Lighting Up Nonemissive Azobenzene Derivatives by Pressure.

Pressure-induced emission (PIE) is a compelling phenomenon that can activate luminescence within nonemissive materials. However, PIE in nonemissive organic materials has never been achieved. Herein, we present the first observation of PIE in an organic system, specifically within nonemissive azobenzene derivatives.

Realizing long range π-conjugation in phenanthrene and phenanthrene-based molecular crystals for anomalous piezoluminescence.

Unlike the known aggregation-caused quenching (ACQ) that the enhancement of π-π interactions in rigid organic molecules usually decreases the luminescent emission, here we show that an intermolecular "head-to-head" π-π interaction in the phenanthrene crystal, forming the so-called "transannular effect", could result in a higher degree of electron delocalization and thus photoluminescent emission enhancement. Such a transannular effect is molecular configuration and stacking dependent, which is absent in the isomers of phenanthrene but can be realized again in the designed phenanthrene-based cocrystals. The transannular effect becomes more significant upon compression and causes anomalous piezoluminescent enhancement in the crystals.

Doping of charge-transfer molecules in cocrystals for the design of materials with novel piezo-activated luminescence.

A novel piezo-activated luminescent material with wide range modulation of the luminescence wavelength and a giant intensity enhancement upon compression was prepared using a strategy of molecular doping. The doping of THT molecules into TCNB-perylene cocrystals results in the formation of a weak but pressure-enhanced emission center in the material at ambient pressure. Upon compression, the emissive band from the undoped component TCNB-perylene undergoes a normal red shift and emission quenching, while the weak emission center shows an anomalous blue shift from 615 nm to 574 nm and a giant luminescence enhancement up to 16 GPa.

Pressure-Induced Local Excitation Promotion: New Route toward High-Efficiency Aggregate Emission Based on Multimer Excited State Modulation.

Achieving high-efficiency solid state emission is essential for practical applications of organic luminescent materials. However, intermolecular interactions generally induce formation of multimeric aggregate excited states with deficient emissive ability, making it extremely challenging to enhance emission in aggregated states. Here we demonstrate a novel strategy of continuously regulating multimeric excitation constituents with a high-pressure technique successfully enhancing the emission in a representative organic charge-transfer material, Laurdan (6-lauroyl-,-dimethyl-2-naphthylamine).

Molecular insertion regulates the donor-acceptor interactions in cocrystals for the design of piezochromic luminescent materials.

Developing a universal strategy to design piezochromic luminescent materials with desirable properties remains challenging. Here, we report that insertion of a non-emissive molecule into a donor (perylene) and acceptor (1,2,4,5-tetracyanobezene) binary cocrystal can realize fine manipulation of intermolecular interactions between perylene and 1,2,4,5-tetracyanobezene (TCNB) for desirable piezochromic luminescent properties. A continuous pressure-induced emission enhancement up to 3 GPa and a blue shift from 655 to 619 nm have been observed in perylene-TCNB cocrystals upon THF insertion, in contrast to the red-shifted and quenched emission observed when compressing perylene-TCNB cocrystals and other cocrystals reported earlier.

Boosting Potassium-Ion Battery Performance by Encapsulating Red Phosphorus in Free-Standing Nitrogen-Doped Porous Hollow Carbon Nanofibers.

Potassium-ion batteries (KIBs) are a promising alternative to lithium-ion batteries (LIBs) for large-scale renewable energy storage owning to the natural abundance and low cost of potassium. However, the biggest challenge for KIBs application lies in the lack of suitable electrode materials that can deliver long cycle life and high reversible capacity. In this work, we realized unprecedented long cycle life with high reversible capacity (465 mAh g at 2 A g after 800 cycles) as well as outstanding rate capability (342 mAh g at 5 A g) for KIBs by embedding red P into free-standing nitrogen-doped porous hollow carbon nanofibers (red P@N-PHCNFs).

Binding S Se in 1D Carbon Nanofiber with CS Bonding for High-Performance Flexible Li-S Batteries and Na-S Batteries.

A one-step synthesis procedure is developed to prepare flexible S Se @carbon nanofibers (CNFs) electrode by coheating S Se powder with electrospun polyacrylonitrile nanofiber papers at 600 °C. The obtained S Se @CNFs film can be used as cathode material for high-performance Li-S batteries and room temperature (RT) Na-S batteries directly. The superior lithium/sodium storage performance derives from its rational structure design, such as the chemical bonding between Se and S, the chemical bonding between S Se and CNFs matrix, and the 3D CNFs network.

Confined Amorphous Red Phosphorus in MOF-Derived N-Doped Microporous Carbon as a Superior Anode for Sodium-Ion Battery.

Red phosphorus (P) has attracted intense attention as promising anode material for high-energy density sodium-ion batteries (NIBs), owing to its high sodium storage theoretical capacity (2595 mAh g ). Nevertheless, natural insulating property and large volume variation of red P during cycling result in extremely low electrochemical activity, leading to poor electrochemical performance. Herein, the authors demonstrate a rational strategy to improve sodium storage performance of red P by confining nanosized amorphous red P into zeolitic imidazolate framework-8 (ZIF-8) -derived nitrogen-doped microporous carbon matrix (denoted as P@N-MPC).