Lead-Free Cesium Thulium Halide Perovskite Microcrystals for Near Ultraviolet Luminescence.

Lead halide perovskites attract tremendous research attention due to excellent optoelectronic properties. However, realizing efficient near ultraviolet (NUV) luminescence with these materials is still a big challenge. Herein, a novel rare-earth perovskite cesium thulium chloride (CsTmCl3 ) with high crystallinity has been synthesized via a simple hot-injection method. The obtained CsTmCl3 microcrystals have a size distribution of around 1-5 µm, and demonstrate a highly efficient NUV emission at 337 nm with a full width at half maximum (FWHM) of 68 nm. The determined band gap of CsTmCl3 microcrystals is ≈3.92 eV, which is supported by theoretical calculations. Moreover, a high photoluminescence quantum yield (PLQY) of up to 12% in NUV region has been achieved in such a lead-free perovskite. The findings suggest that CsTmCl3 perovskite microcrystal is a promising low-toxic material for applications in NUV optoelectronic devices.

Decomposition analysis of PM2.5 emissions based on LMDI and Tapio decoupling model: study of Hunan and Guangdong.

This paper takes energy consumption PM2.5 emission as research object, and quantitatively analyzes the PM2.5 emission level in Hunan and Guangdong provinces from 2012 to 2017. We build a PM2.5 emission decomposition model divided by five sectors, including industry, transportation, construction, resident, and other, and use attribution method and Tapio decoupling index to analyze the relationship between economic development and PM2.5 emission level. The results show that (1) the difference in PM2.5 emissions between the two provinces appeared in 2015; (2) the contribution rate of total PM2.5 emissions is 83.1%, and coal consumption is the determine factor of PM2.5 emissions; industry is the main source of sector contribution with rate of 70.91%; (3) Guangdong's pollution control capacity is much higher than that of Hunan, while Hunan's PM2.5 marginal emission-reduction potential is much higher than that of Guangdong; (4) economic growth is the first increasing emission reason of PM2.5 emission changes, while the intensity of industrial energy consumption is the first reduction emission reason; (5) there is a big difference between the economic development of the two provinces and the decoupling of PM2.5 pollution.

High-pressure Raman studies on aqueous protonated thiazole: presence of charge-enhanced C-H...O hydrogen bonds.

Close interactions of the charge-enhanced C-H...O type have been analyzed both experimentally and computationally in the protonated thiazole-water system. The formation of a weak hydrogen bond was directly evidenced by a low-frequency shift of the hydrogen-bonded aromatic C-H stretch in the protonated thiazole moiety. For pure thiazole, the pressure dependence of the C-H bands yielded blue frequency shifts. The peak frequency of the aromatic C-H stretch band of protonated thiazole in a dilute D2O solution possesses an unusual nonmonotonic pressure dependence, which indicates enhanced C-H...O hydrogen-bond formation at high pressure. We performed density functional theory calculations to predict the frequency shift of the C-H stretching vibrations. The reorganization of the hydrogen-bonded network may be one of the factors to induce the blue frequency shift to the red frequency shift.