Crystallization and up-/down-conversion luminescence of size-dependent CdWO4:Yb3+,RE3+ (RE=Ho and Er)

Tartrate (Tar(2-)) was originally employed as a chelating/structure-directing agent for hydrothermal synthesis of CdWO4:Yb3+,RE3+ (RE = Ho and Er) micro/nanocrystallites, followed by calcination at 700 degrees C for 2 h. It was clearly demonstrated that Tar(2)- restricted the exposed ab planes and 3D self-assembly of microplates, resulting in similar to 50 nm sized nanoparticles. Up-/down-conversion (UC/DC) photoluminescence were revealed to be strongly size dependent. Under 978 nm pump laser excitation, flower-like assembly was found to exhibit the stronger UC emissions of Ho3+ and Er3+, among which two CdWO4:Yb3+,Ho3+ phosphors generated orange-yellow fluorescence via three-photon processes, while CdWO4:Yb3+,Er3+ microflowers and nanoparticles showed yellowishgreen and pale green colors, respectively. Moreover, nanoparticles intensified the dominant green DC emissions of Ho3+ and Er3+ by similar to 3 and 2 times, implying the pivotal roles of morphology engineering in tunable photoluminescence. This research may provide insights into crystallite/architecture engineering and luminescence optimization for near-infrared response solar cells and solid-state lighting.