rGO Layers Research Articles

Solid-state processed novel germanium/reduced graphene oxide composite: Its detailed characterization, formation mechanism and excellent Li storage ability

By using a simple solid-state reduction process, germanium oxide (GeO2) and graphene oxide (GO) are reduced to germanium (Ge) and reduced graphene oxide (rGO), respectively, to form Ge/rGO composite. Transmission electron microscopy showed that clusters of Ge nanoparticles are decorated on the graphene layers of rGO. Detailed x-ray diffraction, Raman scattering, and x-ray photoelectron spectroscopic analyses confirmed Ge/rGO composite formation. The thermal stability of Ge/rGO composite and the reduction mechanism through which the composite is formed are experimentally elucidated. Further, Brunauer–Emmett–Teller (BET) specific surface area, average pore volume, and average pore size of Ge/rGO composite are measured to be ∼115 m2/g, ∼0.4 cm3/g, and ∼14 nm, respectively. The thermal analysis quantified the amount of rGO in the Ge/rGO composite to be ∼66%. As-synthesized Ge/rGO composite is tested as anode material in Li-ion batteries. When cycled at 160 mA/g current density and in the 0.005–3.0 V voltage range, the composite showed an excellent reversible capacity of ∼539 mAh/g that corresponds to 98% capacity retention at the end of the 100th cycle. The Ge/rGO composite also showed high reversible capacity retention, good rate capability, and excellent cycle life when tested at 80 and 320 mA/g in the same voltage range. The redox peaks in the cyclic voltammetry (CV) curves revealed that alloying-dealloying and electrochemical adsorption-desorption mechanisms are the primary reasons for the lithium-ions storage by Ge and rGO, respectively. A constant area under the CV curves throughout the test indicated the stable capacity. Also, the CV results align with the galvanostatic cycling results.

Cation-Driven Assembly of Bilayered Vanadium Oxide and Graphene Oxide Nanoflakes to Form Two-Dimensional Heterostructure Electrodes for Li-Ion Batteries.

Lithium preintercalated bilayered vanadium oxide (LVO or δ-LixV2O5·nH2O) and graphene oxide (GO) nanoflakes were assembled using a concentrated lithium chloride solution and annealed under vacuum at 200 °C to form two-dimensional (2D) δ-LixV2O5·nH2O and reduced GO (rGO) heterostructures. We found that the Li+ ions from LiCl enhanced the oxide/carbon heterointerface formation and served as stabilizing ions to improve structural and electrochemical stability. The graphitic content of the heterostructure could be easily controlled by changing the initial GO concentration prior to assembly. We found that increasing the GO content in our heterostructure composition helped inhibit the electrochemical degradation of LVO during cycling and improved the rate capability of the heterostructure. A combination of scanning electron microscopy and X-ray diffraction was used to help confirm that a 2D heterointerface formed between LVO and GO, and the final phase composition was determined using energy-dispersive X-ray spectroscopy and thermogravimetric analysis. Scanning transmission electron microscopy and electron energy-loss spectroscopy were additionally used to examine the heterostructures at high resolution, mapping the orientations of rGO and LVO layers and locally imaging their interlayer spacings. Further, electrochemical cycling of the cation-assembled LVO/rGO heterostructures in Li-ion cells with a non-aqueous electrolyte revealed that increasing the rGO content led to improved cycling stability and rate performance, despite slightly decreased charge storage capacity. The heterostructures with 0, 10, 20, and 35 wt % rGO exhibited capacities of 237, 216, 174, and 150 mAh g-1, respectively. Moreover, the LVO/rGO-35 wt % and LVO/rGO-20 wt % heterostructures retained 75% (110 mAh g-1) and 67% (120 mAh g-1) of their initial capacities after increasing the specific current from 20 to 200 mA g-1, while the LVO/rGO-10 wt % sample retained only 48% (107 mAh g-1) of its initial capacity under the same cycling conditions. In addition, the cation-assembled LVO/rGO electrodes exhibited enhanced electrochemical stability compared to electrodes prepared through physical mixing of LVO and GO nanoflakes in the same ratios as the heterostructure electrodes, further revealing the stabilizing effect of a 2D heterointerface. The cation-driven assembly approach, explored in this work using Li+ cations, was found to induce and stabilize the formation of stacked 2D layers of rGO and exfoliated LVO. The reported assembly methodology can be applied for a variety of systems utilizing 2D materials with complementary properties for applications as electrodes in energy storage devices.

