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Graphene Based Materials: Past, Present and Future
... The graphene layers are etched away from the transition metal and transferred to a new substrate. While graphene is made by a thermal CVD method in a resistive-heater furnace, when plasma is added to this process, it is called plasma-enhanced CVD (Singh et al., 2011;Tsai et al., 2020). ...
... The amount of time and heat necessary to melt graphite into its many layers varies. The preparation of monolayer or few-layer graphene on SiC via epitaxial growth has been widely documented for use in devices that emit light and high-frequency circuits (Singh et al., 2011;Zhou et al., 2019). Graphene is typically grown epitaxially on a SiC substrate, which involves the breakdown of the SiC and the formation of graphene layers. ...
... The attached PMMA layer was subsequently vaporized using acetone. The breadth and number of layers within the precursor material determine the total amount of layers in GNR (Jiao et al., 2009;Singh et al., 2011). Sridhar et al. released a green synthesis approach for producing graphene using microwaves, as shown in Fig. 3.10 (Sridhar et al., 2010). ...
Graphene-based electroconductive textiles have garnered noteworthy consideration in recent years owing to their exceptional features and latent applications. These textiles combine the remarkable characteristics of graphene, for instance, thermal conductivity, higher electrical, and mechanical strength, as well as lightweight nature, with the flexibility and versatility of textile materials. The processing and preparation of graphene-based electroconductive textiles play a crucial role in ensuring their functionality and performance. This chapter provides a comprehensive summary of the numerous processing techniques and preparation methods employed to incorporate graphene into textile substrates. Initially, it explores different synthesis routes for graphene and discusses the impact of treatment constraints and substrate categories on the functional attributes of these textile substrates. Subsequently, the chapter also discusses the deposition of graphene techniques like vacuum filtration deposition, brush coating, printing, wet transfer, and dip coating. Additionally, it explores the graphene oxide reduction process for the development of graphene-based conductive textiles. Finally, the effect of graphene doping in terms of its impact on electrical resistivity and graphene loadings is analyzed. On the whole, the chapter provides the processing and preparation aspects of electroconductive textiles, so researchers and scholars can further explore and optimize their potential in various technological advancements.
... Carbon-based nanomaterials, such as carbon nanotubes, graphene-family materials, or nanocarbon black, feature outstanding properties, thus promising a wide range of remarkable functionalities. 2 Among others, the unprecedented electrical properties 3 of carbon-based nanomaterials pave the way to next-generation multifunctional cement composites. 4,5 Numerous exciting examples of cement-based and geopolymer nanocomposites have blossomed over the last decades, showing their great potential for self-sensing applications in civil engineering. ...
... Indeed, graphene, defined as a 2D honey-comb lattice monolayer of carbon, 3 has emerged as an exciting material possessing numerous outstanding properties. 2 The methods of graphene synthesis have been extensively studied over the past years. Noteworthy, the synthesis methods differ significantly in terms of the morphology, composition (oxygen level), and properties of the resulting material, costs, yield, and the upscaling potential. ...
... The most common synthesis methods are: mechanical exfoliation, associated mainly with the "scotch tape" method, chemical vapor deposition (CVD) methods, such as thermal CVD, plasma-enhanced CVD, or hot/cold wall CVD, liquid-phase exfoliation, reduction of graphene oxide (GO), synthesis on SiC substrates, and un-zipping of CNTs. 2 Within the field of self-sensing cement composites, a great deal of attention was gained initially by so-called graphene nanoplatelets (GNPs) due to their relatively low cost. Fundamentally, GNPs are considered a hybrid between graphite and graphene since they consist of monolayer and multilayer graphene as well as nanostructured graphite. ...
In the late 1980s, research began on the functionalization of concrete in the context of self‐monitoring. For this purpose, conductive functional fillers placed in a cement matrix were used. The aim of this article is to present an overview of historical solutions, and the latest trends related to the use of conductive materials, ranging from the detection of structural failures to continuous monitoring of deformations. The article presents a critical review of self‐monitoring methods being developed, including concrete with carbon fibers and nanofibers or conductive carbon nanomaterials (such as carbon nanotubes, graphene‐family materials and nanocarbon black), cementitious, polymeric, and AAM (Alkali Activated Materials) repair materials with crack detection features, FRP‐based smart‐strengthening solutions, and monitoring reinforcement rebars. Measurement methods and their development toward in situ applications are also discussed. The paper highlights the major challenges within the field as well as future development paths for the use of multifunctional concrete composites in civil engineering. In particular, the article indicates directions for further research on biomimetic solutions, including those in the areas of monitoring of other non‐mechanical parameters, using functional materials for electrochemical protection of structures, wireless communication, integration with the BIM environment, energy harvesting, actuation, and others.
... RGO can provide superior specific surface area (BET surface area: 422.69-499.85 m 2 /g); furthermore its 2D structure can offer high thermal conductivity (~3000 W/mK) [6,7]. Additionally, it could combust proficiently with the release of nanoblack carbon as black body emitter [3,[8][9][10]. ...
... In this study colloidal Fe 2 O 3 particles of 5 nm particle size were developed by hydrothermal synthesis. In the mean time, RGO particles were developed through the reduction of GO [6,26,27]. Synergism between RGO and Fe 2 O 3 was investigated in an attempt to developed decoy flare with superior spectral performance in terms of average intensity and Ɵ value. Thermal signatures of developed flares were measured using (FT-MIR 1-6 µm) spectrophotometer. ...
Infrared-guided missiles caused 90% aircraft damage. Infrared decoy flares are effective counter measure against infrared missiles. Decoy flare thermal signature depends mainly on black body emission of carbonaceous combustion products. Thermite particles can offer substantial heat output to promote black body emission. Reduced graphene oxide (RGO) is a promising material for advanced infrared decoy flares. RGO could act as ideal black-body emitter with superior thermal properties and high interfacial surface area. This study is dedicated to investigate novel synergism between Fe 2 O 3 and RGO; Fe 2 O 3 NPs of 3.56 nm were fabricated using hydrothermal synthesis technique. RGO nano-sheets of 10 µm dimensions and 10 nm thickness were developed via the reduction of graphene oxide, developed by Hummer ̓ method. Complete reduction of GO to RGO was confirmed by Raman spectroscopy. Amorphous nano-sheets structure was observed using TEM; XRD diffractogram demonstrated tiny characteristic broad peak for amorphous RGO. Decoy flare formulation based on Fe 2 O 3 , RGO, reactive metal fuel (Mg), and fluorocarbon polymer (teflon) were developed. Thermal signature was evaluated using Arc-Optics IR spectrometer (1-6 µm). Multi-component MTV nanocomposite flare based on 6 wt % RGO and 2 wt % Fe 2 O 3 demonstrated superior spectral and radiometric performance. It offered an increase in average intensity by 130% to reference MTV formulation; additionally it offered superior relative intensity Ɵ value of 0.76. While RGO could act as novel black body emitter; thermite reaction between Fe 2 O 3 NPs and surplus magnesium fuel could provide substantial heat output; that could promote RGO black body emission.
... Recently, it has gained significant attention as a nanofiller due of its extraordinary features, including its superb modulus and astonishingly high electrical and thermal conductivities. The unique characteristics inherent in the single-layer structure of these materials, surpassing those of existing carbon nanomaterials, have paved the way for the development of ultra-lightweight, low-cost advanced composite (Kuilla et al. 2010;Singh et al. 2011). However, similar to other nanomaterials, the dispersion state of graphene plays a vital role in determining the physical properties of the elastomers. ...
... This method, as extensively explained by Kuilla et al. (2010), involves oxidation of graphite, followed by exfoliation and reduction to obtain graphene. However, this procedure, designed to produce significant quantities of monolayers, creates structural flaws that interfere with the electrical structure of graphene, as noted by Singh et al. (2011). Raman spectroscopy, a very effective tool for analyzing carbon-based materials, definitively detects the existence of defects (Bokobza et al. 2015(Bokobza et al. , 2017Stankovich et al. 2007;Eda et al. 2008). ...
BC is an incredibly robust material, with an estimated modulus of over 100 GPa and a strength exceeding 1.5 GPa. It is truly one of nature's strongest creations. Research has shown the effectiveness of using BC as a nano-additive in polymeric materials leading to the formation of lightweight and superior strength nanocomposites at high fiber fractions of BC in the matrices. This chapter explores the various uses of BC in polymers and rubber nanocomposites. These materials consist of nanocomposites that are transparent to light and composites that have been reinforced with BC and natural fibres, creating a hierarchical structure. It covers the synthesis, properties, and applications of these advanced materials. Emphasis is placed on the synergy between BC and rubber matrices, the techniques employed for their fabrication, and their enhanced mechanical, thermal, and biocompatible properties. The potential applications of BC/rubber composites in various industries, including biomedical, automotive, and electronics, are discussed. The authors have explored the application of BC in various cellulosic and biomimetic composites. This chapter also highlights then the usage of BC in the production of BC/rubber nanocomposites.
... Factors such as defects and heteroatoms, the number of stacked sheets (mono, bi-, tri-, or multi-layers), and the lateral extension of the graphene structure are determined by the chosen synthesis route. [15] These structures can be synthesized using top-down approaches [38,39] (such as, sonochemical, [40,41] electrochemical exfoliation, [42,43] mechanical or mechanochemical exfoliation of graphite [28,34,44] ) and bottom-up approaches [38,39] (e. g., chemical vapor deposition -CVD, [5,45,46] electrical arc, [47][48][49] epitaxial growth on SiC, [50,51] carbon nanotube unzipping, and chemical synthesis from molecular precursors [4,15,33,35,36] ). Each of these approaches has its merits and limitations. ...
... Factors such as defects and heteroatoms, the number of stacked sheets (mono, bi-, tri-, or multi-layers), and the lateral extension of the graphene structure are determined by the chosen synthesis route. [15] These structures can be synthesized using top-down approaches [38,39] (such as, sonochemical, [40,41] electrochemical exfoliation, [42,43] mechanical or mechanochemical exfoliation of graphite [28,34,44] ) and bottom-up approaches [38,39] (e. g., chemical vapor deposition -CVD, [5,45,46] electrical arc, [47][48][49] epitaxial growth on SiC, [50,51] carbon nanotube unzipping, and chemical synthesis from molecular precursors [4,15,33,35,36] ). Each of these approaches has its merits and limitations. ...
