Two-dimensional Reduced Graphene Oxide Research Articles

SnOx embedded into 3D RGO network for enhanced photoconductive performance

In this study, tin dioxide with vacancies (SnOx) was compounded with three-dimensional reduced graphene oxide (3D RGO) to obtain SnOx/3D RGO. The morphology, optical properties and structural composition of SnOx/3D RGO were analyzed by a series of techniques, and the photoconductive properties of the SnOx/3D RGO composites with different mass fractions of RGO were investigated. The photocurrent density of SnOx/3D RGO at 3D RGO mass fraction of 1.5 % reached a maximum value of 2.77 × 10−4 A/cm2, which was about twice and 1.2 times as large as that of SnOx and SnOx/2D RGO (two-dimensional reduced graphene oxide), respectively. In the linear scanning voltammetry and Mott-Schottky analysis results, SnOx/3D RGO exhibited the highest photocurrent (6.34 × 10−3 A/cm2) intensity at 1.0 V bias and the largest carrier density (2.61 × 1021cm−3). This was due to the fact that RGO played a charge transfer role in the composite material in both 2D and 3D structures. In contrast, the porous 3D RGO could connect separate lamellae, which prevented the aggregation of layers and enhanced the electron transfer, thus exhibiting superior performance than 2D graphene.

Reduced graphene oxide-functionalized polymer microneedle for continuous and wide-range monitoring of lactate in interstitial fluid

Despite substantial developments in minimally invasive lactate monitoring microneedle electrodes, most such electrode developments have focused on either sensitivity or invasiveness while ignoring a wide range of detection, which is the most important factor in measuring the normal range of lactate in interstitial fluid (ISF). Herein, we present a polymer-based planar microneedle electrode fabrication using microelectromechanical and femtosecond laser technology for the continuous monitoring of lactate in ISF. The microneedle is functionalized with two-dimensional reduced graphene oxide (rGO) and electrochemically synthesized platinum nanoparticles (PtNPs). A particular quantity of Nafion (1.25 wt%) is applied on top of the lactate enzyme to create a diffusion-controlled membrane. Due to the combined effects of the planar structure of the microneedle, rGO, and membrane, the biosensor exhibited excellent linearity up to 10 mM lactate with a limit of detection of 2.04 μM, high sensitivity of 43.96 μA mM−1cm−2, a reaction time of 8 s and outstanding stability, selectivity, and repeatability. The feasibility of the microneedle is evaluated by using it to measure lactate concentrations in artificial ISF and human serum. The results demonstrate that the microneedle described here has great potential for use in real-time lactate monitoring for use in sports medicine and treatment.

Interface and magnetic-dielectric synergy strategy to develop Fe3O4-Fe2CO3/multi-walled carbon nanotubes/reduced graphene oxide mixed-dimensional multicomponent nanocomposites for microwave absorption

Interfacial and/or magnetic-dielectric synergistic effects are important avenues to boost microwave absorption properties. In order to simultaneously utilize these effects, we elaborately designed mixed-dimensional Fe3O4-FeCO3/multi-walled carbon nanotubes (MWCNTs)/reduced graphene oxide (RGO) multicomponent nanocomposites (MCNCs) in large scale via a facile process of hydrothermal and freeze-drying. The microstructural investigation revealed that two-dimensional RGO, one-dimensional MWCNTs and zero-dimensional Fe3O4-FeCO3 nanoparticles were well bounded to generate the typical mixed-dimensional structure. By controlling the amounts of initial reactants, the Fe3O4-FeCO3/MWCNTs/RGO MCNCs displayed improved impedance matching features, polarization and conduction loss abilities, which lead to the evidently improved electromagnetic absorption properties. The Fe3O4-FeCO3/MWCNTs/RGO MCNCs simultaneously exhibited excellent absorption ability, large absorption bandwidth, low density and thin matching thickness. Generally, this work not only proposed an effective route to make the best of magnetic-dielectric synergy and interfacial strategy for exploiting novel microwave absorption materials, but also presented a simple approach to synthesize magnetic MWCNTs/RGO-based mixed-dimensional MCNCs.