A novel magnetic AgVO3/rGO/CuFe2O4 hybrid catalyst for efficient hydrogen evolution and photocatalytic degradation

A superior semiconductor material with efficient charge separation and easy reuse could be a promising route for efficient photocatalytic hydrogen evolution and pollutant degradation. AgVO3 is one of the best visible light active materials which has attracted much attention for several biological and environmental applications. In the aim of enhancing its stability and recyclability a novel AgVO3/rGO/CuFe2O4 heterojunction was prepared by hydrothermal method for hydrogen generation (H2) and 4-nitrophenol (4-NP) degradation as well. The composite was well characterized by XRD, SEM, HR-TEM, XPS and VSM. The morphological images suggested the rod shaped AgVO3 and irregular shaped CuFe2O4 are unevenly distributed on reduced graphene oxide (rGO) layers. The hydrogen evolution results indicated that the composite showed around 8.937 mmol g−1h−1 of H2 generation which was ∼2.3 times and ∼9.2 times higher than pure AgVO3 (3.895 mmol g−1h−1) and CuFe2O4 (0.96 mmol g−1h−1) respectively. The 4-NP degradation efficiency of the prepared composite was observed as 94.7% (k = 0.01841 min−1) which is much higher than the AgVO3 (66.3%) and CuFe2O4 (38.2%) after 4 h of irradiation. The higher efficiency could be attributed to the heterojunction formation and faster charge separation. The radical trapping results indicated that the •OH, O2•− and photogenerated h+ are the main species responsible for efficient activity. The AgVO3/rGO/CuFe2O4 heterojunction showed 49.6 emu/g of saturation magnetization and confirms that it could be easily separated with an external magnet, and showed 85.3% of degradation efficiency even after 6 recycles which indicated its higher stability and recyclability. Thus, our study provides new insight into hydrogen generation and phenol degradation using AgVO3 based recyclable composites.

Self-Assembled Construction of Robust and Super Elastic Graphene Aerogel for High-Efficient Formaldehyde Removal and Multifunctional Application.

Simultaneously achieving exceptional mechanical strength and resilience of graphene aerogel (GA) remains a challenge, while GA is an ideal candidate for formaldehyde removal. Herein, flexible polyethyleneimine (PEI) is grafted chemically onto carbon nanotube (CNT) surface, and CNT-PEI@reduced GA (rGA) is fabricated via hydrothermal self-assembly, pre-frozen, and hydrazine reduction process. Introducing CNT-PEI contributes to well-interconnected/robust 3D network construction by connecting reduced graphene oxide (rGO) nanosheets through enhancing cross-linking, while entangled CNT-PEI is intercalated into rGO layers to avoid serious restacking of sheets, producing larger surface area and more formaldehyde adsorption sites. Ultralight CNT-PEI@rGA exhibits extreme high strength (276.37 kPa), reversible compressibility at 90% strain, and structural stability, while FA adsorption capacity reached 568.41 mg g-1 , ≈3.28 times of rGA, derivable from synergistic chemical-physical adsorption effect. Furthermore, CNT-PEI@rGA is ground into powder for first preparing polyoxymethylene (POM)/CNT-PEI@rGA composite, while formaldehyde emission amount is 69.63%/73.96% lower than that of POM at 60/230 °C. Moreover, CNT-PEI@rGA presents outstanding piezoresistive-sensing and thermal insulation properties, exhibiting high strain sensitivity, wide strain detection range, and long-term durability.

