Search Results (1,392)

The development of flexible and self-powered electronic systems requires triboelectric materials that combine high charge retention, mechanical compliance, and stable dielectric properties. Here, we report a redox reaction approach to prepare liquid metal particle-reduced graphene oxide (LMP@rGO) core–shell structures and introduce into a poly(acrylic acid) (PAA) hydrogel to create a high-performance triboelectric layer. The spontaneous interfacial reaction between gallium oxide of LMP and graphene oxide produces a conformal rGO shell while simultaneously removing the native insulating oxide layer onto the LMP surface, resulting in enhanced colloidal stability and a controllable semiconductive bandgap of 2.7 (0.01 wt%), 2.9 (0.005 wt%) and 3.2 eV (0.001 wt%). Increasing the GO content promotes more complete core–shell formation, leading to higher zeta potentials, stronger interfacial polarization, and higher electrical performance. After embedding in PAA, the LMP@rGO structures form hydrogen-bonding networks with the hydrogel nature, improving both dielectric constant and charge retention while notably preserving soft mechanical compliance. The resulting LMP@rGO/PAA hydrogels show enhanced triboelectric output, with the 2.0 wt/vol% composite generating sufficient power to illuminate more than half of 504 series-connected LEDs. All the results demonstrate the potential of LMP@rGO hydrogel composites as promising triboelectric layer materials for next-generation wearable and self-powered electronic systems. Full article

In this study, copper–carbon material composites, Cu/CM (where CM is reduced graphene oxide (rGO), graphitic carbon nitride (g-C₃N₄), their mixture, and N-doped reduced graphene oxide (N-rGO)), were prepared using a simple method of chemical reduction of copper cations in the presence of CM related to molecular-level mixing methods. Additionally, copper cations from its oxides present in the composites were reduced in an electrochemical cell by depositing them on the surface of a horizontally positioned cathode. The structure and morphology of the Cu/CM composites were studied using electron microscopy and X-ray diffraction analysis. The thermal stability and elemental analysis were determined for the carbon materials. The resulting Cu/CM composites were used as electrocatalysts in the electrohydrogenation of the aromatic ketone, acetophenone. Cu/rGO and Cu/N-rGO composites with a 1:1 ratio exhibited catalytic activity in this process, increasing the rate of APh hydrogenation and its degree of conversion with the selective formation of a single product, methyl phenyl carbinol (or 1-phenylethanol), compared to the electrochemical reduction of APh on a cathode without a catalyst. The Cu/N-rGO composite demonstrated the highest electrocatalytic activity. Full article

This study investigates pristine and doped ZnO thin films fabricated via the sol-gel technique, aiming to address efficiency challenges when used as transparent conductive oxide (TCO) layers in thin-film solar cells. ZnO was first doped with aluminum (Al), and subsequently with both Al and reduced graphene oxide (rGO), to evaluate the individual and combined effects of these dopants. The optimal pH value for the ZnO structure was initially determined, with the film produced at pH 9 exhibiting the most favorable characteristics. Al doping was then optimized at a ratio of Al/(Al + Zn) = 0.2, followed by optimization of the graphene content at 1.5 wt%. In this context, the structural, optical, and electrical properties of pristine ZnO, Al-doped ZnO (AZO), and Al and graphene co-doped ZnO (Gr:AZO) thin films were systematically investigated. These films were integrated as TCO layers into Cu₂SnS₃ (CTS)-based thin-film solar cells fabricated via physical vapor deposition (PVD). The cell architecture employed an 80 nm pristine ZnO window layer, while the doped ZnO films (300 nm) served as TCO layers. To assess the influence of the chemically deposited top layers, device performance was compared against a reference cell in which all layers were fabricated entirely using PVD. As expected, the reference cell exhibited superior performance compared to the cell whose AZO layer deposited chemically; however, the incorporation of both Al and graphene significantly enhanced the efficiency of the chemically modified cell, outperforming devices using only pristine or singly doped ZnO films. These results demonstrate the promising potential of co-doped solution-processed ZnO films as an alternative TCO layer in improving the performance of thin-film solar cell technologies. Full article

