,and relatively low crystallization temperature.Thus,it is considered to be a prominent luminescent host material.Simultaneously,the fluoride containing gadolinium?Gd?has paramagnetic properties originating from the intrinsic magnetic moment of Gd³⁺ions in the host.Therefore,the fluoride containing gadolinium is a multifunctional material.The Y³⁺sites can be easily replaced by trivalent lanthanide ions with the same valence state and similar ionic radius.Yttrium trifluoride?YF₃?is well-known as an excellent fluorescent host lattice.At present,there are many studies on the up-conversion luminescence of fluoride materials,and few attention is paid to the down-conversion luminescence of fluoride materials.However,these down-conversion luminescence materials have important potential applications in FED,optical elements in composite materials,color displays and multimodal transport imaging,bioseparation,drug carrier and so on.In this thesis,for BaGd F₅,GdF₃ and YF₃,the down-conversion white light and multicolor light emission have been obtained by doping the different rare earth ions(Dy³⁺,Tb³⁺,Eu³⁺,Sm³⁺,Tm³⁺).The morphology controllable and energy transfer mechanism and luminescence and magnetism properties have been reported and discussed in detail.The main content is as follows:1.GdF₃:Dy³⁺,Tb³⁺,Eu³⁺luminescent materials were synthesized by a one-step hydrothermal method.The structure,morphologies,luminescence,and magnetism properties of the products were investigated.In the GdF₃:Dy³⁺,Tb³⁺phosphor,the different hues of the green emissions could be achieved by properly designed doped rare earth ions contents.In the GdF₃:Tb³⁺,Eu³⁺phosphor,the different hues of red emissions could be achieved by properly designed doped rare earth ions contents.More importantly,the emission of white light can be achieved by adjusting the doping concentration of single activated ion Eu³⁺in single phase matrix triply?GdF₃?doped Dy³⁺,Tb³⁺and Eu³⁺.Furthermore,the Gd F₃:Dy³⁺,Tb³⁺,Eu³⁺samples exhibit paramagnetic properties at room temperature and low temperature.2.GdF₃ micro-/nano-materials were synthesized by a glutamic acid hydrothermal method.The size and shape of the products could be tuned just by adjusting the pH values of the initial reaction solutions.Simultaneously,the possible formation mechanism of multiform morphologies was proposed.In addition,the fluorescence property of Dy³⁺,Tb³⁺,Sm³⁺in GdF₃ matrix was investigated thoroughly.The energy transfer mechanisms of Tb³⁺to Sm³⁺in the host have been studied.More importantly,white light and multicolor light have been obtained in Tb³⁺,Sm³⁺co-doped or Dy³⁺,Tb³⁺,Sm³⁺tri-doped GdF₃ phosphors.3.GdF₃ micro-/nano-materials were synthesized by an L-arginine hydrothermal method.The size and shape of the products could be tuned just by adjusting the pH values of the initial reaction solutions.By adjusting their relative doping concentrations in the Gd F₃ host,the different color hue of blue and yellow light are obtained in GdF₃:Tm³⁺,Dy³⁺and GdF₃:Dy³⁺,Eu³⁺,respectively.More significantly,in the Tm³⁺,Dy³⁺,Eu³⁺tri-doped GdF₃ phosphors,white light can also be achieved upon excitation of UV light by adjusting the doping concentration of rare earth ion(Tm³⁺,Dy³⁺,Eu³⁺).4.BaGdF₅:Tb³⁺,Sm³⁺luminescent materials were synthesized by a one-step hydrothermal method.The structure,morphologies,luminescence,and magnetism properties of the products were investigated.In the BaGdF₅:Tb³⁺,Sm³⁺phosphor,multiple?white,orange red,green and yellow green?emissions could be achieved by adopting different excitation wavelengths or adjusting the appropriate concentration of Sm³⁺and Tb³⁺.The energy migration from Tb³⁺to Sm³⁺has been reported in detail.Furthermore,the BaGdF₅:Tb³⁺,Sm³⁺sample exhibit paramagnetic properties at room temperature and low temperature.5.BaGd F₅:Dy³⁺,Eu³⁺luminescent materials were synthesized by a one-step hydrothermal method.Based on the rare earth concentrations and excitation wavelengths,multiple?white,red,blue and green yellow?emissions are obtained in BaGdF₅:Dy³⁺,Eu³⁺.In addition,the energy migration from Dy³⁺to Eu³⁺has been reported in detail.Furthermore,the obtained samples also exhibit paramagnetic properties at room temperature and low temperature.6.BaGdF₅:Dy³⁺,Tb³⁺,Eu³⁺luminescent materials were synthesized by a one-step hydrothermal method.Under UV excitation,BaGdF₅:Dy³⁺,BaGdF₅:Tb³⁺and BaGd F₅:Eu³⁺samples exhibit strong blue,green and red emissions,respectively.By adjusting their relative doping concentrations in the BaGd F₅ host,the different color hues of green and red light are obtained by co-doped Dy³⁺,Tb³⁺and co-doped Tb³⁺,Eu³⁺ions in the BaGdF₅ host,respectively.Besides,there are two energy transfer pairs in the BaGdF₅ host:?1?Dy³⁺?Tb³⁺and?2?Tb³⁺?Eu³⁺.More importantly,the emission of white light can be achieved by adjusting the doping concentration of single activated ion Eu³⁺in single phase matrix?BaGdF₅?triply doped Dy³⁺,Tb³⁺and Eu³⁺.7.YF₃ micro-/nano-materials were synthesized by a glutamic acid hydrothermal method.The size and shape of the products could be tuned just by adjusting the pH values of the initial reaction solutions and the ratio of RE³⁺/NaF and RE³⁺/NaBF₄.In the YF₃:Dy³⁺,Tb³⁺phosphor,the different hues of the green emissions could be achieved by properly designed doped rare earth ions contents.Simultaneously,the energy migration from Dy³⁺to Tb³⁺has been reported in detail.In the YF₃:Tb³⁺,Eu³⁺phosphor,the different hues of red emissions could be achieved by properly designed doped rare earth ions contents.Simultaneously,the energy migration from Tb³⁺to Eu³⁺has been reported in detail.More importantly,the emission of white light can be achieved by adjusting the doping concentration of single activated ions Eu³⁺in single phase matrix triply?YF₃?doped Dy³⁺,Tb³⁺and Eu³⁺.