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Abstract A disposable screen-printed sensor has been crafted specifically for therapeutic drug monitoring purposes, particularly for detecting ofloxacin in biological fluids. To enhance selectivity toward ofloxacin, a supramolecular calix [6] arene serves as the ionophore of choice. The sensor incorporates a graphene nanocomposite as an ion-to-electron transducer layer, which not only boosts potential stability but also mitigates potential drift. The developed ofloxacin sensor underwent rigorous characterization following IUPAC guidelines. The linearity range spans from 1 × 10–6 to 1 × 10–2 M, with a measured slope of 59.0 mV/decade. Impressively, it boasts a percentage recovery of 100.18 ± 1.60 and a low detection limit (LOD) of 6 × 10–7 M. Stability assessments indicate reliable performance over an extended period of 8 weeks. The versatility of this sensor extends to various applications, including the determination of ofloxacin in pharmaceutical formulations, bulk powder, and biological fluids. Notably, it has demonstrated efficacy post-bioanalysis validation, adhering to Food and Drug Administration regulations. This advancement holds promise for personalized therapeutic drug monitoring in clinical pharmacy studies and quality control laboratories, thereby optimizing patient care at the point-of-care. Graphical abstract

A disposable screen-printed sensor has been crafted specifically for therapeutic drug monitoring purposes, particularly for detecting ofloxacin in biological fluids. To enhance selectivity toward ofloxacin, a supramolecular calix [6] arene serves as the ionophore of choice. The sensor incorporates a graphene nanocomposite as an ion-to-electron transducer layer, which not only boosts potential stability but also mitigates potential drift. The developed ofloxacin sensor underwent rigorous characterization following IUPAC guidelines. The linearity range spans from 1 × 10–6 to 1 × 10–2 M, with a measured slope of 59.0 mV/decade. Impressively, it boasts a percentage recovery of 100.18 ± 1.60 and a low detection limit (LOD) of 6 × 10–7 M. Stability assessments indicate reliable performance over an extended period of 8 weeks. The versatility of this sensor extends to various applications, including the determination of ofloxacin in pharmaceutical formulations, bulk powder, and biological fluids. Notably, it has demonstrated efficacy post-bioanalysis validation, adhering to Food and Drug Administration regulations. This advancement holds promise for personalized therapeutic drug monitoring in clinical pharmacy studies and quality control laboratories, thereby optimizing patient care at the point-of-care. [ABSTRACT FROM AUTHOR]

Numerous scientific and technological developments in wastewater treatment procedures are brought on by the shortage of clean water supplies. Heavy metals' recalcitrance in wastewater has been shown to be a difficult issue. Further, drinking water quality must be at its highest for human health to be at its best; nevertheless, a number of human activities are continuously degrading it, which has an effect on human health either directly or indirectly. Because heavy metals are the primary causes of many chronic illnesses and have a tendency to bio accumulate, they are giving rise to a lot of worries. Technologies from all over the world are being developed to address the demand for clean drinking water. The objective of the current study is to raise awareness of the need to remove dangerous dense metals from various types of wastewater and the application of modified graphene nanocomposite for their adsorption-based removal. Graphene-based nanocomposite materials have been picked for this application due to their large surface area, superior mechanical strength, and reactivity towards polar and nonpolar contaminants for the electrostatic emission of the heavy metal ions arsenic (As), chromium (Cr), copper (Cu), and lead (Pb). [ABSTRACT FROM AUTHOR]

Under thermal environment and axial forces, the dynamic instability of functionally graded graphene platelet (GPLs)-reinforced porous beams on an elastic foundation is investigated. Three modes of porosity distributions and GPL patterns are considered. The governing equations are given by the Hamilton principle. On the basis of the differential quadrature method (DQM), the governing equations are changed into Mathieu–Hill equations, and the main unstable regions of the porous composite beams are studied by the Bolotin method. Thermal buckling and thermo-mechanical vibration problems are also studied. The effects of porosity coefficients and GPL weight fraction, dispersion pattern, initial thermal loading, slenderness ratio, geometry and size, boundary conditions, and foundation stiffness are discussed. The conclusions show that an elastic foundation has an obvious enhancement effect on thermal buckling, free vibration, and dynamic instability, which improves the stiffness of the beam. [ABSTRACT FROM AUTHOR]

Two different types of graphene materials were used as functional nanofillers for the mechanical and tribological improvement of silicon carbide/graphene nanocomposites. On the one hand is thermally reduced graphite oxide (TRGO) reduced at three different temperatures, and on the other hand is graphene made of three different organic precursors, which were directly coated on silicon carbide (SiC) platelets (GSiC). Additionally, benchmark materials were also used as carbon fillers. The SiC/graphene nanocomposites with 2 wt% filler content were manufactured by pressureless sintering (PLS). Some composites were produced with higher graphene contents of 4% and 8% and sintered by spark plasma sintering (SPS). Microstructural analyses were conducted using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Underwater lubrication, the SP sintered TRGO and GSiC materials with high graphene content have shown the most promising tribological performance. Furthermore, the reduced size of the homogeneously distributed nanoparticles promotes the formation of surface states, which improve the friction and wear properties. [ABSTRACT FROM AUTHOR]

