C — Open Access Journal

Graphene is a highly studied material due to its unique electrical, optical, and mechanical properties. Graphene is widely applied in the field of energy such as in batteries, supercapacitors, and solar cells. The properties of graphene can be further improved by making nanocomposites with conducting polymers. In this work, graphene oxide nanoribbons (GONRs) were synthesized by unzipping multiwall carbon nanotubes. Graphene nanoribbons were used to make nanocomposites with polypyrrole for energy storage applications. The synthesized nanocomposites were structurally and electrochemically characterized to understand their structure and electrochemical properties. The electrochemical characterizations of these nanocomposites were carried out using cyclic voltammetry. The specific capacitance of the nanocomposites was observed to decrease with increasing scan rates. The highest specific capacitance of 2066 F/g was observed using cyclic voltammetry for the optimized nanocomposite of GONR and polypyrrole. Our study suggests that the electrochemical properties of graphene or polypyrrole can be improved by making their composites and that they could be successfully used as electrode materials for energy storage applications. This study can also be extended to the self-assembly of other conducting polymers and graphene nanoribbons through a simple route for various other applications. Full article

Advances in wearable, highly sensitive and multifunctional strain sensors open up new opportunities for the development of wearable human interface devices for various applications such as health monitoring, smart robotics and wearable therapy. Herein, we present a simple and cost-effective method to fabricate a multifunctional strain sensor consisting of a skin-mountable dry adhesive substrate, a robust sensing component and a transdermal drug delivery system. The sensor has high piezoresisitivity to monitor real-time signals from finger bending to ulnar pulse. A transdermal drug delivery system consisting of polylactic-co-glycolic acid nanoparticles and a chitosan matrix is integrated into the sensor and is able to release the nanoparticles into the stratum corneum at a depth of ~60 µm. Our approach to the design of multifunctional strain sensors will lead to the development of cost-effective and well-integrated multifunctional wearable devices. Full article

Several crucial problems, such as rapid population growth and extended demands for food, water and fuels, could lead to a severe lack of clean water and an energy crisis in the coming decade. Therefore, low-cost and highly-efficient technologies related to filtration of alternative water supplies (e.g., purification of wastewater and water-rich liquids) and advanced energy storage (e.g., supercapacitors) could play a crucial role to overcome such challenges. A promising class of solid materials for these purposes is exfoliated graphene, and more specifically, its nanoporous forms that exhibit large specific surface areas and pore volumes. In the current work, two plasma-exfoliated graphene-based materials with distinctive morphological and porosity features, including non-porous and low-specific surface area platelets versus nanoporous and high-specific surface area flakes, were tested as filters for water purification purposes (i.e., decolourization and deacidification) and as electrodes for supercapacitors (i.e., ion electrosorption). The findings of this study suggest that a nanoporous and large specific surface area graphene-based material promotes the water purification behaviour by removing contaminants from water-based solutions as well as the energy storage performance by confining ions of aqueous electrolytes. Full article

Magnesium oxide (MgO)-templated nitrogen (N)-doped mesoporous carbons were prepared by using polyvinylpyrrolidone (PVP) as a raw material and magnesium lactate (Mglac) as a precursor for the MgO template to examine the influence of heating temperature and MgO precursor (magnesium acetate was used in similar previous studies) on the pore size and nitrogen content. The MgO-templated carbon was obtained by heating the PVP/Mglac mixture in an inert atmosphere followed by an acid treatment for MgO removal. The mesopore size of the carbons was approximately 4 nm regardless of heating temperature, corresponding to the crystallite size of the MgO template estimated via X-ray diffraction. This indicates that the mesopore of approximately 4 nm was generated using the MgO template. However, larger pores were also found to exist. This result indicates that the larger pores generated through processes other than the MgO templating, likely the thermal decomposition of PVP, are contained in the templated carbon. The volume of the larger pores and the specific surface area increased with increasing heating temperature. The nitrogen content of the carbon decreased as the heating temperature was increased, but it was found to be irrelevant to the MgO precursor. Full article

