Search Results (1,176)

Defective graphene has emerged as a promising strategy to enhance electrochemical performance of pristine graphene (p-Gr) as anodes in lithium-ion batteries (LIBs). Herein, we perform a comprehensive first-principles study based on density functional theory (DFT) to systematically investigate the Li adsorption, charge transfer, and diffusion behaviors of p-Gr and defective graphene (d-Gr) with single vacancy (SV Gr) and double vacancy (DV5-8-5 Gr) defects, aiming to clarify the mechanism by which defects modulate Li storage performance. Structural optimization reveals that SV Gr undergoes notable out-of-plane distortion after Li adsorption, while DV5-8-5 Gr retains planar geometry but exhibits more significant C-C bond length variations compared to p-Gr. Binding energy results confirm that defects enhance Li adsorption stability, with DV5-8-5 Gr showing the strongest Li–graphene interaction, followed by SV Gr and p-Gr. Bader charge analysis and charge density difference plots further validate that defects enhance charge transfer from Li ions to graphene. Using the nudged elastic band (NEB) method, we find that defects reduce Li diffusion barriers: DV5-8-5 Gr exhibits a lower barrier than p-Gr. Our findings demonstrate that DV5-8-5 Gr exhibits the most favorable Li storage performance, providing a robust theoretical basis for designing high-performance graphene anodes for next-generation LIBs. Full article

Metal halide perovskite (MHP)-based heterojunctions have become a forefront area in the research of optoelectronic functional materials due to their unique layered crystal structure, tunable band gaps, and exceptional optoelectronic properties. Recent studies have demonstrated that interface charge transfer is a crucial factor in determining the optoelectronic performance of the heterojunction devices. By constructing heterojunctions between MHPs and two-dimensional (2D) materials such as graphene, MoS₂, and WS₂, efficient electron–hole separation and transport can be achieved, significantly extending carrier lifetimes and suppressing non-radiative recombination. This results in enhanced response speed and energy conversion efficiency in photodetectors, photovoltaic devices, and light-emitting devices (LEDs). In these heterojunctions, the thickness of the MHP layer, interface defect density, and band alignment significantly influence carrier dynamics. Furthermore, techniques such as interface engineering, molecular passivation, and band engineering can effectively optimize charge separation efficiency and improve device stability. The integration of multilayer heterojunctions and flexible designs also presents new opportunities for expanding the functionality of high-performance optoelectronic devices. In this review, we systematically summarize the charge transfer mechanisms in MHP-based heterojunctions and highlight recent advances in their optoelectronic applications. Particular emphasis is placed on the influence of interfacial coupling on carrier generation, transport, and recombination dynamics. Furthermore, the ultrafast dynamic behaviors and band-engineering strategies in representative heterojunctions are elaborated, together with key factors and approaches for enhancing charge transfer efficiency. Finally, the potential of MHP heterojunctions for high-performance optoelectronic devices and emerging photonic systems is discussed. This review aims to provide a comprehensive theoretical and experimental reference for future research and to offer new insights into the rational design and application of flexible optoelectronics, photovoltaics, light-emitting devices, and quantum photonic technologies. Full article

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

Aluminum alloys require improved surface performance to satisfy the demands of today’s aerospace, automotive, marine, and structural applications. This paper compares three key surface hardening methods: diffusion-assisted microalloying, thermomechanical deformation-based treatments, and composite/hybrid reinforcing procedures. Diffusion-assisted Zn/Mg enrichment allows for localized precipitation hardening but is limited by the native Al₂O₃ barrier, slow solute mobility, alloy-dependent solubility, and shallow hardened depths. In contrast, thermomechanical techniques such as shot peening, surface mechanical attrition treatment (SMAT), and laser shock peening produce ultrafine/nanocrystalline layers, high dislocation densities, and deep compressive residual stresses, allowing for predictable increases in hardness, fatigue resistance, and corrosion performance. Composite and hybrid reinforcement systems, such as SiC, B₄C, graphene, and graphite-based aluminum matrix composites (AMCs), use load transfer, Orowan looping, interfacial strengthening, and solid lubrication effects to enhance wear resistance and through-thickness strengthening. Comparative evaluations show that, while diffusion-assisted procedures are still labor-intensive and solute-sensitive, thermomechanical treatments are more industrially established and scalable. Composite and hybrid systems provide the best tribological and load-bearing performance but necessitate more sophisticated processing approaches. Recent corrosion studies show that interfacial chemistry, precipitate distribution, and galvanic coupling all have a significant impact on pitting and stress corrosion cracking (SCC). These findings highlight the importance of treating corrosion as a fundamental design variable in all surface hardening techniques. This work uses unified tables and drawings to provide a thorough examination of strengthening mechanisms, corrosion and fatigue behavior, hardening depth, alloy suitability, and industrial feasibility. Future research focuses on overcoming diffusion barriers, establishing next-generation gradient topologies and hybrid processing approaches, improving strength ductility corrosion trade-offs, and utilizing machine-learning-guided alloy design. This research presents the first comprehensive framework for selecting multifunctional aluminum surfaces in demanding aerospace, automotive, and marine applications by seeing composite reinforcements as supplements rather than strict alternatives to diffusion-assisted and thermomechanical approaches. Full article

