Compared to carbon nanotubes (CNTs), graphene possesses high strength due to wrinkled surface texture caused by a high density of surface defects which benefits more contact with the polymer material than a rolled-up CNT. In the present review, we have discussed and compared the various properties of CNTs (1-D) and graphene (2-D) obtained in experimental results. The effects of covalent and non-covalent functionalization of CNTs and graphene on the properties of its composites have also been reviewed and compared. A comparative analysis has been carried out between CNTs and graphene-reinforced polymer composites. Furthermore, the synergetic effects of CNTs and graphene hybrid nanofiller on the mechanical properties of polymer composites have also been briefly discussed. Finally, this review concludes with the potential application and future challenges are discussed with regards to filler and their polymer composites.
Recent years have witnessed remarkable development in the field of nanotechnology and it has been affirmed that carbonbased nanomaterials have wide applications in agriculture, industrial, biomedical and environmental sectors. Due to distinctive physicochemical properties of the carbon nanotubes (CNTs), they have been extensively utilized in plant science as a growth promoter, and thus, could be a boon for biomass production of agricultural products. Studies suggest that CNTs help increase the plant’s ability to absorb water and essential nutrients, thereby increasing growth. Apart from this, CNTs have been scrutinized for their utilization in genetic engineering for the delivery of genes, proteins or drugs. However, the literature discloses mixed effects of CNTs exposure on plants like in inducing oxidative stress by generating reactive oxygen species (ROS). Moreover, studies concerning CNTs interaction with plant system is at a nascent stage and needs further investigations to explore the mechanisms influencing the growth and toxicity in plants. Therefore, this review attempts to highlight the current literature on CNTs (including both single walled and multi walled) exposure on plants. It also explores unresolved challenges, as well as recommendations to ensure sustainable development of CNTs while minimizing any possible adverse health impacts.
Abstract Graphene, an allotrope of carbon in 2D structure, has revolutionised research, development and application in various disciplines since its successful isolation 16 years ago. The single layer of sp2-hybridised carbon atoms brings with it a string of unrivalled characteristics at a fraction of the price of its competitors, including platinum, gold and silver. More recently, there has been a growing trend in the application of graphene in catalysis, either as metal-free catalysts, composite catalysts or as catalyst supports. The unique and extraordinary properties of graphene have rendered it useful in increasing the reactivity and selectivity of some reactions. Owing to its large surface area, outstanding adsorptivity and high compatibility with various functional groups, graphene is able to provide a whole new level of possibilities and flexibilities to design and synthesise fit-for-purpose graphene-based catalysts for specific applications. This review is focussed on the progress, mechanisms and challenges of graphene application in four main reactions, i.e., oxygen reduction reaction, water splitting, water treatment and Fischer–Tropsch synthesis. This review also summarises the advantages and drawbacks of graphene over other commonly used catalysts. Given the inherent nature of graphene, coupled with its recent accelerated advancement in the synthesis and modification processes, it is anticipated that the application of graphene in catalysis will grow exponentially from its current stage of infancy.
Increasing ambient carbon dioxide ( CO2) concentration from anthropogenic greenhouse gas emission has contributed to the growing rate of global land and ocean surface temperature. Various carbon capture and storage (CCS) technologies were established to mitigate this impending issue. CO2 adsorption is gaining prominence since unlike traditional chemical absorption, it does not require high energy usage for solvent regeneration and consumption of corrosive chemical solvent. In CO2 adsorption, activated carbons show high CO2 adsorption capacity given their well-developed porous structures. Numerous researches employed oil palm wastes as low-cost precursors. This paper provides a comprehensive assessment of research works available thus far in oil palm-derived activated carbon (OPdAC) for CO2 adsorption application. First, we present the desired OPdAC characteristics and its precursors in terms of their chemical properties, elemental, and proximate compositions. This is followed by an overview of various activation methodologies and surface modification methods to attain the desired characteristics for CO2 adsorption. Then the focus turned to present available OPdAC CO2 adsorption performance and how it is affected by its physical and chemical characteristics. Based on these, we identify the challenges and the potential development in different aspects such as precursor selection, process development, and optimization of parameter. A pilot scale production cost analysis is also presented to compare various activation and surface modification methods, so that the appropriate method can be selected for CO2 adsorption.