In our publication from eight years ago (Kogan, E. 2011, vol. 84, p. 115119), we calculated Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between two magnetic impurities adsorbed on graphene at zero temperature. We show in this short paper that the approach based on Matsubara formalism and perturbation theory for the thermodynamic potential in the imaginary time and coordinate representation which was used then, can be easily generalized, and calculate RKKY interaction between the magnetic impurities at finite temperature. Full article

A novel bio-based polyol was synthesized using corn oil and 2-mercaptoethanol via thiol-ene reaction as an alternative to petroleum-based polyol for the synthesis of polyurethane foams. The polyol was analyzed using wet chemical techniques to obtain hydroxyl number and viscosity. Infrared spectroscopy and gel permeation chromatography were used to confirm the structural properties of the foams. Flame-retardant polyurethane foams were prepared by the addition of different concentrations of dimethyl methyl phosphonate (DMMP) in final foam composition. The effect of DMMP on the thermo-mechanical properties of the polyurethane foams was analyzed. The TGA analysis showed improved stability of the final char with addition of DMMP in the foams. All the foams maintained a well-defined cellular structure and over 95% of closed cell content. The horizontal burning test showed reduced burning time and weight loss from 115 s and 38 wt.% for the neat foams, to 3.5 s and 5.5 wt.% for DMMP-containing foams (1.94 wt.% P). The combustion test using cone calorimeter showed a considerable reduction in heat release rate and total heat release. Thus, our study shows that corn-oil based polyol can be used to produce renewable polyol for industrially producible rigid polyurethane foams. The addition of a small amount of DMMP could result in a significant reduction in the flame-retardant properties of the polyurethane foams. Full article

In the present article, we describe the use of highly fluorescent carbon dots (CDs) for the preparation of an effective water-based carbon dot ink (CD-ink) for gravure printing. Carbon dots were prepared hydrothermally from citrate and triethylenetetramine, and mixed properly with certain resins that are used in gravure inks. The as-produced CD gravure ink was used successfully for printing high quality fluorescent images. Full article

A diamond-like carbon (DLC) film, coated on a AISI420-J2 stainless steel substrate and vertically aligned graphite (VAG), was structured by high-density plasma oxidation to work as a DLC-punch for micro-stamping and DLC-nozzle array for micro-dispensing, in addition to acting as a copper-plated thermal spreader, respectively. Thick DLC films were micro-patterned by maskless lithography and directly plasma-etched to remove the unmasked regions. Thick VAG (Ca plates were micro-patterned by screen-printing and selectively etched to activate the surface. Raman spectroscopy as well as electric resistivity measurement proved that there was no degradation of VAG by this surface activation. Wet plating was utilized to prove that copper wettability was improved by this surface treatment. Full article

Iodine and methylene blue adsorption properties of the high surface area nanoporous carbon materials derived from agro-waste and rice husk is reported. Rice husk was pre-carbonized at 300 °C in air followed by leaching out the silica nanoparticles by extraction with sodium hydroxide solution. The silica-free rice husk char was mixed with chemical activating agents sodium hydroxide (NaOH), zinc chloride (ZnCl₂), and potassium hydroxide (KOH) separately at a mixing ratio of 1:1 (wt%) and carbonized at 900 °C under a constant flow of nitrogen. The prepared carbon materials were characterized by scanning electron microscopy (SEM), Fourier transformed-infrared spectroscopy (FT-IR), powder X-ray diffraction (pXRD), and Raman scattering. Due to the presence of bimodal micro- and mesopore structures, KOH activated samples showed high specific surface area ca. 2342 m²/g and large pore volume ca. 2.94 cm³/g. Oxygenated surface functional groups (hydroxyl, carbonyl, and carboxyl) were commonly observed in all of the samples and were essentially non-crystalline porous particle size of different sizes (<200 μm). Adsorption study revealed that KOH activated samples could be excellent material for the iodine and methylene blue adsorption from aqueous phase. Iodine and methylene blue number were ca. 1726 mg/g and 608 mg/g, respectively. The observed excellent iodine and methylene blue adsorption properties can be attributed to the well-developed micro- and mesopore structure in the carbon material. This study demonstrates that the agricultural waste, rice husk, and derived nanoporous carbon materials would be excellent adsorbent materials in water purifications. Full article

