Ultrahydrophobic melamine sponge via interfacial modification with reduced graphene oxide/titanium dioxide nanocomposite and polydimethylsiloxane for oily wastewater treatment

Three-dimensional(3D)porous absorbents have attracted significant attention in the oily wastewater treatment technology due to their high porosity and elasticity.Given their amphiphilic surface,they have a propensity to simultaneously absorb water and oil,which restricts their range of applications.In this study,a reduced graphene oxide and titanium dioxide nanocomposite(rGO/TiO_(2))was used to fabricate an ultra-hydrophobic melamine sponge(MS)through interfacial modification using a solution immersion technique.To further modify it,poly-dimethylsiloxane(PDMS)was grafted onto its surface to establish stronger covalent bonds with the composite.The water contact angle of the sponge(rGO/TiO_(2)/PDMS/MS)was 164.2°,which satisfies the condition for ultrahydrophobicity.The evidence of its water repellency was demonstrated by the Cassie-Baxter theory and the lotus leaf effect.As a result of the increased density of rGO/TiO_(2)/PDMS/MS,it recorded an initial capacity that was 2 g/g lower than the raw MS for crude oil absorption.The raw MS retained 53% of its initial absorption capacity after 20 cycles of absorption,while rGO/TiO_(2)/PDMS/MS retained 97%,suggesting good recyclability.Excellent oil and organic solvent recovery(90%-96%)was demonstrated by rGO/TiO_(2)/PDMS/MS in oil-water combinations.In a continuous separation system,it achieved a remarkable separation efficiency of 2.4×10^(6)L/(m^(3)·h),and in turbulent emulsion separation,it achieved a demulsification efficiency of 90%-91%.This study provides a practical substitute for massive oil spill cleaning.

Mixed‑Dimensional Assembly Strategy to Construct Reduced Graphene Oxide/Carbon Foams Heterostructures for Microwave Absorption,Anti‑Corrosion and Thermal Insulation

Considering the serious electromagnetic wave(EMW)pollution problems and complex application condition,there is a pressing need to amalgamate multiple functionalities within a single substance.However,the effective integration of diverse functions into designed EMW absorption materials still faces the huge challenges.Herein,reduced graphene oxide/carbon foams(RGO/CFs)with two-dimensional/three-dimensional(2D/3D)van der Waals(vdWs)heterostructures were meticulously engineered and synthesized utilizing an efficient methodology involving freeze-drying,immersing absorption,secondary freeze-drying,followed by carbonization treatment.Thanks to their excellent linkage effect of amplified dielectric loss and optimized impedance matching,the designed 2D/3D RGO/CFs vdWs heterostructures demonstrated commendable EMW absorption performances,achieving a broad absorption bandwidth of 6.2 GHz and a reflection loss of-50.58 dB with the low matching thicknesses.Furthermore,the obtained 2D/3D RGO/CFs vdWs heterostructures also displayed the significant radar stealth properties,good corrosion resistance performances as well as outstanding thermal insulation capabilities,displaying the great potential in complex and variable environments.Accordingly,this work not only demonstrated a straightforward method for fabricating 2D/3D vdWs heterostructures,but also outlined a powerful mixeddimensional assembly strategy for engineering multifunctional foams for electromagnetic protection,aerospace and other complex conditions.

Aggregation-regulated bioreduction process of graphene oxide by Shewanella bacteria

The bioreduction of graphene oxide(GO)using environmentally functional bacteria such as Shewanella represents a green approach to produce reduced graphene oxide(rGO).This process differs from the chemical reduction that involves instantaneous molecular reactions.In bioreduction,the contact of bacterial cells and GO is considered the rate-limiting step.To reveal how the bacteria-GO integration regulates rGO production,the comparative experiments of GO and three Shewanella strains were carried out.Fourier-transform infrared spectroscopy,X-ray photoelectron spectroscopy,Raman spectroscopy,and atomic force microscopy were used to characterize the reduction degree and the aggregation degree.The results showed that a spontaneous aggregation of GO and Shewanella into the condensed entity occurred within 36 h.A positive linear correlation was established,linking three indexes of the aggregation potential,the bacterial reduction ability,and the reduction degree(ID/IG)comprehensively.

