An Au/K bicatalyst-assisted chemical vapor deposition process using C2H2(g) to grow high-density carbon nanocoils (CNCs) uniformly on the fibers in carbon fiber cloth substrates three-dimensionally was developed. An as-deposited substrate (2.5 × 1.0 cm2) showed a high electrochemical active surface area (16.53 cm2), suggesting its potential usefulness as the electrode in electrochemical devices. The unique one-dimensional (1D) helical structure of the CNCs shortened the diffusion pathways of the ions in the electrolyte and generated efficient electron conduction routes so that the observed serial resistance R s was low (3.7 Ω). By employing two-electrode systems, a liquid-state supercapacitor (SC) in H2SO4(aq) (1.0 M) and a solid-state SC with a polypropylene (PP) separator immersed in H2SO4(aq) (1.0 M)/polyvinylalcohol were assembled and investigated by using CNC-based electrodes. Both devices exhibited approximate rectangular shape profiles in the cyclic voltammetry measurements at various scan rates. The observations indicated their electric double-layer capacitive behaviors. From their galvanostatic charge/discharge curves, the specific capacitances of the liquid SC and the solid SC were measured to be approximately 137 and 163 F/g, respectively. In addition, the solid-state CNC-based SC possessed excellent energy density (15.3 W h/kg) and power density (510 W/kg). The light weight solid SC (0.1965 g, 2.5 × 1.0 cm2) was bendable up to 150° with most of the properties retained.

Hydrogen production by water splitting and the removal of aqueous dyes by using a catalyst and solar energy are an ideal future energy source and useful for environmental protection. Graphitic carbon nitride can be used as the photocatalyst with visible light irradiation. However, it typically suffers from the high recombination of carriers and low electrical conductivity. Here, we have developed a facile mix-thermal strategy to prepare carbon black-modified graphitic carbon nitrides, which possess high electrical conductivity, a wide adsorption range of visible light, and a low recombination rate of carriers. With the help of carbon black, highly crystallized graphitic carbon nitrides with built-in triazine and heptazine heterojunctions are obtained. Improved photocatalytic activities have been achieved in carbon black-modified graphitic carbon nitride. The dye removal rate can be three times faster than that of pristine graphitic carbon nitride and the photocatalytic H2 generation is 234 μmol h-1 g-1 under visible light irradiation.

Nitric oxide can be removed from flue gas by catalytic oxidation of NO to NO2, followed by dissolution of NO2 in water. The work presented here includes catalytic NO oxidation by activated carbons (ACs) at atmospheric and elevated pressures under dry and wet conditions at ambient temperature. The AC samples had different physicochemical characteristics including surface areas of ∼400-1600 m2/g and micropore volumes of ∼0.2-0.6 cm3/g while having different surface chemistries. Dry tests indicated that introducing nitrogen functionalities or coating with pyrolytic carbon could enhance the catalytic activity of AC for NO oxidation. Nitric oxide concentration profiles from the oxidation experiments under dry conditions showed maximum values after 5-15.5 h of testing and a steady-state condition after ∼12-30 h and that a major release of NO2 began after reaching the maximum values in the NO concentration. Adsorption profiles showed a high rate of NO x adsorption during the early hours of these experiments, and this rate decreased almost exponentially to a near-zero value. A near-complete catalytic conversion was achieved for NO oxidation at 120 psig under dry conditions, substantially higher than the 62% value of the noncatalytic NO oxidation at 217 psig. The wet trickle-bed experiments revealed that an inert packing material with a high external surface was a more suitable option than the ACs for NO oxidation in a wet trickle-bed system, even for ACs that exhibited high catalytic reactivity under dry conditions. Noncatalytic NO oxidation in the trickle-bed system was enhanced by the higher gas-liquid contact surface of the packing material for NO2 dissolution in water. Complete wetting of the hydrophilic AC or the presence of water vapor in the gas in contact with the surface of the superhydrophobic AC could eliminate or drastically reduce the catalytic activity of the AC for NO oxidation.

