| Up-conversion luminescent materials based on rare earth utilize NIR laser as their excitation,and emit visible light or ultraviolet light.Compared with the traditional luminescent materials,up-conversion materials are suitable for applications in the field of biomedicine,because it can effectively avoid the interference of ?autologous-luminescence? by its valuable conversion characersitics of light.In addition,NIR locates in ?optical window? of tissues and has the advantages of deep penetration and low damage in biological tissue.However,due to the multi-photons absorption process,up-conversion materials suffer from the drawback of low luminescent efficiency,which limits their extensive application in biological imaging and photodynamic therapy.Thus,how to improve the luminescent effeiency and luminescent intensity of up-conversion materials is one of urgent issues.In response of the situation mentioned above,we prepared and studied novel rare-earth-based upconversion luminescent materials with inorganic or MOF structure.Moreover,Eu-doped ?cluster-structured? complexes with high-effective luminescence were synthesized and characterized.Major achievements are presented specifically as follow:1.Plasmon enhanced luminescence and mechanism in Core–Spacer–Shell structured upconversion nanoparticles.In order to enhance the luminescent intensity of the upconversion materials,we constructed a kind of up-conversion nanoparticles(UCNPs)with core-spacer-shell structure.The NaGd F4:Yb/Er UCNPs were selected as the upconversion luminescent core.On basis of the core,NaGdF4 spacer with a thickness of 2 nm was prepared to cover the core.And then the UCNPs were covered with a silver shell with a thickness of about 1.5 nm.The core-spacer-shell structured UCNPs were obtained.It is found that the existence of the spacer with appropriate thickness can effectively control the distance between silver shell and the luminescence center in core.Benefit from the synergistic effect of Localized Surface Plasmon Resonance of Ag shell and the homogeneous coating of NaGdF4,the core-spacer-shell structred UCNPs achieved enhanced upconversion luminescence which is about 12 times higher than that of the initial core-UCNPs.2.Metal-Organic Frameworks modulated by doping Er3+ for up-conversion luminescence.The Up-MOF-Y1-x/Erx up-conversion materials,which have characteristic upconversion luminescence of Er,were prepared by the one-step method.When the concerntration of Er is 6%(x = 6%),the Up-MOF has the maximum intensity of upconversion emission,and then with the increasing of concentration of Er,the intensity greatly declines due to concentration quenching effect.By studying the luminescent properties,we presume that the upconversion mechanism is excited state absorption mode.Taking account of the relationship between upconversion intensity and excitation power,the number of photons absorbed in the upconversion process is calculated to 2.In addition,the function of drug release in porous MOF material is also verified.3.Preparation,characterization and photochemical sensing performance of cluster-structured luminescent materials doped with rare earth.By upgrading the reaction temperature,cluster-structured luminescent compound doped with rare earth Eu was prepared.Compared to La(1,3,5-BTC)· 6H2O(CCDC: 290771)reported previously which has same component,luminescent intensity of this compound increased by nearly 10 times.And this material has ability of sensing Fe3+ among a series of metal ions and acetone among a series of organic small molecules respectively.And it can distinguish a variety of nitroaromatic explosives by the extent of quenching effect.The material has multi-functional ability in sensing. |
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