Search Results (18)

This work presents the improvement of the electro-optical response of n-type crystalline silicon via dip-coated graphene oxide (GO) thin films. GO was deposited on Si/SiO₂ by immersion, and the resulting heterostructures were characterized by cyclic voltammetry measurements and Raman spectroscopy. Raman analysis revealed a slight but measurable broadening (~0.7 cm⁻¹) of the Si TO phonon mode at 514 cm⁻¹, indicating local interfacial strain. Cyclic voltammetry measurements showed a substantial increase in photocurrent in comparison to pristine silicon substrates. These effects are attributed to a GO-induced p-type inversion layer and enhanced interfacial charge transfer. The results suggest that GO can serve as a functional interfacial layer for improving silicon-based optoelectronic and photoelectrochemical devices. Full article

The large-scale implementation of 2D material-based membranes is hindered by mechanical stability and mass transport control challenges. This work describes the fabrication, characterisation, and testing of self-standing graphene oxide (GO) membranes cross-linked with oxides such as Fe₂O₃, Al₂O₃, CaSO₄, Nb₂O₅, and a carbide, SiC. These cross-linking agents enhance the mechanical stability of the membranes and modulate their mass transport properties. The membranes were prepared by casting aqueous suspensions of GO and SiC or oxide powders onto substrates, followed by drying and detachment to yield self-standing films. This method enabled precise control over membrane thickness and the formation of laminated microstructures with interlayer spacings ranging from 0.8 to 1.2 nm. The resulting self-standing membranes, with areas between 0.002 m² and 0.090 m² and thicknesses from 0.6 μm to 20 μm, exhibit excellent flexibility and retain their chemical and physical integrity during prolonged testing in direct contact with ethanol/water and methanol/water mixtures in both liquid and vapour phases, with stability demonstrated over 24 h and up to three months. Gas permeation and chemical characterisation tests evidence their suitability for gas separation applications. The interactions promoted by the oxides and carbide with the functional groups of GO confer great stability and unique mass transport properties—the Nb₂O₅ cross-linked membranes present distinct performance characteristics—creating the potential for scalable advancements in cross-linked 2D material membranes for separation technologies. Full article

With the rapid development of the transport industry, there is a higher demand for environmental friendliness, durability, and stability of tires. Rubber composites with excellent mechanical properties, abrasion resistance, and low heat generation are very important for the preparation of green tires. In this study, the all-aqueous phase process was initially employed to prepare 2-Amino-5-mercapto-1,3,4-thiadiazole (AZT) functionalized graphene oxide (AGO). Subsequently, modified graphene oxide/silica/natural rubber (AGO/SiO₂/NR) composites were obtained through latex blending and hot press vulcanization processes. This method was environmentally friendly and exhibited high modification efficiency. Benefiting from the good dispersion of AGO in the latex and the cross-linking reaction between AGO and NR, AGO/SiO₂/NR composites with good dispersion and enhanced interfacial interaction were finally obtained. AGO/SiO₂/NR composites showed significantly improved overall performance. Compared to GO/SiO₂/NR composites, the tensile strength (28.1 MPa) and tear strength (75.3 N/mm) of the AGO/SiO₂/NR composites were significantly increased, while the heat build-up value (10.4 °C) and DIN abrasion volume (74.9 mm³) were significantly reduced. In addition, the steady-state temperature field distribution inside the tire was visualized by ANSYS finite element simulation. The maximum temperature of the prepared AGO/SiO₂/NR was reduced by 18.2% compared to that of the GO/SiO₂/NR tires. This strategy is expected to provide a new approach for the development of low energy consumption, environmentally friendly, and long-life rubber for tires. Full article

We synthesized a boron-doped reduced graphene oxide (BrGO) material characterized by various electrical properties, through simultaneous thermal reduction and doping procedures, using a metal–organic chemical vapor deposition technique. X-ray photoelectron spectroscopy (XPS) was used to study the impact of the doping level on the B bonding in the reduced graphene oxide (rGO) layer that is influenced by the annealing temperature. The synthesized BrGO layer demonstrated a high B concentration with a considerable number of O-B bonds, that were altered by annealing temperatures. This resulted in a decreased work function and the formation of a Schottky contact between the BrGO and n-type Si substrate. Due to the higher proportion of B-C and B-C₃ bonding in the BrGO/Si device than that in the rGO/Si, the decreased Schottky barrier height of the BrGO/n-Si vertical junction photodetector resulted in a higher responsivity. This study showcases a promise of a simple B-doping method in use to alter the electrical characteristics of graphene materials. Full article