Sunlight-driven photocatalytic degradation of Norfloxacin antibiotic in wastewater by ZnSe microsphere functionalized RGO composite

The release of hazardous pollutants into the water, such as dyes, phenolic compounds, pesticides, different heavy metals, and antibiotics is the primary cause of environmental pollution. The solar energy-based photocatalysis technique has the potential to eliminate pollutants from the aquatic environment. ZnSe is a significant and commendable II-VI group photocatalyst having 2.82 eV direct band gap energy. Its performance towards degrading antibiotics in the presence of light was improved by anchoring it on the Reduced graphene oxide (RGO) matrix. Solution-processable RGO-ZnSe composites were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Several spectroscopic studies like Raman spectroscopy, ultraviolet-visible spectroscopy, and photoluminescence spectroscopy were employed to illustrate the optical properties of the composites. The findings demonstrate that the ZnSe microsphere was supported effectively onto the two-dimensional RGO matrix. The performance of as-synthesized RGO-ZnSe composites was assessed based on the photocatalytic degradation of the antibiotic Norfloxacin in the presence of simulated solar light. An optimized RGO-ZnSe composite degrades approximately 83.5% of Norfloxacin in 40 min, while controlled-ZnSe photocatalysis only yields 33% in an identical experimental condition. The optimized RGO-ZnSe achieves the highest degradation reaction rate constant (k) of Norfloxacin (k = 0.057 min−1), and the k value is 4.38 times greater compared to the controlled-ZnSe microsphere. The light-dependent catalytic degradation mechanism was examined by employing scavenger experiments which gave away the responsible reactive radicals. Our results establish that the photo-generated hole has the leading role in the degradation of Norfloxacin in our system. In addition to that, the oxide radical and hydroxyl radical has also an important role in the degradation of Norfloxacin under our experimental condition. The finding suggests that the addition of RGO has enhanced photocatalytic performance and cyclic stability by preventing photo-generated electron-hole pair recombination. The photocatalytic oxidative deactivation mechanism of the Norfloxacin antibiotic was proposed. Our study offers new perceptiveness for the design of efficient solution-processable solar light-responsible photocatalysts for environmental pollution remediation.

Wood-inspired elastic and conductive cellulose aerogel with anisotropic tubular and multilayered structure for wearable pressure sensors and supercapacitors

Cellulose nanofiber (CNF) aerogels hold considerable potential in wearable devices as pressure sensors and flexible electrochemical energy storage. However, the undirectional assembly of CNFs results in poor mechanical performance, which limits their application in structural engineering. In this study, we propose an anisotropic aerogel with both elastic and conductive properties inspired by the micro-nanostructure of natural wood. One-dimensional TEMPO cellulose nanofibers (TOCNF) were utilized as structural building blocks, while two-dimensional reduced graphene oxide (rGO) served as the electron transfer platform, owing to their high mechanical strength. The directionally aligned tubular structure composed of multilayered sheets was formed through rapid unidirectional freezing and subsequent steam heating reduction. These structures efficiently transferred stress throughout the porous skeleton, resulting in TOCNF-rGO aerogels with high compressibility and excellent fatigue resistance (2000 cycles at 60 % strain). The aerogel also exhibited high sensitivity, wide detection range, relatively fast response, and excellent compression cycle stability, making it suitable for accurately detecting various human biological and motion signals. Additionally, TOCNF-rGO can be assembled into a flexible all-solid-state symmetric supercapacitor that delivers excellent electrochemical performance. It is expected that this biomass-derived aerogel will be a versatile material for flexible electronic devices for energy conversion and storage.

Three-dimensional RGO/CNTs/GDY assembled microsphere: Bridging-induced electron transport enhanced microwave absorbing mechanism

As a new type of carbon allotrope, graphdiyne (GDY) is a promising material with highly conjugated conductive structure and excellent chemical stability. This indicates the great potential of GDY as a microwave absorbing material. Herein, we realize the simple one-step assembly of zero-dimensional GDY particles, one-dimensional carbon nanotubes (CNTs) and two-dimensional reduced graphene oxide (RGO) through ultrasonic spray method and carbonization technology, and obtained RGO/CNTs/GDY microspheres (RCG) with three-dimensional porous structure. CNTs can bridge RGO and GDY, forming a complete conductive network and providing pathways for electron migration. Benefiting from the unique three-dimensional assembly structure, high specific surface area, suitable impedance matching and strong dissipation ability, RCG shows excellent microwave absorption performance. By adjusting the assembly ratio and optimizing the filler loading, RCG-2 (RGO: CNTs: GDY = 4:1.5:1, 17.5%) with outstanding microwave absorption properties is obtained. The minimum reflection loss (RLmin) reached −51.8 dB at the matching thickness of 1.6 mm and the maximum effective absorption bandwidth (EAB) covered 5.4 GHz. The novel loss mechanism of bridge-induced electron transfer enhanced microwave absorption is proposed. It provides a new way to manufacture advanced microwave absorbers.