Reduced graphene oxide aerogel decorated with Mo_(2)C nanoparticles toward multifunctional properties of hydrophobicity,thermal insulation and microwave absorption

Reduced graphene oxide(rGO)aerogels are emerging as very attractive scaffolds for high-performance electromagnetic wave absorption materials(EWAMs)due to their intrinsic conductive networks and intricate interior microstructure,as well as good compatibility with other electromagnetic(EM)components.Herein,we realized the decoration of rGO aerogel with Mo_(2)C nanoparticles by sequential hydrothermal assembly,freeze-drying,and high-temperature pyrolysis.Results show that Mo_(2)C nanoparticle loading can be easily controlled by the ammonium molybdate to glucose molar ratio.The hydrophobicity and thermal insulation of the rGO aerogel are effectively improved upon the introduction of Mo_(2)C nanoparticles,and more importantly,these nanoparticles regulate the EM properties of the rGO aerogel to a large extent.Although more Mo_(2)C nanoparticles may decrease the overall attenuation ability of the rGO aerogel,they bring much better impedance matching.At a molar ratio of 1:1,a desirable balance between attenuation ability and impedance matching is observed.In this context,the Mo_(2)C/r GO aerogel displays strong reflection loss and broad response bandwidth,even with a small applied thickness(1.7 mm)and low filler loading(9.0wt%).The positive effects of Mo_(2)C nanoparticles on multifunctional properties may render Mo_(2)C/r GO aerogels promising candidates for high-performance EWAMs under harsh conditions.

Reduced graphene oxide-embedded nerve conduits loaded with bone marrow mesenchymal stem cell-derived extracellular vesicles promote peripheral nerve regeneration

We previously combined reduced graphene oxide(rGO)with gelatin-methacryloyl(GelMA)and polycaprolactone(PCL)to create an rGO-GelMA-PCL nerve conduit and found that the conductivity and biocompatibility were improved.However,the rGO-GelMA-PCL nerve conduits differed greatly from autologous nerve transplants in their ability to promote the regeneration of injured peripheral nerves and axonal sprouting.Extracellular vesicles derived from bone marrow mesenchymal stem cells(BMSCs)can be loaded into rGO-GelMA-PCL nerve conduits for repair of rat sciatic nerve injury because they can promote angiogenesis at the injured site.In this study,12 weeks after surgery,sciatic nerve function was measured by electrophysiology and sciatic nerve function index,and myelin sheath and axon regeneration were observed by electron microscopy,immunohistochemistry,and immunofluorescence.The regeneration of microvessel was observed by immunofluorescence.Our results showed that rGO-GelMA-PCL nerve conduits loaded with BMSC-derived extracellular vesicles were superior to rGO-GelMA-PCL conduits alone in their ability to increase the number of newly formed vessels and axonal sprouts at the injury site as well as the recovery of neurological function.These findings indicate that rGO-GelMA-PCL nerve conduits loaded with BMSC-derived extracellular vesicles can promote peripheral nerve regeneration and neurological function recovery,and provide a new direction for the curation of peripheral nerve defect in the clinic.

Engineering CoMoO_(4) in reduced graphene oxide as superior cathode hosts for advanced room-temperature sodium-sulfur batteries

Promising room-temperature sodium-sulfur(RT Na-S)battery systems rely on purposely designed highperforming and low-cost electrode materials.Nevertheless,there are the challenges of irreversible dissolution and slow redox kinetics of NaPSs in the complete discharge of sulfur capacity.Herein,engineered CoMoO_(4)in reduced graphene oxide(CoMoO_(4)@rGO)is reported as a class of superior cathode hosts for RT Na-S batteries.The CoMoO_(4)@rGO matrix is designed to facilitate the reversible sodiation and desodiation of sulfur,considering the strong chemisorption between sulfur(and short-chain sodium sulfides)and CoMoO_(4),which alleviates the shuttle effect of sodium sulfides and accelerates the electrochemical reaction rate at RT.The obtained S/CoMoO_(4)@rGO cathode with~52%S loading exhibits a high capacity of520.1 mA h g^(-1)after 100 cycles at 0.1 A g^(-1).Moreover,an enhanced long-term performance at high current densities(212.2 mA h g^(-1)at 4 A g^(-1)over 1000 cycles)with high Coulombic efficiency(~100%)is also achieved.This work demonstrates a novel multifunctional additive for RT Na-S battery cathodes,which is expected to promote the long-waited development towards practical applications of RT Na-S batteries.