Synthesis, Characterization, and Electrochemical Performance of Reduced Graphene Oxide-Metal (Cu,Zn)-Oxide Materials

The reduced graphene oxide (rGO) and metal (Cu,Zn)-oxide composites were prepared using a one-step hydrothermal technique. The role of (Cu,Zn)-oxide on the physical and electrochemical properties of the composite was investigated. The composite consists of various shapes of ZnO nanoflowers and micro-spheres, as well as Cu-oxide nanoflakes and octahedron-like shapes. The (Cu,Zn)-oxides were formed in between the rGO layers and observed in the rGO-ZnO, rGO-CuO, and rGO-CuO-ZnO composites. The presence of ZnO, CuO, and rGO within the composite structure is also confirmed by the analyses of crystal structure, microstructure, and surface functional groups. Some excess impurities remaining from the surfactant give considerable differences in the electrochemical performance of the composites. The specific capacitance values of the rGO, rGO-ZnO, rGO-CuO, rGO-(0.5CuO-0.5ZnO), and rGO-(0.25CuO-0.75ZnO) composites are 9.32, 58.53, 54.14, 25.21, and 69.27 F/g, respectively. The formation ofa double metal-oxide structure as well as their insertion into the rGO sheet can significantly improve the electrochemical properties of the supercapacitor.

Facile fabrication of AgVO3/rGO/BiVO4 hetero junction for efficient degradation and detoxification of norfloxacin

In the recent past, the development of efficient materials for degradation and detoxification of antibiotics has gained more attention in wastewater treatment process. As a visible light active material AgVO3 has attracted much concern in environmental remediation. To improve its efficiency and stability, a novel heterojunction was prepared by combining AgVO3 with rGO and BiVO4 through a hydrothermal method. The prepared AgVO3/rGO/BiVO4 composite was further utilized for effective detoxification of Norfloxacin (NFC) antibiotic. The morphological analysis revealed the clear rod shaped AgVO3 and leaf like BiVO4 that are evenly distributed on reduced graphene oxide (rGO) layers. The visible light absorbance and the catalytic activity of AgVO3/rGO/BiVO4 was dramatically improved compared to pure AgVO3 and BiVO4. From the results it showed that the degradation efficiency of AgVO3/rGO/BiVO4 (∼96.1%, k = 0.01782 min−1) was 2.5 times higher than pure AgVO3 and 3.4 times higher than the pure BiVO4 respectively towards NFC after 90 min. The higher efficiency could be attributed to the heterojunction formation and faster charge separation. The radical trapping experiments results indicated that the •OH, and O2•− are the main species responsible for degradation. The degradation products of NFC were analysed through ESI-LC/MS and pathway was proposed. Furthermore, the toxicity assessment of pure NFC and its degradation products was studied using E. coli as the model bacteria through colony forming unit assay and the results indicated the efficient detoxification was attained during the degradation process. Thus, our study provides new insight into detoxification of antibiotics using AgVO3 based composites

Electron paramagnetic resonance

We have studied literature from investigation of the impact of Mechanothermal effects in the creation of defect structures in dispersed systems after prolonged mechanical treatment of ZnO powders. This work illustrates some potential applications of electron paramagnetic resonance. EPR application beginning of a variety of paramagnetic processes is based on the knowledge that this centre happens when some materials are mechanically treated. These facilities can act as EPR sondes of various thermal processes that appear when systems are being mechanically treated consisting of ZnO.Zn was evaporated in air, dry and humid argon flow, and dry and humid nitrogen flow to create Zno tetrapod nanostructures. SEM, X-ray diffraction, photoluminescence, photoluminescence excitation (PLE) spectroscopy (at various temperatures), and electron paramagnetic resonance (EPR) spectroscopy at −160 ℃ and room temperature have all been used to explore the characteristics. It is discovered that the fabrication conditions have a considerable impact on the acquired EPR and PL spectra. while some of the samples exhibit a g = 1.96 EPR signal. We used microwave processing to create and mix ZnO nanoparticles (ZnO-NPs) with various amounts of graphene oxide (GO) (10 %, 20 %, and 30 %).The process delivered evenly distributed ZnO-NPs onto and between the rGO layers.(GZCs). The UV–vis absorption, PL emission, defect states of the ZnO, EPR signals, photo-electrochemical reaction, and charge transfer properties were all influenced by the annealing temperature and graphene oxide content. The GZCs' HRTEM microscopy pictures revealed interpenetrating structures and vacancy flaws that were easily seen. The findings showed that following hybridization with GO, the defect sites (Zn interstitials, oxygen vacancy, ionised oxygen vacancy, and oxygen interstitials) greatly decreased. The GZC-10photo-conversion 10 %'s efficiency(ŋ= 13.1 × 10-3%) We have studied literature from Ref.[1]which show that.

