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Graphene-related two-dimensional materials available on the global market are manufactured using various production methods, with significant variations in properties and qualities causing serious concerns for the emerging multi-billion graphene industry. To address the limitations of conventional characterization methods probing the properties of individual graphene particles which may overlook the presence of non-graphene carbon impurities at a large (bulk) scale, this paper presents the refining thermogravimetric analysis as a complementary method for the reliable chemical characterization and quality control of graphene powders. A systematic parametric investigation of key experimental conditions such as sample mass and loading, heating rate, and gas environment and flow rate is performed to identify optimized settings for reliable thermal gravimetric measurements. These optimized conditions are evaluated through a series of comparative characterizations using industrially produced graphene, graphene oxide, and reduced graphene oxide powders, including their common carbon impurities. The ability of this method to provide both qualitative and quantitative analyses for characterizing graphene-related materials is confirmed. The optimized method is finally validated through an International Laboratory Comparison study and subsequently incorporated into a new standard. This low-cost, industry-affordable, and complementary characterization method is expected to enhance the quality control of manufactured graphene materials and make a valuable contribution to the growing graphene industry. [ABSTRACT FROM AUTHOR]

Curcumin (Cur) is an acidic polyphenol with some effects on α‐glucosidase (α‐Glu), but Cur has disadvantages such as being a weak target, lacking passing the blood–brain barrier and having low bioavailability. To enhance the curative effect of Cur, the hybrid composed of ZnO nanoparticles decorated on rGO was used to load Cur (ZnO@rGO‐Cur). The use of the multispectral method and enzyme inhibition kinetics analysis certify the inhibitory effect and interaction mechanism of ZnO@rGO‐Cur with α‐Glu. The static quenching of α‐Glu with both Cur and ZnO@rGO‐Cur is primarily driven by hydrogen bond and van der Waals interactions. The conformation‐changing ability by binding to the neighbouring phenolic hydroxyl group of Cur increased their ability to alter the secondary structure of α‐Glu, resulting in the inhibition of enzyme activity. The inhibition constant (Ki, Cur > Kis,ZnO@rGO‐Cur) showed that the inhibition effect of ZnO@rGO‐Cur on α‐Glu was larger than that of Cur. The CCK‐8 experiments proved that ZnO@rGO nanocomposites have good biocompatibility. These results suggest that the therapeutic potential of ZnO@rGO‐Cur composite is an emerging nanocarrier platform for drug delivery systems for the potential treatment of diabetes mellitus. [ABSTRACT FROM AUTHOR]

The research community has witnessed an exceptional increase in exploring graphene related two-dimensional materials (GR2Ms) in many innovative applications and emerging technologies. However, simple, low-cost, sustainable, and eco-friendly methods to manufacture large quantities and high-quality GR2Ms still remain an unsolved challenge. To address limitations of conventional wet chemical-based exfoliation methods using graphite resources, the top-down irradiation approach has proven to be an ultrafast, effective, and environmentally friendly technology for scalable exfoliation, production, and processing of GR2Ms providing new properties for emerging applications. Significant advancements have been made for preparation of broad range of GR2Ms from graphite, such as graphene, graphene oxide, and reduced graphene oxide, and their doped, functionalized and modified forms over the past two decades, thanks to the availability of photon and ion irradiation techniques, such as microwave, infrared, ultraviolet, solar, x-ray, gamma, laser, and plasma. This review presents recent advances on the application of these various irradiation techniques and highlights their mechanism, differences in properties of prepared GR2Ms, and their advantages and disadvantages in comparison with other conventional methods. The review provides an insight into the irradiation strategies and their prospective applications to produce, at a large scale, low-cost, high-quality GR2Ms for practical applications in transparent electrodes, optoelectronic devices, sensors, supercapacitors, protective coatings, conductive inks, and composites. [ABSTRACT FROM AUTHOR]

Herein, the visible light‐photocatalytic performance of synthesized ZnO/Gr composite materials with different Gr content under various conditions, i.e., pH, dye concentration, and different scavengers (to understand the photocatalytic activity mechanism) is systematically investigated. Photocatalytic performance is evaluated with the degradation of methylene blue (MB) in solution under sunlight irradiation. The presence of graphene (Gr) in the ZnO/Gr composites shows enhanced photocatalytic activity compared to pure ZnO under natural sunlight illumination. The highest photodegradation efficiency of ≈94% when the content of Gr is 1 wt% in comparison to ≈76% for the pure ZnO, corresponding to reaction rate constants of 0.01038 and 0.00615 min−1, respectively. Compared to recent publications, the degradation efficiency is high with relatively high dye concentration, low catalyst amount, and large solution volume. The enhanced visible light absorption and the reduction of bandgap value are attributed to the enhanced photocatalytic properties of the hybridized composite. Moreover, the investigation of the effect of scavenger substances shows that H2O2 strongly enhanced their photocatalytic ability, suggesting that holes (h+) contribute as the reactive agent in the photodegradation process. [ABSTRACT FROM AUTHOR]

