Search Results (51)

Miniaturized spatial electric field sensors often exhibit insufficient front-end charge coupling because of their limited sensing area. To address this material-level bottleneck, KH550-functionalized graphene composite films were developed as candidate electrode materials for spatial electric-field sensing. Single-layer and multilayer graphene powders were modified with the silane coupling agent KH550 and dispersed in a waterborne polyurethane/PVP matrix to fabricate composite films. The sensing mechanism was analyzed from the Maxwell–Wagner–Sillars interfacial polarization and electrode-equivalent capacitance perspectives. The modified materials were characterized by SEM, EDS, Raman spectroscopy, FTIR spectroscopy, low-frequency dielectric measurements, and broadband high-frequency impedance measurements. KH550 functionalization introduced Si- and N-containing surface species and increased disorder or sp³-related structural features while retaining the layered graphene structure. The film formulation selected through qualitative visual screening contained 0.16 g of graphene, 10 mL of waterborne polyurethane, and 0.05 g of PVP. Under AC excitation, the relative permittivity of the composite film containing KH550-functionalized multilayer graphene was approximately 18% higher than that of its unmodified counterpart. Broadband measurements showed material-dependent changes in the reflection and impedance responses of the electrode–fixture configurations. The modified multilayer-graphene electrode exhibited a different distribution of reflection minima, resistance maxima, and capacitive–inductive transitions from the unmodified and copper electrodes. Because the measured response includes contributions from the coating, substrate, fixture, and parasitic elements, these results are interpreted as comparative system-level responses. These results indicate that interfacial engineering of graphene composite films can enhance electrode-level dielectric response and charge-coupling capability, providing a material basis for non-contact electric field sensing electrodes. Full article

The work explores the effect of modifying thin ZnO and ZnO:V sol–gel films with graphene oxide (GO) dispersions on their structural and photocatalytic properties. The study has, for the first time, detected the effect of selective phase separation in sols, characterized by the separate crystallization of zinc and vanadium oxides upon adding GO dispersion into a mixed sol. Increasing the GO concentration in ZnO-VO₂ precursor sols improves the crystallinity of the material; films of the same composition without added GO are X-ray amorphous. Conversely, adding GO to unmodified ZnO sols causes a reduction in the crystallite size of the films, which increases with higher GO content. Notably, their photocatalytic activity varies non-monotonically: at 10 wt.% GO, it is minimal, while a further increase in the GO concentration leads to its improvement. An increase in the GO concentration in ZnO:V films causes a monotonically enhanced efficiency of photocatalysis. This may be related to the improved crystallinity and the formation of a percolation cluster from reduced graphene oxide. Full article

Carbon/inorganic hybrid composites have evolved from filler-reinforced materials into design platforms for coupled electromagnetic, thermal, sensing, environmental, protective and energy-related functions. Their distinctive value lies in the possibility of combining a conductive, polarizable or porous carbon phase with an inorganic phase that contributes dielectric, magnetic, catalytic, ionic, thermally conductive or barrier behavior. This review examines carbon/inorganic hybrid multifunctional composites from the viewpoint of structure–property relationships, with emphasis on interfacial design, percolation, anisotropy, hierarchical architecture, processing and metrology. Selected graphitic composite studies are discussed as case studies for broadband dielectric spectroscopy, microwave shielding, high-frequency contact metrology, thermal diffusivity analysis and impedance-monitored graphene filters; these case studies are integrated with the broader international literature on CNT and graphene polymer composites, MXene films and foams, graphene/metal oxide photocatalysts, boron nitride/carbon thermal networks, biochar–graphene adsorbents, smart coatings, sensors, supercapacitors and water remediation systems. The central argument is that credible multifunctionality requires more than measuring several properties on the same material. It requires simultaneous or service-relevant co-optimization under constraints of thickness, density, processability, aging, humidity, corrosive media, regeneration, toxicity, economic feasibility and scalable fabrication. The review concludes with design rules and reporting recommendations intended to help move the field from impressive property demonstrations toward application-ready hybrid material systems. Full article

