Graphene Oxide Research Articles

Hierarchical Porous Aggregate-Enabled Chromatography-Inspired Single-Sensor E-Nose for Volatile Monitoring.

Monitoring volatile organic compounds (VOCs) is crucial for ensuring safety and health. In this study, we introduce a strategy to engineer a chromatography-inspired single-sensor (CISS) e-nose tailored for VOC monitoring. This approach overcomes the limitations of traditional methodologies and conventional e-noses. A hierarchical porous multicomponent aggregate, named CuP@G, was initially developed as the sole sensor material. This aggregate integrates a Cu2+-polydopamine (CuP) network with reduced graphene oxide, enhancing its chemoresistive properties. Using laser processing, we fabricated a grooved laser-induced graphene interdigitated electrode that is loaded with CuP@G ink and subsequently integrated into a compact laser-engraved microchamber. This process results in the production of the CISS e-nose. Notably, this e-nose enables swift, reversible, and precise detection of various VOCs using a time-space-resolved methodology. The developed module, known for its affordability and portability, is especially suitable for the point-of-care testing (POCT) of VOCs. Consequently, our research advances the development of streamlined cost-effective e-noses that are essential for proficient VOC monitoring.

Enhanced breakdown strength and reduced polarization hysteresis in relaxor ferroelectric polymers with increased gamma phase content for energy storage capacitors

Polymer dielectric energy storage capacitors play a vital role in modern electronic and electrical power systems, particularly in high-voltage environments. However, achieving both high energy density and charge–discharge efficiency presents a significant challenge for next-generation applications that demand miniaturization and compact design. In this study, we present relaxor ferroelectric terpolymers with an increased gamma (γ)-phase content, prepared through a facile and scalable interfacial engineering approach that incorporates ultra-low amounts of graphene oxide. The γ-phase crystals in the terpolymer reduce hysteresis losses and generate numerous deep traps, resulting in enhanced performance. These terpolymers achieve a high energy density of up to 15.2 J/cm3 and an improved breakdown strength of 562 MV/m, representing enhancements of 62% and 39.8%, respectively, compared to the pristine terpolymer. The results suggest that tuning the phase structure of relaxor ferroelectric terpolymers offers a pathway to developing ferroelectric polymers with enhanced energy density and charge–discharge efficiency for energy storage capacitors.

The Proximal Protonation Source in Cu-NHx-C Single Atom Catalysts Selectively Boosts CO2 to Methane Electroreduction.

Regulating the coordination environment of active sites has proved powerful for tapping into their catalytic activity and selectivity in homogeneous catalysis, yet the heterogeneous nature of copper single-atom catalysts (SACs) makes it challenging. This work reports a bottom-up approach to construct a SAC (rGO@Cu-N(Hx)-C) by inlaying preformed amine coordinated Cu2+ units into reduced graphene oxide (rGO), permitting molecular level revelation on how the proximal N-site functional groups (N-H or N-CH3) impact on the carbon dioxide reduction reaction (CO2RR). It is demonstrated that the N-H moiety of rGO@Cu-NHx-C can serve as an in-situ protonation agent to accelerate the CO2-to-methane reduction kinetics, delivering a methane current density (163 mA/cm2) 2.42-times that with the -CH3 substituted counterpart rGO@Cu-N-C. Operando spectroscopic studies and theoretical calculations elucidate that the high methane faradaic efficiency (77.1%) achieved here is enabled by opening up the energetically favorable formyl pathway (*OCHO pathway) against the traditional *CO pathway that normally leads to various CO2RR products other than methane. Our strategy sets the stage to precisely modulate single-atom catalysts for efficient and selective electrochemical CO2 reduction.

