Reduced Graphene Oxide Substrate Research Articles

Redox-active 9,10-phenanthrenequinone non-covalently modify reduced graphene oxide for high-performance asymmetric supercapacitor and zinc-ion hybrid capacitors

Redox-active organic molecules show great potential in novel renewable energy storage devices by modifying carbon-based materials in covalent or non-covalent forms due to their light-weight, rich structural diversity, good designability and abundance. Herein, we synthesized redox-active 9,10-phenanthrenequinone (PQ) molecules non-covalently modified reduced graphene oxide (RGO) nanocomposites by an improved simple one-step solvothermal method and explored their application as advanced electrode in aqueous energy storage devices. Benefiting from the rich redox-active sites brought by the anchored PQ molecules and the formation of the hierarchical porous network nanostructures with the RGO substrates that facilitates the charge transport and ion diffusion kinetics, the synthesized RGO/PQs nanocomposites exhibit significantly enhanced electrochemical energy storage performance. The optimal RGO/PQ-1.5 electrode has a high specific capacitance of 383.3 F g−1 at 0.5 A g−1 and good rate capability. And the asymmetric supercapacitor (ASC) assembled with the N-RGO negative electrode exhibits significantly better energy density than pure carbon electrode ASCs. More surprisingly, the assembled RGO/PQ-1.5//Zn zinc-ion hybrid capacitor exhibits an attractive specific capacity of 139.4 mAh g−1, a high energy density of 134.6 Wh kg−1, and an ultra-long cycling stability with 95.3 % capacity retention after 14,000 cycles, demonstrating excellent zinc-ion energy storage performance.

Ni Nanoparticles on the Reduced Graphene Oxide Surface Synthesized in Supercritical Isopropanol.

Nanocomposites based on ferromagnetic nickel nanoparticles and graphene-related materials are actively used in various practical applications such as catalysis, sensors, sorption, etc. Therefore, maintaining their dispersity and homogeneity during deposition onto the reduced graphene oxide substrate surface is of crucial importance to provide the required product characteristics. This paper demonstrates a new, reproducible method for preparing a tailored composite based on nickel nanoparticles on the reduced graphene oxide surface using supercritical isopropanol treatment. It has been shown that when a graphene oxide film with previously incorporated Ni2+ salt is treated with isopropanol at supercritical conditions, nickel (2+) is reduced to Ni (0), with simultaneous deoxygenation of the graphene oxide substrate. The resulting composite is a solid film exhibiting magnetic properties. XRD, FTIR, Raman, TEM, and HRTEM methods were used to study all the obtained materials. It was shown that nickel nanoparticles on the surface of the reduced graphene oxide had an average diameter of 27 nm and were gradually distributed on the surface of reduced graphene oxide sheets. The data obtained allowed us to conduct a reconnaissance discussion of the mechanism of composite fabrication in supercritical isopropanol.

Dynamic Electronic and Ionic Transport Actuated by Cobalt-Doped MoSe2 /rGO for Superior Potassium-Ion Batteries.

Molybdenum selenium (MoSe2 ) has tremendous potential in potassium-ion batteries (PIBs) due to its large interlayer distance, favorable bandgap, and high theoretical specific capacity. However, the poor conductivity and large K+ insertion/extraction in MoSe2 inevitably leads to sluggish reaction kinetics and poor structural stability. Herein, Coinduced engineering is employed to illuminate high-conductivity electron pathway and mobile ion diffusion of MoSe2 nanosheets anchored on reduced graphene oxide substrate (Co-MoSe2 /rGO). Benefiting from the activated electronic conductivity and ion diffusion kinetics, and an expanded interlayer spacing resulting from Co doping, combined with the interface coupling with highly conductive reduced graphene oxide (rGO) substrate through Mo-C bonding, the Co-MoSe2 /rGO anode demonstrates remarkable reversible capacity, superior rate capability, and stable long-term cyclability for potassium storage, as well as superior energy density and high power density for potassium-ion capacitors. Systematic performance measurement, dynamic analysis, in-situ/ex-situ measurements, and density functional theory (DFT) calculations elucidate the performance-enhancing mechanism of Co-MoSe2 /rGO in view of the electronic and ionic transport kinetics. This work offers deep atomic insights into the fundamental factors of electrodes for potassium-ion batteries/capacitors with superior electrochemical performance.

