Chemical Physics最新文献

It is indisputable that structural defects are pivotal in modulating the properties of materials. This study provides a comprehensive analysis of the structural, optical, and photoluminescence characteristics of V₂O₅, ZrO₂, and ZrV₂O₇.These materials were chosen for their potential applications in various key technological domains. The XRD results revealed the formation of high-purity materials with no secondary phases. It was determined that ZrO₂exhibits the most significant quantity of structural defects among the investigated materials. The variation in crystallite size as determined by XRD aligns with the variation in grain size observed through Scanning Electron Microscopy (SEM).The optical band gaps of V₂O₅, ZrO₂, and ZrV₂O₇ were determined to be 2.27 eV, 5.19 eV, and 2.38 eV, respectively. X-ray Photoelectron Spectroscopy (XPS) analysis indicated the presence of constituent elements without any contaminants. A detailed examination of the photoluminescence (PL) emission characteristics in both UV–Vis and near-infrared (NIR) regions for all materials presented broad visible luminescence in the [450–650] nm range under UV excitation. Structural defects are crucial in determining the physico-chemical properties of materials. This is thoroughly examined for V₂O₅, ZrO₂, and ZrV₂O₇.The infrared (IR) emission spectra, introduced for the first time in this study for V₂O₅, ZrO₂, and ZrV₂O₇, are employed to elucidate the localization of structural defects within the band gap.

Today epoxy novolac resins are of great interest for the aerospace industry. Thermal properties of the polymer matrix, as well as the effect of moisture on the characteristics of polymer composite materials (PCM) under thermomechanical impacts, are critical tasks in creating dimensionally stable structures operating in a wide temperature range. Particularly, thermal and moisture expansion as well as heat capacity are important parameters for evaluating of polymer matrices and modeling their properties. In this work, polymers based on a number of epoxy novolac resins with aromatic amine hardener were studied. The values of the crosslink density were experimentally determined, and a comparative analysis of thermal expansion and heat capacity for epoxy polymers with different crosslink density was carried out. The dependence of thermophysical properties on polymer crosslinking density is shown, both in glass and highly elastic states. Additionally, this study analyzes the process of water sorption by polymers and the coefficient of moisture expansion. The most significant dependence of the diffusion coefficient was observed with coefficient of moisture expansion.

We utilize all-atom molecular dynamics simulations to explore the intermolecular structure, dynamics and thermodynamic properties of Zn²⁺ ions in water-in-ionic liquid. Two ionic liquid systems featuring the same cation 1-ethyl-3-methyl-imidazolium [EMIM]⁺ and distinct anions tetrafluoroborate [BF₄]⁻ and hexafluorophosphate [PF₆]⁻ are considered. We consider the water (H₂O) mole fractions (x) varying from 0.33 to 0.71. We observe a significant interactions of Zn²⁺ ions with water in the case of [BF₄]⁻ when compared to [PF₆]⁻. On the other hand Zn²⁺ ions mobility rises more in [EMIM]⁺[BF₄]⁻ as compared to [EMIM]⁺[PF₆]⁻ with x. Higher self-diffusion (D) of Zn²⁺ ions is seen in the case of [EMIM]⁺[BF₄]⁻. The ionic conductivity (σ) of [EMIM]⁺[BF₄]⁻ is greater compared to [EMIM]⁺[PF₆]⁻ with the rise in x. Overall, this article furnishes in-depth molecular-level insights into the behaviour of Zn²⁺ ions in the presence of water mixed ionic liquid electrolytes.

The need to examine diverse conditions involving industrial working fluids and improving thermal transfer efficiency cannot be overstated. Every thermal system must monitor and control excessive heat production and propagation to avert disruptions in various engineering processes. Therefore, the study investigated the theoretical significance of thermal criticality and a two-step exothermic reaction on Casson-Williamson fluid dynamics behaviour through a fixed vertical channel driven by an electromagnetic field, axial pressure gradient, and heat buoyancy force under a generalized bimolecular chemical kinetic. The heat exchange at the convective wall surface is adhered to Newton’s law of cooling. The Galerkin weighted residual method (GWRM) was utilized to solve the dimensionless nonlinear equations governing the flow within the boundary layer, yielding graphical representations of momentum and energy distributions. The results show that higher values of the activation energy, Frank-Kamenetskii parameter, electric field loading, activation ratio term, Weissenberg number, and second step term led to better heat dispersion and, eventually, complete combustion of hydrocarbons in the Casson-Williamson fluid. To avoid system disruptions, the study underscores the crucial need for continuous monitoring of all factors that stimulate internal heat generation to prevent system failures, emphasizing the importance of vigilance in the field of thermal systems.

