A process to enhance the specific surface area and capacitance of hydrothermally reduced graphene oxide

Chemical and physical modification of graphene oxide nano-sheets using casein, Zn-Al layered double hydroxide, alginate hydrogel, and magnetic nanoparticles for biomedical applications

In our study, we developed a novel nanobiocomposite using graphene oxide (GO), casein (Cas), ZnAl layered double hydroxide (LDH), sodium alginate (Alg), and Fe3O4 magnetic nanoparticles. To synthesize the GO, we used a modified Hummer's method and then covalently functionalized its surface with Cas protein. The functionalized GO was combined with as-synthesized ZnAl LDH, and the composite was conjugated with alginate hydrogel through the gelation process. Finally, we magnetized the nanobiocomposite using in-situ magnetization. The nanobiocomposite was comprehensively characterized using FT-IR, FE-SEM, EDX, and XRD. Its biological potential was assessed through cell viability, hemolysis, and anti-biofilm assays, as well as its application in hyperthermia. The MTT assay showed high cell viability percentages for Hu02 cells after 24, 48, and 72 h of incubation. The nanobiocomposite had a hemolytic effect lower than 3.84 %, and the measured bacterial growth inhibition percentages of E. coli and S. aureus bacteria in the presence of the nanobiocomposite were 52.18 % and 55.72 %, respectively. At a concentration of 1 mg.mL-1 and a frequency of 400 kHz, the nanocomposite exhibits a remarkable specific absorption rate (SAR) of 67.04 W.g-1, showcasing its promising prospects in hyperthermia applications.

Occurrence and fate of pharmaceutical pollutants in wastewater: Insights on ecotoxicity, health risk, and state-of-the-art removal

Pharmaceutical active compound (PhAC) residues are considered an emerging micropollutant that enters the aquatic environment and causes harmful ecotoxicity. The significant sources of PhACs in the environment include the pharmaceutical industry, hospital streams, and agricultural wastes (animal husbandry). Recent investigations demonstrated that wastewater treatment plants (WWTPs) are an important source of PhACs discharging ecosystems. Several commonly reported that PhACs are detected in a range level from ng L-1 to μg L-1 concentration in WWTP effluents. These compounds can have acute and chronic adverse impacts on natural wildlife, including flora and fauna. The approaches for PhAC removals in WWTPs include bioremediation, adsorption (e.g., biochar, chitosan, and graphene), and advanced oxidation processes (AOPs). Overall, adsorption and AOPs can effectively remove PhACs from wastewater aided by oxidizing radicals. Heterogeneous photocatalysis has also proved to be a sustainable solution. Bioremediation approaches such as membrane bioreactors (MBRs), constructed wetlands (CWs), and microalgal-based systems were applied to minimize pharmaceutical pollution. Noteworthy, applying MBRs has illustrated high removal efficiencies of up to 99%, promising prospective future. However, WWTPs should be combined with advanced solutions, e.g., AOPs/photodegradation, microalgae-bacteria consortia, etc., to treat and minimize their accumulation. More effective and novel technologies (e.g., new generation bioremediation) for PhAC degradation must be investigated and specially designed for a low-cost and full-scale. Investigating green and eco-friendly PhACs with advantages, e.g., low persistence, no bioaccumulation, less or non-toxicity, and environmentally friendly, is also necessary.

Graphene promotes the growth of Vigna angularis by regulating the nitrogen metabolism and photosynthesis

Graphene has promising applications in agriculture and forestry. In the current study, six different concentrations of graphene (0mg/L, 0.01mg/L, 0.10mg/L, 1.00mg/L, 10.00mg/L, and 100.00mg/L) were used to investigate its effect on the growth and development of V. angularis plants in soil culture. The results showed that the group treated with 1.00mg/L graphene (G-1) had significantly increased plant height (19.86%), stem diameter (24.33%), and leaf area (13.69%), compared to the control group (CK). Moreover, all concentrations of graphene had positive effects on the total root length, total root surface area, and the number of root tips of V. angularis. Compared to the CK group, the G-1 group had significantly increased leaf water potential (37.89%), leaf conductivity (2.25%), and SOD, POD, and CAT activities (47.67%, 35.22%, and 199.3%, respectively). The G-1 group also showed improved leaf net photosynthetic rate, chlorophyll content, and soluble sugar content (51.28%, 24.25%, and 38.35%, respectively), compared to the CK group. Additionally, 1.00mg/L graphene led to a 23.88% increase in the podding rate and a 17.04% increase in the yield of V. angularis plants. The rhizosphere soil of V. angularis treated with 1.00mg/L graphene had a 25.14% increase in hydrolyzable nitrogen content and a 66.67% increase in available phosphorus content. RNA-seq data indicated that 1.00mg/L graphene induced the expression of photosynthesis and nitrogen transmembrane transport genes, including ATP synthase subunit b, photosystem I reaction center subunit XI, photosystem I reaction center subunit IV A, ferredoxin, and psbP-like protein 1, as well as genes for photosynthesis antenna proteins, glutamine synthetase, glutamate dehydrogenase 1, cyanate hydratase, protein fluG-like, and NRT1/PTR family, suggesting that graphene promoted the growth and development of V. angularis by enhancing the photosynthesis and nitrogen metabolism processes in V. angularis plants. Our results indicated that a suitable concentration of graphene could significantly promote the growth of V. angularis plants in soil.