Development of ZnO/SnO2/rGO hybrid nanocomposites for effective photocatalytic degradation of toxic dye pollutants from aquatic ecosystems

The impact of ZnO/SnO2/reduced graphene oxide nanocomposites (ZnO/SnO2/rGO NCs) for improved photocatalytic degradation of organic dye pollution is examined in this study. The developed ternary nanocomposites had a variety of characteristics that were detected, such as crystallinity, recombination of photogenerated charge carriers, energy gap, and surface morphologies. When rGO was added to the mixture, the optical band gap energy of ZnO/SnO2 was lowered, which improved the photocatalytic activity. Additionally, in comparison to ZnO, ZnO/rGO, SnO2/rGO samples, the ZnO/SnO2/rGO nanocomposites demonstrated exceptional photocatalytic effectiveness for the destruction of orange II (99.8%) and reactive red 120 dye (97.02%), respectively after 120 min exposure to sunlight. The high electron transport properties of the rGO layers, which make it feasible to efficiently separate electron-hole pairs, are attributed to the enhanced photocatalytic activity of the ZnO/SnO2/rGO nanocomposites. According to the results, synthesized ZnO/SnO2/rGO nanocomposites are a cost-efficient option for removing dye pollutants from an aqueous ecosystem. Studies show that ZnO/SnO2/rGO nanocomposites are effective photocatalysts and may one day serve as the ideal material to reduce water pollution.

Graphene oxide nano-layers functionalized/reduced by L-Citrulline/Pectin bio-molecules for epoxy nanocomposite coating mechanical properties reinforcement

In this work, graphene oxide (GO) was reduced/modified by an eco-friendly route using L-Citrulline molecules extracted from the watermelon rind. Before and after the modification/reduction process, the rGO layers were characterized by different spectroscopy techniques. In addition, the mechanical properties of the epoxy-rGO reinforced coatings were evaluated by tensile and dynamic mechanical thermal analysis (DMTA) tests. The characterization results have demonstrated that the GO nanosheets were successfully reduced/modified by the extracted compounds. DMTA analysis showed that the values of storage modulus at glassy and rubbery regions for the neat epoxy sample incorporated with the rGO nanosheets were increased by about 39 % and 97 %, respectively. Moreover, the glass transition temperature (Tg) was increased from 76.8 °C for the neat epoxy (EP) to 84.0 °C for the EP/modified-reduced GO nanocomposite. Tensile tests showed that the values of tensile strength, maximum strain, elastic modulus, and toughness of the epoxy-based coating were respectively increased by about 142 %, 266 %, 46.7 %, and 388 % after incorporation of the rGO nanosheets compared to the EP sample.

Ag nanoparticles anchored reduced graphene oxide sheets@nickel oxide nanoflakes nanocomposites for enhanced capacitive performance of supercapacitors