Emerging contaminants, such as the hormone 17α‐ethynylestradiol (EE), in aquatic environments pose a serious risk to both human and environmental health, making efficient removal essential. This study evaluated the effectiveness of three‐dimensional porous carbon structures derived from poly(acrylic acid) (PAAc, Carbopol 990) as adsorbents for removing EE from aqueous solutions. Activated carbon materials were prepared using varying ratios of KOH as an activating agent (PAAc : KOH; 1 : 0 AAC, 1 : 1 AC1, 1 : 2 AC2, and 1 : 3 AC3). Adsorption tests were conducted by adding 10 mg of the adsorbent to 40 mL of an EE solution (100 ppm, 20 % acetonitrile in water). Analyses including TGA, XRD, and Raman spectroscopy were performed to evaluate the materials’ structural properties and adsorption capacities. Among the materials, AC3 exhibited the highest adsorption capacity for EE (238 mg g⁻¹), followed by AC2 (153 mg g⁻¹) and AC1 (82 mg g⁻¹). The superior efficiency of AC3 can be attributed to its larger surface area and pore volume, enabling greater interaction with EE molecules. These materials demonstrated higher adsorption capacities compared to commercial activated carbons and single‐walled carbon nanotubes. This work opens new possibilities for developing efficient adsorbents, contributing to more effective and sustainable solutions for water purification and environmental protection.
... Because of these characteristics, several research projects have focused on creating polymer-based nanocomposites that include graphene [6]. Graphene oxide's versatility extends to its role in composite materials, where it improves properties such as lubrication, thermal conductivity, and mechanical strength [7]. ...
... where a is the unit-cell length along the x-axis. Additionally, H 00 and H 01 describe coupling within a principal unit cell (intra-unit cell) and between adjacent principal unit cells (inter-unit cell), respectively, which can be mapped from the real-space TB model given by (2). Based on the TBA model, the electronic Hamiltonian for the PG in real space can be written as ...
Introducing defect vacancies into nanostructures is a straightforward yet powerful technique employed by scientists to manipulate their properties. In this study, we used a tight-binding model to investigate the eects of an external electric eld and the creation of double vacancies at dierent sites on penta-graphene nanoribbons on the electronic and transport properties. Understanding the eects of external electric elds and vacancy creation on the electronic and transport properties of penta-graphene nanoribbons is important for the advancement of nanoelectronics and the development of innovative applications. After calculating the formation energy for all vacancy structures, it was determined that the maximum stability is achieved when the second vacancy is at the C2 site. By creating vacancies in the structure, in addition to tuning the energy gap, an indirecttodirect bandgap transition can be achieved in penta-graphene nanoribbons. The presence of a direct gap in the electronic properties of penta-graphene nanoribbons has signicant implications. Direct bandgap materials can absorb and emit photons with energies close to the bandgap energy and may be better suited for optical devices. It was also observed that the creation of vacancies in penta-graphene nanoribbons leads to a phase transition from a semiconductor to a metal. Next, the eect of these vacancies on the transport properties of penta-graphene nanoribbons was investigated. The results clearly show that the maximum current and threshold voltage can be controlled by creating vacancies at various sites on the nanoribbon. In general, by creating double vacancies in the structure or applying an external electric eld, an indirect transition to a direct band gap and a semiconductortometal phase transition have been observed. Additionally, when a double vacancy is introduced into the system and an external electric eld is applied simultaneously, at bands are observed in the band structure, as are the tunable band gap, semiconductortometal phase transition, and indirecttodirect bandgap transition. Additionally, to explore the cause of the change in electronic and transport properties with the creation of a vacancy in the structure, the charge density distribution of carbon atoms was analyzed using density functional theory calculations. Due to the dierence in charge density between the penta-graphene nanoribbon sites, signicant charge transfer occurs in the structure after a double vacancy is created in the structure. This charge transfer leads to the generation of an electric current in the nanoribbon. Because of these unique characteristics, penta-graphene nanoribbons are promising candidates for the development of solar cells.
... Reduced graphene oxide (rGO) demonstrates robust nonlinear optical characteristics, attributed to its substantial χ³ value. As the concentration of rGO increases, its impact on the nonlinear refractive index becomes more pronounced, resulting from intensified light-matter interactions and a greater density of excited charge carriers [40][41][42][43]. ...
This paper investigates the impact of reduced graphene oxide (rGO) addition on the structural and optical properties of ZnS nanocomposites. The study began with the synthesis of graphene oxide (GO) through the oxidation of natural graphite powder. This process involved using potassium permanganate in a mixture of sulfuric and phosphoric acids, maintained at 50°C for 48 hours. The reaction was terminated using hydrogen peroxide, followed by purification and drying, yielding 1.5 grams of GO. The preparation of ZnS/GO nanocomposites involved dissolving zinc acetate and varying quantities of GO in water, adjusting the pH, and incorporating sodium sulfide. This mixture underwent heating in an autoclave at 180°C for 12 hours, followed by washing and freezing, resulting in ZnS-RGO composites with differing GO contents. The resulting products were categorized as ZnS0rGO, ZnS-5rGO, ZnS-10rGO, ZnS-15rGO, and ZnS-20rGO. To characterize these composite samples, the researchers employed several analytical techniques, including thermogravimetric analysis (TGA), X-ray diffraction (XRD) analysis, X-ray Photoelectron Spectroscopy (XPS), and UV-vis spectroscopy. This comprehensive approach allowed for a thorough examination of the effects of rGO incorporation on the nanocomposite's properties. The X-ray diffraction (XRD) results showed increased diffraction intensity with higher rGO content, attributed to improved crystallinity. The crystallite size and lattice strain also increased, with rGO providing nucleation sites. Optical analysis revealed that rGO increased absorbance and decreased the optical band gap, likely due to enhanced free charge carriers. The extinction coefficient and nonlinear refractive index both increased with rGO content, attributed to rGO’s high polarizability and light-matter interactions.
... It is noteworthy that existing studies indicate that the improvement in ductility is often accompanied by a loss in strength, which is particularly evident in Cu-based systems [14]. To address this issue, researchers have proposed introducing reinforcement phases into amorphous materials [15][16][17], with graphene being considered an effective reinforcement material due to its excellent mechanical properties (strength of 130 GPa, Young's modulus close to 1 TPa) and unique two-dimensional structure [18], and a small amounts of graphene can significantly enhance the mechanical properties of the composites [19,20]. The strengthening effect of Gr in metal-matrix composites is attributed to its superior load-bearing capability and stress transfer proficiency [21]. ...
Metallic glasses are very strong and elastic because of their unique atomic structure. However, they often break suddenly and lack ductility. The study aims to investigate the reinforcement mechanism of amorphous Fe3Cu by molecular dynamics simulations. To achieve this, different lengths and orientations of graphene are introduced to explore their effects on amorphous Fe3Cu. Additionally, different thicknesses of crystalline Cu3Fe are incorporated on the basis of graphene embedding to examine their influence on the strength and ductility of amorphous Fe3Cu. It is shown that complete embedding of graphene with a zigzag pattern along the Z-direction considerably enhances the composite’s strength. Furthermore, with increasing crystal layer thickness, the composite’s yield stress gradually increases due to graphene inhibiting shear transformation zones in the amorphous layer and hindering dislocation movement in the crystal layer. Moreover, the occurrence of numerous dislocation reactions leads to a significant increase in the ductility of the composite when the crystalline Cu3Fe layer is thicker. The results elucidate the plastic deformation behavior of crystalline/graphene/amorphous composites at the nanoscale and offer theoretical guidance for designing amorphous-matrix composites with high strength and excellent ductility.
... Since its isolation as a monolayer in 2004, graphene has been the focus of extensive research due to its extraordinary mechanical, electrical, and thermal properties [1]. It has been successfully incorporated into various materials, creating composites that exhibit enhanced mechanical properties [2,3]. However, to the best of the authors' knowledge, graphene has not yet been explored as an additive in sanitary ceramics. ...
In the competitive production of sanitary ceramics (SCs), fractures during the drying and handling stages significantly contribute to production waste. This study explores the incorporation of graphene, known for its exceptional mechanical properties, to enhance the strength and reduce waste in SCs. Utilising a modified slip casting process, graphene was introduced into Vitreous China (VC) and Fine Fireclay (FFC) ceramics through two methods representing two points of possible graphene inclusion along the production process: An earlier inclusion stage, which was examined by adding graphene solution into ceramic powder to create slip (powder-solution) and a later stage represented by graphene solution added to a readymade slip (solution-solution). The results demonstrated that the solution method significantly improved the mechanical strength of VC, achieving a 12% increase at 1 g graphene inclusion, while the powder method caused a decline in strength due to slip flocculation. FFC showed consistent strength improvements with both methods, with an average increase of 7% at 1 g graphene inclusion. Although the potential for graphene-enhanced ceramics is promising, further research is needed to quantify material savings, evaluate cost-effectiveness, and optimise the integration process for industrial-scale production.
... Figure 3(c) shows the Fourier transform infrared spectra of rGO, PhI and PhI/rGO-4. The peaks GO at 3431 cm −1 and PhI at 3206 cm −1 are-OH stretching vibration peaks, while a slight shift is observed in PhI/rGO-4 [34]. PhI exhibits a bending vibration peak of the benzene ring at 813 cm −1 ; the same peak but with lower intensity is observed in the spectrum of PhI/rGO-4. ...