The development of a newly fabricated ion-selective electrode (ISE) solid-contacted type for the determination of prucalopride succinate represents a significant advancement in analytical chemistry, particularly in the context of green chemistry principles. The optimization process involved numerous trials to ensure the selection of a cation exchanger and ionophore that offer high sensitivity and selectivity for prucalopride succinate. Through these optimization trials, sodium tetrakis was identified as the most suitable cation exchanger, while calix [8] arene demonstrated the highest affinity towards prucalopride succinate as the ionophore. This careful selection of components ensures accurate and specific detection of prucalopride succinate. To enhance the electroanalytical performance of the ISE, a graphene nanocomposite layer was developed as an ion-electron transducer between the carbon and synthetic polymeric membrane. This graphene-nanocomposite layer improves the overall performance of the ISE, providing a Nernstian slope of 57.249 mV per decade, which aligns with the recommendations of the International Union of Pure and Applied Chemistry (IUPAC). The integration of these components and the utilization of green chemistry principles in the design of the fabricated ISE enable rapid and accurate determination of prucalopride succinate. This innovative approach holds great potential for applications in pharmaceutical analysis and quality control, providing a more sustainable and efficient method for the analysis of prucalopride succinate., Competing Interests: Declarations. Ethics approval and consent to participate: All samples used in this study were provided willingly by the authors and as such neither ethical approval nor participant consent were required. Consent for publication: Not applicable. Consent to participate: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

We fabricated a novel nanocomposite composed of graphene-La2CrFeW6 perovskite compounds with an organic-inorganic counter electrode based on CdSe, gallic acid, urea and sulfate in dye-sensitized solar cells (DSSCs) by a simple hydrothermal technique. The nanocomposite shows an excellent electro–catalytic activity with low charge-transfer resistance, due to the synergetic catalytic effects of the graphene sheets and La2CrFeW6 perovskite with organic-inorganic materials. The special structure of this nanocomposite also improves the active sites for reduction of triiodide ions on the counter electrodes. The photo-conversion efficiency of the DSSC fabricated using a gallic-based counter electrode reached a higher value of 10.40% under standard illumination (1 sun, 100 mW cm−2, AM 1.5), as compared to the traditional Pt electrode (7.49%). The graphene-La2CrFeW6 fabricated with an organic-inorganic based CE was also found to be more efficient than those reported in previous works, in which graphene, produced by various methods, was used as a CE material. Therefore, the present nanocomposite is considered an environmentally friendly, low-cost, and highly efficient CE material for DSSCs.

In this study, the electrocatalytic behavior of tin sulfide doped with various metallic elements (copper, cobalt, nickel, and iron) for the oxygen reduction reaction was investigated. Our findings reveal cobalt as the most effective dopant in enhancing ORR efficiency. The graphene nanosheets were introduced to form a G/Co-SnS 2 nanocomposite, which significantly improved ORR performance, surpassing Pt/C in current density. Our findings underscore the positive impact of chemical doping and the synergistic effect of SnS 2 with graphene nanosheets, improving the onset potential and facilitating the ORR. Through comprehensive characterization including XRD, XPS, FESEM, and BET analysis, the structural and surface properties of the materials were evaluated. Employing the Rotating Disk Electrode technique, we observed that G/Co-SnS 2 exhibited a superior onset potential of 0.88 V vs. RHE and high current density of 6.12 mA cm−2, indicating enhanced ORR facilitation. Furthermore, Electrochemical Impedance Spectroscopy revealed lower resistance in the G/Co-SnS 2 nanocomposite compared to other samples, highlighting its enhanced durability. Additionally, G/Co-SnS 2 nanocomposite demonstrated significantly enhanced durability in comparison to the costly Pt/C catalyst, further underscoring its potential as a robust alternative for catalyzing the oxygen reduction reaction. These comprehensive characterizations provide insights into the enhanced electrocatalytic performance observed. Overall, this study highlights the promising potential of Co-doped SnS 2 in combination with graphene nanosheets for efficient oxygen reduction reactions, opening avenues for advanced electrocatalytic materials in energy applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Under thermal environment and axial forces, the dynamic instability of functionally graded graphene platelet (GPLs)-reinforced porous beams on an elastic foundation is investigated. Three modes of porosity distributions and GPL patterns are considered. The governing equations are given by the Hamilton principle. On the basis of the differential quadrature method (DQM), the governing equations are changed into Mathieu–Hill equations, and the main unstable regions of the porous composite beams are studied by the Bolotin method. Thermal buckling and thermo-mechanical vibration problems are also studied. The effects of porosity coefficients and GPL weight fraction, dispersion pattern, initial thermal loading, slenderness ratio, geometry and size, boundary conditions, and foundation stiffness are discussed. The conclusions show that an elastic foundation has an obvious enhancement effect on thermal buckling, free vibration, and dynamic instability, which improves the stiffness of the beam.

