Rheological and Flexural Strength Characteristics of Cement Mixtures through the Synergistic Effects of Graphene Oxide and PVA Fibers

This study investigates the synergistic effects of incorporating graphene oxide (GO) and polyvinyl alcohol (PVA) fibers into cement paste mixtures, aiming to modify their rheological properties and flexural behaviors with resistance to crack formation. The relationship between static yield stress and critical shear strain was examined in ten cement paste mixtures with varying concentrations of 6 mm and 12 mm PVA fibers and 0.05% GO. Additionally, viscosity analyses were performed. For the specimens fabricated from these mixtures, flexural strength tests were conducted using the Digital Image Correlation (DIC) technique for precise strain analysis under load history. The results indicated a significant increase in static yield stress, viscosity, and critical shear strain due to the combined addition of GO and PVA fibers, more so than when added individually. Notably, in PVA fiber-reinforced cement mixtures, the integration of GO increased the crack initiation load by up to 23% and enhanced pre-crack strain by 30 to 50%, demonstrating a notable delay in crack initiation and a reduction in crack propagation. Microstructural analyses using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) revealed a concentrated presence of GO around and on the PVA fibers. This promotes increased C-S-H gel formation, resulting in a denser microstructure. Additionally, GO effectively interacts with PVA fibers, enhancing the adherence of hydration products at their interface.

A DFT investigation of the catalytic oxidation of benzyl alcohol using graphene oxide

CONTEXT

Metal-free heterogeneous materials have attracted great interest due to their potential to facilitate various organic transformations in line with circular economy and green chemistry principles. Among various 2D materials, graphene oxide (GO) is considered an attractive material for numerous applications in physics, chemistry, biology, material sciences, and catalysis. Furthermore, graphene-based catalysts exhibit good catalytic activity toward the selective oxidation of benzyl alcohol to benzaldehyde or benzoic acid under eco-friendly conditions. In this regard, a theoretical investigation was carried out to study both catalytic oxidation reaction pathways (i.e., benzyl alcohols to aldehyde and to benzoic acid) using GO as an eco-friendly and metal-free catalyst.

METHODS

In this study, we report a theoretical investigation at the B3LYP/6-31G level to better understand the oxidation of benzyl alcohol using GO as a metal-free catalyst. The possible bond formation was investigated using the global and local reactivity indexes derived from Fukui functions. Furthermore, we performed a non-covalent interaction (NCI) analysis to unveil the stability and the interaction nature between both reagents and GO surface. The effect of the solvent on the oxidation efficiency was also performed and the results indicate that the solvent significantly affects the decrease of reactivity by increasing the activation barriers through oxidation reactions of benzyl alcohol. Additionally, the electron localization function (ELF) analysis was performed for all intermediates showing the ionic nature of the studied epoxide structure of GO and rules out any type of covalent interaction during the oxidation reaction of benzyl alcohol. All these obtained results are in good agreement with experimental observations and reveal that the epoxide functions on the graphene surface promote an excellent catalyst turnover.

Enhancing High-Capacity and High-Rate Sodium-Ion Storage through Synergistic N,S Dual Doping of Hard Carbon

Hard carbon, as the most promising commercial anode materials of sodium-ion batteries (SIBs), has suffered from the coupling limitations on initial Coulombic efficiency (ICE), capacity, and rate capability. Herein, to break such coupling limitations, sulfur-rich nitrogen-doped carbon nanomaterials (S-NC) were synthesized by a synergistic modification strategy, including structure/morphology regulation and dual heteroatom doping. The small specific surface area of S-NC is beneficial for inhibiting excessive growth of solid electrolyte interphase (SEI) film and irreversible interfacial reaction. The covalent S can serve as active electrochemical sites by Faradaic reactions and provide extra capacity. Benefit by N, S co-doping, S-NC shows large interlayer spacing, high defects, good electronic conductivity, strong ion adsorption performance, and fast Na+ ion transport, which combined with a more significant pore volume result in speedier reaction kinetics. Hence, S-NC possesses a high reversible specific capacity of 464.7 mAh g-1 at 0.1 A g-1 with a high ICE of 50.7%, excellent rate capability (209.8 mAh g-1 at 10.0 A g-1 ), and superb long-cycle capability delivering a capacity of 229.0 mAh g-1 (85% retention) after 1800 cycles at 5.0 A g-1 .

