A material that can serve in almost every field of human life at very low cost with high results is no other than “graphene”. The multifunctional properties of graphene have made it a very ...interesting topic of research among researchers. Since its discovery in the last decade of the last century, scientists continue to disclose the amazing properties of graphene day by day. By last year, the number of publications on graphene applications had reached many thousands per year, which is a record absolutely. The main objectives of this review were to provide an eye-catching view of graphene properties discovered in the last few years. This review aims to report some “green synthesis” methods for synthesizing graphene from low cost/no cost materials having no side effects of any kind. Fabrication of graphene to produce composite materials is another milestone that is discussed in this review, giving recent examples. “Graphene membranes” can serve not only for the separation of different gases but find a main use in the supply of safe drinking water to all countries. “Graphene energy” can be utilized for the production of graphene batteries with much better charging capacity than the traditionally used lithium batteries. Graphene superconductors and magnets exhibit better performance than previously used materials for these purposes. Graphene inks can bring about a revolution in the field of printed electronics. A very recent development is graphene clothing and shoes. Graphene glasses, paints, rubber bands and disease detectors are among other graphene-based materials developed for human use. This review percolates recent advancements in graphene and its applications, which have brought about positive and revolutionary change in different fields of human welfare.
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Constructing a composite photocatalyst with distinct structures is an efficient mean to improve the charge transfer/separation ability and increase the active sites of TiO.sub.2-based photocatalyst. ...For the first time, we synthesized a TiO.sub.2 nanobelts/MoS.sub.2 quantum dots (QDs)/rGO (TiO.sub.2/MoS.sub.2/rGO) ternary photocatalyst via a facile one-step photodeposition method. TiO.sub.2 nanobelts provide photoinduced electrons that facilitate formation and self-assembling of MoS.sub.2 QDs and rGO. The TiO.sub.2/MoS.sub.2/rGO ternary composites present two different structures: One is a composite structure of graphene-wrapped TiO.sub.2 nanobelt/MoS.sub.2 QDs, and the other is composed of graphene-supported TiO.sub.2 nanobelts and MoS.sub.2 QDs. Both configurations facilitate the separation of photoinduced electron-hole pairs and charge transfer. The heterostructure of zero-dimensional MoS.sub.2 QDs, one-dimensional TiO.sub.2 nanobelts, and two-dimensional graphenes endows the photocatalyst with the integrated advantages of these nanomaterials with different dimensions and provides a substantial number of active sites for photocatalytic reactions. The TiO.sub.2/MoS.sub.2/rGO ternary composites degraded rhodamine B at a rate constant that is 8.72 times faster than that of pristine TiO.sub.2 nanobelt. This study presents a facile method to synthesize an inexpensive multi-composite photocatalyst with high efficiency for renewable energy production and environmental treatments.
Based on the calculation using first-principles, we discussed adjustment for electronic properties of the GaN/graphene/WS.sub.2 trilayer vdW heterostructure by doping and biaxial strain. Mg or Se ...doping can regulate the band gap of the GaN/graphene/WS.sub.2 trilayer vdW heterostructure and achieve p-type or n-type dopant in graphene and the trilayer heterostructure system. Band gap decreases with the increase in positive strain, and a p-type Schottky barrier is always maintained. As the negative strain increases, the band gap reaches its maximum at epsilon = - 3% and then gradually decreases. And after |epsilon| greater than or equal to | - 5|%, it changes to an indirect band gap. When |epsilon| greater than or equal to | - 7|%, the Schottky contact type changes from p-type to n-type. Electrons are transferred from GaN layer to graphene and WS.sub.2 layer, and transfer increases with the increase in strain from negative to positive. More electrons are transferred to WS.sub.2 with positive strain, and more electrons are transferred to graphene with negative strain. The results will provide valuable information for the design of trilayer Schottky devices.
Solving energy and environmental problems through solar‐driven photocatalysis is an attractive and challenging topic. Hence, various types of photocatalysts have been developed successively to ...address the demands of photocatalysis. Graphene‐based materials have elicited considerable attention since the discovery of graphene. As a derivative of graphene, nitrogen‐doped graphene (NG) particularly stands out. Nitrogen atoms can break the undifferentiated structure of graphene and open the bandgap while endowing graphene with an uneven electron density distribution. Therefore, NG retains nearly all the advantages of original graphene and is equipped with several novel properties, ensuring infinite possibilities for NG‐based photocatalysis. This review introduces the atomic and band structures of NG, summarizes in situ and ex situ synthesis methods, highlights the mechanism and advantages of NG in photocatalysis, and outlines its applications in different photocatalysis directions (primarily hydrogen production, CO2 reduction, pollutant degradation, and as photoactive ingredient). Lastly, the central challenges and possible improvements of NG‐based photocatalysis in the future are presented. This study is expected to learn from the past and achieve progress toward the future for NG‐based photocatalysis.