Lead (Pb) is commonly used as a X-ray shielding material but has many limitations because of its heaviness and toxicity; thus, it is imperative to be replaced with lightweight and Pb-free shielding materials. To address this problem, molybdenum disulfide (MoS2)/epoxy (MoS2-EP) composites were considered as a possible solution. However, the low compatibility between MoS2 and an epoxy (EP) matrix and an unideal particle dispersion he lack of their distribution have hindered their designed X-ray shielding performance. To overcome this problem, this paper presented how the combination of graphene (GN) and hexagonal boron nitride (hBN) additives can significantly enhance the X-ray shielding performance of MoS2-EP composites. The results showed that when GN or hBN were introduced into the EP-MoS2 composite, X-ray transmission was reduced to 9.8% at 30 kVp and 40.3% at 80 kVp for EP-MoS2-GN and 7.1% at 30 kVp and 34.3% at 80 kVp for EP-MoS2-hBN. These results were explained due to the high aspect ratio of GN, which improved the MoS2 distribution within the EP matrix in the case of hBN, and the electrostatic forces at the interface of hBN and EP leading to better dispersion and interaction with the EP matrix compared to GN. Moreover, by employing an equal amount of the GN–hBN mixture, the synergistic effect of the EP-MoS2-GN-hBN composite film was observed with a significant X-ray shielding enhancement of 52.1% at 30 kVp and 33.2% at 80 kVp compared to that of the EP-MoS2 composite with the same thickness (2 mm) and density. These results were attributed to the molecular bonding of GN or hBN, which improved the compatibility between MoS2 and the EP matrix, providing other benefits of reduced surface roughness (0.46 μm) and improved composite hardness (65.7 HD). This work highlights a new strategy using combined GN and/or hBN for other high atomic number (Z) compounds–polymer composites and the development of advanced non-Pb X-ray shielding applications. [ABSTRACT FROM AUTHOR]

Neural tissue engineering aims to restore the function of nervous system tissues using biocompatible cell‐seeded scaffolds. Graphene‐based scaffolds combined with stem cells deserve special attention to enhance tissue regeneration in a controlled manner. However, it is believed that minor changes in scaffold biomaterial composition, internal porous structure, and physicochemical properties can impact cellular growth and adhesion. The current work aims to investigate in vitro biological effects of three‐dimensional (3D) graphene oxide (GO)/sodium alginate (GOSA) and reduced GOSA (RGOSA) scaffolds on dental pulp stem cells (DPSCs) in terms of cell viability and cytotoxicity. Herein, the effects of the 3D scaffolds, coating conditions, and serum supplementation on DPSCs functions are explored extensively. Biodegradation analysis revealed that the addition of GO enhanced the degradation rate of composite scaffolds. Compared to the 2D surface, the cell viability of 3D scaffolds was higher (p < 0.0001), highlighting the optimal initial cell adhesion to the scaffold surface and cell migration through pores. Moreover, the cytotoxicity study indicated that the incorporation of graphene supported higher DPSCs viability. It is also shown that when the mean pore size of the scaffold increases, DPSCs activity decreases. In terms of coating conditions, poly‐ l‐lysine was the most robust coating reagent that improved cell‐scaffold adherence and DPSCs metabolism activity. The cytotoxicity of GO‐based scaffolds showed that DPSCs can be seeded in serum‐free media without cytotoxic effects. This is critical for human translation as cellular transplants are typically serum‐free. These findings suggest that proposed 3D GO‐based scaffolds have favorable effects on the biological responses of DPSCs. [ABSTRACT FROM AUTHOR]

Thermogravimetric analysis (TGA) has been recognized as a simple and reliable analytical tool for characterization of industrially manufactured graphene powders. Thermal properties of graphene are dependent on many parameters such as particle size, number of layers, defects and presence of oxygen groups to improve the reliability of this method for quality control of graphene materials, therefore it is important to explore the influence of these parameters. This paper presents a comprehensive TGA study to determine the influence of different particle size of the three key materials including graphene, graphene oxide and graphite on their thermal parameters such as carbon decomposition range and its temperature of maximum mass change rate (Tmax). Results showed that Tmax values derived from the TGA-DTG carbon combustion peaks of these materials increasing from GO (558-616 °C), to graphene (659-713 °C) and followed by graphite (841-949 °C) The Tmax values derived from their respective DTG carbon combustion peaks increased as their particle size increased (28.6-120.2 °m for GO, 7.6-73.4 for graphene and 24.2-148.8 °m for graphite). The linear relationship between the Tmax values and the particle size of graphene and their key impurities (graphite and GO) confirmed in this study endows the use of TGA technique with more confidence to evaluate bulk graphene-related materials (GRMs) at low-cost, rapid, reliable and simple diagnostic tool for improved quality control of industrially manufactured GRMs including detection of "fake" graphene. [ABSTRACT FROM AUTHOR]

The coexistence of multiple toxic water pollutants (heavy metals, organic dyes, oils, and organic solvents) limits the sustainable supply of clean water worldwide and urges the development of advanced water purification technology that can remove these contaminants simultaneously. Since its discovery, graphene‐based materials have gained substantial attention toward development of new‐generation sorbents for water purification. Despite several recently published reviews on water purification technology using graphene and its derivatives, there is still a gap in the review considering multiple water‐pollutant remediation using advanced graphene materials. In this review, in the first instance, a comparative structure–function–performance relationship between graphene‐based sorbents and the multipollutants in water is established. A fundamental correlation is made between the sorption performance for diverse pollutants in water with the more specific adsorption properties (surface area, pore size, type of functional groups, C/O, C/N, and C/S atomic ratio) of advanced graphene sorbents. Second, the underlying interaction mechanisms are uncovered between different classes of water pollutants using single graphene‐based sorbents. Third, the rational design of advanced multipollutant sorbents based on graphene is elaborated. The reality, challenges, and opportunities of advanced graphene materials as emerging sorbents for sustainable water purification technology are finally presented in the last section. [ABSTRACT FROM AUTHOR]

