Synthesis Of Carbon Nano-onions Research Articles

The use of ex-situ nitrogen-doped olive oil-derived carbon nano-onions for application in chemi-resistive gas sensors to detect acetone at room temperature

This study reports on the synthesis of carbon nano-onions (CNOs; ca. d < 55 nm) and nitrogen-doped CNOs (N-CNOs) using a facile pyrolysis method and ex-situ doping of the CNOs. Elemental analysis of the N-CNOs revealed that their nitrogen content depended on the ammonia flow rate. Analysis of the N-CNOs revealed that they all exhibited structural defects. After the successful synthesis of CNOs and N-CNOs, polyvinylpyrrolidone (PVP):CNOs/N-CNOs:MnO2-nanorods (MONRs) composites were prepared and used as active sensing materials. In every case, the PVP polymer was used to stabilize the MONRs for acetone detection at 25 °C. The chemi-resistive gas sensors that showed the highest acetone sensitivity (pS = 2.0 x 10-4 ppm-1) was fabricated using a pristine CNOs (pCNOs) based composite. However, the N-CNOs based sensor (a15S) presented the lowest acetone limit of detection (LoD) at 1.2 ppm. The study implicated the effect of the nitrogen and oxygen content of the CNOs surfaces on the acetone detection. Thus, a higher sensitivity with lower LoD was observed at room temperature using the pCNOs based sensor, when compared to earlier literature reports.

One-step hydrothermal synthesis of carbon nano onions anchored on graphene sheets for potential use in electrochemical energy storage

One-step hydrothermal synthesis of carbon nano onions anchored on graphene sheets for potential use in electrochemical energy storage

The role of oxygen in a carbon source (castor oil versus paraffin oil) in the synthesis of carbon nano-onions

The role of a carbon source containing oxygen groups on the physicochemical properties of carbon nano-onions (CNOs) was investigated. Two oils, castor oil (with O groups) and paraffin oil (without O groups) were converted to CNOs in gram-scale yields using an open flame pyrolysis procedure. The products were heated under argon at 900 °C for varying times (1 h, 2 h, 3 h), to investigate the temperature dependence on their structural properties. TGA studies indicated different decomposition behaviour for the different samples with the annealed paraffinic CNOs (CNOP) having a higher decomposition temperature (>600 °C) than the castor oil derived CNOs (CNOC) (<600 °C). TEM images revealed formation of typical chain-like quasi-spherical nanostructures with particles size distributions for the CNOP (22–32 ± 7.8 nm) and the CNOC (44–51 ± 9.9 nm) materials. A detailed Raman analysis of the CNOs revealed that the graphicity of the CNOs varied with both the carbon oil source and the annealing time. Deconvolution of the first order Raman spectra revealed changes in the parameters of the major Raman bands that were then correlated with defect density ratios. Finally, bandwidth analysis depicted the dependence of the graphicity of the CNOs with heat treatment. The data thus indicate that the presence of oxygen in the carbon source provides a method for producing different CNOs and that simple procedures can be used to produce these different CNOs.

