Search Results (58)

Carbon nano-onions (CNOs) were synthesized at ambient conditions using the wick-pyrolysis technique with ghee as a precursor. A high-purity copper substrate produced unique CNOs, differing from those obtained with other metals. To purify the nanoparticles, they underwent treatment with a solvent mixture of acetone and deionized water or were pyrolyzed at 1000 °C under nitrogen without a catalyst. Various characterization techniques, including X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), High-Resolution Transmission Electron Microscopy (HR-TEM), and Raman Spectroscopy, confirmed the successful formation of CNOs. Energy Dispersive Spectroscopy (EDS) and Elemental analysis (CHN) indicated the presence of oxygen in treated CNOs. X-ray photoelectron spectroscopy (XPS) revealed binding energies linked to C-O and C=O bonds. The average particle size was found to be 30–50 nm, with some agglomeration in pyrolyzed samples. A significant increase in surface area from 79.7 m²/g to 261.8 m²/g was observed, along with changes in pore radius and volume via Brunauer–Emmett–Teller (BET) analysis. Water contact angles on the CNO surface were measured at 125° and 138°, indicating hydrophobicity. Electrochemical tests on CNO-based composite electrodes yielded a specific capacitance of 109.7 F/g with 96% capacity retention over 5000 cycles. Full article

Developing effective metal-free electrocatalysts for acidic hydrogen evolution is challenging because both catalytic activity and electronic conductivity must be optimized simultaneously. Here, h-BN/carbon nano-onion (CNO) hybrid electrocatalysts were synthesized by integrating layered hexagonal boron nitride with conductive carbon nano-onions to generate accessible heterointerfaces for the hydrogen evolution reaction (HER). Structural characterization by XRD, SEM/TEM, and STEM-EDS confirmed intimate contact between h-BN sheets and quasi-spherical CNO domains. Similarly, XPS revealed B–N-rich frameworks with interfacial B–C/C–N surface environments and oxygen-associated defect sites. Among the prepared compositions, the h-BN/CNO20 eletrocatalyst exhibited the best apparent HER performance in 0.5 M H₂SO₄, delivering an overpotential of ~270 mV at 5 mA cm⁻² and a Tafel slope of 76 mV dec⁻¹, along with stable chronoamperometric behavior for 15 h. The improved electrocatalytic activity is due to the enhanced charge transport through the CNO network, suppression of h-BN restacking, increased exposure of interfacial sites, and charge redistribution across B–N/C heterojunctions. These findings identify h-BN/CNO20 as the optimum composition within this series and demonstrate that heterointerface engineering between boron nitride and curved graphitic nanocarbons is a promising strategy for developing metal-free HER electrocatalysts. However, further validation using a non-Pt counter electrode is necessary to confirm intrinsic catalytic activity. Full article

Graphitic nanomaterials have emerged as foundational components in nanoscience owing to their exceptional electrical, mechanical, and chemical properties, which can be tuned by controlling dimensionality and structural order. From zero-dimensional (0D) quantum dots, carbon nano-onions, and nanodiamonds to one-dimensional (1D) nanoribbons, two-dimensional (2D) nanowalls, and three-dimensional (3D) graphene foams, these architectures underpin advancements in catalysis, energy storage, sensing, and electronic technologies. Among various synthesis routes, chemical vapor deposition (CVD) provides unmatched versatility, enabling atomic-level control over carbon supply, substrate interactions, and plasma activation to produce well defined graphitic structures directly on functional supports. This review presents a comprehensive, dimension-resolved overview of CVD-derived graphitic nanomaterials, examining how process parameters such as precursor chemistry, temperature, hydrogen etching, and template design govern nucleation, crystallinity, and morphological evolution across 0D to 3D hierarchies. Comparative analyses of Raman, XPS, and XRD data are integrated to relate structural features with growth mechanisms and functional performance. By connecting mechanistic principles across dimensional scales, this review establishes a unified framework for understanding and optimizing CVD synthesis of graphitic nanostructures. It concludes by outlining a path forward for improving how CVD-grown carbon nanomaterials are made, monitored, and integrated into real devices so these can move from lab-scale experiments to practical, scalable technologies. Full article