Ultrahigh Fe3O4 Magnetic Crystals Loading onto Crumpled Spherical Reduced Graphene Oxide for Superb Electromagnetic Absorption in the C and X Frequency Bands

Ultrahigh Fe₃O₄ Magnetic Crystals Loading onto Crumpled Spherical Reduced Graphene Oxide for Superb Electromagnetic Absorption in the C and X Frequency Bands

Thermophysical analysis of time-dependent magnetized Casson hybrid nanofluid flow (Cu + GO/Kerosene Oil) using Darcy-Forchheimer and thermal radiative models for industrial cooling applications

This paper presents an in-depth analytical investigation into the time-dependent flow of a Casson hybrid nanofluid over a radially stretching sheet. The study introduces the effects of magnetic fields and thermal radiation, along with velocity and thermal slip, to model real-world systems for enhancing heat transfer in critical industrial applications. The hybrid nanofluid consists of three nanoparticles—Copper and Graphene Oxide—suspended in Kerosene Oil, selected for their stable and superior thermal properties. The theory of Darcy-Forchheimer, along with the suction and injection effect, is applied to refine the flow behaviour and enhance heat transfer efficiency. The governing nonlinear equations are solved using the Homotopy Analysis Method to provide a robust framework for solution accuracy. The graphical and tabulated results demonstrated that hybrid nanofluid outperforms mono and Casson hybrid nanofluids. The result shows that, at a nanoparticle volume concentration of 0.03, the Casson hybrid nanofluid showed a remarkable 19.99% increase in heat transfer, compared to 14.80% for simple nanofluid. The magnetic parameter and thermal radiation parameter further amplify thermal conductivity. This research provided a critical insight into optimizing thermal management systems for advanced engineering applications, positioning hybrid nanofluid as highly effective solutions for next-generation cooling technologies.

Graphene Oxide‐Assisted Tapered Microfiber Super‐Sensor for Rapid Detection of Mycobacterium tuberculosis Antigens

ABSTRACTTuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is one of the most widespread infectious diseases, with nearly 2 billion people infected globally. We present an innovative approach for the real‐time detection of TB antigens Mpt64 and Ag85B using DNA aptamers in combination with a graphene oxide (GO)‐assisted optical microfiber super‐sensor. The high surface‐to‐volume ratio and superior properties of the GO layer significantly enhance the microfiber's fixation capabilities. To validate the clinical applicability of this sensing method, we employed the optical sensor to successfully detect Mpt64 and Ag85B in serum samples within 10 s, achieving limits of detection of 4.23 × 10⁻²⁰ M and 3.11 × 10⁻¹⁹ M, respectively. Due to the high conservation of Mpt64 and Ag85B in human and bovine MTB strains, our detection system can be used to identify MTB in both humans and bovine. These results demonstrate the sensor's high sensitivity for quantifying MTB particles, enabling rapid identification of infected individuals or bovine. Overall, the optical microfiber sensor system offers a promising platform for diagnosing MTB due to its straightforward detection scheme and potential for miniaturization.

Wireless Flexible Actuator Photoelectric Synergistically Driven for Environment Adaptability Crawling Robots.

Wirelessly driven flexible actuators are crucial to the development of flexible robotic crawling. However, great challenges still remain for the crawling of flexible actuators in complex environments. Herein, we reported a wireless flexible actuator synergistically driven by wireless power transmission (WPT) technology and near-infrared (NIR) light, which consists of a poly(dimethylsiloxane)-graphene oxide (PDMS-GO) composite layer, eutectic gallium-indium alloy (EGaIn), a PDMS layer, and a polyimide (PI) layer. By optimizing the parameters of EGaIn and the concentration of the PDMS-GO composite film, the actuator has excellent bending ability and blocking force under different conditions driven by photoelectronic synergy. In addition, we fabricated a flexible crawling robot with high environmental adaptability by adding crawling structures at both ends of the actuator, which causes a discrepancy in friction between the front and rear feet. The flexible crawling robot has high stability, large deformation, and excellent crawling ability for wirelessly crawling on a plane, slope, and plane with different roughnesses. This work provides an idea for the application of wireless robots in complex environments.