The study reveals the polymer–crosslinker interactions and functionality of hydrophilic nanofibers for antibacterial wound coatings. Coaxial electrospinning leverages a drug encapsulation protocol for a core–shell fiber composite with a core derived from polyvinyl alcohol and polyethylene glycol with amorphous silica (PVA-PEG-SiO₂), and a shell originating from polyvinyl alcohol and graphene oxide (PVA-GO). Crosslinking with GO and SiO₂ initiates the hydrogel transition for the fiber composite upon contact with moisture, which aims to optimize the drug release. The effect of hydrogel-inducing additives on the drug kinetics is evaluated in the case of chlorhexidine digluconate (CHX) encapsulation in the core of core–shell fiber composite PVA-PEG-SiO₂-1x-CHX@PVA-GO. The release rate is assessed with the zero, first-order, Higuchi, and Korsmeyer–Peppas kinetic models, where the inclusion of crosslinking silica provides a longer degradation and release rate. CHX medicated core–shell composite provides sustainable antibacterial activity against Staphylococcus aureus. Full article

This work reports the obtention of nanocompounds from epoxy resin (EP) with graphenes at three different oxidation degrees (GO1, GO2, and GO3), functionalized with 3-glycidyloxypropyl trimethoxysilane (GPTMS), and three different graphene concentrations (1%, 2%, and 3%). The aim is to improve GO compatibility in EP and obtain a nanocompound with synergistic properties. Ultrasonic bath was used to disperse the GO, a factor in the effective interaction between GO and the polymeric matrix. The nanocompounds were characterized by FTIR, SEM, and mechanical tension testing. The FTIR analysis evidenced stretching bonds created during the functionalization of graphene oxide (GO) with the silane (GPTMS); they are characteristic Si-O-Si and Si-O-C at 1000 and 1085 cm⁻¹, respectively. There was a difference between GO and GO-GPTMS nanocompounds regarding the formation of these signals. The SEM micrographs showed morphological changes when GO was added: the smooth fracture surface of EP became rougher. During tension testing, Young’s modulus (2.09 GPa) of GO2-GPTMS/epoxy nanocompounds (1% weight GO) increased by 35% while their resistance to traction (98.71 MPa) grew by 52%; both were higher than in pure EP. In conclusion, the variables studied (oxidation degrees and silanization) significantly affect the mechanical properties studied. Full article

This study investigates the degradation of a commercially available gear lubricant and the potential of nano-additives to mitigate such degradation. Initially, we performed an experimental study on the chemical degradation of commercially available API GL-4 EP90 gear lubricant by mixing the different concentrations of aqueous hydrochloric acid (aqueous HCl) varying from 0.0005% v/v up to 0.0025% v/v, while maintaining overall water content in the oil below the prescribed limits. The degradation was monitored using the pH value, total acid number (TAN) value, and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analysis. The experiments were performed on a developed gear test rig using conventional gear oil as well as chemically aged gear oil, and the corresponding results of pH value and wear debris were recorded. Based on the results, an empirical regression model between the concentration of aqueous HCl and lubricant aging time has been established. Under chemically aged lubricant, severe wear of gear was observed, which motivated us to explore suitable nano-additive to minimize the gear wear. Initially, three nano-additives—graphite, graphene, and “graphene oxide functionalized with silicon oxide (GO@SiO₂)”—were chosen. A series of tests were conducted using the design of experiments method (L8 and L16 orthogonal array) to investigate the effect of nano-additives and to find the optimum additive for wear performance. Finally, experiments were conducted on gear setup using the degraded lubricant optimized with nano-additive. Overall results indicate a very significant contribution of nano-additives in decreasing gear wear. Full article

Photo-nanotheranostics integrates near-infrared (NIR) light-triggered diagnostics and therapeutics, which are combined into a novel all-in-one phototheranostic nanomaterial that holds great promise for the early detection and precise treatment of cancer. In this study, we developed methylene blue-loaded mesoporous silica-coated gold nanorods on graphene oxide (MB-GNR@mSiO₂-GO) as an all-in-one photo-nanotheranostic agent for intracellular surface-enhanced Raman scattering (SERS) imaging-guided photothermal therapy (PTT)/photodynamic therapy (PDT) for cancer. Amine functionalization of the MB-GNR@mSiO₂ surfaces was performed using 3-aminopropyltriethoxysilane (APTES), which was well anchored on the carboxyl groups of graphene oxide (GO) nanosheets uniformly, and showed a remarkably higher photothermal conversion efficiency (48.93%), resulting in outstanding PTT/PDT for cancer. The in vitro photothermal/photodynamic effect of MB-GNR@mSiO₂-GO with laser irradiation showed significantly reduced cell viability (6.32%), indicating that MB-GNR@mSiO₂-GO with laser irradiation induced significantly more cell deaths. Under laser irradiation, MB-GNR@mSiO₂-GO showed a strong SERS effect, which permits accurate cancer cell detection by SERS imaging. Subsequently, the same Raman laser can focus on highly detected MDA-MB-23l cells for a prolonged time to perform PTT/PDT. Therefore, MB-GNR@mSiO₂-GO has great potential for precise SERS imaging-guided synergistic PTT/PDT for cancer. Full article