Polluted waters are complex systems with many different co‐existing contaminants that make their simultaneous removal a very challenging task. To address this problem, all‐in‐one ad/ab‐sorbent with unique combination of interfacial properties and multiple surface chemistry is developed to simultaneously and efficiently remove several pollutants including heavy metals, dyes, oils, and organic solvents. By mimicking the wetting micro‐topology of a darkling beetle with a combined hydrophilic‐hydrophobic surface, a new bioinspired adsorbent, graphene biopolymer foam (Alg‐Fe3O4‐rGO‐4S) for removal of multiple water pollutants is engineered by combining alginate (Alg) and reduced graphene oxide (rGO) functionalized with tetrathiol that is also decorated with iron oxide nanoparticles (Fe3O4). This concept is first proved by single pollutant removal, showing adsorption capacity of 789.7 ± 36 mg/g for methylene blue (MB), 107.0 ± 2.1 mg/g for Hg (II), 73.5 ± 0.7 mg/g for Cu (II), and rapid oil‐water separation with high sorption capacity (11–18 g/g). A remarkable performance for simultaneous removal of their mixtures in milli‐Q, river, and sea water is demonstrated with efficiency for MB (≈90%), Cu (II) (>99.99%) and Hg (II) (100%) and rapid (≈30 s) uptake of organic solvents and oils. The obtained results indicate a valuable potential of proposed concept for simultaneous removal of co‐existing water pollutants. [ABSTRACT FROM AUTHOR]

Environmental context: Per- and poly-fluoroalkyl substances (PFASs) are contaminants of emerging concern, creating a need to develop efficient multi-functional adsorbents for improved remediation performance. By exploiting the versatility of graphene technology, we demonstrate that combining mineral and carbonaceous phases greatly increases and strengthens PFAS-binding to the adsorbent. The study highlights the benefits and potential applications of mixed adsorbents in PFAS-remediation. As the degradation of perfluorooctanoic acid (PFOA) and related per- and poly-fluoroalkyl substances (PFASs) is energy-intensive, there is a need to develop in situ remediation strategies to manage PFAS-contamination. The sorption of PFOA by graphene oxide (GO), an iron-oxide-modified reduced-GO composite (FeG) and an activated-carbon(C)/clay/alumina-based adsorbent, RemBindTM (RemB), are evaluated. Sorption by FeG and RemB (>90 %) is much greater than GO (60 %). While an increase in pH hinders PFOA-sorption by GO, owing to the increased repulsion of anionic PFOA, variations in pH and ionic strength do not significantly influence PFOA-sorption by FeG and RemB, which indicates that binding is predominantly controlled by non-electrostatic forces. Hydrophobic interactions are assumed at the graphene or C-surface for all adsorbents, with added ligand-exchange mechanisms involving the associated Fe- and Al-minerals in FeG and RemB, respectively. Desorption of adsorbed PFOA is greatest in methanol, compared to water, toluene, or hexane, which provides estimates of the binding strength and reversibility from an environmental-partitioning perspective; i.e. risk of remobilisation of bound PFOA owing to rainfall events is low, but the presence of polar organic solvents may increase leaching risk. Iron-mineral-functionalisation of GO enhances the amount of PFOA adsorbed (by 30 %) as well as the binding strength, which highlights the advantage of combining mineral and C-phases. Successful sorption of a range of PFASs from a contaminated-site water sample highlights the potential of using 'mixed' adsorbents like FeG and RemB in situ for PFAS-remediation, as they provide avenues for enhanced sorption through multiple mechanisms. Environmental context. Per- and poly-fluoroalkyl substances (PFASs) are contaminants of emerging concern, creating a need to develop efficient multi-functional adsorbents for improved remediation performance. By exploiting the versatility of graphene technology, we demonstrate that combining mineral and carbonaceous phases greatly increases and strengthens PFAS-binding to the adsorbent. The study highlights the benefits and potential applications of mixed adsorbents in PFAS-remediation. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) and arsenate (As) are notorious environmental contaminants, and co‐contamination usually requires opposing treatment strategies due to their differing physico‐chemical properties. Developing adsorbents that can bind both contrasting contaminants simultaneously is desirable. Two prepared graphene materials, graphene oxide (GO) and iron‐oxide‐modified reduced‐GO (FeG), are evaluated for Cd‐ and As‐sorption, and performance is compared to a mixed‐mode commercial adsorbent. Negatively charged GO shows affinity toward cationic Cd, and positively charged FeG shows affinity toward anionic As. Sorption is pH dependent: Increase in pH‐promotes Cd‐sorption and retards As‐sorption. GO displays excellent Cd‐sorption even in acidic conditions. The maximum amounts adsorbed by GO and FeG are 782 μmol Cd g−1 and 408 μmol As g−1, respectively. Competition by calcium strongly suppresses Cd‐sorption, whereas competition by phosphate does not hinder As‐sorption. A mixture of GO and FeG demonstrates successful simultaneous sorption of Cd and As from co‐contaminated solutions, including a natural water sample, displaying greater sorption than the commercial adsorbent. Data highlight the potential application of graphene materials in effective mixed‐mode remediation of multiple contaminants (cations and anions). [ABSTRACT FROM AUTHOR]

Abstract: The unique physical and chemical properties of graphene‐based nanomaterials (GNMs) have inspired a diverse range of scientific and industrial applications. The market value of GNMs is predicted to reach $US 1.3 billion by 2023. Common to many nanomaterials, an important and unresolved question is the environmental consequences of the increases in GNMs use. The current deficiencies in studies reporting ecotoxicology data for GNMs include differences in analytical methodologies for quantification, no standardized test guidelines, differences in morphology of GNMs, the lack of Chemical Abstract Service numbers, and the quality of the reported data. The assessment of potential adverse effects on aquatic organisms typically relies on guideline values based on species sensitivity distributions (SSDs) of toxicity data. We present preliminary water quality guideline values for graphene oxide NMs in freshwaters. Data include 10 species from 7 phyla (bacteria and fungi were not included). The most sensitive organism was found to be the freshwater shrimp Palaemon pandaliformis. The derived guideline values for 99, 95, 90, and 80% species protection were 350, 600, 830, and 1300 μg/L, respectively. These results will contribute to the regulatory derivations of future water quality guideline values for graphene‐based NMs. Environ Toxicol Chem 2018;37:1340–1348. © 2018 SETAC [ABSTRACT FROM AUTHOR]

