Surface Of Reduced Graphene Oxide Sheets Research Articles

Preparation and characterization of ball milled hexagonal‑boron nitride (BMBN) and fluorescein (FL) decorated reduced graphene oxide (RGO) nanocomposite towards toxic heavy metal ion detection

In the present work, a novel hybrid fluorescent nanocomposite (RBF) based on ball milled hexagonal-Boron Nitride (BMBN) and Fluorescein (FL) decorated reduced Graphene Oxide (RGO) was synthesized for the effective detection and removal of hazardous heavy metal ions present in effluents. Where two different textile effluents namely, reaction outlet and factory outlet collected at the river Noyyel, Tamilnadu were considered. The prepared RBF was subjected to XRD, FTIR, SEM, EDX, TEM, PSA, BET, UV–vis, PL and XPS studies which strongly confirm the decoration of FL and BMBN at the surface of RGO sheets. The selectivity of RBF was examined by considering various toxic heavy metal ions. Where the RBF exhibits remarkable sensing towards Zn2+ (10.7 nM) via enhanced fluorescence and for Fe3+ (15.6 nM), Sn4+ (60.7 nM) and Hg2+ (465.4 nM) ions by “Turn-off” fluorescence only at neutral pH. In addition, the RBF was highly efficient to remove Hg (81.3 %) than Zn (63.7 %), Fe (38.2 %) and Sn (62.9 %) in real-time samples. Moreover, the prepared RBF could also serve as water sensor for the water contaminated organic solvents of Acetonitrile (ACN) and Tetrahydrofuran (THF). Hence the prepared RBF might be a potential choice for the effective detection and removal of heavy metal ions during wastewater treatment.

Photocatalytic Degradation of Methylene Blue and Anticancer Response of In2O3/RGO Nanocomposites Prepared by a Microwave-Assisted Hydrothermal Synthesis Process.

The incorporation of graphene with metal oxide has been widely explored in various fields, including energy storage devices, optical applications, biomedical applications, and water remediation. This research aimed to assess the impact of reduced graphene oxide (RGO) doping on the photocatalytic and anticancer properties of In2O3 nanoparticles. Pure and In2O3/RGO nanocomposites were effectively synthesized using the single-step microwave hydrothermal process. XRD, TEM, SEM, EDX, XPS, Raman, UV-Vis, and PL spectroscopy were carefully utilized to characterize the prepared samples. XRD data showed that synthesized In2O3 nanoparticles had high crystallinity with a decreased crystal size after RGO doping. TEM and SEM images revealed that the In2O3 NPs were spherical and uniformly embedded onto the surface of RGO sheets. Elemental analysis of In2O3/RGO NC confirmed the presence of In, O, and C without impurities. Raman analysis indicated the successful fabrication of In2O3 onto the RGO surface. Uv-Vis analysis showed that the band gap energy was changed with RGO addition. Raman spectra confirmed that In2O3 nanoparticles were successfully anchored onto the RGO sheet. PL results indicated that the prepared In2O3/RGO NCs can be applied to enhance photocatalytic activity and biomedical applications. In the degradation experiment, In2O3/RGO NCs exhibited superior photocatalytic activity compared to that of pure In2O3. The degradation efficiency of In2O3/RGO NCs for MB dye was up to 90%. Biological data revealed that the cytotoxicity effect of In2O3/RGO NCs was higher than In2O3 NPs in human colorectal (HCT116) and liver (HepG2) cancer cells. Importantly, the In2O3/RGO NCs exhibited better biocompatibility against human normal peripheral blood mononuclear cells (PBMCs). All the results suggest that RGO addition improves the photocatalytic and anticancer activity of In2O3 NPs. This study highlights the potential of In2O3/RGO NCs as an efficient photocatalyst and therapeutic material for water remediation and biomedicine.

