Arc Discharge In Liquid Research Articles

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.

Effect of C/H and C/O ratios on the arc discharge synthesis of titanium carbide nanoparticles in organic liquids

TiC nanoparticles were synthesized by submerged direct current (DC) arc discharge in liquid. Synthesis process was carried out in methanol, ethanol and acetone under inert atmosphere by applying 40 A between two pure titanium electrodes with vertical configuration. X-ray diffraction, field emission scanning electron microscopy and UV–visible spectroscopy were used for characterization of nanoparticles. In addition, plasma species were characterized via optical emission spectroscopy (OES). According to the obtained results, nanoparticle shape is spherical, and average particle size of nanoparticles is 28, 45 and 38 nm in methanol, ethanol and acetone, respectively. Although composition of nanoparticles in ethanol and acetone is single-phase of TiC, the presence of around 30% of rutile phase of TiO2 was observed in methanol. According to the OES observation, TiC nanoparticle formation mechanisms are discussed based on the decomposition of organic liquids in arc discharge zone, formation of some carbon species and reaction of this carbon-containing species with Ti species in plasma. In addition, C/H and C/O ratios play a critical role in formation and dominant phase of final product. These results demonstrate a simple and flexible method for rapid mass production of TiC and other refractory metal carbides nanoparticles in an appropriate organic liquid.

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.

Formation mechanism of bead-chain-like ZnO nanostructures from oriented attachment of Zn/ZnO nanocomposites prepared via DC arc discharge in liquid

Bead-chain-like ZnO nanoparticles (NPs) formed in colloidal solution from oriented attachment (OA) of spherical nanoparticles. Arc discharge in liquid is a cost-effective method for quick mass production of nanostructured materials without considerable environmental footprints. Applying voltage across two zinc rods as electrodes, which were immersed in water cause explosion of electrodes and plasma generation. Zn/ZnO nanocomposites produced by interaction of different active species in high-pressure and high-temperature plasma at the solid-liquid interface. Different sized nanoparticles with diameters of 26, 35, 40 and 60nm at applied discharge currents of 150, 100, 50 and 20A respectively, were fabricated in water without any chemical additives. The results showed bead-like oriented attachments appeared with increasing the applied current during synthesis. Length of aggregates increases from 114nm to 120nm with the applied current of the arc discharge. The mechanism of OA of ZnO NPs was investigated by calculating the attractive and repulsive forces based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed for characterization of particle size, shape, and investigation of bead-like aggregates. X-ray diffraction (XRD) analysis was used to study the crystal structure and phase composition of the bead-chain like nanostructures. Finally, zeta potential analysis was used to measure surface charges and study the mechanism of oriented attachment. The results provide a simple and flexible method for synthesis of Zn/ZnO bead-chain like nanostructures.

Preparation of Amine-Functionalized TiO2/Carbon Photocatalyst by Arc Discharge in Liquid

Amine-functionalized titanium dioxide/carbon (TiO2/C) was prepared via the arc discharge method using graphite electrodes and a liquid medium consisting of 50% ethanol with the addition of urea. The arc discharge was conducted using a voltage of 20 to 40 V. X-ray diffraction (XRD) of prepared TiO2/C showed a pattern of definitive peaks at 25.32°, 26.61°, and 36.14°, which are the main characteristic peaks of TiO2, C graphite, and titanium carbide, respectively. The successful surface modification of TiO2/C synthesized in liquid ethanol/urea resulted in better dispersion of nanoparticles in water than TiO2/C synthesized in ethanol only. This surface characteristic was also confirmed via Fourier transform infrared (FTIR) spectra of TiO2/C synthesized in liquid ethanol/urea, which revealed C=O, C–N, C–O, and N–H stretching vibrations at 1600–1700, 1400–1100, 1200–1300, and 3300–3400 cm−1, respectively. Scanning electron microscopy (SEM) analysis showed that the nanocomposite had a spherical morphology. Transmission electron microscopy (TEM) analysis found that the structure of the nanocomposite was carbon coated with TiO2.

