Search Results (179)

Films of a Ni/Al-layered double hydroxide intercalated with reduced graphene oxide were deposited, by means of a simple and rapid electrochemical synthesis, on Pt electrodes previously submitted to a special cleaning procedure. The aim of the research was to determine whether the better electrocatalytic properties of the Ni(III)/Ni(II) couple, due to the presence of the carbon nanomaterial, as compared to the Ni/Al-LDH alone, could allow glucose detection at physiological pHs, as normally LDHs work as redox mediators in basic solutions. Chronoamperometric experiments were carried out by applying a potential of 1.0 V vs. SCE to the electrode soaked in solutions buffered at pHs from 5.0 to 9.0 to which glucose was continuously added. The steady-state currents increased as the pH solution increased, but at pH = 7.0 the modified electrode exhibited a fast and rather sensitive response, which was linear up to 10.0 mM glucose, with a sensitivity of 0.56 A M⁻¹ cm⁻² and a limit of detection of 0.05 mM. Our results suggest the potential application of Ni/Al-LDH(ERGO) composite for the non-enzymatic detection of glucose or other oxidizable analytes under biological conditions. Full article

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

Nickel hydroxide has ultra-high energy storage capacity in supercapacitors, but poor electrical conductivity limits their further application. The use of graphene to improve its conductivity is an effective measure, but how to suppress the stacking of graphene and improve the overall performance of composite materials has become a new challenge. In this work, a well-designed substrate of N-doped carbon nanowires with reduced graphene oxide (NCNWs/rGO) was fabricated by growing polypyrrole (PPy) nanowires between GO nanosheets layers and then calcining them at high temperatures. This NCNWs/rGO substrate can effectively avoid the stacking of rGO nanosheets, and provides sufficient sites for the subsequent in situ growth of Ni(OH)₂, forming a uniform and stable Ni(OH)₂/NCNWs/rGO composite material. Benefiting from the abundant pores, high specific surface area (107.2 m² g⁻¹), and conductive network throughout the NCNWs/rGO substrate, the deposited Ni(OH)₂ can not only realize an ultra-high loading ratio, but also exposes more active surfaces (221.3 m² g⁻¹). After a comprehensive electrochemical test, it was found that the Ni(OH)₂/NCNWs/rGO positive materials have a high specific capacitance of 2016.6 F g⁻¹ at a scan rate of 1 mV s⁻¹, and exhibit significantly better stability. The assembled Ni(OH)₂/NCNWs/rGO//AC asymmetric supercapacitor could achieve a high energy density of 85.2 Wh kg⁻¹ at power densities of 381 W kg⁻¹. In addition, the asymmetric supercapacitor has excellent stability and could retain 70.1% of initial capacitance after 10,000 cycles. These results demonstrate the feasibility of using NCNWs/rGO substrate to construct high-performance supercapacitor electrode materials, and it is also expected to be promoted in other active composite materials. Full article

The long-term corrosion and antibacterial evaluation of bioactive coating obtained by matrix-assisted pulsed laser evaporation (MAPLE) on TiZrTaAg is crucial for assessing its potential in biomedical applications. The MAPLE deposition technique involves the formation of a dense and adherent layer on the surface of the alloy which can include a multitude of components such as bioactive glass, ZnO and graphene oxide. Long-term corrosion studies in simulated body fluids evaluate the stability and integrity of the coating over extended periods, ensuring its durability in the physiological environment. The results showed that the coatings, especially the one incorporating graphene oxide (GO), significantly reduced the corrosion rate of TiZrTaAg compared to the uncoated alloy. Antibacterial evaluation assesses the coating’s ability to inhibit bacterial colonization and biofilm formation, which are major concerns in implant-associated infections. The coatings demonstrated high antibacterial activity, with the one with the GO-containing film exhibiting the highest bacterial inhibition, achieving 83% against Staphylococcus aureus and 71% against Escherichia coli. The study concluded that the MAPLE-modified TiZrTaAg alloy with bioactive coatings, particularly the one with GO, shows promising potential for biomedical applications due to enhanced corrosion resistance and strong antibacterial properties. Full article

