We benefit from various sensors in our daily life with or without being aware of them, and carbon materials are often used as the sensing materials. Here, carbon-based sensors, including their sensing possibilities, are reviewed by classifying the materials into fibrous (carbon nanotubes and nanofibers), graphene-related (graphene, reduced graphene oxide, graphene oxide) and porous (conventional activated carbons and carbon black). The sensors are also classified into chemical sensors, mechanical sensors and biosensors on the bases of their abilities to detect chemicals (inorganic gases, organic vapors), mechanical signals (stress, strain, pressure and temperature), and biological chemicals (such as glucose, protein, DNA, including solution pH). Among the numerous carbon materials, the graphene-related are the most important. The scientific background for the sensing properties of graphene synthesized either by CVD or cleaving natural graphite is presented. Reduced graphene oxide is a promising sensing material mainly because of its easy production, low-cost, and ability to be suspended to fabricate the device. In addition to its excellent properties, it can also be easily modified by functional groups on its surface.

In Japan, the tips of Japanese leek leaves are typically trimmed and discarded during harvesting, resulting in considerable waste. In this study, the discarded leaves were repurposed as a raw material for the production of activated carbon (AC). To prepare the AC, beet sugar syrup was added to precarbonized leaves, followed by carbonization and physical activation with CO₂ gas. The specific surface area, along with the micropore and mesopore volumes, increased as activation time increased. The maximum specific surface area was 1852.7 m²/g after 3 h of activation. The AC produced had a high adsorption capacity for p-cresol, with Langmuir adsorption isotherms indicating a maximum adsorption capacity of 401.5 mg/g—approximately 2.0 and 1.7 times higher than those of commercial coal-based and coconut shell ACs, respectively.

A method for mass-producing graphene without a substrate or catalyst has not yet been developed. Consequently, combined with the tendency of graphene to stack easily, there are currently no applications that effectively exploit its structure and functionality. We address these issues by investigating the preparation of graphene using hot isostatic pressing (HIP) and the mechanism of this process. We developed a method for mass-producing vapor-phase-grown graphene by first heating a resin material such as phenolic resin under conditions that control the amount of residual hydrogen and then treating the product with argon or nitrogen using HIP equipment. After heating, the resin powder changed to carbon powder containing small quantity of residual hydrogen and oxygen. In the HIP method, the carbonized powder generates hydrogen and hydrocarbons from inside the powder particles. These create a concentration gradient near the carbonized powder surface by hydrostatic pressure due to HIP, and a thermal chemical vapor deposition reaction occurs due to the heating, which results in the radial formation of flower-like graphene on the carbonized powder surface. The results show that in the formation of vapor-phase-grown carbon, when the HIP treatment temperature is 1300–1500 ℃, thin two-dimensional growth is preferred over three-dimensional growth, and graphene grows in the same manner as carbon nanotubes without a catalyst.

Weibull analysis is an effective method for examining the strength distribution of carbon fibers. However, prior studies have reported only the average strength and standard deviation (SD), which precludes the determination of the Weibull distribution. To address this limitation, this study proposes a method for estimating the Weibull parameters from average strength and SD data using the method of moments. The number of defects and their associated errors were derived from the tensile strength (mean±SD), and their validity was assessed. The results showed that the method of moments can be used to estimate the approximate number of defects and their errors from the tensile strength data of the fibers. The method allows the estimation of Weibull parameters from previously reported results, and may be beneficial for research and development that relies on existing literature. The number of tensile tests was also determined from these analyses.

In pursuit of an effective controlled drug release system, the development of a suitable carrier is crucial. Among many different materials, a combination of graphene oxide (GO) and a metal–organic framework (MOF) shows great potential. Although GO provides good water dispersibility and oxygen-containing functional groups, its drug-loading capacity is insufficient. Conversely, MOF has a tunable pore size and high drug-loading capacity, but suffers from low water solubility and instability in bodily fluids, which limits controlled drug release. Thus, the combined use of GO and MOF is explored to address these challenges. Here, a novel method involving hydrothermal synthesis and ball milling was used to create a nano-size MOF and GO composite (nanoMOF/GO), for use as a drug carrier. Piperine (PI), a hydrophobic drug, was selected for encapsulation, and its loading capacity and release in response to a pH change were evaluated. Results show a high drug loading because of the electrostatic interaction of nanoMOF and GO, forming new pores and binding sites. The release of PI was achieved at pH 5.5, with minimal release observed when using the MOF alone. Furthermore, the inclusion of GO suppressed premature release from the nanoMOF under neutral conditions. Overall, this study highlights the potential of the nanoMOF/GO composite as a promising nanocarrier for drug delivery.