In the current work, we have developed a new composite catalyst for methanol oxidation based on Ni and/or NiO incorporated in activated carbon (AC) derived from agricultural wastes (Rice straw). The new electrocatalysts based on nickel-activated carbon (Ni/AC) and nickel oxide-activated carbon (NiO/AC) composites were prepared by electroless plating technique. Physico-chemical characteristics of the composites such as structure, composition and morphology were studied by X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and particle size analyzer. The electrochemical activity of the prepared composites towards methanol electrooxidation reaction (MOR) has been evaluated under alkaline conditions by cyclic voltammetry, linear sweep voltammetry, and chronoamperometry. Among the examined electrodes, the electrochemical performance of NiO/AC preceded either Ni/ AC or Ni free AC and showed better stability. The dispersion of different forms of Ni in activated carbon in case of NiO/AC electrode is predicted to give rise to the increase in electrocatalytic activity in the potential range under study and makes it more resistant to poisoning by the byproduct of methanol oxidation. The effect of changing methanol concentrations and scan rates on the electrochemical characteristics of the modified electrode was studied and it was found that the diffusion process is controlled by methanol rather than OH− ions.
In recent years, special attention of energy researchers has been paid to application of polymer–carbon dots composite in energy storage systems. In this work, for the first time, we introduced a combination of polyaniline, carbon dots, polypyrrole and graphene as high performance supercapacitor. Synergistic effect of conductive polymers combined with specific properties of graphene and carbon dots improved the electrochemical performance of supercapacitor. Carbon dots was prepared from carrot juice hydrothermally as a biomass carbon source and polyaniline–carbon dots was synthesized via in-situ polymerization. Electrochemical performance of polyaniline with different carbon dots content was investigated and nanocomposite of polyaniline with 10 wt% carbon dots was selected to mix with polypyrrole–graphene to obtain a high potential window supercapacitor. The as-prepared composite was characterized by several spectroscopic and microscopic techniques. The electrochemical properties of this electrode were studied by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy techniques. A polyaniline–carbon dots (10%)/polypyrrole–graphene has showed the maximum specific capacitance of 396 F g− 1. Value of specific capacity remained at 62% under the current density of 5 A g− 1.
Morphology control of a graphene nanosheet (GNS) is important for graphene-based battery electrodes to exhibit the increased practical surface area and the enhanced ion diffusion into the nanosheets. Nevertheless, it is very difficult to minutely control the shape of graphene nanosheets based on the conventional GNS suspension methods. In this work, we fabricated wrinkle textures of free-standing GNS for large area using Langmuir–Schaefer technique. The wrinkles are oriented vertically to the direction of the monolayer compression. The textured structure of GNS was obtained by cross-deposition of each layer with controlling the orientation of the wrinkle direction. These wrinkles can cause Li-ion to diffuse into the voids created by them and raise the specific surface area between the GNSs. Consequently, as a prospective anode for Li-ion battery, the wrinkled GNS multilayer, exhibits the high specific capacity of ~ 740 mAh g− 1 at 100 mA g−1 and the great power capability with ~ 404 mAh g− 1 being delivered even at 2 A g− 1. Furthermore, outstanding cycle performance of the wrinkled GNS multilayer is achieved over 200 cycles at 300 mA g−1 with high Coulombic efficiency of ~ 96%.
In this study, a new method of rapid preparation of carbon nanotube (CNT) solution with highly dispersed morphology by free arc excitation is proposed, which shortens the time of the preparation of CNT solution with low concentration. The principle is that the high-energy flow density heat generated by the free arc makes the vaporizable substance coated on the surface of CNTs vaporize rapidly, and then generates the bulk increasing motion, which makes the CNTs aggregates dispersed, and finally forms the CNTs gas-phase dispersion monomer with high dispersion or the cross-linking morphology of few CNTs. In this paper, the influence of gum Arabic (GA) and deionized water (DI water) contents in CNTs mixed electrode on the dispersion of CNTs in different environments (gas phase and liquid phase) is explored. In the limited case of this work, the dispersion effect is better when the mass ratio of CNTs, GA and DI water is 1:0.04:3.96 in the liquid-phase environment. The preparation method reported in this work is expected to be a rapid way to obtain low-concentration nanodispersion.
