Search Results (237)

Oil spills represent a critical environmental challenge. The wastewater treatment with porous sorbents presents the advantage of higher uptake and recyclability. In this work, highly porous and low-density three-dimensional reduced graphene oxide aerogels were obtained by hydrothermal reduction followed by lyophilization. The porosity and reduction degree of the aerogels were controlled by the addition of reducing species, namely ethylenediamine, and hydrothermal conditions. The aerogels were characterized using scanning electron microscopy, Raman spectroscopy, and energy-dispersive X-ray analysis. The sorption measurements were performed with vegetable oils, namely canola and olive oil, at varying operating temperatures. The morphological analysis revealed a well-defined porosity gradient along the aerogel length, along with a functionalization gradient. The sorption performance is highly dependent on their combined action. The maximum gravimetric absorption capacity was about 122 g g⁻¹ at room temperature, increasing to 156 g g⁻¹ at 60 °C, with the absorption rate increasing from about 1 g g⁻¹ s⁻¹ to 15 g g⁻¹ s⁻¹ within 10 s. These results demonstrate that anisotropic gradient aerogels could be obtained by simple tailoring of the synthesis conditions, and such aerogels could benefit the sorption of oils with higher viscosities in terms of rate, pore filling and retention. Full article

The increasing demand for high-performance and multifunctional polymer materials has driven interest in improving the mechanical properties of polymer components produced through additive manufacturing. This study aims to systematically investigate and comparatively evaluate the effects of low-content nanofiller incorporation on the structural, thermal, and mechanical performance of PLA-based materials produced via fused deposition modeling (FDM), with a focus on identifying filler-dependent behavior under different loading conditions. In this study, polylactic acid (PLA) composites reinforced with 0.5 wt.% graphene (Gr) and 0.5 wt.% silver (Ag) nanoparticles, added separately, were produced using fused deposition modeling (FDM) and comparatively investigated. Each nanofiller was incorporated individually into PLA-based filaments, and standard test specimens were fabricated via 3D printing. Structural, thermal, and mechanical properties were evaluated using tensile, compressive, and three-point bending tests, along with SEM, EDS, XRD, FTIR, DSC, and TGA analyses. The results showed that pure PLA exhibited typical brittle behavior and a single-stage thermal degradation profile. The tensile strength of pure PLA was 41.93 MPa, and the flexural strength was 70.76 MPa. The addition of 0.5 wt.% graphene led to noticeable improvements, particularly in flexural properties, while only a minimal (almost negligible) increase was observed in tensile strength, with tensile strength increasing to 42.24 MPa (+0.74%) and flexural strength increasing to 110.78 MPa (+56.6%). In contrast, 0.5 wt.% Ag exhibited mixed and load-dependent mechanical behavior, with slight improvements in flexural strength but reductions in tensile and compressive properties, where tensile strength decreased to 22.13 MPa (−47.2%) while flexural strength increased to 112.06 MPa (+58.3%). Structural and thermal analyses indicated that both nanofillers did not significantly alter the PLA matrix chemically, while contributing to controlled changes in material properties primarily through physical interactions. The novelty of this work lies in the comparative evaluation of graphene and silver nanoparticle reinforcement at a fixed low loading level within FDM-processed PLA, combined with a comprehensive and correlated analysis of mechanical, structural, and thermal behavior on the same specimen sets, enabling a clearer understanding of filler-dependent performance mechanisms in additively manufactured nanocomposites. Overall, it was concluded that low-rate nanofiller additions, when properly dispersed, may lead to selective improvements in the performance of PLA-based composites depending on filler type and loading mode, and show potential for advanced engineering applications such as lightweight structural components, functional sensors, and additive-manufactured parts requiring tailored mechanical performance and multifunctionality. Full article