In the recent drug analysis arena, optimizing a green, eco-friendly, and cost-effective technique is the main target. In order to cope with green analytical chemistry principles and the trending development of miniaturized portable and handheld devices, an innovative microfabricated ion-selective electrode for the analysis of metoclopramide (MTP) was developed. The fabricated electrode adopted a two-step optimization process. The first step of optimization depended on screening different ionophores in order to enhance the sensor selectivity. Calix-4-arene showed the maximal selectivity towards MTP. The second step was utilizing a graphene nanocomposite as an ion-to-electron transducer layer between the calix-4-arene polymeric membrane and the microfabricated copper solid-contact ion-selective electrode. The graphene nanocomposite layer added more stability to electrode potential drift and short response times (10 s), probably due to the hydrophobic behavior of the graphene nanocomposite, which precludes the formation of a water layer at the Cu electrode/polymeric membrane interface. The proposed MTP sensor has been characterized according to IUPAC recommendations and the linear dynamic range estimated to be 1 × 10−6 to 1 × 10−2 M with LOD of 3 × 10−7 M. The proposed sensor has been successfully employed in the selective determination of MTP in bulk powder, pharmaceutical formulation, and biological fluid. No statistical significant difference was observed upon comparing the results with those of the official method. The Eco-score of the method was assessed using the Eco-Scale tool and was compared with that of the official method. [ABSTRACT FROM AUTHOR]

Temperature and the alignment state of nanofillers are two important factors that can greatly affect the thermal conductivity of graphene nanocomposites, but the simultaneous influence of these two issues have never been considered in any theoretical treatment. In this work we incorporate the contributions of electron-phonon coupling and phonon-phonon interaction into the diffuse mismatch model to establish the temperature dependence of filler-matrix interfacial thermal resistance and filler-filler contact resistance, both crucial for thermal conduction in graphene nanocomposites. The electron and phonon transport mechanisms, suitable for metal and nonmetal matrices respectively, are both taken into account. Then through an effective-medium approximation based on Maxwell's far-field matching, the temperature-dependent thermal conductivity of both metal and nonmetal-based graphene nanocomposites is derived. By further introducing a confinement angle with respect to the main alignment direction wherein the graphene nanofillers are supposed to be dispersed, the influence of the alignment state of graphene nanofillers is also investigated. We highlight this newly developed theory with direct comparisons to several sets of experimental data, and demonstrate the significant effects of temperature level and alignment state in thermal conductivity of graphene metal and nonmetal nanocomposites. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Personal care products (PCPs) have a prospective influence on human health, and their vast use may cause health effects such as breast cancer. In that perspective, current study is focused on designing a porous N-doped graphene-NiO nano-composite for adsorption of PCPs. Facile, easy and green onepot synthesis via electrochemical/microwave-assisted method was applied. One family, parabens, of PCPs has been selected to be removed from water. Methyl, ethyl, propyl and butyl parabens were removed in single and competitive adsorption systems. The kinetics, thermodynamics, equilibrium, and adsorption behavior under varied pH and dosage were investigated. Recycling of exhausted adsorbent was also studied. The adsorption amount of methyl, ethyl, propyl and butyl parabens was 3.12, 5.28, 8.42 and 10.46 mg g-1 adsorbent under the optimum conditions. It was found that the process obeyed pseudo-second-order kinetic model and both Langmuir and Temkin isotherm models satisfactorily. The process was thermodynamically spontaneous and endothermic. Results revealed that the prepared adsorbent is recyclable and its removal mechanism involves hydrophobic as well as p-p interactions. [ABSTRACT FROM AUTHOR]

