Search Results (479)

The potential of graphene for electric field sensing is limited by its zero bandgap. This study employs a combined first-principles and experimental approach to enhance its response via heterojunctions with ZnO, SnO₂, and Al₂O₃. Calculations reveal spontaneous formation and interfacial charge transfer in all systems, with SnO₂/graphene exhibiting the most significant charge transfer (0.3636 e) and inducing a finite bandgap (0.017–0.064 eV). Experimentally, SnO₂-graphene/PDMS composites demonstrated the highest relative permittivity (3.19) and a 7.76% increase in normalized induced voltage over pure PDMS within 50 Hz–50 kHz. This work establishes a direct correlation between interfacial charge transfer, bandgap opening, and macroscopic dielectric enhancement, identifying SnO₂/graphene as the optimal heterojunction. The integrated multi-scale methodology provides a clear design principle for high-performance, graphene-based field-sensitive materials. Full article

Multiband solar cells offer a promising route to surpass the Shockley-Queisser limit by harnessing sub-bandgap photons through three active energy band transitions. However, realizing their full potential requires overcoming key challenges in material design and device architecture. Here, we propose a novel multiband stacked anti-parallel junction solar cell structure based on highly mismatched alloys (HMAs), in particular dilute GaAsN with ~1–4% N. An anti-parallel junction consists of two semiconductor junctions connected with opposite polarity, enabling bidirectional current control. The structures of the proposed devices are based on dilute GaAsN with anti-parallel junctions, which allow the elimination of tunneling junctions—a critical yet complex component in conventional multijunction solar cells. Semiconductors with three active energy bands have demonstrated the unique properties of carrier transport through the stacked anti-parallel junctions via tunnel currents. By leveraging highly mismatched alloys with tailored electronic properties, our design enables bidirectional carrier generation through forward- and reverse-biased diodes in series, significantly enhancing photocurrent extraction. Through detailed SCAPS-1D simulations, we demonstrate that strategically placed blocking layers prevent carrier recombination at contacts while preserving the three regions of photon absorption in a single multiband semiconductor p/n junction. Remarkably, our optimized five-stacked anti-parallel junctions structure achieves a maximum theoretical conversion efficiency of 70% under 100 suns illumination, rivaling the performance of state-of-the-art six-junctions III-V solar cells—but without the fabrication complexity of multijunction solar cells associated with tunnel junctions. This work establishes that highly mismatched alloys are a viable platform for high efficiency solar cells with simplified structures. Full article

Mechanical vibrations in lightweight structures remain a persistent challenge, often leading to noise, fatigue, and performance degradation in aerospace, automotive, and industrial applications. Recent advances in phononic crystals and perforated metaplates have shown that periodic cavities or uniformly distributed perforations can generate bandgaps and reduce vibration transmission. However, most existing designs rely on identical and regularly spaced holes, which limits the ability to precisely tune the attenuation response. This work introduces a novel design and optimization framework for finite perforated cellular panels, in which each perforation diameter is individually optimized to achieve targeted vibration suppression within specific frequency ranges. Finite element models were coupled with a Particle Swarm Optimization (PSO) algorithm to minimize the frequency response function (FRF) amplitude. Aluminum panels with 16 and 25 perforations were optimized, fabricated via CNC machining, and experimentally validated using impact hammer tests. The optimized designs achieved up to 90% reduction in vibrational amplitude within the target frequency bands, demonstrating strong agreement between numerical predictions and experimental results. These results highlight the potential of non-periodic, locally optimized perforation patterns as a practical and scalable approach for vibration control in finite structural components. Full article

The growing prevalence of emerging contaminants in the aquatic environment poses a critical challenge to global water security. Conventional treatment methods often fail to remove persistent pollutants, necessitating the development of sustainable and efficient alternatives. Heterogeneous photocatalysis, one of the advanced oxidation processes, driven by the light-induced generation of reactive species, has emerged as a promising solution. However, the high cost and environmental footprint of conventional photocatalysts limit large-scale implementation. This review explores the innovative use of waste-derived materials, originating from agricultural residues, industrial by-products, food waste, and electronic waste, as green precursors for photocatalyst synthesis. These materials offer unique structural and chemical properties, including a high surface area, tunable bandgaps, and enhanced stability, while supporting circular economy principles. Recent advances in synthesis strategies, performance optimization, and hybrid system integration are critically analyzed, alongside challenges related to scalability, environmental safety, and process standardization. Waste-to-resource approaches in photocatalysis represent a transformative pathway toward sustainable water treatment and resource recovery. Full article

