Narrow-band red-emitting fluoride phosphors play a crucial role in lighting and backlight displays, whereas the stability issue is a major challenge. Here, highly stable K 2 SiF 6 :Mn 4+ (KSFM) single crystal phosphors with tunable sizes (20–1000 µ m) are grown by a facile saturated crystallization method. The small specific surface area together with the unique Mn 4+ -rare interface layer in KSFM single crystals enables the simultaneous fulfillment of high external quantum efficiency, excellent moisture, improved thermal quenching, and dissipation for high-power and laser-driven lighting applications. As a prototype, a warm white laser diode device with a high luminous flux of 202.7 lm and correlated color temperature of 3277 K, as well as a color rendering index of 87.9 is presented. This work provides new insights into the development of highly efficient and stable materials for advanced lighting applications.
Luo Zhishan,Wan Qiang,Yu Zhiyang,Lin Sen,Xie Zailai,Wang Xinchen
Styrene is one of the most important industrial monomers and is traditionally synthesized via the dehydrogenation of ethylbenzene. Here, we report a photo-induced fluorination technique to generate an oxidative dehydrogenation catalyst through the controlled grafting of fluorine atoms on nanodiamonds. The obtained catalyst has a fabulous performance with ethylbenzene conversion reaching 70% as well as styrene yields of 63% and selectivity over 90% on a stream of 400 °C, which outperforms other equivalent benchmarks as well as the industrial K−Fe catalysts (with a styrene yield of 50% even at a much higher temperature of ca. 600 °C). Moreover, the yield of styrene remains above 50% after a 500 h test. Experimental characterizations and density functional theory calculations reveal that the fluorine functionalization not only promotes the conversion of sp 3 to sp 2 carbon to generate graphitic layers but also stimulates and increases the active sites (ketonic C=O). This photo-induced surface fluorination strategy facilitates innovative breakthroughs on the carbocatalysis for the oxidative dehydrogenation of other arenes.
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