Efficient photocatalytic bactericidal performance of green-synthesised TiO2/reduced graphene oxide using banana peel extracts

In this study, the fabrication of titanium dioxide/reduced graphene oxide (TiO2/rGO) utilising banana peel extracts (Musa paradisiaca L.) as a reducing agent for the photoinactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was explored. The GO synthesis was conducted using a modified Tour method, whereas the production of rGO involved banana peel extracts through a reflux method. The integration of TiO2 into rGO was achieved via a hydrothermal process. The successful synthesis of TiO2/rGO was verified through various analytical techniques, including X-ray diffraction (XRD), gas sorption analysis (GSA), Fourier-transform infrared (FT-IR) spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscope-energy dispersive X-ray (SEM-EDX) and transmission electron microscopy (TEM) analyses. The results indicated that the hydrothermal-assisted green synthesis effectively produced TiO2/rGO with a particle size of 60.5 nm. Compared with pure TiO2, TiO2/rGO demonstrated a reduced crystallite size (88.505 nm) and an enhanced surface area (22.664 m2/g). Moreover, TiO2/rGO featured a low direct bandgap energy (3.052 eV), leading to elevated electrical conductivity and superior photoconductivity. To evaluate the biological efficacy of TiO2/rGO, photoinactivation experiments targeting E. coli and S. aureus were conducted using the disc method. Sunlight irradiation emerged as the most effective catalyst, achieving optimal inactivation results within 6 and 4 h.

Nitrogen and sulfur functionalized microporous carbon nanomaterial derived from waste coconut husk for the efficient detection and removal of ofloxacin

This study uses waste coconut husk to synthesize carbon quantum dots decorated graphene-like structure for sustainable detection and removal of ofloxacin. The XRD spectrum shows the carbon nanomaterial's layered structure with turbostratic carbon stacking on its surface. The FESEM and HRTEM studies claim the successful development of quantum dots decorated 2D layered structure of carbon nanomaterial. The functionalization of sulfur and nitrogen is well observed and studied through XPS, while Raman spectra have provided insight into the surface topology of the as-synthesized nanostructure. The BET surface area was found to be 1437.12 m2/g with a microporous structure (pore width 2.0 nm) which interestingly outcompete many reported carbon-based nanomaterials such as graphene oxide, reduced graphene oxide and quantum dots. The detection and removal processes are monitored through UV-visible spectroscopy and the obtained detection limit and adsorption capacity were 2.7 nM and 393.94 mg/L respectively. Additionally, 1 mg carbon nanomaterial has removed 49 % ofloxacin from water in just 1 h. In this way, this study has successfully managed the coconut husk waste after its utilization for environmental remediation purposes.

Graphene nanowalls grown on copper mesh

Graphene nanowalls (GNWs) can be described as extended nanosheets of graphitic carbon where the basal planes are perpendicular to a substrate. Generally, existing techniques to grow films of GNWsare based on plasma-enhanced chemical vapor deposition (PECVD) and the use of diverse substrate materials (Cu, Ni, C, etc) shaped as foils or filaments. Usually, patterned films rely on substrates priorly modified by costly cleanroom procedures. Hence, we report here the characterization, transfer and application of wafer-scale patterned GNWsfilms that were grown on Cu meshes using low-power direct-current PECVD. Reaching wall heights of ∼300 nm, mats of vertically-aligned carbon nanosheets covered square centimeter wire meshes substrates, replicating well the thread dimensions and the tens of micrometer-wide openings of the meshes. Contrastingly, the same growth conditions applied to Cu foils resulted in limited carbon deposition, mostly confined to the substrate edges. Based on the wet transfer procedure turbostratic and graphitic carbon domains co-exist in the GNWsmicrostructure. Interestingly, these nanoscaled patterned films were quite hydrophobic, being able to reverse the wetting behavior of SiO2surfaces. Finally, we show that the GNWscan also be used as the active material for C-on-Cu anodes of Li-ion battery systems.

