Graphene Oxide Hybrid Materials Research Articles

Multi-compartmentalized electrochemical sensing platforms for monitoring cascade enzymatic reactions

Designing an electrochemical biosensor with the required features is a complex process involving multiple factors. For instance, nanocomposite materials used ensure the adaptation of the sensor to specific parameters on demand. But beyond making more versatile sensors, these materials likely offer excellent sensing platforms to mimic biological processes (e.g. cell communication) on the electrode surface. For this, developed methods are needed to integrate non-conductive nanoreactors for molecular communication into a biocompatible matrix on electrode surfaces with the request of spatially separated and controlled enzyme localization. Here, we present a novel reduced graphene oxide hybrid material to immobilize polymeric nanoreactors supported by an alginate network as a matrix on the electrode surface. The possibility of introducing cascade reactions in an electrochemical biosensor has the advantage of broadening the target substrates as well as their selectivity using enzymes in different nanocompartments (=compartmentalization). The polymeric vesicles allow the loading of enzymes or artificial enzymes, offering active center retention and long-term enzyme stability. Firstly, the inclusion of spatially separated polymeric active nanocompartments into the matrix on the electrode surface is used to monitor a simple enzyme reaction. However, the study’s accomplishment lies in its successful ability to monitor an enzyme cascade reaction, one producing and the other consuming hydrogen peroxide, hosting natural and artificial enzymes. This proof-of-concept generates an important contribution to the design of analytical platforms capable of detecting complex environments or even monitoring communication between cell-like structures, extremely useful for fields such as synthetic biology, biomimetics and advanced biosensors.

Nitrogen, sulfur coordinated metal complex and reduced graphene oxide hybrid materials as counter electrodes for application in dye-sensitized solar cells

Graphene, as one of the carbon-based materials, is considered to be a potential replacement for platinum and has been widely used as a counter electrode in dye-sensitized solar cells to achieve low-cost and high electrocatalytic materials. In this work, we synthesized a nitrogen-sulfur-coordinated iron complex as a source of heteroatoms, and prepared iron-nitrogen-sulfur co-doped reduced graphene oxide (FeNS-rGO) composite material by mixing with different mass ratios of graphene oxide (GO) and thermal annealing under nitrogen at 400 °C. The sintered GO was transformed into rGO, which increased the conductivity of materials, while the doping of nitrogen and sulfur atoms enhanced the carrier mobility and conductivity of the material. The distribution of Fe on graphene also improved the catalytic performance of material. FeNS-rGO (5:1), used as the CE in DSSC, showed superior reduction catalytic activity for I−/I3− compared to platinum and demonstrated an excellent power conversion efficiency of 8.17 %, which outperformed platinum. This proves that the graphene composite material doped with iron, nitrogen, and sulfur has excellent performance and can be used as a substitute for platinum.

Highly stable ammonium ion-selective electrodes based on one-pot synthesized gold nanoparticle-reduced graphene oxide as ion-to-electron transducers

An effective transducer for all-solid-state ion-selective electrodes (SC-ISEs) was developed based on gold nanoparticle-reduced graphene oxide (AuNP-rGO) hybrid material. The AuNP-rGO composite was synthesized via a simple, eco-friendly, and one-pot method with sodium citrate as the reducing agent and the stabilizer. The nanocomposite was deposited on the GC substrate via the drop-casting method and then covered with an ammonium ion-selective membrane (NH4+-ISM) to form the potentiometric electrode. The AuNP-rGO layer possessed a large surface area, high capacitance, and good hydrophobicity; thereby effectively enhancing the potential stability of the electrode without the formation of an aqueous layer. The electrode also exhibited a rapid potential response (<10 s) to NH4+ ions, an excellent Nernstian response with a slope of 56.94 (±1.57) mV/decade, a detection range of 10-5 − 10-2 M, and a detection limit of 3.80 × 10-6 M. The proposed electrode also exhibited outstanding properties including insensitivity to interferences (light, oxygen, carbon dioxide, and redox species), good reproducibility, and long operating life. The electrode has been successfully applied for NH4+ detection in real water samples, which makes it a promising alternative for developing effective and robust SC-ISEs.