This study aims to develop sustainable conductive nanocomposites based on poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends reinforced with multi-walled carbon nanotubes (MWCNT) and graphene nanoplatelets (G), focusing on their multifunctional performance. The novelty lies in the production of hybrid nanocomposites based on PLA/PCL blends with MWCNT/G using conventional industrial processing techniques, enabling the development of eco-friendly nanocomposites with tailored electrical, mechanical, and electromagnetic properties. The nanocomposites were prepared by twin-screw extrusion followed by injection molding. Rheological, scanning electron microscopy (SEM), mechanical, thermal, thermomechanical, electrical conductivity, and electromagnetic shielding properties were systematically evaluated. From a rheological perspective, the PLA/PCL/MWCNT and PLA/PCL/MWCNT/G nanocomposites exhibited a plateau at low frequencies, associated with the formation of a percolated network. This was confirmed by the significant increase in electrical conductivity and electromagnetic shielding response. The morphology observed by SEM showed a refinement of the PCL phase in the PLA matrix with the incorporation of MWCNT. The PLA/PCL/MWCNT/G (4/2 parts per hundred resin, phr) nanocomposite showed a 309% increase in impact strength compared to neat PLA, while maintaining the heat deflection temperature (HDT). The elastic modulus exceeded 2300 MPa and accelerated the crystallization process by more than 15 °C compared to PLA, which makes it important to reduce injection molding time. Additionally, it exhibited the highest electrical conductivity level, around 6.79 × 10⁻⁵ S/cm, which resulted in improved electromagnetic shielding performance in the 8.2–18 GHz range, highlighting the synergistic effect between 1D and 2D fillers. The developed PLA/PCL/MWCNT and PLA/PCL/MWCNT/G nanocomposites demonstrate potential for antistatic applications, combining sustainability with multifunctional performance and industrial scalability. Full article

The performance of CdS-based photocatalysts can be enhanced by incorporating graphene co-catalysts in close contact with the photoactive phase. However, assembling these distinct components remains a bottleneck, as their differing chemical natures often limit effective interfacial interaction when they are synthesized separately. In this work, we present an adaptable PEI-mediated interfacial assembly strategy for promoting the nucleation and growth of nanocrystalline CdS phases on different graphene-based supports within a common, yet support-adapted, approach. Specifically, by functionalizing the surface of various graphene materials with hyperbranched polyethyleneimine (PEI) as a multifunctional interlayer mediator, we achieve controlled CdS formation. This strategy provides a common chemical framework for producing CdS nanocrystals closely associated with the carbon surface, regardless of the substrate. Diverse materials, including low-defect graphene sheets (G-Sheets), graphene nanoplatelets (GNPs), and graphene oxide (GO), were integrated using tailored architectures: noncovalent PDI-anchoring for GNP and G-Sheets and direct covalent functionalization for GO. In the latter case, PEI acts simultaneously as a mild reducing agent, yielding a covalently grafted reduced graphene oxide hybrid (rGO-PEI). XRD patterns confirm comparable CdS crystallinity across all hybrids, while photocatalytic hydrogen evolution measurements reveal a strong dependence on the nature of the graphene support. rGO-PEI@CdS exhibits the highest hydrogen evolution rate (0.44 mmol g⁻¹ h⁻¹) without any noble-metal cocatalyst, highlighting the role of surface defects and oxygen functionalities in interfacial charge transfer. Thermal treatment of rGO-PEI@CdS enhances activity (average 1.20 mmol g⁻¹ h⁻¹) but leads to partial deactivation over time. Overall, this study provides an adaptable PEI-mediated framework for integrating diverse graphene-type materials as co-catalysts within CdS-based photocatalytic materials and investigates structure–function relationships in graphene@CdS systems. Full article

Additive manufacturing by stereolithography (SLA) is widely used for fabricating complex polymeric parts. However, photocurable resins typically exhibit brittle behavior. In this context, the incorporation of nanofillers has emerged as a strategy to tailor mechanical performance, although challenges related to dispersion and processability remain. This work investigates the co-incorporation of graphene oxide (GO) and kraft lignin, including a low-molecular-weight fraction (FKL), into acrylate-based photocurable resins processed by SLA. Pre-curing dispersion and viscosity were evaluated by optical microscopy and rotational rheometry. The mechanical, viscoelastic, and fracture behavior of the printed nanocomposites was assessed by tensile testing, dynamic mechanical analysis, and scanning electron microscopy. The results show that all formulations exhibited viscosities suitable for SLA processing. The presence of FKL promoted improved GO dispersion and more stable rheological behavior compared with unfractionated lignin. At low lignin contents, a pronounced synergistic effect with GO led to enhanced tensile strength, whereas increasing lignin content reduced stiffness and glass transition temperature while significantly increasing elongation at break, particularly for FKL-based systems. Overall, these findings demonstrate that lignin fractionation is an effective strategy to modulate dispersion, mechanical response, and toughness in GO-containing photocurable resins. Full article