Synthesis of silver nanoparticles using large-area arc discharge and its application in electronic packaging

Silver nanoparticles were efficiently synthesized by large-area arc discharge in liquid and were found to be effective as bonding materials in power microelectronic packaging. The results showed that the production rate of silver nanoparticles depended on the heat input during processing and reached the maximum value of 350 mg/min at current 104 A, which was much higher than any previously reported productivity by the arc discharge method. The silver nanoparticles were characterized in terms of their microstructure, morphology, particle size, and distribution. Two Gaussian peaks were found in the nanoparticle size distribution curve, which were 33 and 220 nm, respectively. This mixed-size nanoparticle paste was naturally economical and effective for the packaging application due to the combination of the high surface energy of small nanoparticles and the efficient joint filling of the large nanoparticles. The cross-section microstructure and fracture surface of bonded joints indicated that atomic bonds formed between the sintered layer and the substrates. Additionally, the mechanism of arc discharge for synthesizing the silver nanoparticles was discussed.

Fabrication of Carbon Nanomaterial Using Arc-Discharge in Liquid Method for Battery Application

This work aims to fabricate carbon-based nanomaterial using arc-discharge in liquid which is much simple and cheap compared to other techniques i.e., CVD, laser vaporization, etc. The experiment were performed using intermediate DC power supply (1300 W) to produce arc, and commercial graphite pencils (with 5 mm diameter) as negative and positive electrodes. Deionized water was used as heat absorber. The result shows that arc discharge in deionized water could effectively produce carbon nanomaterial (i.e., graphene and CNT). In adddition, finite element method-based simulation of different intercalating process of Li-ion to different shape of anode i.e., bulk and phorous anode materials for battery application is also presented in order to provide support for design of Li-ion battery based on carbon nanomaterial.

ZnO nanoparticles decorated on graphene sheets through liquid arc discharge approach with enhanced photocatalytic performance under visible-light

We present an innovative approach for synthesis of zinc oxide–graphene (ZnO–G) hybrid nanostructures through combination of improved hummer and arc discharge methods in liquid. A detailed study of the considerable visible-light photocatalytic activities of these nanostructures for the degradation of Phenol red (PR) and Methyl orange (MO) as standard organic compounds under the irradiation of 90W halogen light for 2h has been performed. The ZnO–G nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer Emmett Teller (BET) and ultra violet–visible absorption spectroscopy (UV–vis). The results revealed that the ZnO–G nanostructures extended the light absorption spectrum toward the visible region and remarkably enhanced the photodegradation of standard dyes under visible-light irradiation. It has been confirmed that the ZnO–G nanostructures could be excited by visible-light (E∼2.6eV). The major enhancement in the photocatalytic activity of ZnO–G nanostructures under visible-light irradiation can be attributed to the effect of electron transport among ZnO nanoparticles (NPs) and graphene sheets. A mechanism for photocatalytic degradation of organic pollutants over ZnO–G photocatalyst was proposed based on our observations.

The Effect of Dissolved Oxygen in Arc Medium on Crystal Structure and Optical Properties of Iron Based Nanoparticles Prepared via Dc Arc Discharge in Water