In this work, ternary nanocomposite of silver nanoparticles embedded on the surface of few layered reduced graphene oxide coated nickel oxide (Ag-rGO@NiO) was successfully fabricated as electrode material for high performance supercapacitor applications. NiO nanoflakes was prepared by hydrothermal route while coating of few layered rGO and subsequent silver anchoring was done by chemical methodology. The morphological analysis by scanning electron microscopy and transmission electron microscopy showed NiO nanoflakes coated by rGO/distributed on rGO substrate with scattered Ag nanoparticles. The elemental composition and distribution was confirmed by energy-dispersive X-ray (EDX) and Raman spectroscopy. The electrochemical measurements showed that the fabricated electrode of Ag-rGO@NiO is suitable electrode material and can enhance the capacitive performance of supercapacitors due to its high capacitive value (1230 Fg−1) in contrast to the binary rGO@NiO (337.5 F g−1) and bare NiO flakes (145 F g−1) at current density of 1 A g−1. The enhancement in the capacitive value of Ag-rGO@NiO composite was mainly attributed to the highly conductive rGO sheets and Ag nanoparticles where rGO sheets provided conductive path and Ag created new channels for the electron transfer. Furthermore, it also showed excellent cyclic stability as it retained 88.5 % of its initial capacitive value even after 3000 cycles as well as showed excellent energy density of (27.33 Wh kg−1) at power density (200.073 W kg−1).

Enhanced photoelectrochemical response of reduced graphene oxide covered inexpensive TiO2-BiFeO3 composite photoanodes

We show enhanced photoelectrochemical response of reduced graphene oxide covered inexpensive TiO2-BiFeO3 composite photoanodes for photoelectrochemical water splitting reaction. The photoelectrochemical activity of TiO2-BiFeO3 composite electrode is increased by creating heterojunction of TiO2-BiFeO3 and rGO. Structural, optical and morphological analysis of pristine and composite samples was done by characterizing them using X-ray diffraction, UV–vis spectrometry and scanning electron microscopy. The photoelectrochemical water splitting reaction revealed that composite TiO2-BiFeO3 with 20 wt.% BiFeO3 has higher photocurrent density. Further this composite electrode with rGO layer exhibits more than tenfold photocurrent density at onset and as well as higher potential. Graphene oxide layer acts as rich source of electrons caused better separation of the photogenerated electron hole pairs at heterojunction. Finally, this system shows high photocurrent density of 3.5 mA cm−2 at 0.95 V/Ag/AgCl with good stability under light conditions.

Mitigating the Capacity Degradation by Ion-Electron-Conducting Dual-Layer Coating on a Layered Oxide Cathode Material for Sodium Ion Batteries

A high-capacity and long-life layered P2-Na0.7[Ni0.35Mn0.60Co0.05]O2 (NMC) cathode material, dually coated with Na-ion-conducting Na2SiO3 and electron-conducting RGO, has been successfully synthesized and tested for half-cell as well as full-cell applications. The first coating layer of Na2SiO3 provides a three-dimensional (3D) diffusion channel for Na-ion migration, while the second coating layer of RGO offers the electron-conducting pathways to enhance the charge transfer. Moreover, Si4+ migration in the NMC lattice during Na2SiO3 coating causes the enhancement in the interlayer spacing, which significantly increases the Na+-diffusion rate. The structural, morphological, electronic, and electrochemical analyses of the prepared cathode materials have been performed. The synergic effect of dual-layer modification and Si4+ doping not only protects the cathode particles but also improves the Na-ion kinetics as well as charge transfer rate, resulting in superior electrochemical performance. The dually surface-modified cathode shows a maximum discharge capacity of 171 mAh g–1 at ∼13 mA g–1 and 62 mAh g–1 at ∼1300 mA g–1 with 76% capacity retention and ∼98% coulombic efficiency over 500 cycles at 1C rate (260 mA g–1) for the half cell, while for the full cell, it delivers an initial discharge capacity of ∼91 mAh g–1 and 66% capacity retention over 1000 cycles at 1C rate.

Recovery of rare earth elements from mine wastewater using biosynthesized reduced graphene oxide

