Graphene is a suitable transducer for wearable sensors because of its high conductivity, large specific surface area, flexibility, and other unique considerable features. Using a simple, fast galvanic pulse electrodeposition approach, a unique nonenzymatic glucose amperometric electrode was successfully developed based on well-distributed fine Cu nanoparticles anchored on the surface of 3D structure laser-induced graphene. The fabricated electrode allows glucose detection with a sensitivity of 2665 μA/mM/cm2, a response time of less than 5 s, a linear range of 0.03–4.5 mM, and a LOD of 0.023 μM. It also detects glucose selectively in the presence of interfering species such as ascorbic acid and urea. These provide the designed electrode the advantages for glucose sensing in saliva with 97% accuracy and present it among the best saliva-range non-enzymatic glucose sensors reported to date for real-life diagnostic applications.

Flexible supercapacitors (FS) are ideal as power backups for upcoming stretchable electronics due to their high power density and good mechanical compliance. However, lacking technology for FS mass manufacturing is still a significant obstacle. The present study describes a novel method for preparing FS based on reduced graphene oxide (RGO) using the N+ plasma technique, in which N+ reduces graphene oxide on the surface of a cotton/polyester substrate. The effect of aloe vera (AV) as a natural reducing & capping agent and carbon nanotubes (CNT) as nanoconductors on the electrochemical performance of the electrodes is studied. FESEM and XPS were employed to investigate the electrodes' structural and chemical composition of electrodes. The galvanostatic charge–discharge curves of electrodes revealed the enhancement of the electrochemical activity of the as-prepared electrode upon additions of AV and CNT. The areal capacitance of the RGO, RGO/AV, and RGO/ AV/CNT supercapacitors at 5 mV/s was 511, 1244.5, and 1879 mF/cm2, respectively. The RGO electrode showed capacitive retention of 80.9% after 2000 cycles enhanced to 89.7% and 92% for RGO/AV and RGO/AV/CNT electrodes, respectively. The equivalent series resistance of the RGO electrode was 126.28 Ω, decreased to 56.62 and 40.06 Ω for RGO/AV and RGO/ AV/CNT electrodes, respectively.

In this study, the elastic properties of aluminium nanocomposite representative volumetric element (RVE) reinforced with GNP have been analysed. Pure aluminium is lightweight and has low strength which is not suitable for various aerospace applications. Adding graphene to aluminium gives a highly strengthened nano-matrix. A 3D multiscale finite element (FE) representative volumetric element (RVE) has been developed to estimate the mechanical behaviour of GNP-reinforced aluminium graphene nanocomposite (AGNC). The factors influencing the behaviour of AGNC have been investigated with different weight fractions (wt%), sizes and orientations of GNP. The Young’s modulus of AGNC is enhanced by increasing the wt% of GNP and reducing the size of GNP in the aluminium matrix. The Young’s modulus of AGNC with 1% wt% has been enhanced two times and yield strength by five times than pure Al matrix. In the case of different sizes of GNP, the strength of 15-nm-diameter GNP AGNC enhanced two times and medium-sized GNP, i.e. 30 nm has shown a great combination of strength and ductility. After that different orientations have also influenced the mechanical properties and enhancement shown in layered orientation compared to different angles of GNP.

A novel kind of self-assembled graphene quantum dots-Co3O4 (GQDs-Co3O4) nanocomposite was successfully manufactured through a hydrothermal approach and used as an extremely effectual oxygen evolution reaction (OER) electrocatalyst. The characterization of morphology with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that Co3O4 nanosheets combined with graphene quantum dots (GQDs) had a new type of hexagonal lamellar selfassembly structure. The GQDs-Co3O4 electrocatalyst showed enhanced electrochemical catalytic properties in an alkaline solution. The start potential of the OER was 0.543 V (vs SCE) in 1 M KOH solution, and 0.577 V (vs SCE) in 0.1 M KOH solution correspondingly. The current density of 10 mA cm− 2 had been attained at the overpotential of 321 mV in 1 M KOH solution and 450 mV in 0.1 M KOH solution. Furthermore, the current density can reach 171 mA cm− 2 in 1 M KOH solution and 21.4 mA cm− 2 in 0.1 M KOH solution at 0.8 V. Moreover, the GQDs-Co3O4 nanocomposite also maintained an ideal constancy in an alkaline solution with only a small deterioration of the activity (7%) compared with the original value after repeating potential cycling for 1000 cycles.