Mechanically flexible reduced graphene oxide/carbon composite films for high-performance quasi-solid-state lithium-ion capacitors

Practical applications of diverse flexible wearable electronics require electrochemical energy storage(EES)devices with multiple configurations.Moreover,to fabricate flexible EES devices with high energy density and stability,organic integration from electrode design to device assembly is required.To address these challenges,a free-standing reduced graphene oxide(rGO)/carbon film with a unique sandwich structure has been designed via the assistance of vacuum-assistant filtration for lithium-ion capacitors(LICs).The graphene acts as not only a binder to construct a three-dimensional conductive network but also an active material to provide additional capacitive lithium storage sites,thus enabling fast ion/electron transport and improving the capacity.The designed rGO/hard carbon(rGO/HC)and rGO/activated carbon(rGO/AC)free-standing films exhibit enhanced specific capacities(513.7 mA h g^(-1)for rGO/HC and 102.8 mA h g^(-1)for rGO/AC)and excellent stability.Moreover,the integrated flexible quasi-solid-state rGO/AC//rGO/HC LIC devices possess a maximum energy density of 138.3 Wh kg^(-1),a high power density of 11 kW kg^(-1),and improved cycling performance(84.4%capacitance maintained after 10,000 cycles),superior to the AC//HC LIC(43.5%retention).Such a strategy enlightens the development of portable flexible LICs.

Green synthesis of three-dimensional magnesium ferrite/titanium dioxide/reduced graphene from Garcinia mangostana extract for crystal violet photodegradation and antibacterial activity

In this study,three-dimensional porous magnesium ferrite/titanium dioxide/reduced graphene oxide(Mg Fe_2O_(4)-GM/TiO_(2)/rGO(MGTG))was successfully synthesized via green and hydrothermal-supported co-precipitation methods using the extract of Garcinia mangostana(G.mangostana)as a reducing agent.The characterization results indicate the successful formation of the nano/micro Mg Fe_(2)O_(4)(MFO)and TiO_(2) on the structure of the reduced graphene oxide(rGO),which can also act as efficient support,alleviating the agglomeration of the nano/micro MFO and TiO_(2).The synergic effects of the adsorption and photodegradation activity of the material were investigated according to the removal of crystal violet(CV)under ultraviolet light.The effects of catalyst dosage,CV concentration,and p H on the CV removal efficiency of the MGTG were also investigated.According to the results,the CV photodegradation of the MGTG-200 corresponded to the pseudo-first-order kinetic model.The reusability of the material after 10 cycles also showed a removal efficiency of 92%.This happened because the materials can easily be recollected using external magnets.In addition,according to the effects of different free radicals·O_(2)^(-),h^(+),and·OH on the photodegradation process,the photocatalysis mechanism of the MGTG was also thoroughly suggested.The antibacterial efficiency of the MGTG was also evaluated according to the inhibition of the Gram-positive bacteria strain Staphylococcus aureus(S.aureus).Concurrently,the antibacterial mechanism of the fabricated material was also proposed.These results confirm that the prepared material can be potentially employed in a wide range of applications,including wastewater treatment and antibacterial activity.

Manufacturing N,O-carboxymethyl chitosan-reduced graphene oxide under freeze-dying for performance improvement of Li-S battery

Lithium-sulfur(Li-S) batteries can provide far higher energy density than currently commercialized lithium ion batteries, but challenges remain before it they are used in practice.One of the challenges is the shuttle effect that originates from soluble intermediates, like lithium polysulfides. To address this issue, we report a novel laminar composite, N,O-carboxymethyl chitosan-reduced graphene oxide(CC-rGO), which is manufactured via the self-assembly of CC onto GO and subsequent reduction of GO under an extreme condition of 1 Pa and-50°C. The synthesized laminar CC-rGO composite is mixed with acetylene black(AB) and coated on a commercial polypropylene(PP) membrane, resulting in a separator(CC-rGO/AB/PP) that can not only completely suppress the polysulfides penetration, but also can accelerate the lithium ion transportation, providing a Li-S battery with excellent cyclic stability and rate capability. As confirmed by theoretic simulations, this unique feature of CC-rGO is attributed to its strong repulsive interaction to polysulfide anions and its benefit for fast lithium ion transportation through the paths paved by the heteroatoms in CC.

