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Abstract Polarons generally affect adversely the photochemical and photophysical properties of transition metal oxides. However, the excited-state dynamics of polarons are not fully established to date and thus require an atomistic understanding. We focus on α-Fe2O3 with photoexcitation, electron injection, and heterovalent doping as the small polaron models, and conduct simulations of ab initio adiabatic molecular dynamics (AIMD) and nonadiabatic molecular dynamics (NA-MD). The elaborately designed AIMD simulations show that localization of electron at a single Fe site is an adiabatic and ultrafast process within sub-15 fs. Fe2O3 doping with an electron or a Si and Ti dopant forms a localized electron polaron while photoexcitation forms localized electron and hole polarons simultaneously, leading to diverse electron–hole recombination dynamics. NA-MD simulations demonstrate that recombination of an electron polaron created by doping with a delocalized hole at the valence band maximum of α-Fe2O3 takes place around 5 ps, while recombination between a pair of small electron and hole polarons in photoexcited Fe2O3 delays to about 110 ps owing to weak NA coupling and fast decoherence process. The ultrafast formation of small electron polarons in α-Fe2O3 impedes the accumulation of delocalized holes in the valence band that directly participate in water oxidation at photoanodes. The detrimental effect can be partially circumvented in photoexcited Fe2O3 for slowing electron–hole recombination despite polarons may retain low charge mobility. These findings provide a fundamental understanding of the excited-state dynamics of small electron polaron in α-Fe2O3 and may help design efficient transition metal oxides photoanodes.

Abstract Epitaxial heterostructures of colloidal lead halide perovskite nanocrystals (NCs) with other semiconductors, especially the technologically important metal chalcogenides, can offer an unprecedented level of control in wavefunction design and exciton/charge carrier engineering. These NC heterostructures are ideal material platforms for efficient optoelectronics and other applications. Existing methods, however, can only yield heterostructures with random connections and distributions of the two components. The lack of epitaxial relation and uniform geometry hinders the structure–function correlation and impedes the electronic coupling at the heterointerface. This work reports the synthesis of uniform, epitaxially grown CsPbBr3/CdS Janus NC heterostructures with ultrafast charge separation across the electronically coupled interface. Each Janus NC contains a CdS domain that grows exclusively on a single {220} facet of CsPbBr3 NCs. Varying reaction parameters allows for precise control in the sizes of each domain and readily modulates the optical properties of Janus NCs. Transient absorption measurements and modeling results reveal a type II band alignment, where photoexcited electrons rapidly transfer (within ≈9 picoseconds) from CsPbBr3 to CdS. The promoted charge separation and extraction in epitaxial Janus NCs leads to photoconductors with drastically improved (approximately three orders of magnitude) responsivity and detectivity, which is promising for ultrasensitive photodetection.

The sluggish oxygen evolution reaction kinetics severely hinder the development of photoelectrochemical water splitting. Here the authors introduce Fe-In-S clusters onto the surface of photoanode to effectively lower the electrochemical reaction barrier.

Performance of perovskite LED tends to decline as the active area increases, thus understanding the failure mechanism is paramount to surmount this limitation. Here, the authors report severe phase-segregation to be the cause, and introduce L-Norvaline to overcome it, as the result, highly-efficient 9.0 cm2 green PeLED is realised.

Quasi-2D halide perovskites are good candidates for efficient and stable solar cells but they suffer from high open-circuit voltage (V oc) deficit. Here He et al. show that homogeneous energy landscape of the charge transport levels is important to suppressing the recombination and increasing V oc.

The distribution of individual water molecules’ self-diffusivities in adsorbed layers at TiO2 surfaces anatase (101) and rutile (110) have been determined at 300 K for inner and outer adsorbed layers, via classical molecular-dynamics methods. The layered-water structure has been identified and classified in layers making use of local order parameters, which proved to be an equally valid method of “self-ordering” molecules in layers. Significant distinctness was observed between anatase and rutile in disturbing these molecular distributions, more specifically in the adsorbed outer layer. Anatase (101) presented significantly higher values of self-diffusivity, presumably due to its “corrugated” structure that allows more hydrogen bonding interaction with adsorbed molecules beyond the first hydration layer. On the contrary, rutile (110) has adsorbed water molecules more securely “trapped” in the region between Ob atoms, resulting in less mobile adsorbed layers.