Electrical arc discharge in liquid is a fast, cost-effective and an environmentally benign way for synthesis of nanomaterials. In this research iron based nanoparticles were synthesized via DC arc discharge submerging in deoxidized water and the effect of dissolved oxygen in arc discharge medium on morphology, crystal structure and optical properties of nanoparticles were studied. For nanoparticle synthesis a discharge current of 40 A was applied between pure iron electrodes which were submerged in deoxidized water and kept about 8cm below the surface of water. Dissolved oxygen removal was performed by nitrogen gas bubbling for long time before arc discharge. Furthermore during synthesis a pressurized stream of nitrogen gas was directed perpendicular to the surface of deoxidized water. In addition, a sample was prepared in water without deoxidization under the same synthesis condition. The nanoparticles were characterized by X-ray diffraction (XRD), UV-visible spectroscopy and scanning electron microscopy (SEM). SEM results revealed that the particles were spherical with aspect ratios of about one. The average size of nanoparticle is below 30nm in both samples. It was concluded that the reaction of dissolved oxygen molecules available in deionized water with iron nanoparticles leads to oxidation of nanoparticles during nucleation, nanoparticles formation and especially after synthesis. Therefore the oxygen atom in water molecules and oxygen ions in arc plasma do not have a significant effect on oxidation of nanoparticles. These results demonstrate the importance of oxygen removal of water in arc discharge method for preparation of pure metallic nanoparticles without considerable oxidation.

The Effect of Liquid Environment on Composition, Colloidal Stability and Optical Properties of Nickel Nanoparticles Synthesized by Arc Discharge in Liquid

In this research, nickel nanoparticles were synthesized by arc discharge in different liquid media including deionized water, acetone, ethanol and methanol. Arc discharge is created with applying constant current 40 A between two nickel electrodes. Scanning electron microscopy (SEM), UV-visible spectroscopy and X-ray diffraction (XRD) were used for samples characterization. According to UV-visible spectra, nanoparticles synthesized in deionized water demonstrate metal oxide nanoparticles characteristic, but in organic media metallic nanoparticles were obtained. According to SEM images, the particle size of synthesized nanoparticles in deionized water, ethanol, methanol, and acetone are 25, 31, 38, and 45nm respectively. Also SEM images revealed spherical nanoparticles with broad size distributions in all media, but the narrowest size distribution was observed in deionized water. Furthermore, synthesized nanoparticles in deionized water sedimented after a week. On the other hand, synthesized nanoparticles in organic media were stabled for long periods of time without sedimentation. It is noticeable that the most stable nanoparticles were observed in acetone. Oxidation of nanoparticles in water and perfect colloidal stability in acetone could be explained via reaction of dissolved oxygen in water with nickel nanoparticles and dipole-dipole interaction of acetone molecules with nanoparticles respectively.

Optical Properties of Ag-Cu Alloy Nanoparticles Synthesized by DC Arc Discharge in Liquid

Alloy nanoparticles are much interesting because their properties are flexible and can be very distinct with the particles of their constituents. Optical properties of alloy nanoparticles can differ by size effects and composition of their pure components. The aim of this article is studying the alloying and optical properties of Cu-Ag nanoparticles prepared via DC arc discharge in water with two different experimental procedures. Arc discharge was ignited between two pure silver and copper electrodes and two types of sample productions were held. The first one was based on using copper and silver wire with 99.99% purity as an anode and cathode electrodes and at the same 3mm diameter in each part by two different 40, 50 A current. Second one was using reversed sited electrodes. Optical properties, size and crystal structure of nanoparticles were characterized by UV-visible spectroscopy, Field Emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) respectively. SEM images show the nanoparticles are spherical with the average size of lower than 30nm for all samples. XRD results shows there are some displacements in Bragg diffraction angles of silver XRD peaks which is due to the positioning of Cu atoms among silver atoms and synthesis of Ag-Cu alloy nanoparticles. However some Ag-Cu alloy peaks were also observed. In comparison with the optical extinctions of pure copper and silver nanoparticles the optical extinctions of samples have the characteristic optical extinction of Ag-Cu alloy nanoparticles with extinction peak due to surface plasmon resonance that was observed between silver and copper nanoparticles extinction peaks. In addition optical properties of Ag-Cu alloy are more adjustable with arc current when using copper and silver wire as anode and cathode electrode respectively. The results provide a simple and flexible method for preparation and tuning optical properties of Ag-Cu nanoparticles.

