Rare earth (RE3+)-doped phosphors generally suffer from thermal quenching, in which their photoluminescence (PL) intensities decrease at high temperatures. Herein, we report a class of unique two-dimensional negative-thermal-expansion phosphor of Sc2(MoO4)3:Yb/Er. By virtue of the reduced distances between sensitizers and emitters as well as confined energy migration with increasing the temperature, a 45-fold enhancement of green upconversion (UC) luminescence and a 450-fold enhancement of near-infrared downshifting (DS) luminescence of Er3+ are achieved upon raising the temperature from 298 to 773 K. The thermally boosted UC and DS luminescence mechanism is systematically investigated through in situ temperature-dependent Raman spectroscopy, synchrotron X-ray diffraction and PL dynamics. Moreover, the luminescence lifetime of 4I13/2 of Er3+ in Sc2(MoO4)3:Yb/Er displays a strong temperature dependence, enabling luminescence thermometry with the highest relative sensitivity of 12.3%/K at 298 K and low temperature uncertainty of 0.11 K at 623 K. These findings may gain a vital insight into the design of negative-thermal-expansion RE3+-doped phosphors for versatile applications.

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By utilizing the proportional relationship between the excitation and absorption spectra for some special excited multiplets of rare-earth (RE) ions that are followed by a very fast nonradiative relaxation to the monitored level, we propose a new approach to determine the Judd-Ofelt (JO) intensity parameters that are crucial to the evaluation of laser and luminescent materials via excitation spectra. To validate this approach, the JO parameters of NaGd(WO(4))(2) : Er(3+) and YLiF(4) : Nd(3+) crystals are calculated and compared through both the excitation and absorption spectra. The JO parameters derived from this approach are in good agreement with that determined from the conventional method (absorption spectra). Furthermore, the JO intensity parameters of Y(2)O(3) : Er(3+) nanocrystals are derived from the excitation spectra by taking into account the nano-size effects, which are comparable to the values of the crystal counterpart. The proposed approach is of particular importance for those powders or nanophosphors with low RE doping concentration that their quantitative absorption spectra are difficult to measure.

A family of chiral 3d−4f heterometallic complexes, namely, [Zn 2 Ln(R,R-L) 2 (H 2 O) 4 ](ClO 4 ) 3 ) [Ln = Dy (1), Tb ( 3 5), Tb (7)], and [Zn 2 Ln 2 (S,S-L) 2 (CO 3 ) 2 (NO 3 ) 2 ]•2CH 3 OH [Ln = Dy (6), Tb (8)] {H 2 L = cyclohexane-1,2-diylbis(azanediyl)bis-(methylene)bis(2-methoxyphenol)}, has been synthesized and characterized. Crystal structure analysis reveals that complexes 1− 4 are isostructural trinuclear clusters crystallized in chiral space group C2 2 2 1 , and 5−8 are isostructural tetranuclear clusters crystallized in chiral space group P1. Interestingly, the adjacent [ZnLn] units within the tetranuclear cluster in 5−8 are bridged by two carbonate anions via in situ incorporation of CO 2 from air. Magnetic measurements indicate that complexes 1 and 3 exhibit field-induced single-molecule magnet behavior with energy barriers (U eff ) of 22.46 and 38.70 K (or 41.87 K), respectively. Complex 5 displays typical SMM behavior with U eff = 19.61 K under zero dc field, while for complex 7, no obvious out-of-phase signals are observed even under 2 kOe dc field, the absence of SMM behavior. The solid-state luminescence studies reveal that all complexes display the characteristic fluorescence emission of lanthanide ions. Furthermore, the Kurtz−Perry measurements reveal these complexes are potential nonlinear optical materials.