Graphene aerogels have attracted considerable attention owing to their significantly higher electrical and thermal conductivity compared with conventional materials. To further enhance the surface functionality of graphene aerogels, we prepared three-dimensional multi-functional aerogels via hydrothermal treatment and freeze-drying using natural green organic small-molecule compound phloretin and graphene oxide. This aerogel has excellent electrochemical properties, with a specific capacitance as high as 433 F g⁻¹ (at a current density of 1 A g⁻¹). In addition, symmetrical supercapacitors (SCs) assembled with this electrode material exhibit excellent energy storage performance with an energy density of 13.33 W h kg⁻¹, power density of 399.9 W kg⁻¹ and capacitance retention rate of 88% after 10 000 cycles. Furthermore, a phase change material prepared using the aerogel and pure paraffin wax shows significantly higher energy conversion efficiency than sole paraffin wax and exhibits good thermal stability. Overall, owing to its unique physicochemical properties and environmental friendliness, the prepared multi-functional aerogel has good application prospects in the fields of SCs and thermal management.
... These peaks conrm the presence of abundant oxygen-containing groups. 30 In contrast, these characteristic peaks are nearly absent in pure GA, suggesting substantial reduction of GO during hydrothermal treatment. For ENR, peaks at 1249 cm −1 and 875 cm −1 correspond to the stretching vibrations of the C-O-C ring, indicative of epoxy groups. ...
Addressing the environmental challenges posed by oil spills and industrial wastewater is critical for sustainable development. Graphene aerogels demonstrate significant potential as highly efficient adsorbents due to their high specific surface area, excellent structural tunability and outstanding chemical stability. Among available fabrication methods, the hydrothermal self-assembly technique stands out for its low cost, high tunability and good scalability. However, brittleness caused by stacking and agglomeration of graphene layers during self-assembly remains a significant challenge. In this study, we present a green and efficient self-assembly strategy combining a one-step hydrothermal process with a solution immersion method to fabricate a PDMS-coated epoxidized natural rubber–graphene composite aerogel (P@EGA). The resulting aerogel exhibits a high specific surface area (482.362 m² g⁻¹), hierarchical pore distribution from microporous to macroporous, ultra-low density (0.0104 g cm⁻³) and excellent hydrophobicity (contact angle = 147.6°). Remarkably, it retains 97.54% of its compressive stress after 50 compression-release cycles at 80% strain and quickly recovers its shape under a 500 g load. The P@EGA aerogel demonstrates outstanding adsorption capacities (65.37–132.75 g g⁻¹) for various oils and organic solvents, complete oil absorption in 0.4 seconds, and effortless regeneration through simple squeezing. Furthermore, its dual functionality in gravity-driven and powered water–oil separation systems underscores its broad application potential in environmental remediation.
... The discovery of graphene has sparked a significant amount of research interest in other 2D materials, with the goal of achieving novel functionalisation and applications [30]. The exceptional physical and molecular properties of this atomically thin carbon layer with honeycomb lattices, which was initially achieved by exfoliating graphite crystals, have piqued significant research interest [31][32][33]. To investigate novel electronic, optical, or energy applications, substantial endeavours have been undertaken to investigate alternative 2D materials, including such as h-BN, TMOs, transition metal dichalcogenides (TMDs), silicene, germanene, MXcenes, phosphorene, metal oxide monolayers, group IV-VI or I-V monochalcogenides monolayers, and borophene [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. ...
Solar-powered catalytic reactions are attractive for addressing energy and environmental issues. Photocatalysts are chemically stable semiconductors that initiate chemical reactions in adsorbed molecules when photoexcited charge carriers diffuse to the surface. The interface properties of photocatalysts play a crucial role in improving charge separation and charge transfer processes in photocatalytic reactions. Transition metal oxides (TMOs) are widely used as photocatalysts due to their excellent stability, affordability, abundance on Earth, and remarkable catalytic activity. Recent advancements in nanomaterial growth have significantly accelerated research in this field. This allows for fine-tuning catalyst performance by controlling the morphology of powder catalysts. Recent developments in surface characterisation of oxides have provided a deeper understanding of the atomic structure of surfaces and their interaction with the environment. The discovery of novel surface phases exhibiting unique electrical characteristics has opened up new routes for enhancing the performance of photocatalytic materials.
... Key words: all-carbon composite film; reduced graphene oxide fibers; room-temperature ferromagnetism; magnetoresistance effect 石墨烯是单原子碳以 sp 2 (C=C)杂化成键方式形 成的二维材料，拥有诸多优异的物理和化学性质 [1][2][3] 。 但是由于本征石墨烯原子层中电子完美的 π 电子去 局域网络，不存在未配对电子自旋局域磁矩，因而 表现出固有的抗磁性 [4] ，限制了其在未来电子行业 中的广泛应用。近年来，石墨烯基碳材料的磁性研 究被相继报道，包括石墨烯降维成一维的纳米带及 零维的纳米结构 [5] ， 设计制备具有顺磁性、 反铁磁性 和室温铁磁性的石墨烯及衍生物氧化石墨烯(GO) 和还原氧化石墨烯(rGO) [6][7] 。其中通过引入结构或 化学缺陷等方法，例如空位、掺杂、吸附原子、锯 齿(zig-zag)边缘 π 电子态等策略，均可在理论研究 或实验观察中发现石墨烯基碳材料体系铁磁性特征 [8][9][10] 。开发室温稳定的铁磁性石墨烯基全碳材料的 研究不仅对基础物理学科的发展意义重大，而且在 轻质、透明和生物相容性等关键领域具有重要的应 用价值。 GO 是一类具有单原子碳层的石墨氧化物，主 要元素是碳、氧、氢，具有与本征石墨烯晶格不同 的特征，电子杂化结构为 sp 2 (C=C，C=O)和 sp 3 (C-C, C-O) [11] 。GO 纳米片化学结构显示出多种含氧官 能团，其中羰基(C=O)和羧基(-COOH)位于片层边 缘，羟基(-OH)和环氧基(-O-)位于面内。含氧官能 团降低了石墨烯本征结构的电学性质，但是丰富了 其表面活性，赋予了 GO 在生物医学领域更多的可 能性应用 [12][13] 。通过化学法、热处理、电化学和微 生物等多种方法， 可以去除 GO 中部分含氧官能团， 部分恢复石墨烯共轭结构。由于 rGO 在力学和电学 方面的优势，在开发新一代抗微生物材料和组织工 程支架材料方面呈现出广阔的应用前景 [14][15] 。近年 来，对 GO 和 rGO 的磁性研究更有希望拓宽石墨烯 基材料在生物医学领域的应用，例如利用顺磁特性 制备新型造影剂、借助铁磁特性吸收或屏蔽电磁波 及作为药物递送载体材料等 [7] 。 目前， GO 和 rGO 的 铁磁性和磁性产生机理研究处于初期阶段，相关石 墨烯基纳米片缺陷结构、含氧官能团种类和密度等 因素对铁磁性的贡献机理尚待澄清，而且尚未实现 规模化、低成本制备性能稳定的全碳膜。理论研究 表明， -OH 是一类理想的 sp 3 型结构缺陷， 单个-OH 能够产生约 1 玻尔磁子(μ B )数量的稳定的局域自旋 磁矩 [16] 。通过硼氢化钠碱性溶液处理 GO 纳米片 [17] 或采用高温加热方法 [18] ，可以促使面内-O-迁移和 开环，从而提高材料中-OH 含量，获得具有高饱和 磁化强度的石墨烯基碳材料。然而，Wang 等 [19] 的理 论计算结果表明，只有特定分布结构的-OH 才能产 生有效的不成对自旋，即六元环内的一个碳原子分 别与两个不相邻碳键-OH 相连。而环氧基对铁磁性 可能产生的贡献方面，Bagani 等 [18] [28] ，但是元素掺杂制备条件严苛。 围绕创建边缘态、空位和功能化等方法，尚需开展 大量研究，不仅深入探讨室温铁磁性增强规律与机 理，而且采用简便且高效制备技术，提升石墨烯基 碳材料的铁磁性能，以推动多功能全碳材料在未来 的应用。 还原氧化石墨烯纤维(rGOFs)是一种由rGO纳 米片紧密排列而成的宏观碳质纤维，制备过程中不 使用任何黏合剂或表面活性剂 [29] 。石墨烯纤维承接 了石墨烯纳米片组装体的优异性质，同时拥有碳纤 维诸多优点，如质轻、柔韧性好、制备成本低、易 于功能化等。 采用一步限域水热(DCH)技术， 通过组 装不同尺寸范围内的GO纳米片，可以调控rGOFs 表面拓扑形貌和sp 3 /sp 2 比值 [30][31] 。研究发现，rGOFs 具有良好的生物学性质 [30,[32][33][34] 。最近，Zhao等 [35] 报 道了采用DCH技术，将横向尺寸约为 2.14 μm的GO 纳米片组装成rGOFs。rGOFs具有微纳定向结构， rGO纳米片呈现许多边缘和褶皱形貌；纤维生物相 容性好，对长距离缺损的大鼠坐骨神经表现出优异 的修复功能。 为了进一步拓宽rGOFs的应用范围， 同 时受不同维度材料组装提升电磁性能的策略启发 [36] ，本研究制备了一种rGO基全碳膜，即由rGO纳米 片和rGOFs(直径约45 μm，长度变化范围为50~100 μm)组成rGO-rGOFs自支撑膜。本工作旨在探讨GO [35,37] [40][41] 。rGO-rGOFs 复合膜样品 中 D*峰强度的增加也表明 rGOFs 的引入产生了更 多的 sp 3 型缺陷。 本研究发现， 当加入 20 mg 的 rGOFs 时，D*峰的强度达到最大值。D"峰源于样品中的非 晶相，其强度与样品的结晶度成反比。分析表明， rGO-rGOFs 所有样品具有与 rGO 相似的 D"峰。在 1607 cm -1 附近出现的 D'峰对应于与 G 峰的谷内 (intra-valley)共振，代表了碳材料中与缺陷相关的层 ...
... Due to their peculiar physical and chemical properties, 2D nanostructures have a huge diversity of potential applications in nanoelectronics, spintronics, optoelectronics, nanomedicine, hydrogen storage and so forth. [2][3][4][5][6][7][8][9][10][11][12][13][14] At the same time, the number of already synthetized or predicted 2D materials is increasing continually. ...