Enhanced Electrochemical Ethanol Sensitivity on Ni/NiO‐rGO Hybrids Nanostructures at Room Temperature

AbstractHerein, we depict that the consequential nickel/nickel oxide‐reduced graphene oxide (Ni/NiO‐rGO) hybrid materials synthesized by sol‐gel approach can give as competent electrocatalyst for oxidative determination of ethanol in alkaline condition. Ni/NiO‐rGO based electrochemical sensor shows rapid and highly sensitive linear sweep voltametric (LSV) response to ethanol at an ultra‐low oxidation potential of 0.33 V vs. SCE. Moreover, the electrochemical sensor demonstrates highly stable (current and potential) also with low charge transfer resistance confirmed from chronoamperometic (i‐t) and electrochemical impedance spectroscopic (EIS) data respectively towards ethanol oxidation at Ni/NiO‐rGO hybrid interface confirms its acitivity over individuals i. e. Ni/NiO nanoparticles and rGO. Moreover, linear increase in current density upto 100 μM concentration of ethanol and for the scan rates in the range of 10–100 mV/s with positive shift in potential confirms ethanol oxidation is diffusion controlled process. The selective analysis of electrochemical response for ethanol in benadryl sample with same oxidation potential of ethanol beverages with enhanced ethanol oxidation potential for determination of ethanol concentration into benadryl sample analysis.

Rational synthesis of reduced graphene oxide hybrid nanocomposite with iron tungstate for selective detection of epinephrine in biological fluids

Hybrid nanocomposites made from metal tungstate and stacked graphene nanosheets have attracted the curiosity of researchers due to their high conductivity, strong electrochemical activity, and quick electrochemical transfer response. These properties prompted us to employ co-precipitation and sonochemical approaches to create low-cost iron tungstate (FeWO4)/reduced graphene oxide (rGO) hybrid material. The as-synthesized FeWO4/rGO nanocomposites (NCs) were evaluated for their physicochemical properties and structural and morphological aspects. A modified electrode composed of FeWO4/rGO NCs was utilized to detect epinephrine (Eph), a significant neurotransmitter and hormone associated with various human activities. The electrochemical behavior of Eph was quantified using cyclic voltammetry, and differential pulse voltammetry (DPV) on a FeWO4/rGO NCs modified electrode. According to the DPV study, Eph concentration was linearly distributed from 0.05 to 990.5 µM. For determining Eph, the sensor had a detection limit of 0.0073 µM and a sensitivity of 5.857 µAµM−1 cm−2. The sensor displayed excellent recovery results for the determination of Eph in the human urine and epinephrine pills real samples, revealing its excellent practicality.

Electrical Properties of Polyetherimide-Based Nanocomposites Filled with Reduced Graphene Oxide and Graphene Oxide-Barium Titanate-Based Hybrid Nanoparticles.

The electrical properties of nanocomposites based on polyetherimide (PEI) filled with reduced graphene oxide (rGO) and a graphene oxide hybrid material obtained from graphene oxide grafted with poly(monomethyl itaconate) (PMMI) modified with barium titanate nanoparticles (BTN) getting (GO-g-PMMI/BTN) were studied. The results indicated that the nanocomposite filled with GO-g-PMMI/BTN had almost the same electrical conductivity as PEI (1 × 10−11 S/cm). However, the nanocomposite containing 10 wt.% rGO and 10 wt.% GO-g-PMMI/BTN as fillers showed an electrical conductivity in the order of 1 × 10−7 S/cm. This electrical conductivity is higher than that obtained for nanocomposites filled with 10% rGO (1 × 10−8 S/cm). The combination of rGO and GO-g-PMMI/BTN as filler materials generates a synergistic effect within the polymeric matrix of the nanocomposite favoring the increase in the electrical conductivity of the system.

Capacitive Properties of Chlorine Doped Graphene Quantum Dots Anchored into Reduced Graphene Oxide

In this study, Cl-GQDs anchored into pure reduced graphene oxide (Cl-GQDs/rGO) hybrid materials were hydrothermally fabricated and characterized by various analyses. Meanwhile, P-GQDs, S-GQDs and N-GQDs were also fabricated and anchored into rGO as controls. The AFM images of Cl-GQDs, P-GQDs, N-GQDs and S-GQDs displayed the average height of 1–3 nm, 1–1.5 nm, 1.5–2.0 nm and 4.0–4.5 nm, respectively. Moreover, the absorbance and fluorescence spectra of Cl-GQDs were different from those of other doped graphene quantum dots. Cyclic voltammetry and galvanostatic charge-discharge curves were employed to analyze the capacitive performances of doped-GQDs/rGO. At the current density of 2 A g−1, the capacitance of Cl-GQDs/rGO achieved 316 F g−1, which was about 3 times, 2 times and 1.5 times as high as that of rGO, S or N-GQDs/rGO and P-GQDs/rGO, respectively. At the power density of 1.1−3.3 KW Kg−1, Cl-GQDs/rGO reached the energy density of 53.2 − 32.1 Wh Kg−1. Electrochemical impedance spectroscopy clearly indicated that Cl-GQDs could improve the conductivity of rGO in the electrochemical reaction, resulting in superior capacitive performances.