Synthesis, properties, and applications of graphene oxide/reduced graphene oxide and their nanocomposites

Thanks to their remarkable mechanical, electrical, thermal, and barrier properties, graphene-based nanocomposites have been a hot area of research in the past decade. Because of their simple top-down synthesis, graphene oxide (GO) and reduced graphene oxide (rGO) have opened new possibilities for gas barrier, membrane separation, and stimuli-response characteristics in nanocomposites. Herein, we review the synthesis techniques most commonly used to produce these graphene derivatives, discuss how synthesis affects their key material properties, and highlight some examples of nanocomposites with unique and impressive properties. We specifically highlight their performances in separation applications, stimuli-responsive materials, anti-corrosion coatings, and energy storage. Finally, we discuss the outlook and remaining challenges in the field of practical industrial-scale production and use of graphene-derivative-based polymer nanocomposites.

Magnetic Fe_3O_4-Reduced Graphene Oxide Nanocomposites-Based Electrochemical Biosensing

An electrochemical biosensing platform was developed based on glucose oxidase(GOx)/Fe3O4-reduced graphene oxide(Fe3O4-RGO) nanosheets loaded on the magnetic glassy carbon electrode(MGCE).With the advantages of the magnetism, conductivity and biocompatibility of the Fe3O4-RGO nanosheets, the nanocomposites could be facilely adhered to the electrode surface by magnetically controllable assembling and beneficial to achieve the direct redox reactions and electrocatalytic behaviors of GOx immobilized into the nanocomposites. The biosensor exhibited good electrocatalytic activity, high sensitivity and stability. The current response is linear over glucose concentration ranging from 0.05 to 1.5 m M with a low detection limit of0.15 μM. Meanwhile, validation of the applicability of the biosensor was carried out by determining glucose in serum samples. The proposed protocol is simple, inexpensive and convenient, which shows great potential in biosensing application.

Reduced graphene oxide-grafted bovine serum albumin/bredigite nanocomposites with high mechanical properties and excellent osteogenic bioactivity for bone tissue engineering

The optimization of the scaffolds to provide a suitable matrix and accelerate the regeneration process is vital for bone tissue engineering.However,poor mechanical and biological characteristics remain the primary challenges that must be addressed.For example,although bredigite(Br)has shown great potential for application in bone tissue engineering,it easily fails in replacement.In the present work,these challenges are addressed by reinforcing the Br matrix with nanosheets of graphene oxide(rGO)that have been reduced by bovine serum albumin(BSA)in order to enhance the mechanical properties and biological behavior.The reduction of graphene oxide by BSA improves the water stability of the nanosheets and provides an electrostatic interaction between theBSA-rGO nanosheets and theBr particles.The high thermal conductivity of theBSA-rGO nanosheets decreases the porosity of the Br by transferring heat to the core of the tablet.Furthermore,the addition of BSA-rGO nanosheets into the Br matrix enhances the adhesion of G-292 cells on the surface of the tablets.These findings suggest that the tablet consisting of BSA-rGO-reinforced Br has encouraging potential for application in bone tissue engineering.

Ag/reduced graphene oxide(RGO) nanocomposites for detection of TNT

The modified Hummers method was employed to generate graphene oxide,and Ag /reduced graphene oxide (RGO) nanocomposites were synthesized at different temperatures by using sodium citrate as the reductant. Scanning electron microscopy (SEM),transmission electron microscopy (TEM),X-ray diffraction (XRD),X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were employed to characterize the reaction products. The results indicate that RGO has been synthesized successfully,and Ag particles are distributed evenly on the surface of RGO.The RGO prepared at a reaction temperature of 120℃ shows the best surface-enhanced Raman scattering (SERS) activity.The Ag /RGO nanocomposites modified by 10^- 5 mol /L 4-aminothiophenol (PATP) successfully detect a 10^- 5 mol /L 2,4,6-trinitrotoluene (TNT) alcohol solution.

