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In this paper, we discuss the existence of positive solutions to a discrete third-order three-point boundary value problem. Here, the weight function a(t)a\left(t) and the Green function G(t,s)G\left(t,s) both change their sign. Despite this, we also obtain several existence results of positive solutions by using the Guo-Krasnoselskii’s fixed-point theorem in a cone.

Quantum coherence by electronic quantum interference (QI) is significant to generate macroscopic photocurrent without heterostructures in both bulk and low‐dimensional materials. However, the coherent injection photocurrent by QI in low‐dimensional materials can be veiled by other linear or nonlinear optical effects. Herein, the coherent ultrafast injection photocurrent is investigated by coherent terahertz (THz) wave generation in multilayer rhenium disulfide (ReS2) at the nanometer scale under two‐color light excitation. It is observed that the THz radiation can be controlled by adjusting the relative phase between the two‐color lights under normal incidence. The experimental results demonstrate that the THz radiation of ReS2 is ascribed to the injection photocurrent from the electronic coherence of QI effect. However, the injection photocurrent is veiled by the nonlinear polarization, shift current, and drift current under oblique incidence. A method is proposed to isolate the pure injection photocurrent from these optical responses, based on the THz amplitude dependences on the pump power, incident polarization angle, and the relative phase between the two‐color lights. This work not only provides an all‐optical non‐contact method for understanding the quantum photocurrent in ReS2 but also promotes the quantum coherent control for solid‐state quantum devices. [ABSTRACT FROM AUTHOR]

The carrier dynamics of lead-free cesium tin halide perovskites are crucial for evaluating their potential as substitutes for lead-based perovskites. Herein, we investigate the ultrafast transport of hot carriers in CsSnBr3 microplates synthesized via chemical vapor deposition. We observe a significantly prolonged hot carrier cooling process lasting ∼50 ps, due to the hot-phonon bottleneck effect and the formation of large polarons. By employing transient absorption microscopy, we detect a time-dependent diffusion coefficient of hot carriers initially reaching up to 257.8 cm2·s−1, leading to a long average travel distance of ∼600 nm. Subsequently, it reveals a remarkable equilibrium carrier diffusion coefficient ranging from 12.7 to 16.5 cm2·s−1. These findings establish a fundamental basis for designing and advancing lead-free perovskite-based optoelectronic applications involving hot carriers. [ABSTRACT FROM AUTHOR]

Exploration of efficient, inexpensive, and stable electrocatalysts for the oxygen evolution reaction (OER) is of great significance for the energy crisis and environmental problems. Transition metal oxides (TMOs) are promising electrocatalysts for boosting OER. Herein, porous yolk@shell heterojunction nanospheres (denoted Co3O4@CeO2/Co3O4) were designed by interfaces and vacancies engineering as electrocatalysts for OER. Owing to the large specific surface area of the porous yolk@shell structure, high oxygen vacancy content, and good stability provided by CeO2, rapid charge transfer of Ce3+/Ce4+, and interaction of CeO2/Co3O4 heterojunctions, Co3O4@CeO2/Co3O4 nanospheres exhibit relatively excellent oxygen evolution performance (318 mV@10 mA cm–2) and long-term stability for 45 h in a 1.0 M KOH solution. This work provides a facile way to fabricate a kind of porous yolk@shell heterojunction nanomaterials for improving the OER performance of TMOs electrocatalysis. [ABSTRACT FROM AUTHOR]

Developing efficient electrocatalysts is very important for water electrolysis technology to deal with the energy crisis. The oxygen evolution reaction (OER) in the semireaction of electrolytic water is a crucial step. Herein, we report a facial strategy to fabricate the bird nest-like Fe3O4/CoOx (BN-Fe3O4/CoOx) nanosphere heterojunctions with amorphous/crystalline (a/c) structure through cation-exchange and subsequent calcination treatment in a reducing Ar/H2 atmosphere. Owing to its unique structure and the electron state near the heterogeneous interface, the BN-Fe3O4/CoOx nanosphere exhibits a very competitive overpotential of 286 mV at the current density of 10 mA cm–2 for OER with a low Tafel slope of 55.51 mV dec–1 in 1.0 M KOH, and long-term durability for more than 20 h. This work may provide an idea and a convenient method for the preparation of a/c-heterostructure electrocatalysts. [ABSTRACT FROM AUTHOR]

We have investigated the thermal conductivity and vibration properties of TiS3 nanoribbon via micro-Raman spectroscopy. Based on the Raman spectra, the calculated temperature coefficients of the four A g 1 modes of the TiS3 nanoribbon sample are −0.0140, −0.0136, −0.0179, and −0.0172 cm−1 K−1, respectively, which are higher than that of traditional nanomaterials graphene and MoS2. The Raman frequency shift of TiS3 provides a powerful non-contact method to determine its local temperature rise, which is caused by the anharmonic coupling of phonons. From temperature coefficient and power coefficient values, the in-plane thermal conductivity of the TiS3 supported by SiO2/Si substrate has been calculated to be 187.2 ± 28.9 W/mK with weak anisotropy due to the substrate and size effects. This work paves a way to understand the heat conduction characteristics of transition metal trisulfide. [ABSTRACT FROM AUTHOR]