The instability of metal halide perovskites upon exposure to moisture or heat strongly hampers their applications in optoelectronic devices. Here, we report the large-yield synthesis of highly water-resistant total-inorganic green luminescent CsPbBr 3 /CsPb 2 Br 5 core/shell heteronanocrystals (HNCs) by developing an in situ phase transition approach. It is implemented via water-driven phase transition of the original monoclinic CsPbBr 3 nanocrystal and the resultant tetragonal CsPb 2 Br 5 nanoshell has small lattice mismatch with the CsPbBr 3 core, which ensures formation of an epitaxial interface for the yielded CsPbBr 3 /CsPb 2 Br 5 HNCs.These HNCs maintain nearly 100% of the original luminescence intensity after immersion in water for eleven months and the luminescence intensity drops only to 81.3% at 100 °C. The transient luminescence spectroscopy and density functional theory calculation reveal that there 1 are double radiative recombination channels in the core CsPbBr 3 nanocrystal, and the electron potential barrier provided by the CsPb 2 Br 5 nanoshell significantly improves the exciton recombination rate. A prototype quasi-white light-emitting device based on these robust CsPbBr 3 /CsPb 2 Br 5 HNCs is realized, showing their strong competence in solid-state lighting and wide color-gamut displays.

Single atom catalysts (SACs) harbor a potential to exceed nanoparticle catalysts in terms of activity, stability and selectivity in a growing number of chemical reactions. Although their investigation is attracting significant attention, important fundamental questions focusing on key physicochemical properties of SACs (e. g., structure -property relationships, structural dynamics, reaction-driven restructuring) remain unanswered. A main challenge for research in the field is how to reliably characterize the environments of single atoms in the presence of complicating factors such as low weight loadings, strong metal-support interactions, and atomic and multiscale hetero-geneity of bonding in the single atom sites. This review addresses this challenge -identifying catalytically relevant features of physicochemical properties of single atoms (charge state, electronic structure, atomic configuration, bonding interactions with a support) and surveying advanced tools/methods for characterizing them. The review places a strong emphasis on multimodal methods exploiting X-ray absorption, emission and photoelectron spectroscopies, and provides several examples from the authors' research that demonstrate their use as powerful tools for SAC characterization.

The oxidation of methane to methanol is a pathway to utilizing this relatively abundant, inexpensive energy resource. Here we report a new catalyst, bent mono(μ-oxo)dinickel anchored on an internal surface of micropores,which is active for direct oxidation. It is synthesized from the direct loading of a nickel precursor to the internal surface of micropores of ZSM5 following activation in O2. Ni 2p3/2 of this bent mono(μ-oxo)dinickel species formed on the internal surface of ZSM5 exhibits a unique photoemission feature, which distinguishes the mono(μ-oxo)dinickel from NiO nanoparticles. The formation of the mono(μ-oxo)dinickel species was confirmed with X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). This mono(μ-oxo)dinickel species is active for the direct oxidation of methane to methanol under the mild condition of a temperature as low as 150 °C in CH4 at 1 bar. In-situ studies using UV-vis, XANES, and EXAFS suggest that this bent mono(μ-oxo)dinickel species is the active site for the direct oxidation of methane to methanol. The energy barrier of this direct oxidation of methane is 83.2 kJ/mol.

The zero-dimensional perovskites composed of isolated polyhedrons have unique and distinct physical properties compared with threedimensional perovskites composed of interconnected polyhedrons. Here, we study the photodynamics of the zero-dimensional perovskite-like (C 6 H 22 N 4 Cl 3 )-SnCl 3 single crystals composed of isolated [SnCl 3 ] − tetrahedrons. They exhibit red luminescence with huge Stokes shift (2.49 eV), large spectral broadening (416 meV), and long lifetime (6.9 μs). The experiments in conjunction with the ab initio calculations reveal the special roles of high-and low-frequency phonons in the photodynamics of the (C 6 H 22 N 4 Cl 3 )SnCl 3 crystals. The resonance between the organic-cation-related high-frequency optical phonons and the singlet-totriplet state transition induces strong intersystem crossing and resultant spinforbidden luminescence. The strong electron−tetrahedron-related low-frequency optical-phonon coupling revealed by the low-temperature spectral characterization causes large spectral broadening. The strong lattice relaxation owing to localization of the electronic orbitals along with intersystem crossing accounts for the large Stokes shift.

<p>ClNO<sub>2</sub> and Cl<sub>2</sub> can affect atmospheric oxidation and thereby the formation of ozone and secondary aerosols, yet their sources and production mechanisms are not well understood or quantified. In this study we present field observations of ClNO<sub>2</sub> and Cl<sub>2</sub> at a suburban site in eastern China during April 2018. Persistent high levels of ClNO<sub>2</sub> (maximum ~3.7 ppbv; 1 min average) were frequently observed at night, due to the high ClNO<sub>2</sub> yield (φ(ClNO<sub>2</sub>), 0.56 ± 0.20) inferred from the measurements. The φ(ClNO<sub>2</sub>) value showed a positive correlation with the [Cl<sup>-</sup>]/[H<sub>2</sub>O] ratio, and its parameterization was improved by the incorporation of [Cl<sup>-</sup>]/[H<sub>2</sub>O] and the suppression effect of aerosol organics. ClNO<sub>2</sub> and Cl<sub>2</sub> showed a significant correlation on most nights. We show that the Cl<sub>2</sub> at our site was likely a co-product with ClNO<sub>2</sub> from N<sub>2</sub>O<sub>5</sub> uptake on aerosols that contain acidic chloride, rather than being produced by ClNO<sub>2</sub> uptake, as previously suggested. The Cl<sub>2</sub> yield (φ(Cl<sub>2</sub>)) derived from the N<sub>2</sub>O<sub>5</sub> uptake hypothesis exhibited significant correlations with [Cl<sup>-</sup>] and [H<sup>+</sup>], based on which a parameterization of φ(Cl<sub>2</sub>) was developed. The derived parameterizations of φ(ClNO<sub>2</sub>) and φ(Cl<sub>2</sub>) can be used in models to quantify the nighttime production of ClNO<sub>2</sub> and Cl<sub>2</sub> and their impact on the next day’s photochemistry.</p>