Search Results (401)

Dielectric capacitors offer immense application potential in advanced electrical and electronic systems with their unique ultrahigh power density. Polymer-based dielectric composites with high energy density are urgently needed to meet the ever-growing demand for the integration and miniaturization of electronic devices. However, the universal contradictory relationship between permittivity and breakdown strength in traditional ceramic/polymer nanocomposite still poses a huge challenge for a breakthrough in energy density. In this work, all-organic carbon quantum dot CDs were synthesized and introduced into a poly(vinylidene fluoride) PVDF polymer matrix to achieve significantly boosted energy storage performance. The ultrasmall and surface functionalized CDs facilitate the polar β-phase transition and crystallinity of PVDF polymer and modulate the energy level and traps of the nanocomposite. Surprisingly, a synergistic dielectric enhancement and loss reduction were achieved in CD/PVDF nanocomposite. For one thing, the improvement in ε_r and high-field D_m originates from the CD-induced polar transition and interface polarization. For another thing, the suppressed dielectric loss and high-field D_r are attributed to the conductive loss depression via the introduction of deep trap levels to capture charges. More importantly, E_b was largely strengthened from 521.9 kV mm⁻¹ to 627.2 kV mm⁻¹ by utilizing the coulomb-blockade effect of CDs to construct energy barriers and impede carrier migration. As a result, compared to the 9.9 J cm⁻³ for pristine PVDF, the highest discharge energy density of 18.3 J cm⁻³ was obtained in a 0.5 wt% CD/PVDF nanocomposite, which is competitive with most analogous PVDF-based nanocomposites. This study demonstrates a new paradigm of organic quantum dot-enhanced ferroelectric polymer-based dielectric energy storage performance and will promote its application for electrostatic film capacitors. Full article

Vacancy defect graphitic carbon nitride (g-C₃N₄) and conjugated polyimide (PI) polymer photocatalysts have become increasingly recognized as metal-free photocatalysts featuring an appropriate bandgap. The narrow absorption spectrum of visible light and the rapid recombination rate of the photoexcited charge carriers in PI polymers and g-C₃N₄ impede its photocatalytic performance. The presence of oxygen vacancies (OVs) in PI polymer photocatalysts, as well as nitrogen vacancies (NVs) and carbon vacancies (CVs) in g-C₃N₄, can significantly enhance the migration of photogenerated electrons. Adding vacancies to improve the electronic structure and band gap width can greatly enhance the photocatalytic efficiency of PI polymers and g-C₃N₄. Defect engineering is important for increasing the photocatalytic ability of PI-polymer and g-C₃N₄. There remains a notable absence of thorough review papers covering the synthesis, characterization, and applications of vacancy-rich PI-polymer and g-C₃N₄ in photocatalysis. This review paper examines the roles of OVs in PI-polymer, NVs, and CVs in g-C₃N₄ and thoroughly summarizes the preparation approaches employed before and after, as well as during polymerization. This review scrutinizes spectroscopic characterization techniques, such as EPR, XPS, PAS, XRD, FTIR, and NMR, for vacancy defect analysis. We also reviewed the role of vacancies, which include light absorption, photogenerated charge carrier separation, and transfer dynamics. This review could serve as a comprehensive understanding, a vacancy-engineered design framework, and a practical guide for synthesizing and characterizing. Full article

As a prominent next-generation anode material for high-capacity applications, silicon stands out due to its potential. Crystalline silicon, which offers a higher initial capacity compared to its amorphous counterpart, presents challenges in practical applications due to its poor cycling performance. In this study, we prepared composites of crystalline and amorphous silicon with graphite, assembled pouch-type full cells, and evaluated their suitability for practical use. The material incorporating amorphous silicon demonstrated superior performance at both high and low rates, as well as various temperatures. Additionally, the changes in cell thickness during charge and discharge, i.e., the volume changes in the anode material, are significantly related to cycling performance. We examined the microscopic interactions between silicon and lithium atoms using molecular dynamics simulations. Our observations indicate that lithium migration within amorphous silicon, which has lower activation energy, is much easier than in crystalline silicon. In crystalline silicon, lithium penetration is greatly influenced by the orientation of the crystal planes, resulting in anisotropic volume expansion during lithiation. Full article