Anti-Infective and Toxicity Properties of Carbon Based Materials: Graphene and Functionalized Carbon Nanotubes

Recently, antimicrobial activities of various carbon-based nanomaterials against specific pathogens have become one of the most significant research interests in this field. Carbon nanotubes (CNTs) are promising multidisciplinary nanostructures in biomedicine, drug delivery, genetic engineering, biosensors, and artificial implants. However, the biomedical administration of CNTs is dependent on their solubility, toxicity, and biocompatibility, as well as novel drug-delivery applications through optimization of the drug's loading capacity, cellular absorption, and continuous release within the target cell. The usage of CNTs and Graphene materials as antimicrobial agents and nanocarriers for antibiotics delivery would possibly improve their bioavailability and facilitate better anti-infective therapy. However, it is worth mentioning that CNTs' antimicrobial activity and toxicity are highly dependent on their preparation and synthesis method. Various types of research have confirmed that diameter, length, residual catalyst, metal content, surface coating, electronic structure, and dispersibility would affect CNTs' toxicity toward bacteria and human cells. In this review article, a general study was performed on the antimicrobial properties of carbon-based nanomaterials, as well as their toxicity and applications in confronting different microorganisms. This study could be useful for researchers who are looking for new and effective drug delivery methods in the field of microbial resistance.

Interfacial Distribution of Nafion Ionomer Thin Films on Nitrogen-Modified Carbon Surfaces

Chemically modified carbon supports for the cathode catalyst layers of polymer electrolyte fuel cells (PEFCs) show considerable promise for boosting the oxygen reduction reaction. This study evaluated the ionomer distribution of Nafion ionomer thin films on nitrogen (N)-modified carbon surfaces along their depth direction. Neutron reflectivity (NR) measurements performed using the double-contrast technique with H2O and D2O revealed that the introduction of N functional groups to carbon thin films promoted ionomer adsorption onto the surface under wet conditions (22 °C, 85% relative humidity). Molecular dynamics (MD) simulations conducted to verify the origin of the robust contact between the ionomer and N-modified carbon surface revealed an ionomer adsorption mechanism on the N-modified carbon surfaces, which involved Coulomb interactions between the positively charged carbon surface and the ionomer side chains with negatively charged sulfonic acid groups. The positive surface charge, which was determined using the contents of the N functional groups estimated by X-ray photoelectron spectroscopy, was found to be sufficient as an impetus for ionomer adsorption. This strategy involving NR measurements and MD simulations can provide insights into the solid-ionomer interfacial structures in a cathode catalyst layer and can therefore be extensively employed in studies on PEFCs.

Bioinspired Dual-Driven Binary Heterogeneous Nanofluidic Ionic Diodes

Recently, bioinspired 2D material-based nanofluidic systems with unique properties and advantages have been receiving considerable research interest and getting rapid development. However, it remains a huge challenge to integrate adaptive responsiveness to external stimuli and asymmetric ion transport characteristics into the 2D nanofluidic systems. Herein, we report a dual-driven switchable asymmetric ionic transport phenomenon through a graphene oxide-based heterogeneous 2D nanofluidic membrane. Taking advantage of the formation of a charge heterojunction induced by the variation of pH or UV irradiation, a maximum ionic current rectification (ICR) ratio of ca. 56 for pH or 140 for light was achieved. Such smart nanofluidic devices with pH and light dual-responsiveness and asymmetric ion transport behaviors provide a universal strategy for potential applications in chemical sensing, water treatment, and energy conversion and establish a promising platform for exploring advanced quantum ionics biodevices with ultrafast signal transmission, nanochannel-structured bioreactors with high efficiency, etc.

Graphene-based nanocomposites and nanohybrids for the abatement of agro-industrial pollutants in aqueous environments

Incessant release of a large spectrum of agro-industrial pollutants into environmental matrices remains a serious concern due to their potential health risks to humans and aquatic animals. Existing remediation techniques are unable to remove these pollutants, necessitating the development of novel treatment approaches. Due to its unique structure, physicochemical properties, and broad application potential, graphene has attracted a lot of attention as a new type of two-dimensional nanostructure. Given its chemical stability, large surface area, electron mobility, superior thermal conductivity, and two-dimensional structure, tremendous research has been conducted on graphene and its derived composites for environmental remediation and pollution mitigation. Various methods for graphene functionalization have facilitated the development of different graphene derivatives such as graphene oxide (GO), functional reduced graphene oxide (frGO), and reduced graphene oxide (rGO) with novel attributes for multiple applications. This review provides a comprehensive read on the recent progress of multifunctional graphene-based nanocomposites and nanohybrids as a promising way of removing emerging contaminants from aqueous environments. First, a succinct overview of the fundamental structure, fabrication techniques, and features of graphene-based composites is presented. Following that, graphene and GO functionalization, i.e., covalent bonding, non-covalent, and elemental doping, are discussed. Finally, the environmental potentials of a plethora of graphene-based hybrid nanocomposites for the abatement of organic and inorganic contaminants are thoroughly covered.