Improved mechanical-physical performances of copper composites with reduced graphene oxide and carbonized polymer dots as multi-scale synergetic reinforcements

The development of high-performance (structure-function integration) Cu matrix composites have become a focus by introducing the novel hybrid carbon nanomaterials and giving full play to the synergistic effect. It is a great challenge to homogeneously disperse the ex-situ nano-filler within matrix for excellent performances. In this study, the two-dimensional reduced graphene oxide (RGO) and zero-dimensional carbonized polymer dots (CPD) were incorporated with Cu-based powders by the molecular level mixing (MLM) and high-energy ball milling (HBM) methods, respectively. Results revealed that RGO (MLM)/CPD (HBM)-Cu bulk composites sintered at 650 °C displayed higher ultimate tensile strength (367 MPa) and better failure strain (∼30%) as compared with pure Cu (MLM/HBM). Meanwhile, the electrical conductivity of RGO (MLM)/CPD (HBM)-Cu was almost equal to that of pure Cu (93.74% IACS), exhibiting a promising prospect in applications as advanced multifunctional structural materials. It was well proved that the interface strength of RGO-Cu and the dispersibility of hybrid reinforcements were improved by the incorporation of CPD, which further enhanced the synergistic effects of (CPD + RGO) and achieved better mechanical-physical performances.

An efficient broadband white-light photodetector: Combining visible-light-active ferroelectrics with 2D conductive intermediary RGO

Hitherto, “smart” functional bismuth ferrite (BFO) has triggered intensive research to develop novel visible-light photodetectors to substitute silicon-based detectors. However, current BFO-based detectors still fall short of the requirements for white-light (WL) detection due to unsatisfactory sensitivity and response speed. In pursuit of simple and efficient BFO-based device paradigm, we propose an effective strategy to fill empty space among metallic silver electrode dot-matrix with continuous transparent conductive material by decorating reduced graphene oxide (RGO) nanosheets on top of semiconducting layer. The hybrid device structures, BFO/RGO/Ag and BFO/NiO/RGO/Ag, are systematically explored in comparison to pure BFO. The RGO sheet stands out as qualified transparent conductive intermediary to disrupt the potential barrier caused by ubiquitous metal-semiconductor contact. It is the synergistic action of RGO facilitating charge collection and heterostructure pattern of BFO/NiO that eventually contribute to boost optical-electrical response performances of BFO/NiO/RGO structure. Accordingly, the optimized response time constants of photocurrent rising and decay are lowered down to 16.01 ms and 11.76 ms, respectively. Such response speed can exceed most of BFO-based counterparts especially in the WL-detection. Consequently, we deliver a green and facile approach to push forward the high-speed WL photoelectric detection by combining visible-light-active ferroelectrics BFO with two-dimensional conductive RGO.

3D flower-like β-Ni(OH)2 as an electrochemical sensor for sensitive determination of serotonin

