Study On Preparation And Luminescence Property Of Coreshell Structured Rare Earth Nanoparticles

In this paper, polyhydric alcohol was used as the solvent, rare earth chloride as the raw material and Na OH as the precipitator, with continuously magnetic stirring rare earth ion doped spherical Gd2O3 nano core particles were synthesised, then by the hydrolysis and condensation of TEOS and APTES, a polysiloxane shell was generated on the surface of Gd2O3 leading to the formation of core-shell structured Gd2O3: Tb3+/SiOx nanoparticles. The encapsulation of shell can stabilize the nanoparticles and help grafting biological molecules on it for the further biomedical applications. In order to synthesis Gd2O3: Tb3+/SiOx with excellent luminescence properties, the influence of different RE3+(Tb3+ and Eu3+) doping ions were firstly investigated followed by the study of different encapsulation ratio and different PEG solvent. By Malvern laser granulometer, TEM, SEM and fluorescence spectra, the products’ size distribution, morphology and luminescence properties were characterized. Results showed that:(1) The emission peaks of Eu3+ and Tb3+ co-doped Gd2O3 are located at 545 nm and 612 nm, when the mole doping concentration of Tb3+ is fixed at 5%, with the increasing doping concentration of Eu3+, the emission intensity of both two peaks increased and reached the maximum when Eu3+ doping concentration is 2%, when above 2%, the intensity begins to decrease which indicated the existence of energy transfer from Eu3+ to Tb3+ and the quenching concentration of Eu3+ is 2%.When the mole concentration of Eu3+ is fixed at 2%, with the increasing doping concentration of Tb3+, the intensity of 545 nm emission peak increased and reached the maximum when Tb3+ concentration is 5%, when above 5%, the intensity begins to decrease which indicated the quenching concentration of Tb3+ is 5%. However, with the increasing Tb3+ doping concentration the intensity of 612 nm emission peak decreased which proved the energy transfer from Eu3+ to Tb3+. So we come into a conclusion that Gd2O3:5%Tb3+,2%Eu3+ has the optimized luminescent property。(2)The bigger encapsulation ratio, the greater the particles size and the shell thickness. With the increasing of encapsulation ratio, the luminescence intensity decreased first then increased and reached maximum at a ratio of 4:1, beyond this ratio the luminescence intensity began to decrease again. So with a ratio of 4:1, Gd2O3: Tb3+/SiOx obtain best luminescent performance.(3) Size distribution of Gd2O3:Tb3+/SiOx prepared in different PEG solvent differs a lot, during which PEG200 facilitate the nanoparticles’ growth the most. With the increase of particle size, excitation and emission intensity both increased.