Microplastics, plastic particles smaller than 5 mm, are now ubiquitous and represent a form of pollution that threatens ecosystems and human health, infiltrating the environment, air, and food chain. The search for solutions to microplastics requires industrial policies that limit plastic production and technological innovations for removal and recycling. Specifically, this paper reports a sustainable and cost-effective method for the detection of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) microplastics using nitrogen-doped carbon dots (N-CD) synthesized from onion peel and L-cysteine via hydrothermal carbonization. Two precursor ratios (1:1 and 1:0.30 w/w) were evaluated. The resulting N-CDs exhibited bright yellow-green fluorescence (470–500 nm) and excitation-dependent photoluminescence under 365 nm UV light. FTIR and UV-Vis spectroscopy confirmed the presence of nitrogen-containing functional groups and effective graphitization, particularly in the 1:0.30 ratio. Fluorescence imaging revealed stronger intensity and greater stain uniformity in thermally softened MPs treated with 1:0.30 N-CDs, with a peak emission of 10,230.02 a.u. at 2 h and PMT 11—surpassing the 1:1 ratio. Bandgap and absorbance analyses supported the superior optical behavior of the lower-concentration formulation. Image analysis further indicated increased luminescent area over time, and two-way ANOVA confirmed statistically significant effects of heating time and PMT settings (p < 0.05). Compared to traditional filtration staining, thermal-assisted application offered enhanced and stable fluorescence. These findings demonstrate the efficacy of green-synthesized N-CDs for MP detection, with potential scalability and environmental applicability. Future work should explore alternative biomass sources and assess N-CD performance under field conditions to optimize environmental sensing strategies. Full article

The exponential growth of artificial intelligence (AI), electrified transport, and renewable generation is accelerating a structural shift in how societies produce, deliver, and consume electricity. We argue that the next frontier is not incremental efficiency but Energy Intelligence (EI): the embedding of predictive analytics, adaptive control, and material-aware design directly into power-conversion hardware. In this view, power electronics functions as the cognitive layer that links digital intelligence to the physical flow of energy. Wide-bandgap (WBG) semiconductors—gallium nitride (GaN) and silicon carbide (SiC)—provide the material foundation for higher switching frequencies, superior power density, and real-time controllability, enabling compact and efficient converters for data-centers, EV charging, and grid-interactive resources. We formalize an EI reference architecture (predictive, adaptive, material-efficient, data-driven), review the convergence of AI methods with converter design and operation, and outline a GaN/SiC-enabled data-center power path as an illustrative case. Finally, we examine sustainability and sovereignty, highlighting exposure to critical materials (Ga, Si, In, rare earths) and proposing a roadmap that integrates technology, policy, and education. By reframing power electronics as an intelligent, learning infrastructure, this work sets an agenda for systems that are not only efficient but also self-optimizing, explainable, and resilient. Full article

Wide bandgap (WBG) power semiconductors such as silicon carbide (SiC) can significantly improve the performance of multilevel converters. However, there are three challenges for large-scale application: high cost, limited power ratings, and reliability issues. In this paper, we propose a Si and SiC hybrid arms active neutral-point-clamped (ANPC) converter, using smaller current rating SiC devices compared to other Si devices in this topology. By employing the hybrid-frequency modulation scheme, the Si devices switch at fundamental frequency (FF) or low frequency (LF), while the SiC devices switch at high frequency (HF). The equivalent circuit of the proposed converter is derived to analyze the principle of LF current ripple compensation. The closed-loop cooperative current control strategy is proposed to realize unequal current sharing in two arms and complete LF current ripple compensation. The Si arm processes major power, while the SiC arm compensates the LF current ripple generated by the Si arm and processes minor power. The proposed topology and control strategy are validated by simulation and experimental results. Compared with the existing typical topologies, the comprehensive optimization of power quality, efficiency, and cost is realized. Full article

This study investigates the application of phononic crystal plates for automotive vibration and noise attenuation through a combined material–structure design approach. Four materials—aluminum, lead, epoxy resin, and plexiglass—were selected to construct a composite plate with a low-density matrix and high-density metallic inclusions. Finite element modeling in COMSOL Multiphysics identified organic glass–lead as the optimal configuration, balancing wide bandgap performance with low-frequency characteristics and lightweight requirements. Parametric analysis demonstrated that rectangular inclusions provide the widest bandgap under equal area conditions, and increasing their volume fraction shifts the bandgap to lower frequencies while broadening its width. The study verifies the reliability of the finite element method (FEM) and further explains the formation mechanism of the bandgap. This study proposes a phononic crystal plate structure with optimal performance: a rectangular phononic crystal plate with a length of A = 20 mm and a height of B = 10 mm serves as the matrix, and four identical rectangular inclusions each with an area of S = 16 mm² are embedded in it. The matrix material is organic glass, while the material of the inclusions is lead. The resulting optimized structure exhibits a complete Lamb wave bandgap from 6.29 to 22.03 kHz, with strong elastic wave attenuation extending over 6.00–30.00 kHz. Acoustically, it achieves sound transmission loss (STL) exceeding 130 dB within 5.85–27.91 kHz, peaking at 143.99 dB. These results verify the structure’s dual functionality in simultaneous vibration isolation and sound attenuation within the same frequency range, demonstrating the potential of phononic crystal plates for targeted noise and vibration control in automotive engines and rotating machinery. Full article