Seed Mediated Growth of Gold Nanoparticles Based on Liquid Arc Discharge

We report studies on the growth of gold nanoparticles by a seed-mediated approach in solution. The synthetic method is adapted from one we published earlier (Ashkarran et al. Appl. Phys. A 2009, 96, 423). The synthesized gold nanoparticles were characterized by X-ray diffraction (XRD), dynamic light scattering (DLS), UV-Vis spectroscopy, optical imaging and atomic force microscopy (AFM). Optical absorption spectroscopy of the prepared samples at 15 A arc current in HAuCl4 solution shows a surface plasmon resonance around 520 nm. It is found that sodium citrate acts as a stabilizer and surface capping agent of the colloidal nanoparticles. The intensity of the plasmonic peak of the prepared gold nanoparticles for 1 minute arc duration gradually increases due to seed mediation for up to 6 hours. The formation time of gold nanoparticles at higher seed concentrations is less than that at lower seed concentrations.

A twice liquid arc discharge approach for synthesis of visible-light-active nanocrystalline Ag:ZnO photocatalyst

Ag:ZnO hybrid nanostructures were successfully prepared by a twice arc discharge method in liquid. The visible light photocatalytic activities were successfully demonstrated for the degradation of Rhodamine B (Rh. B), Methyl orange (MO), and Methylene blue (MB) as standard organic compounds under the irradiation of 90 W halogen light for 2 h. The Ag:ZnO nanostructures were characterized by X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and ultraviolet-visible absorption spectroscopy (UV-Vis). The results revealed that the Ag:ZnO nanostructures extended the light absorption spectrum toward the visible region and significantly enhanced the Rh. B photodegradation under visible light irradiation. 3 mM Ag:ZnO nanostructures exhibited highest photocatalytic efficiency. It has been confirmed that the Ag:ZnO nanostructures could be excited by visible light (E<3.3 eV). The significant enhancement in the Ag:ZnO nanostructures photocatalytic activity under visible light irradiation can be ascribed to the effect of physisorbed noble metal Ag by acting as electron traps in ZnO band gap. A mechanism for photocatalytic degradation of organic pollutant over Ag:ZnO photocatalyst was proposed based on our observations.

Instant, template-free and fluorine-free synthesis of TiO2 nanotube arrays with a room-temperature solid–liquid arc discharge technique

An alternating current-based electrochemical spark discharge process was utilized to fabricate TiO2 nanotube arrays, not using any template and fluorine species.

Synthesis and characterization of gold nanoparticles via submerged arc discharge based on a seed-mediated approach

Gold nanoparticles were prepared via liquid arc discharge technique using a seed-mediated approach in solution and characterized by dynamic light scattering, UV–vis spectroscopy, X-ray diffraction, optical imaging, and atomic force microscopy. A surface plasmon resonance was observed around 520 nm based on optical absorption spectroscopy of as-prepared samples at 15 A arc current in HAuCl4 solution. It was found that sodium citrate acts as a stabilizer and surface capping agent of the colloidal nanoparticles. It was found that the intensity of the plasmonic peak of as-prepared gold nanoparticles in 1 min arc duration gradually increases due to seed mediation up to 6 h. The formation time of gold nanoparticles in higher seed concentrations is less than the lower seed concentrations.

Influence of the solution temperature on carbon nanotube formation by arc discharge method

Carbon nanotubes (CNTs) represent an important group of nanomaterials with attractive geometrical, electrical and chemical properties and are synthesised using a variety of techniques. In this study, CNTs are fabricated by arc discharge in liquid with a fully automatic setup, while this system is equipped with a heat exchange system. This fully automatic setup enables the controlling of gap between the two electrodes and temperature of the media. Furthermore, this system can cool down the solution that is heated due to arc and keep the temperature of solution constant during the arc discharge. The temperature of the solution affects the synthesising and structuring of CNTs. In this study, CNTs are fabricated between two graphite electrodes, which are submerged in LiCl (0.25 N) and with a voltage of 25 V, while Ni and Mo are used as catalysts. For comparative study, CNTs are synthesised under different thermal conditions, below zero, at environment temperature and at high temperature (up to 80°C), and the results are analysed, compared and discussed. The scanning electron microscopy, transmission electron microscopy and Raman spectroscopy are employed to study the morphology of these carbon nanostructures. The general impact of the solution temperature upon nanoproduct structures will be discussed.

