Search Results (1,285)

Sodium-ion batteries are generally considered a promising alternative to lithium-ion batteries due to the abundance and low cost of sodium. However, their main limitation is the lack of an appropriate anode, since the usual graphite electrode used in lithium batteries is incompatible with the larger ionic radius of sodium. In this work, the theoretical behavior of pillared graphene as a possible anode is analyzed via computational simulations based on Density Functional Theory (DFT) using the FIREBALL program. The structural relaxation results reveal that staggered pillars are more stable than the aligned alternative. The adsorption energy of sodium is shown to be significantly higher than for graphite, with a maximum value of $-2.23$ eV, leading to an important energetic benefit. The diffusion analysis shows high mobility for sodium, with migration barriers comparable to those of lithium ions both in the flat regions of the structure and close to the nanotubes. The values are comparable to those of the standard graphite used in current batteries. Finally, the charge analysis confirms significant electronic transfer from both sodium and lithium to the lattice. These data indicate that pillared graphene can be a good candidate for the optimization of charge dynamics in sodium-ion batteries. Full article

Silicon is a promising anode for solid-state lithium batteries because of its high theoretical capacity, but large lithiation-induced volume changes and unstable electrode/electrolyte contact remain major challenges. Here, a contact-adaptive solid-state silicon (Si) architecture is developed by coupling an electrostatically assembled silicon/reduced graphene oxide (Si@rGO) nanosheet anode with a poly(ethylene oxide) (PEO)–lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)–ethylene carbonate (EC) electrolyte reinforced with 10 wt% Ta-doped Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO), hereafter denoted PEC-T. Trace EC promotes Li-salt solvation and PEO plasticization, while LLZTO suppresses polymer crystallization and reinforces ion transport. PEC-T shows a reduced melting temperature from 66.7 to 51.4 °C, improved tensile strength and elongation, an ionic conductivity of 3.0 × 10⁻⁴ S cm⁻¹ at 30 °C, a Li⁺ transference number of 0.57, and an oxidative stability limit of ~4.5 V. It also supports stable Li plating/stripping for 600 h at 0.1 mA cm⁻². Meanwhile, the rGO framework mitigates irreversible Si thickness evolution and preserves interfacial integrity. Consequently, Si@rGO/PEC-T/Li batteries deliver strong rate capability and maintain 1.8 Ah g⁻¹ after 250 cycles at 1 C, demonstrating a coupled chemo-mechanical strategy for stable solid-state silicon batteries. Full article

Cadmium contamination in fruits is a relevant food-safety concern because of its toxicity, environmental persistence, and potential transfer from agricultural soils to edible plant tissues. This study developed a screen-printed carbon electrode modified with graphene oxide and cysteamine (SPCE/GO–cysteamine) to determine Cd(II) by square-wave anodic stripping voltammetry (SWASV). Two surface-modification routes, GO-cysteamine and GO-rGO-cysteamine, and GO concentrations of 0.1, 0.2, and 0.5 mg mL⁻¹ were compared by cyclic voltammetry. The direct GO-cysteamine route at 0.2 mg mL⁻¹ produced the highest CV response among the tested conditions and was selected for Cd(II) determination. Raman spectroscopy FTIR spectroscopy and scanning electron microscopy were used to characterize the graphene-based materials employed during surface optimization. Cd(II) concentrations from 1 to 10 µg L⁻¹ were experimentally evaluated; with a calculated LOQ of 0.74 µg L⁻¹, the entire experimentally evaluated range of 1–10 µg L⁻¹, with a sensitivity of 11.30 µA (µg L⁻¹)⁻¹, R² = 0.9892, a limit of detection of 0.25 µg L⁻¹ and a limit of quantification of 0.74 µg L⁻¹. Fortified Kent mango and Hass avocado digestates also showed concentration-dependent responses, with R² values of 0.9799 and 0.9788, respectively, and relative standard deviations below 5%. These results demonstrate the feasibility of the SPCE/GO–cysteamine platform for Cd(II) determination in digested fruit matrices and support its further development as a portable screening approach for food-quality control. Full article