The grand challenges in renewable energy lie in our ability to comprehend efficient energy conversion systems, together with dealing with the problem of intermittency via scalable energy storage systems. Relatively little progress has been made on this at grid scale and two overriding challenges still need to be addressed: (i) limiting damage to the environment and (ii) the question of environmentally friendly energy conversion. The present review focuses on a novel route for producing hydrogen, the ultimate clean fuel, from the Sun, and renewable energy source. Hydrogen can be produced by light-driven photoelectrochemical (PEC) water splitting, but it is very inefficient; rather, we focus here on how electric fields can be applied to metal oxide/water systems in tailoring the interplay with their intrinsic electric fields, and in how this can alter and boost PEC activity, drawing both on experiment and non-equilibrium molecular simulation.

Cytarabine (Ara-C) is a commonly used chemotherapeutic drug for the treatment of leukemia, known for its significant tolerability. The down regulation of miR-203 in leukemia cells suggests its potential involvement in the pathogenesis of leukemia. In this study, we investigated the effects and possible mechanisms of miR-203 and Ara-C on proliferation and apoptosis of human leukemia K562 cells which were cultured with Ara-C and/or with transfection of miR-203 expression vectors. Our results showed that the combination of Ara-C and miR-203 synergistically inhibited the proliferation of K562 cells and the sensitivity of leukemia cells to Ara-C was increased by 2.5-fold with trasfection of miR-203. The proportion of apoptotic cells in the Ara-C and miR-203 combination group was higher than Ara-C or control plasmid group. Caspase-3 and caspase-9 activities were increased in Ara-C and miR-203 combination group. miR-203 down regulated the protein level of Bcr/abl in K562 cells compared with plasmid control. In conclusion, Ara-C in combination with miR-203 has a synergistic effect of proliferation inhibition and apoptosis induction in chronic myelogenous leukemia K562 cells, which may be associated with miR-203 down regulating Bcr/abl, thereby inhibiting cell proliferation and promoting cell apoptosis. [ABSTRACT FROM AUTHOR]

The catalytic oxidation methods are divided into four categories: thermal catalysis, photocatalysis, electrocatalysis and PMS activated catalysis, and their applications in the removal of toluene are summarized. It is found that the application of precious metals and metal oxides such as Pt, Au, Ag and CeO2 in catalysts has become more and more extensive in recent years. The load on the surface of different materials can significantly affect the physical properties of the finished catalyst such as strength and porosity, and then affect its adaptability to the working conditions and economic benefits. Then, the effects of catalytic materials and reaction conditions on the efficiency of toluene removal were analyzed in detail, and the nature of different types of toluene removal reactions was explained. In addition, according to the different types of reaction temperatures and research time, it is pointed out that catalytic oxidation methods are bound to develop in the direction of more moderate reaction conditions, and catalytic oxidation methods involving free radicals are bound to receive more attention and application because of their energy-saving and efficient characteristics. Finally, it is pointed out that the current research is difficult to apply to engineering and the research of reaction mechanism is insufficient, and the development suggestions are put forward. [ABSTRACT FROM AUTHOR]

Transforming growth factor-β (TGF-β) is a key factor in cancer development and progression. TGF-β can suppress tumorigenesis by inhibiting cell cycle progression and stimulating apoptosis in early stages of cancer progression. However, TGF-β can modulate cancer-related processes, such as cell invasion, distant metastasis, and microenvironment modification that may be used by cancer cells to their advantage in late stages. Corresponding mechanisms include angiogenesis promotion, anti-tumor immunity suppression, and epithelial-to-mesenchymal transition (EMT) induction. The correlation between TGF-β expression and cancer prognosis has also been extensively investigated. Results suggest that TGF-β pathway can be targeted to treat cancer; as such, the feasibility of this treatment is investigated in clinical trials.