Abstract We report the synthesis of Mn 3 O 4 nanostructures and their graphene composites following a novel, surfactant free, single-step hydrothermal method. The structural and morphological characterizations of graphene wrapped Mn 3 O 4 nano-octahedrons (Mn 3 O 4 -rGO) are carried out using powder X-ray diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, Field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). We study the electrochemical properties of as-prepared Mn 3 O 4 and Mn 3 O 4 -rGO composite as anodes for lithium ion batteries (LIBs). Mn 3 O 4 -rGO composite electrode showed excellent electrochemical properties when cycled against Li/Li+, with a reversible specific capacity of 474 mAh g−1 at 100 mA g−1 upon 200 cycles. Further, we investigate the kinetics behavior of these electrodes and study their capacitive contribution towards total charge storage. With a high capacitive contribution of ∼73% at 1.0 mV s−1, Mn 3 O 4 -rGO composite electrode exhibits excellent potential for their application in lithium ion battery and hybrid lithium ion capacitor devices. Graphical abstract Image 1 Highlights • One-step synthesis of Mn 3 O 4 /rGO composite with unique morphology is demonstrated. • Mn 3 O 4 /rGO composite electrode exhibits enhanced electrochemical properties. • Excellent Li-ion kinetics is shown with a capacitive nature of ∼73% at 1.0 mV s−1. • Mn 3 O 4 /rGO composite electrode shows potential as efficient anode for LIBs. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Highly active tin doped zirconia/graphene nanocomposite was successfully prepared. • Synthesis of DMC was catalysed by a novel Zr–Sn–O/GO nanocomposite catalyst. • This method produced 82.4% PC conversion and 78.2% yield of DMC. • Novel catalyst was reused several times without affecting its catalytic performance. • Experimental and model predicted values showed an excellent agreement. Abstract A green, rapid and continuous hydrothermal flow synthesis (CHFS) route has been employed to synthesise highly efficient and active novel heterogeneous catalysts. Tin doped zirconia (Zr–Sn–O) and tin doped zirconia/graphene nanocomposite (Zr–Sn/GO) have been assessed as suitable heterogeneous catalysts for the synthesis of dimethyl carbonate (DMC). The catalysts have been extensively characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area measurement and X-ray photoelectron spectroscopy (XPS) analysis. Extensive batch studies for the synthesis of DMC via the transesterification of propylene carbonate (PC) and methanol (MeOH) using Zr–Sn/GO catalyst in a solvent free process were also conducted. The effect of various reaction conditions such as reactant molar ratio, catalyst loading, reaction temperature and reaction time has been extensively evaluated. Response surface methodology based on Box-Behneken Design (BBD) was employed to derive optimum conditions for maximising PC conversion and DMC yield. The correlations and interactions between various variables such as MeOH:PC ratio, catalyst loading, reaction temperature, reaction time and stirring speed were extensively studied. A quadratic model by multiple regression analysis for the PC conversion and DMC yield was developed and verified by several methods BBD revealed that optimum conditions for high yield values of DMC are 12.33:1 MeOH:PC molar ratio, 446.7 K, 4.08 h and 300 rpm using 2.9% (w/w) Zr–Sn/GO nanocomposite. The maximum predicted responses at the optimum conditions are 85.1% and 81% for PC conversion and yield of DMC respectively. Experimental results at optimum model predicted reaction conditions agree very well with the model predicted response, where 82.4% PC conversion and 78.2% yield of DMC were obtained. Catalyst reusability and stability studies have been conducted at optimum reaction condition to investigate the long term stability of Zr–Sn/GO and it has been found that the catalyst could be reused more than six times (about 42 h) without losing its catalytic activity. These experimental and model predicted values showed an excellent agreement for tin doped zirconia/graphene nanocomposite as a heterogeneous catalyst for the synthesis of DMC from PC and MeOH. [ABSTRACT FROM AUTHOR]

For the first time, a simple and rapid sonochemical technique for preparing of pure Cd 2 SiO 4 nanostructures has been developed in presence of various surfactants of SDS, CTAB and PVP. Uniform and fine Cd 2 SiO 4 nanoparticle was synthesized using of polymeric PVP surfactant and ultrasonic irradiation. The optimized cadmium silicate nanostructures added to graphene sheets and Cd 2 SiO 4 /Graphene nanocomposite synthesized through pre-graphenization. Hydrogen storage capacity performances of Cd 2 SiO 4 nanoparticle and Cd 2 SiO 4 /Graphene nanocomposite were compared. Obtained results represent that Cd 2 SiO 4 /Graphene nanocomposites have higher hydrogen storage capacity than Cd 2 SiO 4 nanoparticles. Cd 2 SiO 4 /Graphene nanocomposites and Cd 2 SiO 4 nanoparticles show hydrogen storage capacity of 3300 and 1300 mAh/g, respectively. [ABSTRACT FROM AUTHOR]