Heavy oil and extra-heavy oil represent mobility-limited petroleum resources because supramolecular associations of asphaltenes and resins, together with strong interfacial resistance, generate extremely high apparent viscosity. In recent years, nanotechnology has emerged as a promising approach for viscosity management and enhanced oil recovery (EOR). This review critically examines recent advances in nano-assisted viscosity reduction from a reservoir-operational perspective and organizes the literature into two field-relevant categories: metal-based and non-metal nano-systems. Metal-based nanoparticles (NPs) mainly promote catalytic aquathermolysis and related bond-cleavage and hydrogen-transfer reactions under hydrothermal conditions, enabling partial upgrading and persistent viscosity reduction during thermal recovery. In contrast, non-metal nano-systems—particularly silica- and graphene-oxide-derived materials—primarily operate through interfacial and structural regulation mechanisms at low or moderate temperatures. These effects include wettability alteration, interfacial-film stabilization, modification of asphaltene aggregation behavior, and the formation of dispersed-flow regimes such as Pickering-type emulsions that reduce apparent flow resistance in multiphase systems. Beyond summarizing nanomaterial types, this review emphasizes reservoir-scale considerations governing field applicability, including brine stability, NPs transport and retention in porous media, and formulation compatibility. Comparative analysis highlights the distinct operational windows of thermal catalytic nano-systems and cold-production nano-systems, providing a reservoir-oriented framework for designing nano-assisted viscosity-reduction technologies. Full article

In this work, the deposition of graphene coatings on substrates of an ELI grade Ti-6Al-4V alloy was carried out using the Plasma Enhanced Chemical Vapor Deposition (PECVD) technique. The purpose of this study was to improve the surface properties of the material. The characterization of the material was carried out by non-destructive techniques, such as Raman Spectroscopy and Thermoelectric Potential. A preliminary characterization of Ti substrates was carried out by Raman spectroscopy. Conversely, thermoelectric potential tests were conducted using three distinct tip systems and four different temperature gradients. Lastly, some surface roughness measurements were conducted on all samples, both coated and uncoated. Graphene micro-structured coatings were obtained using a plasma-activated mixture of hydrogen and methane gases with an equimolar feed ratio (1:1 H₂:CH₄) at a temperature of 850 °C and a plasma exposure of 150 Watts and duration of 15 min. Raman spectra verified the presence of uniform micrometric graphene on the surface of Ti substrates. Graphene-coated Ti-6Al-4V ELI substrates exhibited Seebeck coefficient values indicating metallic-like behavior and suitability for thermoelectric sensing. In the eddy current analyses, it was found that low frequencies provided the highest sensitivity for differentiating between samples. An inverse relationship was identified between substrate thickness and phase angle, and a direct relationship with calculated electrical conductivity was also identified. This direct relation is attributed to penetration depth and interactions due to the chemical nature of the substrate and coating. Despite a slight increase in surface roughness after graphene deposition, values remained comparable to the base alloy, preserving compatibility for biomedical integration. Thermoelectric potential measurements revealed enhanced sensitivity to surface morphology and interfacial effects when high-sensitivity probe configurations were employed. These results support potential applications in implantable or wearable temperature sensors, energy harvesting devices, and smart biomedical interfaces. The thickness of the graphene coating was also characterized by SEM, which showed that the films deposited by PECVD are about 1 micron thick. Full article

Flexible dielectric composite materials capable of converting power frequency electric fields into measurable electrical signals are of great significance in the field of non-contact electric field sensing in power systems. In this paper, graphene/nitride heterojunction powders were prepared using three representative nitrides (AlN, BN, and Si₃N₄) and embedded in polydimethylsiloxane (PDMS) to prepare flexible composite films with a fixed filler content of 5.0 wt%. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirmed the successful formation of the heterojunctions. The results showed that the nitride-related elements (Al, Si and N) were spatially correlated with the graphene-rich regions, thus providing abundant interfacial contact sites. Dielectric spectroscopy (50 Hz–50 kHz) showed that all samples exhibited typical dispersive behavior, with the real part of the dielectric constant decreasing monotonically with increasing frequency, and the loss tangent also decreasing smoothly. Under a 50 Hz parallel-plate electric field, the normalized induced voltage amplitude (PDMS = 1) increases to 1.070 (≈7.0%) for G/PDMS, and further to 1.0723–1.07447 (≈7.23–7.45%) for AlN–G/PDMS, BN–G/PDMS, and Si₃N₄-G/PDMS. DFT calculations confirm that the graphene/nitride interface has a stable structure with negative binding energies (−2.241, −1.773, and −3.062 eV for AlN–G, BN–G, and Si₃N₄–G, respectively). Significant charge redistribution and Mulliken charge transfer (0.0538, 0.2047, and 0.0244 eV, respectively) are present at the interface, accompanied by Fermi level density of states modulation and a small bandgap opening (~0.101 eV) in BN–G. These results collectively support the interfacial polarization-driven mechanism and provide a comparative basis for selecting nitride components in graphene-based heterojunction fillers in flexible dielectric electric field-sensing layers. Full article