Biomimetically Inspired Highly Homogeneous Hydrophilization of Graphene with Poly(l-DOPA): Toward Electroconductive Coatings from Water-Processable Paints

Water-based processing of graphene-typically considered as physicochemically incompatible with water in the macroscale-emerges as the key challenge among the central postulates of green nanotechnology. These problematic concerns are derived from the complex nature of graphene in the family of sp2-carbon nanoallotropes. Indeed, nanomaterials hidden under the common "graphene" signboard are very rich in morphological and physicochemical variants. In this work, inspired by the adhesion chemistry of mussel biomaterials, we have synthesized novel, water-processable graphene-polylevodopa (PDOPA) hybrids. Graphene and PDOPA were covalently amalgamated via the "growth-from" polymerization of l-DOPA (l-3,4-dihydroxyphenylalanine) monomer in air, yielding homogeneously PDOPA-coated (23 wt %) (of thickness 10-20 nm) hydrophilic flakes. The hybrids formed >1 year stable and water-processable aqueous dispersions and further conveniently processable paints of viscosity 0.4 Pa·s at 20 s-1 and a low yield stress τ0 up to 0.12 Pa, hence exhibiting long shelf-life stability and lacking sagging after application. Demonstrating their applicability, we have found them as surfactant-like nanoparticles stabilizing the larger, pristine graphene agglomerates in water in the optimized graphene/graphene-PDOPA weight ratio of 9:1. These characteristics enabled the manufacture of conveniently paintable coatings of low surface resistivity of 1.9 kΩ sq-1 (0.21 Ω·m) which, in turn, emerge as potentially applicable in textronics, radar-absorbing materials, or electromagnetic interference shielding.

The Synergistic Properties and Gas Sensing Performance of Functionalized Graphene-Based Sensors

The detection of toxic gases has long been a priority in industrial manufacturing, environmental monitoring, medical diagnosis, and national defense. The importance of gas sensing is not only of high benefit to such industries but also to the daily lives of people. Graphene-based gas sensors have elicited a lot of interest recently, due to the excellent physical properties of graphene and its derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO). Graphene oxide and rGO have been shown to offer large surface areas that extend their active sites for adsorbing gas molecules, thereby improving the sensitivity of the sensor. There are several literature reports on the promising functionalization of GO and rGO surfaces with metal oxide, for enhanced performance with regard to selectivity and sensitivity in gas sensing. These synthetic and functionalization methods provide the ideal combination/s required for enhanced gas sensors. In this review, the functionalization of graphene, synthesis of heterostructured nanohybrids, and the assessment of their collaborative performance towards gas-sensing applications are discussed.

Two-dimensional materials towards separator functionalization in advanced Li-S batteries

Functional separators have played important roles in improving the electrochemical performance of lithium-sulfur (Li-S) batteries by addressing the key issues of both the sulfur cathode and lithium anode. Compared with other materials that are used for separator functionalization, two-dimensional (2D) materials with atomic layer thickness and infinite lateral dimensions feature several advantages of ultra-thin laminate structure, remarkable physical properties and tunable surface chemistry, which show potential applications in separator functionalization towards addressing the issues of both the shuttle effect and formation of Li dendrites in Li-S batteries. In this review, the unique advantages of 2D materials for separator functionalization in Li-S batteries and their common construction methods are introduced. Then, recent progress and advances in the construction of 2D materials functional separators are summarized in detail towards inhibiting the shuttle effect of polysulfides and suppressing Li dendrite growth in Li-S batteries. Finally, some opportunities and challenges of 2D materials for constructing high-performance functional separators are proposed. We anticipate that this review will provide new insights into separator functionalization for developing advanced Li-S batteries.

Graphene and Graphene Oxide as a Support for Biomolecules in the Development of Biosensors

Graphene and graphene oxide have become the base of many advanced biosensors due to their exceptional characteristics. However, lack of some properties, such as inertness of graphene in organic solutions and non-electrical conductivity of graphene oxide, are their drawbacks in sensing applications. To compensate for these shortcomings, various methods of modifications have been developed to provide the appropriate properties required for biosensing. Efficient modification of graphene and graphene oxide facilitates the interaction of biomolecules with their surface, and the ultimate bioconjugate can be employed as the main sensing part of the biosensors. Graphene nanomaterials as transducers increase the signal response in various sensing applications. Their large surface area and perfect biocompatibility with lots of biomolecules provide the prerequisite of a stable biosensor, which is the immobilization of bioreceptor on transducer. Biosensor development has paramount importance in the field of environmental monitoring, security, defense, food safety standards, clinical sector, marine sector, biomedicine, and drug discovery. Biosensor applications are also prevalent in the plant biology sector to find the missing links required in the metabolic process. In this review, the importance of oxygen functional groups in functionalizing the graphene and graphene oxide and different types of functionalization will be explained. Moreover, immobilization of biomolecules (such as protein, peptide, DNA, aptamer) on graphene and graphene oxide and at the end, the application of these biomaterials in biosensors with different transducing mechanisms will be discussed.