(Invited) Electrochemical Synthesis of Carbon Nano Onions

Carbon nano-onions (CNOs) as one of the carbon allotropes, possessing peculiar structure, are composed of multilayered concentric graphitic shells. CNOs can be classified into two types, including hollow polyhedral CNOs and core–shell structured CNOs. CNOs have attracted a great deal of attention because of their unique chemical and physical properties. Dependent on these properties they show potential applications in many areas such as solid lubricants, electrode materials in capacitors, as anode materials in lithium-ion batteries, and as catalyst support in fuel cells as well as biomedical field as pharmaceutical delivery platforms 1. However, to produce CNOs in quantity would be extremely challenging, especially hollow polyhedral carbon onions. At present, the preparation methods of CNOs reported included annealing of nanodiamonds at high temperature 2, thermal treatment of laser pyrolysis carbon blacks and co-sputtering 3, chemical vapour deposition 4 and so on. The common characteristic of these methods was the need for high temperature. Due to lack of controllable preparation methods, little research on hollow polyhedral CNOs has been reported. Here, we describe a simple electrochemical method to prepare high quality hollow polyhedral CNOs without the use of high temperature equipment.Electrochemical synthesis was carried out in a mixed solution of acetonitrile and toluene containing 0.10 M tetra-n-butylammonium perchlorate by using a three-electrode electrochemical system with a platinum plate electrode as the working electrode, a platinum plate electrode as the counter electrode and a Ag rod as the quasi reference electrode in a glove box, as shown in Figure 1a. Multi-potential steps electrolysis were employed. The obtained solid products after electrolysis for a few hours were dispersed in N-cyclohexylpyrrolidone by ultrasonication, and then the solid spherical CNOs and the hollow polyhedral CNOs were separated by gradient centrifugation, as shown in Figures 1b and 1c by high resolution transmission electron microscope characterization. Figure 1d displays TEM oblique image of a hollow polyhedral CNO. A series of images obtained from different tilt angles proved that CNOs were polyhedral hollow structures. Hollow carbon nano onions have an average diameter of 20 nm. The synthetic method is economical and environmentally friendly. Because the CNOs obtained by different methods owned different structures and properties, the properties and applications of the hollow polyhedral CNOs are under way.ACKNOWLEDGEMENTThis work was supported by the National Natural Science Foundation of China (No 21675003 and 21974003).REFERENCES 1. Mykhailiv, O.; Zubyk, H.; Plonska-Brzezinska, M. E., Carbon nano-onions: Unique carbon nanostructures with fascinating properties and their potential applications. Inorganica Chimica Acta 2017, 468, 49-66.2. Kuznetsov, V. L.; Chuvilin, A. L.; Butenko, Y. V.; Mal'kov, I. Y.; Titov, V. M., Onion-like carbon from ultra-disperse diamond. Chemical Physics Letters 1994, 222, 343-348.3. Sano, N.; Wang, H.; Alexandrou, I.; Chhowalla, M.; Teo, K. B. K.; Amaratunga, G. A. J.; Iimura, K., Properties of carbon onions produced by an arc discharge in water. Journal of Applied Physics 2002, 92, 2783-2788.4. Zhang, C.; Li, J.; Liu, E.; He, C.; Shi, C.; Du, X.; Hauge, R. H.; Zhao, N., Synthesis of hollow carbon nano-onions and their use for electrochemical hydrogen storage. Carbon 2012, 50, 3513-3521.

Electrochemical synthesis of carbon nano onions

Electrochemical synthesis of hollow and solid carbon nano onions from simple aromatic compounds in acetonitrile on a platinum plate electrode by a multi-potential steps method.

Sustainable Process for Carbon Nano Onions from Flaxseed Oil for High-Performance Supercapacitors

One of the global key challenge for our society is energy crisis and increasing environmental pollution arises from excessive consumption of fossil fuels. There is an increasing demand for long-term sustainable and durable energy storage devices with tremendous applications in electric, car power supply and wearable electronics. This requires simple, economical and green techniques for the fabrication of active materials to be used in energy storage devices. Supercapacaitor (SCs) as a promising energy storage device which uses electrical double layer (EDL) composed by electrolyte ions and charges on electrode materials surface, and the physisorption offer moderate energy density, high power density, stable life cycle and pollution free operation. With consideration to SCs performance depending on the physical interface, many efforts have been focused to improve electrochemical performance of SCs with high capacitance and higher voltage operated with electrolytes. Herein, we try to address both these critical issues exploring sustainable synthesis of carbon nano onions (CNOs) as the electrode material to fabricate high performance and durable SCs. An environmental-friendly flame synthesis approach was used for facile and large scale synthesis of CNOs for application in high-performance supercapacitors.

Effects of Acoustic Modulation and Mixed Fuel on Flame Synthesis of Carbon Nanomaterials in an Atmospheric Environment.