In the quest for stable 2D arsenic phases, four different structures have been recently claimed to be stable. We show that, due to phonon contributions, the relative stability of those structures differs from previous reports and depends crucially on temperature. We also show that one of those four phases is in fact mechanically unstable. Furthermore, our results challenge the common assumption of an inverse correlation between structural complexity and thermal conductivity. Instead, a richer picture emerges from our results, showing how harmonic interactions, anharmonicity and symmetries all play a role in modulating thermal conduction in arsenenes. More generally, our conclusions highlight how vibrational properties are an essential element to be carefully taken into account in theoretical searches for new 2D materials.
... Whilst pristine graphene is one of the most relevant materials of the decade, several important shortcomings must be overcome before it may step from fundamental physics to applied technology. 1 In particular, the absence of an electronic band gap and its extreme chemical inertness undoubtedly compromise its use as an active element in electronic devices or hybrid structures. Molecular functionalization of graphene can provide singular and advantageous properties, and there have been many attempts via nondestructive methodologies to furnish graphene with surface modifications whilst attempting to preserve its extraordinary properties. ...
Technologically useful and robust graphene-based interfaces for devices require the introduction of highly selective, stable, and covalently bonded functionalities on the graphene surface, whilst essentially retaining the electronic properties of the pristine layer. This work demonstrates that highly controlled, ultrahigh vacuum covalent chemical functionalization of graphene sheets with a thiol-terminated molecule provides a robust and tunable platform for the development of hybrid nanostructures in different environments. We employ this facile strategy to covalently couple two representative systems of broad interest: metal nanoparticles, via S-metal bonds, and thiol-modified DNA aptamers, via disulfide bridges. Both systems, which have been characterized by a multi-technique approach, remain firmly anchored to the graphene surface even after several washing cycles. Atomic force microscopy images demonstrate that the conjugated aptamer retains the functionality required to recognize a target protein. This methodology opens a new route to the integration of high-quality graphene layers into diverse technological platforms, including plasmonics, optoelectronics, or biosensing. With respect to the latter, the viability of a thiol-functionalized chemical vapor deposition graphene-based solution-gated field-effect transistor array was assessed.
... We additionally investigated the utility of the formed lipid membranes through a biomolecular binding event, specifically between the biotin-avidin complex which is the strongest known non-covalent biological interaction [54], [55] and is used for the development of robust and highly sensitive assays useful in protein detection [56], [57]. Non-covalent intermolecular interactions involving π-systems are pivotal to the stabilization of proteins, enzyme-drug complexes and functional nanomaterials [5], [58]. One possible route to experimentally accomplish this binding event is by presenting the avidin protein dispersed in buffer to lipid membranes formed from biotinylated lipid vesicles that have been adsorbed, and in some cases ruptured and reorganized on a supporting substrate. ...
We report on the adsorption dynamics of phospholipid membranes on graphene-coated substrates using the quartz crystal microbalance with dissipation monitoring (QCM-D) technique. We compare the lipid vescle interaction and membranne formation on gold and silicon dioxide QCM crystal surfaces with their graphene oxide (GO) and reduced (r)GO coated counterparts, and report on the different lipid structures obtained. We establish graphene derivative coatings as support surfaces with tuneable hydrophobicity for the formation of controllable lipid structures. One structure of interest formed are lipid monolayer membrannes which were formed on rGO, which are otherwise challenging to produce. We also demonstrate and monitor biotin-avidin binding on such a membranne, which will then serve as a platform for a wide range of biosensing applications. The QCM-D technique could be extended to both fundamental studies and applications of other covalent and non-covalent interactions in 2-dimensional materials.
... Specifically, graphene grown at high temperatures by chemical vapor deposition can introduce silicon and oxygen impurities originating from the quartz (SiO 2 ) substrate or the apparatus itself. Also using silicon carbide (SiC) 13, 14 to grow graphene can produce silicon impurites. Another avenue would be to deliberately introduce silicon impurities by post-synthesis treatments 15,16 , such as by low-energy ion irradiation, similar to direct ion implantation of N and B atoms into single graphene sheets 17 , or deposition of Si atoms on ion or electron-beam treated graphene with irradiationinduced vacancies. ...
We theoretically study the atomic structure and energetics of silicon and silicon-nitrogen impurities in graphene. Using density-functional theory, we get insight into the atomic structures of the impurities, evaluate their formation energies and assess their abundance in realistic samples. We find that nitrogen, as well as oxygen and hydrogen, are trapped at silicon impurities, considerably altering the electronic properties of the system. Furthermore, we show that nitrogen doping can induce local magnetic moments resulting in spin-dependent transport properties, even though neither silicon nor nitrogen impurities are magnetic by themselves. To simulate large systems with many randomly distributed impurities, we derive tight-binding models that describe the effects of the impurities on graphene {\pi} electron structure. Then by using the linear-scaling real-space Kubo-Greenwood method, we evaluate the transport properties of large-scale systems with random distribution of impurities, and find the fingerprint-like scattering cross sections for each impurity type. The transport properties vary widely, and our results indicate that some of the impurities can even induce strong localization in realistic graphene samples.
... As one of the most promising two-dimensional materials, graphene has shown exceptional physical, chemical, and optical properties. [1][2][3][4] However, pristine graphene doesn't have gap between valence band and conduction band which hampers its applications in semiconductor devices. Although layered transition-metal dichalcogenide (TMDC) has the similar hexagonal structure like graphene, it shows distinctly different properties from graphene. ...
A photoinduced current of a layered MoS2-based transistor is studied from first-principles. Under the illumination of circular polarized light, a valley-polarized current is generated, which can be tuned by the gate voltage. For monolayer MoS2, the valley-polarized spin-up (down) electron current at K (K') points is induced by the right (left) circular polarized light. The valley polarization is found to reach +1.0 (-1.0) for the valley current that carried such a K (K') index. For bilayer MoS2, the spin-up (down) current can be induced at both K and K' valleys by the right (left) circular light. In contrast to monolayer MoS2, the photoinduced valley polarization shows asymmetric behavior upon reversal of the gate voltage. Our results show that the valley polarization of the photoinduced current can be modulated by the circular polarized light and the gate voltage. All the results can be well understood using a simple kp model.
... The initial discovery of monolayer graphene by Novoselov and colleagues [1] in 2004 was an important achievement. Graphene has been the subject of intense scientific interest [2,3] because of its various electronic and chemical properties [4,5] and its appealing applications: they have been employed in chemical engineering [6], solar cells [7], magnetic storage [8], electronic devices [9], energy storage [10], and biomedical applications [11]. Theoretically, numerous approaches and applications have been utilized to investigate the magnetic characteristics of graphene lattices, including the star-triangle transformation [12], the effective field [13], Monte Carlo simulation [14], and mean-field approximation [15][16][17][18][19][20][21]. ...
... В настоящее время существует несколько способов синтеза графена: механическое и химическое расслоение [3,4], химическое осаждение из паровой фазы [5], эпитаксиальные методы получения графеновых пленок [6]. Однако эти методы не нашли широкого применения в промышленности из-за высокой стоимости и сложности масштабирования. ...
Графен – привлекательный двумерный материал с превосходными механическими, электрическими и тепловыми свойствами. Массовое производство высококачественного графена в последние годы привлекает все больше внимания исследователей. В большинстве современных методах для синтеза графена используются очищенные химические реагенты, которые являются дорогими для крупномасштабного производства. Тем более, что для некоторых приложений такой высококачественный графен, полученный методами CVD, PVD, не требуется. Поиск технологически простого и экологически чистого метода синтеза графена для массового производства крайне необходим. В работе проведено исследование физико-химическими методами морфологических, структурных и термогравиметрических свойств отходов растительной биомассы на предмет получения из них графеноподобных структур комбинированным способом (гидротермальная обработка с физико-химической активацией). В качестве биопрекурсоров предложены и исследованы образцы пшеничной соломы, пшеничные отруби и рисовая шелуха. Полученные данные позволили сделать вывод о перспективности исходной биомассы по применению их в качестве бипрекурсоров для последующего синтеза графеноподобных структур предлагаемым методом.
We present an interesting low-cost, green, and scalable technique for direct ink writing for flexible electronic applications different from traditional fabrication techniques. In this work, a reduced graphene oxide (RGO)-bismuth oxide (Bi2O3)/carbon nanotube (CNT) (RGBC) ternary conductive ink was prepared by an initial synthesis of RGO-Bi2O3 (RGB) via a hydrothermal method. This was followed by the fabrication of conductive ink through homogenous mixing of the binary nanocomposite with CNTs in a mixture of ethanol, ethylene glycol, glycerol, and double-distilled water as the solvent. Electronic circuits were fabricated through directly writing the prepared ink on flexible nanocrystalline cellulose (NCC) thin film substrates. The nanocomposites consisted of rod-shaped nanoparticles that were grown on the surface of the nanographene sheet. The semiconductor nanocomposite exhibited excellent conductivity and further confirmed by applying it as an electrode in the electrical circuit to light a light-emitting diode (LED) bulb. The highest electrical conductivity achieved was 2.84 × 103 S·m−1 with a contact angle of 37°. The electronic circuit written using the conductive ink exhibited good homogeneity, uniformity, and adhesion. The LED experiment demonstrates the good conductivity of the electroconductive circuit and prepared ink. Hence, the NCC substrate and RGBC conductive ink showcase an excellent potential for flexible electronic applications.
Amine functionalization and silanization of graphene nanoparticles (GNPs) facilitate better interlocking interaction with the polymer matrix, leading to the development of high‐performance laminated composites for structural applications. Hence, in this article, the effect of amine functionalization and silanization of GNPs on the physical, mechanical, interfacial, and nano‐indentation mechanisms of functionalized GNPs (F‐GNPs) infused glass fiber reinforced bio‐epoxy polymer composites (GFRPCs) is investigated. To this end, different weight fractions of GNPs (0.5%, 1.0%, & 1.5%) with various oxidation times (24, 48, 72 h) have been considered for assessment. The interfacial interaction of normal and functionalized GNPs has been assessed through field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM). The homogeneous dispersion, crystallization, and exfoliation of GNPs have been analyzed with Fourier transform infrared (FTIR), Raman spectrometer, x‐ray diffraction (XRD), and x‐ray photoelectron spectroscopy (XPS). The results of FESEM and AFM revealed successful exfoliation of GNPs occurring at 48 h of oxidation. The characterization, such as FTIR, XRD, and XPS analyses, revealed that the functionalized GNPs provided better dispersion and interfacial interaction with the epoxy matrix. Further, the inclusion of functionalized GNPs improved the tensile strength, flexural strength, and interlaminar shear stress by 127.44%, 132.01%, and 23.79%, respectively, compared to neat glass fiber composites. In addition, a significant enhancement in the interfacial transverse properties of hybrid GFRPCs was achieved.