The synthesis, in particular the industrial production, of pharmaceuticals requires a broad arsenal of synthetic reactions capable of selectively forming specific structural motifs and assembling smaller building blocks into complex molecules. The Chan–Evans–Lam cross-coupling reaction, which forms a bond between a N-nucleophile and an aryl group from a boronic acid, catalysed by copper salts, is a typical example of this synthetic route. Considering the toxicity of copper and the stringent regulatory limits for its residues in final pharmaceutical products, a heterogeneous catalytic approach offers a viable alternative for this transformation. In this work, we present a simply and reproducibly synthesized catalyst based on copper nanoparticles supported on reduced graphene oxide (Cu-rGO), with high efficiency in a model Chan–Lam reaction involving benzimidazole and aniline derivatives with substituted boronic acids. Full article

This study includes a comparative analysis of four graphene-based electrochemical sensors used for the detection of melatonin, an endogenous hormone involved in circadian rhythm regulation and associated with various neurological pathologies. The sensors were based on screen-printed electrodes (SPE) modified with graphene (G), graphene modified with gold nanoparticles (AuNPs/G), graphene oxide (GO), and reduced graphene oxide (rGO). Melatonin was extracted from commercially available pharmaceutical products, purified, and characterized using UV-Vis spectroscopy, FTIR spectrometry, and HPLC. The performance of the electrodes was evaluated via cyclic voltammetry, using potassium ferrocyanide and standard melatonin solutions to determine the kinetic characteristics, while square-wave voltammetry was employed to determine the detection and quantification limits. G/SPE showed the best performance, with a detection limit of 0.3424 μM, followed by AuNPs/G/SPE with an LOD of 1.2768 μM. GO/SPE had the poorest performance (LOD 23.1056 μM), and rGO/SPE had an LOD of 5.8503 μM. Testing of sensors on pharmaceuticals showed accurate quantification of melatonin in a complex environment. The results highlight the potential of G/SPE and AuNPs/G/SPE sensors for use in the rapid and accurate detection of melatonin in pharmaceutical and biomedical applications. Full article

This study utilizes QM/MM Born–Oppenheimer Molecular Dynamics in order to model the process of intermolecular binding between reduced graphene oxide (rGO) and butadiene–acrylonitrile copolymer (PBDAN) with a monomer ratio of 2:1. This research aims to elucidate the structural reasons behind the enhancing properties of the substrate, focusing on the polymer matrix. The behavior of each phase was examined and discussed. More importantly, the intermolecular interactions within the interphase zone of adsorption were investigated on an atomic scale. We found and characterized 58 such instances, grouped into hydrogen bonds and three types of stacking: π–π, σ–π, and σ–n. Each occurrence was analyzed through the use of radial distribution functions. Five spontaneous chemical processes within the rGO nanoparticle were modeled and characterized. Two of them were found to provide stabilization only within the substrate, while the rest are relevant for the overall constitution of the heteromaterial. Perhaps most intriguing is the process of self-repair as part of the vacancy defect. This occurs entirely within the carbon frame of the rGO layer. We believe our results to be of importance for a large set of ligand materials, mostly those which contain unsaturated bonds and electronegative atoms. Full article

