Bei Zhao,Li Yuan,Shanshan Hu,Xuemei Zhang,Xianju Zhou,Jianfeng Tang,Jun Yang
Novel chocolate-like scandium molybdate precursors with exposed {001} facets were hydrothermally synthesized in the presence of PVP, which were transformed into morphology-preserved Sc2Mo3O12 crystals by calcination at 800 °C for 2 h. The as-synthesized samples were characterized by XRD, FT-IR SEM, TEM, HRTEM, and PL analysis. Four different types of precursors including prismatic structures, octahedra, truncated octahedra and compressed decahedra could be obtained by varying the amount of MoO42−. Moreover, in the presence of H+, the percentage of high-energy {001} facets could be enhanced. The Mo sources, PVP consumption, reaction time and hydrothermal temperature had significant influences on the morphology of the precursors. As good matrix materials, the tunable down/upconversion (DC/UC) luminescence properties of Sc2Mo3O12:Ln3+ (Ln = Tb, Eu, Tb/Eu, Yb/Er, Yb/Ho, Yb/Tm) were comprehensively investigated. It is found that the materials showed strong morphology-dependent luminescence properties. Particularly, the energy transfer (ET) of MoO42− → Tb3+ → Eu3+ resulted in multicolor emissions from green to red in Sc2Mo3O12:5%Tb3+,x%Eu3+. The Sc2Mo3O12:Ln3+ (Ln = Tb, Eu, Tb/Eu, Yb/Er, Yb/Ho, Yb/Tm) microcrystals show great potential applications in the areas of fluorescent lamps and color displays.
Artem Yakovliev,Tymish Y. Ohulchanskyy,Roman Ziniuk,Tereza Dias,Xin Wang,Hao Xu,Guanying Chen,Junle Qu,Anderson S. L. Gomes
In this work, the application of near infrared (NIR)-emitting NaYbF 4 :1%Tm 3+ @NaLuF 4 :30%Nd 3+ core–shell nanoparticles is reported for noninvasive probing and monitoring the temperature during photopolymerization of dental materials. When excited at 808 nm, the synthesized nanoparticles emit NIR photoluminescence (PL) with two distinctive peaks at 865 and 980 nm which correspond to radiative transitions from the doped Nd 3+ and Yb 3+ ions, respectively. Luminescence intensity ratio between these two bands is found to vary with temperature due to temperature-dependent electronic excitation energy transfer between Nd 3+ and Yb 3+ ions at the core/shell interface. This finding allows luminescence ratiometric evaluation of the in situ temperature during photopolymerization of resin cement (doped with nanoparticles) in a veneer placement procedure. In addition, the NIR emission also enables PL imaging of the distribution of the adhesive under the veneer. The results highlight that rare-earth ions–doped nanoparticles with both excitation and emission in the NIR spectral range are advantageous for both PL-based nanothermometry and imaging due to the reduced attenuation of NIR light by dental ceramics.
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