Development of next-generation sensor devices is gaining tremendous attention in both academia and industry because of their broad applications in manufacturing processes, food and environment control, medicine, disease diagnostics, security and defense, aerospace, and so forth. Current challenges include the development of low-cost, ultrahigh, and user-friendly sensors, which have high selectivity, fast response and recovery times, and small dimensions. The critical demands of these new sensors are typically associated with advanced nanoscale sensing materials. Among them, graphene and its derivatives have demonstrated the ideal properties to overcome these challenges and have merged as one of the most popular sensing platforms for diverse applications. A broad range of graphene assemblies with different architectures, morphologies, and scales (from nano-, micro-, to macrosize) have been explored in recent years for designing new high-performing sensing devices. Herein, this study presents and discusses recent advances in synthesis strategies of assembled graphene-based superstructures of 1D, 2D, and 3D macroscopic shapes in the forms of fibers, thin films, and foams/aerogels. The fabricated state-of-the-art applications of these materials in gas and vapor, biomedical, piezoresistive strain and pressure, heavy metal ion, and temperature sensors are also systematically reviewed and discussed, and their sensing performance is compared. [ABSTRACT FROM AUTHOR]

The early diagnosis of diseases, e.g., Parkinson's and Alzheimer's disease, diabetes, and various types of cancer, and monitoring the response of patients to the therapy plays a critical role in clinical treatment; therefore, there is an intensive research for the determination of many clinical analytes. In order to achieve point-of-care sensing in clinical practice, sensitive, selective, cost-effective, simple, reliable, and rapid analytical methods are required. Biosensors have become essential tools in biomarker sensing, in which electrode material and architecture play critical roles in achieving sensitive and stable detection. Carbon nanomaterials in the form of particle/dots, tube/wires, and sheets have recently become indispensable elements of biosensor platforms due to their excellent mechanical, electronic, and optical properties. This review summarizes developments in this lucrative field by presenting major biosensor types and variability of sensor platforms in biomedical applications. [ABSTRACT FROM AUTHOR]

Abstract: The biomedical applications of graphene-based materials, including drug delivery, have grown rapidly in the past few years. Graphene and graphene oxide have been extensively explored as some of the most promising biomaterials for biomedical applications due to their unique properties: two-dimensional planar structure, large surface area, chemical and mechanical stability, superb conductivity and good biocompatibility. These properties result in promising applications for the design of advanced drug delivery systems and delivery of a broad range of therapeutics. In this review we present an overview of recent advances in this field of research. We briefly describe current methods for the surface modification of graphene-based nanocarriers, their biocompatibility and toxicity, followed by a summary of the most appealing examples demonstrated for the delivery of anti-cancer drugs and genes. Additionally, new drug delivery concepts based on controlling mechanisms, including targeting and stimulation with pH, chemical interactions, thermal, photo- and magnetic induction, are discussed. Finally the review is summarized, with a brief conclusion of future prospects and challenges in this field. [Copyright &y& Elsevier]

Functionalization of pristine graphene to achieve high water dispersibility remains as a key obstacle owing to the high hydrophobicity and absence of reactive functional groups on the graphene surface. Herein, a green and simple modification approach to prepare highly dispersible functionalized graphene via thermal thiol-ene click reaction was successfully demonstrated on pristine graphene. Specific chemical functionalities (–COO, –NH2 and –S) on the thiol precursor (L-cysteine ethyl ester) were clicked directly on the sp2 carbon of graphene framework with grafting density of 1 unit L-cysteine per 113 carbon atoms on graphene. This functionalized graphene was confirmed with high atomic content of S (4.79 at % S) as well as the presence of C–S–C and N–H species on the L-cysteine functionalized graphene (FG-CYS). Raman spectroscopy evidently corroborated the modification of graphene to FG-CYS with an increased intensity ratio of D and G band, ID/IG ratio (0.3 to 0.7), full-width at half-maximum of G band, FWHM [G] (20.3 to 35.5) and FWHM [2D] (64.8 to 90.1). The use of ethanol as the reaction solvent instead of common organic solvents minimizes the chemical hazards exposure to humans and the environment. This direct attachment of multifunctional groups on the surface of pristine graphene is highly demanded for graphene ink formulations, coatings, adsorbents, sensors and supercapacitor applications. [ABSTRACT FROM AUTHOR]

Flexible electronics have gained eminent importance in recent years due to their high mechanical strength and resistance to environmental conditions, along with their effective energy storage and energy generating abilities. In this work, graphene/ceramic/polymer based flexible dielectric nanocomposites have been prepared and their dielectric properties were characterized. The composite was formulated by combining graphene with rutile and anatase titania, and polyvinylidene fluoride in different weight ratios to achieve optimized dielectric properties and flexibility. After preparation, composites were characterized for their morphologies, structures, functional groups, thermal stability and dielectric characterizations by using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis and impedance spectroscopy. Dielectric results showed that prepared flexible composite exhibited dielectric constant of 70.4 with minor leakage current (tanδ) i.e., 0.39 at 100 Hz. These results were further confirmed by calculating alternating current (AC) conductivity and electric modulus which ensured that prepared material is efficient dielectric material which may be employed in electronic industry for development of next generation flexible energy storage devices. [ABSTRACT FROM AUTHOR]