Geopolymers, alkali-activated aluminosilicate materials, have gained increasing attention as sustainable adsorbents for wastewater treatment due to their low-temperature synthesis, cost-effectiveness, and ease of shaping into mechanically robust structures. Their intrinsic negatively charged framework promotes the adsorption of cationic species; however, pristine geopolymers typically exhibit moderate performance, with adsorption capacities generally below ~70 mg g⁻¹ for dyes such as methylene blue (MB) and in the range of 20–100 mg g⁻¹ for divalent metal ions. To overcome these limitations, different strategies have been developed to tailor their pore structure and surface chemistry. In particular, foaming approaches enable the production of highly porous materials with tunable pore architecture, improving mass transfer and accessibility of active sites. Moreover, functionalization with carbon-based materials (e.g., activated carbon, graphene derivatives, biochar) or zeolitic phases significantly enhances adsorption performance, with reported capacities exceeding 500 mg g⁻¹ for Pb²⁺ and up to 450 mg g⁻¹ for organic dyes in optimized systems. This review provides a comprehensive overview of recent advances in geopolymer synthesis, pore engineering, and functionalization strategies, highlighting the relationships between composition, structure, and adsorption performance. Particular attention is devoted to the comparison between carbon-based and zeolitic modifications, as well as to the role of material shaping in enabling practical applications. Overall, the combination of tunable porosity, chemical versatility, and structural integrity positions functionalized geopolymers as promising candidates for the development of scalable and multifunctional adsorbents for wastewater remediation. Full article

Graphene-based nanomaterials (GBNs) have emerged as promising candidates for diverse biomedical applications, but their clinical translation has been hindered by inherent cytotoxicity. We synthesized three distinct cerium-containing graphene nanocomposites using a single-step, in situ electrochemical exfoliation process and investigated their structure–activity relationships in normal dermal fibroblasts (BJ) and hepatocarcinoma cells (HepG2). The properties of the resulting nanocomposites, including their morphology, cerium loading, and the surface redox state (Ce³⁺/Ce⁴⁺ ratio) were directly dictated by the employed synthesis parameters, such as the cerium salt precursor and its concentration. These distinct materials induced differential cellular responses that ranged from preferential cytotoxicity in HepG2 cells to a significant cytostimulatory effect and increased ATP levels in BJ fibroblasts, particularly in EXF3-treated cells. Our findings indicate that by employing the in situ electrochemical exfoliation method, the hybrid graphene compounds might be further tailored for specific purposes, moving the narrative beyond the mere functionalization of the graphene in order to achieve biocompatibility. Full article

Surface-enhanced Raman spectroscopy (SERS) has evolved from a fundamental optical phenomenon to a powerful, molecule-specific analytical technique capable of detecting ultra-trace-level species across biomedicine, catalysis, environmental monitoring, and national security applications. In this review, we summarize recent advances in SERS probe design and fabrication along three major directions: (i) engineering plasmonic hotspots with enhanced field confinement to achieve stronger and more uniform signals; (ii) analyte-directed strategies that precisely position and retain target molecules via tailored surface chemistries, nanoscale confinement, and on-surface reactions for single hotspot SERS; and (iii) hybrid architectures integrating plasmonic metals with functional materials, including high entropy materials, semiconductors, and graphene and other 2D materials, to synergistically couple electromagnetic and chemical enhancement mechanisms. Despite significant progress, key challenges remain for practical applications outside laboratories, including substrate reproducibility and stability, diverse analyte compatibility, unknown molecule identification and standardized quantitative performance in complex environments. We highlight emerging solutions, such as large-area nanomanufacturing for controlled nanoscale gaps, high-resolution Raman mapping for spatial–temporal characterization, density-functional-theory-guided molecular interpretation, and machine-learning-enabled spectral analysis. Advances in foundational AI models and data-driven discovery are positioning SERS to become an increasingly versatile platform, from decoding unknown molecular structures to analyzing complicated multi-component systems for environmental, biomedical, and national security applications with high sensitivity and selectivity. Full article

While aluminum (Al) continues to be a cornerstone for microelectronic interconnect technologies, its chronic tendency toward hillock growth and thermal instability necessitates a transition toward high-performance nanostructured material architectures. This research tackles these reliability bottlenecks by achieving a molecular-level integration of graphene nanoplatelets (GNPs) within Al matrices, a strategy designed to fortify structural resilience. Adopting a green chemistry approach, we synthesized Al-GNP (0.25 vol.%) composite thin films through Pulsed Laser Deposition (PLD) using precursors derived from recycled aluminum. A major obstacle—the formation of the deleterious Al₄C₃ intermetallic phase—was effectively suppressed by ensuring a homogeneous supramolecular dispersion via a specialized dual protocol (ultrasonication and magnetic stirring) during the powder metallurgy stage. Comprehensive physicochemical characterization, utilizing HR-TEM and XRD, verified the structural integrity of the multilayer GNPs (d-spacing = 4.6 Å). Furthermore, surface metrology analysis uncovered a radical shift in growth kinetics: whereas pure Al grew via a “spiky” Volmer-Weber mechanism (Sku = 31.17), the carbon-based inclusion stabilized the film evolution, tempering the kurtosis to Sku = 7.74. Analytical cross-sectional EDS confirmed both stoichiometric fidelity and the achievement of void-free Si/Pt/Al-GNP interfaces. These outcomes prove that a precise nanoscale tailoring of surface morphology via carbonaceous reinforcements significantly bolsters microstructural stamina. Consequently, these PLD-deposited composites emerge as sustainable, cutting-edge candidates for the next generation of microelectronic packaging and interfacial chemistry applications. Full article