Recycling rare earth elements (REEs) from sources of secondary waste such as REEs mine wastewater has emerged as a sustainable approach with both waste reuse and wastewater processing. In this study, green reduced graphene oxide (G-rGO) was prepared utilizing green tea extract with the advantages of being environmentally friendly, sustainable, and low cost. To understand how G-rGO functions, it was compared to commercial reduced graphene oxide (rGO), and the efficiencies in adsorbing Y(III) were 91.6% and 11.9%, respectively. This indicated there is a synergistic adsorption between the capping layer of G-rGO and rGO alone. G-rGO and rGO were characterized before and after exposure to Y(III). This comparison indicated that Y(III) was adsorbed on the surface of G-rGO through complexation and electrostatic interaction. The adsorption kinetics best fit the pseudo-second-order model and the Langmuir model isotherm model, with adsorption capacities of 24.54 mg g−1. A probable adsorption mechanism of Y(III) by G-rGO was proposed, involving electronic complexation, electrostatic adsorption and ion exchange. Furthermore, the adsorption efficiencies of G-rGO for Y(III), Ce(III) and Zn(II) in mine wastewater were 22.1%, 89.1% and 14.6%, respectively. These results demonstrate that G-rGO has great potential in the recovery of REEs from mine wastewater.

A novel approach to fabricate layered RGO/Cu composites with excellent mechanical properties

The preparation of copper matrix composites with high graphene content is difficult, facing the problem of graphene agglomeration. This study proposed a layer-by-layer electrodeposition method to obtain the reduced graphene oxide/copper (RGO/Cu) composite with a layered structure. It was found that the layered distribution of RGO avoided the occurrence of agglomeration effectively, which was conducive to the excellent mechanical strength and toughness of the composite. The strength of the RGO/Cu composite increased with the number of layers, and the tensile strength of the 29-layer composite was 34.2 % higher than that of pure copper. While, its elongation remained at the same level as that of pure copper. The toughening and strengthening mechanism of layered RGO in the composite was analyzed by molecular dynamics simulation. Confinement on crack propagation and strain energy consumption by sliding of layered RGO were identified as the reason for maintaining the high toughness of the composite, and stress transfer, grain refinement and dislocation strengthening were contributed to the high tensile strength.

Synthesis, Characterization, and Evaluation of Antimicrobial Efficacy of Reduced Graphene-ZnO-Copper Nanocomplex.

The prevalence of antibiotic-resistant diseases drives a constant hunt for new substitutes. Metal-containing inorganic nanoparticles have broad-spectrum antimicrobial potential to kill Gram-negative and Gram-positive bacteria. In this investigation, reduced graphene oxide-coated zinc oxide-copper (rGO@ZnO-Cu) nanocomposite was prepared by anchoring Cu over ZnO nanorods followed by coating with graphene oxide (GO) and subsequent reduction of GO to rGO. The synthesized nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy, elemental analysis, and elemental mapping. Morphologically, ZnO-Cu showed big, irregular rods, rectangular and spherical-shaped ZnO, and anchored clusters of aggregated Cu particles. The Cu aggregates are spread uniformly throughout the network. Most of the ZnO particles were partially covered with Cu aggregates, while some of the ZnO was fully covered with Cu. In the case of rGO@ZnO-Cu, a few layered rGO sheets were observed on the surface as well as deeply embedded inside the network of ZnO-Cu. The rGO@ZnO-Cu complex exhibited antimicrobial activity against Gram-positive and Gram-negative bacteria; however, it was more effective on Staphylococcus aureus than Escherichia coli. Thus, rGO@ZnO-Cu nanocomposites could be an effective alternative against Gram-positive and Gram-negative bacterial pathogens.

Enhanced rate capability of S@Co3O4 microsphere wrapped by rGO for cathodes of lithium-sulfur batteries

S@Co3O4/rGO (SCG) composite was synthesized via a readily solvothermal method and subsequent thermal treatment for cathodes of lithium-sulfur (Li-S) batteries, in which Co3O4 hollow microsphere used as a sulfur host has been initially wrapped by conductive reduced graphene oxide (rGO) network. Benefited from polar Co-S bond forming strong adsorption with polysulfides and hollow structure providing void spaces for volumetric expansion, Co3O4 additive effectively alleviates such issues as shuttle effect and electrode pulverization/failure. Moreover, rGO layer covering onto surface of Co3O4 microsphere further increases electrical conductivity and structural stability of electrode. As a result, SCG composite exhibits superior electrochemical performances with a high specific capacity of 1131.6 mAh g−1 at 0.2 C, and an enhanced rate capability tolerating a high current density of up to 5 C. The design strategy on composition and structure of cathode in this work will provide a novel route for achieving high-energy Li-S batteries.

