Stable and Efficient Blue-Emitting CsPbBr3 Nanoplatelets with Potassium Bromide Surface Passivation.

Colloidal all-inorganic perovskites nanocrystals (NCs) have emerged as a promising material for display and lighting due to their excellent optical properties. However, blue emissive NCs usually suffer from low photoluminescence quantum yields (PLQYs) and poor stability, rendering them the bottleneck for full-color all-perovskite optoelectronic applications. Herein, a facile approach is reported to enhance the emission efficiency and stability of blue emissive perovskite nano-structures via surface passivation with potassium bromide. By adding potassium oleate and excess PbBr2 to the perovskite precursor solutions, potassium bromide-passivated (KBr-passivated) blue-emitting (≈450 nm) CsPbBr3 nanoplatelets (NPLs) is successfully synthesized with a respectably high PLQY of 87%. In sharp contrast to most reported perovskite NPLs, no shifting in emission wavelength is observed in these passivated NPLs even after prolonged exposures to intense irradiations and elevated temperature, clearly revealing their excellent photo- and thermal-stabilities. The enhancements are attributed to the formation of K-Br bonding on the surface which suppresses ion migration and formation of Br-vacancies, thus improving both the PL emission and stability of CsPbBr3 NPLs. Furthermore, all-perovskite white light-emitting diodes (WLEDs) are successfully constructed, suggesting that the proposed KBr-passivated strategy can promote the development of the perovskite family for a wider range of optoelectronic applications.

Switchable and Scalable Heteroarylation of Primary Amines with 2-Chlorobenzothiazoles under Transition-Metal-Free and Solvent-Free Conditions.

2-Aminobenzothiazoles comprise a valuable structural motif, which prevails in versatile natural products and biologically active compounds. Herein, a switchable and scalable C-N coupling protocol was developed for the synthesis of these compounds from 2-chlorobenzothiazoles and primary amines. Gratifyingly, this protocol was achieved under transition-metal-free and solvent-free conditions. Moreover, introducing an appropriate amount of NaH completely switched the selectivity from mono- toward di-heteroarylation, and further investigations provided a rationale for this new finding. Furthermore, gram-scale synthesis of representative products 3a and 4a was realized by applying operationally simple and glovebox-free procedures, which revealed the practical usefulness of this work. Finally, evaluation of the quantitative green metrics provided evidence that our protocol was superior over the literature ones in terms of green chemistry and sustainability.

Optical puff mediated laminar-turbulent polarization transition.

Various physical structures exhibit a fundamentally probabilistic nature over diverse scales in space and time, to the point that the demarcation line between quantum and classic laws gets blurred. Here, we characterize the probability of intermittency in the laminar-turbulence transition of a partially mode-locked fiber laser system, whose degree of coherence is deteriorated by multiple mode mixing. Two competing processes, namely the proliferation and the decay of an optical turbulent puff, determine a critical behavior for the onset of turbulence in such a nonlinear dissipative system. A new kind of polarization rogue waves is introduced at the point of transition to polarization turbulence. The probabilistic description of the puff-mediated laminar-turbulence polarization transition provides an additional degree of freedom for our understanding of the complex physics of lasers.

1.6 µm dissipative soliton fiber laser mode-locked by cesium lead halide perovskite quantum dots.

We demonstrate a stable, picosecond fiber laser mode-locked by cesium lead halide perovskite quantum dots (CsPbBr3-QDs). The saturable absorber is produced by depositing the CsPbBr3-QDs nanocrystals onto the endface of a fiber ferrule through light pressure. A balanced two-detector measurement shows that it has a modulation depth of 2.5% and a saturation power of 17.29 MW/cm2. After incorporating the fabricated device into an Er3+-doped fiber ring cavity with a net normal dispersion of 0.238 ps2, we obtain stable dissipative soliton with a pulse duration of 14.4 ps and a center wavelength at 1600 nm together with an edge-to-dege bandwidth of 4.5 nm. The linear chirped phase can be compensated by 25 m single mode fiber, resulting into a compressed pulse duration of 1.046 ps. This experimental works proves that such CsPbBr3-QDs materials are effective choice for ultrafast laser operating with devious mode-locking states.

Highly active bidentate N-heterocyclic carbene/ruthenium complexes performing dehydrogenative coupling of alcohols and hydroxides in open air.

Eight bidentate NHC/Ru complexes, namely [Ru]-1-[Ru]-8, were designed and prepared. In particular, [Ru]-2 displayed extraordinary performance even in open air for the dehydrogenative coupling of alcohols and hydroxides. Notably, an unprecedentedly low catalyst loading of 250 ppm and the highest TON of 32 800 and TOF of 3200 until now were obtained.

Gene transfer using self-assembled ternary complexes of cationic magnetic nanoparticles, plasmid DNA and cell-penetrating Tat peptide.

Nonviral magnetofection facilitates gene transfer by using a magnetic field to concentrate magnetic nanoparticle-associated plasmid delivery vectors onto target cells. In light of the well-established effects of the Tat peptide, a cationic cell-penetrating peptide, that enhances the cytoplasmic delivery of a variety of cargos, we tested whether the combined use of magnetofection and Tat-mediated intracellular delivery would improve transfection efficiency. Through electrostatic interaction, gene transfer complexes were generated by mixing polyethylenimine-coated cationic magnetic iron beads with plasmid DNA, followed by addition of a bis(cysteinyl) histidine-rich Tat peptide. These ternary magnetofection complexes provided a 4-fold improvement in transgene expression at a dose of 1 microg of plasmid DNA per 20,000 cells over the binary complexes without the Tat peptide and transfected up to 60% of cells in vitro. The enhanced transfection efficiency was also observed in vivo in the rat spinal cord after lumbar intrathecal injection. Moreover, the injected ternary magnetofection complexes in the cerebrospinal fluid responded to a moving magnetic filed by shifting away from the injection site and mediating transgene expression in a remote region. Thus, our approach could potentially be useful for effective gene therapy treatments of localized diseases.