A series of reduced graphene oxide–calcium sodium aluminosilicate (rGO-CSA) composites with various rGO/CSA weight ratios (i.e., rGO/CSA 1/2.5, 1/5, 1/10, and 1/15) were successfully synthesized via hydrothermal reaction of CSA particles and GO nanosheets. The chemical compositions and morphology of as-synthesized rGO-CSA composites were characterized by XRD, SEM, BET and FTIR. Results from SEM revealed that CSA particles were deposited on the surface of rGO nanosheets resulting in rGO-CSA nanocomposites. N₂-BET results showed that rGO-CSA4 composites with an rGO/CSA loading ratio of 1/15 showed a high specific surface area of 824.7 m²/g, which is higher than that of raw rGO (370.7 m²/g) and CSA (719.8 m²/g) materials. According the BET and SEM, it can be confirmed that the combination of rGO with CSA can reduce stacking during the drying process of rGO. The as-prepared rGO-CSA nanocomposites exhibited an excellent performance in the adsorption of methylene blue (MB). The rGO-CSA3 material exhibits an MB saturation adsorption capacity of 66.3 mg/g. Since rGO is the only adsorption-active material in the rGO-CSA3 composite, the rGO (9.09 wt%) in rGO-CSA exhibited an MB saturation adsorption capacity of 729.4 mg/L after content correction, which is far greater than the value of raw rGO material. The rGO-CSA3 composites showed superior adsorption efficiency of MB, mainly due to CSA particles effectively reducing rGO nanosheets stacking during the drying process. Full article

A composite based on θ-Al₂O₃ microspheres coated with graphene oxide (GO) and reduced graphene oxide (RGO) was prepared and evaluated as a sorbent for the removal of synthetic dyes from aqueous solutions. GO was synthesized by a modified Hummers’ method and deposited onto alumina microspheres via ultrasound-assisted treatment under various conditions, followed by supercritical reduction to obtain the Al₂O₃_RGO composite. The structure, morphology, and composition of the materials were characterized by Raman spectroscopy, SEM, TGA/DSC, FTIR, and XRD, revealing the formation of mono- and few-layer GO/RGO coatings on the substrate surface. Adsorption tests for cationic methylene blue (MB) dye and anionic methyl orange (MO) dye demonstrated that the alumina substrate was inactive, whereas GO- and RGO-coated microspheres exhibited high adsorption efficiency for MB and partial uptake of MO from water solutions. In mixed-dye solutions, both Al₂O₃_GO and Al₂O₃_RGO composites showed selectivity toward MB, and the RGO-based composite demonstrated enhanced MB adsorption at low concentrations. The results highlight GO/RGO-coated θ-Al₂O₃ microspheres as convenient and selective composite sorbents for water purification processes. Full article

In this study, Ni/Mn-doped cobalt–reduced graphene oxide (Co-RGO) composites were successfully synthesized as advanced electrode materials for supercapacitors. The structural and morphological properties of the composites were characterized using FTIR, XRD, SEM, TEM, and UV–Vis spectroscopy. Their electrochemical performance was evaluated through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD). Among the prepared samples, Co-RGO doped with Ni/Mn at a 40:10 ratio exhibited the most outstanding capacitive behavior, achieving a specific capacitance of 7414 F g⁻¹ at a current density of 10 A g⁻¹, along with a high energy density of 565 Wh kg⁻¹ and a power density of 4998 W kg⁻¹. The high capacitance arises from faradaic pseudocapacitive reactions rather than electric double-layer capacitance, eliminating the need for a large surface area. These results confirm that Ni doping significantly enhances pseudocapacitance and conductivity in the Co-RGO matrix, making Ni/Mn (40:10)–Co-RGO a potential material for advanced energy storage systems. Full article