Adsorptive removal of antibiotic ofloxacin in aqueous phase using rGO-MoS2 heterostructure

This paper reports the synthesis, characterization and detailed adsorption studies of rGO-MoS₂ heterostructure. The heterostructure was explored for the adsorption of ofloxacin from the aqueous phase. Detailed studies were conducted to study the effect of crucial parameters such as pH of drug solution, adsorbent dose, temperature and initial drug concentration on the adsorption capacity. Even with a low surface area of 17.17 m²/g, the adsorbent exhibited maximum removal efficiency of 95% at a dose of 0.35 g/L and an initial drug concentration of 10 mg/L in 240 min. Thermodynamic study revealed the values for ∆H⁰ and ∆G⁰ to be - 101.15 and - 7.47 kJ/mol respectively, indicating that the process is spontaneous and exothermic in nature. The heterostructure adsorbent exhibited remarkable reusability and stability up to five cycles. The heterostructure combines excellent adsorption capabilities arising from the two-dimensional structures of rGO and MoS₂ with the stronger and more specific interaction with the drug molecules which results in better performance towards the removal of the drug. The excellent performance of the heterostructure indicates that combining 2D materials can be a good strategy for producing highly efficient materials towards the adsorptive removal of pollutants.

Comparative studies on the adsorption of various radioactive nuclides from waste aqueous solutions on graphene oxide, inorganic and organic ion exchangers

Adsorption of the radionuclides 141Ce, 140La, 140Ba, 137+134Cs, 131I, 125Sb, 103Ru, 95Nb and 95Zr are studied on graphene oxide from waste aqueous solution samples and their adsorption behaviors are compared to that on the inorganic ion exchanger Ceric tungstate as well as on the strong acidic cation exchanger Dowex-50X8 H+ form, the chelating resin Chelex-100 Na+ form and the strong basic anion exchanger AG-1X8 Cl− form. The waste samples are dilute aqueous solutions resulting from previous work. These solutions contained neither oxidizing nor reducing agents, consequently, it is expected that these radionuclides are existing in their most stable oxidation states, i.e. Ce(III), La(III), Ba(II), Cs(I), Ru(III) & (IV), Sb(III) & (V), Nb(V) and Zr(IV). The adsorption is studied under static conditions for all these radioactive nuclides in the presence of each other. Gamma radiometric analysis is carried out for these radionuclides. Effect of some factors on the adsorption is studied such as pH, graphene oxide particle sizes, contact time, temperature and other parameters. Complete removal of some radionuclides is achieved from these waste solutions by adsorption on graphene oxide. Some separation alternatives for some of these radionuclides are also achieved.

An ecologically friendly process for graphene exfoliation based on the "hydrodynamic cavitation on a chip" concept

Tremendous research efforts have recently focused on the synthesis of graphene from graphitic materials, while environmental issues, scalability, and cost are some of the major challenges to be surmounted. Liquid phase exfoliation (LPE) of graphene is one of the principal methods for this synthesis. Nevertheless, sufficient information about the mechanisms of exfoliation has yet to emerge. Here, a microreactor based on the hydrodynamic cavitation (HC) on a chip concept is introduced to exfoliate graphite in a totally green process which involves only natural graphite flakes and water. HC-treated graphitic materials were characterized by UV-Vis and Raman spectroscopy, DLS (Dynamic Light Scattering), AFM (Atomic Force Microscopy), and SEM (Scanning Electron Microscopy) analyses. The present sustainable reactor system was found to exfoliate thick and large graphite particles to nano-sized sheets (∼1.2 nm) with a lateral size of ∼500 nm to 5 μm.

LPE of graphene with a hydrodynamic cavitation microreactor is a totally green process which involves only natural graphite flakes and water.

Moderating cellular inflammation using 2-dimensional titanium carbide MXene and graphene variants

The effective control of microbial and metabolically derived biological toxins which negatively impact physical health remains a key challenge for the 21st century. 2-Dimensional graphene and MXene nanomaterials are relatively new additions to the field of biomedical materials with superior external surface areas suited to adsorptive remediation of biological toxins. However, relatively little is known about their physiological interactions with biological systems and, to date, no comparative biological studies have been done. This study compares titanium carbide MXene (Ti3C2Tx) in multilayered and delaminated forms with graphene variants to assess the impact of variable physical properties on cellular inflammatory response to endotoxin stimulus. No significant impact on cell metabolism or induction of inflammatory pathways leading to cell death was observed. No significant increase in markers of blood cell activation and haemolysis occurred. Whilst graphene nanoplatelets (GNP), graphene oxide (GO) and Ti3C2Tx showed insignificant antibacterial activity towards Escherichia coli, silver nanoparticle-modified GO (GO-Ag) induced bacterial cell death and at a lower dose than silver nanoparticles. All nanomaterials significantly reduced bacterial endotoxin induced THP-1 monocyte IL-8, IL-6 and TNF-α cytokine production by >99%, >99% and >80% respectively, compared to control groups. This study suggests the utility of these nanomaterials as adsorbents in blood contacting medical device applications for removal of inflammatory cytokines linked to poor outcome in patients with life-threatening infection.