Highlights
The effect of functionalization and silanization of GNPs on GFRPCs is investigated.
Physical, interfacial and mechanical properties are studied.
Oxidation has been done at oxidation times of 24, 48, and 72 h.
Interfacial interaction of normal and functionalized GNPs is compared.
Enhanced properties obtained with the functionalization of GNPs and silanization.
The objective of this work is to prepare the Pd-decorated WS2 nanostructures using a hydrothermal technique, which is subsequently utilized in designing a photodetector device for detecting different wavelengths of the solar spectrum. Broadband photodetection can be significantly enhanced by developing transition metal dichalcogenides with tunable band gaps and unique electrical and optical properties. The X-ray photoelectron spectroscopy analysis has confirmed the presence of W4+ oxidation states, as evidenced by the observation of peaks corresponding to W5p3/2, W4f3/2, and W4f7/2 with binding energies of 37.83, 34.36, and 32.29 eV respectively. Plasmonic photodetector offers advantageous characteristics such as the ability to provide photodetection of different wavelengths by a single photodetector device. WS2 exhibits a notable responsivity of 125 mA·W−1 and a detectivity of 8.40 × 1010 cm·Hz1/2·W−1. On decorating with Pd, the responsivity and detectivity of the device increase up to 4.25 A·W−1 and 1.16 × 1014 cm·Hz1/2·W−1, respectively. By utilizing the plasmons at the semiconductor surface, a surface plasmon effect has been produced, thereby increasing the photocurrent value and offering numerous advantageous features.
Al matrix composites are the most promising candidate for light-weight components in the aerospace and automotive industries. Graphene has numerous applications across various fields due to its exceptional mechanical, electrical, and thermal properties. The incorporation of graphene into aluminium (Al) matrix composites shows significantly improved mechanical and physical properties compared with pure Al. This review article summarizes the properties and applications of graphene in various areas. This article covers the processing route and effect of different fractions of graphene in aluminium matrix. Moreover, the article evaluates the advancement in mechanical and microstructural properties in Al/graphene composites with various fractions of graphene content.
Mercury (Hg) and iron (Fe) contamination in the water is classified as water pollution. This study aims to synthesize and evaluate a reduced graphene oxide/zinc oxide (rGO/ZnO) composite as an efficient adsorbent for removing Hg and Fe in the water. The varied mass of GO was prepared by sonication, aiming to reduce particle size and the oxygen functional group of GO. The rGO/ZnO was prepared by mixing sonicated GO and Zinc (Zn) powder in distilled water, followed by hydrothermal treatment. The rGO/ZnO composite was characterized by scanning electron microscopy (SEM), showing the coverage of rGO layers by ZnO. The performance of the rGO/ZnO composite as an adsorbent for Hg and Fe removal was evaluated through adsorption experiments. The results in varied concentrations of GO showed that the composite rGO/ZnO exhibited high adsorption for Hg and Fe ions in the water, with the highest adsorption capacity of 126 mg/g and 22.95 mg/g, respectively. Meanwhile, the highest removal efficiency of the composite was 99.83% for Hg and 91.82% for Fe. The observed color in well water also changes qualitatively and quantitatively up to 92.26%. In conclusion, the rGO/ZnO composite is a promising adsorbent for removing Hg and Fe ions in the water and decolorizing water contaminated by Fe.
Graphene aerogels (GAs) have emerged as promising materials for supercapacitor applications, yet traditional
methods often fall short of achieving optimal surface modifications for enhanced electrochemical properties. The
focus of the review is to explore the current techniques used in plasma treatment for GA, how these are effective,
what can be done to improve the technology, and what further research is required to advance the field.
Particular attention is given to oxygen and nitrogen plasma treatments, which have shown significant improvements
in specific capacitance and cycling stability. Hydrogen plasma treatment assimilates hydrogen atoms
into graphene, potentially augmenting chemical reactivity and charge transfer. The introduction of nitrogen into
graphene through plasma treatment results in the incorporation of nitrogen atoms, which causes changes in the
electrical and mechanical characteristics of the material. This can lead to higher capacitance and enhanced
cycling stability, which means improved retention after charge-discharge cycles. The existing techniques are
primarily focused on reduced graphene oxide and other graphene fibers or GA, but the studies are minimal, and a
consensus on the overall reliability in achieving high capacitance is also seen to be less precise. This work
proposes future directions to facilitate the development of high-performance, plasma-treated GA supercapacitors.
An active pull on particles undergoing Brownian motion in particle-cluster aggregation leads to more open structures. Aggregates formed under these conditions are shown to have lower fractal dimensions and densities.
Deep eutectic solvents (DESs) have emerged as a captivating subject of scientific inquiry, driven by their unique molecular architecture and promising array of applications. Comprised of two or three components that engage in hydrogen bonding interactions, DESs exhibit eutectic behavior with a melting point lower than that of the individual constituents. Their fluid state, sustained even at temperatures lower than 100°C, underscores their versatility and practical appeal. Moreover, DESs offer a compelling alternative to conventional ionic liquids, boasting comparable physicochemical properties at a fraction of the cost and environmental impact. This distinctive combination of affordability and sustainability has sparked widespread interest among researchers across diverse fields. This chapter provides an overview of the latest research concerning the interaction between DESs and carbon allotropes, with a particular emphasis on recent breakthroughs and applications. The integration of DESs with carbon allotropes has ushered in a realm of fresh opportunities across diverse domains such as energy storage, environmental remediation, and catalysis.
Rapidly increasing global atmospheric carbon dioxide (CO2) concentrations, a direct consequence of unabated fossil fuel combustion, pose a serious threat to our planet, fueling drastic global climate change. In the last ten years, there has been a surge in the development of chemical sorbents cycled through adsorption–desorption processes for CO2 uptake, usually from low-concentration stationary sources like atmospheric air. The efficiency of these technologies, however, will depend on the development and optimization of promising next-generation materials tailored specifically for CO2 capture. Graphene, a special distinctive material discovered about two decades ago, has the potential to propel the world even further toward a more sustainable future goal, for our largely fossil fuel-dependent economies. Graphene has a single-atom-thick sheet of sp2-hybridized carbon atoms causing it to have exceptional and tuneable properties. These have made graphene the most widely studied nanomaterial of the twenty first century. This review provides a comprehensive overview of the graphene-based materials for CO2 capture/conversion. The review commences by exploring the synthesis techniques for graphene and the addition of dopants to tune its properties for targeted CO2 capture applications. Furthermore, the review discusses graphene derivatives for CO2 capture applications. Despite the immense potential, the practical implementation of graphene-based materials for direct air capture (DAC) will further exploration and development. Notably, engineering efficient graphene-air interfacial contact is paramount to expediting the deployment of DAC as a viable strategy for mitigating climate change. The review concludes by charting avenues for future research in environmental pollution mitigation through advanced material science and engineering approaches.
Material komposit nano graphene dan turunannya memiliki aplikasi yang luas di bidang nanobioteknologi kesehatan seperti material untuk sensor molekul DNA, bakteri, dan molekul penanda penyakit, rekayasa jaringan, pembawa obat serta untuk aplikasi lingkungan. Dalam ulasan ini, ditunjukkan pula pendekatan deteksi (sensor) berbasis material komposit nano graphene dengan menggunakan teknik surface-enhanced Raman spectroscopy (SERS) dan elektrokimia untuk mendeteksi DNA (adenin), S. aureus, uremik, dan dopamin. Selain itu, penelitian juga merangkum kemajuan penggunaan material komposit nano graphene sebagai scaffolds untuk rekayasa jaringan dan pembawa obat. Semua aplikasi yang sukses ini membuka jalan baru untuk membangun platform komposit nano graphene yang menjanjikan untuk pada bidang nanobioteknologi kesehatan dan lingkungan. Meskipun kemajuannya menarik dan menggembirakan, pemanfaatan material berbasis graphene untuk aplikasi nanobioteknologi kesehatan dan lingkungan masih memiliki tantangan. Pertama, proses sintesis material berbasis graphene akan mempengaruhi ukuran, bentuk, morfologi, dan ketebalan graphene. Oleh karena itu, metode baru untuk menyiapkan material berbasis graphene perlu dikembangkan. Kedua, material komposit nano graphene memiliki menunjukkan potensi besar dalam bioimaging karena toksisitasnya yang rendah secara in vivo. Ketiga, lebih banyak perhatian harus diberikan pada keamanan bahan graphene dengan mempelajarinya toksisitas jangka panjangnya. Tantangan-tantangan ini perlu dipecahkan melalui kolaborasi yang efektif berbagai disiplin ilmu termasuk kimia, fisika, biologi dan obat-obatan.
Human history has been defined by the dominant materials in use at that time, from the stone age until the age of silicon. As new, disruptive materials have been either discovered or developed, they have had to earn their place in society. Graphene and other new nanomaterials are no different. The graphene commercialization maturity journey is a review of the different stages of development that virtually all new materials have had to navigate on the road to commercial viability. The paper also identifies and reviews a common set of obstacles that must be addressed, any one of which can be a cause of failure for a material to become a commercial success. In this paper we define the stages of development, the associated challenges, and how they evolve over time. We have also provided examples for comparison and to illustrate the point. This framework will help assess graphene’s current position in its journey toward commercialization and can be applied to any of the many new advanced 2D nanomaterials that are currently at the early stages of development.
