In the new era of modern flexible and bendable technology, graphene-based materials have attracted great attention. The excellent electrical, mechanical, and optical properties of graphene as well as the ease of functionalization of its derivates have enabled graphene to become an attractive candidate for the construction of flexible devices. This paper provides a comprehensive review about the most recent progress in the synthesis and applications of graphene-based composites. Composite materials based on graphene, graphene oxide (GO), and reduced graphene oxide (rGO), as well as conducting polymers, metal matrices, carbon–carbon matrices, and natural fibers have potential application in energy-harvesting systems, clean-energy storage devices, and wearable and portable electronics owing to their superior mechanical strength, conductivity, and extraordinary thermal stability. Additionally, the difficulties and challenges in the current development of graphene are summarized and indicated. This review provides a comprehensive and useful database for further innovation of graphene-based composite materials.

Transport measurements have revealed several exotic electronic properties of graphene. The possibility to influence the electronic structure and hence control the conductivity by adsorption or doping with adatoms is crucial in view of electronics applications. Here, we show that in contrast to expectation, the conductivity of graphene increases with increasing concentration of vacancy defects, by more than one order of magnitude. We obtain a pronounced enhancement of the conductivity after insertion of defects by both quantum mechanical transport calculations as well as experimental studies of carbon nano-sheets. Our finding is attributed to the defect induced mid-gap states, which create a region exhibiting metallic behaviour around the vacancy defects. The modification of the conductivity of graphene by the implementation of stable defects is crucial for the creation of electronic junctions in graphene-based electronics devices.

To meet the growing demand in energy, great efforts have been devoted to improving the performances of energy–storages. Graphene, a remarkable two-dimensional (2D) material, holds immense potential for improving energy–storage performance owing to its exceptional properties, such as a large-specific surface area, remarkable thermal conductivity, excellent mechanical strength, and high-electronic mobility. This review provides a comprehensive summary of recent research advancements in the application of graphene for energy–storage. Initially, the fundamental properties of graphene are introduced. Subsequently, the latest developments in graphene-based energy–storage, encompassing lithium-ion batteries, sodium-ion batteries, supercapacitors, potassium-ion batteries and aluminum-ion batteries, are summarized. Finally, the challenges associated with graphene-based energy–storage applications are discussed, and the development prospects for this field are outlined.

Graphene is a two-dimensional material with a capability of gas sensing, which is here shown to be drastically improved by inducing gentle disorder in the lattice. We report that by using a focused ion beam technique, controlled disorder can be introduced into the graphene structure through Ga(+) ion irradiation. This disorder leads to an increase in the electrical response of graphene to NO(2) gas molecules by a factor of three in an ambient environment (air). Ab initio density functional calculations indicate that NO(2) molecules bind strongly to Stone-Wales defects, where they modify electronic states close to the Fermi level, which in turn influence the transport properties. The demonstrated gas sensor, utilizing structurally defected graphene, shows faster response, higher conductivity changes and thus higher sensitivity to NO(2) as compared to pristine graphene.

The past one and a half decades have witnessed the tremendous progress of two-dimensional (2D) crystals, including graphene, transition-metal dichalcogenides, black phosphorus, MXenes, hexagonal boron nitride, etc., in a variety of fields. The key to their success is their unique structural, electrical, mechanical and optical properties. Herein, this paper gives a comprehensive summary on the recent advances in 2D materials for optoelectronic approaches with the emphasis on the morphology and structure, optical properties, synthesis methods, as well as detailed optoelectronic applications. Additionally, the challenges and perspectives in the current development of 2D materials are also summarized and indicated. Therefore, this review can provide a reference for further explorations and innovations of 2D material-based optoelectronics devices.

Multiferroic materials, showing simultaneous ferroelectric and ferromagnetic orders, are considered to be promising candidates for future data storage technology however, the multiferroic phenomenon in two-dimensional (2D) materials is rarely observed. We report a simple approach to observe frequency-dependent ferroelectricity and multiferroicity in 2D Ti₃C₂T_x MXene film at room-temperature. To study the frequency and poling effect on ferroelectricity, we performed electric polarization vs. electric field (P-E) measurement at different frequencies, measured under zero and non-zero static magnetic fields. The results not only indicate a clear frequency dependence of electric domains owing to varying time relaxation during reversal dynamic but also showed magnetic field control of electric polarization thus, confirmed the presence of strong magneto-electric (ME) coupling at room-temperature. The existence of ME coupling was attributed to the coupling between disordered electric dipoles with local spin moments as well reduced dielectric loss after heat-treatment. Moreover, the ferroelectric Ti₃C₂T_x MXene film was employed as an active layer within the resistive data storage device that showed a stable switching behavior along with improved on/off ratio in comparison to non-ferroelectric Ti₃C₂T_x active layer. The unique multiferroic behavior along with ferroelectric-tuned data storage devices reported here, will help understand the intrinsic nature of 2D materials and will advance the 2D ferroelectric data storage industry.