Recent advances in graphene monolayers growth and their biological applications: A review

Development of two-dimensional high-quality graphene monolayers has recently received great concern owing to their enormous applications in diverging fields including electronics, photonics, composite materials, paints and coatings, energy harvesting and storage, sensors and metrology, and biotechnology. As a result, various groups have successfully developed graphene layers on different substrates by using the chemical vapor deposition method and explored their physical properties. In this direction, we have focused on the state-of-the-art developments in the growth of graphene layers, and their functional applications in biotechnology. The review starts with the introduction, which contains outlines about the graphene and their basic characteristics. A brief history and inherent applications of graphene layers followed by recent developments in growth and properties are described. Then, the application of graphene layers in biodevices is reviewed. Finally, the review is summarized with perspectives and future challenges along with the scope for future technological applications.

Antimicrobial Mechanisms and Effectiveness of Graphene and Graphene-Functionalized Biomaterials. A Scope Review

Bacterial infections represent nowadays the major reason of biomaterials implant failure, however, most of the available implantable materials do not hold antimicrobial properties, thus requiring antibiotic therapy once the infection occurs. The fast raising of antibiotic-resistant pathogens is making this approach as not more effective, leading to the only solution of device removal and causing devastating consequences for patients. Accordingly, there is a large research about alternative strategies based on the employment of materials holding intrinsic antibacterial properties in order to prevent infections. Between these new strategies, new technologies involving the use of carbon-based materials such as carbon nanotubes, fullerene, graphene and diamond-like carbon shown very promising results. In particular, graphene- and graphene-derived materials (GMs) demonstrated a broad range antibacterial activity toward bacteria, fungi and viruses. These antibacterial activities are attributed mainly to the direct physicochemical interaction between GMs and bacteria that cause a deadly deterioration of cellular components, principally proteins, lipids, and nucleic acids. In fact, GMs hold a high affinity to the membrane proteoglycans where they accumulate leading to membrane damages; similarly, after internalization they can interact with bacteria RNA/DNA hydrogen groups interrupting the replicative stage. Moreover, GMs can indirectly determine bacterial death by activating the inflammatory cascade due to active species generation after entering in the physiological environment. On the opposite, despite these bacteria-targeted activities, GMs have been successfully employed as pro-regenerative materials to favor tissue healing for different tissue engineering purposes. Taken into account these GMs biological properties, this review aims at explaining the antibacterial mechanisms underlying graphene as a promising material applicable in biomedical devices.

Functionalized Carbon Nanostructures Versus Drug Resistance: Promising Scenarios in Cancer Treatment

Carbon nanostructures (CN) are emerging valuable materials for the assembly of highly engineered multifunctional nanovehicles for cancer therapy, in particular for counteracting the insurgence of multi-drug resistance (MDR). In this regard, carbon nanotubes (CNT), graphene oxide (GO), and fullerenes (F) have been proposed as promising materials due to their superior physical, chemical, and biological features. The possibility to easily modify their surface, conferring tailored properties, allows different CN derivatives to be synthesized. Although many studies have explored this topic, a comprehensive review evaluating the beneficial use of functionalized CNT vs G or F is still missing. Within this paper, the most relevant examples of CN-based nanosystems proposed for MDR reversal are reviewed, taking into consideration the functionalization routes, as well as the biological mechanisms involved and the possible toxicity concerns. The main aim is to understand which functional CN represents the most promising strategy to be further investigated for overcoming MDR in cancer.

Progress in the functional modification of graphene/graphene oxide: a review

Graphene and graphene oxide have attracted tremendous interest over the past decade due to their unique and excellent electronic, optical, mechanical, and chemical properties. This review focuses on the functional modification of graphene and graphene oxide. First, the basic structure, preparation methods and properties of graphene and graphene oxide are briefly described. Subsequently, the methods for the reduction of graphene oxide are introduced. Next, the functionalization of graphene and graphene oxide is mainly divided into covalent binding modification, non-covalent binding modification and elemental doping. Then, the properties and application prospects of the modified products are summarized. Finally, the current challenges and future research directions are presented in terms of surface functional modification for graphene and graphene oxide.

Graphene and graphene oxide have attracted tremendous interest over the past decade due to their unique and excellent electronic, optical, mechanical, and chemical properties.