In order to improve the electrochemical properties of LaMnO 3 perovskite (LMO) materials for supercapacitor applications, different amount of nitrogen-doped reduced graphene oxide (N-rGO) from 25 to 75 wt % has been incorporated with LMO to form nanocomposite materials. These three-dimensional structures are assembled through electrostatic attraction of the positive charged N-rGO and the negative charged LMO. The amount of N-rGO has a significant effect on the properties of the composite materials. Microscopic investigations confirm that LMO particles are wrapped by N-rGO sheets, and with the increase of N-rGO content, the dispersion of LMO particles in graphene matrix is enhanced. Electrochemical characterizations reveal that the specific capacitance of the nanocomposites has been dramatically improved. Compared with pristine graphene and LMO, the sample with a lower amount of N-rGO (25%) exhibited the highest specific capacitance (687 Fg −1 at 5 mVs −1 ) and the longest stability (79% retention after 2000 cycle at 10 Ag −1 ) among other composite materials. The superior capacitive properties make LMO/N-rGO nanocomposites stand out as a promising candidate for supercapacitor applications. [ABSTRACT FROM AUTHOR]

The present work focused on electromagnetic (EM) absorption performance comparison of different polymer nanocomposite structures. Synthesis and fabrication of polymer nanocomposite composed of graphene, polyurethane (PU), epoxy was done using in situ polymerization and resin transfer moulding respectively. The effect of polymer on EM properties of composite was carried out using waveguide measurement technique in X-band. Reflection Loss (RL) and shielding effectiveness (SE) were measured for various nanocomposites using EM wave theory. From the results it is observed that 2.5 wt% of PU/epoxy graphene nanocomposite has shown RL value −35 dB at 12.1 GHz and SE value of −45 dB.

A novel binary nanocomposite, ZnO/nitrogen-doped graphene (ZnO/NG), is synthesized via a facile solution method. In this prepared ZnO/NG composite, highly-crystalline ZnO nanoparticles with a size of about 10 nm are anchored uniformly on the N-doped graphene nanosheets. Electrochemical properties of the ZnO/NG composite as anode materials are systematically investigated in lithium-ion batteries. Specifically, the ZnO/NG composite can maintain the reversible specific discharge capacity at 870 mAh g−1 after 200 cycles at 100 mA g−1. Besides the enhanced electronic conductivity provided by interlaced N-doped graphene nanosheets, the excellent lithium storage properties of the ZnO/NG composite can be due to nanosized structure of ZnO particles, shortening the Li+ diffusion distance, increasing reaction sites, and buffering the ZnO volume change during the charge/discharge process. [ABSTRACT FROM AUTHOR]

This paper investigates the parametric instability of functionally graded graphene reinforced nanocomposite plates that undergo a periodic uniaxial in-plane force and a uniform temperature rise. The plate is composed of multiple graphene platelet reinforced composite (GPLRC) layers in which graphene platelets (GPLs) are uniformly distributed in each individual layer with GPL concentration varying layer-wise across the plate thickness. The modified Halpin–Tsai model that takes into account the GPL geometry effect is employed to calculate the Young's modulus of the GPLRC. Based on the first-order shear deformation theory, the governing equations are deduced and then are solved by using the differential quadrature approach integrated with the Bolotin's method. A parametric study is undertaken to show the influences of GPL distribution pattern, concentration and geometry, temperature change, static in-plane force, plate geometry and boundary condition on the parametric instability of functionally graded multilayer GPLRC plates. It is found that the addition of a small amount of GPL reinforcements considerably increases the critical buckling load and natural frequencies but reduces the size of unstable region. The reinforcing effect is the best when the surface layers of the plate are GPL-rich. [ABSTRACT FROM AUTHOR]

Fouling of marine surfaces has been a perpetual problem ever since the days of the early sailors. The tenacious attachment of seaweed and invertebrates to man-made surfaces, notably on ship hulls, has incurred undesirable economic losses. Graphene receives great attention in the materials world for its unique combination of physical and chemical properties. Herein, we present a novel 2-step synthesis method of graphene-silver nanocomposites which bypasses the formation of graphene oxide (GO), and produces silver nanoparticles supported on graphene sheets through a mild hydrothermal reduction process. The graphene-Ag (GAg) nanocomposite combines the antimicrobial property of silver nanoparticles and the unique structure of graphene as a support material, with potent marine antifouling properties. The GAg nanocomposite was composed of micron-scaled graphene flakes with clusters of silver nanoparticles. The silver nanoparticles were estimated to be between 72 and 86 nm (SEM observations) while the crystallite size of the silver nanoparticles (AgNPs) was estimated between 1 and 5 nm. The nanocomposite also exhibited the SERS effect. GAg was able to inhibit Halomonas pacifica , a model biofilm-causing microbe, from forming biofilms with as little as 1.3 wt.% loading of Ag. All GAg samples displayed significant biofilm inhibition property, with the sample recording the highest Ag loading (4.9 wt.% Ag) associated with a biofilm inhibition of 99.6%. Moreover, GAg displayed antiproliferative effects on marine microalgae, Dunaliella tertiolecta and Isochrysis sp. and inhibited the growth of the organisms by more than 80% after 96 h. The marine antifouling properties of GAg were a synergy of the biocidal AgNPs anchored on the stable yet flexible graphene sheets, providing maximum active contact surface areas to the target organisms. [ABSTRACT FROM AUTHOR]