Owing to the great demand for portable and wearable chemical sensors, the development of all-solid-state potentiometric ion sensors is highly desirable considering their simplicity and stability. However, most ion sensors are challenged by the penetration of water and gas molecules into ion-selective membranes, causing unstable and undesirable sensing performances. In this study, a hydrophobic ionic liquid-modified graphene (Gr) sheet was prepared using a fluid dynamics-induced exfoliation and functionalization process. The high hydrophobicity and electrical double-layer capacitance of Gr make it a potential solid-state ion-to-electron transducer for the development of potentiometric sodium-ion ( Na+) sensors. The as-prepared Na+ sensors effectively prevented the formation of the water layer and penetration of gas species, resulting in stable and high sensing performances. The Na+ sensors showed a Nernstian sensitivity of 58.11 mV/[Na+] with a low relative standard deviation (0.46), fast response time (5.1 s), good selectivity (K < 10− 4), and good durability. Furthermore, the Na+ sensor demonstrated its feasibility in practical applications by measuring accurate and reliable ion concentrations of artificial human sweat and tear samples, comparable to a commercial ion meter.

In the present investigation, a new electrochemical sensor based on carbon paste electrode was applied to simultaneous determine the tramadol, olanzapine and acetaminophen for the first time. The CuO/reduced graphene nanoribbons (rGNR) nanocomposites and 1-ethyl 3-methyl imidazolinium chloride as ionic liquid (IL) were employed as modifiers. The electrooxidation of these drugs at the surface of the modified electrode was evaluated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS) and chronoamperometry. Various techniques such as scanning electron microscopy (SEM) with energy dispersive X-Ray analysis (EDX), X-ray diffraction (XRD) and fourier-transform infrared spectroscopy (FTIR), were used to validate the structure of CuO-rGNR nanocomposites. This sensor displayed a superb electro catalytic oxidation activity and good sensitivity. Under optimized conditions, the results showed the linear in the concentration range of 0.08–900 μM and detection limit (LOD) was achieved to be 0.05 μM. The suggested technique was effectively used to the determination of tramadol in pharmaceuticals and human serum samples. For the first time, the present study demonstrated the synthesis and utilization of the porous nanocomposites to make a unique and sensitive electrode and ionic liquid for electrode modification to co-measurement of these drugs.

Graphene exhibits high carrier mobility and concentration as well as other remarkable properties. Among them, the thermal behaviors of phonon modes play important roles in the application of optical and electronic devices. Here, A–A stacked graphene were proved well by Raman investigation on G and 2D modes. Temperature-dependent Raman scattering measurements on graphene with various number of layers on different substrates were conducted in the temperature range of 80–460 K. The first-order temperature coefficient of single layer graphene (SLG) on SiO2/ Si substrate is obviously smaller than that on Cu foil, indicating that the substrate effect attributes a great impact on graphene phonon temperature dependence. The first-order temperature coefficients of multilayer graphene linearly decrease as the number of layers increases, attributed to the reduction of substrate effect in phonon behaviors, rather than to the anharmonic phonon–phonon (ph–ph) coupling or thermal expansion.

Phytohormones (plant hormones) are a class of small-molecule organic compounds synthesized de novo in plants. Although phytohormones are present in trace amounts, they play a key role in regulating plant growth and development, and in response to external stresses. Therefore, the analysis and monitoring of phytohormones have become an important research topic in precision agriculture. Among the various detection methods, electrochemical analysis is favored because of its simplicity, rapidity, high sensitivity, and in-situ monitoring. Graphene and graphene-like carbon materials have abundant sources, exhibiting large specific surface area, and excellent physicochemical properties. Thus, they have been widely used in the preparation of electrochemical biosensors for phytohormone detection. In this paper, the research advances of electrochemical sensors based on graphene and graphene-like carbon materials for phytohormone detection have been reviewed. The properties of graphene and graphene-like carbon materials are first introduced. Then, the research advances of electrochemical biosensors (including conventional electrochemical sensors, photoelectrochemical sensors, and electrochemiluminescence sensors) based on graphene and graphene-like carbon materials for phytohormone detection is summarized, with emphasis on their sensing strategies and the roles of graphene and graphene-like carbon materials in them. Finally, the development of electrochemical sensors based on graphene and graphene-like carbon materials for phytohormone detection is prospected.