In experimental studies, hydrazine hydrate is widely employed as a reducing agent for the conversion of graphene oxide to graphene. Herein, we conducted theoretical calculations using cluster models to investigate the adsorption behavior of hydrazine hydrate on the surface of graphene. The calculated adsorption energy reveals that hydrazine hydrate can physically bind to the graphene surface. Our findings indicate that two hydrogen bonds stabilize the hydrazine hydrate molecule, while its adsorption onto the graphene surface is primarily driven by van der Waals forces. By combining computational simulations and experimental measurements, we thoroughly examined the Raman spectra of both free and adsorbed hydrazine hydrates, which enabled us to gain detailed insights into their molecular vibrations. Notably, in the Raman spectra of free hydrazine hydrate, a strong peak at around 3300 cm–1 corresponds to the NH2 vibration. Similarly, peaks near 3300 cm–1 were observed in the Raman spectra of graphene with adsorbed hydrazine hydrate molecules. The results are expected to provide valuable references for future experimental investigations involving hydrazine hydrate.
Currently, modified oxidized (intercalated) graphites and thermally expanded graphites obtained from them are used in solving many applied problems. This is due to the fact that while retaining all the properties of layered graphite compounds, split graphite particles have important new properties, such as ease of molding, low bulk density, and active interaction with the polymer matrix. However, the question of the mechanisms of expansion of oxidized graphite and the properties of thermally expanded graphite particles split into layers has not been sufficiently studied. The establishment of experimental patterns of expansion processes of graphite oxidized by acids contributes to the understanding of the set of stages of complex processes occurring during the expansion of graphite particles in a gas atmosphere and in polymer matrices. The purpose of the work was to synthesize a colloidal-graphite suspension based on thermally expanded graphite particles, to study the properties of suspensions and expansion processes of oxidized graphite during thermal and microwave heating. As a result of modifying thermally expanded graphite with low bulk density in activating media, colloidal graphite suspensions are synthesized without a vibration grinding stage. The splitting of graphite materials after chemical modification by thermal and microwave-stimulated heating leads to the formation of graphene-like structures. The development of techniques for modifying electrically conductive porous samples of materials used as electrodes makes it possible to introduce nanographite particles under the influence of an electric field.
Nanotechnology: A Quick Guide to Materials and Technologies invites readers to explore the cutting-edge world of nanotechnology, offering a comprehensive yet accessible introduction to this rapidly evolving field. The content provides a foundation for understanding the field and details the properties of significant nanomaterials. Readers will also gain insights into innovative processes while receiving a balanced perspective on the social and regulatory aspects of nanotechnology. Key Features: Foundational Knowledge: Begins with an overview of nanotechnology, its history, and its key concepts, Diverse Nanomaterials: Explores various types of nanomaterials, including nanoparticles, nanowires, and carbon-based materials like graphene, detailing their properties and potential applications. Advanced Applications: Explores the real-world uses of nanotechnology across multiple sectors, such as medicine, electronics, energy, and environmental science, demonstrating its transformative impact. Fabrication and Characterization: Covers techniques for creating and analyzing nanomaterials, offering insights into the processes that drive innovation in the field. Ethical and Societal Considerations: Discusses the broader implications of nanotechnology, including ethical, societal, and regulatory aspects Ideal for students, educators, researchers, and industry professionals, this guide serves as an informative resource for anyone looking to deepen their understanding of nanotechnology.
This article applies the coarse-grained (CG) molecular dynamics model of graphene to establish a new composite material CG model to expand the time range of atomic simulation of graphite/copper composite materials. We will combine the CG model of graphene structure and CG model of copper to calculate the thermal and mechanical properties of graphite/copper composites, including interface thermal resistance, thermal conductivity of composite materials, influence of graphite volume fraction on thermal conductivity of composite materials, as well as interface bonding analysis and uniaxial tensile properties of composite materials. For graphite/copper composite materials with a graphite volume fraction of 48.57%, the errors in thermal conductivity and uniaxial tensile properties calculated by the CG model (n = 2) compared to the AA model are only 4.2% and 3%, respectively, and save 69% of the calculation time. The CG model construction method proposed in this article can also be expected to be used for studying composite materials composed of graphite and other metals.
AA model and CG model of graphene/copper composite.
When annealed at elevated temperatures under vacuum, silicon carbide
surfaces show a tendency towards graphitization. Using the sensitivity
of empty conduction-band states dispersion towards the structural
quality of the overlayer, we have used angular-resolved inverse
photoemission spectroscopy (KRIPES) to monitor the progressive formation
of crystalline graphite on 6H-SiC(0001) surfaces. The KRIPES spectra
obtained after annealing at 1400 °C are characteristic of
azimuthally oriented, graphite multilayers of very good
single-crystalline quality. For lower annealing temperatures, the
ordered interface already presents most of the fingerprints of graphite
as soon as 1080 °C. The observation of unshifted π*
states, which reveals a very weak interaction with the substrate, is
consistent with the growth of a van der Waals heteroepitaxial graphite
lattice on top of silicon carbide, with a coincidence lattice of
(63×63)R30° symmetry. The growth of the first graphene sheet
proceeds on top of adatoms characteristic of the (3×3)R30°
reconstruction. These adatoms reduce the chemical reactivity of the
substrate. A strong feature located at 6.5 eV above the Fermi level is
attributed to states derived from Si vacancies in the C-rich subsurface
layers of the SiC substrate. This strongly perturbed substrate can be
viewed as a diamondlike phase which acts as a precursor to graphite
formation by collapse of several layers. In this framework, previously
published soft x-ray photoemission spectra find a natural explanation.
Mixed silicon-graphite composites were studied as an anode material for lithium ion batteries. Estimation of the capacity of the composite as a function of silicon mass fraction as well as the lithium mole fraction in the final Li-Si alloy was performed. When the Si/C composite electrode was prepared and tested under controlled conditions, it was possible to achieve stable electrode morphology even after extended cycling. Decreasing the composite particle size was essential for the improvement of the cycling performance. Further improvement could be a difficult problem since contradictious requirements would have to be satisfied. The average particle size and BET specific surface area should be acceptable so that the first cycle irreversible capacity loss would be reduced. The grain particle size should be small enough to achieve stable morphology. The match between the silicon and matrix is also an important issue, since during the reversible alloying the particles are repeatedly subjected to mechanical stress. When exposed to the electrolyte, the formed surface film could serve as a barrier for the further Li+ transport. This in turn will lead to a decrease in the cycling efficiency. A thin metal film deposited on the silicon cores could further improve the cycling efficiency in the presence of organic electrolyte.
The graphene nanosheet (GNS)/ultrahigh molecular weight polyethylene composite with a two-dimensional conductive network of GNSs exhibits an increasing positive temperature coefficient (PTC) of resistivity while thermally treated at a certain temperature. This anomalous phenomenon is originated from the reduced viscosity of polymer matrix, crystallization induced local flow and weak interactions among the overlapping joints of GNSs, which allow GNSs to migrate to the polymer matrix, thus weakening the conductive paths and increasing the PTC intensity. A facile approach is accordingly developed to prepare a conductive polymer composite with a tunable PTC intensity.
Poly(vinylalcohol)/reduced graphite oxide nanocomposites have been synthesised by reducing graphite oxide in the presence of the polymer matrix and coagulating the system with 2-propanol. It has been observed that some interactions occur between the polymer and the reduced graphite oxide layers, mainly by hydrogen bonding. These interactions are responsible for a remarkable change in the thermal behaviour of the nanocomposites. In addition, high electrical conductivity has been achieved at concentrations beyond 7.5 wt% of reduced graphite oxide (0.1 S cm−1), with a percolation threshold between 0.5 and 1 wt%.
A composite of graphite oxide (GO)-supported Co3O4 nanoparticles (NPs) was prepared through a facile chemical route. The lamellar GO sheets in this composite were exfoliated and decorated randomly by Co3O4 particles with an average size of 100 nm. The formation route to anchor Co3O4 NPs onto the exfoliated GO sheets was proposed as the intercalation and adsorption of cobalt ions into the layered GO sheets, followed by the nucleation and growth of Co3O4 crystals, resulting in the exfoliation of GO sheets. The nanocomposite reveals unusual catalytic effect for the decomposition of ammonium perchlorate due to the concerted effects of GO and Co3O4 NPs or their integrated properties. This methodology made the synthesis of GO-NP composites possible and may be further extended to prepare more complicated nanocomposites based on GO sheets for technological applications.
This work presents a novel approach to the functionalization of graphite nanoparticles. The technique provides a mechanism for covalent bonding between the filler and matrix, with minimal disruption to the sp2 hybridization of the pristine graphene sheet. Functionalization proceeded by covalently bonding an epoxy monomer to the surface of expanded graphite, via a coupling agent, such that the epoxy concentration was measured as approximately 4wt.%. The impact of dispersing this material into an epoxy resin was evaluated with respect to the mechanical properties and electrical conductivity of the graphite–epoxy nanocomposite. At a loading as low as 0.5wt.%, the electrical conductivity was increased by five orders of magnitude relative to the base resin. The material yield strength was increased by 30% and Young’s modulus by 50%. These results were realized without compromise to the resin toughness.
A silicon chip is covered by a monomolecular film of a fluorescence dye with silicon dioxide used as a spacer. The fluorescence depends on the distance of the dye from the silicon. The modulation of the intensity is described quantitatively by an optical theory which accounts for interference of the exciting light and of the emitted light. The effect is used to obtain a microscopic picture of the surface profile with a precision of a few Angströms. The perspectives for an application in wet systems such as neuron-silicon junctions and lipid membranes on silicon are pointed out.
The design feature and principles of atomic force microscopy (AFM) instruments are discussed. AFM can provide images of atoms on sample surfaces in three dimensions and can be used to measure force at the nanonewton scale. The Nano-R AFM consists of an IBM PC type master computer control unit, Nano-R stage and software for acquiring and analyzing images. The AFM chip prototype eliminates the optical readout system of a standard desktop AFM instrument.
