Inherent poor stability of perovskite nanocrystals (NCs) is the main impediment preventing broad applications of the materials. Here, TiO 2 shell coated CsPbBr 3 core/shell NCs are synthesized through the encapsulation of colloidal CsPbBr 3 NCs with titanium precursor, followed by calcination at 300 °C. The nearly monodispersed CsPbBr 3 /TiO 2 core/shell NCs show excellent water stability for at least three months with the size, structure, morphology, and optical properties remaining identical, which represent the most water-stable inorganic shell passivated perovskite NCs reported to date. In addition, TiO 2 shell coating can effectively suppress anion exchange and photodegradation, therefore dramatically improving the chemical stability and photostability of the core CsPbBr 3 NCs. More importantly, photoluminescence and (photo)electrochemical characterizations exhibit increased charge separation efficiency due to the electrical conductivity of the TiO 2 shell, hence leading to an improved photoelectric activity in water. This study opens new possibilities for optoelectronic and photocatalytic applications of perovskites-based NCs in aqueous phase.

A guest-induced reversible crystal-structure transformation is identified in a new 3D covalent organic framework (COF) by comprehensive analyses using powder X-ray diffraction, organic vapor sorption isotherm, and Xe NMR spectroscopy. The revolving imine bond in interpenetrating 3D networks is uncovered as the key to the dynamic behavior, the potential applications of which are illustrated by gas separation and heterogeneous catalysis, thus paving the way to the design of stimuli-responsive and multifunctional COF materials.

Molecular-based dye-sensitized photoelectrochemical cells (DSPECs) have traditionally targeted solar-driven water splitting for the conversion of solar energy into fuels in aqueous media. This work reports the use of a DSPEC-type photoanode specifically designed to carry out chemoselective oxidation of benzylic alcohol moieties in lignin model compounds and real lignin in organic media. The TiO 2 -based photoanode incorporates a surface-bound Ru(II)-based photocatalyst and solutiondissolved hydrogen atom transfer (HAT) co-catalyst to perform solar-driven photocatalytic oxidation of the lignin substrates. Under aerobic conditions with simulated solar illumination, conversion efficiencies in excess of 90% are observed for the formation of the oxidized ketone product from model compounds. The DSPEC half-cell exhibited impressive long-term durability, sustaining photocatalytic oxidation of the lignin model compound over a net illumination period of 80 h. This photoelectrochemical heterogeneous catalytic process provides a unique foundation to perform selective C−O bond cleavage for real lignin conversion technologies.

Halogenbrücken sind nichtkovalente Wechselwirkungen, in denen Halogenatome als elektrophile Spezies auftreten. Die Energien und geometrischen Charakteristika derartiger Bindungen werden im vorliegenden Kurzaufsatz beschrieben, und es wird diskutiert, welche Voraussetzungen Moleküle erfüllen müssen, um diese Wechselwirkungen eingehen zu können. Die Bildung von Halogenbrücken wirkt sich auf alle Forschungsgebiete aus, die durch molekulare Erkennung und Selbstorganisation bestimmt sind. Es werden einige Prinzipien für das Kristall‐Engineering mithilfe von Halogenbrücken vorgestellt. Das Potenzial derartiger Wechselwirkungen zeigt sich auch in Flüssigkristallen, magnetischen und leitfähigen Materialien sowie in biologischen Systemen.

Purpose To critically review and summarize the literature comparing the results of surgery via an anterior approach and that via a posterior approach for the treatment of thoracolumbar burst fractures to identify the better approach. Methods In this meta-analysis, we conducted electronic searches of MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials and other databases using the search terms ''thoracolumbar fractures'', ''anterior'', ''posterior'', ''controlled clinical trials''. Relevant journals or conference proceedings were also searched manually. Data extraction and quality assessment were in accordance with Cochrane Collaboration guidelines. The analysis was performed on individual patient data from all the trials that met the selection criteria. Sensitivity analysis was performed when there was significant heterogeneity. Results were expressed as risk difference for dichotomous outcomes and mean difference for continuous outcomes with 95 % confidence interval. Results Four randomized clinical trials and three controlled clinical trials comparing the results of the anterior versus posterior approach in the treatment of thoracolumbar burst fractures were retrieved; these studies included 179 and 152 patients in the anterior and posterior approach groups, respectively. There were no differences in terms of neurological recovery, return to work, complications and Cobb angle between the two groups. The anterior approach was associated with longer operative time, greater blood loss and higher cost than the posterior approach. Conclusions The posterior approach may be more effective than the anterior approach. However, more highquality, randomized controlled trials are required to compare these approaches and guide clinical decision-making. Level of Evidence Level II, therapeutic study. See the Guidelines for Authors for a complete description of level of evidence.