DFT study of graphene functionalized via carbene was performed to identify the preferred –OH adsorption sites and to assess how hydroxylation affects adsorption of NH₃ gas. The carbene attaches to the graphene basal plane through a [2+1] cycloaddition, producing a local cyclopropane-like motif with a C–C bond. This modification introduces localized mid-gap states and asymmetric charge redistribution that create chemically active anchoring sites for –OH groups. We systematically scanned possible –OH adsorption sites and identified site-dependent binding energies. NH₃ preferentially anchors at the carbene center and is further stabilized by multidentate hydrogen bonding with neighboring –OH groups. Calculated NH₃ adsorption energies range from moderate values (single –OH and some two –OH symmetric sites, E_ads ≈ −0.64 to −0.75 eV) to strong interaction for selected through-plane two –OH pairs (E_ads ≈ −1.78 to −1.83 eV), where synergistic hydrogen bonding amplifies the NH₃ interaction. Charge density difference and Bader analyses indicate polarization-dominated binding with minimal net charge transfer, consistent with hydrogen bonding rather than covalent bond formation. Desorption time estimation shows that moderate binding motifs provide rapid recovery at room temperature. We conclude that targeted placement of paired –OH groups on carbene-functionalized graphene offers a tunable route to balance sensitivity and reusability for NH₃ sensing. Full article

To increase the use of the near-infrared (NIR) light from In₂O₃, a nanocomposite of In₂O₃/reduced graphene oxide was synthesised. To improve adhesion to the substrates, a small amount of PVA (polyvinyl alcohol) was added to the nanocomposite. Results showed that adding an appropriate amount of PVA to the nanocomposite remarkably enhanced the ability to extract photogenerated carriers due to interface optimisation based on the grain boundary filling with PVA and charge tunnelling effects. The nanocomposites exhibited photoconductive switching responses from the visible light region to the near-infrared range. Meanwhile, the organic/inorganic hybrid coating on silk fibres exhibited mutual conversion of positive and negative photoconductivity, as well as electrical switching responses to applied strain. Furthermore, it was found that a photoelectric signal could still be determined with zero bias after the In₂O₃/reduced graphene oxide nanocomposite had been stored for over four years. This reflects that the nanocomposites have an internal electric field that promotes the transfer of photogenerated carriers and prevents the recombination of photogenerated electrons and holes. Similar results were also obtained by adding an appropriate amount of other non-conjugated polymers, such as dendrimers. Physical mechanisms are discussed. This study provides reference values for the development of multifunctional organic/inorganic hybrids integrating non-conjugated polymer components to enhance specific properties. Full article

The integration of 2D materials with artificially textured substrates offers exceptional opportunities for engineering novel functional devices. A straightforward technological route towards such devices is a mechanical dry or wet transfer of 2D layer or heterostructure onto prepared patterned elements with subsequent van der Waals bonding. An issue of van der Waals bond stability is crucial for device operation but is almost unexplored. In our research, we address it by studying transport properties of hBN/graphene heterostructures transferred onto metallic island arrays and subjected to thermal cycling. We reveal that heating from cryogenic to room temperature and cooling back leads to irreversible changes in electronic transport properties: the contact between metal and graphene degrades, and signatures of suspended graphene regions transport disappear. These changes are accompanied by slight movement of the flakes and atomic-force-microscope-detected breakdown of van der Waals bonds between the flake and substrate near the metal electrodes. Interestingly, a hot pressing allows us to restore the metal-to-graphene contact. We relate the observed metastability to the thermal-expansion-driven flake delamination and argue that it is accompanied by redistribution of the interfacial water or organic residues. Our findings provide useful insights into the topic of interfacial stability in van der Waals heterostructures and establish constraints for low-temperature applications of transferred 2D devices. We also add up an additional control parameter for the experimentalists in the field of 2D materials—degree of quenched disorder. Full article