In this study, a nanoscale ionic liquid (NIL) GO@SiO₂ hybrid was synthesized by attaching silica nanoparticles onto graphene oxide (GO). It was then functionalized to exhibit liquid-like behavior in the absence of solvents. The physical and chemical properties of the synthesized samples were characterized by means of a transmission electron microscope, X-ray diffraction, Fourier transform infra-red, Raman spectroscopy, and thermogravimetric analysis. The tribological properties of the NIL GO@SiO₂ hybrid as a water-based (WB) lubricant additive were investigated on a ball-on-disk tribometer. The results illustrate that the NIL GO@SiO₂ hybrid demonstrates good dispersity as a WB lubricant, and can decrease both the coefficient of friction (COF) and wear loss. Full article

The measurement and control of humidity is a major challenge that affects the sensing properties of sensors used in high-precision equipment manufacturing industries. Graphene Oxide(GO)-based materials have been extensively explored in humidity sensing applications because of their high surface area and functional groups. However, there is a lack of effective bulk-manufacturing processes for the synthesis of 2D-based nanocomposites with comb electrodes. Moreover, water intercalation within the layers of 2D materials increases recovery time. This work demonstrates the enhanced sensing characteristics of a capacitive/resistive GO-MnZnO nanocomposite humidity sensor produced using a cost-effective single-pot synthesis process. The in-plane sensing layer consistently improves sensitivity and reduces response time for a wide range of relative humidity measurements (10% to 90%). Interdigitated gold electrodes with varying numbers of fingers and spacing were fabricated using photolithography on a Si/SiO₂ for a consistent sensor device platform. The choice of nanomaterials, dimension of the sensor, and fabrication method influence the performance of the humidity sensor in a controlled environment. GO nanocomposites show significant improvement in response time (82.67 times greater at 40% RH) and sensitivity (95.7 times more at 60% RH). The response time of 4.5 s and recovery time of 21 s was significantly better for a wider range of relative humidity compared to the reduced GO-sensing layer and ZnMnO. An optimized 6 mm × 3 mm dimension sensor with a 28-fingers comb was fabricated with a metal-etching process. This is one of the most effective methods for bulk manufacturing. The performance of the sensing layer is comparable to established sensing nanomaterials that are currently used in humidity sensors, and hence can be extended for optimal bulk manufacturing with minimum electrochemical treatments. Full article

Electrospinning is a well-established method for the fabrication of polymer biomaterials, including those with core-shell nanofibers. The variability of structures presents a great range of opportunities in tissue engineering and drug delivery by incorporating biologically active molecules such as drugs, proteins, and growth factors and subsequent control of their release into the target microenvironment to achieve therapeutic effect. The object of study is non-woven core-shell PVA–PEG–SiO₂@PVA–GO fiber mats assembled by the technology of coaxial electrospinning. The task of the core-shell fiber development was set to regulate the degradation process under external factors. The dual structure was modified with silica nanoparticles and graphene oxide to ensure the fiber integrity and stability. The influence of the nano additives and crosslinking conditions for the composite was investigated as a function of fiber diameter, hydrolysis, and mechanical properties. Tensile mechanical tests and water degradation tests were used to reveal the fracture and dissolution behavior of the fiber mats and bundles. The obtained fibers were visualized by confocal fluorescence microscopy to confirm the continuous core-shell structure and encapsulation feasibility for biologically active components, selectively in the fiber core and shell. The results provide a firm basis to draw the conclusion that electrospun core-shell fiber mats have tremendous potential for biomedical applications as drug carriers, photocatalysts, and wound dressings. Full article