The novel tubular carbon membranes produced from natural materials are, for the first time, reported. The novelty of this idea is to use natural rattans as precursors for making carbon membranes to address the challenges of cellulose polymers. The rattan precursors were carbonized to present evenly distributed channels inside the tubular carbon membranes. Each channel has an inner diameter of 2 × 10⁻⁴ m with a dense-selective inner layer and a porous outer layer. Future work on selection of suitable rattans, proper pre-treatment, carbon structure tailoring can be conducted to open a new research field of carbon membranes/materials. Full article

Hydrogenated amorphous carbon (a-C:H) films have attracted much attention, because of their excellent physical and chemical properties, such as high mechanical hardness, chemical robustness, a wide variety of optical bandgaps, and so forth. Although an ion bombardment energy has been regarded as essential in the well-know subplantation model, it alone is inadequate especially in complicated reactions of a plasma-enhanced chemical vapor deposition process. In this study, an ion bombardment energy flux (Γ_Ei) was proposed as a crucial factor to determine chemical compositions and structures of a-C:H films. To obtain the amounts of Γ_Ei, electron densities, hydrogen (H) excitation temperatures, and negative direct current (DC) self-bias voltage (-V_DC) were measured. The deposition rate increased, and sp²-C clusters incorporation was induced by the Γ_Ei. With increasing Γ_Ei, photoluminescence (PL) backgrounds in Raman spectra decreased, while spin densities in electron spin resonance (ESR) measurements increased. These results suggested the H content of a-C:H film decreased depending on the amount of Γ_Ei. The Γ_Ei is one of the crucial factors to determine the properties of the a-C:H films. Full article

Hydrogen peroxide (H₂O₂) reactions on platinum nanoparticle-decorated carbon nanowalls (Pt-CNWs) under potential applications were investigated on a platform of CNWs grown on carbon fiber paper (CFP) using plasma-enhanced chemical vapor deposition. Through repeated cyclic voltammetry (CV), measurements of 1000 cycles using the Pt-CNW electrodes in phosphate-buffered saline (PBS) solution with 240 μM of H₂O₂, the observed response peak currents of H₂O₂ reduction decreased with the number of cycles, which is attributed to decomposition of H₂O₂. After CV measurements for a total of 3000 cycles, the density and height of CNWs were reduced and their surface morphology changed. Energy-dispersive X-ray (EDX) compositional mapping revealed agglomeration of Pt nanoparticles around the top edges of CNWs. The degradation mechanism of Pt-CNWs under potential application with H₂O₂ is discussed by focusing on the behavior of OH radicals generated by the H₂O₂ reduction. Full article

Graphene oxide (GO) is conveniently prepared from expandable graphite using a simplified Hummers’ method. The product is thoroughly characterized by usual techniques (UV-vis, Fourier-transform infrared (FTIR) and Raman spectroscopies, zeta potential, electron microscopy, X-ray diffraction, nitrogen adsorption) to confirm the success of synthesis. Positron annihilation lifetime spectroscopy (PALS) is then used to extract information on the microenvironment in between the layers of graphene oxide. Full article