Tuning interactions at the interfaces in carbon fiber (CF)-reinforced polymer composites necessitates the implementation of CF surface modification strategies that often require destructive environmentally unfriendly chemistries. In this study, interfacial interactions in cellulose-based composites are tailored by means of a mussel-inspired adhesive polydopamine (PDA) coating, being inherently benign for the environment and for the structure of CFs. The step-by-step growth of PDA was followed by increasing treatment time leading to a hydrophilic PDA-coated surface, presumably via surface-based polymerization mechanisms attributed to strong π-π stacking interactions. Although PDA deposition led to an initial increase in the interfacial shear strength (IFSS) (5 h), it decreased at a longer reaction time (24 h), the formation of weakly attached PDA particles on the coated surface can possibly lie behind the latter phenomenon. Nevertheless, the mechanical properties of the prepared short CF-reinforced composite were improved (tensile strength increased ∼12% compared to the unmodified surface) with decreasing IFSS owing to the particular morphological design, resulting in longer fiber segments. Our study underlines the importance of the morphological design at the interface and considers PDA as a promising bioinspired material to tailor interfacial interactions.

The development of inexpensive and environmentally friendly graphene-like carbon is critical for its integration into industrial products. This work highlights the production of graphene-like carbon structures from calcium hydroxide. The chemical vapor deposition conditions to grow graphitic carbon on a calcium hydroxide catalyst are reported. Acetylene, steam, and calcium hydroxide are used to grow a crumpled carbon morphology. The crumpled carbon resulted in a high surface area of 1276 m2/g and high electrical conductivity (>105 S/m). Additionally, the significance and origin of the C 1s X-ray photoelectron spectroscopy (XPS) π-π* plasmon loss peak as it is related to high electrical conductivity is reported. A unique mechanism for the catalytic process involving calcium acetylide is proposed. Several deposition times, steam concentration, and catalyst morphology were tested to synthesize a variety of carbon morphologies from calcium-based materials. Crumpled carbon, hollow nanospheres, bamboo-like carbon nanotubes, multi-walled carbon nanotubes, and graphene fiber morphologies were all formed using calcium-based catalysts. Multiple reaction conditions, a scaled reaction (300 g), and catalyst recyclability were investigated. Calcium-based materials were then used as catalysts for the growth of other graphene-like carbons.

In this study, Liquidambar formosana tree leaves have been used as a renewable biomass precursor for preparing porous carbons (PCs). The PCs were produced by pyrolysis of natural waste of leaves after 10% KOH activation under a nitrogen atmosphere and characterized by a variety of state-of-the-art techniques. The PCs possess a large surface area, micro-/mesoporosity, and functional groups on its surface. A glassy carbon electrode modified with high PCs was explored as an efficient binder-free electrocatalyst material for the voltammetric determination of nitro isomers such as 3-nitroaniline (3-NA) and 4-nitroaniline (4-NA). Under optimal experimental conditions, the electrochemical detection of 3-NA and 4-NA was found to have a wide linear range of 0.2-115.6 and 0.5-120 μM and a low detection limit of 0.0551 and 0.0326 μM, respectively, with appreciable selectivity. This route not only enhanced the benefit from biomass wastes but also reduced the cost of producing electrode materials for electrochemical sensors. Additionally, the sensor was successfully applied in the determination of nitro isomers even in the presence of other common electroactive interference and real samples analysis (beverage and pineapple jam solutions). Therefore, the proposed method is simple, rapid, stable, sensitive, specific, reproducible, and cost-effective and can be applicable for real sample detection.