Objective: To compare the anesthetic effects of obturator nerve blockade (ONB) and succinylcholine (SCL) during transurethral resection of bladder tumors underwent spinal anesthesia, and to explore the best modality for prevention of obturator nerve reflex. Methods: The data of 90 patients with superficial bladder tumors were retrospectively reviewed. Of all the cases, 48 cases were managed with ONB and 42 cases with SCL. Between the two managements, the anesthetic successful rates were compared and analyzed during the procedures. Results: The anesthetic successful rates of the ONB and SCL group were 68. 8% and 100% respectively. The anesthetic successful rate of SCL group was significantly higher than that of ONB group (P<0.05). Conclusion: Due to its mechanism of action, succinylcholine is more effective and provides a simple and safe alternation to ONB.
We uncover the constitutive relation of graphene and probe the physics of its optical phonons by studying its Raman spectrum as a function of uniaxial strain. We find that the doubly degenerate E(2g) optical mode splits in two components: one polarized along the strain and the other perpendicular. This splits the G peak into two bands, which we call G(+) and G(-), by analogy with the effect of curvature on the nanotube G peak. Both peaks redshift with increasing strain and their splitting increases, in excellent agreement with first-principles calculations. Their relative intensities are found to depend on light polarization, which provides a useful tool to probe the graphene crystallographic orientation with respect to the strain. The 2D and 2D(') bands also redshift but do not split for small strains. We study the Gruneisen parameters for the phonons responsible for the G, D, and D(') peaks. These can be used to measure the amount of uniaxial or biaxial strain, providing a fundamental tool for nanoelectronics, where strain monitoring is of paramount importance.
We have fabricated electrodes for a supercapacitor using fluorinated single-walled carbon nanotubes (SWCNTs). Although the specific surface areas of the pristine and fluorinated SWCNTs are similar, the electrochemical reactions are different significantly from each other. The specific capacitance of the fluorinated SWCNTs is smaller than that of the pristine sample particularly at large discharge current density, which can be attributed to the micropores formed during fluorination. After heat treatment at 900°C for 30 min, the nonredox reaction is dominant, and furthermore, the fluorinated sample gives a larger specific capacitance than the pristine sample.
The preparation of graphitic oxide by methods described in the literature is time consuming and hazardous. A rapid, relatively safe method has been developed for preparing graphitic oxide from graphite in what is essentially an anhydrous mixture of sulfuric acid, sodium nitrate and potassium permanganate.
Intercalated natural crystalline graphite compounds [GICs] were formed followed by exfoliation and milling to produce sub-micron graphite flakes. SEM and TEM images showed that the average size of graphite became 0.86 um with a thickness of around 5 nm. The cost of this new nano-size graphite material was estimated to be around $5/lb or less. Since exfoliated graphite has superior mechanical, electrical, thermal properties and cost effectiveness, this material has been shown to be a superior potential reinforcement for polymer nanocomposites.
This study was carried out to investigate the eating habits and preference of snacks for students in Chungnam province. Questionnaires were collected from 333 students, which were divided into male and female, food nutrition majors and non-majors, and weight groups according to BMI. The results obtained were as follows; 1. 62.8% of students responded that they were healthy. A significant difference on the health question was found between male and female students (p
Graphite oxide (GO)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared by a novel method utilizing macroazoinitiator (MAI). The MAI, which has a poly(ethylene oxide) (PEO) segment, was intercalated between the lamellae of GO to induce the inter-gallery polymerization of methyl methacrylate (MMA) and exfoliate the GO. The morphological, conductivity, thermal, mechanical and rheological properties of these nanocomposites were examined and compared with those of intercalated nanocomposites prepared by polymerization with the normal radical initiator, 2,2′-azobisisobutyronitrile. The improvement in conductivity by GO was more evident in exfoliated nanocomposites compared to that of intercalated nanocomposites. For example, a conductivity of 1.78 × 10−7 S/cm was attained in the exfoliated nanocomposite prepared with 2.5 parts GO per 100 parts MMA, which was about 50-fold higher than that of the intercalated nanocomposite. The thermal, mechanical and rheological properties also indicate that thin GO with a high aspect ratio is finely dispersed and effectively reinforced the PMMA matrix in both exfoliated and intercalated nanocomposites.
For developing high performance graphene-based nanocomposites, dispersal of graphene nanosheets in polymer hosts and precise interface control are challenging due to their strong interlayer cohesive energy and surface inertia. Here we report an efficient method to functionalize graphene nanosheets. The initiator molecules were covalently bonded to the graphene surface via a diazonium addition and the succeeding atom transfer radical polymerization linked polystyrene chains (82 wt% grafting efficiency) to the graphene nanosheets. The prominent confinement effect arising from nanosheets resulted in a 15 °C increase in the glass transition temperature of polystyrene compared to the pure polymer. The resulting polystyrene nanocomposites with 0.9 wt% graphene nanosheets revealed around 70% and 57% increases in tensile strength and Young's modulus. The protocol is believed to offer possibilities for optimizing the processing properties and interface structure of graphene-polymer nanocomposites.
A recent letter about the effect of Coulomb interaction on variable-range hopping is discussed.
Transport in ultrathin graphite films grown on single-crystal silicon
carbide is dominated by the electron-doped epitaxial graphene layer at
the interface and shows graphene characteristics. Epitaxial graphene
provides a platform for studying the novel electronic properties of this
2D electron gas in a controlled environment. Shubnikov-de Haas
oscillations in the magnetoresistance data indicate an anomalous Berry's
phase and reveal the Dirac nature of the charge carriers. The system is
highly coherent with phase coherence lengths beyond 1 micrometer at
cryogenic temperatures, and mobilities exceeding 2.5 square meters per
volt-second. In wide structures, evidence is found for weak
anti-localization in agreement with recent graphene weak-localization
theory. Patterned narrow ribbons show quantum confinement of electrons.
Several Hall bar samples reveal anomalous magnetoresistance patterns
consisting of large structured non-periodic oscillations that may be due
to a periodic superlattice potential.
Tight-binding calculations, using a two-dimensional model of the graphite lattice, lead to a point of contact of valence and conduction bands at the corner of the reduced Brillouin zone. A perturbation calculation which starts with wave functions of the two-dimensional lattice and is applied to the three-dimensional lattice is described. Some general features of the structure of the \pi bands in the neighborhood of the zone edge are obtained and are expressed in terms of appropriate parameters.
Influences of H2O2 in H2SO4-GIC synthesis with natural graphite flakes at room temperature were studied using powder X-ray diffractometry. The results indicate that the efficiency of intercalation depends on a volume ratio of H2O2 to H2SO4. For 10 g graphite powder, mixed stage 3 and stage 4 GICs were obtained with a volume ratio of 1:15, while only stage 7 GICs were synthesized when the volume ratio was 3:15. When the reaction time increased from 15 to 120 min, the X-ray diffraction intensity ratio of GICs to graphite decreased. In addition, the expansion volumes for GICs synthesized under different conditions were measured and are reported here for the benefit of the flexible graphite manufacturing industry.
The exquisite structure of natural materials manifests the importance of particle mobility and load transfer in developing advanced polymer nanocomposites; however, it is difficult to concurrently meet these two mutually exclusive requirements. To address this issue, we demonstrate an approach that constructs a hierarchical, flexible interphase structure in epoxy nanocomposites through a local amine-rich environment around graphene sheets (GNs) and volume exclusion effect of grafting chains. Long-chain aromatic amines, which are chemically similar to the curing agent, are covalently bonded on the surface of GNs by diazonium addition. They play multifold roles in the structure formation of epoxy composites, (1) promoting the exfoliation and molecular level dispersion of GNs in the matrix, (2) serving as a linker between GNs and epoxy networks for improved load transfer, (3) modulating the stoichiometric ratio around GNs to construct a hierarchical structure that can dissipate more strain energy during fracture. With the addition of 0.6 wt% amine-functionalized GNs, the resulting composite exhibits significant mechanical improvements, 93.8 and 91.5% increases in fracture toughness and flexural strength, respectively. This approach affords a novel design strategy for developing high-performance structural composites.
A direct electrochemical DNA sensor was constructed based on gold nanoparticles/graphene film. A precursor graphene film was fabricated on glassy carbon electrode (GCE) using both electrochemically reduced graphene oxide (ERGNO) and chemically reduced graphene oxide (CRGNO). The electrochemical approach was green and fast, and unlike chemical reduction, does not result in contamination of the reduced material, and at highly negative potential could reduce the oxygen functionalities (–OH, C–O–C and –COOH) of the graphene oxide more efficiently. ERGNO exhibited better electrochemical and electrocatalytic performances than CRGNO. Gold nanoparticles (AuNPs) were electrodeposited on the ERGNO/GCE to amplify the electrochemical signals. The resulting AuNPs/ERGNO composite film was characterized by scanning electron microscopy, energy dispersive spectroscopy and Raman spectroscopy. The electrochemical responses of guanine (G), adenine (A), thymine (T) and cytosine (C) were investigated at AuNPs/ERGNO/GCE, which showed more favorable electron transfer kinetics than at ERGNO/GCE, demonstrating the significantly synergistic electrocatalytic effect of ERGNO and AuNPs. Synthetic sequence-specific DNAoligonucleotides was successfully detected and the established immobilization-free biosensor had the ability to discriminate single- or double-base mismatched DNA.
The recent discovery of graphene has sparked significant interest, which has so far been focused on the peculiar electronic structure of this material, in which charge carriers mimic massless relativistic particles. However, the structure of graphene is also puzzling. On one hand, graphene appears to be a strictly 2D material and exhibits such a high crystal quality that electrons can travel submicron distances without scattering. On the other hand, perfect 2D crystals cannot exist in the free state, according to both theory and experiment. This is often reconciled by the fact that all graphene structures studied so far were an integral part of larger 3D structures, either supported by a bulk substrate or embedded in a 3D matrix. We describe individual graphene sheets freely suspended on a microfabricated scaffold. These membranes are only one atom thick and still display a long-range crystalline order. However, our studies by transmission electron microscopy have revealed that suspended graphene sheets are not perfectly flat but exhibit intrinsic microscopic roughening such that the surface normal varies by several degrees and out-of-plane deformations reach 1 nm. The atomically-thin single-crystal membranes offer an ample scope for fundamental research and new technologies whereas the observed corrugations in the third dimension may shed light on subtle reasons behind the stability of 2D crystals.
