Red, green, and blue upconversion luminescence of trivalent-rare-earth ion-doped Y2O3 nanocrystals

Trivalent-rare-earth ion-doped Y2O3 nanocrystals have been synthesized, and their photoluminescence properties have been studied under 980 nm laser diode excitation. The crystallite size estimated by x-ray diffractometry and scanning electron microscopy was about 30–40 nm. In Yb3+ and Tm3+ codoped Y2O3 nanocrystals, the bright blue emissions near 450 and 480 nm have been noticeable due to the 1D2–3F4 and 1G4–3H6 transitions of Tm3+, respectively. The bright green emissions of Er3+ doped Y2O3 nanocrystals appeared near 530 and 550 nm were assigned to the 2H11/2–4I15/2 and 4S3/2–4I15/2 transitions of Er3+, respectively. The ratio of the intensity of green luminescence to that of red luminescence has decreased with an increase of concentration of Yb3+ in Er3+ doped Y2O3 nanocrystals. In sufficient quantities of Yb3+ to Er3+, the bright red emission near 660 nm has been predominant due to the 4F9/2–4I15/2 transition of Er3+. The primary color components are in these red, green, and blue emissions, from which a wide spectrum of colors, including white, would be produced by appropriate mixing them.