Polyaniline/Reduced Graphene Oxide Composite as an Electrode for Symmetric and Asymmetric Supercapacitors

ABSTRACTPolyaniline‐based composites with reduced graphene oxide (rGO) were synthesized using chemical polymerization. Characterization techniques, including X‐ray diffraction (XRD), ultraviolet–visible (UV–visible) absorption spectroscopy, Fourier transform infrared (FTIR), and Raman spectroscopy, confirmed that both polyaniline (Pani) and the Pani/rGO composite were in the emeraldine salt state. The synergistic effect of Pani and rGO increases the polaron band and improves the electrical conductivity, which is confirmed by spectroscopic analysis. Scanning electron microscopy revealed that Pani had a granular morphology, whereas the Pani/rGO composite had a layered morphology. This layered morphology indicates that adding rGO can enhance the conductivity and electrochemical activity. The electrochemical studies of the Pani/rGO composite electrode showed a specific capacitance of 261 F g−1 at a current density of 2.4 A g−1. The electrochemical performance of the Pani/rGO composites for energy storage devices was examined via two‐electrode cell assembly. Pani/rGO was utilized as a cathode, whereas various carbon materials (CNFs, MWCNTs, AC) were used as anodes. A maximum energy density of 7.9 Wh kg−1 at a power density of 325 W kg−1 was observed in the Pani/rGO//PMAC asymmetric supercapacitor at a voltage of 1.4 V. The electrochemical performance results show that the Pani/rGO composite is an efficient supercapacitor electrode material.

Properties of poly(2-ethyl aniline)/graphene oxide (PEAn/GO) nanocomposites: influence of a synthesis method and polymerization time

Properties of poly(2-ethyl aniline)/graphene oxide (PEAn/GO) nanocomposites: influence of a synthesis method and polymerization time

Manufacture of 3D Compact Graphene Oxide Macrostructures

AbstractGraphene oxide (GO) is an important candidate material in the 2D‐material family. A single GO nanosheet comprises a one‐atom‐thick graphene sheet with oxygen‐containing functional groups. The interaction of oxygen groups on GO can help assemble GO nanosheets into macroscopic structures as flat membranes or nonplanar 3D structures. The manufacturing of 3D GO‐based macrostructures is of great interest as many applications require nonplanar structures, but current reviews on fabricating 3D GO‐based macrostructures with compact morphology are limited. This article reviews available methods to manufacture 3D GO‐based compact macrostructures, including molding, origami and kirigami, stimuli‐responsive deformation, and 3D printing. With these methods, the manufactured 3D structures have compact layered morphology under scanning electron microscopy. The compact morphology makes the GO‐based structures achieve high mechanical stiffness and strength to satisfy applications that need excellent mechanical properties. These methods have their advantages and drawbacks, so it is needed to select them carefully for specific applications. The development of processing methods to manufacture 3D macrostructures will enable GO‐based materials to achieve wide real‐life applications.

Quasi-vertically asymmetric channels of graphene oxide membrane for ultrafast ion sieving

The high performance of two-dimensional (2D) channel membranes is generally achieved by preparing ultrathin or forming short channels with less tortuous transport through self-assembly of small flakes, demonstrating potential for highly efficient water desalination and purification, gas and ion separation, and organic solvent waste treatment. Here, we report the construction of vertical channels in graphene oxide (GO) membrane based on a substrate template with asymmetric pores. The membranes achieved water permeance of 2647 L m−2 h−1 bar−1 while still maintaining an ultrahigh rejection rate of 99.9% for heavy metal ions, which is superior to the state-of-the-art 2D membranes reported. Furthermore, the membranes exhibited excellent stability during long-term filtration experiments for at least 48 h, as well as resistance to ultrasonic treatment for over 100 minutes. The vertical channels possess very short pathway for almost direct water transport and a highly effective channel area, meanwhile the asymmetric porous template enhances the packing of the inserted GO nanosheets to avoid the swelling effect of membrane. Our work provides a simple way to fabricate vertical channels of 2D nanofiltration membranes with high water purification performance.