Enabling High-Performance Sodium Battery Anodes by Complete Reduction of Graphene Oxide and Cooperative In-Situ Crystallization of Ultrafine SnO_(2)Nanocrystals

The main bottleneck against industrial utilization of sodium ion batteries(SIBs)is the lack of high-capacity electrodes to rival those of the benchmark lithium ion batteries(LIBs).Here in this work,we have developed an economical method for in situ fabrication of nanocomposites made of crystalline few-layer graphene sheets loaded with ultrafine SnO_(2)nanocrystals,using short exposure of microwave to xerogel of graphene oxide(GO)and tin tetrachloride containing minute catalyzing dispersoids of chemically reduced GO(RGO).The resultant nanocomposites(SnO_(2)@MWG)enabled significantly quickened redox processes as SIB anode,which led to remarkable full anode-specific capacity reaching 538 mAh g^(−1)at 0.05 A g^(−1)(about 1.45 times of the theoretical capacity of graphite for the LIB),in addition to outstanding rate performance over prolonged charge–discharge cycling.Anodes based on the optimized SnO_(2)@MWG delivered stable performance over 2000 cycles even at a high current density of 5 A g^(−1),and capacity retention of over 70.4%was maintained at a high areal loading of 3.4 mg cm^(−2),highly desirable for high energy density SIBs to rival the current benchmark LIBs.

Synthesis of Cu_2O/reduced graphene oxide composites as anode materials for lithium ion batteries

A facile way was used to synthesize Cu2O/reduced graphene oxide （rGO） composites with octahedron-like morphology in aqueous solution without any surfactant. TEM images of the obtained Cu2O/rGOs reveal that the Cu2O particles and rGO distribute hierarchically and the primary Cu2O particles are encapsulated well in the graphene nanosheets. The electrochemical performance of Cu2O/rGOs is enhanced compared with bare Cu2O when they are employed as anode materials for lithium ion batteries. The Cu2O/rGO composites maintain a reversible capacity of 348.4 mA？h/g after 50 cycles at a current density of 100 mA/g. In addition, the composites retain 305.8 mA？h/g after 60 cycles at various current densities of 50, 100, 200, 400 and 800 mA/g.

Efficient degradation of dye pollutants in wastewater via photocatalysis using a magnetic zinc oxide/graphene/iron oxide-based catalyst

In this paper, we present a proof-of-concept study of the enhancement of photocatalytic activity via a combined strategy of fabricating a visible-light responsive ternary heterostructure and improving overall photostability by incorporating magnetic zinc oxide/graphene/iron oxide (ZGF). A solvothermal approach was used to synthesize the catalyst. X-ray diffraction (XRD), scanning electron microscopic, energy dispersive X-ray, transmission electron microscopic, vibrating sample magnetometric, and ultraviolet–visible diffuse reflectance spectroscopic techniques were used to characterize the synthesized samples. The obtained optimal Zn(NO_(3))_(2) concentration, temperature, and heating duration were 0.10 mol/L, 600℃, and 1 h, respectively. The XRD pattern revealed the presence of peaks corresponding to zinc oxide, graphene, and iron oxide, indicating that the ZGF catalyst was effectively synthesized. Furthermore, when the developed ZGF was used for methylene blue dye degradation, the optimum irradiation time, dye concentration, catalyst dosage, irradiation intensity, and solution pH were 90 min, 10 mg/L, 0.03 g/L, 100 W, and 8.0, respectively. Therefore, the synthesized ZGF system could be used as a catalyst to degrade dyes in wastewater samples. This hybrid nanocomposite consisting of zinc oxide, graphene, and iron oxide could also be used as an effective photocatalytic degrader for various dye pollutants.