Carbon nanomaterials such as graphene and its derivatives based membranes in real applications are still far from reality due to their hydrophobic nature and limitations in their fabrication process. Here, we have devised a simple and feasible fabrication method to bring the high end nanocarbon based material to real downstream applications. In order to achieve this objective, the wettability of graphene was initially increased to an ultra-wetting level by incorporating amine and carboxyl functionality onto the graphene. The amine and carboxylated graphene is then covalently attached to a polymer matrix to fabricate a water filtration membrane. The characterization of the modified supported graphene-based membrane indicates that significantly higher hydrophilicity than previously expected is achieved, with the water contact angle reduced to zero. The ultra-wetting graphene increases the water permeability of the membrane by 126% without any changes in the selectivity. Based on our findings, we conclude that the ultra-wetting graphene will be an ideal material for new generation water filtration membranes. [ABSTRACT FROM AUTHOR]

• Natural vibration of FG-GPLRC beam-fluid interaction systems is investigated for the first time. • The 3D Halpin-Tsai model is derived to estimate the elastic modulus of 3D-random graphene nanocomposites. • The multidomain GDQ method together with an iteration procedure is used to determine the natural frequencies. • The beam-fluid interaction reduces the fundamental frequency most, but it hardly affects the first order vibration mode. This paper presents the free vibration analysis of functionally graded graphene platelets reinforced composite (FG-GPLRC) beams partially in contact with fluid based on the first-order shear deformation theory (FSDT). By considering the 3D-random orientation of graphene platelets (GPLs), the 3D Halpin-Tsai model is introduced to calculate the elastic modulus of graphene nanocomposites. The fluid velocity potential and hydrodynamic loading are determined by virtue of variable separation method. The equations of motion are derived by using Hamilton's principle and the natural frequencies are determined by the multidomain generalized differential quadrature (GDQ) approach together with an iterative scheme. Parametric studies are carried out to evaluate the influences of GPL distribution pattern, weight fraction and dimension, fluid depth and density, beam geometry and end supports on the free vibration behaviour of FG-GPLRC beam-fluid interaction systems. Results show that the beam-fluid interaction reduces the fundamental frequency most, but it hardly affects the first order vibration mode. [ABSTRACT FROM AUTHOR]

A reduced graphene oxide/chitosan (rGO/Chi) nanocomposite film for chemoresistive trimethylamine sensing was prepared by solution-phase mixing and deposited on nylon membrane via vacuum assisted self-assembly (VASA) method. The film was analysed using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The electrical property of the prepared films were measured by four-point probe measurement. Using 0.40% volume fraction (v.f) it was exposed to trimethylamine vapour and its electrical resistance quickly changed. The composite film sensor exhibited linear range from 23 to 230mg/L (r 2 = 0.9774) and the calculated limit of detection was 20.56mg/L. It exhibited a repeatable response to trimethylamine gas. [ABSTRACT FROM AUTHOR]

Development of high-efficiency electrocatalysts for pH-universal overall water splitting is a critical step towards a sustainable hydrogen economy. Herein, graphene nanocomposites with Ru-RuO 2 Mott-Schottky heterojunctions (Ru-RuO 2 @NPC) are prepared pyrolytically and exhibit a remarkable electrocatalytic activity at pH = 0–14 towards both oxygen/hydrogen evolution reactions and overall water splitting, as compared to commercial RuO 2 and Pt/C. Ru-RuO 2 @NPC can also be used as an effective air cathode catalyst for flexible, rechargeable zinc-air batteries. Density functional theory calculations show that the formation of Ru-RuO 2 heterojunctions moderately enhances the surface charge density of metallic Ru and brings the d states closer to Fermi level, as compared to that of RuO 2 alone, leading to improved intrinsic electrocatalytic activity towards these important reactions. These results demonstrate the significance of Mott-Schottky heterojunctions in the development of high-efficiency electrocatalysts for various new energy technologies. [Display omitted] • Doped carbon nanocomposites with Ru-RuO 2 Mott-Schottky heterojunctions. • Modulation of electronic structures by interfacial charge transfer. • Bifunctional electrocatalysts for pH-universal water splitting. • Oxygen catalysts for flexible metal-air battery. [ABSTRACT FROM AUTHOR]