Decabromodiphenyl ether (BDE209) is a persistent aromatic compound widely associated with environmental pollutants. Given its persistence and possible bioaccumulation, exploring a feasible technique to eradicate BDE209 efficiently is critical for today’s environmentally sustainable societies. Herein, an advanced nanocomposite is elaborately constructed, in which a large number of titanium dioxide ( TiO2) nanoparticles are anchored uniformly on two-dimensional graphene oxide (GO) nanosheets ( TiO2/GO) via a modified Hummer’s method and subsequent solvothermal treatment to achieve efficient photocatalytic degradation BDE209. The obtained TiO2/ GO photocatalyst has excellent photocatalytic due to the intense coupling between conductive GO nanosheets and TiO2 nanoparticles. Under the optimal photocatalytic degradation test conditions, the degradation efficiency of BDE209 is more than 90%. In addition, this study also provides an efficient route for designing highly active catalytic materials.

The thermoelectric effect, which converts waste heat into electricity, holds promise as a renewable energy technology. Recently, bismuth telluride (Bi2Te3)-based alloys are being recognized as important materials for practical applications in the temperature range from room temperature to 500 K. However, conventional sintering processes impose limitations on shape-changeable and tailorable Bi2Te3 materials. To overcome these issues, three-dimensional (3D) printing (additive manufacturing) is being adopted. Although some research results have been reported, relatively few studies on 3D printed thermoelectric materials are being carried out. In this study, we utilize extrusion 3D printing to manufacture n-type Bi1.7Sb0.3Te3 (N-BST). The ink is produced without using organic binders, which could negatively influence its thermoelectric properties. Furthermore, we introduce graphene oxide (GO) at the crystal interface to enhance the electrical properties. The formed N-BST composites exhibit significantly improved electrical conductivity and a higher Seebeck coefficient as the GO content increases. Therefore, we propose that the combination of the extrusion 3D printing process (Direct Ink Writing, DIW) and the incorporation of GO into N-BST offers a convenient and effective approach for achieving higher thermoelectric efficiency.

본 연구에서는 공기중에서도 안정적이며 상대적으로 전기음성도가 큰 테플론계열의 고분자와 그래핀플라워를 이용하여 마찰전기 나노발전기를 제작하였다. 상기 복합고분자는 회전도포방법을 이용하 여 나노발전기의 전기적 음성층의 제작에 이용되었다. 전기적 양성층을 위하여 졸-겔 방법을 이용하여 산 화아연막을 제작하였다. 제작된 마찰전기 나노발전기는 약 44 μW의 최대전력을 생산하였다. 결론적으로, 마찰전기 나노발전기의 모든 활성층은 회전도포방법을 이용하였으므로 대면적으로 확장가능하다.

본 연구에서는 PVA(Poly Vinyl Alcohol)섬유와 GO(Graphene Oxide)를 혼입한 섬유보강 콘크리트(FRC)의 역학적 특성 을 평가하고자 하였다. GO와 PVA 섬유를 동시에 혼입한 FRC 각각의 재료를 단일로 사용하였을 때보다 기대효과가 다소 미흡 하였지만, 각 재료의 하이브리드화로 인장강도가 개선되면서 PVA 섬유 혼입률 0.1∼0.3%과 GO 혼입률 0.025%에서 우수한 효 과를 얻을 수 있었다. 특히 PVA 섬유는 0.3%로 혼합하였을 때 부작용을 최소화하면서 최대의 효과를 보였지만, 적절한 GO 배 합비를 조절할 필요가 있으며 FRC내 GO와 PVA 섬유의 최적배합을 구하기 위한 추가적인 연구가 필요할 것으로 사료된다.

How to effectively deal with the polluted water by the pollutant of organic dyes is the world problem. It is of great significance if the organic dyes in the polluted water can be directly turned into the useful materials through a facile approach. Herein, the water which contains the common organic dye, Reactive red 2 (RR2), has been chosen to be the model to synthesize graphene quantum dots (GQDs) by a facile route. The comprehensive characterizations, including TEM (HRTEM), XPS, Raman, PL and UV–Vis. spectra, have been performed to confirm the structures and explore the properties of the synthesized GQDs. Meanwhile, the excellent PL properties and low biotoxicity of the GQDs confer them with the potential applications in the biological fields. When the GQDs are excited by the wavelength of 360 nm, the maximum emission is achieved at 428 nm. It is well demonstrated that the synthesized GQDs are able to detect the Al3+ which causes multiple diseases, such as Parkinson, Alzheimer, kidney disease, and even cancer. The detection range is from 90 to 800 μM, which is different from the reported kinds of the literature. Therefore, this work not only provides an economical and environmental route on solving the universal problem from organic dyes, but also facilitates to advancing the synthesis and application of GQDs.