A thorough understanding of the dispersion characteristics of graphene oxide (GO), its micro-pore enhancement mechanisms, and correlations with mechanical properties are crucial for advancing high-strength, durable green concrete. Introducing recycled concrete powder (RCP) can weaken the interfacial transition zone (ITZ) and inhibit hydration reactions, degrading the pore structure and affecting mechanical strength and durability. However, traditional methods struggle to accurately characterize and quantitatively analyze GO-modified pore structures due to their nanoscale size, microstructural diversity, and characterization technique limitations. To address these challenges, this study integrates deep learning-based backscattered electron image analysis with deep Taylor decomposition feature extraction. This innovative method systematically analyzes pore characteristic evolution and the correlation between porosity and mechanical strength. The results indicate that GO promotes Calcium Silicate Hydrate gel growth, refines pores, and reduces pore connectivity, decreasing the maximum pore size by 33.4–45.2%. Using a Convolutional Neural Network architecture, BSE images are efficiently processed and analyzed, achieving an average recognition accuracy of 94.3–96.9%. The optimized degree of GO coating on enhanced regions reaches 30.2%. Fitting porosity with mechanical strength and chloride ion permeability coefficients reveals that enhanced regions exhibit the highest correlation with mechanical strength and durability in regenerated cementitious materials, with R² values ranging from 0.79 to 0.99. The deep learning-assisted pore structure characterization method demonstrates high accuracy and efficiency, providing a critical theoretical basis and data support for performance optimization and engineering applications of recycled cementitious materials. This research expands the application of deep learning in building materials and offers new insights into the relationship between the microstructural and macroscopic properties of recycled cementitious materials. Full article

The objective of this research was to assess the tribological performance and the capacity to withstand low-temperature degradation of alumina-zirconia-tantalum (ZTA) ceramic-metal composites, modified with 0.5 vol.% graphene oxide (GO) under ball (alumina) on disk dry sliding conditions. The studied ceramic and ceramic-metal composites reinforced with 20 vol.% of tantalum particles were prepared using a colloidal mixing and sintered at a temperature of 1500 °C using a spark plasma sintering technique. In contrast to ZTA ceramic, the wear performance of composites with metal particles and graphene oxide was significantly improved, regardless of the chosen load (10 N and 40 N). The results showed an improvement in the friction coefficient of about 20% and 15% at low and high load, respectively. The wear rate was reduced by 2 and 7 times at 10 N and 40 N, respectively. Raman and energy dispersive spectroscopy confirmed that ZTA-Ta-rGO composites exhibited superior wear resistance primarily because a protective tribolayer formed on their surfaces during wear. This layer effectively lubricated the surfaces, leading to a decrease in both friction and the rate of material loss. Furthermore, these composites exhibited excellent resistance to low-temperature degradation. The results obtained will serve as a starting point for future biomedical testing directions, opening up new perspectives for the use of these materials in biomedicine. Full article

Creatinine (Crn) is a clinically relevant biomarker commonly used for the diagnosis and monitoring of kidney disease. In this work, we report the fabrication of reduced-graphene-oxide-based field-effect transistors (rGO FETs) for Crn detection. These devices were functionalized using a layer-by-layer (LbL) assembly, in which polyethyleneimine (PEI) and creatinine deiminase (CD) were alternately deposited. This LbL strategy allows for the effective incorporation of CD without compromising its structural or functional integrity, while also taking advantage of the local pH changes caused by creatinine hydrolysis. It also benefits from the use of a polyelectrolyte that can amplify the enzymatic signal. Furthermore, it enables scalable and efficient fabrication. These transistors also address the challenges of point-of-care implementation in single-use cartridges. It is worth noting that the devices showed a linear relationship between the Dirac-point shift and the logarithm of the creatinine concentration in the 20–500 µM range in diluted simulated urine. The sensor response improved with increasing numbers of PEI/CD bilayers. Furthermore, the functionalized FETs demonstrated rapid detection dynamics and good long-term stability. Present results confirm the potential of these devices as practical biosensors for sample analysis under real-world conditions, making them ideal for implementation in practical settings. Full article