The large-amplitude free vibration behaviors of rotating pre-twisted functionally graded (FG) nanocomposite multilayered blade reinforced with graphene platelets (GPLs) in a thermal environment is comprehensively investigated in the paper. It is assumed that the GPLs volume fraction varies gradually from layer to layer across the blade thickness direction but remains constant in each individual GPLs-reinforced composite (GPLRC) layer. The modified Halpin-Tsai micromechanical model is exploited to obtain the effective Young's modulus of each GPLRC layer while Poisson's ratio, mass density, and thermal expansion coefficient are determined via Voigt's rule. The nonlinear dynamic model of pre-twisted GPLRC blades at moderate rotational speed in a thermal environment is derived based on the first-order shear deformation theory (FSDT) combined with the improved version of the Novozhilov nonlinear shell theory. The nonlinear vibration characteristics of FG GPLRC blades are obtained by applying the element-free improved moving least-square Ritz (IMLS-Ritz) method in conjunction with a direct iterative scheme. Validation of obtained results is performed in detail and show effectiveness of used numerical approach and fast convergence of obtained results to exact values. The impacts of rotating speed, pre-twisted angle, presetting angle, and aspect ratio on nonlinear to linear frequency ratio of GPLRC blades are studied with emphasis on temperature rise and nano reinforcement parameters. Finally, new insights into dynamics of nanocomposite rotating blades with conclusions are presented in detail. [ABSTRACT FROM AUTHOR]

The sulfur on the sulfur-assisted reduced graphene oxide (SrGO) surface provides the origin of poly(phenylene sulfide) PPS-grafting via SNAr mechanism. In-situ polymerization from sulfur on SrGO afforded surface modification of SrGO, resulting in enhanced dispersibility in PPS. The tensile strength, electrical and thermal conductivities, and flame retardancy of PPS-coated SrGO were efficiently enhanced using highly concentrated SrGO and masterbatch (MB) for industrial purposes. Three-dimensional X-ray microtomography scanning revealed that diluting MB in the PPS resin afforded finely distributed SrGO across the PPS resin, compared to the aggregated state of graphene oxide. For the samples after dilution, the thermal conductivity and flame retardancy of PPS/SrGO are preserved and typically enhanced by up to 20%. The proposed PPS/SrGO MB shows potential application as an additive for reinforced PPS due to the ease of addition during the extrusion process. [ABSTRACT FROM AUTHOR]

In this paper, a meshless method has been developed to analyze stresses and deflections in an advanced smart lightweight sandwich plate (ASLSP) subjected to thermo-electro-mechanical loads. In ASLSP, a passive sandwich plate consisting of a lightweight porous core and two graphene nanocomposite layers is integrated between two active piezoceramic faces. Moreover, functionally graded profiles have been considered for the dispersions of porosity and graphene in their corresponding layers. In the meshless method, MLS shape functions has been utilized, and essential boundary conditions are implemented using transformation approach. A version of Halpin-Tsai equations capable of capturing nanoscale effects of randomly oriented graphene is adopted to approximate the temperature dependent mechanical properties of graphene nanocomposite layers. The highly coupled governing equations are extracted by minimizing total energy function obtained from the estimation of displacement domain with Reddy's third order plate theory (called TSDT). The influences of different aspects of ASLSP including loading, graphene content, porosity and geometric details have been studied on thermo-electro-mechanical stresses and deflections. It is observed that both graphene content and dispersion profile have considerable influence on ASLSP's deflections. Moreover, embedding pores in core layer offers a significant reduction in structural weight and a considerable stability in structural bending stiffness. [ABSTRACT FROM AUTHOR]

• Investigation into uniaxial tensile response of a PVA-graphene oxide nanocomposite over a strain rate range of 0.003–1200/s. • Identification and analysis of interfacial slip between polymer matrix and filler as a dominant mechanism influencing the stress–strain response. • Simulation of the mechanical response of the nanocomposite using a modified Mori-Tanaka approach which accommodates the effect of interfacial slip. • Analysis of the rate sensitivity of the nanocomposite by examination of the initial elastic stiffness and stress level at a strain of 0.1, as a function of strain rate. The dynamic stress–strain response of a polyvinyl alcohol (PVA) – graphene oxide (GO) nanocomposite is examined through tensile testing over a strain rate range of 0.003–1200/s, as well as via theoretical microscale modeling. PVA-GO samples with various GO content were prepared and subjected to uniaxial tension using a universal testing machine and a split Hopkinson tension bar arrangement. In previous studies by the authors [1,2] , interfacial slip between the GO flakes and PVA matrix was identified as a key mechanism in the mechanical behavior of the nanocomposite, and a modified Mori-Tanaka (M-T) approach was developed to accommodate the effect of slip. The modified M-T method was employed to model the stress–strain response of the PVA-GO nanocomposite at various strain rates, and close agreement between the theoretical and experimental results was observed. The rate sensitivity of PVA and its nanocomposites was analyzed by determining the initial elastic stiffness of specimens and their stress corresponding to a strain of 0.1, as functions of logarithmic strain rate (log (ε ˙)); it was found that both these parameters increase linearly with log (ε ˙). Moreover, the rate of increase in initial elastic stiffness with log (ε ˙) increases with GO content. In terms of the relationship between the stress at a strain of 0.1 and the logarithmic strain rate (log ε ˙), both PVA and its nanocomposites display curves with similar profiles. [ABSTRACT FROM AUTHOR]

