Laser-induced modification of composite Cu-C nanosized particles synthesized using a pulsed electrical discharge in a liquid

Composite copper-containing carbon nanosized structures were synthesized in the plasma of a pulsed electrical discharge, initiated between two graphite electrodes in an aqueous copper chloride solution. We studied the effect of laser radiation on the morphology of the nanoparticles formed, whose properties we studied by optical absorption spectroscopy and transmission electron microscopy. We discuss the mechanisms for nanoparticle formation in a discharge submerged in a liquid, and the possibilities for laser-induced modification of the nanoparticles. We estimated the temperature of the nanoparticles when exposed to laser radiation pulses. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 372–378, May–June, 2008.     

Synthesis of tungsten carbide nanopowder via submerged discharge method

Tungsten carbide nanopowder was prepared via pulsed discharge of bulk tungsten and graphite rods immersed in pure ethanol. The effect of discharge parameters on the characteristics of final products was investigated. Structural and morphological characterization of nanopowder was performed by means of X-ray diffraction analysis and transmission electron microscopy. In order to determine the feasibility of using synthesized material as an electrocatalyst, tungsten carbide nanopowder was tested for hydrogen evolution. A correlation was found between morphology of nanoparticles, their phase composition and electrocatalytic activity.     

Laser ablation of gadolinium targets in liquids for nanoparticle preparation

Tight focusing of a sub-picosecond laser pulse in a transparent dielectric provides a mean for localized deposition and plasma formation. A micro-explosion in a confined geometry results in a sub-micron cavity formation. Our numerical simulations show the cavity size is strongly dependent on the parameters of the equation of state such as the Grüneisen coefficient or the latent heat of sublimation. A comparison of numerical simulations with experimental data should allow a tuning of equations of state in the domain of extreme parameters     

Influence of Solvent Polarity and Viscosity on Nonradiative Processes in Oligothiophenes with Intramolecular Charge Transfer

By the methods of luminescence, picosecond spectroscopy, and quantumchemical calculations the mechanisms of electron excitation energy deactivation in some oligothiophenes with intramolecular charge transfer depending on the solvent polarity and viscosity have been investigated. While for 2Npiperidino5(2,2dicyanovinyl)thiophene (PDCVT) the main channel of nonradiative deactivation is the transition to a lower intermediate state with a twisted double bond controlled by the medium viscosity, in the case of (E){2[25piperidino2thienyl]6(trifluoridemethyl)4H4pyranylidene}propanedinitryl (PTFDN) fluorescence quenching is initiated by the solvent polarity. For two other oligothiophenes, 2Npiperidino5cyanothiophene (PCT) and 2Npiperidino5cyanoterthiophene (PCTT), differing in the length of the thiophene chain, we have revealed, along with the effective quenching of fluorescence in shortchain PCT (independent of the solvent polarity and viscosity), an increase in the radiation capacity in PCTT with increasing polarity of the solvent. The possible mechanisms of nonradiative deactivation in the investigated oligothiophenes are discussed.     

Plasma synthesis and treatment of nanosized chalcopyrite particles

We synthesized chalcopyrite (CuFeS2) nanoparticles by methods involving laser ablation and electrical discharge in water. The nanoparticles obtained were exposed to an oxygen/argon plasma of a microwave discharge. The synthesized material was studied by photometry, x-ray diffraction (XRD), and energy dispersive x-ray elemental analysis (EDX), IR spectroscopy, and atomic force electron microscopy (AFM). We have established that the nanoparticles are morphologically stable relative to exposure to plasma fluxes of power ≤1 kW, and can be used as a model system to study processes of interaction between a plasma and minerals.     

Synthesis of nanoparticles using a pulsed electrical discharge in a liquid

We used a pulsed electrical discharge in a liquid to obtain Cu-, WC-, and ZnO-containing nanoparticles. The effect of the discharge current and pulse duration on the morphology and phase composition of the synthesized material was studied by spectrophotometry, transmission electron microscopy, and x-ray diffraction analysis. We discuss possible mechanisms for nanoparticle formation in a discharge submerged in a liquid. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 111–120, January–February, 2008.     

Synthesis of nanosized particles during laser ablation of gold in water

In this paper we report the formation of gold nanoparticles during laser ablation of gold target in water in the absence of any additives. The experiments were carried out by using the radiation of the pulsed Nd:YAG laser, operating at the second (532 nm, 10 ns, 10 Hz), or the fourth harmonic (266 nm) wavelengths. The properties of the nanoparticles were found to be susceptible to the additional 532 and 266 nm laser irradiation. It has been established that both the mean size of the nanoparticles and their stability could be varied by proper selection of the parameters of laser ablation and postirradiation such as laser fluence and wavelength combinations.     

Morphology and optical properties of zinc oxide nanostructures synthesized by the methods of thermal and discharge sputtering

Zinc oxide nanostructures are obtained by the methods of electrothermal and discharge sputtering in gaseous and liquid media. Structure and phase peculiarities of synthesized samples, as well as morphology and luminescence properties of synthesized structures with and without doping are examined. The luminescence spectra of the deposited zinc oxide nanostructures have characteristic luminescence maxima (at λ = 380 and 520 nm) associated with exciton emission and defects in nanocrystals, respectively.     

Adsorption of sodium dodecylsulfate on modified carbon adsorbents

The adsorption of anionic surfactants on carbon adsorbents modified with water-soluble derivatives of natural polymers, cellulose and chitin, is considered with sodium dodecylsulfate taken as an example. It is shown that such modification leads to changes in the adsorption structural characteristics and the particle size distribution of carbon-water suspensions of the original adsorbent, and to the emergence of new functional groups on its surface that are able to interact selectively with adsorbate molecules. It is assumed that adsorption of anionic surfactant on carbon adsorbents under equilibrium conditions proceeds via stepwise filling of the carbon??s porous structure: we first observe volume filling of micropores according to their sizes, and then the formation of a surfactant??s monolayer in mesopores and on the outer surface of the adsorbate. It is established by thermal analysis that the thermal stability of carbon adsorbents is enhanced through the preferential localization of anionic surfactants in micropores. The filling of mesopores and the outer carbon surface by surfactant molecules leads to a regular decrease in thermal stability and an increase in the adsorbent surface??s hydrophilicity.