Arc Discharge In Water Research Articles

Detailed yield assessment of carbon nanostructures synthesized by submerged arc discharge in water

Submerged arc discharge in water (SADW) is one of the most effective methods for the synthesis of high-quality carbon nanostructures (CNSs). Despite the numerous published studies on SADW, systematic data on yield is still lacking. The SADW runs as a succession of stable and unstable zones, but the influence of these zones on its yield has not yet been explored. The CNSs were synthesised in a SADW facility with a micro-positioning system controlled by current feedback, stabilisation via ballast resistance, and data recorded by a five-parameter correlated measurement system. The synthesis products were characterised by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) adsorption isotherms. In this study, an approach is presented to determine the SADW yield by analysing the correlation between the process parameters recorded with the experimental setup and gravimetric measurements. In the work, the relationship between the formation of the different CNSs and the stable and unstable zones is discussed. The yield was determined at a current of 30 A, which is considered the optimal current for CNSs synthesis, and the estimation obtained indicates that it is in the range of 1%–1.3%. The energy consumption to produce CNSs was assessed to be around 80 kJ.mg−1. The results obtained contribute to clarifying some of the factors that influence yield and how to optimise it. This work provides a useful reference point for future work associated with CNS synthesis using SADW.

Experimental study on the underwater DC arc behaviors regulated by an external transverse magnetic field

An arc discharge in water can generate extremely high voltage, which has great potential to be used in DC fault protection. The voltage characteristic is closely related to the arc behaviors. However, due to the complexity of the gas–liquid mixed environment, the arc shape is difficult to observe directly. In this letter, an observation device is specially designed and underwater arc motion with millisecond-scale duration is clearly photographed. The corresponding relationship between the arc behaviors and the varied voltage is revealed. Additionally, the random behaviors of underwater arc are controlled stably by applying an external transverse magnetic field. The enhanced cooling mechanism and the directional arc motion characteristics are discussed. We demonstrate that fast elongation of the arc column and continuous heat exchange between phase surfaces are the keys to realizing a rapid increase of underwater arc voltage.

Neutral red dye adsorption on carbon nano-onions: viability assay interference and adduct characterisation

Carbon nano-onions (CNO) are versatile carbon nanomaterials with many potential biomedical applications. In this work, the interaction of submerged arc discharge in water (SADW) produced CNOs with the neutral red (NR) dye was studied. This dye is used in the in vitro toxicity NR assay, one of the most commonly used dye-based procedures to determine cell viability. Firstly the NR assay was carried out in murine fibroblast cell cultures exposed to CNOs. It was demonstrated that this assay produced invalid results due to the strong adsorption of NR on the CNOs. Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) studies confirmed the effective adsorption of the NR on CNOs and π-π stacking as the main interaction between them. The adsorption of NR on the CNOs was evaluated by studying the decrease of the dye solution absorbance. The influence of different experimental conditions such as pH and CNOs dosage was evaluated: absorbance was found to diminish with the CNO dosage. For the maximum dosage used of 240 μg ml−1, the highest absorbance drops of −85% at pH 7 and −78% at pH 4 were registered. The adsorption process was found to be described best by a pseudo-first order (PFO) kinetics model (R 2 = 0.99), with a kinetic adsorption constant of k 1 = 0.02 min−1 and achieving an estimated sorption capacity of 3866 mg of dye per gram of CNOs. This is one of the highest values ever reported for dyes’ adsorption on carbon materials. Lastly, density functional theory (DFT) calculations were carried out to gain further insights into the interaction. These studies suggest a CNO highest occupied molecular orbital (HOMO)/NR lowest unoccupied molecular orbital (LUMO) electron density transfer as the main orbital interaction.

