Reduced Graphene Oxide Nanosheets Research Articles

Cobalt(ii) Schiff base chemically grafted onto magnetic amino-functionalized reduced graphene oxide nanosheets for highly rapid and selective removal of methyl orange

A magnetic graphene oxide functionalized with a Co(ii) Schiff base complex (Co(SB)-rGO/ZnFe2O4) was synthesized and applied as an ultrafast adsorbent to remove anionic organic dyes from water.

Antibacterial effect of ciprofloxacin loaded reduced graphene oxide nanosheets against Pseudomonas aeruginosa strain

• Combination of ciprofloxacin and reduced graphene oxide creates a drug composite. • This nanocomposite has sheet like structure, high zeta potential and high surface area. • The scanning electron microscope images confirm the rupture of the bacterial cells under the effect of composite. • AFM and optical microscope images show the visible significant reduction of biofilm of P. aeruginosa by the drug composite.

Pt21(C4O4SH5)21 clusters: atomically precise synthesis and enhanced electrocatalytic activity for hydrogen generation

How to effectively enhance the catalytic performance and simultaneously reduce the usage of Pt-based catalysts is always the goal of catalyst design for electrochemical energy devices. Platinum nanoclusters (Pt NCs) have aroused massive concerns in recent years because of the excellent activity of Pt-based materials themselves and the unique physical and chemical properties of nanoclusters. However, the studies on the synthesis, properties and applications of Pt NCs have been rarely reported. Here, we report a simple avenue to synthesize Pt nanoclusters through using K2PtCl4 as precursor and mercaptosuccinic acid (MSA) as not only ligand but also the reducing agent at the room temperature. Based on the matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS), the obtained Pt NCs have the composition of Pt21(C4O4SH5)21. By loading the Pt NCs on reduced graphene oxide nanosheets (rGO) and the following removal of MSA ligands upon annealing treatment, the obtained surface-clean Pt NCs/rGO exhibits excellent hydrogen evolution reaction (HER) catalytic performance and superior stability with Pt loading as low as 0.8 wt%. Especially, the HER mass catalytic activity of the Pt NCs/rGO is much higher than that of the 20.0 wt% commercial Pt/C catalyst. Meanwhile, this kind of cluster catalyst also shows large exchange current density (574 µA•cm−2) and high turn-over frequency (1.19 s−1). The experimental result in this work clearly indicates that Pt catalyst on cluster scale can obviously improve the catalytic performance. Therefore, this study provides an effective avenue to enhance the utilization of noble metals and to develop high-performance and cost-effective catalysts.

Electrical Cartridge Sensor Enables Reliable and Direct Identification of MicroRNAs in Urine of Patients.

Urinary miRNAs are biomarkers that demonstrate considerable promise for the noninvasive diagnosis and prognosis of diseases. However, because of background noise resulting from complex physiological features of urine, instability of miRNAs, and their low concentration, accurate monitoring of miRNAs in urine is challenging. To address these limitations, we developed a urine-based disposable and switchable electrical sensor that enables reliable and direct identification of miRNAs in patient urine. The proposed sensing platform combining disposable sensor chips composed of a reduced graphene oxide nanosheet and peptide nucleic acid facilitates the label-free detection of urinary miRNAs with high specificity and sensitivity. Using real-time detection of miRNAs in patient urine without pretreatment or signal amplification, this sensor allows rapid, direct detection of target miRNAs in a broad dynamic range with a detection limit down to 10 fM in human urine specimens within 20 min and enables simultaneous quantification of multiple miRNAs. As confirmed using a blind comparison with the results of pathological examination of patients with prostate cancer, the sensor offers the potential to improve the accuracy of early diagnosis before a biopsy is taken. This study holds the usefulness of the practical sensor for the clinical diagnosis of urological diseases.