Biomass-derived materials are attracting increasing interest for photocatalytic photoreforming due to their ability to function as photocatalysts, co-catalysts, supports, templating agents, and green reducing agents. This review examines recent advances in the development of biomass-derived photocatalysts, including biochar, hydrochar, carbon quantum dots, graphene-like carbons, heteroatom-doped porous carbons, and biomass-derived graphitic carbon nitride, highlighting the relationships between synthesis strategies, structural properties, and photocatalytic performance. The multifunctional role of biomass-derived materials in enhancing semiconductor dispersion, interfacial charge transfer, and charge-carrier separation is also discussed. Finally, current challenges are identified, including the limited number of intrinsically active biomass-derived photocatalysts, the incomplete understanding of structure-activity relationships, and the lack of standardized evaluation protocols, providing perspectives for the rational design of efficient and scalable photocatalysts for solar-driven photoreforming. Full article

The persistent threat of chemical warfare agents (CWAs) drives the need for advanced detection and protective technologies. Polymers, with their tunable structures, ease of functionalization, and lightweight nature, have emerged as a versatile platform in this field. This review systematically summarizes recent progress in polymer-based materials for CWA sensing and protection, with emphasis on interaction mechanisms and structure–property relationships. In the realm of sensing, the working principles of polymer-based systems are rooted in electron transfer, hydrogen bonding, fluorescence quenching, and colorimetric response. Conductive polymers enable chemiresistive detection through charge transfer; hydrogen-bond acidic polymers provide selective recognition of organophosphorus agents; conjugated polymers exploit fluorescence quenching via the “molecular wire” effect; and polydiacetylenes offer visible color changes for naked-eye detection. Representative materials and their performance metrics are critically compared. For protection and decontamination, current polymer systems are designed around four synergistic mechanisms: barrier action, physical adsorption, filtration, and catalytic degradation. Barrier layers based on crosslinked networks or graphene/MOF composites suppress agent permeation while maintaining breathability. Porous polymers such as polymers of intrinsic microporosity (PIMs) and coordination polymers provide high-capacity adsorption through tailored surface functionality. Electrospun nanofiber membranes effectively filter aerosolized agents with low air resistance. Catalytic composites incorporating Zr-MOFs or single-atom catalysts enable hydrolysis of nerve agents and oxidation of blister agents under ambient conditions, with recent advances achieving self-buffering and solid-state operation. Despite significant advances, challenges remain in selectivity, environmental stability, and balancing protection with wearer comfort. Future directions point toward multifunctional systems that integrate detection, protection, and self-detoxification within wearable polymer platforms for next-generation chemical defense. Full article

Wearable and implantable biosensors are becoming small distributed biomedical systems rather than isolated transducers. Their practical performance depends on how the sensing interface, analog front end, power source, local computation, wireless link, packaging, and therapeutic output interact over time. The analysis focuses on that cross-layer problem, with emphasis on nanomaterial interfaces, energy autonomy, edge intelligence, and long-term reliability. Graphene, carbon nanotubes, MXenes, and transition-metal dichalcogenides are discussed across electrochemical, field-effect, impedance, optical, and radio-frequency transduction. Mechanical nanogenerators, biofuel cells, wireless power transfer, and hybrid storage are compared using the energy actually available after rectification and regulation rather than peak generator output alone. Quantitative re-plots illustrate non-monotonic carbon-nanotube loading in triboelectric layers and voltage-tunable few-layer-graphene microwave components. Edge AI is treated as part of the power and measurement architecture: local inference can reduce radio traffic and latency, but introduces model drift, uncertainty, and update requirements. The final sections connect biofouling, encapsulation, mechanical fatigue, calibration drift, wireless safety, and algorithm lifecycle to a common validation ladder for wearable, insertable, and implantable systems. Full article

