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.

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.

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).

Poor mechanical properties and bacterial infection are the main problems faced by dental restorative resins in clinical use. In this study, graphene quantum dots (GQDs) grafted with imidazole groups and mesoporous silica (MSN) are co-filled in a dental resin to impart excellent antimicrobial activity and mechanical properties to the dental resin. The higher specific surface area of GQDs and MSN results in an increased contact area with the resin matrix, which enhances the strength of the dental composite resin. The introduction of GQDs significantly improves the antimicrobial activity of the resin. The inhibition efficiency of the composite resin against Streptococcus mutans reached 99.9% with the addition of GQDs at only 0.2 wt.%. When MSN and GQDs are co-filled, MSN interferes with the release of GQDs, thus reducing the antimicrobial activity of the dental resin but improving the cyto-compatibility. By reasonably adjusting the amount of GQDs and MSN, the dental composite resin can exhibit excellent antimicrobial properties, mechanical properties and cyto-compatibility at the same time.

The physical and antibacterial properties of ophthalmic lenses fabricated by copolymerization with hydrogel monomers using two types of graphene were measured, and their usability as contact lens materials was analyzed. For polymerization, silicone monomers, including SID-OH, 3-(methacryloxy)propyl tris(trimethylsiloxy)silane, and decamethylcyclopentasiloxane, were used, and N,N-dimethylacetamide, ethylene glycol dimethacrylate as a crosslinking agent, and azobisisobutyronitrile as an initiator were added. Also, graphene oxide nanoparticle (GON) and graphene nanoplate (GNP) were used as an additive, and the physical properties of the lenses fabricated after copolymerization were evaluated. The fabricated lenses satisfied the basic physical properties of general hydrogel contact lenses and showed the characteristics of lenses with high water content, and the disadvantage of very weak durability, due to low tensile strength. However, it was confirmed that the tensile strength and antibacterial properties were greatly improved by adding GON and GNP. With GON, the oxygen permeability and refractive index of the fabricated lenses were slightly improved. Therefore, it was determined that the graphene materials used in this study can be used in various ways as a contact lens material.

The effect of the laser ablation duration of reduced graphene oxide sheets on their optical properties was studied. After 30 min of ablation, the average lateral size of reduced graphene oxide sheets decreases from 347.4 ± 86.5 nm to 98.8 ± 36.0. The sizes of almost all particles are in the range up to 100 nm, which was confirmed by transmission electron microscopy and dynamic light scattering data. The FTIR spectroscopy data showed that after ablation the intensity of the bands associated with O–H, C–OH and C=O vibrations were noticeably decreased. The optical density and the fluorescence intensity of reduced graphene oxide also depend on the ablation time. After ablation, the reduced graphene oxide fluorescence intensity increased 2–3 times. The fluorescence lifetime decreases both for the first (from 1.36 ns to 0.71 ns) and second (from 6.03 to 3.66 ns) components. A broad band was recorded in the long-lived luminescence spectrum. The long-lived luminescence intensity is higher on 80% for the samples after 30 min of ablation compared to the unablated sample. It was assumed that during laser ablation of reduced graphene oxide a change in the ratio between oxidized and sp2- hybridized carbon occurs. This opens up possibilities for controlling the optical properties of reduced graphene oxide.

그래핀옥사이드는 우수한 물리적 특성 및 가공성으로 멤브레인 소재로 각광받고 있다. 특히, 이론적 예측과 실험 적인 접근을 통해 그래핀옥사이드의 원자 수준의 얇은 두께, 뛰어난 기계적 강도, 높은 수준의 내화학성, 기공 생성이 가능한 2차원 구조 또는 기체 확산 유로 생성이 가능한 적층구조 등 멤브레인 소재로서 매우 유리한 특성들을 보유하고 있음이 밝혀 졌다. 또한 그래핀옥사이드에서의 분자 투과 거동은 적층된 그래핀옥사이드 사이의 채널 크기에 따라 영향을 받는다는 것이 발견되었다. 그 후, 이러한 특성을 응용하여 그래핀옥사이드를 멤브레인 소재로 활용하기 위해 많은 연구가 집중적으로 진행 되고 있다. 본 총설에서는 그래핀옥사이드의 고유 특성을 기반으로 멤브레인 분야로의 응용 가능성에 대하여 논하고자 한다.

Graphene, a new material with various advantageous properties, has been actively used in various fields in recent years. Applications of graphene oxide are increasing in combination with other materials due to the different properties of graphene oxide, depending on the number of single and multiple layers of graphene. In this study, single-layer graphene oxide and multi-layer graphene oxide are spray coated on polystyrene, and the physicochemical properties of the coated surfaces are characterized using SEM, Raman spectroscopy, AFM, UV-Vis spectrophotometry, and contact angle measurements. In singlelayer graphene oxide, particles of 20 μm are observed, whereas a 2D peak is less often observed, and the difference in surface height increases according to the amount of graphene oxide. Adhesion increases with an increase in graphene oxide up to 0.375 mg, but decreases at 0.75 mg. In multi-layer graphene oxide, particles of 5 μm are observed, as well as a 2D peak. According to the amount of graphene oxide, the height difference of the surface increases and the adhesive strength decreases. Both materials are hydrophilic, but single-layer graphene oxide has a hydrophilicity higher than that of multi-layer graphene oxide. We believe that multi-layer graphene oxide and single-layer graphene oxide can be implemented based on the characteristics that make them suitable for application.