Somatic mutations are common in cancer, with only a few driving the progression of the disease, while most are silent passengers. Some mutations may hinder or even reverse cancer progression. The voltage-gated proton channel (H_V1) plays a key role in cellular pH homeostasis and shows increased expression in several malignancies. Inhibiting H_V1 in cancer cells reduces invasion, migration, proton extrusion, and pH recovery, impacting tumor progression. Focusing on HVCN1, the gene coding for the human voltage-gated proton channel (hH_V1), 197 mutations were identified from three databases: 134 missense mutations, 51 sense mutations, and 12 introducing stop codons. These mutations cluster in two hotspots: the central region of the N-terminus and the region coding for the S4 transmembrane domain, which contains the channel’s voltage sensor. Five somatic mutations within the S4 segment (R205W, R208W, R208Q, G215E, and G215R) were selected for electrophysiological analysis and MD simulations. The findings reveal that while all mutants remain proton-selective, they all exhibit reduced effective charge displacement and proton conduction. The mutations differentially affect hH_V1 kinetics, with the most pronounced effects observed in the two Arg-to-Trp substitutions. Mutation of the first voltage-sensing arginine (R1) to tryptophan (R205W) causes proton leakage in the closed state, accelerates channel activation, and diminishes the voltage dependence of gating. Except for R205W, the mutations promote the deactivated channel configuration. Altogether, these data are consistent with impairment of hH_V1 function by mutations in the S4 transmembrane segment, potentially affecting pH homeostasis of tumor cells. Full article

Durability is crucial for reinforced concrete, directly influencing the service life of structures. The presence of aggressive agents, especially chloride ions, significantly impacts durability. This study investigates the differences between ASTM C1202 and IBRACON/NT Build 492 standards in concrete containing various types of cement designed for a characteristic compressive strength of 40 MPa. Forty-eight cylindrical samples were prepared using eight types of Portland cement, including those with blast furnace slag, filler, and pozzolanic materials. Chloride migration tests were performed according to the ASTM C1202/2022 and IBRACON/NT Build 492/1999 methodologies. At a 95% confidence level, the results indicated that concrete made with filler-containing cement (PCII F-SR and PC II F) showed the poorest chloride resistance, with charge passing values exceeding 4000 coulombs (ASTM C1202) and diffusion coefficients above 10 × 10⁻¹² m²/s (IBRACON/NT Build 492). In contrast, concrete containing high slag cement (PC III-SR) and pozzolan cement (PC IV) demonstrated superior resistance to chloride penetration, with charge passing values below 1500 coulombs and diffusion coefficients under 5 × 10⁻¹² m²/s. Notably, discrepancies in classification were observed, as PC II Z (fly-ash based) and PC II E-SR (slag-based) received different ratings under the two methods. ASTM C1202 was found to be more stringent than NT Build 492, highlighting significant variations in the classification criteria between these standards. Based on the findings, new interval values are proposed for classifying concrete regarding the risk of chloride ion penetration, particularly for the ASTM C1202 standard, in order to better align with performance-based durability criteria and improve classification accuracy. Full article