Fullerene cages are known as being able to participate in radical initiated copolymerization reactions with vinyl monomers for polymer-functionalized fullerenes. In this work, poly(N-vinylcarbazole) (PVK) was selected as a representative of electronic polymers in the functionalization of fullerene C60 by the same copolymerization reaction to yield the PVK-C60. Similarly found was that small carbon nanoparticles could also participate in the same copolymerization reaction for the nanoparticles to be surface-functionalized and -passivated by the attached PVK polymers, which are structurally adhering to the general definition on carbon dots (CDots), thus PVK-CDots. In the comparison between PVK-CDots and PVK-C60, the former was found to be more absorptive and therefore more effective in photon harvesting across the visible spectral region and also brightly fluorescent, orders of magnitude more so than the latter. Similar to the PVK-C60 and C60 cages in general, the PVK-CDots exhibited significant photoinduced electron accepting characteristics and, at the same time, also extraordinary electron donating abilities that are not available to fullerenes. Because fullerene-based composites with electronic polymers including PVK have found significant applications in optoelectronic devices and systems, the prospect of CDots represented by the PVK-CDots for similar purposes is discussed.

The oxygen evolution reaction (OER) and the hydrogen evolution reaction occurred at the anode and cathode, which depends on the electronic structure, morphology, electrochemically active surface area, and charge-transfer resistance of the electrocatalyst. Transition metals like cobalt, nickel, and iron have better OER and oxygen reduction reaction activities. At the same time, transition-metal oxide/carbon hybrid has several applications in electrochemical energy conversion reactions. The rich catalytic site of transition metals and the excellent conductivity of carbon material make these materials as a hopeful electrocatalyst in OER. Carbon-incorporated LaFe0.8Co0.2O3 was prepared by a simple solution combustion method for the development of the best performance of the electrocatalyst. The catalyst can deliver 10 mA/cm2 current density at an overpotential of 410 mV with better catalytic stability. The introduction of carbon material improves the dispersion ability of the catalyst and the electrical conductivity. The Tafel slope and onset potential of the best catalyst are 49.1 mV/dec and 1.55 V, respectively.

Heat dissipation problem is the primary factor restricting the service life of an electronic component. The thermal conductivity of materials has become a bottleneck that hinders the development of the electronic information industry (such as light-emitting diodes, 5G mobile phones). Therefore, the research on improving the thermal conductivity of materials has a very important theoretical value and a practical application value. Whether the thermally conductive filler in polymer composites can form a highly thermal conductive pathway is a key issue at this stage. The carbon fiber/carbon felt (CF/C felt) prepared in the study has a three-dimensional continuous network structure. The nickel-coated carbon fiber/carbon felt (CF/C/Ni felt) was fabricated by an electroplating deposition method. Three-dimensional CF/C/Ni/epoxy composites were manufactured by vacuum-assisted liquid-phase impregnation. By forming connection points between the adjacent carbon fibers, the thermal conduction path inside the felt can be improved so as to improve the thermal conductivity of the CF/C/Ni/epoxy composite. The thermal conductivity of the CF/C/Ni/epoxy composite (in-plane K∥) is up to 2.13 W/(m K) with 14.0 wt % CF/C and 3.70 wt % Ni particles (60 min electroplating deposition). This paper provides a theoretical basis for the development of high thermal conductivity and high-performance composite materials urgently needed in industrial production and high-tech fields.

A novel, one-step protocol for the selective synthesis of W2C nanoparticles from phosphotungstic acid (H3PW12O40), a low-cost and commercially available tungsten compound, was developed. The nanoparticles had diameters of 1-50 nm and were dispersed on a carbon substrate. The W2C nanoparticles were prepared by a simple operation sequence, involving impregnation of carbon black with H3PW12O40 followed by calcination at 1000 °C. X-ray diffraction study revealed the selective formation of the W2C phase in the samples prepared, whereas the tungsten carbide (WC) phase was present in the control prepared from H2WO4. Stable W2C nanoparticles were obtained using this method owing to the presence of phosphate at the interfaces between the W2C nanoparticles and the carbon substrates, which inhibited the diffusion of carbon atoms from the carbon substrates to the W2C nanoparticles, leading to the formation of WC. The W2C nanoparticles prepared showed an excellent catalytic activity for the hydrogen evolution reaction (HER), with low Tafel slopes of ∼50 mV/decade. The HER catalytic activity was notably high, being comparable to that of MoS2, which is a promising alternative to Pt. The present method can potentially be applied to produce highly effective, low-cost, Pt-free electrocatalysts for the HER.