To address the limitations of piezoelectric polymers which have a low dielectric constant andto improve their dielectric and ferroelectric efficiency for energy storage applications, we designed and characterized a new hybrid composite that contains polyvinylidene fluoride as a dielectric polymer matrix combined with graphene platelets as a conductive and barium titanite as ceramic ferroelectric fillers. Different graphene/barium titanate/polyvinylidene fluoride nanocomposite films were synthesized by changing the concentration of graphene and barium titanate to explore the impact of each component and their potential synergetic effect on dielectric and ferroelectric properties of the composite. Results showed that with an increase in the barium titanate fraction, dielectric efficiency ofthe nanocomposite was improved. Among all synthesized nanocomposite films, graphene/barium titanate/polyvinylidene fluoride nanocomposite in the weight ratio of 0.15:0.5:1 exhibited thehighest dielectric constant of 199 at 40 Hz, i.e., 15 fold greater than that of neat polyvinylidene fluoride film at the same frequency, and possessed a low loss tangent of 0.6. However, AC conductivity and ferroelectric properties of graphene/barium titanate/polyvinylidene fluoride nanocomposite films were enhanced with an increase in the graphene weight fraction. Graphene/barium titanate/polyvinylidene fluoride nanocomposite films with a weight ratio of 0.2:0.1:1 possessed a high AC conductivity of 1.2 × 10−4 S/m at 40 Hz. While remanent polarization, coercive field, and loop area of the same sample were 0.9 μC/cm2, 9.78 kV/cm, and 24.5 μC/cm2·V, respectively. Our results showed that a combination of graphene and ferroelectric ceramic additives are an excellent approach to significantly advance the performance of dielectric and ferroelectric properties of piezoelectric polymers for broad applications including energy storage. [ABSTRACT FROM AUTHOR]

One of the most studied photoluminescence emission peaks of anatase titanium dioxide (TiO 2) is green, located at about 520 nm, which is assigned to the radiative recombination between a mobile electron in the conduction band and oxygen vacancy defect as a trapped hole in the bandgap. Composite materials of TiO 2 with graphene are normally shown by the gradual quenching of photoluminescence intensity as a result of carrier lifetime extension, which is important to enhance photocatalytic activity. Herein we report an observation of the intensity enhancement of the green PL emission in a composite TiO 2 nanotube (TNT) and graphene produced through facile hydrothermal synthesis. The heterojunction formation of graphene and TNT makes the excited photoelectrons easy to diffuse from TNT to graphene. Hence, the recombination rate of mobile electrons in graphene and trapped holes located on the nanotube surface is enhanced due to the high mobility of electrons in graphene. • A facial hydrothermal systhesis of titanium dioxide nanotube (TNT) and graphene composite. • The nanohybridization formation between graphene and TNT was revealed by XRD and Raman shift. • The intensity of the green photoluminescence emission at 530 nm was considerably increased in the composite. • The electromigration between graphene and TNT is a reason for the high green emission intensity. [ABSTRACT FROM AUTHOR]

Since the initial emergence of two-dimensional graphene (Gr) nano-material, there has been a great interest in its potential applications due to its excellent conductivity, enormous surface area and good mechanical strength. Microbial fuel cells (MFCs) are one of these important promising applications. The limited productivity of MFCs compared to other fuel cell technologies along with the high cost of their components are the two major obstacles to commercialization. Gr is proposed to help overcome such challenges by integrating with biocatalysts for the construction of Gr based MFCs, either as an anode to increase the electron transfer efficiency, or as a cathode to effectively catalyze the oxygen reduction reaction (ORR). This integration is relevant only if the favorable environment for bacterial biofilm adherence to Gr modified surfaces is available. Unfortunately, there is insufficient understanding of the interaction mechanism of bacterial cells with such modified surfaces. Despite this challenge, along with the complexity of the Gr modified electrode fabrication, Gr-based electrodes remain a promising option for developing MFCs to achieve sustainable wastewater treatment and bioelectricity generation. As a reflection on these facts, the aim of this review is to provide critical overview and to evaluate the recent advances for the applications of Gr in MFCs, focusing on electrode fabrication and power generation. Within that context, the concerns about microbial compatibility of Gr will be addressed. [ABSTRACT FROM AUTHOR]

Point-of-care (POC) diagnostic technologies for early stage diagnosis and real-time monitoring of medical conditions are important element of healthcare strategy to improve medical treatment outcomes. Graphene, one-atom-thick fabric of carbon, has attracted enormous attention as a new sensing platform for the development of a new generation of nanoscale sensing devices. The two-dimensional (2D) nanostructure and high surface-to-volume ratio of graphene provide a strategy for designing sensing devices with capability to detect diverse analyte molecules. Their excellent conductivity and zero-band gap features promote electron transport between the sensor and analyte molecules, which is crucial for the development of ultra-fast-responsive and high sensitive devices for numerous biomedical applications. Particularly, owing to ease of fabrication and miniaturization, low cost, and simplicity of operation, graphene-based sensors offer a great potential for portable real-time medical diagnostics, when compared with conventional techniques based on expensive and labor extensive lab-bench instruments. This review provides a brief overview of recent progress in graphene-based sensors for the detection of volatile organic compounds (VOCs) and diagnosis of diseases via non-invasive analysis. Techniques for the fabrication of sensors and critical analysis of VOCs detection devices associated with various diseases are presented. We also summarized approaches to overcome the remaining obstacles in real-world applications of sensors in clinical diagnosis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Kinetics of CO 2 adsorption was explored on three graphene materials. • Avrami's model best describes CO 2 adsorption kinetics of graphene materials. • Activation parameters of CO 2 adsorption on graphene materials were investigated. • Rate-limiting kinetics were explored to determine their mass transfer mechanisms. • CO 2 adsorption rate is governed by film diffusion and intraparticle diffusion. Graphene related two dimensional materials (GR2Ms) are promising adsorbents for CO 2 capture. However, the CO 2 adsorption kinetics and mechanisms on these materials remain insufficiently explored and understudied. Recognizing the pivotal role of adsorption kinetics in assessing the practical applicability, this study comprehensively evaluates the CO 2 adsorption kinetics, underlying mechanisms, and thermodynamic properties via gravimetric analysis on three distinct well-characterized graphene materials (few layer graphene-FLG, graphene oxide-GO, reduced graphene oxide-rGO) across temperatures from 25 to 75 °C under atmospheric pressure. Results reveal that Avrami's fractional model offers the most accurate fit for CO 2 adsorption kinetics among the three examined models (pseudo-first, pseudo-second, and Avrami's fractional order). The interplay between the physico-structural-chemical properties of GR2Ms and the CO 2 adsorption kinetics discloses that the morphology, crystallite size, specific surface area and porosity of GR2Ms greatly influence the CO 2 adsorption rate as evidenced by the largest rate constant, k A value of rGO at 25 to 75 °C under atmospheric pressure. Analysis of activation parameters including activation energy, enthalpy of activation, entropy of activation, and free energy of activation derived from Eyring, Arrhenius, and Gibbs equations indicates a greater favorability of CO 2 adsorption on GR2Ms at lower temperatures. Moreover, investigation into the underlying interaction mechanisms between CO 2 molecules and GR2Ms, using rate-limiting kinetic models (Boyd's film diffusion model, interparticle diffusion model, and intraparticle diffusion model), confirms that both film diffusion resistance and intraparticle diffusion resistance predominantly govern the CO 2 adsorption rate. [ABSTRACT FROM AUTHOR]