SYNTHESIS OF REDUCED GRAPHENE OXIDE - Mn0.8Zn0.2Fe2O4 - POROUS POLYANILINE NANOCOMPOSITE MATERIALS FOR EFFECTIVE MICROWAVE ABSORPTION IN X-BAND

In this paper, a composite of reduced graphene oxide (RGO), manganese/zinc ferrite (Mn0.8Zn0.2Fe2O4 - MZF) nanoparticles, and porous polyaniline (PANI) was successfully synthesized to improve microwave absorption properties exclusively in X-band. The experimental results demonstrate that the synthesized ternary composite had RGO nanosheets decorated mostly with MZF nanoparticles, and porous PANI was uniformly coated onto the surface of RGO-MZF. The strong reflection loss value of -60.4 dB at 10 GHz and wide effective bandwidth are effectively achieved with the sample which had thicknesses of 2 mm and contained 33 weight % of product. The marked display of the microwave absorption properties of this composite was associated with their notable structure.

Self-Assembled Hybrid of Microwave-Exfoliated V2O5 Nanoribbons and Reduced Graphene Oxide Nanosheets As a Sustainable Electrode Material for Zinc Ion Batteries

Rechargeable aqueous zinc ion batteries are an emerging topic in the battery research due to its high volumetric capacity (5855 mAh/cm3), low cost, environmental friendliness and safety. But the development of the zinc ion batteries have been seriously hindered by the slow insertion/extraction kinetics of the multivalent Zn2+ ions in the host structure. Two-dimensional (2D) transition metal oxides are intensely studied for various energy storage applications such as batteries and supercapacitors but controlled synthesis and tunable nanoscale properties are still a challenge. Herein we present and discuss the self-assembly of a hybrid material of microwave-exfoliated Vanadium pentoxide (V2O5) nanoribbons (NRs) on graphene oxide (GO) nanosheets as a potential host for zinc ion storage. Vanadium pentoxide have several advantages such as high discharge capacity (294 mAhg-1) and large abundance but suffers from low electrical conductivity and poor stability. Using a thermal treatment, the GO template is converted to reduced graphene oxide (rGO) which improves the electrical conductivity of the hybrid. Multiple divalent cations such as Zn2+ and Mn2+ have been used in the self-assembly process to bind the negatively charged V2O5 NRs and GO nanosheets to improve the stability of the hybrid and accommodate the intercalation/deintercalation of the Zn2+ ions. Incorporation of 0.0357 M Mn2+ along with 0.10 M Zn2+ in the assembly process has been found to form a stoichiometric composition of Mn0.15Zn0.08V2O5 by XPS, which provides the high specific capacity of 295 mAh g-1 at 0.5 A g-1 and a high stability with the capacity retention of ~81.3% after 500 cycles at 4 A g-1.

CdS@h-BN heterointerface construction on reduced graphene oxide nanosheets for hydrogen production

Solar light driven hydrogen evolution is a prospective strategy to solve the energy problem. However, the poor photoresponse, low photocurrent density and easy electron-hole recombination remarkably restrict the HER activity of the conventional photocatalyst. Herein, we constructed a CdS@hexagonal boron nitride (h-BN) heterostructure on reduced graphene oxide (rGO) to synthesize a ternary CdS@h-BN/rGO catalyst via a structural reconstruction strategy. The CdS@h-BN heterointerface promoted the electrons transferring to the CdS active centers from the valence band of h-BN under photoinduction, overcoming the wide bandgap defect of pristine h-BN. The easily photoexcited property of CdS cocatalyst resulted in superhigh photocurrent density (2.7·μA cm−2) under simulated solar light, which was 3.3-fold greater of pristine CdS NPs. Meanwhile, the interfacial interactions of three components remarkably restrained the carriers recombination. Hence, the resultant ternary hybrid catalyst presented remarkably improved photoresponse and interfacial conductivity, thereby the optimal catalyst represented remarkably enhanced HER activity (6465.33 μmol h−1 g−1) under simulated solar light, which was about 10.9-fold greater of the pristine CdS NPs and 218.3-fold greater of the optimal h-BN/rGO hybrid. About 19.8 % of apparent quantum yield was achieved under illumination of λ =420 nm, and the excellent regenerability and durability were represented during six cycles and 20 h of continued illumination. Thereby, this study provides a prospective idea for constructing low-cost nonprecious metal based photocatalyst with highly efficient HER performance.