Probing ionization characteristics of under-water plasma arc discharge using simultaneous current and voltage versus time measurement in carbon nanoparticle synthesis

Abstract This study investigated the characteristics of plasma ionization that occurs during plasma arc discharge in water using carbon electrodes. The characterization of plasma ionization begins by observing the arc shape using a digital camera associated with voltage oscillation using current and voltage vs. time (I-t and V-t) characteristics. Furthermore, the ionization energy calculation is performed using simultaneous I-t and V-t measurement data. These calculations are then compared to the photon energy from the optical emission spectroscopy (OES). The results from the digital camera indicate four types of arc discharge in terms of shape and intensity related to voltage oscillation. Moreover, the energy calculations show that by using the I-t and V-t methods is possible to measure the plasma ionization detected not only in the range 1–4 eV but also in the outside range, including smaller than 1 eV and greater than 4 eV. These ranges correspond to the emission lines in visible light, infrared, and ultraviolet, respectively. In addition, the I-t and V-t methods can also measure the excitation and recombination energy of the arc discharge plasma ionization. This study reveals the possibility of investigating the characteristics of plasma ionization using simultaneous I-t and V-t measurements, which comprise an easier and more practical method in the diagnostics of carbon nanoparticle synthesis • A novel plasma diagnostic using I-t and V-t measurement were demonstrated as a probing method for ionization of arc discharge. • I-t and V-t measurement measurement reveals voltage oscillation during arc discharge for different states. • The difference in arc intensity and shape is due to the difference in plasma ionization characteristics of arc discharge. • Numerical analysis of single discharge energy is calculated from I-t and V-t data to obtain plasma parameters.

Shed light on defect induced enhanced visible-light photocatalysis activity of rutile TiO2 nanoparticles: effects of annealing on blue-gray to light–gray transition

Preparation of the defective TiO2 nanoparticles (NPs) have been recently in particular interest for its outstanding applications in visible-light active photocatalysis. In order to make TiO2 visible-light absorber, optical band gap should be modified especially via introducing structural defects like oxygen vacancies as an effective pathway. In this research, we prepared defective rutile TiO2 NPs with highly efficient photocatalytic activity under visible light. The NPs were synthesized by electric arc discharge in water as a cost-effective and environmentally friendly method with capability of defect formation which followed by heat treatment. The photocatalytic activity improvement mechanisms based on oxygen vacancies were supported by TEM, XPS, XRD, PL and optical spectroscopy characterizations. Spherical TiO2 NPs with average size of 23, 28, 38, and 50 nm were obtained for pristine, and annealed samples at 300, 500 and 700 °C respectively. The optical band gaps of NPs decreased from 2.9 to 2.0 eV with annealing temperature, and a concurrent color change from blue-gray to light-gray. The XPS results confirm the presence of vacant oxygen and surface OH defects in all TiO2 samples. The results reveal that concentration of surface defects and mostly the oxygen vacancies play a crucial role in visible light photoactivity of gray TiO2 nanostructures. In the synthesized TiO2 NPs, the sample with the lowest concentration of non-lattice oxygen exhibit better degradation efficiency than other samples. The results provide a flexible method for synthesis of defective rutile TiO2 as a highly efficient visible active photocatalyst nanomaterial.

Necked gold nanoparticles prepared by submerged alternating current arc discharge in water.

The article presents the method of producing gold nanoparticles using a high voltage arc discharge of alternating current with a frequency of 50 Hz in distilled water. The equipment necessary to carry out the process is described, including the construction of the reactor and the power source of a very simple design necessary to generate a high-voltage arc discharge between the electrodes. Arc discharge processes were carried out two times for 2 and 5 minutes, respectively, in ambient conditions without thermostating the reactor, at medium temperature varying in the range of 25-70 °C. The obtained gold nanoparticles were examined by means of various analytical techniques such as UV-vis spectroscopy, zeta potential measurement, energy dispersive X-ray analysis (EDS), X-ray diffraction (XRD). The morphology, surface, and size of the obtained nanoparticles were carried out using transmission electron microscopy (HRTEM) and dynamic light scattering (DLS). The concentration of the obtained colloids were determined using the mass spectrometry ICP-MS technique. The results show that high-voltage AC arc discharge is a simple and effective way to obtain stable gold nanoparticles under environmentally friendly conditions at relatively low production costs, and can be considered as an alternative to arc discharge nanoparticles synthesis by means of direct current (DC) methods.