Unveiling the Reduction Process of Graphene Oxide by Ascorbic Acid: Grafting and Reduction Sequences for High Surface Area Graphene Materials

This work reports the synthesis of high surface area reduced graphene oxides using L-ascorbic acid as a reducing agent by precisely controlling the interaction between graphene oxide and L-ascorbic acid. Based on the structural characterization, such as textural properties (specific surface area, pore structure), crystallinity, and carbon chemical state, we identified that the temperature and reaction time are critical parameters to control the stacking degree of the final reduced product. Besides, by performing a time course analysis of the reaction, we identified the side products of the reducing agent by LC-MS and verified the reduction mechanism. Following our results, we proposed an optimum condition for producing a graphene derivative adsorbent with a high surface area. This graphene derivative was tested in an aqueous solution with organic and inorganic pollutants such as methylene blue, methyl orange, and cadmium.

Recent progresses, challenges, and opportunities of carbon-based materials applied in heavy metal polluted soil remediation

The application of carbon-based materials (CBMs) for heavy metal polluted soil remediation has gained growing interest due to their versatile properties and excellent remediation performance. Although the progresses on applications of CBMs in removing heavy metal from aqueous solution and their corresponding mechanisms were well known, comprehensive review on applications of CBMs in heavy metal polluted soil remediation were less identified. Therefore, this review provided insights into advanced progresses on utilization of typical CBMs including biochar, activated carbon, graphene, graphene oxide, carbon nanotubes, and carbon black for heavy metal polluted soil remediation. The mechanisms of CBM remediation of heavy metals in soil were summarized, mainly including physical adsorption, precipitation, complexation, electrostatic interaction, and cationic-π coordination. The key factors affecting the remediation effect include soil pH, organic matter, minerals, microorganisms, coexisting ions, moisture, and material size. Disadvantages of CBMs were also included, such as: potential health risks, high cost, and difficulty in achieving co-passivation of anions and cations. This work will contribute to our understanding of current research advances, challenges, and opportunities for CBMs remediation of heavy metal-contaminated soils.

Hybrid Carbon Supports Composed of Small Reduced Graphene Oxide and Carbon Nanotubes for Durable Oxygen Reduction Catalysts in Proton Exchange Membrane Fuel Cells

We demonstrated highly active and durable hybrid catalysts (HCs) composed of small reduced graphene oxide (srGO) and carbon nanotubes (CNTs) for use as oxygen reduction reaction (ORR) catalysts in proton exchange membrane fuel cells. Pt/srGO and Pt/CNTs were prepared by loading Pt nanoparticles onto srGO and CNTs using a polyol process, and HCs with different Pt/CNT and Pt/srGO ratios were prepared by mechanically mixing the two components. The prepared HCs consisted of Pt/CNTs well dispersed on Pt/srGO, with catalyst HC55, which was prepared using Pt/srGO and Pt/CNTs in a 5:5 ratio, exhibiting excellent oxygen reduction performance and high stability over 1000 cycles of the accelerated durability test (ADT). In particular, after 1000 cycles of the ADT, the normalized electrochemically active surface area of Pt/HC55 decreased by 11.9%, while those of Pt/srGO and Pt/C decreased by 21.2% and 57.6%, respectively. CNTs have strong corrosion resistance because there are fewer defect sites on the surface, and the addition of CNTs in rGO further improved the durability and the electrical conductivity of the catalyst. A detailed analysis of the structural and electrochemical properties of the synthesized catalysts suggested that the synergetic effects of the high specific surface area of srGO and the excellent electrical conductivity of CNTs were responsible for the enhanced efficiency and durability of the catalysts.

Improving Electroactivity of N-Doped Graphene Derivatives with Electrical Induction Heating

Graphene derivatives doped with nitrogen have already been identified as active non-noble metal materials for oxygen reduction reaction (ORR) in PEM and alkaline fuel cells. However, an efficient and scalable method to prepare active, stable, and high-surface-area non-noble metal catalysts remains a challenge. Therefore, an efficient, potentially scalable strategy to improve the specific surface area of N-doped graphene derivatives needs to be developed. Here, we report a novel, rapid, and scalable electrical induction heating method for the preparation of N-doped heat-treated graphene oxide derivatives (N-htGOD) with a high specific surface area. The application of the induction heating method has been shown to shorten the reaction time and improve the energy efficiency of the process. The materials synthesized by induction heating exhibited very high specific surface area and showed improved ORR activity compared to the conventional synthesis method. Moreover, we demonstrated that the temperature program of induction heating could fine-tune the concentration of nitrogen functionalities. In particular, the graphitic-N configuration increases with increasing final temperature, in parallel with the increasing ORR activity. The presented results will contribute to the understanding and development of nonmetal N-htGOD for energy storage and conversion applications.