Reduced graphene oxide/Ag nanoparticle aerogel for efficient solar water evaporation

To improve the efficiency of solar water evaporation, Ag nanoparticles (AgNPs)/reduced graphene oxide (RGO) aerogel (RGOA/Ag) were prepared by hydrothermal reduction and freeze-drying method. The FESEM images showed that AgNPs were successfully loaded onto the surface of RGO sheets. The assembly of RGO during the formation of aerogel gave rise to multilevel-pore structure and ordered water channels. The coupling of multilevel-pore structure and AgNPs enhanced the optical absorption of RGOA/Ag up to 90.45% in the Vis-near IR region. And the high absorption and ordered channels enhanced the water evaporation rate (WER). The water evaporation monitoring showed that the WER of RGOA/Ag reached 1.56 kg m-2 h-1 under one-sun illumination (1 kW m-2), and the photothermal conversion efficiency (PTCE) reached as high as 97.9%. The excellent water evaporation properties caused by the unique structure of RGO-based aerogels can provide valuable strategy for high efficiency of solar water evaporation.

Microstructure and Photocatalytic Properties of TiO2–Reduced Graphene Oxide Nanocomposites Prepared by Solvothermal Method

TiO2–reduced graphene oxide (RGO) nanocomposites have been prepared by a solvothermal method using Ti(SO4)2 and graphene oxide (GO) in aqueous/ethanol suspension and their microstructure and optical and photocatalytic properties investigated. The results show that, for all cases, graphene oxide was partially reduced to RGO during the solvothermal process, and anatase TiO2 nanoparticles (~ 10 nm) accumulated on the surface of RGO sheets. The formal valence state Ti4+ was identified in all cases, whereas Ti–O–C bond can form in the TiO2–RGO nanocomposites due to the strong chemical bonding effect. On increasing the mass ratio (x) of GO/Ti(SO4)2, the bandgap of the nanocomposites became narrow, thus extending the absorption wavelength range. TiO2–RGO nanocomposites exhibited good photogenerated electron transfer properties as proven by photoluminescence spectra. However, excessive addition of GO (x ≥ 1/40) decreased the photoelectron transfer performance. The photocatalytic activity was studied under ultraviolet (UV) and visible light, being greatly improved with addition of GO at x = 3/200 then decreased at x ≥ 1/40. TiO2–RGO nanocomposite (x ≤ 3/200) also exhibited better photocatalytic performance than pure TiO2 under visible light, indicating increased absorption.

Synthesis of Fe@Ni nanoparticles-modified graphene/epoxy composites with enhanced microwave absorption performance

High performance microwave absorber consisting of Fe@Ni nanoparticles (NPs) modified reduced graphene oxide (RGO) and epoxy resin was successfully prepared. Fe@Ni NPs obtained via electroless plating method could be simply anchored on the surface of RGO sheets because of its high surface area, as well as residual organic groups of RGO. The crystal/micro-structure and magnetic properties of as-synthesized samples were subsequently analyzed by XRD, SEM, TEM, XPS and VSM, while electromagnetic properties were tested by vector network analyzer. The synergistic effect between graphene and Fe@Ni NPs generated suitable impedance match and strong microwave attenuation ability which lead to excellent microwave absorption property. The optimal reflection loss (RL) calculated from measured electromagnetic parameters can reach up to − 22.7 dB at 14.9 GHz with a layer thickness of 2 mm. Moreover, RL values < − 10 dB is found to be 5.5 GHz within 12.5–18 GHz, almost covering the entire Ku band. It’s convincing that the as-synthesized composites are potential candidates for high-performance lightweight microwave absorbers.

Preparation of porous Fe2O3 nanorods-reduced graphene oxide nanohybrids and their excellent microwave absorption properties