Facile one-pot green synthesis, antioxidant and antimicrobial activities of 7-(substituted phenyl)-7,11-dihydro-6H,8H-chromeno[3′,4′:5,6]pyrano[2,3-d]pyrimidine-6,8,10(9H)-trione derivatives

The work aims to develop a simple and efficient protocol for one-pot three-component synthesis to produce a series of poly functionalized 7-(substituted phenyl)-7,11-dihydro-6H,8H-chromeno[3′,4′:5,6]pyrano[2,3-d]pyrimidine-6,8,10(9H)-trione derivatives using Sulfonated reduced graphene oxide (rGO-SO3H) as an efficient catalyst via one-pot multicomponent reaction of 4-hydroxycoumarin, aromatic aldehydes and barbituric acid under microwave irradiation and solvent-free conditions in good to excellent yields. The reported protocol is metal-free, highly atom-economic, better yielding in quick reaction time, simple to operate and eco-friendly with reaction conditions comparatively milder. Use of low-cost acidic catalyst under neat conditions makes the reaction an environmentally benign protocol. Additionally, the compounds were screened for their free radical scavenging, antibacterial and antifungal activities which showed good activities when compared than that of standard drugs.

Bio-inspired preparation of Ag NPs, rGO, and Ag/rGO nanocomposites for acoustical, antioxidant, and plant growth regulatory studies

Acoustical properties are essential for understanding the molecular interactions in fluids, as they influence the physicochemical behavior of liquids and determine their suitability for diverse applications. This study investigated the acoustical parameters of silver nanoparticles (Ag NPs), reduced graphene oxide (rGO), and Ag/rGO nanocomposite nanofluids at varying concentrations. Ag NPs and Ag/rGO nanocomposites were synthesized via a Bos taurus indicus (BTI) metabolic waste-assisted method and characterized using advanced techniques, including XRD, TEM, Raman, DLS, zeta potential, and XPS. The synthesized nanocomposites were evaluated for their acoustical, antioxidant, and plant growth-regulatory properties. Acoustical analysis revealed a linear relationship between the nanofluid concentration and density, with key parameters such as adiabatic compressibility, apparent molar compressibility, and apparent molar volume increase at lower concentrations. Irregular changes in ultrasonic velocity and other parameters at 0.025 mol/dm3 suggest unique nanoparticle-solvent interactions. The Ag/rGO nanocomposites exhibited superior antioxidative potential compared to Ag NPs, with DPPH scavenging activity reaching 65.69% and ABTS scavenging activity reaching 65.01% at 100 µg/mL. Plant growth studies have demonstrated enhanced germination rates (100% in spinach and 40% in fenugreek) and improved root and shoot elongation at 0.0025–0.005 mol/dm3. This study bridges the gap in understanding the acoustical and multifunctional properties of nanocomposites for biomedical, agricultural, and environmental applications.

Mechanism Study of Combustion Dynamics of GO@CL-20 Composite

The objective of this study was to investigate the distribution of pyrolysis products and the chemical reaction kinetics of a novel composite, GO@CL-20. The GO@CL-20 composite powder was synthesized using a solvent–non-solvent method. The thermal decomposition process of GO@CL-20 was analyzed through thermogravimetric differential scanning calorimetry (TG-DSC). The results indicate that the incorporation of graphene oxide (GO) reduces the activation energy of the sample, thereby catalyzing the thermal decomposition process of the complex. Subsequently, single pulse shock tube experiments were conducted to assess ignition delay time distribution, from which corresponding data on pyrolysis product distribution for GO@CL-20 were obtained. The findings regarding ignition delay times demonstrate that adding GO decreases the energy within the complex system and mitigates its reactivity, consequently prolonging ignition delay times. An important carbon and nitrogen molecule, C2N2, was identified in the pyrolysis product distribution; notably, its yield increased progressively with higher concentrations of GO. Finally, mass transfer characteristics and sensitivity analyses for GO@CL-20 samples were performed using CHEMKIN software to preliminarily determine pyrolysis reaction pathways. The results reveal that incorporating GO can significantly alter the thermal decomposition behavior of the entire system; moreover, C2N2 exhibits a high cleavage rate along this reaction pathway—findings that align well with experimental observations. This study aims to enhance understanding of CL-20 and GO reaction kinetics—materials with extensive applications in military operations as well as aviation and aerospace—and provides valuable insights for propellant development.