The study presents the ethanol vapor sensing performance of a resistive sensor that utilizes a quaternary nanohybrid sensing layer composed of holey carbon nanohorns (CNHox), graphene oxide (GO), SnO₂, and polyvinylpyrrolidone (PVP) in an equal mass ratio of 1:1:1:1 (w/w/w/w). The sensing device includes a flexible polyimide substrate and interdigital transducer (IDT)-like electrodes. The sensing film is deposited by drop-casting on the sensing structure. The morphology and composition of the sensitive film are analyzed using scanning electron microscopy (SEM), Energy Dispersive X-ray (EDX) Spectroscopy, and Raman spectroscopy. The manufactured resistive device presents good sensitivity to concentrations of alcohol vapors varying in the range of 0.008–0.16 mg/cm³. The resistance of the proposed sensing structure increases over the entire range of measured ethanol concentration. Different types of sensing mechanisms are recognized. The decrease in the hole concentration in CNHox, GO, and CNHox due to the interaction with ethanol vapors, which act as electron donors, and the swelling of the PVP are plausible and seem to be the prevalent sensing pathway. The hard–soft acid-base (HSAB) principle strengthens our analysis. Full article

Graphene oxide (GO) has emerged as a carbon-based nanomaterial providing a different pathway to graphene. One of its most notable features is the ability to partially reduce it, resulting in graphene-like sheets through the elimination of oxygen-including functional groups. In this paper, the effect of localized interactions in an Ag/GO/Au multilayer system was studied to explore its potential for photonic applications. GO was dip-coated onto magnetron-sputtered silver, followed by the deposition of a thin gold film to form an Ag/GO/Au structure. Micro-Raman Spectroscopy, SEM and Variable Angle Ellipsometry (VASE) measurements were performed on the Ag/GO/Au structure. An interesting behavior of the GO deposited on magnetron-sputtered silver with the formation of Ag nanostructures on top of the GO layer is reported. In addition to typical GO bands, Micro-Raman analysis reveals peaks such as the 1478 cm⁻¹ band, indicating a transition from sp³ to sp² hybridization, confirming the partial reduction of GO. Additionally, calculations based on effective medium theory (EMT) highlight the potential of Ag/GO structures in hyperbolic metamaterials for photonics. The medium exhibits dielectric behavior up to 323 nm, transitions to type I HMM between 323 and 400 nm and undergoes an Epsilon Near Zero and Pole (ENZP) transition at 400 nm, followed by type II HMM behavior. Full article

The electrodeposition of ZnO films was studied using potentiostatic mode in varying conditions including the presence of graphene oxide (GO) as a buffer layer and an additional deposition step. The obtained films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform Infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The effect of electrodeposition conditions on the adsorption and photocatalytic properties of ZnO nanostructured films was analyzed by using methylene blue (MB) as a model dye molecule and exposure to UV light. The results indicated a marked effect of GO content in the buffer layer and the duration of nucleation on the properties of electrodeposited ZnO films. Lower GO content and an additional deposition step of 60 s resulted in the best adsorption and photocatalytic activity, these being 7 and 5-folds, respectively, in comparison to ZnO in absence of these adjustments. The MB photodegradation was found to follow first-order kinetics, the rate constant reaching a value of 2.38 × 10⁻³ min⁻¹. Full article

This study investigated a hybrid electrode based on titanium/titanium dioxide nanowires/reduced graphene oxide (Ti-TiO₂(NW)/rGO) that was developed in two stages. The Ti-TiO₂(NW)/rGO was obtained by hydrothermal treatment in a mixed solution of H₂O₂ and melamine for Ti-TiO₂ support, followed by a simple spin-coating deposition method and thermal oxidation in a controlled atmosphere of nitrogen gas (99%). The as-prepared structures of electrodes were characterized using ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). In addition, the electrochemical behavior was assessed by cyclic voltammetry (CV) in a 1M HNO₃-supporting electrolyte and in the presence of 4 mM K₄Fe(CN)₆ 3H₂O to determine the electroactive surface area and apparent diffusion coefficient of the hybrid electrode. The development of the Ti-TiO₂(NW)/rGO hybrid electrode provides a sensitive method for photo-electrooxidation of doxorubicin due to exploiting the synergistic and remarkable properties of the nanowires of TiO₂ and of reduced graphene oxide (rGO) layer on the electrode surface. Full article