Synergetic Effect of Polyaniline and Graphene in Their Composite Supercapacitor Electrodes: Impact of Components and Parameters of Chemical Oxidative Polymerization

The current development of clean and high efficiency energy sources such as solar or wind energy sources has to be supported by the design and fabrication of energy storage systems. Electrochemical capacitors (or supercapacitors (SCs)) are promising devices for energy storage thanks to their highly efficient power management and possible small size. However, in comparison to commercial batteries, SCs do not have very high energy densities that significantly limit their applications. The value of energy density directly depends on the capacitance of full SCs and their cell voltage. Thus, an increase of SCs electrode specific capacitance together with the use of the wide potential window electrolyte can result in high performance SCs. Conductive polymer polyaniline (PANI) as well as carbonaceous materials graphene (G) or reduced graphene oxide (RGO) have been widely studied for usage in electrodes of SCs. Although pristine PANI electrodes have shown low cycling stability and graphene sheets can have low specific capacitance due to agglomeration during their preparation without a spacer, their synergetic effect can lead to high electrochemical properties of G/PANI composites. This review points out the best results for G/PANI composite in comparison to that of pristine PANI or graphene (or RGO). Various factors, such as the ratio between graphene and PANI, oxidants, time, and the temperature of chemical oxidative polymerization, which have been determined to influence the morphology, capacitance, cycling stability, etc. of the composite electrode materials measured in three-electrode system are discussed. Consequently, we provide an in-depth summary on diverse promising approaches of significant breakthroughs in recent years and provide strategies to choose suitable electrodes based on PANI and graphene.

High-Capacity Ti3C2Tx MXene Electrodes Achieved by Eliminating Intercalated Water Molecules Using a Co-solvent System

Synthesizing layered transition-metal carbides, MXenes, with a mesoporous structure remains challenging but is highly useful because it converts the laminated two-dimensional structures into versatile porous materials. Hydrogen bonds between intercalated H₂O molecules and oxygen terminal groups on the surface are formed in aqueous solution processes, and this is a determining factor of surface area. We developed an extraction method to remove intercalated water molecules based on a simple intermolecular force attraction strategy in a co-solvent system using a combination of polar-protic/-aprotic and non-polar solvents. As a result, self-aggregated mesoporous Ti₃C₂T_x was realized without any additives. The dipole-dipole interaction between H₂O and CHCl₃ molecules under non-polar solvent conditions assists the extraction of intercalated H₂O from the MXene suspension, which can form a self-aggregated morphology (not re-stacked horizontally). The process yields Ti₃C₂T_x with a layered structure of embedded mesopores and a specific surface area that is 13-fold higher than that of standard MXene. Electrodes made with the resulting MXene exhibited a larger specific capacitance of 224 F/g (1 A/g), with an improved cyclic retention of 96.4%@10,000 cycles. This intermolecular attraction-induced approach, involving the manipulation of morphology, is simple to mass-produce and can be used for MXene-based electrochemical applications.

Investigating the thermal stability of metallic and non-metallic nanoparticles using a novel graphene oxide-based transmission electron microscopy heating-membrane

In recent years, graphene has been explored as a heating membrane for studying high-temperature dynamics inside the transmission electron microscope (TEM) due to several limitations with the existing silicon nitride-based membrane. However, the transfer of monolayer graphene films for TEM experiments is challenging and requires many complicated steps with a minimum success rate. This work developed a novelin situheating platform by combining the graphene oxide (GO) flakes in the pre-patterned chips. The isolated GO flake was self-suspended between the metal electrodes by a simple drop-casting process. The GO was reduced and characterized using Raman and electron energy-loss spectroscopy. Furthermore, a GO-based heater was used to investigate the thermal stability of gold and silica nanoparticles. The gold nanoparticles evaporated non-uniformly and left an empty carbon shell, while silica disappeared uniformly by etching carbon support. We successfully demonstrated a GO flake as a heating membrane to study high temperature thermal dynamic reactions: melting/evaporation, agglomeration, Rayleigh instability, and formation/or removal of carbon in the nanoparticles.

Reduced Graphene Oxide—Polycarbonate Electrodes on Different Supports for Symmetric Supercapacitors

Electrode materials for electrochemical capacitors or supercapacitors (SCs) are widely studied, as they are needed for the development of energy storage devices in electrical vehicles and flexible electronics. In the current work, a self-supported paper of reduced graphene oxide (rGO) with polycarbonate (PC) (as rGO-PC composite) was prepared by simple vacuum filtration and low-temperature annealing. rGO-PC as a freestanding single electrode was studied in a three-electrode system and presented a capacitive energy storage mechanism. To fabricate SCs based on rGO-PC, flexible polyethylene terephthalate (PET) with layers of both Cu tape (Cu tape) and carbon tape (C tape) (PET/Cu/C), as well as PET covered by graphene ink (PET/GrI), were used as supports. Fabricated flexible symmetric SCs have shown similar behavior with a higher areal capacitance value than that on PET/Cu/C substrate.