We used density functional theory with a hybrid functional to investigate the structure and properties of [4H]_Si (hydrogarnet) defects in α-quartz as well as the reactions of these defects with electron holes and extra hydrogen atoms and ions. The results demonstrate the depassivation mechanisms of hydrogen-passivated silicon vacancies in α-quartz, providing a detailed understanding of their stability, electronic properties, and behaviour in different charge states. While fully hydrogen passivated silicon vacancies are electrically inert, the partial removal of hydrogen atoms activates these defects as hole traps, altering the defect states and influencing the electronic properties of the material. Our calculations of the hydrogen migration mechanisms predict the low energy barriers for H⁺, H⁰, and H⁻, with the lowest barrier of 0.28 eV for neutral hydrogen migration between parallel c-channels and a similar barrier for H⁺ migration along the c-channels. The reactions of electron holes and hydrogen species with [4H]_Si defects lead to the breaking of O–H bonds and the formation of non-bridging oxygen hole centres (NBOHCs) within the Si vacancies. The calculated optical absorption energies of these centres are close to those attributed to individual NBOHCs in glass samples. These findings can be useful for understanding the role of [4H]_Si defects in bulk and nanocrystalline quartz as well as in SiO₂-based electronic devices. Full article

Background/Objective: Cationic polymers were shown to assemble with negatively charged proteins yielding nanoparticles (NPs). Poly-diallyl-dimethyl-ammonium chloride (PDDA) combined with ovalbumin (OVA) yielded a stable colloidal dispersion (OVA/PDDA-NPs) eliciting significant anti-OVA immune response. Dendritic cells (DCs), as sentinels of foreign antigens, exert a crucial role in the antigen-specific immune response. Here, we aimed to evaluate the involvement of DCs in the immune response induced by OVA/PDDA. Methods: In vivo experiments were used to assess the ability of OVA/PDDA-NPs to induce anti-OVA antibodies by ELISA, as well as plasma cells and memory B cells using flow cytometry. Additionally, DC migration to draining lymph nodes following OVA/PDDA-NP immunization was evaluated by flow cytometry. In vitro experiments using bone marrow-derived DCs (BM-DCs) were used to analyze the binding and uptake of OVA/PDDA-NPs, DC maturation status, and their antigen-presenting capacity. Results: Our data confirmed the potent effect of OVA/PDDA-NPs inducing anti-OVA IgG1 and IgG2a antibodies with increased CD19⁺CD138⁺ plasma cells and CD19⁺CD38⁺CD27⁺ memory cells in immunized mice. OVA/PDDA-NPs induced DC maturation and migration to draining lymph nodes. The in vitro results showed higher binding and the uptake of OVA/PDDA-NPs by BM-DCs. In addition, the NPs were able to induce the upregulation of costimulatory and MHC-II molecules on DCs, as well as TNF-α and IL-12 production. Higher OVA-specific T cell proliferation was promoted by BM-DCs incubated with OVA/PDDA-NPs. Conclusions: The data showed the central role of DCs in the induction of antigen-specific immune response by OVA-PDDA-NPs, thus proving that these NPs are a potent adjuvant for subunit vaccine design. Full article

Heterojunction creation is demonstrated as an effective strategy to enhance the transfer and separation of charge carriers, which is beneficial for subsequent photocatalytic reactions. In this study, “sea urchin-like” W₁₈O₄₉ was in situ-grown on the surface of Bi₁₂GeO₂₀ through a hydrothermal process, and the released Cl⁻ anions tended to produce BiOCl simultaneously. Systematical characterizations confirmed the construction of ternary composites Bi₁₂GeO₂₀/BiOCl/W₁₈O₄₉ (GBW), in which Type I and Z-scheme models were integrated to promote charge carrier migration and separation by combining the structural merits of both models. Under UV–visible light, the catalytic performance of the as-synthesized samples was tested in terms of NO oxidation removal. Compared to pure Bi₁₂GeO₂₀, the composite GBW5 showed the highest NO photocatalytic removal efficiency of 42%, which was nearly four times that of pure Bi₁₂GeO₂₀. These improvements were mainly due to enhanced light absorption, suitable morphological features, effective separation of charge carriers, and the boosted generation of reactive species in the GBW series. This study paves the way for the construction of Bi₁₂GeO₂₀-based ternary composites using a comprehensive utilization of waste method and the employment of the composites for the photocatalytic removal of low concentrations of NO at the ppb level. Full article