Cycloaddition of Nitrile Oxides to Graphene: a Theoretical and Experimental Approach

Density functional theory (DFT) studies of the interaction between graphene sheets and nitrile oxides have proved the feasibility of the reaction through 1,3-dipolar cycloaddition. The viability of the approach has been also confirmed experimentally through the cycloaddition of few-layer exfoliated graphene and nitrile oxides containing functional organic groups with different electronic nature. The cycloaddition reaction has been successfully achieved in one-pot from the corresponding oximes under microwave (MW) irradiation. The successful formation of the isoxazoline ring has been confirmed by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS).

A novel one-pot facile economic approach for the mass synthesis of exfoliated multilayered nitrogen-doped graphene-like nanosheets: new insights into the mechanistic study

The present research focuses on providing a novel facile, cost-effective and eco-friendly method for the mass production of N-doped graphene-like nanosheets (NGLs), in order to industrially benefit the exploitation of N-doped graphene in electronics, which will lead to the remarkable prosperity of graphene-based nanoelectronics. NGLs have been synthesized through a one-pot single-step process involving hydrolysis/hydrothermal treatment of glucose under mild conditions, using cetyltrimethylammonium bromide (CTAB) and ammonia solution (NH₄OH) as the structure-directing agents. NGLs of high yield (65 wt%) and fascinating structural features, including low oxidation level, good crystalline structural order, and large laterally sized and well-exfoliated nanosheets, have been produced. The growth mechanism has been deeply investigated. The impressive chemical nature of CTAB has a synergistic effect in controlling the NGL structure. The cationic head of CTAB and anionic OH^- ions resulting from NH₄OH ionization have formed a passivating layer that played a profound role in hindering the NGL agglomeration and allowing the NGLs to grow into large lateral dimensions. Meanwhile, the polar (mainly H-bonding) and apolar (hydrophobic) interfacial interactions between the passivating layer and the graphitic network can be mainly considered responsible for the mild disturbed structural order inside the sp² crystals. On the other hand, the excessive decomposition of CTAB that is also accompanied by fair ammonia decomposition during the hydrothermal treatment resulted in plenty of hydrogen and nitrogen gases in the atmosphere. The nitrogen gas N-doped the graphitic structure and the hydrogen gas effectively deoxygenated it. Furthermore, the high evolution rate of gases throughout the synthesis system contributed to the obstruction of NGL agglomeration. These results emphasize the high yield and good quality of the synthesized NGLs, which makes such a strategy promising in trust acquisition for investors in industrial production of N-doped graphene.

Qualitative and Quantitative Analysis of Graphene-Based Adsorbents in Wastewater Treatment

Nowadays water bodies across the world are heavily polluted due to uncontrollable contamination of heavy metal particles, toxic dyes, and other harmful wastes discharged by emerging industries other than normal domestic wastages. This contamination needs sufficient control to protect the natural water bodies. There are various methodologies to be followed to perform wastewater treatment, in which the adsorption method of filtration is found to be efficient. The adsorption method is a high priority and preferable filtration method compared to other waste water treatment methods due to its peculiar characteristics. Considering the adsorption method, there are multiple options available in selecting material and methodology for the filtration process. In selecting the filtering material, there is much attraction towards graphene and its oxides, which have widespread range of differential applications in commercial industries because of their eco-friendly characteristic features. The importance of various graphene composites and their chemical properties is found to be significant in various fields. Analyzing the adsorbing properties of graphene widely, this article deeply reviews about the improvements and the technologies identified for using graphene and (GO) graphene oxide in wastewater treatment taken into discussion elaborately. Therefore, in this hard review, the advantages and demerits of using graphene for wastewater treatment as well as improving its properties to make it more suitable for wastewater treatment are detailed.

Precise control of the interlayer spacing between graphene sheets by hydrated cations

Based on DFT computations, we show that different hydrated cations can precisely control the interlayer spacings between graphene sheets, which are smaller than that between graphene oxide sheets, indicating an ion sieving.

Graphene-based drug delivery systems in tissue engineering and nanomedicine

The time and dosage form of graphene derivatives have been found to determine therapeutic and toxic windows in several cell lines and preclinical models. The enhanced biological action of graphene derivatives is made possible by altering the chemistry of native materials via surface conjugation, or by changing the oxidation state. The high level of chemical reactivity vested in the planar structure of graphene can be used to load various drugs and biomolecules with maximum radical scavenging effect. The integration of graphene and polymers brings electrical conductivity to scaffolds, making them ideal for cardiac or neuronal tissue engineering. Drawbacks associated with graphene-based materials for biomedical applications include defect-free graphene formation and heteroatom contamination during synthesis process; reduced availability of sp² hybridized carbon centers due to serum proteins masking; and poor availability of data pertaining to in vivo clearance of graphene-based formulations. Personalized medicine is an emerging area of alternative treatments, which in combination with graphene-based nanobiomaterials, has revolutionary potential for the development of individualized nanocarriers to treat highly challenging diseases.