Hydroxyapatite coatings containing graphene oxide and palladium were hydrothermally deposited on a β-type Ti30Zr5Mo alloy in order to establish how the organization of graphene oxide and the incorporation of palladium influence the structural, electrochemical, and biological performance of the coating system. Six compositions—hydroxyapatite, hydroxyapatite with 1 wt% palladium, hydroxyapatite with 2 wt% palladium, hydroxyapatite/graphene oxide, and the corresponding graphene oxide composites containing 1 and 2 wt% palladium—were compared using X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, potentiodynamic polarization, cell-density analysis with A7R5 cells, and bioluminescence imaging of Staphylococcus aureus Xen36. The apatite framework was retained in every composition, and Raman spectroscopy confirmed that the carbon phase derived from graphene oxide survived hydrothermal processing. X-ray photoelectron spectroscopy of the graphene oxide coating containing 2 wt% palladium revealed oxygenated carbon environments and predominantly oxidized, oxygen-coordinated palladium species rather than metallic palladium. Electrochemical behavior depended strongly on composition. The hydroxyapatite coating containing 2 wt% palladium showed the lowest corrosion current density, 1.46 ± 0.02 µA cm⁻² (0.0127 ± 0.0002 mm year⁻¹), and a mean total resistance of 15.73 ± 0.13 kΩ cm², close to that of the unmodified hydroxyapatite coating (1.95 ± 0.04 µA cm⁻²; 16.52 ± 0.40 kΩ cm²). The hydroxyapatite/graphene oxide coating showed the weakest barrier behavior, with a corrosion current density of 4.21 ± 0.07 µA cm⁻² (0.0366 ± 0.0006 mm year⁻¹) and a mean total resistance of only 8.50 ± 0.15 kΩ cm². Microscopic and electrochemical evidence indicated that the expected barrier effect of graphene oxide was lost because the graphene oxide-containing layer was structurally heterogeneous. This layer contained folded, sheet-like domains and pathways that remained accessible to the electrolyte, and restacking or aggregation of the sheets induced by calcium ions is proposed as a plausible origin of this morphology. Adding 1 wt% palladium partially restored coating coverage and raised the mean total resistance to 14.97 ± 0.20 kΩ cm² (2.15 ± 0.04 µA cm⁻²), whereas 2 wt% palladium lowered the interfacial charge-transfer resistance and reduced the mean total resistance to 11.73 ± 0.30 kΩ cm² (2.91 ± 0.06 µA cm⁻²), even though the outer part of the coating remained intact. All coatings supported higher short-term A7R5 cell densities than the uncoated substrate, and the highest value, 330.2% of the control, was obtained for the graphene oxide coating containing 2 wt% palladium. The same graphene-oxide/palladium coatings, however, produced considerably stronger bioluminescent responses from Staphylococcus aureus than the remaining compositions. Overall, the hydroxyapatite coating containing 2 wt% palladium offered the most balanced combination of electrochemical and biological performance. The results show that the behavior of these coatings is governed by the organization of graphene oxide, by the interfacial chemistry associated with palladium, by the pathways available to the electrolyte, and by buried charge-transfer processes, rather than by nominal additive content alone. Their architecture is characterized by folded sheet-like domains and accessible electrolyte pathways, with Ca²⁺-mediated restacking/aggregation proposed as a plausible origin. Incorporation of 1 wt% Pd partially restored coating coverage and increased the mean total resistance to 14.97 ± 0.20 kΩ cm², whereas increasing Pd to 2 wt% reduced the interfacial charge-transfer resistance and decreased the mean total resistance to 11.73 ± 0.30 kΩ cm² despite retention of the outer-coating barrier. All coatings supported higher short-term A7R5 cell densities than the uncoated substrate, with HA/GO-2Pd reaching 330.2% of the control. However, the GO/Pd coatings produced substantially higher Xen36 bioluminescent responses than the remaining compositions. Overall, HA-2Pd provided the most balanced electrochemical and biological performance, while the results demonstrate that the behavior of HA/GO/Pd coatings is governed by GO organization, Pd-associated interfacial chemistry, electrolyte-access pathways, and buried interfacial charge-transfer processes rather than nominal additive content alone. Full article