In this paper, α-Fe2O3 nanoparticles (NPs)-reduced graphene oxide (RGO), α-FeOOH nanorods (NRs)-RGO and porous α-Fe2O3 NRs-RGO could be selectively synthesized by hydrothermal method. The investigations indicated that the obtained α-Fe2O3 NPs, α-FeOOH NRs and porous α-Fe2O3 NRs were either attached on the surface of RGO sheets or coated uniformly by the RGO sheets. And the as-prepared nanohybrids exhibited excellent microwave absorption performance, which was proved to be ascribed to the quarter-wavelength matching model. The optimum reflection loss (RL) values for α-Fe2O3 NPs-RGO, α-FeOOH NRs-RGO and porous α-Fe2O3 NRs-RGO were ca. −32.3, −37.4 and −71.4 dB, respectively. Moreover, compared to the obtained α-Fe2O3 NPs-RGO and α-FeOOH NRs-RGO, the as-prepared porous α-Fe2O3 NRs-RGO nanohybrids exhibited enhanced microwave absorption properties because of their special structure and synergetic effect. The possible enhanced microwave absorption mechanisms were discussed in details. Our results confirmed that the geometrical morphology had a great influence on their microwave absorption properties, which provided a promising approach to exploit high performance microwave absorbing materials.

Facile hydrothermal procedure to synthesize sheet-on-sheet reduced graphene oxide (RGO)/CuxO[sbnd]CeO2 nanocomposites for preferential oxidation of carbon monoxide

The sheet-on-sheet reduced graphene oxide (RGO)/CuxOCeO2 catalysts were synthesized by a facile hydrothermal procedure and systematically characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, hydrogen temperature-programmed reduction, X-ray photoelectron spectroscopy and N2 adsorption–desorption techniques. It is found that there is a large amount of reduced copper species in the RGO/CuxOCeO2 catalysts, and the addition of RGO was beneficial for the dispersion of particles and the improvement of textural properties. The spherical nanoparticles of copper species can be served as spacers to prevent the stacking of RGO. Copper and cerium species are homogenously distributed on the surface of RGO sheets. The introduction of RGO improves the formation of high Ce3+ concentration and oxygen vacancies. Therefore, the RGO/CuxOCeO2 catalysts show higher catalytic activity than the CuOCeO2 catalyst at low temperature (below 135 °C). Moreover, good resistance to H2O and CO2 of the RGO/CuxOCeO2 may be from for the formation of hydroxyl groups by dissociative adsorption of H2O on the surface of RGO, which can improve the WGS reaction and the decomposition of carbonates.

CuO Nanorods-Decorated Reduced Graphene Oxide Nanocatalysts for Catalytic Oxidation of CO

Developing an efficient non-noble catalyst for CO oxidation with high catalytic activity remains a challenge for practical applications. In this work, CuO nanorods decorated reduced graphene oxide (RGO) nanocatalysts were prepared via a facile one-step hydrothermal method. The structure and morphology of the as-prepared samples were characterized by XRD, Raman spectroscopy, SEM, TEM, and X-ray photoelectron spectroscopy (XPS). The analysis results show that CuO nanorods were successfully deposited on the surface of RGO sheets with the length of 250–500 nm. The catalytic properties of the as-prepared catalysts for CO oxidation were evaluated by using a microreactor-gas chromatograph (GC) system. The as-prepared RGO–CuO nanocatalysts exhibited high activity for CO oxidation, and the 10 wt % reduced graphene oxide content catalyst can achieve CO total oxidation at 165 °C.

Facile synthesis and enhanced catalytic performance of reduced graphene oxide decorated with hexagonal structure Ni nanoparticles

In this study, reduced graphene oxide (RGO) supported Ni nanoparticles were synthesized by a facile in-situ refluxing approach using triethylene glycol as both reductive and dispersing agent. The as-synthesized RGO/Ni nanocomposites were characterized by X-ray diffraction, Raman spectroscopy and transmission electron microscopy, which revealed that Ni nanoparticles with hexagonal close-packed structure were homogeneously dispersed on the surface of RGO sheets. The catalytic activity and electrochemical properties of the RGO/Ni nanocomposites were investigated. It is found that the RGO/Ni nanocomposites exhibit markedly enhanced catalytic activity toward the reduction of p-nitrophenol by NaBH4, which is comparable to noble metal catalyst. The RGO/Ni nanocomposites also exhibited excellent electrocatalytic response to glucose. The linear range, detection limit and sensitivity were estimated to be 0.01–3.0mM (R2=0.997), 2.8μM and 535.258μAmM−1cm−2, respectively. It is expected that this facile method presented here could be extended to synthesize other RGO/metal nanocomposites with various functions.