The absence of rapid, reliable and cost-effective quality control for industrially manufactured graphene materials is an immediate problem for the emerging graphene industry. Recent studies have alarmingly revealed that a large percentage of manufactured graphene materials traded worldwide have a large variation of properties, and some of them are overpriced graphite powders. Currently, benchmark graphene characterization methods based on localized analysis can provide information of key properties of graphene such as the number of layers, particle size, and defects, only on individual graphene particles, which do not represent the properties of "bulk" material. To address these limitations, we developed and validated thermogravimetric analysis (TGA) as a simple analytical tool for characterization and quality control of manufactured few-layer graphene (FLG) and their non-graphene impurities in powder forms. Our results, using verified control and industrial samples, revealed that the derivative TGA graphs of FLG, graphene oxide and graphite powders have signatory distinctive peaks with temperature of maximum mass decomposition rates (T max) in specific ranges, reflecting differences of their structural, chemical, and thermal properties, which are suitable for their qualitative and quantitative analysis. The method is applicable for graphene manufacturers and end-users for simple, low-cost and reliable quality control of graphene materials that will not fail to detect "fake" graphene. [Display omitted] • A TGA method for quality control of graphene powders is introduced and validated. • Method allows quantitative and qualitative analysis of non-graphene components in graphene. • Number DTG peaks, their position and area are identified as key analytical parameters. • It is recommended as simple low-cost and reliable method to detect "fake graphene". [ABSTRACT FROM AUTHOR]

In the present paper, synthesis and characterizations of flexible dielectric and ferroelectric polymer films combining different ratios of graphene, barium titanate and polydimethylsiloxane are presented. Broad range of characterization techniques were carried out to confirm their, morphological, structural, chemical, thermal and mechanical (flexibility, stretching, bending and twisting) characteristics. Dielectric studies showed that a high dielectric constant of the nanocomposite was dependent on the ratio of graphene:bariumtitanate:polydimethylsiloxane, showing that ratio of 15:25:100 had a high dielectric constant at high frequency range and the ratio 15:30:100 at the low frequency range. At 2 Hz the ratio 15:30:100 showed a dielectric constant of 116.9 which decreased to 30.6 at 2 MHz, thus showing capacitive nature at full frequency range. Meanwhile dielectric loss was very low i.e., 1.3 at 20 Hz and 0.02 at 2 MHz and AC conductivity was 1.6 × 10−7 S/m. Ferroelectric properties like energy density, energy loss and efficiency were calculated and compared. At an electric field of 0.92 kV/cm, remanant polarization and coercive field were 3.9 × 10−4 μC/cm2 and15.82 kV/cm, respectively. Energy density of 0.64 J/m3, energy loss 0.358 J/m3 and efficiency 64.2% were confirmed respectively. Results indicate that the nanocomposite films having desirable performances such as flexibility, thermal stability, high dielectric constant, high energy density are good candidates to be considered in energy storage and memory device applications. [ABSTRACT FROM AUTHOR]

The paper presents the tuning of sensitivity and selectivity performance of volatile organic compounds (VOCs) chemoresistive sensors for biomarker detection using the hybridization of pristine graphene (pG) and metal organic frameworks (MOFs). The synergistic effect of this nanocomposite material was discovered showing improved sensing performances where graphene acts as a highly conductive sensing element, and MOFs, with a high surface area and adsorption capacity provide an enhanced sensitivity and selectivity for specific VOCs. By combining and selecting different MOFs, we proposed that is possible to tailor sensing performances of chemoresistive sensors for VOC biomarkers detection. To prove that graphene hybrid nanocomposite with selected MOFs including copper–benzene-1,3,5-tricarboxylate (pG-Cu BTC), zirconium 1,4-dicarboxybenzene (pG-UiO 66) and 2-methylimidazole zinc salt (pG-ZIF 8), were investigated to enhance the sensing performance and capability of distinguishing different VOC biomarkers (e.g., methanol, ethanol, chloroform, acetone, acetonitrile and THF). Results showed that the pG-Cu BTC sensor has the highest sensitivity and selectivity towards chloroform and methanol VOCs at 2.82–22.6 ppm level. The proposed concept presents a valuable contribution for the development of low-cost and high-performing VOC biomarker sensors for monitoring human health from metabolic human breath and further implementation for non-invasive biomedical diagnostics for personalized telehealth monitoring. Image 10660 [ABSTRACT FROM AUTHOR]