The behaviour of semiconducting graphene quantum dots (GQDs), as good candidates for various biological carrier applications and optical sensing, are necessary to be studied under various conditions. In this study, GQD models were generated according to the geometrical and chemical specifications of synthesized GQDs to achieve the most realistic models. The GQDs’ bandgap and distribution of their electric surface charges were obtained using computational chemistry method. Finite element analysis was conducted on pristine and defective GQDs to study Young and shear modulus. Buckling load and resonant frequency modes of GQDs were calculated analytically and demonstrated under various boundary conditions. The dimension of GQDs has an average of 3.5 ± 0.4 nm, with an interlayer spacing of 0.36–0.40 nm. Computational chemistry studies revealed the characteristic zero-band-gap nature of graphene. Finite element studies showed that the by introducing the inevitable dislocation, mono atom vacancy and Stone–Wales defects to GQD models, their mechanical properties reduces to approach data from experimental investigations, whereas an increase in the number of layers does not influence the obtained results significantly.

Compared to carbon nanotubes (CNTs), graphene possesses high strength due to wrinkled surface texture caused by a high density of surface defects which benefits more contact with the polymer material than a rolled-up CNT. In the present review, we have discussed and compared the various properties of CNTs (1-D) and graphene (2-D) obtained in experimental results. The effects of covalent and non-covalent functionalization of CNTs and graphene on the properties of its composites have also been reviewed and compared. A comparative analysis has been carried out between CNTs and graphene-reinforced polymer composites. Furthermore, the synergetic effects of CNTs and graphene hybrid nanofiller on the mechanical properties of polymer composites have also been briefly discussed. Finally, this review concludes with the potential application and future challenges are discussed with regards to filler and their polymer composites.

Herein, we report significantly enhanced mechanical properties and thermal conductivity of polyimide (PI) by incorporating a small amount (0.01 wt %) of individualized boron-doped high-quality graphene as a filler. The boron-doped expandable graphite (B-EG) was synthesized by mixing boric acid ( H3BO4) with expandable graphite (EG) and thermally treating the mixture at 2450 °C for 30 min using a graphite furnace in an argon atmosphere. The boron-doped graphene (B-g) was prepared by the solution-phase exfoliation of B-EG with an ultrasonication process, which is a method to obtain individualized graphene as well as few-layer graphene. The PI nanocomposites were prepared using the obtained graphene. The PI nanocomposites synthesized with high-quality B-graphene (B-g) showed enhanced mechanical properties and thermal conductivity compared to those of pure PI due to the doping effects and strong interfacial interactions between graphene and the PI matrix.

Low cost and scalable manufacturing of highly doped cellulose for enhanced multifunctional applications is still an issue. In this work, eco-friendly nanocomposites were fabricated by incorporating regenerated cellulose (RC) of 10, 30, and 50 wt% into an exfoliated graphene nanoplatelets (GNPs), resulting in the intercalation of GnPs. The thermal and electrical properties of hybrid nanocomposites were investigated. The structural property was conducted through scanning electron microscope and X-ray diffraction analyses. Strong frequency-dependent dielectric response was found due to the change of the permittivity and the loss tangent of nanocomposites by different content of RC, which is associated with the polarizations behavior. Non-elastic relaxation at the GNPs–RC chains interfacial areas in an alternating field was identified as the main cause of polarization losses among others. Detailed ferroelectric measurements provided the evidence of the ideal resistive behavior of the nanocomposites, which are confirmed by the resistivity measurements along the out-of-plane direction of the nanocomposite sheets.

For the automotive application, graphene-glass composites were fabricated using E-glass fiber(GF) coated with various types of graphene nanosheets deposited by electrophoretic deposition. Graphene oxide(GO) was first synthesized using a modified Hummer’s method and its subsequent ultrasonic treatment in deionized water produced a stable stop of the GO. Glass fiber was immersed in water and GO suspension near the copper anode. The potential applied between the electrodes caused the GO to move toward the anode. In addition, the GO coated yarn was exposed to hydrazine hydrate at 100℃ to obtain a reduced graphene oxide(rGO) coating yarn. Both GO and rGO coated glass fiber yarns were used to fabricate unidirectional epoxy-based multi-scale composites by passive lay-up. The presence of a conductive rGO coating on glass fiber improves both the electrical conductivity and thermal conductivity of the composite. In addition, rGO-based epoxy-glass composites have been used to improve the dielectric constant, providing the option of using this structure for electromagnetic interference shielding.

Membrane fabrication is a critical area that hampers forward osmosis (FO) technology from industrialization. Herein, electrospun poly(vinyl alcohol) (PVA) nanofiber (NF) was used as a support layer for thin film composite (TFC) FO membrane. The PVA NF was incorporated with sulfonated graphene oxide (sGO). The oxygenous-rich sGO enhanced the hydrophilicity and mechanical strength of PVA NF as revealed by contact angle and tensile strength measurements, and pure water flux. On this support, the active polyamide layer was formed through interfacial polymerization. Meanwhile, FO performance of sGO/PVA TFC membrane is currently being evaluated. This work was supported by NRF of Korea funded by the Ministry of Science and ICT (2016R1A2B1009221 and 2017R1A2B2002109) and Ministry of Education (2009-0093816 and 22A20130012051 (BK21Plus)).