We demonstrate a new approach for the unzipping of single-walled carbon nanotube (SWCNT) in an aqueous solution using the transition metal complex PdCl4 2- as a sacrificial chemical scissor and the growth of graphitic-carbon-coated Pd nanoparticles for the electrocatalytic oxidation of formic acid. The chemical unzipping and the growth of Pd nanoparticles involve the spontaneous electron transfer between SWCNT and the metal complex in an aqueous solution at room temperature. The redox potential for SWCNT and PdCl4 2- favors the spontaneous electron transfer reaction. The metal complex, in situ generated Pd nanoparticle, and oxygen play vital role in the oxidative unzipping of SWCNT. The Pd nanoparticles have an average size of 11 nm and are coated with the graphitic carbon layer of unzipped SWCNT (UzCNT-Pd). The Pd nanoparticle of the UzCNT-Pd hybrid material has a large electrochemically active surface area of 2.14 cm2. The hybrid material exhibits excellent electrocatalytic activity toward the oxidation of formic acid. The area and mass specific activity are significantly higher than those of the traditional carbon-supported Pd nanoparticle. The synergistic effect of graphitic carbon and the metal nanoparticles controls the catalytic activity. The confinement of Pd particles inside the graphitic carbon enhances the overall performance of the catalyst.

Carbon black nanospheres were turned to hollow carbon nanospheres (HCNs) and were used as the conductive additive in the cathodes of Li-ion batteries (LIBs). The results show that 10 wt % HCN added to the LIB cathodes, such as LiMn2O4, LiCoO2, LiNiMnCoO2, and LiFePO4, can provide significantly higher specific capacity than those using spherical carbon black. For example, a specific capacity of the LiMn2O4/HCN/PVDF cathode at 80:10:10 wt % with a bulk electrical conductivity of 1.07 Ω cm-2 is 125 mA h g-1 at 0.1 C from 3.0 to 4.3 V versus Li+/Li, which is 3.85-fold higher than that using Super P. The stability tested at 1 C remains over 95% after 800 charge/discharge cycles with 100% Coulombic efficiency. Replacing the present carbon black conductive additive with HCN in this work may be one of the best choices to increase the charge storage performance of LIBs rather than only focusing on the development of active cathode materials.

Electrode fouling is a major factor that compromises the performance of biosensors in in vivo usage. It can be roughly classified into (i) electrochemical fouling, caused by the analyte and its reaction products, and (ii) biofouling, caused by proteins and other species in the measurement environment. Here, we examined the effect of electrochemical fouling [in phosphate buffer saline (PBS)], biofouling [in cell-culture media (F12-K) with and without proteins], and their combination on the redox reactions occurring on carbon-based electrodes possessing distinct morphologies and surface chemistry. The effect of biofouling on the electrochemistry of an outer sphere redox probe, [Ru(NH3)6]3+, was negligible. On the other hand, fouling had a marked effect on the electrochemistry of an inner sphere redox probe, dopamine (DA). We observed that the surface geometry played a major role in the extent of fouling. The effect of biofouling on DA electrochemistry was the worst on planar pyrolytic carbon, whereas the multiwalled carbon nanotube/tetrahedral amorphous carbon (MWCNT/ta-C), possessing spaghetti-like morphology, and carbon nanofiber (CNF/ta-C) electrodes were much less seriously affected. The blockage of the adsorption sites for DA by proteins and other components of biological media and electrochemical fouling components (byproducts of DA oxidation) caused rapid surface poisoning. PBS washing for 10 consecutive cycles at 50 mV/s did not improve the electrode performance, except for CNF/ta-C, which performed better after PBS washing. Overall, this study emphasizes the combined effect of biological and electrochemical fouling to be critical for the evaluation of the functionality of a sensor. Thus, electrodes possessing composite nanostructures showed less surface fouling in comparison to those possessing planar geometry.