Three-dimensional MoS_2/reduced graphene oxide aerogel as a macroscopic visible-light photocatalyst

Photocatalysis is regarded as an ideal technology for solving the urgent environmental and energy issues that we face today.Among the reported photocatalysts,molybdenum disulfide（MoS2） is very promising for applications in hydrogen production and pollutant photodegradation.However,its lack of active sites and the difficulty of recovering catalysts in powder form have hindered its wide application.Here,we report the successful preparation of a macroscopic visible-light responsive MoS2/reduced graphene oxide（MoS2/RGO） aerogel.The obtained MoS2/RGO aerogel exhibits enhanced photocatalytic activity towards hydrogen production and photoreduction of Cr（Ⅵ） in comparison with the MoS2 powder.In addition,the low density（56.1 mg/cm^3） of the MoS2/RGO aerogel enables it to be used as an efficient adsorption material for organic pollutants.Our results demonstrate that this very promising multifunctional aerogel has potential applications in environmental remediation and clean energy production.

Metal porphyrin intercalated reduced graphene oxide nanocomposite utilized for electrocatalytic oxygen reduction

In this paper, we report a simple and facile self-assembly method to successfully fabricate cationic metal porphyrin-MtTMPyP(Mt= Cobalt(Ⅱ), Manganese(Ⅲ), or Iron(Ⅲ); TMPyP = 5, 10, 15, 20-tetrakis(N-methylpyridinium-4-yl) porphyrin) intercalated into the layer of graphene oxide(GO) by the cooperative effects of electrostatic and π-π stacking interaction between positively charged metal porphyrin and negatively charged GO sheets. Followed by reduction with hydrazine vapor, a series of novel 2 D MtTMPyP/rGO_n were fabricated. The as-prepared 2 D hybrids were fully characterized and tested as non-noble metal catalysts for oxygen reduction reaction(ORR) in an alkaline medium. The MtTMPyP/rGO_n hybrids, especially CoTMPyP/rGO_5, demonstrated an improved electrocatalytic activity for ORR and a number of exchanged electrons close to 4-electron reaction, increased stability and excellent tolerance to methanol, showing a potential alternative catalyst for ORR in fuel cells and air batteries.

Electro-conductive Nanocrystalline Cellulose Film Filled with TiO_2-ReducedGraphene Oxide Nanocomposite

Imparting electro-conductive properties to nanocellulose-based products may render them suitable for applications in electronics, optoelectronics, and energy storage devices. In the present work, an electro-conductive nanocrystalline cellulose （NCC） film filled with TiO2-reduced-graphene oxide （TiO2-RGO） was developed. Initially, graphene oxide （GO） was prepared using the modified Hummers method and thereafter photocatalytically reduced using TiO2 as a catalyst. Subsequently, an electro-conductive NCC film was prepared via vacuum filtration with the as-prepared TiO2-RGO nanocomposite as a functional filler. The TiO2-RGO nanocomposite and the NCC/TiO2-RGO film were systematically characterized. The results showed that the obtained TiO2-RGO nanocomposite exhibited reduced oxygen-containing group content and enhanced electro-conductivity as compared with those of GO. Moreover, the NCC flm flled with TiO2-RGO nanocomposite displayed an electro-conductivity of up to 9.3 S/m and improved mechanical properties compared with that of the control. This work could provide a route for producing electro-conductive NCC flms, which may hold signifcant potential as transparent ？exible substrates for future electronic device applications.

Hydrophobic and Magnetic Reduced Graphene Oxide Nanocomposite for Emulsified Oil Removal

Magnetic reduced graphene oxide(MRGO) nanocomposite was prepared by the chemical coprecipitation method and applied as adsorbent for removing emulsified oil from oily wastewater. SEM, TEM, XRD, FT-IR, VSM and other analytical methods were utilized to characterize the prepared MRGO. The adsorption performance of MRGO was evaluated under different initial adsorbate concentration, MRGO dosage, temperature, and pH value of the solution. The adsorption kinetics and isotherms were investigated. In addition, the MRGO repeatability was also tested. It was found that almost 65%of emulsified oil were removed by MRGO in the first 15 min. The MRGO adsorption capacity and efficiency for removal of adsorbate reached 335.85 mg/g and 92.52% within 60 min, respectively. The adsorption capacity reduced with an increasing MRGO dosage, while increased with the increase of emulsified oil concentration. The adsorption performance of MRGO in the alkaline environment was lower than that in the acidic environment. The adsorption data could well fit to the pseudosecondorder model. The Langmuir model could well describe the isotherm data. The MRGO adsorption capacity was still more than 236.1 mg/g at the sixth regeneration cycle.