Ag, Au and ZrO2@reduced graphene oxide nanocomposites; Pd free catalysis of suzuki-miyaura coupling reactions

Suzuki coupling is a widely used, well-studied and versatile method in synthetic chemistry for development of C–C bonds where palladium-based catalysts have been used extensively in the reaction to date. We report a Suzuki-cross-coupling reaction for C–C bonds formation between aryl halides and phenylboronic acid by using Metal/metal oxide@Reduced graphene oxide nanocomposites being efficient, simple and cost-effective. In this work, plant mediated synthesis of silver, gold and zirconia nanoparticles doped Reduced Graphene Oxide nanocomposites is reported where 30 mg of each of the catalysts resulted in C-C bond formation achieving percentage yield comparable to palladium-based catalyst used as standard in series of reactions, attaining highest yield with silver based catalyst. The catalysts demonstrated high catalytic activity over three cycles of recycling with no loss. Bromoaryl and phenylboronic acid are coupled together by the increased surface area of the reduced graphene oxide substrate, which also exhibits enhanced reactivity toward other chemical reactions. XRD, FTIR and UV–vis analyses were used to describe the synthesized catalyst. Using the devised technique, various substituted aryl halides have been used successfully with modest to high yields of the desired biphenyls.

High specific energy and power sodium-based dual-ion supercabatteries by pseudocapacitive Ni-Zn-Mn ternary perovskite fluorides@reduced graphene oxides anodes with conversion-alloying-intercalation triple mechanisms

• A new concept of sodium-based dual-ion supercabattery (S-DICB) was firstly proposed. • The superior pseudocapacitance-dominated kinetics was verified. • The charge storage mechanism of KNZMF@rGO anode was deeply deciphered. • Utilizing different presodiated methods to explore the impact on S-DICB. Sodium (Na)-based electrochemical energy storage devices have drawn particular attention in the renewable and rechargeable energy storage system primarily because of their remarkable energy density and cost-competitive advantages. Herein, we have reported a novel ternary perovskite fluoride K 0.97 Ni 0.31 Zn 0.28 Mn 0.41 F 2.84 with a well-distributed reduced graphene oxide substrate (denoted as KNZMF@rGO) as anode for Na-ion storage that possesses the fast kinetics validated via electrochemical and density functional theory (DFT) methods as well as superior lifespan, which delivers fascinating performances owing to the unexceptionable synergistic effect of Ni, Zn and Mn redox-active species with variable valence. Meanwhile, the surface conversion, alloying and intercalation triple hybridization mechanisms of KNZMF@rGO anode have been explored by the electrochemical analysis and the diverse ex situ physicochemical characterizations. What is more, this work also offers new insights into the device design and proposes the previously unreported “sodium-based dual-ion supercabatteries” (S-DICBs) systems for establishing advanced electrochemical energy storage devices, which exhibit the more intriguing properties than traditional sodium ion capacitors (SICs) and sodium-based dual ion batteries (S-DIBs). In parallel, utilizing different presodiated current densities of anode to explore their impact on the various electrochemical properties of S-DICBs opens up a way for the research of presodiation techniques in the future. A new concept of sodium-based dual-ion supercabattery (S-DICB) was constructed via the pseudocapacitive Ni-Zn-Mn ternary perovskite fluoride (ABF 3 )@reduced graphene oxide (KNZMF@rGO) anode material, which shows the surface conversion/alloying/intercalation triple mechanisms for charge storage. The lower presodiated current density of anode leads to the higher electrochemical properties of S-DICB because of the superior solid electrolyte interface (SEI) film, charge balance and utilization rate of active substance.

Interspace-controlled biosensing interface with enhanced charge transfer based on tripod DNA probes

Binding of a target by a probe for selective detection depends on the state of the probes on the sensing interface. Here, the hanging strand length of triple-helix DNA was used to form tripod probes immobilized via π-π interactions on a reduced graphene-oxide substrate. The spacing between the probes was adjusted by controlling the lengths of the tripod “feet” on the substrate; that is, increased probe spacing occurred when foot size increased over the range of 6–12 bases. The surface coverages and electron-transfer rates mediated the tripod DNA probes were characterized by electrochemical methods and atomic force microscopy. The electron-transfer mediated by the tripod DNA probes was higher than that mediated by doubled-stranded DNA. Then different sizes tripod DNA probes were developed for protein-CEA detection. The DNA probes with 10 bases feet showed the best detection limit of detection of 10−6 ng/mL in the detection linear range (10−6 - 25 ng/mL). The result demonstrated the tripod DNA probes with different sizes could obtain excellent sensitivity when it applied to the target with appropriate size. This interspace-controlled biosensing interface of tripod DNA probes with enhanced charge transfer should find widespread applications in clinical, medical, biological, and environmental areas for precise detection of differently sized targets.