Synthesis of a novel fluorinated graphene oxide hybrid material based on poly(2,3,4,5,6-pentafluorostyrene) and its use as a filler for thermoplastic polyurethane film

In this study, graphene oxide (GO) was synthesized via modified Hummers method. The GO was grafted with poly(2,3,4,5,6-pentafluorostyrene) (PPFSGO) by surface initiated atom transfer radical polymerization (SI-ATRP). This material was used as a novel filler for thermoplastic polyurethane (TPU) to prepare composite films via solution casting method. FTIR, Raman and XRD spectroscopy analyses confirmed the formation of proposed hybrid structure. SEM analysis indicated that the GO layers of PPFSGO were exfoliated and decorated with weblike PPFS. Particularly, the contact angle measurements showed that the contact angle of TPU based composite films could be increased by 20% compared to bare TPU film with the incorporation of 10 wt% of PPFSGO while preserving thermal stability and electrically insulating properties. These results revealed that the herein proposed PPFSGO hybrid material is a promising candidate to adjust the wettability of TPU films without compatibility issues.

Preparation of Silver Decorated Reduced Graphene Oxide Nanohybrid for Effective Photocatalytic Degradation of Indigo Carmine Dye

Background: Even though silver decorated reduced graphene oxide (Ag-rGO) shows maximum absorptivity in the UV region, most of the research on the degradation of dyes using Ag-rGO is in the visible region. Therefore the present work focused on the photocatalytic degradation of indigo carmine (IC) dye in the presence of Ag-rGO as a catalyst by UV light irradiation. Methods: In this context, silver-decorated reduced graphene oxide hybrid material was fabricated and explored its potential for the photocatalytic degradation of aqueous IC solution in the UV region. The decoration of Ag nanoparticles on the surface of the rGO nanosheets is evidenced by TEM analysis. The extent of mineralization of the dye was measured by estimating chemical oxygen demand (COD) values before and after irradiation. Results: The synthesized Ag-rGO binary composites displayed excellent photocatalytic activity in 2 Χ 10-5 M IC concentration and 5mg catalyst loading. The optical absorption spectrum of Ag-rGO showed that the energy band-gap was found to be 2.27 eV, which is significantly smaller compared to the band-gap of GO. 5 mg of Ag-rGO was found to be an optimum quantity for the effective degradation of IC dye. The degradation rate increases with the decrease in the concentration of the dye at alkaline pH conditions. The photocatalytic efficiency was 92% for the second time. Conclusion: The impact of the enhanced reactive species generation was consistent with higher photocatalytic dye degradation. The photocatalytic mechanism has been proposed and the hydroxyl radical was found to be the reactive species responsible for the degradation of dye. The feasibility of reusing the photocatalyst showed that the photocatalytic efficiency was very effective for the second time.

Facile synthesis and antibacterial activity of silver nanoparticles-modified graphene oxide hybrid material: the assessment, utilization, and anti-virus potentiality

The present work reported the one-pot preparation of silver nanoparticles doped with graphene oxide (Ag@GO), using glucose as an eco-friendly reducing agent. The effects of synthesis conditions on the introduction of AgNPs onto graphene oxide sheets were confirmed by modern analytical techniques and antibacterial assays. Results showed that the Ag@GO-4 sample prepared with glucose:AgNO3:GO mass ratio of 1:1:1 at 60 °C for 60 min exhibited an appropriate one for further studies with AgNPs sizing of 16.66 ± 3.73 nm. The Ag@GO-4 effectively inhibited the development of S. enterica, P. aeruginosa, and S. aureus with the 50 % inhibitory concentration at 14.5, 0.9, and 6.8 μg/mL, respectively. The simultaneous effects of Ag@GO concentration, pH, interaction time, annealing temperature, and bacterial density on the antibacterial activity of Ag@GO-4 were also investigated by Plackett-Burman and Box-Behnken design. The optimal values deducing for Ag@GO-4 concentration, pH, and bacterial density were 40 μg/mL, 5.5, and 5.1 × 106 CFU/mL, respectively, which could impressively reach 99.99 % of S. enterica elimination in practice. The interaction time and annealing temperature implied a negligible effect on the antibacterial activity of Ag@GO-4. All results of the present study affirmed the future use of Ag@GO not only as an efficient antibacterial agent but also potentially as a novel anti-virus method of treatment.

