Aqueous rechargeable Zn–MnOx batteries are very attractive due to their low‐cost and high energy density. However, Mn(III) disproportionation and Jahn–Teller distortion can induce Mn(II) dissolution and irreversible phase changes, greatly deteriorating the cycling life. Herein, a multi‐valence cobalt‐doped Mn3O4 (Co‐Mn3O4) with high capacity and reversibility, which lies in the multiple roles of the various states of doped cobalt, is reported. The Co2+ doping between the phase change product δ‐MnO2 layer acts as a “structural pillar,” and the Co4+ in the layer can increase the conductivity of Mn4+ and hold the high specific capacity. More importantly, Co ion (Co2+, Co3+) doping can effectively inhibit the Jahn–Teller effect in discharge products and promote ion diffusion. Using X‐ray absorption spectra results and density functional theory modelling, the multiple roles of doped cobalt are verified. Specifically, the Co‐Mn3O4 cathode shows high specific capacity of 362 mAh g–1 and energy density of 463.1 Wh kg–1 at 100 mA g–1. After 1100 cycles at 2.0 A g–1, the capacity retention rate reaches 80%. This work brings a new idea and approach to the design of highly reversible Mn‐based oxides cathode materials for Zn‐ion batteries.

Wet-chemically synthesized cesium lead halide nanoparticles have many attractive properties that make them promising as optical gain media, but generally suffer from poor stability under ambient conditions and an optical gain threshold that is widely believed to be dictated by the need for biexcitons. These conditions make it impractical for such particles to be utilized as gain media given the need to undergo repeated stimulated emission processes at above-threshold pump intensities over long periods of time. We demonstrate that the surface treatment of CsPbBr nanoparticles with a mixture of PbBr, oleic acid, and oleylamine not only raises their fluorescence quantum yield to nearly unity and prolongs their stability in air from days to months, but it also dramatically increases their trion photoluminescence lifetime from ∼0.9 to ∼1.6 ns. Via a combination of time-resolved photoluminescence and transient absorption spectroscopy, we provide evidence for trion gain at sufficiently low pump intensities in which the likelihood of predominantly biexciton-based gain is small. We then show that, in line with theoretical prediction, the amplified spontaneous emission (ASE) threshold of a thin film of surface-treated CsPbBr nanoparticles reduces to a record low of ∼1.2 μJ/cm with a corresponding average exciton occupancy per nanoparticle of 0.62. The ultralow pump threshold and increased stability allow for stable ASE over millions of laser shots, paving the way for the deployment of these nanoparticles as viable solution-processed optical gain media.

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The energy and spatial distribution of intragap trap states of the TiO2 photoanode of dye-sensitized solar cells and their impact on charge recombination were investigated by means of time-resolved charge extraction (TRCE) and transient photovoltage (TPV). The photoanodes were built from TiO2 nanospheroids with different aspect ratios, and the TRCE results allowed differentiation of two different types of trap states, that is, deep and shallow ones at the surface and in the bulk of the TiO2 particles, respectively. These trap states exhibit distinctly different characteristic energy with only a slight variation in the particle size, as derived from the results of the density of states. Analyses of the size-dependent TPV kinetics revealed that in a moderate photovoltage regime of about 375-625 mV, the dynamics of electron recombination are dominated by shallow trap states in the bulk, which can be well accounted for by the mechanism of multiple-trap-limited charge transport.

In the framework of effective-mass envelope-function theory, the optical transitions of InAs/GaAs strained coupled quantum dots grown on GaAs ͑100͒ oriented substrates are studied. At the ⌫ point, the electron and hole energy levels, the distribution of electron and hole wave functions along the growth and parallel directions, the optical transition-matrix elements, the exciton states, and absorption spectra are calculated. In calculations, the effects due to the different effective masses of electrons and holes in different materials are included. Our theoretical results are in good agreement with the available experimental data.

The density of state (DOS) of intra-gap traps and the dynamics of electron transport of a dye-sensitized TiO2 solar cell were investigated by means of time-resolved charge extraction (TRCE). The intrinsic chemical capacitance of the TiO2 layer was separated from the parasitic capacitance of the FTO electrode, and was found to be dependent biexponentially on the photovoltage. It was shown that the shallow traps (>700 meV) differ from the deep ones (<350 meV) by the respective characteristic energy of 48 meV and 765 meV, and that the amount of shallow traps is more than an order of magnitude larger than that of the deep ones. Our results support the mechanism of shallow-trap dominant multiple-trap limited charge transport, and suggest a substantial margin for the short-circuit photocurrent density to reach its theoretical limit.

Development of earth-abundant, efficient, and stable electrocatalysts for hydrogen evolution reactions (HER) in alkaline or even neutral pH electrolyte is very important for hydrogen production from water splitting. Construction of bimetal phosphides via tuning the bonding strength to hydrogen and increasing effective active sites through nanostructuring and surface engineering should lead to high HER activity. Here, ternary NiCoP nanowires (NWs) decorated by homogeneous nanoparticles have been obtained on Ni foam for a highly efficient HER property via long-term cyclic voltammetric (CV) sweeping. The electron density transfer between the positively charged Ni and Co and negatively charged P atoms, one-dimensional electron transfer channel of the NWs, and abundant active sites supplied by the nanoparticles and NWs endow the catalyst with low overpotentials of 43 and 118 mV to achieve the respective current densities of 10 and 100 mA cm together with long durability for at least 33 h in 1 M KOH. A cycled anodic dissolution-redeposition mechanism is disclosed for the formation of the NiCoP nanoparticles during the CV sweeping process. Such a surface roughening method is found to be adaptable to enhance the HER property of other phosphides, including NiP nanoplates/NF, NiCoP nanoparticles/NF, and CoP NW/NF.

Synthesis of densely grafted (co)­polymer brushes, including poly­(tert-butyl acrylate) (PtBA), poly­(tert-butyl acrylate)-b-poly­(styrene) (PtBA-b-PS), and poly­(tert-butyl acrylate)-b-poly­(butyl acrylate) (PtBA-b-PBA), from 15.8 nm silica nanoparticles (NPs) via a surface-initiated simplified electrochemically mediated atom transfer radical polymerization (SI-seATRP) under constant potential electrolysis conditions is reported for the first time. The rate of polymerization was enhanced by applying more negative potentials, which resulted in an increase in grafting density, up to 0.93 nm–2. Furthermore, temporal control over the polymerization was achieved by adjustment of the applied potential. The polymers showed narrow molecular weight distributions (Đ = 1.20–1.32), and polymer-grafted nanoparticles had excellent size uniformity. Dispersions in suitable solvents were stable without any nanoparticle aggregation. Microstructures observed in thin films of densely block copolymer tethered silica NPs suggested that the structure formation process is strongly influenced by the conformation of tethered chains. Hence, microstructure formation in thin films of block copolymer brush particles in which the first block is in the “stretched brush regime” was determined primarily by surface interactions rather than microphase separation.