Morphology studies of nanomaterials have attracted considerable attention in the field of catalysis because of their distinguishable properties and performances. In this context, we have developed a β-Ni(OH) 2 decorated para phenylenediamine (p-PDA) functionalized reduced graphene oxide (RGO) (denoted as RGO/p-PDA/β-Ni(OH) 2 ) electrochemical sensor for detecting serotonin (5-HT). The growth mechanism of a three-dimensional (3D) flower-like β-Ni(OH) 2 based on two-dimensional (2D) RGO nanosheets assembled with petals of the flower was investigated by field emission scanning electron microscopy (FESEM). The 3D flower-like morphology significantly enhanced the surface area and conductivity of RGO/p-PDA/β-Ni(OH) 2 modified glassy carbon electrode (GCE). The electrochemical performance of the material was studied using different techniques, including cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectra (EIS), and amperometry. The higher oxidation current of RGO/p-PDA/β-Ni(OH) 2 /GCE was -134.8 µA at 0.383 V ( vs Ag / AgCl ) in CV. In amperometry, the modified electrode provided a wide linear range (5-325 µM), low limit of detection (0.0462 µM), high sensitivity (339.46 µA mM -1 cm -2 ), and fast response time (<2 s). Furthermore, the as-prepared electrode demonstrated high selectivity, long-term stability, reproducibility, and repeatability. The much better recovery range of urine (109.83-111.05%) than drinking water (98.15-101.02%) implied that the sensor is effective for 5-HT determination. • Thermally and chemically stable nanocomposite. • It demonstrated 3D flower-like morphology. • It responded within 2 s in CA. • Higher recovery range for urine sample. • It showed high selectivity in presence of DA and AA.

Multifunctional NiCo@RGO/SWNTs foam with oriented pore structure for excellent electromagnetic interference shielding

Constructing multifunctional material toward advanced electromagnetic interference (EMI) shielding has become a development trend. Carbon-based foams with excellent EMI shielding performance and structural stability for various environments are being widely studied. Here, an oriented pore structure was assembled with a carbon-based conductive skeleton, consisting of single-walled carbon nanotubes (SWNTs) and two-dimensional reduced graphene oxide (RGO), for facilitating the electromagnetic wave (EMW) to be multilevelly reflected in the confined space. In addition, magnetic NiCo nanoparticles were introduced to further improve the shielding performance by enhancing the magnetic loss. The as-prepared NiCo@RGO/SWNTs foam (NiCo@RSF) exhibited an exceptional EMI shielding effectiveness (SE) of 105 dB at the whole X band (8.2–12.4 GHz) with an ultralow density (0.0135 g cm−3). Moreover, the foam possessed extraordinary heat insulation and flame-retardant properties. Overall, the lightweight multifunctional foam with an oriented pore structure is thus promising for applications in advanced EMI shielding and other specific areas.

Rationally engineering a hierarchical porous carbon and reduced graphene oxide supported magnetite composite with boosted lithium-ion storage performances

Ferric gallate (Fe-GA), an ancient metal–organic framework (MOF) material, has been recently employed as an eco-friendly and cost-effective precursor sample to synthesize a porous carbon confined nano-iron composite (Fe/RPC), and the Fe element in the Fe/RPC sample could be further oxidized to Fe3O4 nanocrystals in a 180 °C hydrothermal condition. On this foundation, this work reports an optimized approach to engineering a hierarchical one-dimensional porous carbon and two-dimensional reduced graphene oxide (RGO) supporting framework with Fe3O4 nanoparticles well dispersed. Under mild hydrothermal condition, the redox reaction between metal iron atoms from Fe/RPC and surface functional radicals from few-layered graphene oxide sheets (GO) is triggered. As a result, reinforced microstructure and improved atomic efficiency have been achieved for the Fe3O4@RPC/RGO sample. The homogeneously dispersed Fe3O4 nanoparticles with controlled size are anchored on the surface of the larger sized RGO coating layers while the smaller sized RPC domains are embedded between the RGO sheets as spacer. Challenges including spontaneous aggregation of RPC, over exposure of Fe3O4 nanoparticles and excessive restacking of RGO have been significantly inhibited. Furthermore, micro-sized carbon fiber (CF) is chosen as a structural reinforcement additive during electrode fabrication, and the Fe3O4@RPC/RGO sample delivers a good specific capacity of 1170.5 mAh·g−1 under a current rate of 1000 mA·g−1 for 500 cycles in the half cell form. The reasons for superior electrochemical behaviors have been revealed and the lithium-ion storage performances of the Fe3O4@RPC/RGO sample in the full cell form have been preliminarily investigated.

Remote Floating-Gate Field-Effect Transistor with 2-Dimensional Reduced Graphene Oxide Sensing Layer for Reliable Detection of SARS-CoV-2 Spike Proteins.