A novel dual Z-scheme heterojunction photocatalyst was constructed by introducing the narrow-bandgap semiconductor CuInS₂ (CIS) into the dual metal-organic framework (MOF) system of UiO-66(Zr) and NH₂-MIL-101(Fe). This structure effectively overcomes the limitations of conventional photocatalysts in terms of light absorption range and the separation efficiency of photogenerated charge carriers. The prepared ternary catalyst, (UiO-66(Zr))-(NH₂-MIL-101(Fe))/CuInS₂, exhibited excellent photocatalytic performance under visible light irradiation, achieving a hydrogen production rate of 888 μmol g⁻¹ h⁻¹ and a methylene blue (MB) degradation efficiency of up to 95.03%. The significant enhancement in performance is attributed to the material’s porous structure, extended light absorption range, and optimized electron transfer pathways. Additionally, the construction of the dual Z-scheme heterojunction further promotes the separation and migration of photogenerated charge carriers, suppressing electron–hole recombination. This study demonstrates the great potential of dual Z-scheme heterojunctions in improving photocatalytic efficiency and provides an important theoretical foundation and design strategy for the development of efficient photocatalysts. Full article

xTiO₂-(1-x)SiO₂ (x = 2.9~8.2 mol%) glass specimens were synthesized using the flame hydrolysis technique. This study aimed to elucidate the influence of TiO₂ incorporation on the optical characteristics, defect behavior, and microwave dielectric performance of these materials. UV–vis and near-infrared spectroscopic analyses were employed to investigate the hydroxyl and optical bandgap properties. Electron paramagnetic resonance (EPR) and AC impedance spectroscopy were utilized to examine oxygen vacancies, Ti³⁺ defects, and their respective behaviors. The findings revealed that, with increasing TiO₂ content, the generation and migration of defects became more favorable, consequently leading to higher dielectric losses. The imaginary component of the electric modulus experimental data was fitted using the modified Kohlrausch–Williams–Watts (KWW) function, while the frequency-dependent AC conductivity was analyzed using the Jonscher power law. The calculated activation energy exhibited a decreasing trend with increasing TiO₂ content, consistent with the characteristics of doubly ionized oxygen vacancies, suggesting the involvement of identical charge carriers in the relaxation and conduction mechanisms. Notably, the 8.2TiO₂–91.8SiO₂ glass specimen demonstrated exceptional microwave dielectric performance, exhibiting ε_r = 4.13, Q × f = 57,116 GHz, and τ_f = −4.32 ppm/°C, rendering it a promising candidate for microwave substrate applications. Full article

Perovskite solar cells (PSCs) can utilize the residual photons from indoor light and continuously supplement the energy supply for low-power electron devices, thereby showing the great potential for sustainable energy ecosystems. However, the solution-processed perovskites suffer from serious defect stacking within crystal lattices, compromising the low-light efficiency and operational stability. In this study, we designed a multifunctional organometallic salt named sodium sulfanilate (4-ABS), containing both electron-donating amine and sulfonic acid groups to effectively passivate the positively-charged defects, like under-coordinated Pb ions and iodine vacancies. The strong chemical coordination of 4-ABS with the octahedra framework can further regulate the crystallization kinetics of perovskite, facilitating the enlarged crystal sizes with mitigated grain boundaries within films. The synergistic optimization effects on trap suppression and crystallization modulation upon 4-ABS addition can reduce energy loss and mitigate ionic migration under low-light conditions. As a result, the optimized device demonstrated an improved power conversion efficiency from 22.48% to 24.34% and achieved an impressive efficiency of 41.11% under 1000 lux weak light conditions. This research provides an effective defect modulation strategy for synergistically boosting the device efficiency under standard and weak light irradiations. Full article

