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 CdWO 4 :Yb 3+ ,RE 3+ (RE = Ho and Er) micro/nanocrystallites, followed by calcination at 700 °C for 2 h. It was clearly demonstrated that Tar 2− restricted the exposed ab planes and 3D self-assembly of microplates, resulting in ∼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 Ho 3+ and Er 3+ , among which two CdWO 4 :Yb 3+ ,Ho 3+ phosphors generated orange-yellow fluorescence via three-photon processes, while CdWO 4 :Yb 3+ ,Er 3+ microflowers and nanoparticles showed yellowish-green and pale green colors, respectively. Moreover, nanoparticles intensified the dominant green DC emissions of Ho 3+ and Er 3+ by ∼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.