The Graphene Oxide/Gold Nanoparticles Hybrid Layers for Hydrogen Peroxide Sensing—Effect of the Nanoparticles Shape and Importance of the Graphene Oxide Defects for the Sensitivity

Graphene oxide (GO) and reduced graphene oxides (RGOs) show intrinsic electrocatalytic activity towards the electrocatalytic reduction of H2O2. Combining these materials with gold nanoparticles results in highly sensitive electrodes, with sensitivity in the nanomolar range because the electrocatalytic properties of GO and nanoparticles are synergistically enhanced. Understanding the factors influencing such synergy is crucial to designing novel catalytically active materials. In this contribution, we study gold nanostructures having shapes of nanospheres (AuNSs), nanourchins (AuNUs), and nanobowls (AuNBs) combined with GO or electrochemically reduced graphene oxide (ERGO). We investigate the amperometric responses of the hybrid layers to H2O2. The AuNUs show the highest sensitivity compared to AuNBs and AuNSs. All materials are characterized by electron microscopy and Raman spectroscopy. Raman spectra are deconvoluted by fitting them with five components in th e1000–1800 cm−1 range (D*, D, D”, G, and D′). The interaction between nanoparticles and GO is visualized by the relative intensities of Raman bands (ID/IG) and other parameters in the Raman spectra, like various D”, D* band positions and intensities. The ID/IG parameter is linearly correlated with the sensitivity (R2 = 0.97), suggesting that defects in the graphene structure are significant factors influencing the electrocatalytic H2O2 reduction.

Enhancing early breast cancer detection with APE1-triggered oligonucleotide probes and graphene oxide: The impact of variable AP site modification on sensitivity and specificity.

There is a critical need for inclusive diagnostic platforms to enhance the accuracy of early breast cancer detection. Dysregulated microRNA-1246 (miR-1246), closely linked to the disease progression and recurrence, has emerged as a promising diagnostic and prognostic biomarker for BC. However, achieving simple, rapid, and ultrasensitive quantification of serum miRNAs remains significant challenge. In this study, we present an innovative detection platform triggered by endogenous DNA repair enzyme apurinic/apyrimidinic endonuclease 1 (APE1). This platform utilizes an oligonucleotide probe with variable modified AP sites (denoted as AOP) coupled with graphene oxide (GO) for quantifying miR-1246. Our in vitro experiments reveal that the proposed method employing the AOP2 probe with two AP sites exhibits exceptional selectivity and sensitivity. The method achieves a detection limit as low as 2.3 pM towards miR-1246, which is approximately 260-fold more sensitive than the enzyme-free system. RT-qPCR experiments further validate the accuracy and practicability of the AOP2-based platform. In clinical trials, our platform has successfully differentiated between BC patients and normal healthy controls. In conclusion, we have established an integrated biosensing technology for PCR-free, non-invasive liquid biopsies of miR-1246, offering a promising approach for BC diagnosis.

Approaches for the measurement of lateral dimensions of graphene oxide flakes using scanning electron microscopy

Abstract There is a practical need, especially from the industrial community, to accurately measure the size and shape of graphene oxide (GO) flakes of commercial origin, in a reliable, simple, and unambiguous way. The sample preparation is a decisive step to obtain a homogeneous distribution of flakes on a substrate, which is suitable for image analysis. A certain level of inhomogeneity was still found but could be accepted for the purpose of this lateral size measurement study. A measurement procedure for Scanning Electron Microscopy (SEM) including sample preparation, measurement, image analysis and reporting was developed and validated to be applied for the lateral size analysis of “real-world” 2D flakes. Samples were produced for analysis by drop casting GO dispersions onto Si/SiO2 substrates. After SEM imaging, the images were analysed using two approaches to derive size and shape parameters. The influence of different operators has been evaluated. A maximum difference of 10% for the size descriptor and 2% for shape descriptor was found for both image analysis approaches when different samples of the same source material are measured and analysed by the same operator, hence indicating variability caused by sample preparation and analysing different sample areas. When different laboratories/operators perform the image analysis on exactly the same images and same flakes, the deviation found for the size descriptor is 2% and 4.6% corresponding to the two approaches applied, while no difference in the shape descriptor is observed.