Sulfated nanocellulose (SCNF) and reduced graphene oxide (rGO) films were fabricated through environmentally friendly methods to develop an effective platform for electrochemical applications. The hybrid materials were extensively characterized by FTIR, XRD, Raman spectroscopy, TGA, SEM, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Results showed that incorporating rGO into the SCNF matrix significantly improved the electrical conductivity and structural robustness of the films. FTIR confirmed interactions between sulfate groups on cellulose and residual oxygen-containing groups on rGO, while XRD and Raman analyses indicated reduced crystallinity and increased structural disorder, supporting the successful integration of both phases. XPS further demonstrated that SCNF and rGO form chemical bonds rather than simply mixing, with both components remaining active at the surface—evidence of strong interfacial interactions that contribute to enhanced stability and efficient charge transfer. The 1:5 (rGO:SCNF) composition showed the best electrochemical performance, exhibiting minimal charge-transfer resistance and improved hydrazine oxidation, as reflected by a shift of the anodic peak potential toward lower values. Additionally, functionalization with cobalt porphyrin significantly boosted catalytic activity. Overall, the SCNF:rGO films offer a sustainable and scalable platform for electrochemical sensing and energy-conversion applications, demonstrating excellent adaptability and functional performance. Full article

Reducing the Schottky barrier at the metal–semiconductor interface and achieving Ohmic contact is crucial for the development of high-performance Schottky field-effect transistors. This paper investigates the stability, interface interactions, interlayer charge transfer, and types of Schottky contacts in the graphene/ZnSe heterostructure structure using first-principles methods. It employs biaxial strain as a control mechanism. The results indicate that applying compressive strain increases the barrier and band gap while maintaining n-type contact; whereas tensile strain reduces the n-type barrier to negative values, inducing Ohmic contact and decreasing the band gap. The findings of this study will provide theoretical references for the design and fabrication of field-effect transistors, photodetectors, and other optoelectronic devices. Full article

Single-atom catalysts are highly efficient electrocatalysts for water splitting with exceptional atomic utilization, but atomic aggregation can impair their catalytic performance. To address this challenge, a Fe-Co-Ni single-atom bifunctional catalyst supported on nitrogen-doped graphene oxide was designed and employed for overall water splitting in alkaline electrolyte. The catalyst’s composition, structure, and morphology were systematically characterized using XRD, XPS, SEM, and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Electrochemical evaluations were performed to assess its activity and stability toward both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The results demonstrate that strong metal-nonmetal interactions between the Fe, Co and Ni single atoms and the nitrogen-doped graphene oxide support facilitate stable and uniform anchoring of the metal centers on the wrinkled carbon framework. The total metal loading reaches approximately 6.78 wt%, ensuring a high density of accessible active sites. Furthermore, synergistic electronic coupling among the Fe, Co, and Ni centers enhances charge transfer kinetics and modulates the D-band electronic states of the metal atoms. This effect weakens the adsorption strength of hydrogen and oxygen-containing intermediates, thus promoting faster reaction kinetics for both HER and OER. Consequently, the FeCoNi/CNG catalyst delivers low overpotentials of 77 mV for HER and 355 mV for OER at a current density of 10 mA cm⁻² in alkaline conditions. When integrated into an alkaline water electrolyzer, the system achieves a cell voltage of only 1.68 V to attain a current density of 10 mA cm⁻², underscoring its outstanding bifunctional catalytic performance. Full article

In this paper, a simple hydrothermal approach is employed to prepare nitrogen-doped graphene quantum dots (N-GQDs) with controllable size and structural features, where citric acid and ethylenediamine served as the carbon and nitrogen precursors, respectively. The influence of hydrothermal temperature and duration on the structural features, surface chemistry, and electrochemical behavior of N-GQDs is systematically investigated. The capacitive behavior of N-GQD electrodes exhibits typical pseudocapacitive characteristics, primarily attributed to the surface functional groups. The NG-2 electrode (180 °C, 6 h) demonstrates a specific capacitance of 309.8 F g⁻¹ at 1 A g⁻¹ and maintains 98.1% of its initial capacitance after 8000 cycles, confirming excellent stability. Density functional theory (DFT) results demonstrate that the co-presence of graphitic and pyrrolic nitrogen induces a synergistic modulation of the electronic structure, resulting in improved charge-transfer kinetics and surface reactivity of N-GQDs compared to single-type nitrogen doping. Additionally, NG-2//activated carbon (AC)-asymmetric supercapacitor (ASC) achieves an energy density of 22.5 Wh kg⁻¹ at 500 W kg⁻¹ and maintains outstanding cycling stability. This work provides valuable insights into the design and application of N-GQDs for advanced energy storage devices. Full article