Bi2S3 Nanorods Hosted on rGO Sheets from Pyrolysis of Molecular Precursors for Efficient Li‐Ion Storage

Bismuth‐based compounds with high capacity and durability are still challenging in Li‐ion batteries (LIBs). In this article, Bi2S3 nanorods hosted on reduced graphene oxide nanosheets (Bi2S3/rGO, BSG) are successfully prepared using molecular precursor pyrolysis strategy. 1D nanorod architecture possesses preeminent kinetic characteristics, shortening the ion diffusion path and increasing the contact area between electrode and electrolyte. The large specific surface area and charge polarization of rGO at the interface promote charge transfer. The capacity of material (BSG‐400) reaches 558.4 mAh g−1 at 0.2 A g−1 after 200 cycles. The anode properties of the composite outperform those of pristine Bi2S3. The introduction of graphene enables the interfacial interaction between rGO and Bi2S3. The closely contact interface improves the conductivity and lithium storage performances of Bi2S3. The regulatory effect of rGO on the electronic density of states and band gap of Bi2S3 has been demonstrated by theoretical calculation. The synthetic approach has the advantages of universality, simple operation procedure, and strong repeatability. This research provides some ideas for the preparation of other metal sulfides/rGO nanomaterials and their application in battery research.

Enhanced piezoelectricity properties of reduced graphene oxide (RGO) loaded polyvinylidene fluoride (PVDF) nanocomposite films for nanogenerator application

Flexible and lightweight films of Polyvinylidene fluoride (PVDF) loaded with nanosheets of reduced graphene oxide (RGO) have been prepared via solution casting method. The structure of RGO nanosheets have been examined through X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Raman spectroscopy technique. FTIR studies revealed that the enhancement of β-phase from 53 to 70% has been observed by adding RGO nanosheets in PVDF matrix. The frequency dependent dielectric constant and dielectric loss have been studied. Ultraviolet–visible spectra show a decrease in optical band gap with increases RGO concentration in nanocomposite films. The ferroelectric behavior of RGO loaded PVDF nanocomposite films showed remarkable improvement in remnant polarization values as compared to bare PVDF. The piezo-response of RGO loaded nanocomposite films showed significant enhancement in output voltage from 0.886 to 1.915 V. On exposure to ultraviolet–visible light, RGO loaded nanocomposite PVDF films showed about 13.8% enhancement in piezo- voltage with action of same pressure.

Graphene Field Effect Transistor Biosensors Based on Aptamer for Amyloid-βDetection

The development of cost-efficient, sensitive and specific methods to detect amyloid-beta 42 ( $\text{A}\beta 42$ ) biomarkers in cerebrospinal fluid and serum-samples is of considerable interest to enable early and reliable diagnosis of Alzheimer’s disease as a precondition for future disease-modifying therapies. This paper presents a reduced graphene oxide field effect transistor (r-GO FET) for label free ultrasensitive detection of an $\text{A}\beta 42$ -biomarker with RNA aptamer. The channel in the device was formed by reduction of graphene oxide nanosheets by self-assembly process. As a result, the interaction between $\text{A}\beta 42$ and RNA aptamer on the surface of r-GO channel caused a linear response in the shift of the gate voltage ( $\text{V}_{\mathbf {TG}}$ ) where the minimum conductivity occurs. The r-GO FET can detect the biomarker in range of 1ng/ml to 1pg/ml at pH 7.4 with high specificity. The developed r-GO FET is a low-cost, highly sensitive and selective method for detecting tiny concentrations of $\text{A}\beta 42$ , which would also enable measurements in serum-samples.