The present studies explored the possibility of immobilizing phosphocholine (PC) liposomes on the surface of graphene oxide (GO) which was pre-adsorbed with two kinds of enzymes, horseradish peroxidase and glucose oxidase. The transmission electron microscope images showed that the PC liposomes adsorbed onto the GO surface kept integrity. By using 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)-encapsulated liposomes, a one-step colorimetric assay for glucose was developed. In the presence of glucose, the GO nanocomposites catalyzed the cascade enzymatic reaction producing colorimetric signals directly. Under the optimal conditions, the GO nanocomposites produced linearly increased colorimetric signal with increased concentrations of glucose ranging from 50 to 500 μM. The detection limit was 33 μM. The GO nanocomposites also exhibited good selectivity for the detection of glucose and were able to detect glucose in human serum.

PURPOSES : The purpose of this study is to experimentally analyze the flexural strength characteristics of cement mortar mixtures simultaneously incorporated with graphene oxide (GO) and polyvinyl alcohol (PVA) fibers, and to understand the composite effect of those on enhancing resistance against the initiation and progression of micro-cracks, as well as the control of macro-cracks in flexural behavior. METHODS : Cement mortar(w/c=0.5) specimens for flexural strength test, mixing 6 mm and 12 mm PVA fibers at 1% and 2% volume ratios, were fabricated. Additionally, specimens incorporating GO at a cement weight ratio of 0.05% were prepared for each mixture to analyze the effect of GO. Therefore total eight types of mixture were prepared. The fabricated specimens were subjected to flexural strength tests after curing in waterbath for 7 and 28 days. Concurrently, digital images for analyzing deformation in accordance with loading history were obtained at a rate of 20 Hz using the DIC technique. Through displacement and strain calculation via DIC, the flexural behavior characteristics of the mixtures combined with GO and PVA fibers were precisely analyzed. Furthermore, the composite effect on flexural behavior characteristics when GO and PVA fibers are incorporated was discussed. RESULTS : For the PVA fiber-reinforced cement mortar mixture, the incorporation of 0.05% GO increased the crack initiation load by up to 23%, and the maximum resistive load after cracking by up to 24%. Moreover, introducing GO into the PVA fiber-reinforced mixture increased the flexural strain just before cracking by approximately 30 to 50%, while the maximum resistive load after cracking exhibited similar strain levels with or without GO incorporation. Therefore, under flexural behavior, the integration of GO might delay crack initiation by increasing the strain concurrent with the rise in flexural stress before crack occurrence. It also seems to contribute to reducing crack expansion by synergistically interacting with PVA fibers after crack occurrence. CONCLUSIONS : It was experimentally examined that the flexural strength of PVA fiber reinforced cement mortar is improved by incorporating GO. Moreover, GO enhances resistance of crack occurrance and reduces crack propagation in combination with PVA fibers. This study suggests that simultaneous incorporation of GO and PVA fibers can synergistically improve the performance of cement composites.

An hydrogen adsorption study on graphene-based surfaces consisting of nitrogen-doped graphene and core–shell type catalysts of initially Pd13 , Pt13 , PdPt12 and PtPd12 core–shells, is presented in this work. Density functional theory results indicate correlation between charge transfer and structural properties, hydrogen adsorption energies, magnetic behavior and electronic properties. Reduction of hydrogen, together with higher values of charge transfer was observed for high hydrogen dissociation, compared to the case of non-hydrogen dissociation. In some cases, these values may be almost an order of magnitude larger than that of non-hydrogen dissociation. Hydrogen dissociation is also related to oxidation of the surface and correlates with a non-core shell-type structure, high adsorption energies and low magnetic moments, in general. Besides, core shell-type structure dramatically changes the magnetic and electronic properties of charge transfer. The results obtained in this work may provide important information for storing hydrogen.