Reduced graphene oxide/polyurethane coatings for wash-durable wearable piezoresistive sensors

Graphene-based functional coatings for cotton textiles were realized through an easy dip-coating procedure. Cotton fabrics were coated with a reduced graphene oxide (rGO) layer and then protected with a very thin polyurethane (PU) layer that does not affect the flexibility and the hand of the pristine cotton. The application of the rGO coating induces electrical conductivity to the fabric and the application of the PU phase increases the durability of the coatings, that show very stable surface resistivity after 10 washing cycles performed at temperatures up to 40 °C. Furthermore, the rGO and rGO/PU coated fabrics show good comfort properties, increased thermal conductivity and breathability with respect to cotton. In particular, the realized coatings allow to confine the heat transfer in correspondence of a localized heating source, which is very interesting for thermal therapy applications. Finally, the rGO/PU coated fabrics present a piezoresistive behaviour characterized by very stable electrical response to applied stretching up to 50% deformation, high sensitivity especially at low deformations with gauge factor values up to 11.7 and fast response time down to 500 ms when stretched at 100 mm/min rate at 2.5% strain. Overall, the results demonstrate that rGO/PU coated fabrics are very promising wash-durable electrically conductive e-textiles with improved comfort, enhanced thermal conductivity for possible thermal therapy applications, and piezoresistive properties for sensing applications as human motion monitoring.

Enhancement of functional surface and molecular dynamics at Pt-rGO by spacer 1,6-hexanediamine for precise detection of biomolecules: uric acid as a specimen

Hexanediamine (HA) was incorporated in rGO-platinum (Pt) matrices to obtain HA-rGO-Pt with an improved molecular migration track. The HA-rGO-Pt could detect very low concentrations uric acid as the uric acid could migrate through the layers of rGO.

Effect of Concentration and pH of GO Solutions on the Pd-rGO@NF Electrode Prepared by Spontaneous Reduction for H2O2 Reduction in Acidic Media

The Pd-rGO@NF composite electrodes were prepared by a simple and green two-step process of spontaneous reduction. Graphene oxide (GO) was first reduced directly by nickel foam (NF) to form a rGO@NF composite substrate. The effect mechanism of GO concentration and pH on the morphology and properties of rGO@NF was investigated by SEM, TEM, XRD and Raman. Increasing GO and H[Formula: see text] concentration can improve the reduction rate, deposit amount and reduction degree of GO on the surface of Ni foam. A uniform, compact and multi-fold rGO coating formed on the Ni skeleton surface at the GO concentration of 2[Formula: see text]g[Formula: see text]L[Formula: see text] and pH of 7. Then, Pd[Formula: see text] was reduced by rGO on the NF surface to construct the 3D Pd-rGO@NF composite electrodes, which showed superior catalytic activity and stability for H2O2 reduction in acidic media compared to Pd-NF due to a higher surface area and better anti-acid corrosion from rGO layers.

Influence of Graphene Sheets Accumulation on Optical Band Gap Enhanced Graphite Exfoliation

Recently, graphene has been adopted to replace other expansive materials in various devices that perform numerous functionalities in many industrial fields. Meanwhile, researchers are still investigating the amazing properties of graphene. Herein, reduced graphene oxide (rGO) has been successfully exfoliated directly using a graphite rod in a modified electrolyte including a table salt as a co-electrolyte. The structure of graphene obtained by using exfoliation methods shows a low ratio of O/C and confirms the high crystallinity of rGO. The thickness of rGO was adjusted during the drying of the drops of rGO solution and obtained about an 8-80 nm rGO thick. The increased O/C ratio and crystallinity enhancement could be attributed to the quantum confinement effect. Further investigations to estimate the decay constant of the optical band gap during the thinning of the rGO layers show that the optical band gap was associated with thicknesses of the rGO at a decay constant of 0.3367±0.00205. These results would be crucial in several optical applications that depend on the thicknesses and the band gap.