Due to increased populations, there is an increased demand for food; thus, battery electrode materials created from waste biomass provide an attractive opportunity. Unfortunately, such batteries rarely sustain capacities comparable to current state-of-the-art technologies. However, an anode synthesized from waste avocado seeds provides high cycling stability over 100 cycles and provides comparable capacity to graphite, around 315 mAh g-1 at 100 mA g-1 current density, and readily outperforms graphene in terms of both stability and capacity. This novel electrode provides such capacities as an amorphous carbon without the use of any additives or doped heteroatoms by utilizing capacitance-driven mechanisms to contribute to 54% of its lithium-ion storage. This allows the waste biomass-derived anode to overcome its low apparent diffusion coefficient of 4.38 × 10-11 cm2 s-1. By creating battery anodes from avocado seeds, waste streams can be redirected into creating valuable, renewable energy storage resources.

The increasing development of antibiotic resistance in bacteria has been a major problem for years, both in human and veterinary medicine. Prophylactic measures, such as the use of vaccines, are of great importance in reducing the use of antibiotics in livestock. These vaccines are mainly produced based on formaldehyde inactivation. However, the latter damages the recognition elements of the bacterial proteins and thus could reduce the immune response in the animal. An alternative inactivation method developed in this work is based on gentle photodynamic inactivation using carbon nanodots (CNDs) at excitation wavelengths λex > 290 nm. The photodynamic inactivation was characterized on the nonvirulent laboratory strain Escherichia coli K12 using synthesized CNDs. For a gentle inactivation, the CNDs must be absorbed into the cytoplasm of the E. coli cell. Thus, the inactivation through photoinduced formation of reactive oxygen species only takes place inside the bacterium, which means that the outer membrane is neither damaged nor altered. The loading of the CNDs into E. coli was examined using fluorescence microscopy. Complete loading of the bacterial cells could be achieved in less than 10 min. These studies revealed a reversible uptake process allowing the recovery and reuse of the CNDs after irradiation and before the administration of the vaccine. The success of photodynamic inactivation was verified by viability assays on agar. In a homemade flow photoreactor, the fastest successful irradiation of the bacteria could be carried out in 34 s. Therefore, the photodynamic inactivation based on CNDs is very effective. The membrane integrity of the bacteria after irradiation was verified by slide agglutination and atomic force microscopy. The method developed for the laboratory strain E. coli K12 could then be successfully applied to the important avian pathogens Bordetella avium and Ornithobacterium rhinotracheale to aid the development of novel vaccines.

This study reports usage of Mongolian anthracite-based porous activated carbons (PMACs), namely, PMAC 1/3 and PMAC 1/4 for model diesel fuel desulfurization, having 500 ppmw of dibenzothiophene (DBT) in n-heptane. Further, the effects of contact time, adsorbent dosage, and temperature on the adsorption capacity were studied systematically. The experimental adsorption isotherm results were well represented by the Sips isotherm for PMAC 1/3 and the dual site Langmuir isotherm for PMAC 1/4. The maximum DBT adsorption by PMAC 1/3 and PMAC 1/4 were 99.7 and 95.7%, respectively. The kinetics for the adsorption of DBT on PMACs follows the pseudo second order behavior. The Weber-Morris plot shows the multilinearity over the entire time range, suggesting that both the surface and pore diffusions control the adsorption. The values of boundary layer thickness for PMAC 1/4 and PMAC 1/3 were found to be 3.183 and 1.643, respectively. Thus, PMAC 1/4 possesses more surface diffusion control than PMAC 1/3. The changes in Gibbs free energy (ΔG°), entropy (ΔS°), and enthalpy (ΔH°) are negative, which confirms that the studied process is spontaneous and exothermic and possesses less randomness at the interface. Based on the Sips isotherm, single-stage batch-adsorber design was prepared for the adsorption of DBT onto PMAC 1/3.