One-dimensional ZnO nanoarrays (ZnO NAs) were prepared on nickel foam using a one-step chemical bath deposition method. SEM and XRD confirmed the successful preparation of ZnO nanoarrays. TEM and Raman spectroscopy confirmed the preferential orientation of the ZnO nanorods along the (0 0 2) crystal plane. The Ni/ZnO NAs composites exhibited excellent photocatalytic degradation activity for ciprofloxacin (CIP) under UV light. UV–visible diffuse reflectance and transient photocurrent response characterization revealed that compared with ZnO nanorod powder, the Ni/ZnO NA composites increased the light absorption and reduced the complexation rate of photogenerated electron-hole pairs, thus improving the photocatalytic efficiency. In addition, the electron work functions of the two substances were calculated by using the crystal faces of Ni (1 1 1) and ZnO (0 0 2), and the calculation results confirmed the electron transfer paths. Electron transfer pathways further confirmed the possible reaction mechanism of Ni/ZnO NA degradation of CIP. Finally, Mott–Schottky tests were used to investigate the structure of the energy bands of the material and reveal its photocatalytic mechanism.

Neutral impact collision ion scattering spectroscopy (NICISS) is used to measure the energy loss in organic self-assembled monolayers (SAMs) on Au using Ne⁺ with low kinetic energies from 3 to 5 keV. With increasing film thickness, the energy loss of the projectiles increases because the projectile experiences more collisions with target atoms.

Through comparing Monte-Carlo simulations with the NICISS experiments, it was found that contributions from nuclear stopping for Ne⁺ were significantly larger than for He⁺ mainly due to the stronger contribution of small-angle scattering of Ne⁺ making Ne NICISS unsuitable for depth profiling at energies of 5 keV or lower. The measured Ne⁺ electronic stopping in SAMs is small despite the large atomic number of Ne. Comparing experiments and DFT calculations shows that the latter accurately reproduce stopping powers for Ne⁺, while SRIM overestimates the stopping power. This contrasts He⁺ ions, where DFT and SRIM align closely with experiments.

In recent years, two-dimensional (2D) all-inorganic Ruddlesden–Popper (RP) perovskites have attracted significant research attention. In this study, the electronic and carrier transport properties of 2D layered RP perovskite Cs₂PbBr₄ are studied by DFT calculations. The carrier mobility of the RP perovskite Cs₂PbBr₄ layers are studied based on deformation-potential (DP) theory. We found that the carrier mobility in 2D Cs₂PbBr₄ layers are enhanced as the number of layers increases. For trilayer Cs₂PbBr₄ the electron mobility reaches 7588.7 cm²V⁻¹s⁻¹, which is much higher than the widely studied bulk MAPbI₃ (1500 cm²V⁻¹s⁻¹). In addition, the exciton binding energies are also calculated. Our work proves that the 2D RP perovskite Cs₂PbBr₄ layers are potential candidates for the photoelectronic devices applications.

Photocatalytic process is a new and efficient technology, which has great potential in the U(VI) reduction process. Nitrogen is volatile at high temperatures, so its synthesis reaction is significantly influenced by pyrolysis temperature. Herein, a series of nitrogen-rich carbon nitride with different nitrogen content and different catalytic properties were prepared by changing the pyrolysis temperature from 450 °C to 650 °C. With the increase of pyrolysis temperature, the nitrogen content decreases continuously, and the triazine ring, tetrazine ring and azo bond generated by low temperature pyrolysis are gradually replaced by heptazine ring and nitrogen single bond. The nitrogen-rich carbon nitride synthesized at 550 °C has the best reducing activity for U(VI) reduction, which is attributed to the good cavity structure, narrow light absorption band gap and high electron transport channel. These results can provide guidance for regulating the electron transport structure of the nitrogen-rich carbon nitride to achieve enhanced photocatalytic activity.

This study addresses a scientific challenge by elucidating the influence of calcination temperature on the properties and electromagnetic wave absorption capabilities of NiCo₂O₄, a material whose performance is inherently tied to its preparation process. Specifically, we systematically investigate how varying calcination temperatures not only diversify the material’s composition and morphology but also enhance its electromagnetic wave absorption properties. By controlling the calcination temperature, we not only achieve the successful synthesis of NiCo₂O₄ but also unravel intricate correlations among calcination conditions, material composition, and wave absorption performance. Notably, NiCo₂O₄ sample calcined at 400 °C exhibits remarkable electromagnetic wave absorption, marked by an exceptional maximum reflection loss of −53.93 dB and a broad absorption bandwidth spanning 6.24 GHz. These insights contribute to advancing the frontiers of NiCo₂O₄ utilization, particularly in the realm of electromagnetic wave absorption and beyond, underscoring the novelty and impact of our research.

The photocatalytic performance of a semiconductor photocatalyst mainly depends on the exposure degree of the crystal surface with high catalytic performance. The research focused on sm-BiVO₄, which exhibits superior photocatalytic performance, as the subject of the study. Based on Density Functional Theory (DFT), the stability, electrical properties, optical properties, adsorption properties and surface activity of 7 low-index faces and one easily formed (1 1 2) crystal face of monoclinic clinobisvanite bismuth scheelite (sm-BiVO₄) were investigated. The results show that the (0 0 1) crystal faces of sm-BiVO₄ have the highest stability compared to other crystal faces. Bi atoms have the highest number of electrons from VO₄³⁻, the highest light absorption efficiency and the highest surface activity. This work not only contributes to the understanding of sm-BiVO₄ but also demonstrates that the (0 0 1) crystal faces of sm-BiVO₄ has great potential for photocatalytic applications.