Ionic self-assembled porphyrin-graphene composite for enhanced photocurrent response and electrochemical property

We have synthesized cationic mesa-tetra(4-pyridyl) porphine (TPyP)-reduced graphene oxide (RGO) hybrid structures through chemical reduction and subsequent ionic self-assembly. UV–vis spectroscopy, fluorescence emission spectroscopy and scanning and transmission electron microscopies are used to analyze the structures, which indicate that TPyP covalent bonds present between the double surface of RGO sheets. A reversible on/off photo-current density of 45.89A/cm2 has been observed when the as-formed TPyP/RGO nanocomposite is placed in the environment of pulsed white-light illumination. In addition, an ultrasensitive electrochemical aptasensor could be fabricated by the as-prepared TPyP/RGO to detect thrombin. A linear response to thrombin has been observed with the as-formed electrochemical aptasensor in the concentration range of 1–1200nM. Besides, the limitation of detection is determined to be 0.3nM.

Facile synthesis of Mn3O4/reduced graphene oxide nanocomposites with enhanced capacitive performance

In this study, a facile refluxing approach has been developed to load Mn3O4 nanocrystals onto reduced graphene oxide (RGO) sheets. The microstructure and morphology of the resulting Mn3O4/RGO nanocomposites were systematically investigated by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM). The results reveal that Mn3O4 nanocrystals with particle size of several nanometers were uniformly dispersed on the surface of RGO sheets. The electrochemical properties of the resulting Mn3O4/RGO nanocomposites were investigated by using them as electrode materials for a supercapacitor. It is found that the Mn3O4/RGO nanocomposites exhibit enhanced specific capacitance and long-term stability. The enhanced capacitive performance can be attributed to the synergistic effect among Mn3O4 and RGO. The facile synthesis and the enhanced capacitive performance demonstrate the promising application of the Mn3O4/RGO nanocomposites as supercapacitor electrode materials.

One-step synthesis of reduced graphene oxide-supported PtCo nanoalloys with enhanced electrocatalytic activity for methanol oxidation

Direct methanol fuel cells (DMFCs) have recently become the research hotspot, due to their high energy-conversion efficiency, low operating temperature, and low exhaust emission. In this study, PtCo nanoalloys supported on reduced graphene oxide (RGO) were successfully synthesized via a one-step reduction method, carried out by coreduction of PtCl6 2−, Co2+ and graphene oxide (GO) in ethylene glycol. Fourier-transform infrared spectra, X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy techniques were used to study microstructure, composition, particle size, and morphology, respectively. The results show that highly dispersed PtCo nanoalloys with average sizes of ca. 2.4 nm are dispersed on the surfaces of RGO sheets. The catalytic performances of the PtCo/RGO, Pt/RGO, and Pt/C catalysts toward methanol oxidation were studied, which indicates that PtCo/RGO nanoalloys show higher catalytic performance and stability than Pt/RGO and Pt/C catalysts. Furthermore, the PtCo/RGO catalyst exhibits improved CO-tolerance ability due to the addition of Co.

Controlled synthesis of Fe3O4@SnO2/RGO nanocomposite for microwave absorption enhancement

A ternary nanocomposite of Fe3O4@SnO2/reduced graphene oxide (RGO) with different contents of SnO2 nanoparticles was synthesized by a simple and efficient three-step method. The transmission electron microscopy and field emission scanning electron microscopy characterization display that plenty of Fe3O4@SnO2 core–shell structure nanoparticles are well distributed on the surface of RGO sheets. The X-ray diffractograms show that the products consist of highly crystallized cubic Fe3O4, tetragonal SnO2 and disorderedly stacked RGO sheets. The magnetic hysteresis measurement reveals the ferromagnetic behavior of the products at room temperature. The microwave absorption properties of paraffin containing 50wt% products were investigated at room temperature in the frequency range of 2–18GHz by a vector network analyzer. The electromagnetic data show that the maximum reflection loss is −45.5dB and −29.5dB for Fe3O4@SnO2/RGO-1 and Fe3O4@SnO2/RGO-2 nanocomposite, respectively. Meanwhile, the reflection loss less than −10dB is up to 14.4GHz and 13.8GHz for Fe3O4@SnO2/RGO-1 and Fe3O4@SnO2/RGO-2 nanocomposite, respectively. It is believed that such nanocomposite could be used as promising microwave absorbers.