Despite intensive research of nanomaterials-based field-effect transistors (FETs) as a rapid diagnostic tool, it remains to be seen for FET sensors to be used for clinical applications due to a lack of stability, reliability, reproducibility, and scalability for mass production. Herein, we propose a remote floating-gate (RFG) FET configuration to eliminate device-to-device variations of two-dimensional reduced graphene oxide (rGO) sensing surfaces and most of the instability at the solution interface. Also, critical mechanistic factors behind the electrochemical instability of rGO such as severe drift and hysteresis were identified through extensive studies on rGO-solution interfaces varied by rGO thickness, coverage, and reduction temperature. rGO surfaces in our RFGFET structure displayed a Nernstian response of 54 mV/pH (from pH 2 to 11) with a 90% yield (9 samples out of total 10), coefficient of variation (CV) < 3%, and a low drift rate of 2%, all of which were calculated from the absolute measurement values. As proof-of-concept, we demonstrated highly reliable, reproducible, and label-free detection of spike proteins of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a saliva-relevant media with concentrations ranging from 500 fg/mL to 5 μg/mL, with an R2 value of 0.984 and CV < 3%, and a guaranteed limit of detection at a few pg/mL. Taken together, this new platform may have an immense effect on positioning FET bioelectronics in a clinical setting for detecting SARS-CoV-2.

Effect of β-MnO2 on Controlled Polymorphism of VO2(x) (x = A, B, M Polymorphs) Microstructures Anchored on Two-Dimensional Reduced Graphene Oxide Nanosheets for Overall Water Splitting

Herein, nonprecious bifunctional composite materials made of vanadium dioxide (VO2) anchored on two-dimensional reduced graphene oxide (2D-rGO) nanosheets (VO2/2D-rGO) via a one-step in situ hydrothermal method were developed. In particular, different polymorphs of VO2 microstructures, that is, VO2(A), VO2(B), VO2(M), and so on, obtained by the influence of β-MnO2 have been paid much attention because of their wide range of potential applications, especially, in electrochemical water splitting. Accordingly, the electrochemical activity of the VO2/2D-rGO composite for the oxygen evolution reaction and hydrogen evolution reaction (OER and HER) was dramatically amended by tuning the electronic structure of VO2(A) using a cationic additive such as β-MnO2. Moreover, the obtained VO2(A)/2D-rGO (MVAG) composite was used as a precursor for attaining different polymorph-based composite materials by altering the additive KMnO4. The crystallographic phase transition of the VO2(x) microstructure was systematically studied and confirmed by powder X-ray diffractometer patterns. By varying the additive concentration, three different composite materials were prepared: β-MnO2-VO2(M)/2D-rGO (MVMG), β-MnO2-VO2(B)/2D-rGO (MVBG), and β-MnO2-V2O5/2D-rGO (MVOG). Benefiting from the prismatic type of the VO2(B) microstructure, the MVBG composite material shows enhanced OER (273 mV) and HER (178 mV) activities to achieve a current density of 10 mA cm–2. Remarkably, the two-electrode system has been constructed using one of the polymorphs such as MVBG||MVBG to study the cell voltage of 1.62 V to reach a current density of 10 mA cm–2 and displayed a Tafel slope of 108 mV dec–1. In addition, the MVBG||MVBG system showed outstanding long-term stability for 35 h. This work offers simple and convenient protocols for achieving cost-effective bifunctional composite materials for overall water splitting.

One-dimensional self-assembled Co2SnO4 nanosphere to nanocubes intertwined in two-dimensional reduced graphene oxide: an intriguing electrocatalytic sensor toward mesalamine detection

The present work deals with the preparation of hybridized electrode material with electrostatic self-assembly strategy for mesalamine (MES) detection. Grabbing significant abilities between the one-dimensional bimetallic oxides and two-dimensional nanosheets network, a nanohybrid was designed. The developed cobalt stannate/reduced graphene oxide (Co2SnO4/rGO)-1D/2D heterostructure will possess improvised anisotropic electron transport, earth abundant, highly conducting, multiple actives site, and higher surface area. The 1D/2D nanostructured architecture will enhance faster electron and mass transport during the electrochemical analysis, which is more significant for MES detection. Progressive testing of Co2SnO4/rGO for structural analysis was done, and highly crystalline nature was proved. The self-assembled nanospheres to form nanocube such as Co2SnO4 strongly attached over the rGO matrix was confirmed with field emission scanning microscope, and nanocube structure is more visible with high-resolution transmission electron microscopy. The hierarchical highly electroactive material establishes lower detection limit at 4.9 nM with sensitivity of about 8.57 μA/μM/cm2. The interfacial area of nanocomposite with higher conducting channels to improve the interactions with MES resulted in enhanced selectivity. The practical analysis in environmental, pharmaceutical, and biological fluids (human urine and serum) showed good recovery. The Co2SnO4/rGO will be more prominent and significant as electrode material in electrochemical sensing.

