Preparation and upconversion property of TeO2:Er3+/Yb3+ nanoparticles

Different crystal structure of TeO 2 nanoparticles were used as the host materials to prepare the Er 3+ /Yb 3+ ions co-doped upconversion luminescent materials. The TeO 2 nanoparticles mainly kept the original morphology and phase after having been co-doped the Er 3+ /Yb 3+ ions. All the as-prepared TeO 2 :Er 3+ /Yb 3+ nanoparticles showed the green emissions (525   nm, 545   nm) and red emission (667   nm) under 980   nm excitation. The green emissions at 525   nm, 545   nm and red emission at 667   nm were attributed to the 2 H 11/2   →   4 I 15/2 , 4 S 3/2   →   4 I 15/2 and 4 F 9/2   →   4 I 15/2 transitions of the Er 3+ ions, respectively. For the α-TeO 2 :Er 3+ /Yb 3+ (3/10   mol%) nanoparticles, three-photon process involved in the green ( 2 H 11/2   →   4 I 15/2 ) emission, while two-photon process involved in the green ( 4 S 3/2 → 4 I 15/2 ) and red ( 4 F 9/2   →   4 I 15/2 ) emissions. For the β-TeO 2 :Er 3+ /Yb 3+ (3/10   mol%) nanoparticles, two-photon process involved in the green ( 2 H 11/2   →   4 I 15/2 ), green ( 4 S 3/2   →   4 I 15/2 ) and red ( 4 F 9/2   →   4 I 15/2 ) emissions. It suggested that the crystal structure of TeO 2 nanoparticles had an effect on transition processes of the Er 3+ /Yb 3+   ions. The emission intensities of the α-TeO 2 :Er 3+ /Yb 3+ (3/10   mol%) nanoparticles and β-TeO 2 :Er 3+ /Yb 3+ (3/10   mol%) nanoparticles were much stronger than those of the (α   +   β)-TeO 2 :Er 3+ /Yb 3+ (3/10   mol%) nanoparticles.