The confinement of SnO2nanocrystals into 3D RGO architectures for improved rate and cyclic performance of LIB anode

In this study, we demonstrate the synthesis of a composite with SnO2 nanoparticles anchored on three-dimensional (3D) reduced graphene oxide (RGO) as an anode for Li ion batteries (LIBs). SnO2 nanoparticles were uniformly deposited on the surface of RGO sheets and the resulting RGO–SnO2 architecture had an interconnected hierarchical structure. This hierarchical RGO–SnO2 architecture exhibited outstanding electrochemical performance with a high reversible capacity of 810 mAh g−1 at 0.1 A g−1 and a high rate capacity of 210 mAh g−1 at 2 A g−1. Moreover, this architecture achieves 99% capacity retention even after 150 cycles at 0.1 A g−1. The improved performance of the RGO–SnO2 architecture is attributed to the uniform dispersion of SnO2 nanoparticles and the 3D macroporous continuity, which afford a highly accessible area, easy ion accessibility, a short ion diffusion length, and rapid mass and charge transport. The composite described here is practically useful in the development of high-energy-density anode materials for LIBs.

Al doped-ZnO nanoparticles implanted in reduced graphene oxide with improved electrochemical properties for lithium ion batteries

Al-doped ZnO nanoparticles (AZONs) have been successfully implanted in reduced graphene oxide (RGO) by a simple annealing process. The unique layered structure of composites is obtained, which is mainly ascribed to the well-anchored AZONs on the surface of RGO sheets. As anode materials for lithium ion batteries, the AZONs/RGO composites deliver an initial charge capacity of 624mAhg−1 and a 100th charge capacity of 391mAhg−1. Compared to pure AZONs, the remarkably enhanced reversible capacity and cycling stability of the composites could be attributed to the unique structure and the synergistic effect between the AZONs and RGO.

One-pot microwave-assisted synthesis of reduced graphene oxide/nickel cobalt double hydroxide composites and their electrochemical behavior

Reduced graphene oxide (RGO)/nickel cobalt (NiCo) double hydroxide composites were synthesized by one-pot microwave-assisted method in propylene carbonate. This method is efficient because the reduction of graphene oxide and the formation of hydroxide particles on the graphene sheets were simultaneously produced. We investigated an effect of microwave irradiation in organic solvent and an electrochemical influence of nickel and cobalt ratio in double hydroxide. Morphological characterization was performed by XRD, FTIR, XPS and FE-SEM. It was found that the NiCo double hydroxide particles were well decorated on the surface of RGO sheets and the reduction of graphene oxide was completed by short-term microwave irradiation. Electrochemical behavior was also measured by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge performance. The highest specific capacitance was 1622Fg−1 obtained at (RGO)/NiCo 2:1 (weight ratio of nickel to cobalt was 2–1). Furthermore, the composites showed higher capacitance, as well as lower resistance, better rate capability and longer cycle life rather than RGO/Ni(OH)2 and RGO/Co(OH)2.

Hierarchically structured reduced graphene oxide/WO3 frameworks for an application into lithium ion battery anodes

In this study, we demonstrate the synthesis of WO3 particle deposited on three-dimensional (3D) macroporous reduced graphene oxide (RGO) frameworks for lithium ion battery anodes. WO3 particles are uniformly deposited on the surface of RGO sheets and the resulting RGO/WO3 frameworks reveal hierarchically structured, 3D networks assembled during a hydrothermal process. The hierarchically architectured RGO/WO3 hybrid frameworks achieve a discharge capacity of 487mAhg−1 even after 100 cycles at 150mAg−1 and reversible capacity as high as 356mAhg−1 at a high rate of 300mAg−1. Such the improved battery performances of RGO/WO3 frameworks are attributed to uniform dispersion of discrete WO3 particles and 3D macroporous continuity, which provides a high accessible area, easy accessibility to redox sites, short ion diffusion length, and rapid charge and mass transport.