Molecules possessing harmine moiety are reported to exhibit marked fungicidal and bactericidal activities. In this study, various quinozilinium tetrafluoroborate salts were synthesized using acylic and cyclic oxoketene dithioacetals followed by cycloaromatization from Harmine. All of these synthesized compounds were characterized by 1H NMR, 13C NMR, Mass and CHN analysis. This methodology would find wide usage in the preparation of indolo quinozilinium -based library of small molecules useful for medicinal chemistry and in drug discovery.
In this study, graphene was rapidly grown by chemical vapor deposition using a liquid cell for supplying methanol as a carbon source of graphene. To realize the rapid growth, methanol which is carbon-contained organic solvent was used instead of methane gas, a widely used carbon source for graphene growth. The graphene grown with the growth time as a variable was transferred to a SiO2/ Si substrate with an oxide thickness of 300 nm to confirm whether it was grown with full coverage with an optical microscope. The results confirmed a full coverage in 0.5 min of growth. The Raman spectra also confirmed the G-peak position at 1585.0 cm−1 and an intensity ratio of 2D/G at 2.3 or higher. Concerning electrical transport characteristics, at an induced carrier density of 1 × 1012 cm−2, the hole (μh) and electron (μe) mobilities were 1524 cm2 V−1 s−1 and 1528 cm2 V−1 s−1, respectively. Thus, our study confirmed that high-quality, large-area graphene can be grown within 0.5 min.
We report a simple procedure to fabricate single crystals 3D C60 having an FCC structure on silicon substrates using a vapour–solid set-up in vacuum conditions. The morphology of the deposited film can be tuned by controlling the temperature and position of the substrate. The as-fabricated samples are extensively characterised by transmission electron microscopy, scanning electron microscope, X-ray powder diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and nanoindentation, which allow us to shed light on the recrystallization process of the C60. In addition, the growth mechanism of the formation of crystalline 3D structure of the C60 film is discussed in detail. Based on the newly gained knowledge of mechanism and its unique properties, fullerene has shown huge potential as a solid lubricant on various kinds of substrates.
Nanostructured ZnO materials have been studied extensively because of their functional properties. This paper presents a composite material of zinc oxide quantum dots (ZnO QDs) and porous carbon using a one-step carbonization process. The direct carbonization of a metal–organic complex generates mesostructured porous carbon with a homogeneous distribution of ZnO QDs. The structural and morphological properties are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The resulting ZnO QDs@porous carbon composite delivers a high specific capacity of 990 mAh g−1 at 100 mA g−1, 357 mAh g−1 at 2 A g−1, and high reversibility when evaluated as an anode for lithium ion batteries.
Numerous studies have addressed the commercial viability of lithium–air batteries (LABs). However, the high reactivity of Li with air moisture and CO2 has hindered the broad applicability of LABs. In this study, lithium-protective hybrid lithium–air batteries (HLABs) were fabricated with Super P (SP) and composites of fluorinated carbon ( CFx), MoS2, and WS2 as the cathodes. Subsequently, their potential use as a power source for the next generation of defense technologies was investigated. It was observed that a single cell HLAB with the SP-CFx composite cathode exhibited a specific capacity of 893 mAhg− 1 cathode. In comparison, a Tomcell with the SP cathode demonstrated a specific capacity of 465 mAhg− 1 cathode when discharged. The cells with SP-MoS2 and SP-WS2 cathode yielded specific capacities of 357 and 386 mAhg− 1 cathode, respectively. The improved performance of the SP-CFx cell can be attributed to synergistic effects of lithium–air cell and lithium battery reactions between CFx and SP. To assess all functionalities of the SP-CFx HLAB, lithium-protective HLABs were fabricated and discharged in air. To operate the lithium–air battery in air, pure lithium metal was sealed with solid electrodes (lithium-ion conducting glass–ceramics (LICGC)) and a buffer electrolyte (1 M LiFTSI in TEGDME) was applied. The SP-CFx cell was discharged for 25 days in air, greatly exceeding the 72 h requirement for the next-generation soldier power systems. These results demonstrate significant potential for HLABs to be used as a pioneering power source in nextgeneration energy-independent tactical defense units.