Force-field Monte Carlo and Molecular Dynamics simulations are used to compare wetting behaviors of model carbon sheets mimicking neat graphene, its saturated derivative, graphane, and related planar allotropes penta-graphene, γ-graphyne, and ψ-graphene in contact with aqueous droplets or an aqueous film confined between parallel carbon sheets. Atomistic and area-integrated surface/water potentials are found to be essentially equivalent in capturing moderate differences between the wetting free energies of tested substrates. Despite notable differences in mechanical and electric properties of distinct allotropes, the predicted allotrope/water contact angles span a narrow window of weakly hydrophilic values. Contact angles in the range of 80 ± 10° indicate modest hydration repulsion incapable of competing with van der Waals attraction between carbon particles. Poor dispersibility in neat water is hence a common feature of studied materials. Full article

In the present work, we provide the development results of highly efficient conductive biopolymer composite films with potential use as piezoresistive sensors. Natural isotactic biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was selected as the primary biopolymer material. To reduce the crystallinity and improve the processability of PHBV, the synthetic atactic (R,S)poly-3-hydroxybutyrate ((R,S)-PHB) polyester was blended with the semicrystalline PHBV biopolyester. Graphene nanomaterials with different structures, comprising crude multi-walled carbon nanotubes (MWCNTs), oxidatively functionalized multi-walled carbon nanotubes (ox-MWCNTs) and graphene nanoplatelets (GNPs), were proposed as electroactive fillers. The preparation of the composites was based on a simplified solvent casting method and the conductive graphene fillers were dispersed into the biopolyester matrix without any further routines. As a result of the optimization, a PHBV/((R,S)-PHB) mass ratio of 70:30 was found to be the most promising composition to obtain composite films with the expected mechanical characteristics. The influence of graphene filler structure on the degree of crystallinity, viscoelastic, electrical, and piezoresistive properties obtained for of the composites was determined. The lowest PHBV/PHB matrix crystallinities of 37% (DSC) and 39% (XRD) were recorded for the composite with 1% ox-MWCNTs and 1% GNPs. The most promising piezoresistive responses were noted for composites filled simultaneously with 1% GNPs and 1% ox-MWCNTs or MWCNTs. However, a 1.5% deformation and recovery did not affect the initial conductivity of the PHBV/(R,S)-PHB +1%MWCNTs+1%GNP system (9 × 10⁻⁵ S/cm), while for the system with oxidized carbon nanotubes, the resistance increases by approximately 0.2% in relation to the initial value (8 × 10⁻⁶ S/cm). Full article

Graphene oxide (GO) and reduced graphene oxide (rGO) have emerged as robust materials in the development of SAs for erbium-doped fiber lasers (EDFLs). Their exceptional optical properties, such as broadband absorption and fast recovery times, make them ideal candidates for achieving ultrashort pulse operation in EDFLs. With its higher oxygen content, GO offers greater nonlinearity and a tunable absorption spectrum, while rGO, yielded through chemical reduction, exhibits enhanced electrical conductivity and higher saturable absorption. These properties facilitate the generation of ultrashort pulses in EDFLs, which are highly desired for various medical imaging, telecommunications, and material processing applications. This review paper comprehensively analyzes the advancements in GO and rGO SAs in the context of EDFLs for mode-locking and Q-switching applications. The performance of EDFLs utilizing GO and rGO SAs is critically evaluated, focusing on key parameters, such as modulation depth, pulse duration, repetition rate, average power, pulse energy, peak power, and signal-to-noise ratio. Additionally, this review delves into the various synthesis methods of GO and rGO thin film, highlighting their impact on the optical properties and performance of SAs. The discussion on techniques to integrate the SAs into laser cavities includes direct deposition of nanoparticles/thin-film-based SAs, tapered-fiber-based SAs, and D-shaped SAs. Furthermore, the paper explores the challenges encountered during the fabrication of ideal GO and rGO SAs, with issues related to uniformity, stability, and tunability, along with proposed solutions to address these challenges. The insights provided offer valuable guidance for future research aimed at enhancing the performance of EDFLs using GO/rGO SAs. Full article