The development of implantable neural interfaces is essential for enabling bidirectional communication between the nervous system and prosthetic devices, yet their evaluation still relies primarily on in vivo models which are costly, variable, and ethically constrained. Here, we report a bio-inspired artificial nerve simulator engineered as a reproducible ex vivo platform for pre-implantation testing of plug-type electrodes. The simulator is fabricated from a conductive hydrogel composite based on reduced graphene oxide (rGO), polyaniline (PANI), agarose, sucrose, and sodium chloride, with embedded conductive channels that replicate the fascicular organization and conductivity of peripheral nerves. The resulting construct exhibits impedance values of ~2.4–2.9 kΩ between electrode needles at 1 kHz, closely matching in vivo measurements (~2 kΩ) obtained in Sus scrofa domesticus nerve tissue. Its structural and electrical fidelity enables systematic evaluation of electrode–nerve contact properties, signal transmission, and insertion behavior under controlled conditions, while reducing reliance on animal experiments. This bio-inspired simulator offers a scalable and physiologically relevant testbed that bridges materials engineering and translational neuroprosthetics, accelerating the development of next-generation implantable neural interfaces. Full article

Delamination remains a critical failure mode in carbon fiber-reinforced polymer (CFRP) composites, particularly under cyclic loading in aerospace and automotive applications. This study explores whether nanoscale reinforcement with graphene-based materials can enhance delamination resistance and identifies the most effective nanofiller type. Two distinct graphene nanospecies—reduced graphene oxide (rGO) and carboxyl-functionalized graphene nanoplatelets (HDPlas)—were incorporated at 0.5 wt% into CFRP laminates and tested under static and fatigue mode I loading using double cantilever beam (DCB) tests. Both nanofillers enhanced interlaminar fracture toughness compared to the neat composite: rGO improved the energy release rate by 36%, while HDPlas achieved a remarkable 67% enhancement. Fatigue testing showed even stronger effects, with the fatigue threshold energy release rate rising by 24% for rGO and 67% for HDPlas, leading to a fivefold increase in fatigue life for HDPlas-modified laminates. A compliance calibration method enabled continuous monitoring of crack growth over one million cycles. Fractography analysis using scanning electron microscopy revealed that both nanofillers activated crack bifurcation, enhancing energy dissipation. However, the HDPlas system further exhibited extensive nanoparticle pull-out, creating a more tortuous crack path and superior resistance to crack initiation and growth under cyclic loading. Full article

This study investigates the impact of ultrasonic treatment on the deagglomeration of aggregates of single-walled carbon nanotubes (SWCNTs) and reduced graphene oxide (rGO). The aim of the research is to enhance the electrical conductivity of a biopolymer hydrogel designed for coating metallic neurostimulation electrodes. Biocompatible coating materials are essential for the safe long-term function of implants within the body, enabling the transmission of nerve impulses to external devices for signal conversion and neurostimulation. Dynamic light scattering (DLS) was employed to monitor the dispersion state, in conjunction with measurements of specific electrical conductivity. The mass loss and swelling capacity were evaluated over an 80-day period to account for the effects of degradation during in vitro studies. Samples of flexible–elastic hydrogels for electrodes with complex geometry were formed by the photopolymerization of a photopolymerizable medium, similar to a photoresist. Analysis of the dependence of temperature and normalized optical transmittance on the duration of laser photopolymerization made it possible to determine the optimal polymerization temperature for the photopolymerizable medium as −28 °C. This temperature regime ensures maximum reproducibility of hydrogel formation and eliminates the presence of unpolymerized areas. The article presents a biopolymer hydrogel with SWCNTs and rGO nanoparticles in a 1:1 ratio. It was found that sufficient specific electrical conductivity is achieved using SWCNTs with a characteristic hydrodynamic radius of R = 490 nm and rGO with R = 210 nm (sample Col/BSA/CS/Eosin Y/SWCNTs (490 nm)/rGO 4). The photopolymerized hydrogel 4 demonstrated sufficient biocompatibility, exceeding the control sample by 16%. According to the results of in vitro studies over 80 days, this sample exhibited moderate degradation of 45% while retaining its swelling ability. The swelling degree decreased by 50% compared to the initial value of 170%. The presented hydrogel 4 is a promising coating material for implantable metallic neurostimulation electrodes, enhancing their stability in the physiological environment. Full article