Carbon quantum dots by submerged arc discharge in water: Synthesis, characterization, and mechanism of formation

Carbon quantum dots (CQDs) are novel nanostructures that have great potential as fluorescent markers due to their multi-fluorescence, down and up converted emission, resistance to photobleaching, and biocompatibility. Here, we report the synthesis of fluorescent CQDs by the submerged arc discharge in water method. We discuss the method's simplicity, natural phases’ separation, and scalability. The produced CQDs size distribution was in the range of 1–5 nm. High-resolution transmission electron microscopy images and their fast Fourier transformation allowed the analysis of the CQDs’ internal structure. The absorption and fluorescence spectra of the as-produced CQDs were analyzed. The UV-Vis spectrum shows a single band with a maximum located at 356 nm. The photoluminescence emission presents two consistent bands with maxima located in the ranges of 320–340 nm (band A) and 400–410 nm (band B). To these emission bands correspond two bands in the excitation spectra located at 275 nm (band A) and 285 nm (band B). The fluorescence quantum yield was assessed as ∼16% using Rhodamine 6G as reference. The capabilities of the produced CQDs as fluorescent markers for in vitro studies were also evaluated by setting them in contact with a cell culture of L929 murine fibroblasts. Control and CQD-treated cell cultures were visualized under a fluorescence microscope. Finally, the mechanism of formation of these nanostructures by top-down methods is discussed, and a general model of formation is proposed.

Obtained Carbon Nano-onions from Underwater Arc Discharge Without the Complex Purification Procedures

Carbon nano-onions (CNOs), which consist of concentric graphitic shells, currently attract much attention because of their unique structural and physical properties, which are different from the properties of the other carbon nanomaterials such as fullerenes, graphene, and carbon nanotubes (CNTs). Due to their small size, the large external surface area and high conductivity, CNOs are used for supercapacitor applications. The arc discharge underwater is an effective and simple method for the synthesis of larger CNOs in reasonable quantities. In this research, we have been obtained carbon nanomaterials using arc discharge in water between two high purity graphite electrodes. The main experimental techniques used to characterize carbon nanostructures have been Transmission Electron Microscopy (TEM) and Raman Spectroscopy. Among them, Raman spectroscopy is the most useful non-destructive technique capable of differentiating between these various structures. Our TEM images showed that the samples collected from the material floating on the water surface consist CNOs with other carbon nanomaterials such as CNTs. We observed for the first time the formation of solid agglomerate on the cathode surface. Raman and TEM results revealed that the agglomerate is made exclusively of CNOs. The defragmentation of such agglomerate allows to obtain CNOs free of other carbon nanomaterials without the complex purification procedures needed for floating nanomaterials.

XRD Quantitative Analysis of Cathode Deposition Formed by DC Arc-Discharge in Water

In this study, we aimed to estimate the weight fraction of crystalline phases in a cathode deposition formed by DC arc-discharge between graphite electrodes in water via the XRD method and CARBON XS program based on Shi model, which takes into account disorder and stacking faults in a graphite structure. The structural computation of graphitic carbon materials for comparison was done by using CARBON XS according to Shi model. From the study, we observed that the total weight fraction of 2H hexagonal and 3R rhombohedral ordered structures of graphitic carbon decreases from 77.69% to 48.98%, whereas the weight fraction of random shift and stacking faults increases from 22.31% to 51.02% as compared to these parameters belonging to pure graphite structure during the arc-discharge process.

One-step synthesis of carbon nanoflowers by arc discharge in water

Nanoflowers are a recent class of nanomaterials that show structural similarity to plant flowers. Among these structures, carbon nanoflowers (CNFs) stand out as promising materials for application in electrochemistry, gas adsorption and absorption, batteries and supercapacitors. This paper innovates by presenting a method for CNFs production using electric arc (EA) discharge in water. The main advantage of using water instead of other liquid media is the possibility of reusing that water several times, reducing its waste in an eco-friendly process. X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the yielded CNFs present high quality (ID/IG = 1.03), homogeneity and purity. The low-cost and simplicity of CNFs synthesis by EA in water make their production on an industrial scale attractive.

(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.

Size-selected polyynes synthesised by submerged arc discharge in water

Polyynes, linear sp-carbon chains of finite length, can be synthesised by submerged arc discharge in liquid, which so far, has been mainly exploited in organic solvents.In this work, we investigated this technique in water as a cheap and non-toxic solvent to produce polyynes. After optimisation of the process parameters, hydrogen-terminated polyynes (CnH2: n = 6–16) were identified by high-performance liquid chromatography with the support of theoretical calculations. Size-selected polyynes were separately analysed by surface-enhanced Raman spectroscopy allowing to assign the bands of mixed polyynes solution to specific wire lengths. Stabilisation strategies for hydrogen-capped polyynes were also studied, obtaining promising results.

