Synthesis and characterization of tunable color upconversion luminescence beta-NaGdF4: Yb3+,Er3+ nanoparticles - Khan, Latif Ullah; Khan, Zahid Ullah; Rodrigues, R. V.; Costa, L. S.; Gidlund, Magnus Ake; Brito, Hermi Felinto de (Journal of Materials Science: Materials in Electronics, 2019)