Wood modification with graphene oxide can give it unique features characteristic of other materials. However, the durability of the newly acquired features is of great importance. To better understand them, it is worth conducting an in-depth analysis of the structural changes that occur in wood under the influence of modification with graphene oxide. As part of the research, wood was impregnated with aqueous graphene oxide dispersion. Wood was impregnated using two methods: single vacuum and pressureless with ultrasound. Laser-assisted ionization spectroscopy (LIBS) was used to determine elements, mainly carbon, and to characterize differences in the elemental composition between the surface layers of wood impregnated with graphene oxide and native wood. Changes in the structure of polymers building wood tissue were analyzed using LIBS and FTIR spectrometry. The wood surface was also imaged using three microscopic techniques (stereomicroscope, confocal laser scanning microscope, and scanning electron microscopy). LIBS showed that graphene oxide was deposited on the surface of impregnated wood, and the intensity of carbon signals in wood impregnated with graphene oxide using vacuum and ultrasound differed. The content of carbon, magnesium, and oxygen elements in the surface layers of wood impregnated with graphene oxide using ultrasound was lower than in vacuum-impregnated wood. Analysis of FTIR spectra showed effective incorporation of graphene oxide into the surface layer of wood. Full article

In order to identify carcinoembryonic antigen (CEA) in serum samples, an innovative smartphone-based, label-free electrochemical immunosensor was created without the need for additional labels or markers. This technology presents a viable method for on-site cancer diagnostics. The novel smartphone-integrated, label-free immunosensing platform was constructed by nanostructured materials that utilize the layer-by-layer (LBL) assembly technique, allowing for meticulous control over the interface. Detection relies on direct interactions without extra tagging agents, where ordered graphene oxide (GO), carbon nanotubes (CNTs), and copper oxide nanoparticles (CuONPs) were sequentially deposited onto a screen-printed carbon electrode (SPCE), designated as CuONPs/CNTs/GO/SPCE. This significantly amplifies the electrochemical signal, allowing for the detection of low concentrations of target molecules of CEA. The LBL approach enables the precise construction of multi-layered structures on the sensor surface, enhancing their activity and optimizing the electrochemical performance for CEA detection. These nanostructured materials serve as efficient carriers to significantly increase the surface area, conductivity, and structural support for antibody loading, thus improving the sensitivity of detection. The detection of carcinoembryonic antigen (CEA) in this electrochemical immunosensing transducer is based on a decrease in the current response of the [Fe(CN)₆]^3−/4− redox probes, which occurs in proportion to the amount of the immunocomplex formed on the sensor surface. Under the optimized conditions, the immunosensor exhibited good detection of CEA with a linear range of 0.1–5.0 ng mL⁻¹ and a low detection limit of 0.08 ng mL⁻¹. This label-free detection approach, based on signal suppression due to immunocomplex formation, is highly sensitive and efficient for measuring CEA levels in serum samples, with higher recovery ranges of 101% to 112%, enabling early cancer diagnosis. The immunosensor was successfully applied to determine CEA in serum samples. This immunosensor has several advantages, including simple fabrication, portability, rapid analysis, high selectivity and sensitivity, and good reproducibility with long-term stability over 21 days. Therefore, it has the potential for point-of-care diagnosis of lung cancer. Full article

The growing demand for efficient energy storage systems, particularly in portable electronics and electric vehicles, has led to increased interest in supercapacitors, which offer high power density, rapid charge/discharge rates, and long cycle life. However, improving their energy density without compromising performance remains a challenge. In this study, we developed novel 3D-printed reduced graphene oxide (rGO) electrodes coated with polyaniline (PANI) to enhance their electrochemical properties. The rGO 3D-printed electrodes were fabricated using direct ink writing (DIW), which allowed precise control over thickness, ranging from 4 to 24 layers. A unique ink formulation was optimized for the printing process, consisting of rGO, cellulose acetate (CA) as a binder, and acetone as a solvent. The PANI coating was applied via chemical oxidative polymerization (COP) with up to five deposition cycles. Electrochemical testing, including cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS), revealed that 12-layer electrodes with three PANI deposition cycles achieved the highest areal capacitance of 84.32 mF/cm². While thicker electrodes (16 layers and beyond) experienced diminished performance due to ion diffusion limitations, the composite electrodes demonstrated excellent cycling stability, retaining over 80% of their initial capacitance after 1500 cycles. This work demonstrates the potential of 3D-printed PANI/rGO electrodes for scalable, high-performance supercapacitors with customizable architectures. Full article