Deep saline reservoirs have the highest volumetric CO₂ storage potential, but drying and salt precipitation during CO₂ injection could severely impair CO₂ injectivity. The physical mechanisms and impact of salt precipitation, especially in the injection area, is still not fully understood. Core-flood experiments were conducted to investigate the mechanisms of external and internal salt precipitation in sandstone rocks. CO₂ Low Salinity Alternating Gas (CO₂-LSWAG) injection as a potential mitigation technique to reduce injectivity impairment induced by salt precipitation was also studied. We found that poor sweep and high brine salinity could increase salt deposition on the surface of the injection area. The results also indicate that the amount of salt precipitated in the dry-out zone does not change significantly during the drying process, as large portion of the precipitated salt accumulate in the injection vicinity. However, the distribution of salt in the dry-out zone was found to change markedly when more CO₂ was injected after salt precipitation. This suggests that CO₂ injectivity impairment induced by salt precipitation is probably dynamic rather than a static process. It was also found that CO₂-LSWAG could improve CO₂ injectivity after salt precipitation. However, below a critical diluent brine salinity, CO₂-LSWAG did not improve injectivity. These findings provide vital understanding of core-scale physical mechanisms of the impact of salt precipitation on CO₂ injectivity in saline reservoirs. The insight gained could be implemented in simulation models to improve the quantification of injectivity losses during CO₂ injection into saline sandstone reservoirs. Full article

Carbon nanotubes (CNTs) are known as nano-architectured allotropes of carbon, having graphene sheets that are wrapped forming a cylindrical shape. Rolling of graphene sheets in different ways makes CNTs either metals or narrow-band semiconductors. Over the years, researchers have devoted much attention to understanding the intriguing properties CNTs. They exhibit some unusual properties like a high degree of stiffness, a large length-to-diameter ratio, and exceptional resilience, and for this reason, they are used in a variety of applications. These properties can be manipulated by controlling the diameter, chirality, wall nature, and length of CNTs which are in turn, synthesis procedure-dependent. In this review article, various synthesis methods for the production of CNTs are thoroughly elaborated. Several characterization methods are also described in the paper. The applications of CNTs in various technologically important fields are discussed in detail. Finally, future prospects of CNTs are outlined in view of their commercial applications. Full article

Carbon blacks are an extensively used manufactured product. There exist different grades by which the carbon black is classified, based on its purpose and end use. Different properties inherent to the various carbon black types are a result of their production processes. Based on the combustion condition and fuel used, each process results in a carbon black separate from those obtained from other processes. These carbons differ in their aggregate morphology, particle size, and particle nanostructure. Nanostructure is key in determining the material’s behavior in bulk form. A variety of carbon blacks have been analyzed and quantified for their lattice parameters and structure at the nanometer scale, using transmission electron microscopy and custom-developed fringe analysis algorithms, to illustrate differences in nanostructure and their potential relation to observed material properties. Full article

In this study, hydrophilic magnetic nanoparticles were synthesized by green routes using a methanolic extract of Rubus ulmifolius Schott flowers. The prepared magnetic nanoparticles were coated with carbon-based shell for drug delivery application. The nanocomposites were further chemically functionalized with nitric acid and, sequentially, with Pluronic^® F68 (CMNPs-plur) to enhance their colloidal stability. The resulting material was dispersed in phosphate buffer solution at pH 7.4 to study the Doxorubicin loading. After shaking for 48 h, 99.13% of the drug was loaded by the nanocomposites. Subsequently, the drug release was studied in different working phosphate buffer solutions (i.e., PB pH 4.5, pH 6.0 and pH 7.4) to determine the efficiency of the synthesized material for drug delivery as pH-dependent drug nanocarrier. The results have shown a drug release quantity 18% higher in mimicking tumor environment than in the physiological one. Therefore, this study demonstrates the ability of CMNPs-plur to release a drug with pH dependence, which could be used in the future for the treatment of cancer "in situ" by means of controlled drug release. Full article

Transmission electron microscopy and neutron or X-ray diffraction are powerful techniques available today for characterization of the structure of various carbon materials at nano and atomic levels. They provide complementary information but each one has advantages and limitations. Powder X-ray or neutron diffraction measurements provide structural information representative for the whole volume of a material under probe but features of singular nano-objects cannot be identified. Transmission electron microscopy, in turn, is able to probe single nanoscale objects. In this review, it is demonstrated how transmission electron microscopy and powder X-ray and neutron diffraction methods complement each other by providing consistent structural models for different types of carbons such as carbon blacks, glass-like carbons, graphene, nanotubes, nanodiamonds, and nanoonions. Full article