This paper investigates an in situ, non-destructive detection sensor based on flexible wearable technology that can reflect the intensity of plant transpiration. The sensor integrates four components: a flexible substrate, a humidity-sensing element, a temperature-sensing element, and a self-adhesive film. It is capable of accurately and continuously measuring the temperature, humidity, and vapor pressure deficit (VPD) on the leaf surface, thus providing information on plant transpiration. We combined the humidity-sensitive material graphene oxide (GO) with a PDMS-GO-SDS flexible substrate as the humidity-sensing element of the sensor. This element exhibits high sensitivity, fast response, and excellent biocompatibility with plant interfaces. The humidity monitoring sensitivity of the sensor reaches 4456 pF/% RH, while the temperature sensing element has a sensitivity of approximately 3.93 Ω/°C. Additionally, tracking tests were conducted on tomato plants in a natural environment, and the experimental results were consistent with related research findings. This sensor can be used to monitor plant growth during agricultural production and facilitate precise crop management, helping to advance smart agriculture in the Internet of Things (IoT) for plants. Full article

Multiphase nanomaterials are of increasing importance in material science. Providing reliable and statistically meaningful information on their average nanostructure is essential for synthesis control and applications. In this paper, we propose a novel procedure that simplifies and makes more effective the electron powder diffraction-based Rietveld analysis of nanomaterials. Our single step in-TEM method allows to obtain the instrumental broadening function of the TEM directly from a single measurement without the need for an additional X-ray diffraction measurement. Using a multilayer graphene calibration standard and applying properly controlled acquisition conditions on a spherical aberration-corrected microscope, we achieved the instrumental broadening of ±0.01 Å in terms of interplanar spacing. The shape of the diffraction peaks is modeled as a function of the scattering angle using the Caglioti relation, and the obtained parameters for instrumental broadening can be directly applied in the Rietveld analysis of electron diffraction data of the analyzed specimen. During peak shape analysis, the instrumental broadening parameters of the TEM are controlled separately from nanostructure-related peak broadening effects, which contribute to the higher reliability of nanostructure information extracted from electron diffraction patterns. The potential of the proposed procedure is demonstrated through the Rietveld analysis of hematite nanopowder and two-component Cu-Ni nanocrystalline thin film specimens. Full article

Nanocomposites based on ferromagnetic nickel nanoparticles and graphene-related materials are actively used in various practical applications such as catalysis, sensors, sorption, etc. Therefore, maintaining their dispersity and homogeneity during deposition onto the reduced graphene oxide substrate surface is of crucial importance to provide the required product characteristics. This paper demonstrates a new, reproducible method for preparing a tailored composite based on nickel nanoparticles on the reduced graphene oxide surface using supercritical isopropanol treatment. It has been shown that when a graphene oxide film with previously incorporated Ni²⁺ salt is treated with isopropanol at supercritical conditions, nickel (2+) is reduced to Ni (0), with simultaneous deoxygenation of the graphene oxide substrate. The resulting composite is a solid film exhibiting magnetic properties. XRD, FTIR, Raman, TEM, and HRTEM methods were used to study all the obtained materials. It was shown that nickel nanoparticles on the surface of the reduced graphene oxide had an average diameter of 27 nm and were gradually distributed on the surface of reduced graphene oxide sheets. The data obtained allowed us to conduct a reconnaissance discussion of the mechanism of composite fabrication in supercritical isopropanol. Full article