This study prepared 4,4-diaminodiphenylmethane (DDM)-functionalized graphene oxide (GO)@silica dioxide (SiO₂) nano-composites through amidation reaction and low-temperature precipitation. The resulting modified GO, that was DDM−GO@SiO₂. The study found that DDM−GO@SiO₂ showed good dispersion and compatibility with thermoplastic polyurethane (TPU) substrates. Compared with pure TPU, the tensile strength of the TPU composites increased by 41% to 94.6 MPa at only 0.5 wt% DDM−GO@SiO₂. In addition, even when a small amount of DDM−GO@SiO₂ was added, the UV absorption of TPU composites increased significantly, TPU composites can achieve a UV shielding efficiency of 95.21% in the UV-A region. These results show that this type of material holds great promise for the preparation of functional coatings and film materials with high strength and weather resistance. Full article

This paper presents the relative humidity (RH) sensing response of a resistive sensor employing sensing layers based on a ternary nanocomposite comprising graphene oxide-oxidized carbon nanohorns-polyvinylpyrrolidone (GO-CNHox–PVP), at 1/1/1, 1/2/1, and 1/3/1 w/w/w mass ratios. The sensing structure is composed of a silicon substrate, a SiO₂ layer, and interdigitated transducers (IDT) electrodes, on which the sensing layer is deposited via the drop-casting method. The morphology and the composition of the sensing layers are investigated through scanning electron microscopy (SEM) and RAMAN spectroscopy. The RH sensing capability of each carbonaceous nanocomposite-based thin film was analyzed by applying a current between the two electrodes and by measuring the voltage difference when varying the RH from 0% to 100% in humid nitrogen. The sensors have a room temperature response comparable to that of a commercial humidity sensor and are characterized by a rapid response, excellent linearity, good sensitivity, and recovery time. The manufactured sensing devices’ transfer functions were established, and we extracted the response and recovery times. While the structures with GO/CNHox/PVP at 1/1/1 ratio (w/w/w) had the best performance in terms of relative sensibility, response time, and recovery time, the sensors employing the GO/CNHox/PVP nanocomposite at the 1/2/1 ratio (w/w/w) had the best linearity. Moreover, the ternary mixture proved to have much better sensing properties compared to CNHox and CNHox-PVP-based sensing layers in terms of sensitivity and linearity. Each component of the ternary nanocomposites’ functional role is explained based on their physical and chemical properties. We analyzed the potential mechanism associated with the sensors’ response; among these, the effect of the p-type semiconductor behavior of CNHox and GO, correlated with swelling of the PVP, was dominant and led to increased resistance of the sensing layer. Full article

Gene therapy has been considered a promising strategy for treating several inherited diseases and acquired complex disorders. One crucial challenge yet to be solved to ensure the nanomaterials’ success in delivering gene therapies is their ability to escape from endosomes. To address this issue, we previously developed magnetite nanoparticles conjugated with the antimicrobial peptide Buforin II, which showed potent translocating and endosomal escape abilities in several cell lines. In this work, we propose developing new cell-penetrating nanoplatforms by interfacing graphene oxide (GO) with powerful translocating peptides to take advantage of already tested and unique peptides as well as the distinctive interactions of GO with the phospholipids of membranes and endosomes. GO was prepared by the modified Hummers’ method through the oxidation of graphite sheets. Next, the functionalization of GO was carried out by rendering pendant amine groups to the GO surface. Thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) were used to corroborate the successful functionalization of the nanoplatform. FTIR analysis exhibited the peaks related to the distinct carboxyl groups of GO and the Si–O bonds after silanization. TGA allowed us to estimate a silanization efficiency of 38%. Future work will be focused on conjugating Buforin II and assessing translocation efficiency by conducting uptake assays in liposomes and various cell lines. Additionally, endosomal escape will be determined via confocal microscopy by labeling the peptide with fluorescent molecules and examining colocalization with the fluorescent marker of endosomes, LysoTracker. By taking advantage of the exceptional qualities in terms of the physicochemical, electrical, and optical properties of GO, this study might provide novel strategies to overcome limitations commonly faced, such as low stability of the translocating biomolecules and endosomal entrapment. Full article

Reduction of graphene oxide is one of the most promising strategies for obtaining bulk quantities of graphene-like materials. In this study, graphene oxide was deposited on SiO₂ and reduced by annealing at 500 K under vacuum conditions (5 × 10⁻¹ Pa). Here, graphene oxide films as well as their chemical changes upon heating were characterized in depth by X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning electron and atomic force microscopies. From the chemical point of view, the as prepared graphene oxide films presented a large quantity of oxidized functional groups that were reduced to a large extent upon heating. Moreover, residual oxidized sulfur species that originated during the synthesis of graphene oxide (GO) were almost completely removed by heating while nitrogen traces were integrated into the carbon framework. On the other hand, regarding structural considerations, reduced graphene oxide films showed more homogeneity and lower roughness than graphene oxide films. Full article