Graphene-derived materials are an excellent electrode for electrochemical detection of heavy metals. In this study, a MnO2/ graphene supported on Ni foam electrode was prepared via ultrasonic impregnation and electrochemical deposition. The resulting electrode was used to detect Pb(II) in the aquatic environment. The graphene and MnO2 deposited on the Ni foam not only improved active surface area, but also promoted the electron transfer. The electrochemical performance towards Pb(II) was evaluated by cyclic voltammetry (CV) and square wave anodic stripping voltammetry (SWASV). The prepared electrode exhibited lower limit of detection (LOD, 0.2 μM (S/N = 3)) and good sensitivity (59.9 μAμM−1) for Pb(II) detection. Moreover, the prepared electrodes showed good stability and reproducibility. This excellent performance can be attributed to the strong adhesion force between graphene and MnO2, which provides compact structures for the enhancement of the mechanical stability. Thus, these combined results provide some technical considerations and scientific insights for the detection of heavy metal ions using composite electrodes.

Nanofillers, by virtue of their minute size, when incorporated inside a matrix, have the capability to enhance the physical parameters of the complex matrix. Graphene, the wonder material of the twenty-first century, has established itself in the field of nanofillers. However, it still has yet to find its way into the mining industry. This review paper focuses on a novel way of attaining sustainability in mining methodology using graphene as a nanofiller. The implementations can be subdivided into three categories based on their impact—economic, environment, and safety. To achieve economic welfare in mine methodology; Graphene is used to enhance the productivity of machinery. Electric-Heavy Earth Moving Machinery using LiFePO4/Graphene hybrid cathode battery is not only an ideal replacement to fossil-powered vehicles considering the contribution of environmental strain but also a more-efficient model than Electric-Heavy Earth Moving Machinery using conventional Lithium Ion Phosphate Battery batteries. Heavy Earth Moving Machinery having tires of Styrene-Butadiene Rubber/Graphene composite would have better efficacy and longer life cycle than the conventional ones. Graphene derivative Magnetic Graphene Oxide is used to achieve environmental welfare by its implication as an additive in the effluent treatment plant for its capability of removing heavy metal ions and negative-strain bacteria from the mine water. To improve the safety standards of the mine workers, graphene and its derivatives have environmental implications to constitute a safer surrounding concerning precarious situations due to the unpredictable behavior of geomaterials. Graphene can assist in constituting a more economical and reliable slope model as incorporating graphene induces restructuration and improvement in strength parameters. This enables a miner to extract more minerals in tranquility from the resources as there is an increase in compaction and shear strength. A combination of a graphene sheet and auxetic graphene foam can be placed over the blast holes to not only restrict the trajectory of the fly rocks but also attenuate some part of the explosive energy. The objective of this coagulation is to upgrade the traditional practice by replacing the conventional products, and the effect is observed in the form of achieving sustainability in the mine.

Graphene oxide/Iron III oxide (GO: Fe2O3) nanocomposites (NCs) have been topical in recent times owing to the enhanced properties they exhibit. GO acting as a graphene derivative has demonstrated superior features as obtainable in a graphene sheet. Furthermore, the attachment of oxygen functional groups at its basal and edge planes of graphene has allowed for easy metal/oxide functionalization for improved properties harvesting. Fe2O3 nanoparticles (NPs) on the other hand have polymorphic property enabling the degeneracy of Fe2O3 in different phases, thereby resulting in different physical and crystalline properties when used to functionalize GO. The properties of GO: Fe2O3 have been applied to supercapacitor energy harvesting, Li-ion batteries, and biomedicine. The enhanced properties are attributed to the adsorption and electronic structure properties of Fe atoms. In this review, the various synthesis used in the preparation of reduced/graphene oxide: Fe2O3 is discussed. As indicated in the considered literature, the XPS analysis suggests electronic bond interactions between C–C, C–O, C–Fe and Fe–C. The available report on UPS measurements further suggests the formation of mixed states emanating from  and  bonds. The discussed reports further suggest that the various applications based on the harvesting of electronic, electrical, and magnetic properties are due to the ionic and exchange interactions between the different orbital states of carbon, oxygen and iron. The challenges and future prospects of the synthesis and application of GO/Fe2O3 are examined. Graphical abstract showing the process of exfoliation, reduction and functionalization of graphite to produce reduced graphene oxide (rGO).