Three types of graphene–single crystal titanium dioxide composite (GR–TiO₂SCs) were prepared using the hydrothermal method, employing TiF₄ and graphite as raw materials with hydrofluoric acid serving as the morphology-directing agent. The phase composition and morphological features of the resultant composites were systematically characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray diffraction. These complementary characterization results clearly demonstrate that graphene and TiO₂ single crystals have been successfully hybridized to form a well-defined heterostructure, rather than a simple physical mixture. Photocatalytic performances were evaluated by monitoring the photodegradation behaviors of methylene blue, rhodamine B, and methyl orange solutions under simulated light irradiation, with real-time concentration variations recorded by UV–visible absorption spectroscopy. The composite sample in which TiO₂SCs were in situ grown and uniformly anchored onto graphene oxide substrates effectively suppressed the self-stacking and agglomeration of individual crystallites, thus delivering the best photocatalytic response. Increased exposure of the active catalytic interfaces of TiO₂SCs was found to play a key role in elevating the overall photocatalytic activity. The hierarchical assembly protocol developed in this work provides a feasible pathway for the rational design of functional composites with controllable microstructures and tailored properties, which can be further extended to the development of advanced sensing materials. Full article

Aluminum alloy (AA5083) is widely used in the aerospace and marine industries. However, its use is sometimes limited by its low surface hardness, wear resistance, and thermal stability. The microstructural, mechanical, tribological, and dynamic behavior of AA5083 matrix composites incorporated with mono-reinforcements (hexagonal boron nitride (hBN), graphene (G), and carbon nanotubes (CNTs)) and hybrid reinforcements (hBN+CNTs, G+hBN, and CNTs+G) by friction stir processing (FSP) is thoroughly investigated. Microstructural examination demonstrated that extensive dynamic recrystallization was induced by FSP, reducing the base-metal grains (about 215 μm) to very small sizes. The hybrid hBN+CNT composite had the smallest grain size (about 4.5 μm), the mono-CNT composite had the highest microhardness (~60 HV), whereas the hybrid CNTs+G composite had the highest ultimate compressive strength (~350 MPa). This enhancement was attributed to the formation of a 3D network within the hybrid composite, which hindered graphene agglomeration and restacking. Tribological tests revealed that hybridization greatly reduced wear; in particular, hBN-containing hybrids (hBN+CNTs and hBN+G) had the lowest wear rates (~0.037 mg/bar.min), owing to hBN’s solid-lubrication effect. Moreover, dynamic mechanical analysis and free-vibration testing showed the tunability of vibrational characteristics; the mono-CNT composite had the greatest structural stiffness (storage modulus ~72.75 GPa), whereas the G+CNTs hybrid had the best damping ratio (damping ratio ~4.82%). These results demonstrate that hybrid nanoreinforcements can tailor the multifunctional characteristics of AA5083 composites. Full article

Diamond-like carbon (DLC) coatings are widely used as protective and self-lubricating surfaces in metal–metal contacts. Their frictional behavior is governed by the formation and evolution of carbon-rich transfer layers (TLs), which can be tailored through functionalization with carbon nanomaterials. Recent studies have shown that graphene sheets (GSs) and nanodiamonds (NDs) act synergistically to achieve ultra-low friction in microrough (~0.2 μm) metal–DLC contacts under dry N₂ at a 1 N load. Here, we probe how this lubrication mechanism evolves with increasing load from 1 to 10 N—corresponding to local contact pressures up to ~11–16 GPa—respectively, in dry N₂ and humid air conditions. Ball-on-disk experiments are performed on an industrial hydrogenated DLC coating sliding against stainless-steel. In dry N₂, GS–ND functionalization yields a low and stable coefficient of friction across the entire load range, reaching a minimum of about 0.05. In humid air, higher friction levels are observed across all loads (CoF ~0.10–0.15), accompanied by oxidation-driven modifications of both wear debris and the counterface contact region, with oxygen content increasing by more than a factor of three compared to dry N₂. Detailed microscopy and spectroscopy analyses indicate that enhanced lubricity in dry N₂ arises from TLs incorporating GSs, NDs, and nanoscroll-like structures, whereas humid air promotes interfacial amorphization and oxidation, leading to load-insensitive friction and boundary lubrication effects through physisorbed water molecules. Full article