Electrode-Electrolyte Interactions in an Aqueous Aluminum-Carbon Rechargeable Battery System

Being environmentally friendly, safe and easy to handle, aqueous electrolytes are of particular interest for next-generation electrochemical energy storage devices. When coupled with an abundant, recyclable and low-cost electrode material such as aluminum, the promise of a green and economically sustainable battery system has extraordinary appeal. In this work, we study the interaction of an aqueous electrolyte with an aluminum plate anode and various graphitic cathodes. Upon establishing the boundary conditions for optimal electrolyte performance, we find that a mesoporous reduced graphene oxide powder constitutes a better cathode material option than graphite flakes.

Efficient Use of Graphene Oxide and Silica Fume in Cement-Based Composites

Incorporation of graphene oxide (GO) and silica fume (SF) to cement composites enhances their mechanical properties if suitable proportional amounts of GO and SF are used. This study presents a simplified approach to determine experimentally the optimum GO and SF contents that should be added to the cementitious mixture to obtain a proper and stable dispersion of GO sheets within the cement matrix. Composite mortar specimens with different GO and SF contents were designed and tested under flexural and compression loading. The phase formation and the microstructure of selected samples were also investigated to give an in-depth interpretation of the test results. The main criterion to determine the GO and SF contents was the ultimate strength required of the GO–cement composite. It was found that there was a composite interaction between the SF and GO contents in the cementitious mixture, which an envelope surface could describe if all other mix design parameters are kept constant.

Evaluation of tire derived rubber (TDR) fixed biofilm reactor (FBR) for remediation of Methylene blue dye from wastewater

The present investigation is focused on development of aerobic biofilm on tire-derived rubber (TDR) media and then evaluation of such system for bioremediation of Methylene blue (MB) dye for 9 weeks. After 9 weeks of operation, the COD, BOD, ammonia and color values have been declined by 89.2%, 98.3%, 99.61% and 99.81%, respectively, While SEM-EDX results showed a variance in weight percent of various elements in TDR without biofilm i.e. raw TDR media, as well as in the 1st and 9th-week samples. Moreover, fine and strong peaks were observed in both the MB simulated wastewater and 9th week TDR samples at 1190, 1300, 1400, 1450, 1500 and 1618 cm^-1 respectively by Raman Spectroscopic analysis. Further, FTIR analysis was performed for the MB simulated wastewater, and absorbance peaks ranging from 1591 to 1363 cm^-1 and 3410 cm^-1 were observed in all the samples with different intensities. To assess the biodeterioration of the TDR media, ATR was performed for the raw, 1st, 2nd and 9th week TDR media samples and in the raw TDR, two important bands, 842 and 2962 cm^-1 were noticed representing -CH = CH and -CH₃. A clear variation of bands and peak intensities were observed in different support media samples. The results indicate that TDR media is a resilient, chemically resistant material and could be employed for the biofilm growth for biological treatment of textile dye wastewater.

Graphene aerogels via hydrothermal gelation of graphene oxide colloids: Fine-tuning of its porous and chemical properties and catalytic applications

Recently, 3D graphene aerogel has garnered a high interest aiming at benefiting of the excellent properties of graphene in devices for energy storage or environmental remediation. Hydrothermal gelation of GO dispersion is a straightforward method that offers many opportunities for tuning its properties and for processing it to devices. By adjusting hydrothermal gelation and drying conditions, it is possible to tune the density (from ~3 mg cm^-3 to ~2 g cm^-3), pore volume, pores size (micro to macropores), pore distribution, surface chemical polarity (hydrophobic or hydrophilic), and electrical conductivity (from ~0.5 S m^-1 to S cm^-1). Besides other well explored applications in energy storage or environmental remediation, graphene aerogels have excellent prospects as support for catalysis since they combine the advantages of graphene sheets (high surface area, high electrical conductivity, surface chemistry tunability, high adsorption capacity…) while circumventing their drawbacks such as difficult separation from reaction media or tendency to stacking. Compared to other 3D porous carbon materials used as catalyst support, graphene aerogels have unique porous structure. The pore walls are the thinnest to be expected for a carbon material (the thickness of monolayer graphene is 0.335 nm), hence leading to the highest exposed surface area per weight and even per volume for compacted aerogels. This has the potential to maximize the catalytic site density per reactor mass and volume while minimizing the pressure drop for continuous reactions in flow. Herein, different strategies to control the porous texture, chemical and physical properties are revised along with their processability and scalability for the implementation into different morphologies and devices. Finally, the application of graphene aerogels in the catalysis field are overviewed, giving a perspective about future directions needing further research.