Structural Features of Products Formed during DC Arc Discharge in Water

Products formed in the discharge region of the DC arc between graphite electrodes in water were studied. Whereas one of them was grown on a cathode and kept whole, the other is arose by erosion of electrodes in powder form and sank or floated in the surrounding water. The structure of the products was studied by SEM and SEM EDX analysis. The whole parts grown on the cathode were made up three different components: (i) almost spherical tiny particulates; (ii) long and narrow linear parts; and (iii) macro particulates of gigantic size. We have identified the size distributions and the number densities for these component parts in the sample as well their mechanical features. The powder samples included bulk particulates of carbon sheets and linear structures, like a thread. The study shows that the long linear structures in the powder sample are formed by the scrolling of carbon layers whereas the ones deposited are formed by a growth mechanism

Toxicity, morphological and structural properties of chitosan‐coated Bi 2 O 3 –Bi(OH) 3 nanoparticles prepared via DC arc discharge in liquid: a potential nanoparticle‐based CT contrast agent

In this study, Bi 2 O 3 nanoparticles were employed as computed tomography (CT) contrast agents. In this regard, X-ray attenuation of Bi 2 O 3 nanoparticles, prepared via DC arc discharge in water, was investigated. In addition, the optical, structural, morphology and cytotoxicity properties of afforded nanoparticles were also studied. The electric arc discharge was done via bismuth electrodes in a water medium. Then, to stabilise Bi 2 O 3 nanoparticles, chitosan molecule was cross linked via glutaraldehyde around Bi 2 O 3 nanoparticles. X-ray diffraction analysis demonstrated the monoclinic structure and field emission-scanning electron microscopy images clarified the average size of Bi 2 O 3 as 40 nm. Fourier transform infrared analysis proved chitosan band formation around Bi 2 O 3 nanoparticles. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay revealed no considerable toxicity after 72 h. Finally, X-ray CT of chitosan-coated Bi 2 O 3 nanoparticles and Iohexol was carried out at concentrations of 1-6 mg/ml. The CT number of chitosan-coated Bi 2 O 3 nanoparticles measured 16, 30, 49, 66, 75 and 85, as well as, respective numbers for Iohexol were 5, 14, 25, 34, 44 and 57. Therefore, it displayed that X-ray attenuation of chitosan-coated Bi 2 O 3 nanoparticle was more in comparison with Iohexol at the same concentrations. Eventually, the results demonstrated that chitosan-coated Bi 2 O 3 nanoparticles are a suitable candidate for commercial iodine contrast agent substitution.

Formation mechanisms, structural and optical properties of Bi/Bi2O3 One dimensional nanostructures prepared via oriented aggregation of bismuth based nanoparticles synthesized by DC arc discharge in water

Bismuth based rod-like nanostructures were prepared via oriented attachment of colloidal bismuth based nanoparticles synthesized by direct current (DC) arc discharge in liquid. For the synthesis of bismuth based nanoparticles 5 A and 20 A DC electrical currents were applied between two pure bismuth electrodes in water. Bismuth based nanoparticles extracted from the water after 30 days then dispersed in ethanol. Bismuth based rod-like nanostructures formed via the oriented attachment mechanism in ethanol during 30 days. According to X-ray diffraction (XRD) patterns of as-prepared samples, the main parts of the particles were bismuth phase while after 30 days bismuth oxide and bismuth hydroxide phases were dominant. To investigate the species that formed in plasma during the electrical discharge in water, optical emission spectroscopy (OES) was used. The OES spectra demonstrate the creation of Bi-I, Bi-II, O-I, O-II and H ions and H2-I molecules for both currents. UV–visible spectroscopy and field emission scanning electron microscopy (FE-SEM) were used for the study of optical properties, morphology and size distribution of the nanostructures respectively. Optical transmission spectra of synthesized nanostructures in water indicated the optical characteristic of both bismuth and bismuth oxide. FE-SEM images illustrate that bismuth based nanoparticles are rather spherical as-prepared and formed rod-like nanostructures by passing the time in the presence of ethanol. Also, the size of nanoparticles and subsequently diameter of rod-like nanostructures for samples that prepared by 5 A arc current is more than samples that prepared by 20 A. The results provide a simple and flexible method for synthesis of bismuth based rod-like nanostructures.

