| Rare earth (RE) doped nano-material exhibits different luminescent properties. It possesses the advantages of the RE's excellent luminescence and the effects of a nano-system host. Comparing with the buck material, the fluorescent properties, upconversion, radiative and non-radiative relaxation, energy transfer, concentration quenching effect in a nano-material doped with RE would be largely changed, which is due to the influence of the surface, confinement effect of the local environment. In the current dissertation, the upconversion in the Tm3+-doped oxyfluoride glass, transparent glass ceramic embedded with LaF3 nanocrystals, Tin3+:LaF3 nano- and micron-crystals were investigated. The influences of the excitation lights on the upconversion process in different matrix types were also discussed. Additionally, the influence of Ln3+ codopant ion on the enhancement of the red fluorescent emission of Ln3+/Eu3+:LaOF nanocrystals and the energy transfer effect of Sm3+/Eu3+ in LaF3 and LaOF nanocrystal particles were investigated, respectively. The dissertation mainly includes four parts.Part one:The nano- and micron-sized crystal particles with the concentration of 1.0 mol% and 3.0 mol% were prepared by a hydrothennal method. The two DCM dye lasers pumped with two Nd3+:YAG pulsed lasers were served as the excitation sources to output the tunable lights around 650 nm. The upconversions of Tm3+ion arising from ESA were implemented in nano- and micron-sized crystals by means of the two-photon resonant excitation, and the fluorescence around 365 nm and 453 nm corresponding to the transitions of1D2→3H6 and 1D2→3F4 were observed successfully. The relations between the intensity of the upconversion fluorescence and the delay interval of the two pulsed excitation lights were recorded. The information of the non-radiative relaxation of 3F2→3H4 and radiative relaxation of 3H4→3H6 were extracted from the relations. The influences of confinement and concentration effects on the two relaxation processes were discussed. It was shown that the non-radiative relaxation rate of 3F2→3H4 in nanocrystal was less than that of the micron-sized one, but the Tm3+ concentration hardly affected it. For the nano- and micron-crystals with the concentration of 3.0 mol% exhibited a quicker radiative relaxation rate than that of the crystals with 1.0 mol%, but the concentration had less effect on the non-radiative relaxation rate. Consequently, the confinement mainly affects the non-radiative relaxation rate, while the concentration mostly influences the radiative relaxation rate. Based on this experimental study and theoretic analysis, an effective new way to obtain the information in time domain via a spectroscopic measurement in frequency domain is proposed. Part two:The upconversion mechanisms and characteristics of the Tm3+-doped in different host were analyzed when the Tm3+ was excited by a cw, a single pulsed and the double pulsed lights. The influence of the local environment, size of nanoparticels, local temperature, and excitation lights on the luminescence properties and non-radiative relaxation of 3F2→3H4 transition were investigated. The upconversion could be implemented in Tm3+-doped glass and LaF3 when the sample was pumped with a cw light, but the information of the non-radiative relaxation could not be detected. And the upconversion could be observed successfully in many kinds of glass or glass-ceramics hosts under the excitation with a pulsed light. The relations between the non-radiative relaxation and the temperature were obtained from the buildup the upconversion fluorescence. The non-radiative relaxation rates in Tm3+:LaF3 nano- and micron-crystals under the two-color pulsed excitation technique were in agreement with what obtained with single pulsed excitation light. Finally, the influence of the three excitation techniques on the emission spectra profiles of the Tm3+-doped the four different hosts were discussed.Part three:The nanoparticles of Eu3+:LaOF and Ln3+/Eu3+:LaOF were prepared by a hydrothermal-sintering method, and the influences of Ln3+ codopant in the host on the 610 nm fluorescent emission were investigated. It was shown that the emission intensities could be enhanced when a Ln3+ codopant, not including Nd3+ was introduced into the system. The enhancement of the fluorescent intensities were increased up to ten times than that of Eu3+:LaOF when the Gd3+,Dy3+ and Tm3+ were co-doped in the system, additionally the monochromaticities of the fluorescent emission of the co-doped systems were also improved. The reasons behind the phenomena were also discussed, and it is an effective way to obtain luminescence materials with excellent red emission.Part four:The two types of nanocrystal particles, that is Sm3+:LaF3, Eu3+:LaF3, Sm3+/Eu3+:LaF3 and Sm3+:LaOF, Eu3+:LaOF, Sm3+/Eu3+:LaOF with different concentrations were prepared by a hydrothermal-sintering method. The fluorescence properties of Sm3+/Eu3+ codoped in both LaF3 and LaOF were investigated under the excitation with 442 nm. The energy transfers from Sm3+ to Eu3+ were observed in the codopant systems, and their mechanisms were also analyzed. The influences of the Eu3+ concentration and the size of nanoparticles on the energy transfer effect were investigated by means of spectroscopic technique. The intensity of the fluorescence arising from Eu3+ was enhanced with the increase of the Eu3+ concentration. For the nano-scaled region, the big size of the particle has higher energy transfer efficiency than the small ones.
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