Frontispiece: Near‐Equilibrium Growth of Chemically Stable Covalent Organic Framework/Graphene Oxide Hybrid Materials for the Hydrogen Evolution Reaction

Covalent Organic Frameworks Near-equilibrium growth of chemically stable covalent organic framework–graphene oxide hybrid materials for the hydrogen evolution reaction is reported in the Communication by Jianyi Chen, Jichen Dong, Yunqi Liu et al. (e202113067).

A Solid-Contact for Ammonium Ion-Selective Electrodes Based on Gold Nanoparticle-Reduced Graphene Oxide Hybrid Material: One-Pot Synthesis Using Sodium Citrate as Green Reductant and Stabilizer

A Solid-Contact for Ammonium Ion-Selective Electrodes Based on Gold Nanoparticle-Reduced Graphene Oxide Hybrid Material: One-Pot Synthesis Using Sodium Citrate as Green Reductant and Stabilizer

Organosilane-functionalized graphene oxide hybrid material: Efficient adsorbent for heavy metal ions in drinking water

Organosilane-functionalized and chemically activated graphene-supported Schiff base ligand were synthesized and characterized with XRD, SEM, EDX, TEM, UV–vis, FT-IR, and TG/DTA techniques. Graphene oxide (GO) obtained with the route of Hummer’s method was reacted with 3-(trimethoxysilyl)propylamine, then, the organosilane functionalized and amine-activated-GO was reacted with 3,5-di-tert-butylsalicylaldehyde obtained the hybrid material containing azomethine group on GO surface. The material was used as an adsorbent in order to remove cobalt(II) and zinc(II) ions in drinking water and standard solutions. The adsorption capacity of the material to cobalt(II) and zinc(II) ions were investigated by using batch method. The effect of pH, contact time, temperature, and concentration on the adsorption capacity of the material was also investigated. The enrichment factors were calculated as 441 and 675 for zinc(II) and cobalt(II), respectively. The recovery performance of the material was determined in 98.65–101.75% and 98.55–104.0% range for zinc(II) and cobalt(II) ions, respectively.

Direct observation of adsorption and desorption of ds-DNA on graphene oxide and graphene oxide-gold nanoparticle hybrid material: A kineto-mechanistic investigation

Graphene oxide (GO) and its functional derivatives have found tremendous application in the development of biosensors for the detection of nucleic acid hybridization. In this work, we have systematically investigated the adsorption mechanism of oligonucleotides on both GO and graphene oxide-gold nanoparticle (GO-AuNP) hybrid surface and also recovered the adsorbed DNA by applying complementary strands by employing ensemble and single-molecule fluorescence methods. A remarkable observation about the adsorption and desorption mechanism of double-stranded DNA (ds-DNA) on graphene oxide (GO) and GO-AuNP surface has been monitored. The efficiency and rate of adsorption are found to be higher for the GO-AuNP hybrid material compared to that of only GO. The results from the single-molecule-FRET (sm-FRET) indicate that the adsorption of the ds-DNA on the GO-AuNP hybrid material takes place by completely unzipping the strands, i.e. the DNA adsorbs as single-stranded DNA. However, no such clear evidence was observed for the GO. The sm-FRET results reveal the DNA hybridization mechanism to happen “in situ”, i.e. hybridization between the probe and target DNA to form a ds-DNA and desorption thereafter from the GO surface takes place simultaneously. These results also demonstrate that the electrostatic interaction between DNA and GO is of little importance to the overall theory of interaction. This investigation improves the fundamental understanding of DNA hybridization dynamics on GO surface opening new windows in the field of biophysics, sensing, and therapeutic application.

Enhanced blue photoluminescence of cobalt-reduced graphene oxide hybrid material and observation of rare plasmonic response by tailoring morphology

Enhanced blue photoluminescence of cobalt-reduced graphene oxide hybrid material and observation of rare plasmonic response by tailoring morphology

Covalently bonded boron nitride quantum dot and reduced graphene oxide composite electrode for highly efficient supercapacitors