Porous Graphene Composite Polymer Fibres

Since the isolation of graphene, there have been boundless pursuits to exploit the many superior properties that this material possesses; nearing the two-decade mark, progress has been made, but more is yet to be done for it to be truly exploited at a commercial scale. Porous graphene (PG) has recently been explored as a promising membrane material for polymer composite fibres. However, controlling the incorporation of high surface area PG into polymer fibres remain largely unexplored. Additionally, most polymer-graphene composites suffer from low production rates and yields. In this paper, graphene-loaded microfibres, which can be produced at a very high rate and yield have been formed with a carrier polymer, polycaprolactone. For the first time, PG has been incorporated into polymer matrices produced by a high-output manufacturing process and analysed via multiple techniques; scanning electron microscopy (SEM), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Raman spectra showed that single layer graphene structures were achieved, evidence for which was also backed up by the other techniques. Fibres with an average diameter ranging from 3-8 μm were produced with 3-5 wt% PG. Here, we show how PG can be easily processed into polymeric fibres, allowing for widespread use in electrical and ultrafiltration systems.

Graphene Oxides Derivatives Prepared by an Electrochemical Approach: Correlation between Structure and Properties

Graphene oxide (GO) can be defined as a single monolayer of graphite with oxygen-containing functionalities such as epoxides, alcohols, and carboxylic acids. It is an interesting alternative to graphene for many applications due to its exceptional properties and feasibility of functionalization. In this study, electrochemically exfoliated graphene oxides (EGOs) with different amounts of surface groups, hence level of oxidation, were prepared by an electrochemical two-stage approach using graphite as raw material. A complete characterization of the EGOs was carried out in order to correlate their surface topography, interlayer spacing, defect content, and specific surface area (SSA) with their electrical, thermal, and mechanical properties. It has been found that the SSA has a direct relationship with the d-spacing. The EGOs electrical resistance decreases with increasing SSA while rises with increasing the D/G band intensity ratio in the Raman spectra, hence the defect content. Their thermal stability under both nitrogen and dry air atmospheres depends on both their oxidation level and defect content. Their macroscopic mechanical properties, namely the Young’s modulus and tensile strength, are influenced by the defect content, while no correlation was found with their SSA or interlayer spacing. Young moduli values as high as 54 GPa have been measured, which corroborates that the developed method preserves the integrity of the graphene flakes. Understanding the structure-property relationships in these materials is useful for the design of modified GOs with controllable morphologies and properties for a wide range of applications in electrical/electronic devices.

Silver-Decorated Cobalt Ferrite Nanoparticles Anchored onto the Graphene Sheets as Electrode Materials for Electrochemical and Photocatalytic Applications

The present work describes the synthesis of Ag-CoFe₂O₄/rGO nanocomposite as a photocatalyst through the hydrothermal process by the attachment of silver and cobalt ferrite (CoFe₂O₄) nanoparticles on the surface of reduced graphene oxide. The effect of Ag and reduced graphene oxide (rGO) on the structure, optical, magnetic, photocatalytic, and electrochemical performance of the CoFe₂O₄ is systematically explored through various analytical techniques. The analyses of the observed outcomes reveal that the graphene sheets are exfoliated and decorated with well-dispersed Ag and CoFe₂O₄ nanoparticles. UV-vis spectra indicate a gradual shift in the absorption edge toward the higher wavelength with the addition of Ag ions, which signifies variation in the energy gap of the samples. Photoluminescence results divulge that graphene can decline the electron-hole recombination rate and improve the photocatalytic activity of the Ag-CoFe₂O₄/rGO nanocomposite. In this context, the Ag-CoFe₂O₄/rGO sample presents good catalytic activity as compared to the CoFe₂O₄ and Ag-CoFe₂O₄ photocatalysts for the degradation of methylene blue (MB) dye and suggests that the rGO plays a vital role in the Ag-CoFe₂O₄/rGO nanocomposite. The deterioration rate of the samples is found to be in the order of CoFe₂O₄(78.03%) < Ag-CoFe₂O₄(83.04%) < Ag-CoFe₂O₄/rGO(93.25%) in 100 min for MB dye, respectively, under visible-light irradiation. The room-temperature ferromagnetic behavior of the samples is confirmed by the M-H hysteresis loop measurements. Overall, the Ag-CoFe₂O₄/rGO nanocomposite promises to be a strong magnetic photocatalyst for contaminated wastewater treatment. The electrochemical performance of all of the samples was examined by the cyclic voltammetry (CV) that exhibits a superior rate performance and cycle stability of the Ag-CoFe₂O₄/rGO nanocomposite as compared to the other samples.