Nanofluid-cooled plate heat exchangers (PHEs) have strong potential to improve thermal system performance, but they often incur substantial pressure-drop penalties and are affected by uncertainties in the underlying correlations. I built a steady-state numerical model of a counter-current PHE in an ammonia heat-pump application to assess water-based mono- and hybrid nanofluids using an integrated thermohydraulic, exergetic, and operational–environmental perspective. The model was validated using my own experimental thermal conductivity measurements. While purely theoretical predictions suggest an 8.0% thermal improvement and a reduction in required plates (32 to 31) for 3 wt.% graphene, experiments show the graphene thermal conductivity is overpredicted by 35.10% because of nanoplatelet agglomeration. When the measured (realistic) conductivity is used, graphene’s heat-transfer benefit falls to only 1.2%, eliminating the plate-count advantage. As a result, dilute oxide nanofluids (1 wt.% TiO₂ and SiO₂) appear to be the most practical and sustainable choices, with Performance Evaluation Criterion (PEC) values of 0.994. In addition, the sensitivity study reveals a large 167–181% spread between the Pietrzak- and Kumar-type Nusselt-number correlations. Overall, the results show that physical constraints significantly limit the practical gains of concentrated carbon-based nanofluids, whereas low-loading metal oxides provide the most dependable route for sustainable PHE design. Full article

The corrosion degradation of ultra-thin copper foils remains a critical challenge for maintaining their long-term structural stability under aggressive electrochemical environments. In this work, small-size graphene (sGr) was incorporated into ultra-thin copper foils through a direct-current electrodeposition strategy to improve corrosion resistance. Compared with conventional graphene, the reduced graphene size facilitated a more uniform dispersion within the copper matrix and effectively regulated the surface morphology and crystallographic texture of the deposited copper foils. The resulting sGr/Cu composite foil exhibited reduced surface defects, enhanced (220) preferred orientation with a texture coefficient of 83.7%, and improved electrochemical corrosion resistance in 3.5 wt.% NaCl solution. Specifically, the sGr/Cu foil showed a more positive corrosion potential (−0.099 V), a lower corrosion current density (3.781 × 10⁻⁵ A·cm⁻²), and a higher charge transfer resistance (3789 Ω·cm²) compared with pure copper foil. The enhanced corrosion resistance was attributed to the synergistic effects of improved graphene dispersion, graphene-induced barrier effects, surface morphology optimization, and strengthened graphene/copper interfacial interactions. X-ray photoelectron spectroscopy analysis suggested the presence of Cu–O–C-related interfacial interactions, which may contribute to improved interfacial stability and corrosion protection. This work provides an effective strategy for designing corrosion-resistant ultra-thin copper foils through graphene size regulation and interface engineering. Full article

Track-etched polycarbonate membranes (PC-TeMs) offer a structurally supported and well-defined nanoporous architecture, but their intrinsically low ionic conductivity limits their direct application as solid-state electrolytes in supercapacitors. Here, we grafted poly(acrylic acid) (PAA) into the cylindrical nanopores of PC-TeMs via reversible addition–fragmentation chain-transfer (RAFT) polymerization, incorporating graphene oxide (GO) at 0–1 wt% to enhance ion transport and structural stability. Structural, spectroscopic, and morphological analyses indicated effective PAA grafting along the nanochannels and homogeneous GO dispersion within the membrane matrix. Electrochemical tests revealed a non-linear dependence of performance on GO content: an optimal GO content of 0.5 wt% with PAA grafting delivered the highest ionic conductivity (0.57 mS·cm⁻¹) and specific capacitance (1.14 F·g⁻¹ at 5 mV·s⁻¹). This corresponds to improvements of approximately ~6× and ~800× compared to the ungrafted GO-free membrane (0.09 mS·cm⁻¹ and 1.42 mF·g⁻¹), and ~3× and ~42× compared to the ungrafted GO-containing membrane (0.18 mS·cm⁻¹ and 26.96 mF·g⁻¹), respectively. In contrast, at a GO content of 1 wt%, pore blockage and a decline in performance were observed. These results demonstrate that finely tuned GO incorporation into RAFT-grafted PAA/PC-TeMs enables dimensionally stable solid-state electrolytes for high-performance solid-state supercapacitors. Full article