When exposed to high contact pressure and shear conditions, the sliding and/or rolling contact interfaces of moving mechanical systems can experience significant friction and wear losses, thereby impairing their efficiency, reliability, and environmental sustainability. Traditionally, these losses have been minimized using high-performance solid and liquid lubricants or surface engineering techniques like physical and chemical vapor deposition. However, increasingly harsh operating conditions of more advanced mechanical systems (including wind turbines, space mechanisms, electric vehicle drivetrains, etc.) render such traditional methods less effective or impractical over the long term. Looking ahead, an emerging and complementary solution could be tribocatalysis, a process that spontaneously triggers the formation of nanocarbon-based tribofilms in situ and on demand at lubricated interfaces, significantly reducing friction and wear even without the use of high-performance additives. These films often comprise a wide range of amorphous or disordered carbons, crystalline graphite, graphene, nano-onions, nanotubes, and other carbon nanostructures known for their outstanding friction and wear properties under the most demanding tribological conditions. This review highlights recent advances in understanding the underlying mechanisms involved in forming these carbon-based tribofilms, along with their potential applications in real-world mechanical systems. These examples underscore the scientific significance and industrial potential of tribocatalysis in further enhancing the efficiency, reliability, and environmental sustainability of future mechanical systems. Full article

The electrochemical conversion of CO₂ into high-purity Graphene NanoCarbon (GNC) materials provides a compelling path to address climate change while producing economically valuable nanomaterials. This work presents the progress and prospects of new large-scale syntheses of GNC allotropes via the C2CNT (CO₂ to Carbon Nano Technology) process. The C2CNT molten carbonate electrolysis technique enables the formation of Carbon NanoTubes (CNTs), Magnetic CNTs (MCNTs), Carbon Nano-Onions (CNOs), Carbon Nano-Scaffolds (CNSs), and Helical CNTs (HCNTs) directly from atmospheric or industrial CO₂. We discuss the morphology control enabled through variations in electrolyte composition, temperature, current density, and nucleation additives. We present results from scaled operations reaching up to 1000 tons/year CO₂ conversion and propose design approaches to reach megaton scales to support climate mitigation and GNC mass production. The products demonstrate high crystallinity, as evidenced by Raman, XRD, SEM, and TGA analyses, and offer promising applications in electronics, construction, catalysis, and medical sectors. Full article

Printed electronics employ established printing methods to create low-cost, mechanically flexible devices including batteries, supercapacitors, sensors, antennas and RFID tags on plastic, paper and textile substrates. This review focuses on the specific contribution of screen printing to that landscape, examining how ink viscosity, mesh selection and squeegee dynamics govern film uniformity, pattern resolution and ultimately device performance. Recent progress in advanced ink systems is surveyed, highlighting carbon allotropes (graphene, carbon nano-onions, carbon nanotubes, graphite), silver and copper nanostructures, MXene and functional oxides that collectively enhance mechanical robustness, electrical conductivity and radio-frequency behavior. Parallel improvements in substrate engineering such as polyimide, PET, TPU, cellulose and elastomers demonstrate the technique’s capacity to accommodate complex geometries for wearable, medical and industrial applications while supporting environmentally responsible material choices such as water-borne binders and bio-based solvents. By mapping two decades of developments across energy-storage layers and functional electronics, the article identifies the key process elements, recurring challenges and emerging sustainable practices that will guide future optimization of screen-printing materials and protocols for high-performance, customizable and eco-friendly flexible devices. Full article

This paper reports several preliminary investigations concerning the relative humidity (RH) detection response of a chemiresistive sensor that uses a novel sensing layer based on pristine carbon nano-onions (CNOs) and polyvinyl alcohol (PVA) at a 1/1 and 2/1 w/w ratio. The sensing device, including a Si/SiO₂ substrate and gold electrodes, is obtained by depositing the CNOs–PVA aqueous suspension on the sensing structure by drop casting. The composition and morphology of the sensing film are explored by means of scanning electron microscopy, Raman spectroscopy, atomic force microscopy, and X-ray diffraction. The manufactured sensor’s room temperature RH detection performance is examined by applying a continuous flow of the electric current between the interdigitated electrodes and measuring the voltage as the RH varies from 5% to 95%. For RH below 82% (sensing layer based on CNOs–PVA at 1/1 w/w ratio) or below 50.5% (sensing layer based on CNOs–PVA at 2/1 w/w ratio), the resistance varies linearly with RH, with a moderate slope. The newly developed sensor, using CNOs–PVA at a 1:1 ratio (w/w), responded as well as or better than the reference sensor. At the same time, the recorded recovery time was about 30 s, which is half the recovery time of the reference sensor. Additionally, the changes in resistance (ΔR/ΔRH) for different humidity levels showed that the CNOs–PVA layer at 1:1 was more sensitive at humidity levels above 80%. The main RH sensing mechanisms considered and discussed are the decrease in the hole concentration in the CNOs during the interaction with an electron donor molecule, such as water, and the swelling of the hydrophilic PVA. The experimental RH detection data are analyzed and compared with the RH sensing results reported in previously published work on RH detectors employing sensing layers based on oxidized carbon nanohorns–polyvinylpirrolidone (PVP), oxidized carbon nanohorns–PVA and CNOs–polyvinylpyrrolidone. Full article