One-Pot Synthesis of Sulfur-Doped TiO2/Reduced Graphene Oxide Composite (S-TiO2/rGO) With Improved Photocatalytic Activity for the Removal of Diclofenac From Water

Sulfur-doped TiO2 (S-TiO2) composites with reduced graphene oxide (rGO), wt. % of rGO equal to 0.5%, 2.75%, and 5.0%, were prepared by a one-pot solvothermal procedure. The aim was to improve photocatalytic performance in comparison to TiO2 under simulated solar irradiation for the treatment of diclofenac (DCF) in aqueous medium. The obtained composites were characterized for physical-chemical properties using thermogravimetric analysis (TGA), X-ray diffractograms (XRD), Raman, scanning electron microscopy (SEM)/energy dispersive X-ray (EDX), Brauner Emmett Teller (BET), and photoluminescence (PL) analyses, indicating successful sulfur doping and inclusion of rGO. Sulfur doping and rGO have successfully led to a decrease in photogenerated charge recombination. However, both antagonistic and synergistic effects toward DCF treatment were observed, with the latter being brought forward by higher wt.% rGO. The composite with 5.0 wt.% rGO has shown the highest DCF conversion at pH 4 compared to that obtained by pristine TiO2, despite lower DCF adsorption during the initial dark period. The expected positive effects of both sulfur doping and rGO on charge recombination were found to be limited because of the subpar interphase contact with the composite and incomplete reduction of the GO precursor. Consequent unfavorable interactions between rGO and DCF negatively influenced the activity of the studied S-TiO2/rGO photocatalyst under simulated solar irradiation.

Chemical and Structural Analysis of Carbon Materials Subjected to Alkaline Oxidation

Redox species such as transition metals may, unknowingly, integrate carbon materials that are produced (or supplied) for the assembling of electrodes in batteries, supercapacitors, and fuel cells. The extent to which these species alter the electrochemical profile of carbons and affect the performance and/or degradation of energy storage systems is still not fully appreciated. Alkaline oxidation (or fusion) is a promising approach to disintegrate nanocarbons for the subsequent study of their chemical composition by routine analytical tools. In this work, three commercial carbon powders, relevant for electrochemical applications and bearing varied textural orientation (point, radial, and planar), were selected to evaluate the versatility of fusion as a pretreatment process for elemental analysis. Additionally, the interaction of the flux, a lithium borate salt, with the carbons was elucidated by examining their post-fusion residues. The degree of structural degradation varied and, generally, the doping with Li and/or B (whether substitutional or interstitial) was low to nonexistent. With future developments, fusion could become a relevant pretreatment method to analyze the composition of carbon materials, even when complex mixtures (e.g., cycled battery electrodes) and larger batch scales are considered.

The efficient profiling of serum N-linked glycans by a highly porous 3D graphene composite

In this work, an enrichment approach for the profiling of N-linked glycans was developed by utilizing a highly porous 3D graphene composite fabricated from graphene oxide nanosheets and a phenol-formaldehyde polymer via graphitization and KOH activation. In tailoring the large surface area (ca. 2213 m² g^-1) and 3D-layered mesoporous structure, the 3D graphene composite demonstrated not only high efficiency in glycan enrichment but also the size-exclusion effect against residual protein interference. For a standard protein ovalbumin digest, 26 N-linked glycans were identified with good repeatability, and the detection limit was as low as 0.25 ng μL^-1 with the identification of 13 N-linked glycans (S/N > 10). When the mass ratio of the ovalbumin digest to the interfering proteins, i.e., bovine serum albumin and ovalbumin was 1 : 2000 : 2000, 18 N-linked glycans could still be detected with sufficient signal intensities. From a 60 nL minute complex human serum sample, up to 53 N-linked glycans with S/N > 10 were identified after the 3D graphene enrichment, while only 20 N-linked glycans were identified by the porous graphitized carbon material used for comparison. In addition, the application of the 3D graphene composite in profiling the up-regulated and down-regulated N-linked glycans from the real clinical serum samples of ovarian cancer patients confirmed the potential of the 3D graphene composite for analyzing minute and complicated biological samples.