A CoN‐based OER Electrocatalyst Capable in Neutral Medium: Atomic Layer Deposition as Rational Strategy for Fabrication

AbstractReported herein is an active and durable CoN‐containing oxygen evolution reaction (OER) electrocatalyst which efficiently functions in a neutral medium (pH ≈7). The composite material (N, S)‐RGO@CoN is synthesized by delicate atomic layer deposition (ALD) of CoN on a nitrogen and sulfur (N, S) co‐doped reduced graphene oxide (RGO) substrate. Representative results of the comprehensive study are: 1) The flower‐like sphere RGO substrate prepared by spray drying method features rich physical and chemical properties, which are beneficial for rapid mass/charge transfer to improve the intrinsic OER process; 2) the optimal ALD material for OER tests is afforded by tuning spray conditions and ALD parameters. Versatile structural and compositional characterizations confirm uniform growth and strong chemical coupling of nanostructured CoN on (N, S)‐RGO matrix; 3) the material is electrocatalytically active and durable in a neutral electrolyte, recording an OER overpotential of 220 mV at a current density of 10 mA cm−2 and stability of 20 h continuous catalysis at 20 mA cm−2 with nearly 100% Faradic efficiency; 4) Upon the experimental studies and density functional theory calculations, the eventual mechanism of remarkable OER activity conforms to the structural fate of ALD CoN electronic coupling to the carbon substrate.

Ultrahigh-temperature ferromagnetism in MoS2 Moiré superlattice/graphene hybrid heterostructures

Realizing high-temperature ferromagnetism in two-dimensional (2D) semiconductor nanosheets is significant for their applications in next-generation magnetic and electronic nanodevices. Herein, this goal could be achieved on a MoS2 Moire superlattice grown on the reduced graphene oxide (RGO) substrate by a hydrothermal approach. The as-synthesized bilayer MoS2 superlattice structure with rotating angle (ϕ = 13° ± 1°) of two hexagonal MoS2 lattices, possesses outstanding ferromagnetic property and an ultra-high Curie temperature of 990 K. The X-ray absorption near-edge structure and ultraviolet photoelectron spectroscopies combined with density functional theory calculation indicate that the covalent interactions between MoS2 Moire superlattice and RGO substrate lead to the formation of interfacial Mo-S-C bonds and complete spin polarization of Mo 4d electrons near the Fermi level. This design could be generalized and may open up a possibility for tailoring the magnetism of other 2D materials.

Enabling shuttle-free of high concentration redox mediators by metal organic framework derivatives in lithium–oxygen batteries

High concentration LiBr is beneficial to enhance the Br− oxidation rate, displaying stable low voltage plateau during charging process for lithium–oxygen batteries. However, the sufficient cyclic performance is generally restricted by uncontrollable high level Br3−, resulting in the low energy efficiency and shuttle effect. Herein, a nanoreactor, red-ox mediators shuttling suppressor and lithium-metal protector with the combination of the high concentration and shuttle-free LiBr are successfully constructed by anchoring the Br3− to carbonized ZIF-8 supported on reduced graphene oxide substrate (ZC-rGO). ZnO-decorated/nitrogen-doped 3D carbon framework of ZC-rGO cathode can accurately capture Br3− by space confinement effects and/or chemisorption, which is beneficial to improve the oxidation of discharge products (Li2O2) and avoid the anode corrosion. The Li–O2 battery demonstrates enormous advantages of the RMs in comparation with the typical rGO-based batteries, such as better cycling performance (>90 cycles) and more stable overpotential (<1.0 V). The proposed strategy in this study opens up a new way of inhibiting the shuttle effect of RMs in Li–O2 batteries and other halogen batteries.