One-step construction of MoO2 uniform nanoparticles on graphene with enhanced lithium storage

Transition−metal oxides are considered to be a promising anode material for lithium−ion batteries (LIBs) due to their high capacities, low cost, and ease of synthesis. Herein, a hybrid nanosheet composed of uniform MoO2 nanoparticles (NPs) homogeneously immobilized on the reduced graphene oxide nanosheets (MoO2 NP@rGO) is first synthesized by a self-templating and subsequent calcination treatment. The unique two-dimensional hybridnanosheets provides several merits. rGO can be used as a favorable support for the loading of electrochemically active MoO2 NPs. Meanwhile, MoO2 NPs can effectively prevent the stacking of the rGO. The effective combination of MoO2 NPs and rGO nanosheets furnish additional electrochemically interfacial active sites for extra lithium ion storage. Noticeably, the as-fabricated hybrid nanosheets deliver a reversible capacity of 641 mAh/g after 350 cycles at a current density of 1000 mA/g with a good rate capability. The greatly enhanced lithium storage properties of MoO2 NP@rGO indicate the importance of elaborate construction of novel hybrid hierarchical structures.

Strong, conductive aramid fiber functionalized by graphene

The surface modification of aramid fibers is an essential and potent approach to manipulate and improve fiber properties. Biogenic fibers are in stark contrast, as exemplified by the case of natural silk fibers. This high-performance fiber features a surface functionalization as a thin sericin film enwraps it for improving the mechanical properties of silks. Inspired by this unique sheath structure of biogenic silk, we improved the performance of aramid fibers by exploiting a coating composed of reduced graphene oxide nanosheets that self-assemble on the fiber surface guided by hydrogen bonding and π-π stacking interactions. The graphene functionalized aramid fibers show a remarkable 1 GPa improvement in tensile strength. Moreover, the functionalized aramid fiber also shows high electrical conductivity which preserved 99% of its conductivity even after 100 cycles. Our approach provides a universal strategy for improving the performance of the fiber via surface functionalization by graphene nanosheets.

Influence of Sputtering Temperature of TiO2 Deposited onto Reduced Graphene Oxide Nanosheet as Efficient Photoanodes in Dye-Sensitized Solar Cells.

Renewable solar energy is the key target to reduce fossil fuel consumption, minimize global warming issues, and indirectly minimizes erratic weather patterns. Herein, the authors synthesized an ultrathin reduced graphene oxide (rGO) nanosheet with ~47 nm via an improved Hummer’s method. The TiO2 was deposited by RF sputtering onto an rGO nanosheet with a variation of temperature to enhance the photogenerated electron or charge carrier mobility transport for the photoanode component. The morphology, topologies, element composition, crystallinity as well as dye-sensitized solar cells’ (DSSCs) performance were determined accordingly. Based on the results, FTIR spectra revealed presence of Ti-O-C bonds in every rGO-TiO2 nanocomposite samples at 800 cm–1. Besides, XRD revealed that a broad peak of anatase TiO2 was detected at ~25.4° after incorporation with the rGO. Furthermore, it was discovered that sputtering temperature of 120 °C created a desired power conversion energy (PCE) of 7.27% based on the J-V plot. Further increase of the sputtering temperature to 160 °C and 200 °C led to excessive TiO2 growth on the rGO nanosheet, thus resulting in undesirable charge recombination formed at the photoanode in the DSSC device.

Pd nanocrystals grown on MXene and reduced graphene oxide co-constructed three-dimensional nanoarchitectures for efficient formic acid oxidation reaction

Although direct formic acid fuel cell (DFAFC) is regarded as one of the most promising energy-conversion systems, its commercialization process is impeded by the high costs of electrode catalysts as well as the sluggish catalytic reaction kinetics. Herein, we present a convenient bottom-up method to the synthesis of nanosized Pd crystals grown on 3D porous hybrid nanoarchitectures constructed from MXene (Ti3C2Tx) and reduced graphene oxide nanosheets (Pd/MX-rGO) through a co-assembly process. The as-derived 3D Pd/MX-rGO nanoarchitecture is equipped with a number of attractive textural features, such as 3D cross-linked porous networks, large specific surface area, uniform Pd dispersion, optimized electronic structure, and good electron conductivity. As a result, unusual formic acid oxidation properties in terms of high catalytic activity, strong poison tolerance, and reliable long-term stability are achieved for the 3D Pd/MX-rGO catalyst, significantly superior to those for conventional Pd catalysts supported by carbon black, graphene, and Ti3C2Tx matrixes.