Inducing regioselective chemical reactivity in graphene with alkali metal intercalation

First principles calculations demonstrate that alkali metal atoms, intercalated between metal substrates and adsorbed graphene monolayers, induce localised regions of increased reactivity. The extent of this localisation is proportional to the size of the alkali atom and the strength of the graphene-substrate interaction. Thus, larger alkali atoms are more effective (e.g. K > Na > Li), as are stronger-interacting substrates (e.g. Ni > Cu). Despite the electropositivity of these alkali metal adsorbates, analysis of charge transfer between the alkali metal, the substrate and the adsorbed graphene layer indicates that charge transfer does not give rise to the observed regioselective reactivity. Instead, the increased reactivity induced in the graphene structure is shown to arise from the geometrical distortion of the graphene layer imposed by the intercalated adsorbed atom. We show that this strategy can be used with arbitrary adsorbates and substrate defects, provided such structures are stable, towards controlling the mesoscale patterning and chemical functionalisation of graphene structures.

Eco-friendly preparation of large-sized graphene via short-circuit discharge of lithium primary battery

We proposed a large-sized graphene preparation method by short-circuit discharge of the lithium-graphite primary battery for the first time. LiC_x is obtained through lithium ions intercalation into graphite cathode in the above primary battery. Graphene was acquired by chemical reaction between LiC_x and stripper agents with dispersion under sonication conditions. The gained graphene is characterized by Raman spectrum, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Atomic force microscope (AFM) and Scanning electron microscopy (SEM). The results indicate that the as-prepared graphene has a large size and few defects, and it is monolayer or less than three layers. The quality of graphene is significant improved compared to the reported electrochemical methods. The yield of graphene can reach 8.76% when the ratio of the H₂O and NMP is 3:7. This method provides a potential solution for the recycling of waste lithium ion batteries.

Reduction of Graphene Oxide Thin Films by Cobaltocene and Decamethylcobaltocene

Reduced graphene oxide (RGO) films have been prepared by immersion of graphene oxide (GO) films at room temperature in nonaqueous solutions containing simple, outer-sphere metallocene reductants. Specifically, solutions of cobaltocene, cobaltocene and trifluoroacetic acid (TFA), and decamethylcobaltocene each showed activity for the rapid reduction of GO films cast on a wide variety of substrates. Each reactant increased the conductivity of the films by several orders of magnitude, with RGO films prepared with either decamethylcobaltocene or cobaltocene and TFA possessing the highest conductivities (∼10⁴ S m^-1). X-ray photoelectron spectroscopy suggested that while all three reagents lowered the content of carbon-oxygen functionalities, solutions of cobaltocene and TFA were the most effective at reducing the material to sp² carbon. Separately, Raman spectra and atomic force micrographs indicated that RGO films prepared with decamethylcobaltocene consisted of the largest graphitic domains and lowest macroscopic roughness. Cumulatively, the data suggest that the outer-sphere reductants can affect the conversion to RGO but the reactivity and mechanism depend on the standard potential of the reductant and the availability of protons. This work both demonstrates a new way to prepare high-quality RGO films on a wide range of substrate materials without annealing and motivates future work to elucidate the chemistry of RGO synthesis through the tunability of outer-sphere reductants such as metallocenes.

Synthesis of novel cyclodextrin-modified reduced graphene oxide composites by a simple hydrothermal method

Cyclodextrin (β-CD)-functionalized reduced graphene oxide was successfully synthesized by a simple hydrothermal method, followed by conjugating with polyethylene glycol (PEG) and folic acid (FA). Microscopic and spectroscopic techniques were used to characterize the nanocomposites. Photothermal experiments showed that β-CD-functionalized reduced graphene oxide exhibited higher photothermal conversion efficiency in the near infrared region than reduced graphene oxide functionalized with other molecules under the same conditions. Cytotoxicity experiments indicated that rGO@CD@PEG@FA possessed good biocompatibility even at high concentration. When doxorubicin (DOX) was loaded on the rGO@CD@PEG@FA nanocomposite, it showed the stimulative effect of heat, pH response, and sustained drug release. Cytotoxicity experiments also confirmed the targeted effect and high efficiency of the combined therapy. The findings of the present study provide an ideal drug delivery system for malignant cancer therapy due to the advanced synergistic chemo-photothermal targeted therapy and good drug release properties.

The rGO@CD@PEG@FA nanocomposite showed the stimulative effect of heat, pH response, and sustained drug release for cancer therapy

Heptamethine Cyanine Dyes in the Design of Photoactive Carbon Nanomaterials

Near-infrared (NIR) absorbing nanomaterials, built from anionic heptamethine cyanine dyes and single-walled carbon nanotubes or few-layer graphene, are presented. The covalent linkage, using 1,3-dipolar cycloaddition reactions, results in nanoconjugates that synchronize the properties of both materials, as demonstrated by an in-depth characterization study carried out by transmission electron microscopy, atomic force microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. UV-vis-NIR and Raman spectroscopies further confirmed the unique electronic structure of the novel photoactive nanomaterials.