AuNPs/GO/Pt microneedle electrochemical sensor for in situ monitoring of hydrogen peroxide in tomato stems in response towounding stimulation.

Hydrogen peroxide (H2O2) is a critical signaling molecule with significant roles in various physiological processes in plants. Understanding its regulation through in situ monitoring could offer deeper insights into plant responses and stress mechanisms. In this study, we developed a microneedle electrochemical sensor to monitor H2O2 in situ, offering deeper insights into plant stress responses. The sensor features a platinum wire (100µm diameter) modified with graphene oxide (GO) and gold nanoparticles (AuNPs) as the working electrode, an Ag/AgCl wire (100µm diameter) as the reference electrode, and an untreated platinum wire (100µm diameter) as the counter electrode. This innovative design enhances sensitivity and selectivity through the high catalytic activity of AuNPs, increased surface area from GO, and the superior conductivity of platinum. Operating at a low potential of -0.2V to minimize interference, the sensor detects H2O2 concentrations from 10 to 1000µM with high accuracy. In situ monitoring of H2O2 dynamics in tomato stems under the wounding stimulation reveals that H2O2 concentration increases as the sensor approaches the wound site, indicating localized production and transport of H2O2. This approach not only improves H2O2 monitoring in plant systems but also paves the way for exploring its generation, transport, and elimination mechanisms.

Defects vibrations engineering for enhancing interfacial thermal transport in polymer composites.

To push upper boundaries of thermal conductivity in polymer composites, understanding of thermal transport mechanisms is crucial. Despite extensive simulations, systematic experimental investigation on thermal transport in polymer composites is limited. To better understand thermal transport processes, we design polymer composites with perfect fillers (graphite) and defective fillers (graphite oxide), using polyvinyl alcohol (PVA) as a matrix model. Measured thermal conductivities of ~1.38 ± 0.22 W m-1 K-1 in PVA/defective filler composites is higher than those of ~0.86 ± 0.21 W m-1 K-1 in PVA/perfect filler composites, while measured thermal conductivities in defective fillers are lower than those of perfect fillers. We identify how thermal transport occurs across heterogeneous interfaces. Thermal transport measurements, neutron scattering, quantum mechanical modeling, and molecular dynamics simulations reveal that vibrational coupling between PVA and defective fillers at PVA/filler interfaces enhances thermal conductivity, suggesting that defects in polymer composites improve thermal transport by promoting this vibrational coupling.

Bio-waste derived reduced graphene oxide (rGO) decorated Cr (III) doped α-Fe2O3 nanocomposite for selective ppm-level acetone sensing at room temperature: Potential approach towards non-invasive diagnosis of diabetic biomarker

Reduced graphene oxide (rGO) was synthesized via reduction of graphitized household tea-waste utilizing neem leaves extract. The synergistic effect of rGO decoration and Cr3+ doping within pristine Fe2O3 enhanced surface adsorption property, defect density, and oxygen vacancies, facilitating the detection of ppm-levels (1 to 10 ppm) acetone at room temperature. Noticeably, the formation of ‘inversion space-charge-layer’ on sensing material surface at lower operating temperature resulted p-type sensing response using n-type nanomaterial that was transformed to n-type response when the operating temperature was elevated. The maximum sensing response (Rg/Ra) ~ 6.8 towards ~ 10 ppm acetone was obtained from optimized rGO decorated Cr3+ doped Fe2O3 sensor (FC3R3) at ambient condition. This sensor also revealed a rapid response/recovery time (~ 10 s/ ~ 10 s) and was able to detect as low as ~ 1 ppm acetone. The sensor exhibited improved selectivity towards acetone over other interfering VOCs, attributed to significant dipole moment, low bond dissociation energy, and strong affinity of acetone towards surface-adsorbed oxygenated ions. Notably, the sensor showed negligible deterioration in sensing performance even after ~ 150 days. Furthermore, this sensor was capable to differentiate between acetone concentration in breath sample of healthy and diabetic person for non-invasive diabetes detection.