Synthesis and modification of molecular nanoparticles in electrical discharge plasma in liquids

Abstract

A review of studies on the synthesis and modification of nanosized particles by electrical discharges in liquid media is presented. The modern understanding of the mechanisms of initiation and features of discharge evolution in liquids are analyzed. By using of the spectroscopic diagnostics, parameters of the discharge plasma in liquids (water, ethanol) are determined. It is shown that the pulsed electrical discharge between electrodes immersed in a nonconducting or weakly conducting liquid, provides a simple and effective method for the synthesis of nanoparticles of different compositions with the average size ranging from 5 to 50 nm. The morphology, phase structure, and composition of the particles formed are defined by the discharge mode and composition of the liquid medium in which the discharge is produced. The conditions for the synthesis of nanosized metal oxides, carbides, and silicides (for example, copper and zinc oxides, titanium and tungsten carbides, gadolinium silicides) were found. Zinc oxide nanoparticles were produced in pulsed electrical discharge plasma in distilled water, and the possibility of their doping with nitrogen atoms during synthesis was demonstrated. Experimental results on the modification of tungsten and copper powders by spark discharge in ethanol are discussed. The possibility to synthesize copper chalcogenides CuInSe 2 by electrical discharge treatment of a mixture of copper, indium, and selenium powders was demonstrated.wide range of nanomaterials (metals and intermetallics, nitrides, metal oxides and carbides, composite materials).Electrical discharge in liquids is accompanied by a complex of physical and chemical phenomena, including shock wave generation, cavitation processes, formation of a vapor-gas bubble and its pulsation, ionization and decomposition of liquid molecules in the plasma channel and around it, intense UV and sound radiation, and pulsed electric and magnetic fields. These processes generate free radicals, singlet oxygen, ozone, and hydrogen peroxide. Furthermore, electrode erosion results in release into the liquid of atoms and ions of the electrode materials. These excited or ionized particles take part in diverse physicochemical processes that affect the liquid and objects placed in it. A great variety of compounds, including metastable ones, can form in the plasma channel. Nanoparticles are formed by chemical reactions of atoms and ions released from electrodes with the decomposition products of the surrounding liquid.

Filamentation of diamond nanoparticles treated in underwater corona discharge

“…In contrast to the gas phase discharge, the underwater discharge enables uniform surface treatment of all diamond nanoparticles in the batch. In accordance with other works [48][49][50][51] we suppose that the underwater discharge combined with a reactive gas supply and/or solutions of donor substances may provide different surface functionalities of DNPs (via oxidation, nitration, hydroxylation, etc.). Moreover, since relatively large amount of treated nanoparticles can be simply processed at low cost (specic power dosage 500 W g À1 ), the presented method of DNPs modication seems to be suitable for industrial production.…”

Aqueous dispersion of hexagonal boron nitride via plasma processing in a hydroquinone solution

“…Plasmas in solution provide highly reactive species such as oxygen, hydrogen, and hydroxyl radicals that react with materials in aqueous media [1,3]. The dispersion of nanoparticles via plasma processing in the solution and its applications have received the attention of researchers [4,10]. Surface modification via functionalization by plasmas in solution was conducted for carbon nanomaterials [4,6] and metallic nanoparticles [7,10] to improve their aqueous dispersibility and compatibility with polymers, occasionally combined with additives [11,12].…”

“…The dispersion of nanoparticles via plasma processing in the solution and its applications have received the attention of researchers [4,10]. Surface modification via functionalization by plasmas in solution was conducted for carbon nanomaterials [4,6] and metallic nanoparticles [7,10] to improve their aqueous dispersibility and compatibility with polymers, occasionally combined with additives [11,12]. As an example of aqueous dispersed carbon nanotubes (CNTs), added solubilizers such as aromatic compounds and catechins are effective for dispersing CNTs in water [13,14], and dispersion via plasmas in solution for CNTs is enhanced by adding molecules such as ammonia, and amino acid to introduce functional groups [5,11].…”

Synthesis of Cu@ZnO core–shell nanoparticles by spark discharges in liquid nitrogen

“…If the synthesis of copper oxides and zinc oxide NPs by discharges in liquids have been amply investigated [11][12][13][14][15][16], the same is not true for core-shell structures and alloys. Panuthai et al [17] eroded copper-zinc (Cu-Zn) alloy electrodes with different copper contents (90Cu/10Zn and 65Cu/35Zn) by an arc discharge submerged in glycol, ethanol and deionized water.…”