The conversion of biochar, the low value byproduct of pyrolysis bio-oil production from biomass multi-walled carbon nanotubes (MWCNTs) and carbon nanochains (CNCs), is reported. It is shown that biomass can be converted to long (>30 µm) carbon nanotubes with an anomalously deep (>280 nm) stacked-cup structure. A mechanism of the transformation that is consistent with previously reported graphitization of biochar, a “non-graphitizable” carbon, is proposed, suggesting the molten metal catalyst is absorbed into the biochar by capillary action, forming graphene walls as it percolates through pore structure. Graphite is formed when the diameter of the molten catalyst droplets is large (microns), while smaller droplets (submicron) form MWCNTs and still smaller (<100 nm) form CNCs. Branching in the biochar pore structure leads to subdivision of the catalyst droplets resulting in the progression from MWCNT to CNC formation. Very long MWCNTs (>50 µm) can be formed in the absence of CNCs by transforming lignite char rather than biochar, presumably due to the elimination of smaller branching pores during coalification. CNCs, in the absence of MWCNTs, can be formed in biochar by using low concentrations of catalyst nanoparticles formed by carbon thermal reduction of a metal salt during charring. The results presented suggest that developing methods to control the porosity of the char could yield the ability to rationally synthesize carbon nanotubes with control of length, breadth and wall thickness. Full article

Graphite made from coal will not only widen the graphite mineral resource, but also significantly improve the value of coal utilization. In this study, anthracite coal was heated in the temperature range of 500 to 2900 °C to study the size increase of nanometric graphite crystallites from anthracite to real graphite. The carbon content rapidly increases to 99.2% when heated from room temperature to 1600 °C, and then gradually increases to 100% when the treated temperature increases to 2900 °C. The FTIR results show that methyl, methylene, and aromatic hydrocarbon, preexisting in the raw anthracite, were preserved in the JZS-500 sample, but that when the treated temperature ≥ 1000 °C, these C-H bonds almost disappear. The basic structural units (nano graphitic carbon) grow into distorted columns, and the basic structural units and micro-columns re-oriented and coalesced to form local molecular oriented domains with the temperature increase from anthracite to JZS-1500. When the temperature ≥ 1600 °C, amorphous carbon, onion-like carbon, turbostratic layers, and graphitic carbon co-occur within the graphitized coals. At the sub-micron scale, carbonization is a homogenous process, whereas graphitization is a heterogenous process. The average graphite crystalline size (L_a, lateral extension; L_c, stacking height) rapidly increases as the treatment temperature increases from 1600 to 2300 °C. Three coal structural transformation stages were classified according to the nanometric carbon structural evolution with temperature. This study will contribute to the efficient and value-added utilization of coal to make graphite materials. Full article

Recent observations of superconductivity in low-dimensional systems composed of twisted, untwisted, or rhombohedral graphene have attracted significant attention. One-dimensional moiré superlattices and flat bands have interestingly been identified in collapsed chiral carbon nanotubes (CNTs), opening up new avenues for the tunability of the electronic properties in these systems. The nucleation of hexagonal moiré superlattices and other types of stacking faults has also been demonstrated in partially collapsed and uncollapsed carbon nano-onions (CNOs). Here, we report a novel investigation on the dynamics of stacking fault nucleation within the multilayered lattices of micrometer-scale vertically oriented films of multiwall CNTs (MWCNTs), resulting from the pyrolysis of molecular precursors consisting of ferrocene or dimethyl ferrocene, at low vapor flow rates of ~5–20 mL/min. Interestingly, local nucleation of moiré-like superlattices (as stacking faults) was found when employing dimethyl ferrocene as the pyrolysis precursor. The morphological and structural properties of these systems were investigated with the aid of scanning and transmission electron microscopies, namely SEM, TEM, and HRTEM, as well as X-ray diffraction (XRD) and Raman point/mapping spectroscopy. Deconvolution analyses of the Raman spectra also demonstrated a local surface oxidation, possibly occurring on defect-rich interfaces, frequently identified within or in proximity of bamboo-like graphitic caps. By employing high-temperature Raman spectroscopy, we demonstrate a post-growth re-graphitization, which may also be visualized as an alternative way of depleting the oxygen content within the MWCNTs’ interfaces through recrystallization. Full article

