Bright white-light emission and multicolor outputs in time domain from a core-shell structured microcrystal

Intense white-light color emission of lanthanide-doped core-shell structured particles at microscale level was presented under 980 nm excitation. The prepared NaYF 4 :Yb/Er@ NaYF 4 :Yb/Tm microcrystals not only can effectively prevent the deleterious cross-relaxation that occurs between the Er 3+ and Tm 3+ due to the location of the activator ions within different layers, but also possess a high luminescence efficiency due to dimensions of the micro-scale structure. The core-shell structured microcrystals presented satisfactory capacity for color control in the white region. The results show great potential in attaining white light-emitting diodes within the field emission display on specific device applications. Furthermore, the core-shell microcrystals emit white-light that presents obvious and distinct lifetimes of green, red, and blue emissions, which could achieve multicolor emissions by setting a suitable delay time. This feature demonstrates that the core-shell structured microrods offer practical use as security ink to prevent forgery, such as in identifying currency.