Cobalt ferrite supported on reduced graphene oxide as a T2 contrast agent for magnetic resonance imaging

Nanoscaled spinel-structured ferrites bear promise as next-generation contrast agents for magnetic resonance imaging. However, the small size of the particles commonly leads to colloidal instability under physiological conditions. To circumvent this problem, supports onto which the dispersed nanoparticles can be anchored have been proposed. Amongst these, flakes of graphene have shown interesting performance but it remains unknown if and how their surface texture and chemistry affect the magnetic properties and relaxation time (T₂) of the ferrite nanoparticles. Here, it is shown that the type of graphene oxide (GO) precursor, used to make composites of cobalt ferrite (CoFe₂O₄) and reduced GO, influences greatly not just the T₂ but also the average size, dispersion and magnetic behaviour of the grafted nanoparticles. Accordingly, and without compromising biocompatibility, a judicious choice of the initial GO precursor can result in the doubling of the proton relaxivity rate in this system.

In a one-pot hydrothermal synthesis of MRI-active CoFe₂O₄ nanoparticles grafted onto graphene flakes, careful selection of the parent graphene oxide enables major increments in grafting yield and proton relaxivity rates.

Mesoporous Reduced Graphene Oxide as a High Capacity Cathode for Aluminum Batteries

Research in the field of aluminum batteries has focused heavily on electrodes made of carbonaceous materials. Still, the capacities reported for these multivalent systems remain stubbornly low. It is believed that a high structural quality of graphitic carbons and/or specific surface areas of >1000 m² g^-1 are key factors to obtain optimal performance and cycling stability. Here an aluminum chloride battery is presented in which reduced graphene oxide (RGO) powder, dried under supercritical conditions, is used as the active cathode material and niobium foil as the current collector. With a specific surface area of just 364 m² g^-1 , the RGO enables a gravimetric capacity of 171 mAh g^-1 at 100 mA g^-1 and remarkable stability over a wide range of current densities (<15% decrease over 100 cycles in the interval 100-20000 mA g^-1 ). These properties, up to now achieved only with much larger surface area materials, result from the cathode's tailored mesoporosity. The 20 nm wide mesopores facilitate the movement of the chloroaluminate ions through the RGO, effectively minimizing the inactive mass content of the electrode. This more than compensates for the ordinary micropore volume of the graphene powder.

A facile synthesis of porous graphene for efficient water and wastewater treatment

The use of two-dimensional graphene-based materials in water treatment has recently gained significant attention due to their unique electronic and thermal mobility, high surface area, high mechanical strength, excellent corrosion resistance and tunable surface chemistry. However, the relatively expensive, poor hydrophobicity, low adsorption capacity and recyclability, and complex post-treatment of the most pristine graphene frameworks limit their practical application. Here, we report a facile scalable method to produce highly porous graphene from reduced graphene oxide via thermal treatment without addition of any catalyst or use of any template. Comparing to conventional graphene counterparts, as-prepared porous graphene nanosheets showed evident improvement in hydrophobicity, adsorption capacity, and recyclability, making them ideal candidate materials for water treatment. Superhydrophobic and superoleophilic porous graphene prepared in this work has been demonstrated as effective absorbents for a broad range of ions, oils and organic solvents, exhibiting high selectivity, good recyclability, and excellent absorption capacities > 90%. The synthesis method of porous graphene reported in this paper is easy to implement, low cost and scalable. These attributes could contribute towards efficient and cost-effective water purification and pollution reduction.

One-pot synthesis of amine-functionalized graphene oxide by microwave-assisted reactions: an outstanding alternative for supporting materials in supercapacitors

A simple and straightforward method using microwave-assisted reactions is presented for the functionalization of graphene oxide with aromatic and non-aromatic amines, notedly dibenzylamine (DBA), p-phenylenediamine (PPD), diisopropylamine (DPA) and piperidine (PA). The as-synthesized amine-functionalized graphene oxide materials (amine-GO) were characterized using spectroscopic techniques including XRD, FTIR, ¹³C NMR, XPS, TEM for imaging and thermogravimetric analysis (TGA). The characterization confirmed the functionalization for all amines, reaching relatively high surface nitrogen atomic concentrations of up to 8.8%. The investigations of electrochemical behavior for the amine-GOs show the significant improvement in GO's electrochemical properties through amine functionalization, exhibiting long life cycle stability and reaching specific capacitance values of up to 290 F g⁻¹ and 260 F g⁻¹ for GO-PA and GO-DPA samples, respectively, confirming their potential application as alternative supporting materials in supercapacitors.

A simple and straightforward method using microwave-assisted reactions is presented for the functionalization of graphene oxide with aromatic and non-aromatic amines.

A facile hydrothermal synthesis of graphene/RuO2/Co3O4 nanocomposites with high pseudocapacity

The combination of three materials is innovative and the mechanisms of chemical transformation and the electrochemical process are insightfully discussed.