We introduce a fully solution-processed interlayer strategy for n–p CdS/PbS thin film solar cells that combines a sol–gel ZnO compact coating with an electrospun ZnO nanofiber network. The synthesis and characterization of ZnO, CdS, and PbS thin films, complemented by electrospun ZnO nanofibers, are aimed at low-cost photovoltaic applications. Sol–gel ZnO films exhibited a hexagonal wurtzite structure with a bandgap (Eg) of approximately 3.28 eV, functioning effectively as electron transport and hole-blocking layers. CdS films prepared by chemical bath deposition (CBD) showed mixed cubic and hexagonal phases with an Eg of about 2.44 eV. PbS films deposited at low temperature displayed a cubic galena structure with a bandgap of approximately 0.40 eV. Scanning Electron Microscopy revealed uniform ZnO and CdS surface coatings and a conformal 1D ZnO network with nanofibers measuring about 50 nm in diameter (ranging from 49.9 to 53.4 nm), which enhances interfacial contact coverage. PbS films exhibited dense grains ranging from 50 to 150 nm, and EDS confirmed the expected stoichiometries. Electrical characterization indicated low carrier densities and high resistivities consistent with low-temperature processing, while mobilities remained within reported ranges. The incorporation of ZnO layers and nanofibers significantly improved device performance, particularly at the CdS/PbS heterojunction. The device achieved a V_oc of 0.26 V, an J_sc of 3.242 mA/cm², and an efficiency of 0.187%. These improvements are attributed to enhanced electron transport selectivity and reduced interfacial recombination provided by the percolated 1D ZnO network, along with effective hole blocking by the compact film and increased surface area. Fill-factor limitations are linked to series resistance losses, suggesting potential improvements through fiber densification, sintering, and control of the compact layer thickness. This work is a proof-of-concept of a fully solution-processed and low-temperature CdS/PbS architecture. Efficiencies remain modest due to low carrier concentrations typical of low-temperature CBD films and the deliberate omission of high-temperature annealing/ligand exchange. Overall, this non-vacuum, low-temperature coating method establishes electrospun ZnO as a tunable functional interlayer for CdS/PbS devices and offers a practical pathway to elevate power output in scalable productions. These findings highlight the potential of nanostructured intermediate layers to optimize charge separation and transport in low-cost PbS/CdS/ZnO solar cell architectures. Full article

Barium disilicide (BaSi₂) was identified as a promising silicon-based photovoltaic absorber due to its near-optimal bandgap, strong optical absorption, and earth-abundant composition. However, the performance of BaSi₂ thin-film solar cells was severely restricted by structural defects and interfacial instabilities that introduced localized electronic states and facilitated non-radiative recombination. These imperfections degraded carrier lifetime, mobility, and open-circuit voltage. This review systematically examined the formation, energetics, and electronic roles of intrinsic and extrinsic defects in BaSi₂ thin films, and evaluated nanoscale passivation strategies developed to mitigate defect-induced losses. Chemical, dielectric, and interfacial approaches were critically analyzed with emphasis on their underlying mechanisms, limitations, and integration potential. The convergence of in situ characterization, first-principles modeling, and data-driven process optimization was expected to enable predictive defect control and rational interface design, thereby advancing BaSi₂-based photovoltaics toward practical implementation. Full article

To address the challenges of low solar energy utilization efficiency and rapid recombination of photogenerated charge carriers in photocatalytic hydrogen evolution, this study successfully constructed a composite photocatalyst of ZnIn₂S₄ (ZIS) supported on N-doped hollow carbon spheres (N-HCS), denoted as ZIS/N-HCS, via a combination of template etching and in situ growth strategies. Characterization results demonstrate that this hollow structure possesses a high specific surface area (48.41 m²/g) and a narrowed bandgap (2.41 eV), achieve broad-spectrum light absorption, thereby enabling the catalyst to generate a local hot spot temperature of 136 °C under AM1.5G conditions. The optimized ZIS/N-HCS-0.30 sample exhibited a significantly enhanced photocurrent response (8.26 μA cm⁻²) and improved charge separation efficiency. When evaluated at a set solution temperature of 20 °C, the material exhibited a photocatalytic hydrogen evolution rate of 17.03 mmol g⁻¹·h⁻¹, which is 7.06 times higher than that of pure ZIS. Furthermore, it demonstrated excellent cycling stability. This work elucidates the synergistic role of the hollow photothermal structure in enhancing solar energy utilization and catalytic reaction kinetics, providing a new strategy for designing efficient solar-driven hydrogen production systems. Full article

