Nanocristais de ítria dopados com íons terras-raras: caracterização e aplicações luminescentes

Abstract

In this research the optical and structural characterization of Y2O3 luminescent nanoparticles is carried out. Effects of rare earth (Er3+, Eu3+ and Tb3+) co-doping on luminescence properties of the developed nanoparticles have been investigated under IR (800 nm) and UV excitation. Upon IR excitation intense infrared to red and green upconversion (UC) were identified and associated to Er3+(4F9/2 → 4I15/2), Eu3+(5D0 → 7F2) and Er3+(2H11/2 , 4S3/2 → 4 I15/2) emissions, respectively, while RGB components were obtained under UV excitation as a result of Tb3+(5D4 → 7FJ), Eu3+(5D0 → 7F2) and Er3+(4S3/2→ 4I15/2) transitions. Excited state absorption (ESA) and energy transfer (ET) mechanisms were proposed based on spectral and power dependence studies. We also used fluorescence intensity ratio (FIR) technique to study the optical heating behavior of nanophosphors (Y2O3:Er3+, Y2O3:Er3+ -Eu3+, Y2O3:Er3+-Tb3+ and Y2O3:Er3+-Eu3+-Tb3+) and temperature sensitivity of the upconverting green emissions of the Er3+ ions under 800 nm CW diode laser excitation. The experimental results indicate that the studied nanoparticles are promising candidates to applications such as photothermal treatments and hyperthermia. Finally, we successfully employed the nanoparticles doped with Tb3+ and Eu3+ ions to generate fluorescent images of latent fingerprints. In our studies, the developed nanoparticles were effective in producing fluorescent images of latent fingerprints in shades of green, red and yellow with high-contrast color under ultraviolet lighting.