In this study, we employed a straightforward flame synthesis process to produce carbon soot containing carbon nano onions (CNOs) using easily accessible ghee oil as a precursor. The ghee oil, with a molecular composition rich in more than 50 carbon atoms, served as an effective source for generating CNOs. The synthesized CNO particles underwent comprehensive characterization through high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses, providing a detailed account of their physicochemical properties. In addition, we explored the direct deposition of CNOs on carbon fiber (CF) surfaces for 5 and 10 min via a soot deposition process. The resulting freeze–fracture images obtained from scanning electron microscope (SEM) offered insights into the morphology of the CNO-deposited CF. Our study aims to shed light on the potential applications of CNOs, focusing on their characterization and the possible benefits they may offer in diverse fields, including but not limited to enhancing interfacial bonding in thermoplastic composites. Full article

The use of carbon nanomaterials including fullerenes, carbon nanotubes, carbon nano-onions, carbon dots and carbon quantum dots for environmental applications has increased substantially. These nanoparticles are now used in the development of sensors and switches, in agriculture as smart fertilizers and in the biomedical realm for cancer therapy intervention, as antioxidants, in gene delivery and as theranostics. Here, we review the role of fullerenes as neuroprotectants. Their sp² hybridized architectures and ability to intervene in the soluble-to-toxic transformation of amyloidogenic trajectories is highlighted here, along with other physico–chemical properties that impact interventional efficacy. Also highlighted are drawbacks that need to be overcome and future prospects. Full article

With the existing pressure sensors, it is difficult to achieve the unification of wide pressure response range and high sensitivity. Furthermore, the preparation of pressure sensors with excellent performance for sleep health monitoring has become a research difficulty. In this paper, based on material and microstructure synergistic enhancement mechanism, a hybrid pressure sensor (HPS) integrating triboelectric pressure sensor (TPS) and piezoelectric pressure sensor (PPS) is proposed. For the TPS, a simple, low-cost, and structurally controllable microstructure preparation method is proposed in order to investigate the effect of carbon nano-onions (CNOs) and hierarchical composite microstructures on the electrical properties of CNOs@Ecoflex. The PPS is used to broaden the pressure response range and reduce the pressure detection limit of HPS. It has been experimentally demonstrated that the HPS has a high sensitivity of 2.46 V/10⁴ Pa (50–600 kPa) and a wide response range of up to 1200 kPa. Moreover, the HPS has a low detection limit (10 kPa), a high stability (over 100,000 cycles), and a fast response time. The sleep monitoring system constructed based on HPS shows remarkable performance in breathing state recognition and sleeping posture supervisory control, which will exhibit enormous potential in areas such as sleep health monitoring and potential disease prediction. Full article

Improving the damping capacity of metal matrix composites is crucial, especially for applications in the aerospace industry where reliable performance against vibrations and shocks is mandatory. The main objective of the present study is the numerical prediction of the damping behavior of alpha titanium matrix nanocomposites reinforced with hollow carbon nano-onions at various volume fractions. According to the proposed numerical scheme, a structural transient analysis is implemented using the implicit finite element method (FEM). The metal matrix nanocomposites are modeled via the utilization of appropriate representative volume elements. To estimate the mechanical and damping behavior of the nanocomposite representative volume elements, axial sinusoidally time-varying loads are applied to them. The damping capacity of the metal matrix nanocomposites is then estimated by the arisen loss factor, or equivalently the tan delta, which is computed by the time delay between the input stress and output strain. The analysis shows that the loss factor of alpha titanium may be improved up to 60% at 100 Hz by adding 5 wt% carbon nano-onions. The numerical outcome regarding the dynamic properties of the carbon nano-onions/alpha titanium nanocomposites is used in a second-level analysis to numerically predict their damping performance when they are additionally reinforced with unidirectional carbon fibers, using corresponding representative volume elements and time-varying loadings along the effective direction. Good agreement between the proposed computational and other experimental predictions are observed regarding the stiffness behavior of the investigated metal matrix nanocomposites with respect to the mass fraction of the carbon-onion nanofillers in the titanium matrix. Full article

In this work, carbon nano-onions (CNOs) with particle sizes of 5–10 nm were prepared by the multi-potential step method. High-resolution transmission electron microscopy, infrared spectroscopy and Raman spectroscopy characterize the effective synthesis of CNOs. CNOs/GCEs were prepared by depositing the prepared CNOs onto glassy carbon electrodes (GCEs) by a drop-coating method. Examination of the electrocatalytic activity of the CNOs/GCE sensor by simultaneously detecting dopamine (DA), uric acid (UA), L-tryptophan (Trp) and theophylline (TP) using a differential pulse voltammetry technique. The results showed that the linear ranges of DA, UA, Trp and TP were DA 0.01–38.16 μM, UA 0.06–68.16 μM, Trp 1.00–108.25 μM, and TP 8.16–108.25 μM, and the detection limits (S/N = 3) were 0.0039 μM, 0.0087 μM, 0.18 μM and 0.35 μM, respectively. The CNO_S/GCE sensor had good stability and could be used for the detection of actual samples. Full article