Granular fertilizers should have appropriate mechanical strength to resist significant fracturing during the handling and storage process. Graphene (GN) has the potential to act as a high-performance reinforcement for different composites. This paper provides a comprehensive study of the influence of GN concentration on the crushing strength of two fertilizers (monoammonium phosphate (MAP) and diammonium phosphate (DAP)) with different initial hardness. The results show differences in concentration dependence, with optimum concentration of 0.5% GN for MAP and 0.05% for DAP increasing their crushing strength by 1680% and 67.3%, respectively. The effect of different physicochemical properties of GN, such as method of preparation and specific surface area (SSA) on the crushing strength of the fertilizer was also investigated. Results showed dependence of granules' crushing strength on the method of GN production and their SSA, while GN samples with a high degree of reduction and SSA were more effective than others. Image 1 • Two fertilizers with different initial hardness were granulated with GN. • The crushing strength of co-granulated fertilizers with GN was measured. • Improving crushing strength of granules with GN is related to their initial strength. • There was an optimal GN concentration to enhance crushing strength of granules. • The physicochemical properties of GN influenced the crushing strength of granules. [ABSTRACT FROM AUTHOR]

Abstract Compounds and composites with high dielectric performance are in high demand in electronic industry due to their ability to store more charge and lower energy dissipation. In this paper we present synthesis of flexible three phase nanocomposite films of graphene/titania/polydimethylsiloxane with reasonably high real part of permittivity and very low imaginary part of permittivity. Dielectric permittivity of polydimethylsiloxane was raised by addition of graphene and rutile titania used as conducting and ceramic additives, respectively added in various weight ratios. Dielectric studies of synthesized three phase graphene/titania/polydimethylsiloxane nanocomposite films with weight/weight of 2:15:20 exhibits dielectric permittivity of 34.8 even at very high frequency of 2 MHz. While loss tangent of the same three phase graphene/titania/polydimethylsiloxane nanocomposite film is as low as 0.01 and its AC conductivity is 4.3 × 10−5 Sm−1. Complex impedance and complex electric modulus of three phase graphene/titania/polydimethylsiloxane nanocomposite films also confirm its capacitive behaviour. Based on these properties and results we propose that these type of three phase graphene/titania/polydimethylsiloxane nanocomposite films can be used as useful dielectric materials in energy storage devices. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Magnetic iron oxide nanoparticles decorated graphene gas sensor is presented. • The accurate particle size synthesis was conducted by using poly(ion liquids) (PIL). • The influence of particle size on sensitivity was evaluated. • Particles of a size of 20 nm have a significant enhancement of sensitivity. • The graphene-Fe 3 O 4 sensor detect trace amounts (1 ppm) of the NO 2 and ethanol. Abstract We report a synthesis of magnetic nanoparticles chemically immobilized onto reduced graphene oxide sheets (referred to as rGO-Fe 3 O 4 NPs) as a gas and vapor sensing platform with precisely designed particle size of 5, 10 and 20 nm to explore their influence of particle size on sensing performance. The rGO-Fe 3 O 4 NP sensors have been investigated their responses to different gases and volatile organic compounds (VOCs) at part-per-million (ppm) levels. Results show that the Fe 3 O 4 NPs with smaller size (5 and 10 nm) on the rGO surface led to a lower sensitivity, while particles of a size of 20 nm have a significant enhancement of sensitivity compared to the bare rGO sensor. The rGO-Fe 3 O 4 NP20 sensor can detect trace amounts of NO 2 gas and ethanol vapor at the 1 ppm and is highly selective to the NO 2 and ethanol among other tested gases and VOCs, respectively. The particle size causes different distribution behaviour of NPs over rGO surface and interspaced between them, which results in deceased or increased the surface interactions between gas and graphene. The NPs themselves contained different defects level and the charge depletion layer that affect their adsorption gas/vapor molecules, which are explained for different sensing responses. [ABSTRACT FROM AUTHOR]

The use of pristine graphene (pG) based on solution processed coating technologies is often limited by their poor dispersibility in water and organic solvents which prevents to achieve the best performing properties of pG in coating applications. To address these limitations, we developed a dispersant-free coating approach of pG based on their intrinsic solid-lubricity and interlayer electrostatic interactions. The “rotating drum” method was established to provide suitable conditions for electrostatic deposition of pG-powder which is demonstrated on two model substrates with granular and fibril morphologies (urea and acrylic fibers) to improve their physical and electrical properties. The results showed that the pG coating enables to minimize moisture induced caking tendency of commercial urea prills at a relative humidity (RH) of 85% (higher than critical humidity) exhibiting greater moisture rejection ability (∼2 times higher than uncoated urea) and to improve their anti-abrasive properties. The pG-powder coating applied on nonconductive acrylic fibers provides a stable conductive layer (∼0.8 ± 0.1 kΩ/sq) which made them suitable for using in wearable electronics, sensors and electromagnetic interference (EMI) shielding. The developed coating method for pG-powder based on “rotating drum” is generic, simple, eco-friendly, low-cost, and scalable for broad range of coating applications. [ABSTRACT FROM AUTHOR]