A form of discrimination associated with international migration is workplace discrimination. This study focused on identifying discriminatory actions in working conditions, as perceived by Venezuelan immigrants residing in Cúcuta, La Parada and Los Patios (Colombia). The goal was to determine the measures employers could implement to reduce such discriminatory actions. A quantitative, non-probabilistic snowball sampling method was adopted, followed by a survey of 177 immigrants. An exploratory and descriptive analysis of the variables under study was conducted using multivariate analysis techniques of multiple correspondences with optimal scaling. The study also explored discrimination perceived by employed and unemployed immigrants, as well as by those who had been denied work during their job search. The study concluded that to address discrimination by employers, culture should be linked to ethics and corporate social responsibility, enabling organisations to successfully raise awareness among their staff, managers and those in charge of human resource management about non-discrimination policies, equal treatment and opportunities, from design to implementation, along with necessary monitoring by Labour Inspecting Offices. Full article

Na₃V₂(PO₄)₃ (NVP), a NASICON-type material, has gained attention as a promising battery cathode owing to its high sodium mobility and excellent structural stability. Using computational simulation techniques based on classical potentials and density functional theory (DFT), we examine the defect characteristics, diffusion mechanisms, and dopant behavior of the NVP. The study found that the Na Frenkel defect is the most favorable intrinsic defect, supporting the desodiation process necessary for capacity and enabling vacancy-assisted Na-ion migration. The Na migration is anticipated through a long-range zig-zag pathway with an overall activation energy of 0.70 eV. K and Sc preferentially occupy Na and V sites without creating charge-compensating defects. Substituting Mg at the V site can simultaneously increase Na content by forming interstitials and reducing the band gap. Additionally, doping Ti at the V site promotes the formation of Na vacancies necessary for vacancy-assisted migration, leading to a notable improvement in electronic conductivity. Full article

The light oil wells within the Neogene Shawan Formation have been extensively drilled in the Chepaizi Uplift, reflecting an increase that provides new targets for unconventional resources in the Junggar Basin of northwestern China. However, the original sources of light oil remain controversial, as several source rocks could potentially generate the oil. For this study, we collected light oils and sandstone cores for biomarker detection using gas chromatography–mass spectrometry (GC-MS). Additionally, fluid inclusions were observed and described, and the homogenization temperatures of saltwater inclusions were measured to confirm the oil charging history in conjunction with well burial and thermal history analysis. Based on these geochemical characteristics and carbon isotopic analysis, the results indicate that light oil in the Chepaizi Uplift zone primarily originates from Jurassic hydrocarbon source rocks in the Sikeshu depression, with some contribution from Cretaceous hydrocarbon source rocks. Jurassic hydrocarbon source rocks reached a peak of hydrocarbon generation in the middle to late Neogene. The resulting crude oil predominantly migrated along unconformities or faults to accumulate at the bottom of the Cretaceous or Tertiary Shawan Formation, forming anticlinal or lithologic oil reservoirs. Some oil reservoirs contain mixtures of Cretaceous immature crude oil. During the Neogene light oil accumulation process, the burial rate of reservoirs was high, and the efficiency of charging and hydrocarbon supply was relatively high as well. Minimal loss occurred during the migration of light oil, which significantly contributed to its rapid accumulation. Full article

A novel spherical MoS₂/WO₃ composite was fabricated via a hydrothermal method for the photocatalytic degradation of RhB from wastewater. The structure and morphology of the photocatalyst were systematically characterized. The MoS₂/WO₃ nanospheres formed a p-n heterojunction, with charge migration following a Z-scheme mechanism. The MoS₂/WO₃ composites exhibited superior photocatalytic activity, achieving a 94.5% degradation rate for RhB in just 60 min under visible light irradiation, far surpassing the performance of pure WO₃ and MoS₂. This enhanced activity was attributed to the improved charge separation efficiency and redox capacity, enabled by the unique “layer–bending layer” growth mode. The composite’s transfer resistance (R_ct) was as low as 7.42 × 10² Ω, promoting faster electrochemical reactions. With a maximum photocurrent density of 87 μA·cm⁻², the composite rapidly separated photogenerated electron–hole pairs. The primary reactive species in the photocatalytic reaction were ·OH and O₂⁻, with h⁺ playing a secondary role. Full article