ChemPhysMater最新文献

In this study, Mn₃O₄ spherical particles (SPs) were synthesized by the sol-gel process, after which they were thermally annealed at 400 °C, and comprehensively characterized. X-ray Diffraction (XRD) revealed that Mn₃O₄ exhibited a tetragonal spinel structure, and Fourier transformed infrared (FTIR) spectroscopy identified surface-adsorbed functional groups. Scanning electron microscopy (SEM) and the specific surface area analyses by Brunauer−Emmett−Teller (BET) revealed a porous, homogeneous surface composed of strongly agglomerated spherical grains with an estimated average particle size of ∼35 nm, which corresponded to a large specific surface area of ∼81.5 m²/g. X-ray photoelectron spectroscopy (XPS) analysis indicated that Mn₃O₄ was composed of metallic cations (Mn⁴⁺, Mn³⁺, and Mn²⁺) and oxygen species (O²⁻, OH⁻ and CO₃²⁻). The optical bandgap energy is ∼2.55 eV. Assessment of the catalytic performance of the Mn₃O₄ SPs indicated T₉₀ conversion of CH₄ to CO₂ and H₂O at 398 °C for gas hourly space velocity (GHSV) of 72000 mL³ g⁻¹ h⁻¹. This observed performance can be attributed to the cooperative effects of the smallest spherical grain size with a mesoporous structure, which is responsible for the larger specific surface area and available surface-active oxygenated species. The cooperative effect of the good reducibility, higher ratio of active species (O_Lat/O_Ads), and results of density functional theory (DFT) calculations suggested that the total oxidation of CH₄ over the mesoporous Mn₃O₄ SPs might take place via a two-term process in which both the Langmuir−Hinshelwood and Mars−van Krevelen mechanisms are cooperatively involved.

Organic-inorganic hybrids are next-generation materials for use in high-performance optoelectronic devices owing to their adaptabilities in terms of design and properties. This article reviews the application of hybrid materials and layers in several widely used optoelectronic devices, i.e., light amplification by stimulated emission of radiation (LASER), solar cells, and light-emitting diodes (LEDs). The effects of the incorporation of inorganic particles on photostability and optical gain are analyzed in the first section with reference to dye and perovskite lasers. Second, the strategies used in blending inorganic nanostructures into organic solar cells and bulk heterojunctions are analyzed. The use of various organic layers as electron- and hole-transport materials in Si heterojunction solar cells is reviewed in detail. Finally, the benefits of the presence of organic components in quantum-dot- and perovskite-based LEDs are derived from the analysis. The integration of organic and inorganic components with optimal interfaces and morphologies is a challenge in developing hybrid materials with improved efficiencies.

ZnO–TiO₂ thin films containing 0.5 mol%, 1.0 mol%, and 5.0 mol% ZnO were synthesized by oxidative solid-phase pyrolysis. The materials contained anatase and rutile phases with particle size of 6–13 nm, as confirmed using X-ray phase analysis and scanning electron microscopy. When a certain number of ZnO crystallites appeared in the TiO₂ film structure in the temperature range of room temperature to 220 °C, a two-level response of the film resistance was observed, differing by approximately 10%, as obtained by electrophysical measurements. The two-level response correlates with the formation of two donor energy levels of 0.28 and 0.33 eV in the band structure of the ZnO–TiO₂ films. The donor level with a higher activation energy corresponded to the Ti vacancy (V⁻_Ti), and that with a lower activation energy corresponded to the Zn vacancy (V⁻_Zn). Two levels of gas-sensitive properties were noted for 0.5ZnO–TiO₂, 1ZnO–TiO₂, and 5ZnO–TiO₂ under the influence of 50 ppm NO₂ at 250 °C. Such two-level responses can be ascribed to the pinning of the Fermi level on ZnO and TiO₂ nanocrystallites. The mechanism of the beak-shaped and two-level responses of sensors based on composite nanomaterials when exposed to various gases was elucidated.

Nickel foam is widely used as a collector for electrocatalysts because of its excellent electrical conductivity; however, it is prone to react with elements such as oxygen, sulfur, and phosphorus during the growth of electrode materials, which makes it brittle and fragile, thus limiting its large-scale application. In this study, bifunctional electrocatalysts with flexible multilevel Ni-based nanoclusters Ni@(Ni,Fe)Se₂/Ni@CC were synthesized on carbon cloth (CC) by hydrothermal and electrodeposition methods; these flexible electrocatalysts are convenient for subsequent industrial applications. At a current density of 10 mA cm⁻², the overpotentials of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) reached 98 and 224 mV, respectively, exceeding the catalytic effects of most metal-based collectors. The overall water-splitting potential of the catalyst was only 1.56 V at 10 mA cm⁻², and the performance was maintained after a 24 h stability test. Ni@(Ni,Fe)Se₂/Ni@CC significantly improved the activity in alkaline environments by modulating the center of the d-band, thereby increasing the adsorption capacity of the catalyst for H ions. In this study, we improved the intrinsic activity and charge transfer of transition metal electrocatalysts by modifying the carbon cloth and constructing multilevel Ni-based nanoclusters, which provided some insights into the rational design of flexible bifunctional electrocatalysts.