Earthen architectural heritage is highly vulnerable to moisture, erosion, salt activity, and progressive loss of cohesion, creating a need for consolidants that improve mechanical performance without obscuring the limitations of laboratory-to-field transfer. This study evaluates a graphene oxide–ESTEL (GO–ESTEL) nanocomposite as an exploratory consolidant for adobe under controlled laboratory conditions in Egypt and discusses, separately, how the results may inform future validation at Sudus, Saudi Arabia. Laboratory specimens and non-Sudus reference adobe fragments were characterized using polarized light microscopy (PLM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), computed tomography (CT), and uniaxial compressive strength testing. A fixed exploratory formulation based on a 3 wt.% aqueous GO dispersion combined with ESTEL was applied to the adobe specimens. The treated specimens showed denser microstructural features and improved particle bridging in SEM observations, while CT imaging provided complementary qualitative visualization of the internal structure of the treated adobe. Average maximum compressive load increased from 340.60 to 486.87 kgf, corresponding to a 42.94% increase; maximum displacement and strain at failure decreased by approximately 36.8%. These results demonstrate short-term laboratory strengthening of the tested adobe formulation, but they do not establish long-term durability, an optimum GO concentration, or direct compatibility with Sudus materials. The Sudus survey is therefore retained only as an application context and monitoring framework rather than evidence of field effectiveness. Site-specific mineralogical characterization, environmental monitoring, formulation optimization, accelerated ageing, and controlled pilot trials are required before any conservation application at Sudus or comparable heritage sites. Full article

Graphene quantum dots (GQDs) with distinct optical responses were prepared from pyrene using urea, melamine, and 2,4-pyridinedicarboxylic acid as nitrogen-containing regulators and were subsequently combined with ZIF-8 for visible-light-driven CO₂ reduction. FT-IR, Raman, XRD, optical spectroscopy, representative high-magnification transmission electron microscopy, and X-ray photoelectron spectroscopy (XPS) showed regulator-dependent structural, compositional, and optical differences. XPS detected surface nitrogen in all three GQD samples, with the highest N content in y-GQDs, while the relative N 1s component distributions differed across the series. At a nominal 4 wt% GQD addition, r-GQDs/ZIF-8 gave the highest observed mean CO and CH₄ formation rates of 23.51 ± 0.48 and 4.08 ± 0.15 μmol·g⁻¹·h⁻¹, respectively, corresponding to approximately 2.9- and 4.5-fold increases over pristine ZIF-8. This sample also showed the lowest fitted charge-transfer resistance, the highest mean photocurrent density, and the fastest qualitative time-resolved photoluminescence decay among the compared composites. Across three independent five-cycle tests, 83.78 ± 0.54% of the initial combined CO and CH₄ rate was retained. These results establish correlations among regulator identity, surface composition, optical relaxation, photoelectrochemical response, and catalytic activity, but do not determine a unique charge-transfer pathway or exclude contributions from surface basicity, CO₂ adsorption, and nominal-loading differences. Full article