A flexible LiFePO4/carbon nanotube/reduced graphene oxide film as self-supporting cathode electrode for lithium-ion battery

By a rational design and facile vacuum filtration, a flexible and free-standing LiFePO4/carbon nanotube/reduced graphene oxide film electrode is fabricated for lithium-ion batteries. The carbon nanotube and reduced graphene oxide substrates are favor of improving the conductivity of the electrode; meanwhile, the LiFePO4 particles can efficiently reduce aggregation between carbon nanotube and reduced graphene oxide. The resultant self-supporting LiFePO4/carbon nanotube/reduced graphene oxide electrode delivers excellent electrochemical performance beyond the metal-base electrode. After 100 cycles at 0.2 C, the capacity maintains 151 mAh g−1, nearly staying the same with initial value. Especially, at 10 C, the specific capacity still keeps 98 mAh g−1. Moreover, these findings in this work supply a means of manufacturing LiFePO4 electrode and urge the practical application of LiFePO4 in flexible facilities.

Impact of Graphene-Based Surfaces on the Basic Biological Properties of Human Umbilical Cord Mesenchymal Stem Cells: Implications for Ex Vivo Cell Expansion Aimed at Tissue Repair.

The potential therapeutic applications of mesenchymal stem/stromal cells (MSCs) and biomaterials have attracted a great amount of interest in the field of biomedical engineering. MSCs are multipotent adult stem cells characterized as cells with specific features, e.g., high differentiation potential, low immunogenicity, immunomodulatory properties, and efficient in vitro expansion ability. Human umbilical cord Wharton’s jelly-derived MSCs (hUC-MSCs) are a new, important cell type that may be used for therapeutic purposes, i.e., for autologous and allogeneic transplantations. To improve the therapeutic efficiency of hUC-MSCs, novel biomaterials have been considered for use as scaffolds dedicated to the propagation and differentiation of these cells. Nowadays, some of the most promising materials for tissue engineering include graphene and its derivatives such as graphene oxide (GO) and reduced graphene oxide (rGO). Due to their physicochemical properties, they can be easily modified with biomolecules, which enable their interaction with different types of cells, including MSCs. In this study, we demonstrate the impact of graphene-based substrates (GO, rGO) on the biological properties of hUC-MSCs. The size of the GO flakes and the reduction level of GO have been considered as important factors determining the most favorable surface for hUC-MSCs growth. The obtained results revealed that GO and rGO are suitable scaffolds for hUC-MSCs. hUC-MSCs cultured on: (i) a thin layer of GO and (ii) an rGO surface with a low reduction level demonstrated a viability and proliferation rate comparable to those estimated under standard culture conditions. Interestingly, cell culture on a highly reduced GO substrate resulted in a decreased hUC-MSCs proliferation rate and induced cell apoptosis. Moreover, our analysis demonstrated that hUC-MSCs cultured on all the tested GO and rGO scaffolds showed no alterations of their typical mesenchymal phenotype, regardless of the reduction level and size of the GO flakes. Thus, GO scaffolds and rGO scaffolds with a low reduction level exhibit potential applicability as novel, safe, and biocompatible materials for utilization in regenerative medicine.

Uniform, Scalable, High-Temperature Microwave Shock for Nanoparticle Synthesis through Defect Engineering

Summary Here we demonstrate a thermal shock synthesis method triggered by microwave irradiation for the rapid synthesis of nanoparticles on reduced graphene oxide (RGO) substrate. With properly controlled reduction, RGO has high electrical conductivity while maintaining functional groups, leading to an extremely efficient microwave absorption of ∼70%. The high utilization of microwaves results in the ability to raise the temperature to 1,600 K in just 100 ms, which is followed by rapid quenching to room temperature. The defects on the RGO are crucial for achieving this record-high microwave-induced temperature as these defects play a fundamental role in absorbing the radiation as well as the self-quenching mechanism. By loading precursors onto RGO, we can utilize rapid temperature change to synthesize nanoparticles. The nanoparticles are ∼10 nm with uniform distribution. This facile, rapid, and universal synthesis technique has the potential to be employed in large-scale production of nanomaterials and suggests a new direction for nanosynthesis.