Graphene and its derivatives are widely recognized as effective reinforcements due to their unique mechanical, thermal and lubrication performance. Incorporation of these reinforcements into polyamide-imide (PAI) coating matrix has shown significant potential for improving the tribological performance. Here, the mechanisms underlying the tribological improvement enabled by graphene oxide (GO) are investigated via frictional experiments and molecular dynamics simulations. It was found that the coefficient of friction (COF) of PAI coating is reduced upon the addition of GO over the range of 100–400 MPa and 20–100 mm/s, with a maximum reduction of ~25% achieved at 200 MPa and 60 mm/s. Simulations reveal that the friction reduction arises from strong adhesion interactions between the embedded GO sheets and PAI molecular chains, which inhibit the shear-induced mobility of the chains during the friction process. This mechanism enables a further reduction in the COF of the GO/PAI composite coating by increasing the interfacial adhesion through the tailored modulations of surface morphology and chemistry of the GO sheets. These findings pave the way for advancing the rational design and application of graphene-based composite coatings with highly improved tribological performance. Full article

The transformation of waste plastics into hydrogen and functional carbon (C) materials represents a promising pathway for achieving both resource recycling and the production of value-added products. Owing to their tunable physicochemical properties, plastic-derived carbons have attracted significant attention in electrochemical energy storage applications. Various C nanostructures, including graphene, porous C, hard C, and C nanotubes (CNTs), can be generated from discarded plastics through thermochemical processes. The electrochemical performance of these materials is closely governed by their structural characteristics, such as pore architecture, specific surface area, heteroatom doping, surface functionalities, and dimensional morphology. This review aims to provide a comprehensive and systematic overview of the conversion of waste plastics into functional C nanomaterials via thermochemical routes, particularly catalytic pyrolysis and carbonization. The resulting C nanostructures are systematically categorized based on their dimensional architectures (0D, 1D, 2D, and 3D) and comparatively analyzed in terms of their structural features and electrochemical performance. Emphasis is placed on the transformation of diverse plastic feedstocks into high-value C materials with tailored dimensional architectures, including graphene, CNTs, C nanospheres, C nanosheets, porous carbons, and their composites. Furthermore, recent progress and critical challenges in utilizing these materials for electrochemical energy storage systems, such as supercapacitors and rechargeable batteries (Li-ion, Na-ion, K-ion, Li-S, and Zn-air), are discussed. Distinct from previous reports, this review highlights the correlation between thermochemical processing strategies, resulting structural features, and electrochemical performance, providing new insights into the rational design of high-performance C materials. These findings are expected to facilitate the advancement of sustainable energy storage technologies while contributing to effective plastic waste valorization. Full article

Graphene incorporation into polymer fibers offers a strategy to tune nanoscale morphology while preserving mechanical conformity for flexible composite applications. Graphene-based dopants can enable modulation of polymer fiber structure; however, the relationship between graphene incorporation, fiber morphology, and mechanical flexibility must be evaluated. This study investigates the integration of graphene oxide (GO) and reduced graphene oxide (RGO) into fibrous materials to tailor the structural and surface characteristics by fabricating GO- and RGO-enhanced poly(vinylidene fluoride) (PVDF) fibers via a wet-spinning process and examining the tunability of their morphology and its influence on mechanical properties. The effect of graphene doping and reduction state on fiber architecture is explored using scanning electron microscopy (SEM), atomic force microscopy (AFM), and Brunauer–Emmett–Teller (BET) surface area analysis. Fourier transform infrared (FTIR) and Raman spectroscopy analyses confirmed the incorporation and reduction of graphene derivatives within the PVDF matrix while revealing corresponding changes in chemical functionality and the piezoelectric phase of PVDF. Mechanical flexibility is assessed through tensile testing, revealing increased stiffness with graphene addition, although maintaining sufficient structural integrity for wearable applications. These results collectively demonstrate that graphene doping provides a facile route to engineer composite fibers, enabling a balance between morphological complexity and mechanical compliancy, while establishing graphene-enhanced fibers as promising materials for flexible sensing systems and wearable smart textiles. Full article