Tuning from green to red the upconversion emission of Y 2 O 3 :Er 3+ –Yb 3+ nanophosphors L. A. Diaz-Torres 1 • P. Salas 2 • J. Oliva 3 • E. Resendiz-L 2 • C. Rodriguez-Gonzalez 2 • O. Meza 4 Received: 20 October 2016 / Accepted: 8 December 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Abstract In this work, the structural, morphological and luminescent properties of Y 2 O 3 nanophosphors doped with Er 3? (1 mol%) and different Yb 3? concentrations (2–12 mol%) have been studied. Those nanophosphors were synthesized using a simple hydrothermal method. XRD analysis indicates that all the samples presented a pure cubic phase even for Yb concentrations as high as 12 mol%. In addition, SEM images show nanoparticles with quasi-spherical shapes with average sizes in the range of 300–340 nm. Photoluminescence measurements obtained after excitation at 967 nm revealed that our samples have strong green (563 nm) and red emissions (660 nm) corresponding to 2 H 11/2 ? 4 S 3/2 ? 4 I 15/2 and 4 F 9/2 ? 4 I 15/2 transitions of Er 3? ions, respectively. We also observed that the green band is quenched and the red emission enhanced as the Yb concentration increases. In consequence, the CIE coordinates changed from (0.35, 0.64) in the green region to (0.59, 0.39) in the red region. Thus, the tuning properties of Y 2 O 3 nanophosphors suggest that they are good candidates for applications in lighting. 1 Introduction In recent years, research on luminescent nanophosphors has attracted considerable attention due to their upcon- version properties which can be used for the development of upconversion lamps and solid-state lasers [1]. Several works about upconversion emission have been specially investigated in fluorides, oxides and oxysulfides doped with Er 3? , Eu 3? , Ho 3? , Tm 3? and Tb 3? [2–8]. Those doped nanophosphors with rare earth ions can be used for applications in color displays, bio-imaging [9], white LEDs [10], solar cells [11] and biotechnological applications [12, 13]. In the upconversion process, two infrared photons are absorbed by the luminescent material and it generates visible photons after multiphonon relaxation processes [14]. Particularly, yttrium oxide (Y 2 O 3 ) is considered a promising phosphor due to its high luminescent emission when it is doped with rare earth ions such as Yb 3? [15], Er 3? [16], Eu 3? [17] or codoped with Yb 3? –Er 3? [18–20]. Also, it has reported the fabrication of Er 3? , Tm 3? , and Yb 3? or Tm 3? , Ho 3? and Yb 3? tridoped Y 2 O 3 nanophos- phors where Yb 3? acts as a sensitizer (this ion transfers its energy to the activator ion which, in turn, emits a visible photon) for the enhanced intensity of blue, red and green emissions [19, 21–24]. Based on the reports mentioned above, the Y 2 O 3 host promotes the conversion of near infrared radiation (NIR) to VIS emission. Furthermore, some authors have investigated the luminescent properties of the crystallite yttrium oxide doped with rare earth ions such as Er 3? and Yb 3? . It has been reported Y 2 O 3 :Yb 3? – Er 3? nanophosphors prepared using CTAB via hydrother- mal synthesis for different ethanol/water ratios, and authors demonstrated that solvent ratios affect the morphology and luminescent properties of such nanophosphors [20]. Fur- thermore, Y 2 O 3 :Yb 3? –Er 3? nanophosphors have been & P. Salas psalas@fata.unam.mx 1 Grupo de Espectroscopia de Materiales Avanzados y Nanoestructurados (GEMANA), Centro de Investigaciones en O ´ ptica, A. P. 1-948, Leo ´n, GTO, Mexico 2 Centro de Fı ´sica Aplicada y Tecnologı ´a Avanzada, Universidad Nacional Auto ´noma de Me ´xico, Apartado Postal 1-1010, Quere ´taro, QRO, Mexico 3 Conacyt-Facultad Ciencias Quimicas Universidad Autonoma de Coahuila, 25000 Saltillo, Coahuila, Mexico 4 Instituto de Fı ´sica, Benemerita Universidad Autonoma de Puebla, A.P. J-48, 72570 Centro Histo ´rico, PUE, Mexico 123 Appl. Phys. A (2017) 123:25 DOI 10.1007/s00339-016-0668-5