A novel method for synthesis of colloidal silver nanoparticles by arc discharge in liquid

This paper presents a novel, inexpensive and one-step approach for synthesis of silver nanoparticles (Ag NPs) using arc discharge between titanium electrodes in AgNO 3 solution. The resulting nanoparticles were characterized using UV–Vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Silver nanoparticles of 18 nm diameter were formed during reduction of AgNO 3 in plasma discharge zone. Optical absorption spectroscopy of as prepared samples at 15 A arc current in AgNO 3 solution shows a surface plasmon resonance around 410 nm. It was found that sodium citrate acts as a stabilizer and surface capping agent of the colloidal nanoparticles. SEM images exhibit the increase of reduced nanoparticles in 6 min arc duration compared with 1 min arc duration. TEM image of the sample prepared at 6 min arc duration shows narrow size distribution with 18 nm mean particle size. Antibacterial activities of silver nanoparticles were investigated at the presence of Escherichia coli (E-coli) bacteria.

Enhancing effect of monoolein surfactant on carbon nanoparticle synthesis by arc discharge in liquid

Effect of monoolein surfactant which promotes n-hexane to dissolve in water was investigated to enhance the carbon nanoparticle (CNP) synthesis by arc discharge in liquid. The production rate of CNPs consisting of multi-shelled fullerenes and multi-walled carbon nanotubes was increased by the addition of the n-hexane to water with support of monoolein surfactant. An optimal amount of monoolein led to the maximal production rate of CNPs which was ca. two-fold higher than that obtained from a pure water system. This effect is ascribed to the role of n-hexane and monoolein to provide carbon clusters to the arc reactive zone. The hydrodynamic particle sizes of CNPs and their crystallinity were also enhanced by the addition of these organic compounds. As the vapor pressure of the organic component is significantly suppressed, the proposed method is much safer than that using pure organic liquid.

Effects of gravity on single-wall carbon nanotubes synthesized by arc in water

The method using arc discharge in liquid is a simple and inexpensive route for synthesis of carbon nanotubes and other related nano-materials. In this study, we report the synthesis of single-wall carbon nanotubes (SWCNTs) by means of the arc-in-water method under extremely low gravity conditions. The strong heat convection caused by the arc plasma is suppressed under such conditions. Therefore, the boiling flow behavior and temperature distribution have been stabilized in low gravity. As a result, the possibility of the chirality control of SWCNTs by applying extremely low gravity was revealed; namely, the yield of semiconducting SWCNTs was increased and several SWCNTs of specific diameters turned out to be prominent under extremely low gravity conditions.

Influence of transverse magnetic field on the formation of carbon nano-materials by arc discharge in liquid

To change the structures and yields of carbon nano-products, transverse magnetic field (TMF) was introduced to arc discharge in liquid (de-ionized water, liquid nitrogen). Direct current was used to sustain the arc discharge between two graphite electrodes and cobalt powder was filled in drilled anodes as catalyst sometimes. Scanning electron microscopy and high-resolution transmission electron microscopy were used to investigate the nano-products. Some novel carbon nano-structures were obtained with the effect of TMF. For arc discharge in water, curled multi-walled carbon nanotubes and nano-structures with few layers were found in cathode depositions and floating products, respectively. For arc discharge in liquid nitrogen, twists of single-walled carbon nanotubes appeared in cathode depositions and the yields of spherical nano-particles in floating products increased.