To achieve the rapid and real-time detection of triethylamine (TEA) gas, this study synthesized a gas sensor based on heterostructures of Fe₂O₃/MoO₃ using a hydrothermal method. Fe₂O₃/MoO₃ composites with a narrow bandgap (1.1 eV) were successfully synthesized by constructing heterostructures. The rapid and efficient detection of triethylamine was achieved at 220 °C. The response and response/recovery times of the Fe₂O₃/MoO₃ sensor with 50 × 10⁻⁶ triethylamine were 132 s and 5 s/10 s, respectively. The Fe₂O₃/MoO₃ sensor maintained a good response to triethylamine gas, even at 80% relative humidity. The sensing mechanism of the Fe₂O₃/MoO₃ sensor can be described in terms of adsorption energy and electronic behavior of the sensing layer using density functional theory (DFT). The results are consistent with the excellent selectivity and rapid response/recovery of the Fe₂O₃/MoO₃ gas sensor for triethylamine. Therefore, the construction of heterostructures to facilitate electron transmission is an effective strategy to achieve rapid detection of triethylamine and is worthy of further exploration and investigation.

MnWO₄/WO₃ p-n heterojunction films were fabricated using a one-step method consisting of the plasma electrolytic oxidation (PEO) of titanium in homogeneous electrolytes containing paratungstate ions and stable water-soluble EDTA-chelated manganese. The influences of the formation current density and W:Mn molar ratio of the electrolyte, which was varied from 1:2 to 2:1, on the composition, morphology, and optical and photocatalytic properties of the resulting coatings were studied. X-ray diffraction analysis, scanning electron microscopy, energy dispersive X-ray analysis, Raman spectroscopy, and ultraviolet diffuse reflectance spectroscopy were used to characterize the formed composites. Regardless of the W:Mn ratio of the electrolyte, the coatings contained crystalline t-WO₃ and m-MnWO₄. Depending on the formation conditions, the optical band gap energies of the composites varied from 2.63 to 3.01 eV. The largest absorption red shift and lowest band gap energy were observed in the film composite formed in an electrolyte with W:Mn = 2:1, at a current density of 0.2 A cm⁻². Composites obtained in electrolytes with W:Mn ratios of 2:1 and 1:1 exhibited photocatalytic activity in the degradation of rhodamine C and methyl orange dyes in the presence of 10 mmol L^–1 H₂O₂ under ultraviolet and visible light irradiation. The role of hydrogen peroxide in this dye degradation on PEO-coated composites under light irradiation is discussed.

Micro-/nano-motors (MNMs) or swimmers are minuscule machines that can convert various forms of energy, such as chemical, electrical, or magnetic energy, into motion. These devices have attracted significant attention owing to their potential application in a wide range of fields such as drug delivery, sensing, and microfabrication. However, owing to their diverse shapes, sizes, and structural/chemical compositions, the development of MNMs faces several challenges, such as understanding their structure-function relationships, which is crucial for achieving precise control over their motion within complex environments. In recent years, machine learning techniques have shown promise in addressing these challenges and improving the performance of MNMs. Machine learning techniques can analyze large amounts of data, learn from patterns, and make predictions, thereby enabling MNMs to navigate complex environments, avoid obstacles, and perform tasks with higher efficiency and reliability. This review introduces the current state-of-the-art machine learning techniques in MNM research, with a particular focus on employing machine learning to understand and manipulate the navigation and locomotion of MNMs. Finally, we discuss the challenges and opportunities in this field and suggest future research directions.

Owing to the significant development in graphene, an increasing number of studies have been conducted to identify novel two-dimensional (2D) organic materials with Dirac cones and topological properties. Although a series of toy models based on specific lattice patterns has been proposed and demonstrated to possess a Dirac cone, realistic materials corresponding to the lattice models must be identified to achieve excellent properties for practical applications. To understand factors contributing to the rarity of 2D organic Dirac materials and provide guidance for identifying novel organic Dirac systems, we review recent theoretical studies pertaining to various 2D Dirac models and their corresponding organic Dirac materials, including the Haldane, Kagome, Libe, line-centered honeycomb, and Cairo pentagonal models. Subsequently, the corresponding structural and topological electronic properties are summarized. Additionally, we investigate the relationship between the existence of Dirac cones and their structural features, as well as the manner by which Dirac points emerge and propagate in these systems.