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Quantum‐dot light‐emitting diodes (QLEDs) have been considered the next‐generation display. However, the toxicity of Cd or Pb in these quantum dots (QDs) and the low performance of blue QLEDs remain critical issues, which greatly limit their sustainable development. Herein, first blue‐emitting quantum‐dot light‐emitting diode based on orthorhombic BN QDs with high photoluminescence quantum yield (PLQY) of 31.3% and electroluminescence at 437 nm is reported. With optimal solvothermal parameters, high photoluminescence quantum yield (PLQY) of 31.3% can be realized in the as‐synthesized BN QDs. The turn‐on voltage, maximum luminance, and maximum current density of these novel QLEDs are 9 V, 6.55 Cd m−2, and 34.42 mA cm−2, respectively. This work demonstrates that BN QDs have great potential for blue QLEDs with advantages of being nontoxic, Earth abundant, and having low‐cost manufacturing.

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Novel near-infrared (NIR) phosphors are in demand for light-emitting diode (LED) devices to extend their suitability for new applications and, in turn, support the sustainable and healthy development of the LED industry. The Cr3+ has been used as an activator in the development of new NIR phosphors. However, one main obstacle for the Cr3+-activated phosphors is the low luminescence efficiency due to the spin-forbidden d-d transition of Cr3+. The rare-earth (RE) huntite minerals that crystallize in the form of REM3(BO3)4 (M = Al, Sc, Cr, Fe, Ga) have a large family of members, including the rare-earth scandium borates of RESc3(BO3)4. Interestingly, in our research, we found that the luminescence efficiency of Cr3+ in the CeSc3(BO3)4 host, whose quantum yield was measured at 56%, is several times higher than that in GdSc3(BO3)4, TbSc3(BO3)4, and LuSc3(BO3)4 hosts. Hereby, the energy conversion and transfer in the luminescence of CeSc3(BO3)4:Cr3+ phosphor were examined. The Stokes shift of electron energy conversion within the Cr3+ 4T2g level for the emission at 818 nm and excitation at 625 nm in CeSc3(BO3)4 host was evaluated to be 3775.1 cm−1, and the super-large splitting energy of the 2F5/2 and 2F72 sub-states of the Ce3+ 4f1 state, about 3000 cm−1, was found in CeSc3(BO3)4 host. The typical electronic thermal vibration peaks were observed in the excitation spectra of CeSc3(BO3)4:Cr3+. On this basis, the smallest phonon energy, around 347.7 cm−1, of the CeSc3(BO3)4 host was estimated. Finally, the energy transfer that is responsible for the far higher photoluminescence of Cr3+ in CeSc3(BO3)4 than in other hosts was proven through the way of Ce3+ emission and Cr3+ reabsorption.

BackgroundPeritrichously flagellated bacteria such as Escherichia coli perform chemotaxis by a biased random walk toward various chemicals, which was driven by the bacterial flagellar motor. The chemotaxis system is a perfect robust system which can adapt to its pre-stimulus level after the stimulus. Fructose, a typical monosaccharide that can attract Escherichia coli. Previous studies have shown Escherichia coli to be chemotactic to both amino acids and simple sugars. However, little is known about the chemotaxis and motility response of Escherichia coli towards fructose.ResultsIn this study, we characterized the chemotaxis behavior of Escherichia coli to different concentrations of fructose from 0mM to 50mM by using microfluidics and bead assay. We observed the wild-type cells responded to the stimulus of fructose, which suggested fructose is an attractant to Escherichia coli, while the cells defective in chemotaxis could not sense the stimulus of fructose. Fructose affects the motor behavior of wild-type cells and reduces the CCW motor speeds significantly compared to CW motor speeds, contrast to that fructose cannot affect the motor speeds of cells defective in chemotaxis. The CW biases of wild-type cells increased with the addition of fructose. And the fructose promotes bacterial aggregation on surface by lowering the bacteria motor speed.ConclusionsWe found that fructose is an attractant to Escherichia coli, with the wild-type cells showed stronger response to higher concentration of fructose, while cells lacking chemoreceptors and CheY cannot sense or respond to fructose. The motility of wild-type cells was reduced in various concentrations of fructose, which helped the aggregation of cells near the surface, in contrast with the result that the fructose showed no effect on the motility of the cells defective in chemotaxis. Similar phenomena are expected to be found in the effect of other monosaccharides to Escherichia coli.