The synergistic combination of hybrid perovskites with graphene-related materials is leading to optoelectronic devices with enhanced performance and stability. Still, taking advantage of the solution processing of perovskite onto graphene is especially challenging. Here, MAPbBr₃ perovskite is grown on single-layer graphene/graphene oxide (Gr/GO) patterns with 120 µm periodicity using a solution-processed method. MAPbBr₃ rounded crystals are formed with sizes ranging from nanometers to microns, either forming continuous films or dispersed particles. A detailed morphological and structural study reveals a fully oriented perovskite and very different growth habits on the Gr/GO micro-patterns, which we relate to the substrate characteristics and the nucleation rate. A simple method for controlling the nucleation rate is proposed based on the concentration of the precursor solution and the number of deposited perovskite layers. The photoluminescence is analyzed in terms of the crystal size, strain, and structural changes observed. Notably, the growth on top of Gr/GO leads to a huge photostability of the MAPbBr₃ compared with that on glass. Especially outstanding is that of the microcrystals, which endure light densities as high as 130 kW/cm². These results allow for anticipating the design of integrated nanostructures and nanoengineered devices by growing high-stability perovskite directly on Gr/GO substrates. Full article

Flame-resistant polymer composites were prepared based on polyvinyl alcohol (PVA) as a polymer matrix and a polyphosphonate as flame retardant. Oxalic acid was used as crosslinking agent. LiClO₄, BaTiO₃, and graphene oxide were also incorporated into PVA matrix to increase the ionic conductivity. The obtained film composites were investigated by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry and microscale combustion tests. Incorporating fire retardant (PFRV), BaTiO₃, and graphene oxide (GO) into a material results in increased resistance to fire when compared to the control sample. A thermogravimetric analysis revealed that, as a general trend, the presence of PFRV and BaTiO₃ nanoparticles enhances the residue quantity at a temperature of 700 °C from 7.9 wt% to 23.6 wt%. Their dielectric properties were evaluated with Broad Band Dielectric Spectroscopy. The electrical conductivity of the samples was determined and discussed in relation to the LiClO₄ content. The electrical properties, including permittivity and conductivity, are being enhanced by the use of LiClO₄. Additionally, a relaxation peak has been observed in the dielectric losses at frequencies exceeding 103 Hz. The electrical properties, including permittivity and conductivity, are being enhanced by the use of LiClO₄. Additionally, a relaxation peak has been observed in the dielectric losses at frequencies exceeding 103 Hz. Out of the various composites tested, the composite containing 35 wt% of LiClO₄ exhibits the highest alternating current (AC) conductivity, with a measured value of 2.46 × 10⁻³ S/m. Taking into consideration all the aspects discussed, these improved composites are intended for utilization in the manufacturing of Li-Ion batteries. Full article

Nowadays, virus pandemics have become a major burden seriously affecting human health and social and economic development. Thus, the design and fabrication of effective and low-cost techniques for early and accurate virus detection have been given priority for prevention and control of such pandemics. Biosensors and bioelectronic devices have been demonstrated as promising technology to resolve the major drawbacks and problems of the current detection methods. Discovering and applying advanced materials have offered opportunities to develop and commercialize biosensor devices for effectively controlling pandemics. Along with various well-known materials such as gold and silver nanoparticles, carbon-based materials, metal oxide-based materials, and graphene, conjugated polymer (CPs) have become one of the most promising candidates for preparation and construction of excellent biosensors with high sensitivity and specificity to different virus analytes owing to their unique π orbital structure and chain conformation alterations, solution processability, and flexibility. Therefore, CP-based biosensors have been regarded as innovative technologies attracting great interest from the community for early diagnosis of COVID-19 as well as other virus pandemics. For providing precious scientific evidence of CP-based biosensor technologies in virus detection, this review aims to give a critical overview of the recent research related to use of CPs in fabrication of virus biosensors. We emphasize structures and interesting characteristics of different CPs and discuss the state-of-the-art applications of CP-based biosensors as well. In addition, different types of biosensors such as optical biosensors, organic thin film transistors (OTFT), and conjugated polymer hydrogels (CPHs) based on CPs are also summarized and presented. Full article