We report a new method for the fabrication of highly conductive and transparent ultrathin nitrogen (N) doped graphene films from graphene inks by combining a microwave treatment, ultrasonic nebulizer coating and thermal annealing. The starting graphene oxide (GO) solution was mixed with poly(ionic liquids) (PIL) and treated with microwave (Mw) irradiation to prepare Mw-rGO@PIL inks, which is a gentle reduction of PIL-attached reduced graphene oxide (rGO). In this non-contacting heating method, the PIL was used to not only mediate microwave irradiation and prevent disorder of the graphitic structure, but also repair the lattice defects and introduce nitrogen into the graphitic structure. The ultra-thin graphene films were prepared using the nebulizer for controlling the aerosol droplet distribution of the Mw-rGO@PIL inks coated onto quartz or glass substrates. The prepared films displayed a surface resistance of ∼1.45 × 10 7  Ω/sq at a transparency of ∼87%. A further thermal treatment was conducted to improve the conductivity of the prepared films by annealing at a high temperature (900 °C), which allowed complete reduction of oxygen containing groups, enhanced graphitization, and reordering of the basal graphene plane and N-doping of the carbon lattice (pyrolytic PIL). The resulting thin films significantly reduced the surface resistance in the range of 1.5 × 10 3 to 6.2 × 10 3  Ω/sq at a transparency ranging from 68 to 82%, respectively. The presented method involving in situ N-doping offers a promising environmentally-friendly, low-cost and scalable manufacture of high-quality conductive N-doped graphene films. [ABSTRACT FROM AUTHOR]

It remains a formidable challenge to develop supercapacitors having both high stretchability and electrochemical performance. A ternary polymer composite was herein developed by engineering graphene platelets (GnPs), poly (3,4-ethylenedioxythiophene) (PEDOT) and manganese dioxide (MnO 2 ) into a kitchen sponge. Cost-effective GnPs having an electrical conductivity of 1460 S cm − 1 were deposited onto the sponge pore surface by a simple dipping and drying process, followed by in situ polymerization of 3,4-ethylenedioxythiophene. MnO 2 was then deposited onto the GnPs and PEDOT layers through soaking the GnP/PEDOT sponge into KMnO 4 solution. When the composite was used as the electrodes for a flexible, stretchable supercapacitor, we obtained not only high specific capacitance but a high stretchability up to 400%. The supercapacitor demonstrated a specific capacitance of 802.99 F g − 1 and an energy density of 55.76 Wh kg − 1 , with 99% capacitance retention over 1000 stretching cycles; these are attributed to the synergy between the composite components as well as the wavy device structure. The mass and thickness of the MnO 2 layer was found to increase with the soak, leading to the enhancement of electrochemical performance of GnP/PEDOT/MnO 2 sponge electrodes, i.e. 368.96 F g − 1 for 5 min and 740.25 F g − 1 for 10 min. [ABSTRACT FROM AUTHOR]

The outstanding properties of graphene, including its electromechanical property, could be engineered for wearable electronic sensor platforms. The tubular graphene weaved into a mesh or graphene woven fabrics (GWF) has been reported as one of the most sensitive materials for deformation detection, as well as a promising temperature sensor. Herein, we present the performance of our developed flexible, stretchable, and multiple sensitive sensors fabricated from GWF embedded in polydimethylsiloxane (PDMS) film substrate. The GWF/PDMS sensor shows a pressure sensitivity of 0.0142 kPa−1 in a wide linearity range of 0–20 kPa, an outstanding Gauge factor (GF) of 582 at a strain of 6.2 %, and a very high positive sensitivity of 0.0238 °C−1 in the temperature range of 25–80 °C. A practical application as a high sensitivity air pressure sensor able to measure low pressures (in the range of Pa to kPa) was also demonstrated. This sensor platform having desirable performance characteristics is an excellent candidate for wearable devices in the healthcare sector. [Display omitted] • Graphene mesh-like architecture deposited on PDMS film uses as a piezo-resistive material. • The flexible and stretchable nanocomposite shows multi-sensing with different external stimuli. • Highly sensitive pressure, strain and temperature of GWF/PDMS sensors is an excellent candidate for wearable devices. • The high performance of the sensor compared with other sensing materials can be attributed to the unique structure of the GWF. • This sensor platform having desirable performances are a promising choice for practical application in the healthcare sector. [ABSTRACT FROM AUTHOR]

We report a green approach for synthesis of graphene–carbon nanotube aerogels with three dimensional (3D) interconnected networks prepared from natural graphite rocks. A one-step reaction under the synergic effects of the reduction of graphene oxide (GO) sheets and acid treated carbon nanotubes (CNTs) by ferrous ion is employed eliminating the use of harsh chemicals for the reduction of GO. CNTs are incorporated into the network to increase the robustness and hydrophobicity of aerogels with excellent porosity and oleophilic properties. The prepared aerogels exhibit outstanding adsorption performance for the removal of petroleum products, fats and organic solvents especially under continuous vacuum regime showing adsorption capacity of 28 L of oil per gram of aerogel. The proposed synthetic method is simple and economical for the scalable production of highly porous 3D graphene–carbon nanotube aerogels, which can be successfully used for efficient and cost-effective oil spill clean-up and water purification. [ABSTRACT FROM AUTHOR]

In this work we investigate the crystal transformation and optical properties of hydrothermal titania nanotube (TNT) when combining with large size of exfoliated graphene achieved by electrochemical process (EC-Gr). The TNT monoclinic structure has been changed to TiO 2 anatase phase when TNT was grown in the presence of graphene dispersion. The effect of graphene on the evolution of TNT crystal could be understood by the interaction of carbon elements in graphene and Ti4+ ions in the titania structure. Due to the carrier separation which reduced recombination rate of excited photoelectrons and holes revealed by photoluminescence characterizations, the visible light photocatalytic activity in degradation of methylene blue in solution of the composite was enhanced. The photocatalytic enhancement was discussed and clarified based on UV–vis diffuse absorption spectra and time-resolved photoluminescence investigation. • The TNT@EC-Gr photocatalyst was successfully synthesized by a facile hydrothermal method. • TNT was transformed from monoclinic to anatase phase in nanocomposite. • MB dye degradation performance under sunlight was improved in nanocomposite. • Compositing with graphene reduced the band gap and prolonged the carriers' lifetime. • The bandgap diagram was proposed to elucidate the photocatalytic mechanism. [ABSTRACT FROM AUTHOR]