A Copper Iodide Cluster-Based Coordination Polymer as an Unconventional Zero-Thermal-Quenching Phosphor.

Phosphor-converted white light-emitting diodes (pc-wLEDs) are promising candidates for next-generation solid-state lighting and display technologies. However, most of the conventional phosphors in pc-wLED devices suffer from serious thermal quenching (TQ) at high temperatures. Herein, we investigate an unconventional high-efficiency metal-halide cluster-based phosphor with dynamic Cu-Cu interactions that can resist the TQ effect of photoluminescence. The temperature-dependent structure and solid-state and in situ NMR spectroscopy reveal that the weakening of the Cu-Cu interaction in such a phosphor system enables the electronic structural transition from a bonding to a nonbonding state and hence sustains the PL efficiency at high temperatures (up to 100 °C). The pc-wLEDs incorporating the zero-TQ phosphor show a rapid brightness rise even at a high bias current (1000 mA) with a color rendering index as high as 90, comparable to the commercial phosphor-based prototype LEDs (e.g., YAG:Ce3+). This work establishes a novel prototype of a cluster-based phosphor featuring dynamic intermetallic interactions, which paves the way for the exploration of pc-wLEDs against thermal quenching.

Tracking the Explosive Boiling Dynamics at the Alcohol/MXene Interface.

We demonstrate the real-time tracking of explosive boiling dynamics at the alcohol/MXene interface by monitoring the photoinduced lattice dynamics of MXene nanosheets dispersed in different alcohols. As revealed by ultrafast spectroscopy, the explosive boiling experiences three cascading stages, i.e., the starting initiation (0-1 ns), the following phase explosion (1-6 ns), and the eventual termination (>6 ns). More importantly, the occurrence conditions of explosive boiling are rationally evaluated via photothermal modeling, echoing well to our experimental observations and further suggesting that ∼17-25 layers of alcohol molecules undergo phase transition from liquid to vapor, a result that can hardly be attained by other physicochemical means. Additionally, useful insights into thermal conduction/diffusion and transient acoustic pressure related to the early stage of explosive boiling are provided. This paradigmatic study enriches the fundamental understanding (on a microscopic level) about the elusive dynamics of explosive boiling at the liquid-solid interface.

Designing a Redox Heterojunction for Photocatalytic "Overall Nitrogen Fixation" under Mild Conditions.

Ammonia and nitrates are the most fundamental and significant raw ingredients in human society. Till now, industrial synthetic ammonia by Haber-Bosch process and industrial synthetic nitrates by the Ostwald process have encountered increasingly serious challenges, i.e., high energy consumption, high cost, and environment-harmful gas emissions. Therefore, developing alternative approaches to achieve nitrogen fixation to overcome the inherent deficiencies of the well-established Haber-Bosch and Ostwald processes has fascinated scientists for many years, especially the simultaneous formation of ammonia and nitrate directly from N2 molecules, which has been rarely studied. Herein, a heterojunction-based photocatalytic system is designed to successfully achieve "overall nitrogen fixation," a sustainable and simultaneous conversion of N2 molecules into ammonia and nitrate products under mild conditions. In this heterojunction, interfacial charge redistribution (ICR) promotes selective accumulations of photogenerated electrons and holes in the CdS and WO3 components. As a result, N2 molecules can be activated and reduced to ammonia products with yields of 35.8 µmol h-1 g-1 by a multi-electron process, and synchronously oxidized into nitrate products with yields of 14.2 µmol h-1 g-1 by a hole-induced oxidation coupling process. This work provides a novel insight and promising approach to realize artificial nitrogen fixation under mild condition.