Solvent Effect on Supramolecular Self-Assembly of Chlorophylls a on Chemically Reduced Graphene Oxide.

Solvent plays an important role in the surface interaction of molecules. In this study, we use "chlorophyll a", an archetypical molecule, to investigate its supramolecular self-assembly with chemically reduced graphene oxide in three different types of solvents: polar protic, polar aprotic, and non-polar. It was observed that only a polar protic solvent that can donate protons facilitates the hydrogen bonding between chlorophyll a and chemically reduced graphene oxide nanosheets in a hybrid system. The formation of hydrogen bonds further initiates the other non-covalent interactions such as π-π stacking and hydrophobic interaction, which altogether play a key driving force for supramolecular self-assembly of chlorophylls on chemically reduced graphene oxides. The experimental results are strongly supported by density functional theory calculations, which show robust electron coupling between chlorophylls and chemically reduced graphene oxide.

A novel ternary composite aerogel for high-performance supercapacitor

Despite the attractive features of existing supercapacitors (SCs), SC devices still exhibit low mass loading, limited working voltage, low specific capacitance, short cycle life, and unsatisfactory energy density. In this study, we introduced novel self-suspended polyaniline (S-PANI) into a combination of manganese dioxide (MnO2) and reduced graphene oxide (RGO) to propose an efficient SC electrode for energy storage applications. The unique addition of lightweight, highly conductive, exceptionally water-soluble, and unique fibrillar structure S-PANI increased the conductivity of composite aerogels and reduced the ionic diffusion resistance of electrode materials. The introduction of S-PANI significantly improved the dispersion of MnO2 particles and enabled MnO2 to give full play to its pseudopotentiability. The MnO2/S-PANI/P-RGO ternary composite aerogel was prepared by the self-assembly hydrothermal technique where different mass ratios of MnO2, S-PANI, and RGO were used and analyzed. Physical analyses showed that MnO2/S-PANI/P-RGO composite aerogels had a 3D porous network structure and MnO2 nanospheres are evenly disseminated on the surface of RGO nanosheets. The flowable S-PANI reduced the solid-solid contact resistance in the electrode. The developed 3D MnO2/S-PANI/P-RGO composite aerogel electrode displayed a specific capacitance of 571 F g−1 at the current density of 1 A g−1 along with the specific capacitance of 413 F g−1 with an increased current density of 40 A g−1 and the capacity retention rate of 72.6 %. Also, the initial capacitance retention of 96.7 % was attained after 10,000 cycles at a current density of 20 A g−1 is attained, displaying significant and long-term stability of the composite aerogel electrode. In summary, MnO2/S-PANI/P-RGO composite aerogels reported in this study are promising in energy storage applications demanding high specific capacitance and cycle life.

Readily Dispersible Chemically Functionalized Reduced Graphene Oxide Nanosheets for Solution-Processable Electrodes and Conductive Coatings

Reduced graphene oxides (rGO) are a promising class of materials for scalable electrodes and performance enhancing additives; however, commercial deployment of these materials is challenged by thei...