Carbon dots, the celebrated green material among the nanocarbon family, are blessed with several interesting features like biocompatibility, solubility, tunable luminescence, and so forth. Herein, carbon dots derived from Mint leaf extract (M-CDs) via a green method are exploited for versatile applications as a biosensor, reductant, and biomarker. M-CDs are applied for fluorimetric sensing of biologically relevant folic acid through quenching response originating from the inner filter effect, with a limit of detection of 280 nM. The carbon dots were highly selective toward folic acid in a collection of 16 biomolecules. The specificity of carbon dots toward folic acid is explained based on the interaction between the two. Along with sensing, herein, we project M-CDs as a green reducing agent by demonstrating the reduction of Fe(III) and noble metal nanoparticle synthesis from their salt solutions. The particles are found to be significantly non-cytotoxic, as evident from the MTT assay performed on primary H8 cells. The application of M-CDs in multicolor imaging is also illustrated using HeLa cells.

Electronic waste management is one of the key challenges for the green revolution without affecting the environment. The wide use of printer devices has brought a horde of discarded waste toner, which release ∼6000 tons of processed carbon powder into the atmosphere every year that would essentially pollute the atmosphere. Here, we propose a one-step thermal conversion of waste toner powder into carbon/Fe3O4 nanocomposites for energy storage applications. Recovered toner carbon (RTC) and toner carbon calcined at 300 °C (RTC-300) were characterized using various analytical tools. From the FE-SEM analysis, the presence of carbon particles with uniformly decorated Fe3O4 nanoparticles was confirmed. RTC-300 carbon was used as an electrode material for supercapacitors, and it exhibited a high specific capacitance of 536 F/g at a current density of 3 A/g, which is almost six times higher than that of the commercial mesoporous graphitized carbon black. RTC-300 showed excellent electrochemical stability of 97% over 5000 cycles at a high current density of 20 A/g. The fabricated symmetric cell using RTC-300 electrode materials in an aqueous electrolyte with a cell voltage of 1.8 V delivered a high energy and high-power density of 42 W h/kg and 14.5 kW/kg, respectively. The fabricated device is stable up to 20,000 cycles at a high current density of 20 A/g with a loss of 23% capacitance.

We describe a one-pot synthesis method for carbon filament-supported mixed metal oxide nanoparticles. The thermal intracrystalline reaction of adamantanecarboxylate ions confined inside interlayer galleries of layered double hydroxide materials under a reducing atmosphere (H2) leads to carbon filaments forming in situ within the material. Raman spectroscopy and combined microscopy techniques show the formation of hybrid organic-inorganic carbon filaments with the mixed metal oxide particles interleaved.

The production of graphene films is of importance for the large-scale application of graphene-based materials; however, there is still a lack of an efficient and effective approach to synthesize graphene films directly on dielectric substrates. Here, we report the controlled growth of ultrathin carbon films, which have a similar structure to graphene, directly on silicon substrates in a process of seeded chemical vapor deposition (CVD). Crystalline silicon with a thermally grown 300 nm oxide layer was first treated with 3-trimethoxysilyl-1-propanamine (APS), which was used as an anchor point for the covalent deposition of small graphene flakes, obtained from graphite using the Hummers' method. Surface coverage of these flakes on the silicon substrate was estimated by scanning electron microscopy (SEM) to be around only 0.01% of the total area. By treating the covalently deposited graphene as seeds for CVD growth, the coverage was increased to >40% when using ethanol as the carbon source. Examination of the carbon thin films with SEM, X-ray photoelectron spectroscopy, and Raman spectroscopy indicated that they consist of domains of coherent, single-layer graphene produced by the coalescence of the expanding graphene islands. This approach potentially lends itself to the production of high-quality graphene films that may be suitable for device fabrication.