This study presents a novel strategy for controlling the orientation of MoS₂ films on thick metallic substrates through precise regulation of the sulfur flux alone. In contrast to previous approaches that rely on substrate modifications or complex parameter tuning, orientation control is achieved here solely by adjusting the sulfur concentration during the sulfurization of 400 nm RF-sputtered Mo films. The metallic Mo substrate also allows potential film transfer via selective etching—analogous to the graphene/Cu system—providing a viable route for device integration on arbitrary substrates. Analyses (XRD, Raman, and TEM) reveal that low sulfur flux (30–50 sccm) favors horizontal growth, whereas high flux (>300 sccm) induces vertical orientation. To rationalize this behavior, a reaction-diffusion model based on the Thiele modulus was developed, quantitatively linking sulfur flux to film orientation and identifying critical thresholds (~50 and ~300 sccm) governing the horizontal-to-vertical transition. This unified approach enables the realization of distinct MoS₂ orientations using identical materials and processes, analogous to the orientation control in graphene growth on copper. The ability to grow orientation-controlled MoS₂ on non-noble metal substrates opens new opportunities for integrating electronic (horizontal) and catalytic (vertical) functionalities, thereby advancing scalable manufacturing of TMDC-based technologies. Full article

We present a flexible pH sensor which leverages the unique properties of reduced graphene oxide/polyaniline (rGO/PANI) composite films through an efficient and scalable hybrid microfabrication approach, wherein the rGO/PANI films are conformally coated on flexible polyethylene terephthalate (PET) substrates via dip-coating and thereafter lithographically patterned into precise arrays of interdigitated electrodes (IDEs), serving both as the pH-active medium and the electrical interface. Upon dip-coating, a thermal reduction process is performed to yield uniform rGO/PANI composite layers on PET substrates, where the PANI content is adjusted to 20% to optimize conductivity and protonation-driven response. Composition optimization is first performed using inkjet-printed silver (Ag) contacts and a conductometric readout mechanism is employed to explore pH-dependent behavior. Subsequently, IDE arrays are defined in the rGO/PANI using photolithography and oxygen-plasma etching, demonstrating clean pattern transfer and dimensional control on flexible substrates. Eliminating separate contact metals in the final design simplifies the stack and reduces cost. A set of IDE geometries is evaluated through I–V measurements in buffers of different pH values, revealing a consistent, monotonic change in electrical characteristics with pH and geometry-tunable response. The present study demonstrated that the most precise pH measurement was achieved with an 80:20 rGO/PANI composition within the pH 2–10 range. These results establish rGO/PANI IDEs as a scalable route to low-cost, miniaturized, and mechanically compliant pH sensors for field and in-line monitoring applications. Full article

In this work, we analyze how the coupling prism governs the performance of reduced-graphene-oxide (rGO)-assisted surface plasmon resonance (SPR) sensors for trace heavy-metal detection in water. A Kretschmann multilayer at 633 nm with a fixed Cu/Si₃N₄/rGO stack (45.0/5.00/1.41 nm) is modeled by transfer-matrix methods while varying the prism material among CaF₂, BK7, SiO₂, and SF₆. Performance optimization is carried out using angular sensitivity, full width at half maximum (FWHM), figure of merit (FoM), detection accuracy (DA), quality factor (QF), and a practical limit of detection (LoD). The analyte is represented by refractive-index typical of clean and contaminated water (n = 1.330 and 1.340). SF₆ yields the narrowest angular resonances but compresses analyte-induced angle spacing; CaF₂ provides larger analyte separations and consequently higher FoM and lower LoD under angle-encoded readout. The rGO interlayer enhances surface interaction across all prisms when co-tuned with the Cu and Si₃N₄ thicknesses. The sensitivity peaks around 310–320°·RIU⁻¹ for CaF₂. These results highlight the prism as a primary design variable in rGO-enhanced SPR sensing and position CaF₂-coupled architectures as promising for compact water-quality monitoring. Full article

Electro-Fenton (EF) technology holds significant promise for degrading recalcitrant organic pollutants. Still, it faces distinct challenges in high-pollutant-load wastewater, including insufficient radical generation, electrode passivation, and mass transfer limitations. This review systematically organizes recent advances in material design and operational strategies to address these issues. We highlight innovative cathode materials (e.g., graphene-based structures, carbon nanotubes, and metal–organic frameworks), stable anodes such as boron-doped diamond, and catalysts tailored for harsh conditions. Key operational improvements are discussed, including pH adaptability, current density optimization, and oxygen supply enhancement. The integration of hybrid systems, such as bio-electro-Fenton and photo-electro-Fenton, is also examined. Looking forward, future research for treating high-pollutant load wastewater should focus on: (1) Developing electrodes and catalysts with superior antifouling properties and long-term stability in high-strength, complex wastewaters; (2) Constructing intelligent control systems capable of real-time response to water quality fluctuations for adaptive parameter optimization; (3) Exploring energy-efficient, self-sustaining EF systems coupled with renewable energy sources or incorporating energy recovery units. This review aims to provide a comprehensive reference for subsequent research endeavors and practical applications related to the treatment technology of EF systems in high-pollutant-load wastewater contexts. Full article