Solar-blind ultraviolet photodetectors with thermally reduced graphene oxide formed on high-Al-content AlGaN layers

Solar-blind deep-ultraviolet (UV) photodetectors (PDs) with high responsivity and fast response have attracted significant attention in environmental, industrial, biological, and military applications. AlGaN is a representative semiconductor material in the field of solar-blind detection; semiconductor performance can be accelerated by combining it with high-transparency, high-stability contact electrode materials. In this study, solar-blind deep-UV metal–semiconductor–metal (MSM) PDs were fabricated based on two-dimensional reduced graphene oxide (rGO) contacts formed on various high-Al-content AlGaN semiconductors. A low dark current in the order of a few picoamperes and a fast photoresponse time of a few tens of milliseconds were confirmed. The investigation of the effects of front- and back-side illumination showed that the photocurrents and corresponding responsivities of the PDs drastically improved under back-side illumination. In detail, the peak locations of the responsivity–wavelength curves were downshifted from 290 nm with a responsivity of 0.0518 A/W for the rGO/Al0.5Ga0.5N MSM PD to 250 nm with a responsivity of 0.0113 A/W for the rGO/Al0.7Ga0.3N MSM PD under back-side illumination. These results indicate that rGO contacts on AlGaN provide a viable approach for developing solar-blind deep-UV PDs.

Composite nanofiltration membrane comprising one-dimensional erdite, two-dimensional reduced graphene oxide, and silkworm pupae binder

Composite nanofiltration membranes offer advantages because of synergetic effects among the constituent materials’ properties. However, the sustainability of both the membrane fabrication and the raw materials has been a drawback of this energy-efficient separation technology. We report the facile fabrication of a nanocomposite membrane composed of a two-dimensional (2D) material of reduced graphene oxide (rGO) combined with a one-dimensional (1D) material of a ternary metal-based chalcogenide (NaFeS2 or NFS) using silkworm pupae protein as a natural binder. All the source materials can be derived from either nature or waste, ensuring the sustainability of the membrane and its production method. The structural characteristics of the synthesized membranes were analyzed, and the morphology of the composite membranes was studied thoroughly. Thermogravimetric analysis, differential scanning calorimetry, and nanoindentation characterizations indicated that the composite membranes were mechanically and thermally stable. The water and acetone fluxes; salt, dye, and pollutant rejections; and long-term membrane performance were evaluated using a cross-flow filtration system. Solute rejection was observed to increase (up to 98%, 94%, 95%, and 78% for Rhodamine B, 2,4-dichlorophenol, MgCl2, and NaCl, respectively) with increasing concentration of the nanomaterials in the membrane. The fine-tuning of the molecular weight cutoff from 794 to 600 g mol−1 was achieved by varying the concentration of the nanomaterials from 1 to 3 mg mL−1. Our research findings demonstrate the synergetic effects of combining 1D and 2D materials using silkworm pupae binder. The composite membrane was stable in different classes of organic solvents, including hydrocarbons, alcohols, esters, ethers, polar aprotic solvents, halogenated solvents, and ketones. This first use of natural pupae binder in constructing membrane materials paves the way toward the development of more sustainable membranes.