• Study of quasi-static uniaxial loading-unloading tensile response of a PVA-graphene oxide nanocomposite. • Identification of interfacial slip between polymer matrix and filler as a significant factor for the stress-strain response. • Development of an interfacial slip model using finite elements to simulate filler-matrix interaction when interfacial slip occurs. • Incorporation of interfacial slip model into Mori-Tanaka theory to analyze the large deformation stress-strain response of the graphene oxide polymer nanocomposite. A novel modified Mori-Tanaka (M-T) approach to modeling the stress-strain response of graphene nanocomposites subjected to large deformation is described. It is hypothesized that slip at the filler-matrix interface occurs, and this limits the stress which can be transferred to the filler through the interface. Although interfacial slip has a significant influence on the mechanical response of polymer nanocomposites, the M-T method, commonly employed to model nanocomposites, does not accommodate this effect. A pseudo-filler phase is defined to represent the filler when interfacial slip occurs, and this is modeled using finite elements to simulate a single filler flake encapsulated by the interface, interacting with the matrix. The stiffness of the pseudo-filler is determined by examination of the variation of stress in the filler when interfacial slip occurs; this interfacial slip model is incorporated into the M-T method. Quasi-static tensile loading and unloading tests were conducted on polyvinyl alcohol (PVA)-graphene oxide (GO) nanocomposite samples, and significant enhancement of the stress-strain response of the nanocomposite was observed by the addition of GO; e.g. a 5 wt% GO addition increases the initial elastic modulus of PVA from 330 MPa to 1.29 GPa. The modified M-T method was used to simulate the stress-strain response of the nanocomposites, and the theoretical results compare well with experimental stress-strain data for both loading and unloading. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Large amplitude vibration of FG-GPLRC annular plates is investigated. • A DQM-based iterative method is developed to obtain the nonlinear frequencies. • Dispersing more GPLs within outer layers decreases the nonlinear frequency ratio. • The GPL geometry has little influence on the nonlinear vibration behaviour. This paper investigates the large amplitude vibration of functionally graded nanocomposite multilayer annular plates reinforced with graphene platelets (GPLs) in thermal environments. It is assumed that the GPL concentration varies from layer to layer across the plate thickness but remains constant in each individual GPL-reinforced composite (GPLRC) layer, whose elastic modulus is estimated by the modified Halpin-Tsai micromechanics model. Within the framework of first-order shear deformation theory and von Kármán geometric nonlinearity, the governing equations are derived by using the Hamilton's principle and then solve by the differential quadrature method together with an iterative scheme. Numerical results are presented to show the influences of GPL geometry, distribution pattern and concentration, plate geometry, boundary conditions, as well as temperature rise on the nonlinear vibration behaviour of functionally graded GPLRC annular plates. It is found that dispersing more GPLs within the outer layers substantially decreases the nonlinear frequency ratio, while the effect of GPL geometry is insignificant. [ABSTRACT FROM AUTHOR]

• A multifunctional smart sandwich plate with two piezoelectric faces is proposed. • The proposed plate has passive graphene/polymer nanocomposite and porous core layers. • The critical stability mechanical loads and temperature changes of MFSSP are studied. • a mesh-free method incorporated with Reddy's TSDT of plates is developed. The application of piezoelectric layers on the outer surfaces of lightweight passive sandwich plates can offer multifunctional smart sandwich plates (MFSSPs). This paper proposes a new MFSSP and studies its critical stability mechanical loads and temperature changes. The smart plate is proposed to include a multifunctional passive sandwich plate integrated with two active piezoelectric layers. The lightweight sandwich plate has a polymeric porous core and two randomly oriented graphene/polymer nanocomposite layers. Different profiles are considered for graphene and porosity distributions in nanocomposite and core layers, respectively. A modified Halpin–Tsai' approach with efficiency parameters is employed to estimate the material properties of polymer/graphene layers. Reddy's third order shear deformation theory (TSDT) of plates is selected to estimate displacement field and obtain the governing stability equations of the proposed MFSSP. Then, a mesh-free method is developed to solve the obtained mechanical and thermal stability equations. The effect of MFSSP's parameters, including porosity and graphene characteristics, on the stability responses have been studied. The results disclose that the addition of graphene significantly improves the mechanical stability responses of MFSSPs. Furthermore, embedding more pores in core layer can improve the thermal stability of MFSSPs without a considerable reduction in their mechanical stability responses. Image, graphical abstract [ABSTRACT FROM AUTHOR]