High electrical conductivity and optical transparency make graphene a suitable candidate for photovoltaic-based power systems. In this study, we present the design and fabrication of an array of graphene-based Schottky junction solar cells. Using mainstream semiconductor manufacturing methods, we produced 96 solar cells from a single 100 mm diameter silicon wafer that was precoated with an oxide layer. The fabrication process involves removing the oxide layer over a select region, depositing metal contacts on both the oxide and bare silicon regions, and transferring large-area graphene onto the exposed silicon to create the photovoltaic interface. A single solar cell can provide up to 160 μA of short-circuit current and up to 0.42 V of open-circuit voltage. A series of solar cells are wired to recharge a 3 V battery intermittently, while the battery continuously powers a device. The solar cells and rechargeable battery together form a power system for any 3-volt low-power application. Full article

The accurate measurement of moisture content in pure gases and in gas mixtures, such as air, has great relevance in many industrial processes. In the present study, graphene oxide reduced through a mild alkaline treatment was used as a humidity sensing material to fabricate a flexible chemiresistive device operating at room temperature. The active layer was deposited by solution casting on a substrate of bimatted polyester, previously coated with inkjet-printed interdigitated electrodes made of silver. Structural investigations were performed by means of X-ray diffraction, Raman spectroscopy, and FTIR spectroscopy, while the optical properties were investigated using UV-VIS absorption and photoluminescence excitation spectroscopy. With increasing relative hu-midity from 0 to 80%, the electrical resistance decreased from about 1.4 GΩ to 2.5 MΩ. The ex-traordinarily large range of resistance values highlights the ultrahigh humidity sensitivity of re-duced graphene oxide, which acquires a fair amount of electrical conductivity after physisorption of water molecules but results in a highly resistive material in dry air. The high sensitivity at room temperature, the response’s repeatability, the wide relative humidity range detected, and the fast response time are the main advantages of the proposed humidity sensor, while the presence of some hysteresis, mainly at low relative humidity, and the recovery time need further improve-ment. Finally, the sensing mechanisms are briefly discussed. Full article

This study presents a novel approach for fabricating ZIF-8 membranes supported on α-alumina hollow fibers through the introduction of a graphene oxide (GO) gutter layer and the application of zinc oxide (ZnO) Atomic Layer Deposition (ALD). The method successfully addressed key challenges, including excessive precursor penetration and membrane thickness. The introduction of the GO layer and subsequent ZnO ALD treatment significantly reduced membrane thickness to approximately 300 nm and eliminated delamination issues between the GO layer and the alumina support. The optimized membranes demonstrated enhanced propylene permeance, with values approximately three times higher than those of membranes without GO, and achieved higher separation factors, indicating minimal inter-crystalline defects. Notably, the GO layer influenced the microstructure, leading to an increase in permeance with rising temperatures. These findings highlight the potential of this strategy for developing high-performance ZIF-8 membranes for gas separation applications. Full article

Photodetectors are of great interest in several technological applications thanks to their capability to convert an optical signal into an electrical one through light–matter interactions. In particular, broadband photodetectors based on graphene/silicon heterojunctions could be useful in multiple applications due to their compelling performances. Here, we present a 2D photodiode heterojunction based on a graphene single layer deposited on p-type and n-type Silicon substrates. We report on the electro-optical properties of the device that have been measured in dark and light conditions in a spectral range from 400 nm to 800 nm. The comparison of the device’s performance in terms of responsivity and rectification ratio is presented. Raman spectroscopy provides information on the graphene single layer’s quality and oxidation. The results showcase the importance of the doping of the silicon substrate to realize an efficient heterojunction that improves the photoresponse, reducing the dark current. Full article