Selective synthesis of turbostratic polyhedral carbon nano-onions by arc discharge in water

Carbon nano-onions (CNOs), in their spherical or polyhedral forms, represent an important class of nanomaterials, due to their peculiar physical and electrochemical properties. Among the different methods of production, arc discharge between graphite electrodes sustained by deionized water is one of the most promising to obtain good quality CNOs in gram quantities. We applied the method with the aim to optimize the production of CNOs, using an innovative experimental arrangement. The discharges generate dispersed nanomaterials and a black hard cathodic deposit, which were studied by transmission electron microscopy–high-resolution TEM, scanning electron microscopy, Raman, thermogravimetric analysis and energy-dispersive x-ray spectroscopy. A simple mechanical grinding of the deposits permitted us to obtain turbostratic polyhedral CNOs that exhibited higher stability towards burning in air, compared to CNOs found in water. We propose a mechanism for the formation of the CNOs present in the deposit, in which the crystallization is driven by a strong temperature gradient existing close to the cathode surface at the beginning of the process, and subsequently close to the deposit surface whenever it is growing.

Shed light on submerged DC arc discharge synthesis of low band gap gray Zn/ZnO nanoparticles: Formation and gradual oxidation mechanism

Synthesis of colloidal metal oxides with controllable size and morphology is burgeoning field of research in nanoscience. Low band gap gray Zn/ZnO colloidal nanoparticles were fabricated by plasma-liquid interaction of DC arc discharge in water. Scanning electron microscopy, X-ray diffraction and UV–vis spectroscopy were employed for morphology, crystal structure and optical characterizations respectively. Optical emission spectroscopy was used to investigate the plasma properties during the synthesis and formation mechanism of nanoparticles. Nanoparticles with different size and shape were fabricated only by adjusting discharge current during synthesis without introducing any chemical agent. Electric discharge current was set to 20, 50, 100 and 150 A during synthesis. Estimated values of plasma excitation energies were 2.41, 2.66, 2.86 and 3.04 eV and diameter size of nanoparticles were 63, 42, 37 and 29 nm for these applied currents respectively. Synthesized nanoparticles were dark gray as prepared and became more transparent gradually getting white color finally. XRD and UV–vis results revealed that the oxidation process was time dependent. The colloidal nanoparticles composed of two metal and metal-oxide phase and white crystalline ZnO was achieved after complete oxidation process. These results provided a flexible and versatile method to synthesize metal oxide nanoparticles with controlled composition.

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

AbstractReview: 114 refs.

<italic>Escherichia Coli</italic> Inactivation in Water Using Pulsed Discharge

In this paper, a new multiple-needle-cylinder reactor is designed to study the Escherichia coli inactivation with an unstable pulsed arc discharge in water and investigate the influence of several parameters for promoting its industrial application. The results show that the inactivation rate is mainly determined by energy density. About three orders reduction can be obtained with an initial cell count of $3\times 10^{5}$ CFU/mL and energy density around 2 J/mL. The inactivation rate can almost reach 100% when the energy density is around 8 J/mL. For reaching the maximum inactivation rate of this system, the parameters including initial water conductivity below $50~\mu \text{S}$ /cm, initial cell count over $10^{4}$ CFU/mL, and bubbling flow rate around 3.5 L/min are recommended. The water conductivity, pH value, and concentrations of hydrogen peroxide and ozone are also measured during the treatment to evaluate their influence. The transmission electron microscopy images of E. coli indicate that the intracellular morphology changes after plasma treatment.

Synthesis of Magnetite/ Hematite/ Iron Nanocomposites by the Low Voltage Arc Discharge in Water in the Presence of External Magnetic Field

Synthesis of Magnetite/ Hematite/ Iron Nanocomposites by the Low Voltage Arc Discharge in Water in the Presence of External Magnetic Field