Graphene, a recently discovered form of carbon, revealed many unique properties, including extremely high electron mobility of ~15000 cm2/Vs at room temperature (RT). We have experimentally studied the thermal conductivity of graphene suspended over a trench in silicon (Si) wafer. It was found for a given set of samples that RT thermal conductivity of graphene is in the range ~ 3080 - 5150 W/mK. The giant thermal conductivity and demonstrated graphene - Si integration suggest that graphene can become superior material for thermal management of Si nanoelectronic circuits.
Graphenenanosheets in the form of chemically reduced graphene oxide have been prepared in organic media without the need to chemically functionalise the starting graphene oxide nanosheets. The preparation procedure is simple and similar to that previously used for the production of stable aqueous dispersions of graphenenanosheets. The resulting organic dispersions are homogeneous, exhibit long-term stability and are made up of graphene sheets a few hundred nanometres large. The ability to prepare graphene dispersions in organic media facilitates their combination with polymers, such as polyacrylonitrile and poly(methyl methacrylate), to yield homogeneous composites.
SnO2/multi-walled carbon nanotube (MWCNT) composite was prepared via a diffusion method. Firstly the MWCNT was sonicated in a filtrate which was derived from a tin dichloride solution mixed with AgNO3 solution. Then the SnO2/MWCNT composite was prepared whereby, after calcination in N2 atmosphere, the salts inside the MWCNT decomposed to SnO2. The resulting composite was characterized by transmission electron microscopy, Raman spectroscopy and X-ray diffraction, which indicated that SnO2 had infiltrated into the MWCNT and filled the interior. The subsequent evaluation of the electrochemical performance in lithium ion batteries showed that the SnO2/MWCNT composite had a reversible discharge capacity of 505.9 mAh∙g−1 after 40 cycles, as compared to 126.4 mAh∙g−1 for pure nano-SnO2.
A study was conducted to prepare organic-solution-processable functionalized-graphene (SPF Graphene) hybrid material with porphyrins and to demonstrate its photophysical properties including optical-limiting properties. The synthesis of the porphyrin-graphene nanohybrid, 5-4 (aminophenyl)-10, 15, 20-triphenyl porphyrin (TPP) and graphene oxide molecules covalently bonded using an amide bond was carried out using an amine-functionalized prophyrin (TPP-NH2) and graphene oxide in N,N-dimethylformamide (DMF). FTIR, UV-vis absorption, and TEM studies were also carried out to examine covalent functionalization of the graphene. It was observed that the fluorescence of photo-excited TPP-NH2 was quenched by a possible electron-transfer process. These organic solution-processable functionalized graphene material can be used for light harvesting and solar-energy conversion materials for optoelectronic devices.
The factors determining the performance of supercapacitors were studied using single-walled carbon nanotube (CNT) electrodes. These factors were the equivalent series resistance (ESR), specific capacitance, energy density and power density. The specific surface area and the specific capacitance increased with increasing annealing temperatures of the sample. It was also found that most of the surface area of the electrode contributed to the theoretically estimated specific capacitance. Mpreover, minimization of the contact resistance was independent of the specific capacitance but directly related to the maximization of the power density.
We report a simple yet versatile method to simultaneously achieve the exfoliation and reduction of graphite oxide. By treating graphite oxide powders in a commercial microwave oven, reduced graphite oxide materials could be readily obtained within 1 min. Extensive characterizations showed that the as-prepared materials consisted of crumpled, few-layer thick and electronically conductive graphitic sheets. Using the microwave exfoliated graph- ite oxide as electrode material in an ultracapacitor cell, specific capacitance values as high as 191 F/g have been demonstrated with KOH electrolyte.
Hybrids of graphene oxide (GO) nanosheets and surface-modified Fe3O4 nanoparticles (NPs) were fabricated by a two-step process. First, Fe3O4 was modified by tetraethyl orthosilicate and (3-aminopropyl) triethoxysilane to introduce amino groups on its surface. Second, the amino groups of Fe3O4 were reacted with the carboxylic groups of GO with the aid of 1-ethyl-3-(3-dimethyaminopropyl)carbodiimide and N-hydroxysuccinnimide to form a GO–Fe3O4 hybrid. The attachment of Fe3O4 NPs on the GO nanosheet surface was confirmed by transmission electron microscopy and Fourier-transform infrared spectroscopy. The adsorption capacity of GO–Fe3O4 for methylene blue and neutral red cationic dyes was as high as 190.14 and 140.79mg/g, respectively. The GO–Fe3O4 hybrids could be reduced to form graphene–Fe3O4 hybrids by using NaBH4 as reducing agent and be used to prepare magnetic GO films.
Nanocrystalline multi-walled carbon nanotube (MWNT)–Sn and MWNT–SnNi composite anode materials were prepared by chemical reduction of SnCl2 and NiCl2 precursors in the presence of MWNTs. SEM and TEM observations showed that the Sn and SnNi particles are homogeneously dispersed on the MWNT surface and in the MWNT matrix. The electrochemical performance of MWNT–Sn and MWNT–SnNi nanocomposites has been investigated by charge/discharge tests, cyclic voltammetric experiments and the ac impedance technique. The MWNT–Sn and MWNT–SnNi anodes have demonstrated a high first discharge capacity (570 and 512mAh/g for MWNT–Sn and MWNT–SnNi anodes, respectively), high charge/discharge efficiency in the first cycle (77.5% and 84.1% for MWNT–Sn and MWNT–SnNi anodes, respectively), and good cyclability (0.99 loss%/cycle for MWNT/SnNi anode). A reaction model has been proposed to explain the reaction mechanisms of lithium insertion and extraction in the MWNT–Sn and MWNT–SnNi electrodes.
Polycarbonate composites reinforced with graphite and functionalized graphene sheets (FGS) were produced using melt compounding. Composite samples with different degrees of graphite orientation were processed via injection, compression molding and long-term annealing. Electron microscopy and X-ray scattering revealed that FGS was nearly exfoliated. However, graphite remained multi-layer even after melt processing. Flow induced orientation of graphite was observed from both injection and compression molded samples. Graphite particles in samples after long-term annealing exhibited more random orientation. Composites with the exfoliated FGS required a smaller amount of reinforcement for rigidity and connectivity percolation, as determined by melt rheology and electrical conductivity measurements. FGS also showed better performance in suppressing gas permeability of polycarbonate. However, improvements by FGS dispersion in tensile modulus and dimensional stability were not as significant. This may be due to defects in the sheet structure formed during oxidation and pyrolysis used to exfoliate.
A new process for the dispersion of graphite in the form of nanosheets in a polymer matrix was developed via in situ polymerization of monomer at the presence of sonicated expanded graphite during sonication. Graphite nanosheets prepared via powdering the expanded graphite had a thickness ranging 30–80nm and a diameter ranging 0.5–20μm and was an excellent nanofiller for the fabrication of polymer/graphite conducting nanocomposite. The process fabricated electrically conducting polystyrene/graphite nanosheet nanocomposite films with much lower percolation threshold and much higher conductivities than those of composites made by conventional methods.
A novel photoelectrochemical cells (PEC) based on quantum dots (QDs) sensitized graphene for light harvesting and energy conversion was described in this work. QDs sensitized graphene was prepared by in situ growth of QDs on noncovalently functionalized graphene. QDs sensitized graphene photoelectrodes showed enhanced photocurrent generation capability and incident photon-to-electron conversion efficiency (IPCE) at visible light, and could also be an efficient platform for other optoelectronic applications.
Graphene–ZnO composite film was synthesized for its potential application in supercapacitors. Graphene was prepared by a modified Hummers method and hydrazine reduction process, and ZnO was deposited on graphene by ultrasonic spray pyrolysis. The electrochemical characteristics of the film were investigated through electrochemical impedance spectrometry, cyclic voltammetry and chronopotentiometry tests. The results showed that graphene–ZnO composite film exhibited an enhanced capacitive behavior with better reversible charging/discharging ability and higher capacitance values, by comparison to pure graphene or ZnO electrode.
Graphene films and ribbons were grown on Ni-coated Si substrates using the microwave plasma enhanced chemical vapor deposition method. We report the structure, morphology, and quality of graphene films and ribbons. The semiconducting nature of the CVD-grown graphene was observed by studying resistance−temperature variation in the range 25 to 200 °C, using the four-point probe method. Graphene exhibited an increase of resistance upon exposure of CO and a decrease in resistance upon pure O2 and NO2 exposures. It was observed that graphene films show sensor signal 3 and 35 for 100 ppm of CO and 100 ppm of NO2 whereas the graphene ribbons show the sensor signal values of 1.5 and 18 for 100 ppm of CO and 100 ppm of NO2. The gas sensor mechanism was observed to be mainly dependent on the charge carrier transfer on conducting graphene surfaces caused by the adsorption of gases.
Influences of H2O2 in H2SO4-GIC synthesis with natural graphite flakes at room temperature were studied using powder X-ray diffractometry. The results indicate that the efficiency of intercalation depends on a volume ratio of H2O2 to H2SO4. For 10 g graphite powder, mixed stage 3 and stage 4 GICs were obtained with a volume ratio of 1:15, while only stage 7 GICs were synthesized when the volume ratio was 3:15. When the reaction time increased from 15 to 120 min, the X-ray diffraction intensity ratio of GICs to graphite decreased. In addition, the expansion volumes for GICs synthesized under different conditions were measured and are reported here for the benefit of the flexible graphite manufacturing industry.
We have investigated the key factors determining the performance of supercapacitors using singlewalled carbon nanotube (SWNT) electrodes. Several parameters of compositions of the binder, annealing temperature, type of current collectors, charging time and discharging current density are optimized for the best performance of the energy density and power density. We find a maximum specific capacitance of 180 F/g and a measured power density of 20 kW/kg at the energy density of 7 Wh/kg in a solution of 7.5 N KOH. The specific surface area and the specific capacitance increase with increasing annealing temperatures of the sample. It was found that most of the BET surface area of the SWNT electrode contributed to the theoretically estimated specific capacitance. Minimization of the contact resistance is independent of the specific capacitance but directly related to the maximum of the power density. .