Continuous flow synthesis and microwave-assisted synthesis represent two sustainable and efficient methods for polymer production aligned with green chemistry principles, compared to conventional polymer synthesis. Here we present a case study of poly(4,4-dioctyldithieno(3,2-b:2′,3′-d)silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl (PSBTBT), a low band-gap electron-donating polymer for organic photovoltaics (OPVs). The PSBTBT Stille cross-coupling polymerization conditions were optimized by comparing different synthetic methods: conventional, flow, and microwave. To assess the impact of the different synthetic methods, detailed molecular and spectroscopic characterization, highlighting both the differences and similarities within the methodologies, was performed with several techniques, such as GPC, UV-Vis, PL, and NMR. Full article

Enhancing TiO₂ performance is essential for advancing photocatalysis, environmental remediation, and energy conversion technologies. In this work, nanosized TiO₂ was modified with biochar (BC) derived from red sea algae at different loadings (0, 5, 10, and 15 wt%). Structural analysis confirmed that TiO₂ maintained its crystalline framework while biochar introduced additional amorphous features and modified surface morphology. Optical measurements revealed a redshift in the absorption edge and tunable bandgap values (3.28–3.72 eV), accompanied by increases in refractive index and extinction coefficient, indicating enhanced light–matter interactions. Electrochemical studies demonstrated that the TiO₂/5 wt% BC composite exhibited the lowest charge-transfer resistance and highest peak current, reflecting superior conductivity. Photocatalytic tests showed that TiO₂/5 wt% BC achieved nearly 84% degradation of methylene blue within 150 min under visible-light irradiation, with stable reusability over multiple cycles. These findings demonstrate that moderate biochar incorporation (5 wt%) optimally enhances the physicochemical, electrochemical, and photocatalytic properties of TiO₂, making it a promising candidate for wastewater treatment, solar-driven catalysis, and sustainable energy applications. Full article

Monitoring nitrogen dioxide (NO₂) in various scenarios is crucial due to its significant environmental impact as a hazardous gas which is emitted by several industrial sectors. This study reports the optimized synthesis of WO₃ flower-like structures using the microwave-assisted hydrothermal method under various experimental conditions, resulting in the optimized sample designated MF-WO₃-K2. Structural, morphological, and chemical characterizations revealed that WO₃ microflowers (MF-WO₃-K2) exhibit a hexagonal crystalline phase, a bandgap of 2.4 eV, and a high specific surface area of 61 m²/g. The gas-sensing performance of WO₃ microflowers was investigated by electrical measurements of six similarly fabricated MF-WO₃-K2 sensors. The MF-WO₃-K2 sensors demonstrated a remarkable sensor signal of 225 for 5 ppm NO₂ at 150 °C and response/recovery times of 14.5/2.4 min, coupled with outstanding selectivity against potential interfering gases such as CO, H₂, C₂H₂, and C₂H₄. Additionally, the sensors achieved a low detection limit of 65 ppb for NO₂ at 150 °C. The exceptional sensing properties of WO₃ microflowers are attributed to the abundance of active sites on the surface, large specific surface area, and the presence of pores in the material that facilitate the diffusion of NO₂ molecules into the structure. Overall, the WO₃ microflowers demonstrate a promising ability to be used as a sensitive layer in high-performance chemiresistive gas sensors due to their high sensor performance and good reproducibility for NO₂ detection. Full article

Aluminum nitride (AlN) is a wide-bandgap semiconductor (6.2 eV) with a broad transparency window spanning from the ultraviolet (UV) to the mid-infrared (MIR) wavelength region, making it a promising material for integrated photonics. In this work, AlN thin films using reactive RF sputtering are deposited, followed by annealing at 600 °C in a nitrogen atmosphere to reduce slab waveguide propagation losses. After annealing, the measured loss is 0.84 dB/cm at 978 nm, determined using the prism coupling method. A complete microfabrication process flow is then developed for the realization of optical channel waveguides. A key challenge in the processing of AlN is its susceptibility to oxidation when exposed to water or oxygen plasma, which significantly impacts device performance. The process is validated through the fabrication of microring resonators (MRRs), used to characterize the propagation losses of the AlN channel waveguides. The fabricated MRRs exhibit a quality factor of 12,000, corresponding to a propagation loss of 4.4 dB/cm at 1510–1515 nm. The dominant loss mechanisms are identified, and strategies for further process optimization are proposed. Full article