This study investigates the microstructural, tribological, and corrosion properties of electrodeposited Zn-Co nanocomposite coatings reinforced with graphene and TiO₂ nanoparticles on Selective Laser-Melted (SLM) Ti6Al4V alloy. Systematic characterization using XRD, SEM, and Raman spectroscopy revealed that the incorporation of graphene and TiO₂ significantly refined the grain structure, resulting in a dense and defect-free surface morphology. Reciprocating wear tests demonstrated that the optimized hybrid coating (Zn-Co-GTi) exhibited superior tribological performance. Electrochemical impedance spectroscopy (EIS) tests conducted in simulated body fluid (SBF) at 37 °C demonstrated that the optimized hybrid coating (Zn-Co-GTi) also provided enhanced corrosion resistance. Specifically, the coefficient of friction decreased from 0.79 to 0.24, while the wear rate was reduced to 5.1 × 10⁻⁴ mm³/Nm. Electrochemical evaluations further confirmed a significant improvement in corrosion resistance, with the Zn-Co-GTi coating exhibiting the lowest corrosion current density (0.0059 μA cm⁻²) and the highest charge transfer resistance (Rct). However, increasing the reinforcement content beyond the optimum level resulted in partial nanoparticle agglomeration, leading to a slight deterioration in both tribological and corrosion performance. Overall, the optimized Zn-Co-Graphene-TiO₂ nanocomposite coating provides an effective and scalable surface engineering strategy for improving the durability and corrosion resistance of SLM-produced Ti6Al4V components for advanced engineering and biomedical applications. Full article

Laboratory experimentation is shaped by practical constraints, so computational frameworks built for offline settings do not transfer cleanly to an online laboratory routine. Two mismatches dominate. First, they assume on-demand access to high-fidelity facilities, whereas characterisation, fabrication, and testing are rarely economical one sample at a time. Second, experiments produce occasional catastrophic, non-Gaussian errors that a fixed noise model handles poorly. Here, we introduce a coupled scheduling-and-verification layer that wraps a multi-fidelity optimiser. A queue scheduler models per-session overheads and batches expensive measurements to amortise them; a Fidelity-Aware Verification Protocol repeats suspect observations and escalates unresolved ones to a higher fidelity. The two share the same cost-amortised queue, so a verification escalation is dispatched as just another queued sample, and anomaly handling reinforces batching rather than competing with it. On synthetic functions, the layer reduces overhead-incurring sessions by 28–43% and, under catastrophic outliers, cuts regret by 51–84%. On a real three-fidelity materials dataset, it improves cost-efficiency and robustness. In a live deployment on polydimethylsiloxane-mediated 2D material transfer, it reached Raman-confirmed monolayer graphene in 26 trials using only two Raman sessions, and those discovered parameters transferred another 2D material, monolayer molybdenum disulphide, on the first attempt. Full article

Alkaline water electrolysis (AWE) is a promising technology for sustainable hydrogen production, although its performance is limited by electrode overpotential, interfacial charge-transfer resistance, and limited electrochemically accessible surface area. In this study, a monolayer ternary carbon nanomaterial (CNM) composite comprising reduced graphene oxide (rGO), carbon nanotubes (CNTs), and Vulcan XC-72 was fabricated on stainless steel (SS) using a hybrid polyvinyl alcohol–polytetrafluoroethylene (PVA–PTFE) binder. Thermal treatment generated a porous conductive network that enhanced electrolyte accessibility and electron transport. Electrochemical characterization in 0.12 M NaOH showed that the CNM-modified electrode exhibited substantially higher current response and CV-derived double-layer capacitance (C_dl) of 62.61–78.51 mF/cm², compared with 3.43–3.74 mF/cm² for bare SS. Electrochemical fitting further showed markedly higher exchange-current density (i₀) parameters for the modified electrode, along with a reduced solution resistance (Rs) of ~2.1–2.2 Ω·cm² and a lower Rct. The oxyhydrogen (HHO) production rate reached 0.304 mL/min at 3.8 V, compared with 0.262 mL/min for bare SS at 4.0 V. Repeated HHO measurements showed ~2% variation (n = 3), indicating good reproducibility of the gas-production response. These results demonstrate that the rGO/CNT/XC-72 composite provides an effective and reproducible surface-engineering approach for enhancing electrochemical performance and HHO production in alkaline electrolysis systems. Full article