Brown coal is characterized by a high moisture and volatile matter content, but its heating value per unit weight is low. To use it as a substitute fuel for bituminous coal, it must be dried and carbonized to increase its heating value to a level comparable to that of the bituminous variety. During this upgrading process, careful consideration must be given to its combustion efficiency while retaining a certain proportion of volatile matter. However, the upgraded coal containing volatile matter poses a considerable risk of spontaneous combustion, preventing long-distance transportation and long-term storage. This study proposes a straightforward method to suppress this spontaneous combustion by stabilizing the aliphatic hydrocarbons. Quantum chemical calculations have shown that the carboxyl and ester groups produced during the oxidation of methyl groups in the upgraded coal have a high chemical stability. Based on these results, Loy Yang coal, a representative brown coal from Victoria, Australia, was upgraded at 430 °C, and its oxidative behavior was evaluated using FT-IR, nuclear magnetic resonance, thermogravimetry/differential thermal analysis, and gas chromatography. The results confirmed that oxidizing the upgraded coal at 240 °C effectively reduced its tendency for spontaneous combustion.

To optimize the use of brown coal, methods for minimizing the spontaneous combustion of upgraded brown coal were investigated. Previous studies have shown that the controlled oxidation at 200–240 °C of Loy Yang coal from Australia, a typical brown coal, stabilized the functional groups of the coal which significantly reduced its ignition potential to the level of bituminous coal. However, the influence of the oxidation conditions on further reducing the spontaneous combustion potential of the upgraded coal was not thoroughly assessed. In this study, the exothermic reaction rate during the oxidation of upgraded Loy Yang coal was carefully examined. Its weight change and heat generation rates were measured during oxidation at temperatures between 140 °C and 300 °C, with O₂ concentrations of 1‒15 vol%, using thermogravimetry-differential scanning calorimetry. The exothermic reaction was identified as an apparent first-order reaction in the temperature range of 140–240 °C, and the heat generation rate was described by an Arrhenius-type equation. The activation energy was found to be approximately 60 kJ/mol, with the O₂ concentration affecting the frequency factor. Based on these results, a new equation was proposed to predict the oxidation conditions of the upgraded brown coal.

A small aperture, allowing the encapsulation of hydrofluoric acid (HF), was made in [60]fullerene. To create this structure, reductive decarbonylation was performed on an open [60]fullerene with a 13-atom ring aperture, resulting in two primary derivatives with 14-atom apertures. The chemical structure of the aperture was found to be critical in determining the selectivity between the two derivatives. Despite the reaction being performed at 180 °C in the presence of water, the products spontaneously allowed a water molecule to pass through the aperture. However, under milder conditions at 0 °C, HF was encapsulated in the cavity. The encapsulation of HF led to a distinct shifting of proton signals attributed to the translational movement of HF in the cavity, as predicted by theoretical calculations.

In this study, we investigated the ion conduction of protons and sulfate ions within various pore structures using an aqueous H₂SO₄ electrolyte. Proton conduction in aqueous electrolytes follows the Grotthuss mechanism, whereas sulfate ion conduction proceeds via the vehicle mechanism. These conduction mechanisms play a crucial role in the performance of electric double-layer capacitors, fuel cells, and related energy storage devices. Two redox-active materials, benzoquinone and 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) derivatives, undergo reversible redox reactions with protons and sulfate ions acting as counterions, respectively. These materials were hybridized into the pores of three porous carbons with varying pore structures and sizes. The two porous carbons are activated carbons, one containing only micropores and the other containing both micropores and mesopores. Additionally, a microporous carbon with three-dimensionally ordered and interconnected 1.2-nm micropores was used. The hybridized benzoquinone and TEMPO derivatives underwent reversible redox reactions within the pores, functioning as electrode materials in electrochemical capacitors. The reversible redox reactions involve the counterion diffusion of protons and sulfate ions within the pores of the porous carbons. The rate of these reversible redox reactions depended on the ion conduction within the pores. Ion conduction was assessed by examining the charge/discharge performance of the hybrids.