Spray drying induced engineering a hierarchical reduced graphene oxide supported heterogeneous Tin dioxide and Zinc oxide for Lithium-ion storage

In this work, a hierarchical reduced graphene oxide (RGO) supportive matrix consisting of both larger two-dimensional RGO sheets and smaller three-dimensional RGO spheres was engineered with ZnO and SnO2 nanoparticles immobilized. The ZnO and SnO2 nanocrystals with controlled size were in sequence engineered on the surface of the RGO sheets during the deoxygenation of graphene oxide sample (GO), where the zinc-containing ZIF-8 sample and metal tin foil were used as precursors for ZnO and SnO2, respectively. After a spray drying treatment and calcination, the final ZnO@SnO2/RGO-H sample was obtained, which delivered an outstanding specific capacity of 982 mAh·g−1 under a high current density of 1000 mA·g−1 after 450 cycles. Benefitting from the unique hierarchical structure, the mechanical strength, ionic and electric conductivities of the ZnO@SnO2/RGO-H sample have been simultaneously promoted. The joint contributions from pseudocapacitive and battery behaviors in lithium-ion storage processes bring in both large specific capacity and good rate capability. The industrially mature spray drying method for synthesizing RGO based hierarchical products can be further developed for wider applications.

Enhanced ammonia sensing properties of rGO/WS2 heterojunction based chemiresistive sensor by marginal sulfonate decoration

Abstract Two-dimensional reduced graphene oxide (rGO) nanosheets were pre-sulfonated and further incorporated by WS2 nanoflakes to form S-rGO/WS2 heterojunctions by hydrothermal synthesis. The sulfonation and WS2 incorporation in S-rGO/WS2 heterojunction have been confirmed by EDS, XPS and FTIR. The sensing performance of rGO-based chemiresistive-type sensor to ammonia at room temperature has been significantly improved by the sulfonation and incorporation of WS2 nanoflakes. The chemiresistive sensor based on S-rGO/WS2 exhibits enhanced response signals to 10∼50 ppm ammonia, while the response/recovery time is significantly shortened compared to rGO/WS2 reported previously at room temperature. It benefits from both the extra introduced active acid centers sensitive to ammonia molecules and the better desorption-ability facilitated significantly by sulfonate groups (S O3H). The adsorption energy calculation of ammonia molecule on the sulfonated graphene sheet based on density functional theory (DFT) has been performed to illustrate the adsorption capacity of S O3H group. The selectivity and stability of gas sensor based on S-rGO/WS2 have also been studied.

Ru x Pd y Alloy Nanoparticles Uniformly Anchored on Reduced Graphene Oxide Nanosheets (Ru x Pd y @rGO): A Recyclable Catalyst.

In this work, RuxPdy alloy nanoparticles were uniformly decorated on a two-dimensional reduced graphene oxide (rGO) sheet by an in situ chemical co-reduction process. The resulting products were characterized by various physiochemical techniques such as X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic absorption spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Further, the synthesized RuxPdy@rGO nanocomposites have been employed as a heterogeneous catalyst for three different catalytic reactions: (1) dehydrogenation of aqueous ammonia borane (AB); (2) hydrogenation of aromatic nitro compounds using ammonia borane as the hydrogen source, and (3) for the synthesis of aromatic azo derivatives. The present work illustrates the sustainable anchoring of metal nanoparticles over the surface of rGO nanosheets, which could be used for multifarious catalytic reactions.

Redox-active rGO-nZVI nanohybrid-catalyzed chain shortening of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS)

Per- and polyfluoroalkyl substances (PFASs) are exceptionally stable chemicals due to their strong CF bonds. Nanoscale zero-valent iron (nZVI) particles have the potential to remove and degrade PFASs through redox activity. In this study, we deposited nZVI onto two-dimensional reduced graphene oxide (rGO) nanosheets and tested these synthesized rGO-nZVI nanohybrid (NH) for the treatment of a mixture of short- and long-chain PFASs in water with and without H2O2. All PFASs were removed at a higher efficiency by the rGO-nZVI NH than by the parent materials rGO and nZVI. Notably, the long-chain PFASs were removed at a faster rate than the short-chain PFASs. After a 10 min exposure to the rGO-nZVI NH without H2O2, the long-chain PFASs (perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA)) were removed by 85 % and 39 %, respectively, while short-chain PFASs (perfluoropentane sulfonic acid and perfluoropentanoic acid) were removed by 19 % and 18 %, respectively. The addition of H2O2 enhanced the PFAS treatment performance by 10–18 %, which can be attributed to the generation of reactive oxygen species by the rGO-nZVI NH. Liquid chromatography high-resolution mass spectrometry analysis confirmed the formation of unique shorter chain and partially defluorinated PFAS-Fe complexes from both PFOS and PFOA.