Nanomolar level detection of non-steroidal antiandrogen drug flutamide based on ZnMn2O4 nanoparticles decorated porous reduced graphene oxide nanocomposite electrode

Flutamide is a non-steroidal antiandrogen drug and widely used in the treatment of prostatic carcinoma. Nevertheless, the excessive intake and improper disposal could affect the living organisms. In this work, we have synthesized a new nanocomposite based on ZnMn2O4 nanoparticles and porous reduced graphene oxide nanosheets (ZnMn2O4-PGO) for the electrocatalytic detection of flutamide (FLU) drug. The crystallinity and morphological properties of ZnMn2O4-PGO composite examined by different characterization techniques such as X-ray diffraction, Raman spectroscopy and so on. The fabricated ZnMn2O4-PGO nanocomposite modified electrode exhibited superior electrocatalytic performance to FLU drug in an optimized pH electrolyte. Fascinatingly, the electrode received a wide linear range (0.05–3.5 µM) with limit of detection of 8 nM. Besides, the developed ZnMn2O4-PGO nanocomposite electrode showed good sensitivity 1.05 µAµM−1 cm−2 and excellent selectivity for FLU detection in presence of various interfering species. A developed disposable electrode was scrutinized to determine FLU level in human urine samples by spiking method and the results achieved good recoveries in real sample analysis.

High-efficiency microwave absorption and electromagnetic interference shielding of Cobalt-doped MoS2 nanosheet anchored on the surface reduced graphene oxide nanosheet

In this paper, Co-doped molybdenum disulfide anchored on the surface reduced graphene oxide (Co@MoS2/rGO) has been successfully synthesized using a simple and effective hydrothermal approach to measure their microwave shielding properties. The X-ray diffraction (XRD) technique confirmed the successful doping of magnetic atoms into the MoS2 lattice. The experiments show that 15% and 20% Co@MoS2/rGO nanocomposite have higher electromagnetic interference shielding effectiveness (EMI SE) value up to SET ~ 38.26 and ~ 46.02 dB, respectively. But pure MoS2/rGO nanocomposite demonstrates a lower EMI SE value of around ~ 28.90 dB over the frequency range of 8.0–12.0 GHz with a 1.7 mm thickness. A higher value of the EMI SE depends mainly on the doping percentage of Co-ion. This nanocomposite network enhances the defect dipole polarization, electric conduction, interfacial polarization, and impedance matching characteristics. It is favorable for strong attenuation and dissipation loss ability of microwave energy inside the shielding material. The actual role of Co-doping is to form a highly conductive and magnetic channel between multi-interfaces leading to enhance the migration and hopping of electrons at defective sites or interface. Therefore, the 20% Co@MoS2/rGO nanocomposite is considered as novel microwave shielding material and can be widely used in electronic information and communication devices.

On the Role of γ-Fe2O3 Nanoparticles and Reduced Graphene Oxide Nanosheets in Enhancing Self-Cleaning Properties of Composite TiO2 for Cultural Heritage Protection

The durability of novel metallic artifacts and buildings is an open issue, and the role of smart protecting coatings in extending these artifacts’ lifetimes is crucial. In this paper, the role of γ-Fe2O3 nanoparticles and reduced graphene oxide (rGO) nanosheets on enhancing the self-cleaning properties of composite TiO2 films and reducing metal alterations due to contact with acid rain and pollutants is investigated. The photocatalytic assessment of the TiO2 based films indicates that there are optimum contents for γ-Fe2O3 and rGO, which confer the film lower bandgap and tune the TiO2 anatase/rutile ratio. By adding a proper content of γ-Fe2O3, wettability is reduced both in dark and under illumination, which could be related to higher roughness. γ-Fe2O3 overloading causes increasing crack density and eventually a fully cracked structure. Adding an appropriate amount of rGO causes a sharp increase in roughness, due to the stacking of rGO nanosheets, while simultaneously avoiding cracking. At higher contents of rGO, wettability further decreases due to higher amounts of hydroxyl groups bound onto rGO; also in this case, overloading causes film cracking. Evaluation of self-cleaning performance and discoloration resistance under soiling and acid rain simulated tests demonstrates that proper loadings of γ-Fe2O3 and rGO present higher efficiency thanks to higher superhydrophilic tendency and higher photocatalytic activities, as well as an efficient barrier effect.