High quality Pt–graphene nanocomposites for efficient electrocatalytic nitrite sensing

Abstract A promising electrochemical sensor, Pt nanoparticles decorated on the surface of reduced graphene oxide (RGO) sheets were facilely synthesized by a one-pot hydrothermal method. The morphology and composition of as-prepared Pt–RGO composites have been characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and X-ray diffraction (XRD). It is found that Pt nanoparticles with ca. 4.81 ± 1.54 nm in diameter were evenly distributed on the surface of RGO sheets. The cyclic voltammetry shows that Pt–RGO nanocomposite has a higher electron transfer rate and remarkable increase electrochemical activity toward the oxidation of nitrite. The amperometry reveals that the Pt–RGO modified electrode exists a good linear relationship between peak current and concentration of nitrite with a low detection limit of 0.1 μM and high sensitivity of 496.4 μA mM−1. Moreover, the as-synthesized Pt–RGO electrode display a fast amperometric response within 4 s. Compared to the bare Pt nanoparticles or the RGO modified glassy carbon (GC) electrode, the as-synthesized Pt–RGO nanocomposite shows a well reproducibility, stability and anti-interference electrocatalytic performance toward nitrite sensing.

One-step reduction and functionalization protocol to synthesize polydopamine wrapping Ag/graphene hybrid for efficient oxidation of hydroquinone to benzoquinone

Based on the excellent properties of dopamine (reduction, self-polymerization and adhesion), we designed a one-step and environment-friendly reduction route to synthesize and simultaneously functionalize polydopamine (PDA)–Ag–reduced graphene oxide (RGO) hybrid. The obtained PDA–Ag–RGO hybrid was characterized by transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, FT-IR and UV–vis analysis. Silver nanoparticles were uniformly dispersed on the surface of RGO sheets and coated with a thin PDA film. The hybrid exhibited good dispersivity in polar solvents (water and acetonitrile). Compared with Ag–RGO hybrid prepared via NaBH4 reduction and commercial Pd/C catalyst, PDA–Ag–RGO hybrid had better catalytic activity for the oxidation of hydroquinone to benzoquinone in the presence of H2O2. Moreover, the hybrid still retained superior catalytic activity over multiple cycles.

Ag nanoparticles decorated MnO2/reduced graphene oxide as advanced electrode materials for supercapacitors

Abstract A ternary nanocomposite of Ag/MnO 2 /RGO, in which reduced graphene oxide (RGO) sheets are decorated with Ag and MnO 2 nanoparticles, is synthesized by in situ growth of MnO 2 nanoparticles on graphene oxide (GO) sheets, following by co-reduction of Ag + and GO. The in situ formed Ag and MnO 2 nanoparticles with sizes of several nanometers are homogeneously distributed on the surface of RGO sheets. The composites as electrode materials for supercapacitors are investigated. It is found that the Ag/MnO 2 /RGO nanocomposites exhibit excellent capacitive performance with a specific capacitance as high as 467.5 F g −1 at the scan rate of 5 mV s −1 , which is much higher than that of MnO 2 /RGO nanocomposites (293.2 F g −1 ). Moreover, the specific capacitance of Ag/MnO 2 /RGO does not show any obvious degeneration after 1000 cycles at the scan rate of 80 mV s −1 , indicating that the Ag/MnO 2 /RGO composites possess an excellent cycle life. The greatly enhanced capacitive performance of the Ag/MnO 2 /RGO nanocomposites is mainly attributed to the introduction of Ag nanoparticles, which can increase the electrical conductivities of the nanocomposites, and promote the electron transfer between the active components. This study suggests that graphene-based ternary nanocomposites are a promising class of electrode materials for high performance energy storage applications.