Joaquin García Alvarez

Due to the spin-forbidden nature, it remains challenging to achieve room-temperature organic phosphorescence and afterglow materials with high quantum yields. We report a highly efficient dopant-matrix afterglow system enabled by TADF mechanism to realize afterglow quantum yields of 60–70 %, which features a moderate rate constant for reverse intersystem crossing to simultaneously improve afterglow quantum yields and maintain afterglow emission lifetime.

Abstract

We report a highly efficient dopant-matrix afterglow system enabled by TADF mechanism to realize afterglow quantum yields of 60–70 %, which features a moderate rate constant for reverse intersystem crossing (k _RISC) to simultaneously improve afterglow quantum yields and maintain afterglow emission lifetime. Difluoroboron β-diketonate (BF₂bdk) compounds are designed with multiple electron-donating groups to possess moderate k _RISC values and are selected as luminescent dopants. The matrices with carbonyl functional groups such as phenyl benzoate (PhB) have been found to interact with and perturb BF₂bdk excited states by dipole–dipole interactions and thus enhance the intersystem crossing of BF₂bdk excited states. Through dopant-matrix collaboration, the efficient TADF-type afterglow materials have been achieved to exhibit excellent processability into desired shapes and large-area films by melt casting, as well as aqueous afterglow dispersions for potential bioimaging applications.

The natural cellulose substances have been proven to be ideal structural templates and scaffolds for the fabrication of artificial functional materials with designed structures, psychochemical properties and functionalities. The natural cellulose substances own unique hierarchically porous network structures with flexible, biocompatible, and environmental characteristics, exhibiting great potentials in the preparation of energy‐related materials. This minireview summarizes the natural cellulose substances based materials that utilized in batteries, supercapacitors, photocatalytic hydrogen generation, photoelectrochemical cells, and solar cells. When the natural cellulose substances are employed as the structural template or carbon sources of the energy materials, the three‐dimensionally porous interwoven structures are perfectly replicated, leading to the enhanced performances of the resultant materials. Benefiting from the mechanical strengths of the natural cellulose substances, the wearable, portable, free‐standing, and flexible materials for energy storage and conversion are easily obtained by using natural cellulose substances as the substrates.

The ability to synthesize metal halide perovskite nanocrystals (PNCs) with outstanding long‐term stability against a set of external stimuli represents an important step towards their use for a wide spectrum of optoelectronic applications. Notably, approaches to achieve stable PNCs of interest, in particular those with large structural anisotropy , via protective coating of inorganic shell at a single‐nanocrystal (NC) level are comparatively few and limited in scope. Herein, we report a robust amphiphilic‐diblock‐copolymer‐enabled strategy for crafting highly‐stable anisotropic CsPbBr 3 nanosheets (NSs) via in‐situ formation of uniform inorganic shell (1 st shielding) that is intimately ligated with hydrophobic polymers (2 nd shielding). The dual‐protected NSs display an array of remarkable stabilities (i.e., thermal, photostability, moisture, polar solvent, aliphatic amine, etc.) and find application in white light‐emitting diodes. In principle, by anchoring other multidentate amphiphilic polymer ligands on the surface of PNCs, followed by templated‐growth of shell materials of interest, a rich variety of dual‐shelled, multifunctional PNCs with markedly improved stabilities can be created for use in optics, optoelectronics and sensory devices.

Rhodium–antimony nanorods: A unique class of surface‐rough Rh₂Sb nanorods (RNRs) has been created. Rh₂Sb RNRs/C showed enhanced N₂ reduction reaction (NRR) performance with NH₃ yield rate of 228.85±12.96 μg h⁻¹ mg⁻¹ _Rh at −0.45 V_RHE, outperforming the surface‐smooth Rh₂Sb NRs/C, as well as the Rh nanoparticles/C, demonstrating the important role of surface regulation in boosting NRR.

Abstract

Surface regulation is an effective strategy to improve the performance of catalysts, but it has been rarely demonstrated for nitrogen reduction reaction (NRR) to date. Now, surface‐rough Rh₂Sb nanorod (RNR) and surface‐smooth Rh₂Sb NR (SNR) were selectively created, and their performance for NRR was investigated. The high‐index‐facet bounded Rh₂Sb RNRs/C exhibit a high NH₃ yield rate of 228.85±12.96 μg h⁻¹ mg⁻¹ _Rh at −0.45 V versus reversible hydrogen electrode (RHE), outperforming the Rh₂Sb SNRs/C (63.07±4.45 μg h⁻¹ mg⁻¹ _Rh) and Rh nanoparticles/C (22.82±1.49 μg h⁻¹ mg⁻¹ _Rh), owing to the enhanced adsorption and activation of N₂ on high‐index facets. Rh₂Sb RNRs/C also show durable stability with negligible activity decay after 10 h of successive electrolysis. The present work demonstrates that surface regulation plays an important role in promoting NRR activity and provides a new strategy for creating efficient NRR electrocatalysts.

Density functional theory calculations have been preformed to investigate the mechanism of addition of a 4‐nitrophenyl ester to an iminium ion catalyzed by isothiourea and the origin of the selectivity. The principle of chemoselectivity prediction was also verified by a series of analyses.

Abstract

The possible mechanisms and origin of the selectivities of isothiourea‐catalyzed addition of saturated esters to iminium ions have been investigated by density functional theory. The favorable reaction pathway includes three stages: formation of an ammonium enolate intermediate, enantioselective addition of the ammonium enolate intermediate to the iminium ion, and dissociation of the catalyst to form the product. The enantioselective addition process is the stereoselectivity‐determining step, while the chemoselectivity‐determining step is included in the formation of the final product. The calculated energy barriers show that the chemoselectivity is thermodynamically controlled, and it depends on the polarities of the products and the nucleophilicities of the N atoms of the enamine reactant moieties of the intermediates. The origin of the stereoselectivity was investigated by non‐covalent interaction analysis of the key transition states. Hydrogen bonding interactions were identified as the determining factor for controlling the stereoselectivity. The obtained insight will be valuable for rational design of novel Lewis base organocatalyst‐promoted enantioselective addition reactions with special chemoselectivities.

Publication date: 24 January 2020

Source: Inorganica Chimica Acta, Volume 500

Author(s): Kang Liu, Junhua Zhang, Shuaicong Huo, Qing Dong, Zhiqiang Hao, Zhangang Han, Guo-Liang Lu, Jin Lin

Graphical abstract

Glucaric acid (GA) is a major value‐added chemicals feedstock and additive, especially in the food, cosmetic and pharmaceutical industries. The increasing demand for GA is driving the search for a more efficient and less costly production pathway. In this study, we developed a novel in vitro multi‐enzyme cascade system which efficiently converts sucrose to GA in a single vessel. The in vitro system, which does not require ATP or NAD+ supplementation, contains seven enzymes (sucrose phosphorylase, phosphoglucomutase, myo‐inositol 1‐phosphate synthase, myo‐inositol monophosphatase, myo‐inositol oxygenase, uronate dehydrogenase and NADH oxidase). All enzyme were chosen from the BRENDA and NCBI databases and were efficiently expressed in Escherichia coli BL21(DE3). We combined all seven enzymes in an in vitro cascade system and optimized the reaction conditions (temperature, pH, NAD+, buffer, enzyme composition, including fed‐batch addition of myo‐inositol oxygenase). Under the optimized conditions, the in vitro seven‐enzyme cascade system converted 50 mM sucrose to 34.8 mM GA with high efficiency (75% of the theoretical yield). This therefore represents an alternative pathway for more efficient and less costly production of GA, which could be adapted for the synthesis of other value‐added chemicals.