Controlled Chemical Synthesis in CVD Graphene

Due to the unique properties of graphene, single layer, bilayer or even few layer graphene peeled off from bulk graphite cannot meet the need of practical applications. Large size graphene with quality comparable to mechanically exfoliated graphene has been synthesized by chemical vapor deposition (CVD). The main development and the key issues in controllable chemical vapor deposition of graphene has been briefly discussed in this chapter. Various strategies for graphene layer number and stacking control, large size single crystal graphene domains on copper, graphene direct growth on dielectric substrates, and doping of graphene have been demonstrated. The methods summarized here will provide guidance on how to synthesize other two-dimensional materials beyond graphene.

Nanofluidics in two-dimensional layered materials: inspirations from nature

This review highlights the recent progress, current challenges, and future perspectives in the design and application of 2D layered materials for nanofluidic research, with emphasis on the thought of bio-inspiration.

Catalytic reduction of 4-nitrophenol over Ni-Pd nanodimers supported on nitrogen-doped reduced graphene oxide

Catalytic reduction of toxic 4-nitrophenol to 4-aminophenol over magnetically recoverable nanocatalysts has attracted much attention. Herein, we report a Ni-Pd/NrGO catalyst through the growth of Ni-Pd nanodimers (NDs) on nitrogen-doped reduced graphene oxide (NrGO). The Ni-Pd NDs show a heterogeneous nanostructure with Ni and Pd subparts contacting with each other, remarkably different from the frequently-observed core/shell nanoparticles (NPs) or nanoalloy. The formation of Ni-Pd NDs follows an initial deposition of Pd NPs on the graphene and in-situ catalytic generation of Ni subparts over the newly-generated Pd NPs. The resulting Ni-Pd/NrGO exhibits a superior catalytic activity towards the reduction of 4-nitrophenol at room temperature with a high rate constant (3400s^-1g^-1) and a low activated energy (29.1kJmol^-1) as compared to unsupported Ni-Pd NDs and supported monometallic catalysts. The conversion rate of 4-NP is calculated to be 99.5% and the percent yield (%) of 4-AP is as high as 99.1%. A synergistic catalysis mechanism is rationally proposed, which is ascribed to the electronic modification of Ni-Pd metals due to the strong metal/support interaction (SMSI) effect as well as the electron transfer between Ni and Pd. The hybrid catalyst shows soft ferromagnetic properties and can be magnetically separated and recycled without obvious loss of activity.

Adsorption of poly(ethylene succinate) chain onto graphene nanosheets: A molecular simulation

Understanding the interaction between single polymer chain and graphene nanosheets at local and global length scales is essential for it underlies the mesoscopic properties of polymer nanocomposites. A computational attempt was then performed using atomistic molecular dynamics simulation to gain physical insights into behavior of a model aliphatic polyester, poly(ethylene succinate), single chain near graphene nanosheets, where the effects of the polymer chain length, graphene functionalization, and temperature on conformational properties of the polymer were studied comparatively. Graphene functionalization was carried out through extending the parameters set of an all-atom force field. The results showed a significant conformational transition of the polymer chain from three-dimensional statistical coil, in initial state, to two-dimensional fold, in final state, during adsorption on graphene. The conformational order, overall shape, end-to-end separation statistics, and mobility of the polymer chain were found to be influenced by the graphene functionalization, temperature, and polymer chain length. Furthermore, the polymer chain dynamics mode during adsorption on graphene was observed to transit from normal diffusive to slow subdiffusive mode. The findings from this computational study could shed light on the physics of the early stages of aliphatic polyester chain organization induced by graphene.

Nitrogen-Doped Holey Graphene Film-Based Ultrafast Electrochemical Capacitors

The commercialized aluminum electrolytic capacitors (AECs) currently used for alternating current (AC) line-filtering are usually the largest components in the electronic circuits because of their low specific capacitances and bulky sizes. Herein, nitrogen-doped holey graphene (NHG) films were prepared by thermal annealing the composite films of polyvinylpyrrolidone (PVP), graphene oxide (GO), and ferric oxide (Fe2O3) nanorods followed by chemical etching with hydrochloride acid. The typical electrochemical capacitor with NHG electrodes exhibited high areal and volumetric specific capacitances of 478 μF cm(-2) and 1.2 F cm(-3) at 120 Hz, ultrafast frequency response with a phase angle of -81.2° and a resistor-capacitor time constant of 203 μs at 120 Hz, as well as excellent cycling stability. Thus, it is promising to replace conventional AEC for AC line-filtering in miniaturized electronics.