This study investigates the synthesis and application of boron nitride quantum dot (BNQD) covalently bonded reduced graphene oxide (rGO) hybrid materials as a novel electrode material for supercapacitors. Because of the p-doping as well as the enhanced hydrophilicity and interfacial bonding force enabled by the hybridization of amine-functionalized boron nitride quantum dot (A-BNQD) with rGO via the chemical coupling reaction, the A-BNQD/rGO shows improved charge carrier density, wettability of electrolyte, and durability. As a result of the synergistic effects, the A-BNQD/rGO as a supercapacitor electrode shows much higher specific capacitance compared to those of rGO and raw BNQD/rGO at a current density of 1 A g−1. Further, the A-BNQD/rGO shows high cycling stability, maintaining almost 94.38%, even after 10,000 cycles due to the enhanced interfacial bonding force between the A-BNQD and rGO. Besides, the fabricated symmetric supercapacitor exhibits high specific capacitance (90 F g−1@1 A g−1), an energy density (12.5 Wh kg−1@0.5 kW kg−1), and good cycling stability. This result suggested that the fabricated A-BNQD/rGO has great potential as electrode materials for high-performance supercapacitors.

Hydrogen photoproduction on TiO2-reduced graphene oxide hybrid materials from water-ethanol mixture

Titanium dioxide mixed with reduced graphene oxide (rGO) has been tested in the photoproduction of hydrogen using UV light from water-ethanol combination in gas phase. The presence of the reduced graphene oxide in TiO2/rGO nanocomposites affects the physicochemical properties of hybrid materials, thus enhancing the photocatalytic activity. The obtained catalysts have been characterized for physical-chemical properties using X-ray diffraction (XRD), UV–vis spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM)/high-resolution transmission electron microscopy (HRTEM), and Brauner Emmett Teller (BET). The best photocatalyst has been obtained by mixing anatase and rGO (10 wt%) after calcination at 700 °C. This TiO2-rGO composite exhibited the highest performance with a hydrogen photogeneration rate of 9.5 mmol h−1 g−1.

Eco-friendly and bio-waste based hydroxyapatite/reduced graphene oxide hybrid material for synergic electrocatalytic detection of dopamine and study of its simultaneous performance with acetaminophen and uric acid

Herein, we report an innovative fabrication of agglomerate eco-friendly and bio-waste based hydroxyapatite/reduced graphene oxide hybrid material modified carbon paste electrode (BHA/rGO/CPE) for the detection of dopamine (DA). In the present exertion, environmental bio-waste eggshells were utilized to synthesize the hydroxyapatite (BHA) material. Further, BHA/rGO hybrid material was synthesized via a simple disperser assisted sonochemical approach and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), High-resolution transmission electron microscopy (HRTEM) with energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analysis. Under the optimal conditions, the electrochemical results were attained by the cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. BHA/rGO/CPE displayed good sensitivity over the other electrodes. The enhanced results were due to the combination of the multi-adsorption capability of BHA and superior conductivity nature of rGO. The limit of detection and quantification of dopamine were found to be as 0.39, 1.32 µM and 0.63, 2.10 µM respectively, for lower (5 to 100 µM) and higher (120 to 310 µM) linear dynamic ranges. BHA/rGO/CPE was also demonstrated for the simultaneous determination of dopamine (DA), acetaminophen (AC) and uric acid (UA) with no interference among the analyte molecules. Further, the discussed sensor had great potential application in determining DA in real sample analysis.

FeNb2O6/reduced graphene oxide composites with intercalation pseudo-capacitance enabling ultrahigh energy density for lithium-ion capacitors.

Lithium-ion capacitors (LICs), which combine the characteristics of lithium-ion batteries and supercapacitors, have been well studied recently. Extensive efforts are devoted to developing fast Li+ insertion/deintercalation anode materials to overcome the discrepancy in kinetics between battery-type anodes and capacitive cathodes. Herein, we design a FeNb2O6/reduced graphene oxide (FNO/rGO) hybrid material as a fast-charge anode that provides a solution to the aforementioned issue. The synergetic combination of FeNb2O6, whose unique structure promotes fast electron transport, and highly conductive graphene shortens the Li+ diffusion pathways and enhances structural stability, leading to excellent electrochemical performance of the FNO/rGO anode, including a high capacity (770 mA h g−1 at 0.05 A g−1) and long cycle stability (95.3% capacitance retention after 500 cycles). Furthermore, the FNO/rGO//ACs LIC achieves an ultrahigh energy density of 135.6 W h kg−1 (at 2000 W kg−1) with a wide working potential window from 0.01 to 4 V and remarkable cycling performance (88.5% capacity retention after 5000 cycles at 2 A g−1).

Tuning the defects in MoS2/reduced graphene oxide 2D hybrid materials for optimizing battery performance

This work reports the Li-ion and Zn-ion storage properties of a set of MoS2/reduced graphene oxide (rGO) hybrid materials whose defect density is tuned by controlling the annealing temperature, which is critical in improving Zn-ion storage.