Nitrogen‐doped graphene plays a significant role in photocatalysis. Rational design, preparation, and understanding the mechanism of N‐doped graphene‐based photocatalysts provides a new opportunity to further enhance the photocatalytic performance. The research progress, atomic and band structures, photocatalytic mechanism, synthesis strategy, unique advantages, and wide application of N‐doped graphene in photocatalysis are highlighted.
Agsub.2Te is a novel topological insulator system and a new candidate for plasmon resonance due to the existence of a Dirac cone in the low-energy region. Although the optical response spectrum of ...Agsub.2Te has been studied by theoretical and experimental methods, the plasmon resonance and stability of Co-doped Agsub.2Te remain elusive. Here, we theoretically report a new unconventional UV plasmon mode and its stability in Co-doped Agsub.2Te. Through density functional theory (DFT), we identify a deep UV plasmon mode within 15–40 eV, which results from the enhanced inter-band transition in this range. The deep UV plasmon is important for detection and lithography, but they have previously been difficult to obtain with traditional plasmon materials such as noble metals and graphene, while most of which only support plasmons in the visible and infrared spectra. Furthermore, we should highlight that the high-energy dielectric function is almost invariant under different doping amounts, indicating that the UV plasmon of Agsub.2Te is robust under Co doping. Our results predict a spectrum window of a robust deep UV plasmon mode for Agsub.2Te-related material systems.
A facile, ultrasonic wave-assisted one pot hydrothermal method has been developed to fabricate reduced graphene oxide/bismuth vanadate/titanium oxide (RGO/BiVO.sub.4/TiO.sub.2) ternary ...nanocomposites. By utilizing graphene oxide (GO) as multifunctional structure, RGO/BiVO.sub.4/TiO.sub.2 (GBT) with diverse percentage composition possessing varying band gap energies is obtained. XRD and Raman spectroscopy evince formation of tetragonal and monoclinic phases of BiVO.sub.4. The band gap energies of the components of the composite were determined by applying modified Kubelka-Munk function on UV-Vis DRS data. Tuning of band gap energy of the BiVO.sub.4 and TiO.sub.2 were simultaneously achieved by modifying the concentrations of GO and TiO.sub.2 during synthesis. The GBT exhibited enhanced photocatalytic degradation of methylene blue (MB) under visible light irradiation. The relative photocatalytic activity rates of the composites in GBT series are in agreement with the photoluminescence data. The mechanism behind the activity suggests GO acting as an electron trapper and TiO.sub.2 behaving as an efficient mediating co-catalyst. The band gap energy tuning led to reduction in time needed for complete MB degradation from 40 min with RGO/BiVO.sub.4 to 10 min with the ternary composite GBT. It is expected that the work would encourage new vistas to engineer different combinations of graphene based ternary composites which might lead to potential applications guided by band gap tuning.
Graphene, a single, one-atom-thick sheet of carbon atoms arranged in a honeycomb lattice and the two-dimensional building block for carbon materials, has attracted great interest for a wide range of ...applications. Due to its superior properties such as thermo-electric conduction, surface area and mechanical strength, graphene materials have inspired huge interest in sensing of various chemical species. In this timely review, we discuss the recent advancement in the field of graphene based gas sensors with emphasis on the use of modified graphene materials. Further, insights of theoretical and experimental aspects associated with such systems are also discussed with significance on the sensitivity and selectivity of graphene towards various gas molecules. The first section introduces graphene, its synthesis methods and its physico-chemical properties. The second part focuses on the theoretical approaches that discuss the structural improvisations of graphene for its effective use as gas sensing materials. The third section discusses the applications of pristine and modified graphene materials in gas sensing applications. Various graphene modification methods are discussed including using dopants and defects, decoration with metal/metal oxide nanoparticles, and functionalization with polymers. Finally, a discussion on the future challenges and perspectives of this enticing field of graphene sensors for gas detection is provided.
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