In this study, methane–ethylene jet diffusion flames modulated by acoustic excitation in an atmospheric environment were used to investigate the effects of acoustic excitation frequency and mixed fuel on nanomaterial formation. Acoustic output power was maintained at a constant value of 10 W, while the acoustic excitation frequency was varied (f = 0–90 Hz). The results show that the flame could not be stabilized on the port when the ethylene volume concentration (ΩE) was less than 40% at f = 10 Hz, or when ΩE = 0% (i.e., pure methane) at f = 90 Hz. The reason for this is that the flame had a low intensity and was extinguished by the entrained air due to acoustic modulation. Without acoustic excitation (f = 0 Hz), the flame was comprised of a single-layer structure for all values of ΩE, and almost no carbon nanomaterials were synthesized. However, with acoustic excitation, a double-layer flame structure was generated for frequencies close to both the natural flickering frequency and the acoustically resonant frequency. This double-layer flame structure provided a favorable flame environment for the fabrication of carbon nanomaterials. Consequently, the synthesis of carbon nano-onions was significantly enhanced by acoustic excitation near both the natural flickering frequency and the acoustically resonant frequency. At f = 20 Hz (near the natural flickering frequency) for 0% ≤ ΩE ≤ 100%, a quantity of carbon nano-onions (CNOs) piled like bunches of grapes was obtained as a result of improved mixing of the fuel with ambient air. High-density CNOs were also produced at f = 70 Hz (close to the acoustically resonant frequency) for 40% ≤ ΩE ≤ 100%. Furthermore, carbon nanotubes (CNTs) were synthesized only at 80 Hz for ΩE = 0%. The suitable temperature range for the synthesis of CNTs was slightly higher than that for the formation of CNOs (about 600 °C for CNTs; 510–600 °C for CNOs).

ChemInform Abstract: Carbon Nano‐Onions: Large‐Scale Preparation, Functionalization and Their Application as Anode Material for Rechargeable Lithium ion Batteries

AbstractReview: 114 refs.

Influence of oxygen concentration, fuel composition, and strain rate on synthesis of carbon nanomaterials

This paper investigates the influence of flame parameters including oxygen concentration, fuel composition, and strain rate on the synthesis of carbon nanomaterials in opposed-jet ethylene diffusion flames with or without rigid-body rotation. In the experiments, a mixture of ethylene and nitrogen was introduced from the upper burner; meanwhile, a mixture of oxygen and nitrogen was supplied from the lower burner. A nascent nickel mesh was used as the catalytic metal substrate to collect deposited materials. With non-rotating opposed-jet diffusion flames, carbon nanotubes (CNTs) were successfully produced for oxygen concentrations in the range of 21–50 % at a fixed ethylene concentration of 20 %, and for ethylene concentrations ranging from 14 to 24 % at a constant oxygen concentration of 40 %. With rotating opposed-jet diffusion flames, the strain rate was varied by adjusting the angular velocities of the upper and lower burners. The strain rate governed by flow rotation greatly affects the synthesis of carbon nanomaterials [i.e., CNTs and carbon nano-onions (CNOs)] either through the residence time or carbon sources available. An increase in the angular velocity lengthened the residence time of the flow and thus caused the diffusion flame to experience a decreased strain rate, which in turn produced more carbon sources. The growth of multi-walled CNTs was achieved for the stretched flames experiencing a higher strain rate [i.e., angular velocity was equal to 0 or 1 rotations per second (rps)]. CNOs were synthesized at a lower strain rate (i.e., angular velocity was in the range of 2–5 rps). It is noteworthy that the strain rate controlled by flow rotation greatly influences the fabrication of carbon nanostructures owing to the residence time as well as carbon source. Additionally, more carbon sources and higher temperature are required for the synthesis of CNOs compared with those required for CNTs (i.e., about 605–625 °C for CNTs and 700–800 °C for CNOs).

Formation of Carbon Nano Onions by Thermo-Mechanical Processing of Graphite Powders

Abstract This study reports on the thermo-mechanical synthesis of carbon nano onions from elemental graphite powders. Initially, amorphous carbon was obtained by high energy ball milling technique from graphite powders. X-ray spectra taken from ball milled samples indicated that the hexagonal graphite, composed of layers, was transformed into the amorphous carbon for a shorter milling time of 5 h by high energy input about 78 times of gravity. Subsequent isothermal annealing of milled graphite powders was conducted at 1400 °C for 4 h in Ar gas. It was revealed via investigation of transmission electron microscopy that carbon nano onions were formed after annealing.

Flame synthesis of carbon nano onions using liquefied petroleum gas without catalyst

Densely agglomerated, high specific surface area carbon nano onions with diameter of 30–40nm have been synthesized. Liquefied petroleum gas and air mixtures produced carbon nano onions in diffusion flames without catalyst. The optimized oxidant to fuel ratio which produces carbon nano onions has been found to be 0.1 slpm/slpm. The experiment yielded 70% pure carbon nano onions with a rate of 5g/h. X-ray diffraction, high-resolution electron microscopy and Raman spectrum reveal the densely packed sp2 hybridized carbon with (002) semi-crystalline hexagonal graphite reflection. The carbon nano onions are thermally stable up to 600°C.