چكيده به لاتين
In this research, Y2O3:RE3+ (RE: Eu3+; Tb3+; Tb3+/Yb3+, Tm3+/Yb3+) nanocrystalline particles with downconversion (DC) and upconversion (UC) photoluminescence characteristics are successfully synthesized by novel microwave assisted co-precipitation method in less than 10 min. This synthesis method is surfactant free and urea is used as precipitating agent. Fast microwave heating and controlled decomposition of urea led to the formation of non-aggregated spherical particles. The particle size and size dispersion are controlled by adjusting the different reaction parameters such as urea concentration, metal ions concentration, reaction time and temperature and spherical particles with different particle size between 60 nm and 550 nm are synthesized. The as prepared particles have (Y,RE)(OH)CO3 structure, which converts to cubic Y2O3:RE3+ after calcination at temperatures above 500°C. The effect of calcination temperature, particle size, dopant type and concentration on the structural, microstructural and optical properties of Y2O3:RE3+ particles is investigated. It is observed that the calcined nanoparticles are polycrystalline and the crystallite size is independent on the doping element type and concentration but dependent on the calcination temperature. The crystallite size is increased from 15 nm to 25 nm as the calcination temperature increased from 700 °C to 1050 °C. Under UV excitation, Y2O3:Eu3+ and Y2O3:Tb3+ nanoparticles exhibit a strong red emission at 613 nm and green emission at 489 nm, respectively. The DC photoluminescence intensity increases proportionally with calcination temperature and dopant concentration. Furthermore, the luminescence quenching has not been observed for Y2O3:Eu3+ nanoparticles till 13 mol% Eu3+ concentration and for Y2O3:Tb3+ nanoparticles till 3 mol% Tb3+ concentration. Upon NIR excitation, Y2O3:Tb3+,Yb3+ and Y2O3:Tm3+,Yb3+ nanoparticles exhibit intense green and blue UC emission, respectively. Cooperative energy transfer (CET) from sensitizer ions (Yb3+) to activator ions (Tb3+ or Tm3+) is the dominant mechanism for UC. The fluorescent emission properties combined with the spherical morphology, monodispersity and narrow size distribution characteristics make the Y2O3:RE3+ nanophosphors applicable in fluorescence cell imaging and as fluorescence bio labels.