Manganese nitride stabilized on reduced graphene oxide substrate for high performance sodium ion batteries, super-capacitors and EMI shielding

Though the utility of manganese compounds such as oxides, sulphides has been well researched in energy storage applications such as super-capacitors and lithium-ion batteries, the utility of manganese nitrides hasn't been reported yet, especially as anode in sodium-ion batteries. In this manuscript we report synthesis of manganese nitride decorated reduced graphene oxide (MnN@rGO) prepared by simple microwave nitridation technique and its utility as anode material in sodium-ion batteries, electrodes in super-capacitors and in EMI shielding applications. In energy storage applications such as sodium ion batteries, MnN@rGO electrodes exhibited sodium storage capacity of 716 mAhg−1 whereas when used as electrodes in super-capacitors, a high capacitance value of 639.2 Fg-1 at scan rates of 10 mVs−1 in 1 M Na2SO4 aqueous electrolyte was achieved. The EMI shielding effectiveness measured in the X-band region of 2–18 GHz was about 30–32 dB which is 300% more than reduced graphene oxide.

A New Broadband and Strong Absorption Performance FeCO3/RGO Microwave Absorption Nanocomposites

A novel composite of FeCO3 nanoparticles, which are wrapped with reduced graphene oxide (RGO), is fabricated using a facile one-spot solvothermal method. The composite consists of a substrate of RGO and FeCO3 nanoparticles that are embedded in the RGO layers. The experimental results for the FeCO3/RGO composite reveal a minimum refection loss (−44.5 dB) at 11.9 GHz when the thickness reaches 2.4 mm. The effective bandwidth is 7.9 GHz between 10.1 and 18 GHz when the refection loss was below −10 dB. Compared to GO and RGO, this type of composite shows better microwave absorption thanks to improved impedance matching. Overall, this thin and lightweight FeCO3/RGO composite is a promising candidate for absorbers that require both strong and broad absorption.

Cellular organization of three germ layer cells on different types of noncovalent functionalized graphene substrates

Graphene and its derivatives have seen a rapid rise in interest as promising biomaterials especially in the field of tissue engineering, regenerative medicine, and cell biology of late. Despite its proven potential in numerous biological applications, information regarding the relationship between the different forms of graphene and cell lineages is still lacking partly due to its topical emergence in cellular studies. Herein, we explore the biocompatibility of four types of graphene substrates (chemical vapor deposition grown graphene, mechanically exfoliated graphene, chemically exfoliated graphene oxide, and reduced graphene oxide) with three types of somatic cells (keratinocytes, hepatocytes, endothelial cells) derived from the three germ layers in relation to cell adhesion, proliferation, morphology, and gene expression. The results revealed exceptional cell adhesion for all tested groups but enhanced proliferation and cytoskeletal interconnectivity in graphene oxide and reduced graphene oxide substrates. We were unable to detect any adverse effects in gene expression and survivability during a week of culture. We further show topographic changes to graphene substrates under fetal bovine serum adsorption to better illustrate the actual microenvironment of inhabitant cells. This study highlights the extraordinary synergy between graphene and somatic cells, suggesting the discretionary use of extracellular matrix components for in vitro cultivation.

Structurally Tunable Reduced Graphene Oxide Substrate Maintains Mouse Embryonic Stem Cell Pluripotency.

Culturing embryonic stem cells (ESCs) in vitro usually requires animal‐derived trophoblast cells, which may cause pathogenic and immune reactions; moreover, the poor repeatability between batches hinders the clinical application of ESCs. Therefore, it is essential to synthesize a xenogeneic‐free and chemically well‐defined biomaterial substrate for maintaining ESC pluripotency. Herein, the effects of structurally tunable reduced graphene oxide (RGO) substrates with different physicochemical properties on ESC pluripotency are studied. Colony formation and CCK‐8 assays show that the RGO substrate with an average 30 µm pore size promotes cell survival and proliferation. The unannealed RGO substrate promotes ESC proliferation significantly better than the annealed substrate due to the interfacial hydrophilic groups. The RGO substrate can also maintain ESC for a long time. Additionally, immunofluorescence staining shows that ESCs cultured on an RGO substrate highly express E‐cadherin and β‐catenin, whereas after being modified by Dickkopf‐related protein 1, the RGO substrate is unable to sustain ESC pluripotency. Furthermore, the cell line that interferes with E‐cadherin is also unable to maintain pluripotency. These results confirm that the RGO substrate maintains ESC pluripotency by promoting E‐cadherin‐mediated cell–cell interaction and Wnt signaling.

High-performance Si flexible anode with rGO substrate and Ca2+ crosslinked sodium alginate binder for lithium ion battery

For the purpose of free-standing and stable silicon anode for lithium-ion battery, a silicon flexible anode is fabricated through a sequential filtration process and a post heat treatment. The reduced graphene oxide film is employed as a substrate, upon which the silicon nanoparticles, carbon nanotubes, and Ca2+ crosslinked sodium alginate are built. The prepared silicon flexible anode exhibits great electrochemical performance, due to the good flexibility and electric conduction of the reduced graphene oxide substrate, and the mechanical reinforcement of the strong three dimensional network formed by carbon nanotubes and Ca2+ crosslinked sodium alginate binder. The specific capacity of silicon flexible anode regarding the total mass of the electrode is as high as ∼1100 mAh g–1 at current density of 0.1 A g–1, 7 times higher than that of the traditional silicon anode with Cu foil current collector (∼150 mAh g–1). Moreover, it shows satisfactory rate capacity and favorable cycle stability (70% capacity retention after 100 cycles). Due to the flexibility, free-standing feature, and high electrochemical performance, the silicon flexible anode is potential for future applications in flexible lithium-ion battery and light-weight electronics.

Tuning photoluminescence quenching efficiency of reduced graphene oxide substrates using silver nanoparticles

In this paper we report the synthesis of reduced graphene oxide doped with silver nanoparticles using aqueous extract of Psidium guajava. The dependence of photoluminescence (PL) quenching efficiency of reduced graphene oxide with variable dosage of silver nanoparticles using methylene blue as a model dye is investigated. The effect of excitation energies on the PL quenching efficiency of as-synthesized samples is also systematically studied. At 420 nm excitation, the plasmonic field of silver nanoparticles accelerates charge transfer from methylene blue to reduced graphene oxide resulting in efficient PL quenching as compared to pristine reduced graphene oxide. However at 650 nm excitation, the PL quenching efficiency of reduced graphene oxide surpasses silver nanoparticles doped reduced graphene oxide. This is attributed to strong interaction between reduced graphene oxide and methylene blue in absence of plasmonic fields at lower excitation energies. In order to enhance the quenching efficiency of silver nanoparticle doped reduced graphene oxide at 650 nm excitation, the concentration of silver nanoparticles over graphene surface is increased. This leads to increase in inhomogeneously sized and shaped nanoparticles over graphene surface which not only broadens the plasmonic absorption band but also improves the quenching efficiency at 650 nm. The schematics of charge transfer states via which the PL quenching occurs at different excitation energies are also presented.

Carbon‐Encapsulated SnO2 Core–Shell Nanowires Directly Grown on Reduced Graphene Oxide Sheets for High‐Performance Li‐Ion Battery Electrodes

AbstractA designed electrode material of carbon‐encapsulated tin dioxide core–shell nanowires that are synthesized directly on reduced graphene oxide substrates is reported, and its application as a positive electrode material for lithium‐ion battery is shown. Each of the individual tin dioxide nanowires is wrapped with carbon shell layers and grown on a reduced graphene oxide substrate, which gives rise to structural benefits for electrochemical performance of the lithium‐ion battery. Such carbon structures allow the electrode materials to withstand the mechanical stress during repeated charge/discharge processes and facilitate the reaction kinetics for the lithiation/delithiation processes. In the electrochemical cell tests, the synergetic effect of the proposed electrode design is explicitly verified by presenting highly enhanced rate capability and cycle durability on full‐cell batteries as well as half‐cell tests.

Improving the glial differentiation of human Schwann-like adipose-derived stem cells with graphene oxide substrates.

There is urgent need to improve the clinical outcome of peripheral nerve injury. Many efforts are directed towards the fabrication of bioengineered conduits, which could deliver stem cells to the site of injury to promote and guide peripheral nerve regeneration. The aim of this study is to assess whether graphene and related nanomaterials can be useful in the fabrication of such conduits. A comparison is made between graphene oxide (GO) and reduced GO substrates. Our results show that the graphene substrates are highly biocompatible, and the reduced GO substrates are more effective in increasing the gene expression of the biomolecules involved in the regeneration process compared to the other substrates studied.