Emil Omurzak

Wurtzite-type ZnS nanoparticles by pulsed electric discharge

The synthesis of wurtzite-type ZnS nanoparticles by an electric discharge submerged in molten sulfur is reported. Using a pulsed plasma between two zinc electrodes of diameter 5 mm in molten sulfur, we have synthesized high-temperature phase (wurtzite-type) ZnS nanocrystals with an average size of about 20 nm. The refined lattice parameters of the synthesized wurtzite-type ZnS nanoparticles were found to be larger than those of the reported ZnS (JCPDS card no 36-1450). Synthesis of ZnMgS (solid solution of ZnS and MgS) was achieved by using ZnMg alloys as both cathode and anode electrodes. UV-visible absorption spectroscopy analysis showed that the absorption peak of the as-prepared ZnS sample (319 nm) displays a blue-shift compared to the bulk ZnS (335 nm). Photoluminescence spectra of the samples revealed peaks at 340, 397, 423, 455 and 471 nm, which were related to excitonic emission and stoichiometric defects.

High temperature stable WC1−x@C and TiC@C core–shell nanoparticles by pulsed plasma in liquid

High temperature phase tungsten carbide and titanium carbide coated with graphitic carbon (WC1−x@C and TiC@C) nanoparticles were synthesized by pulsed plasma in liquid. HRTEM results show that the average size of WC1−x@C and TiC@C nanoparticles are 30 and 35 nm, respectively. Raman spectroscopy revealed well-organized graphitic coatings, which make the nanoparticles stable at higher temperatures and resistant to oxidation. Refinement of the XRD profiles showed larger cell parameters compared to JCPDS cards. Furthermore, thermogravimetric analyses showed the higher thermal stability up to 601 and 543.4 °C, for the WC1−x@C and TiC@C nanoparticles, these are 43% and 36% more compared to the thermal stability of previously reported nanoparticles, which degraded at around 350 °C.

Pulsed Plasma Synthesis of Iron and Nickel Nanoparticles Coated by Carbon for Medical Applications

Fe and Ni magnetic nanoparticles coated by carbon were synthesized between the Fe–Fe and Ni–Ni metal electrodes, submerged in ethanol using pulsed plasma in a liquid method. Iron coated carbon (Fe@C) nanoparticles have an average size of 32 nm, and Ni@C nanoparticles are 40 nm. Obtained samples exhibit a well-defined crystalline structure of the inner Fe and Ni cores, encapsulated in the graphitic carbon coatings. Cytotoxicity studies performed on the MCF-7 (breast cancer) cell line showed small toxicity about 88–74% at 50 µg/mL of Fe@C and Ni@C nanoparticles, which can be significant criteria for use them in medical cancer treatment. In addition, appropriate sizes, good magnetic properties and well-organized graphitic carbon coatings are highlight merits of Fe@C and Ni@C nanoparticles synthesized by pulsed plasma.

Effect of shock compression on wurtzite-type ZnMgS crystals

It is hard to generate twin defects in wurtzite-type ZnMS (M: metal element) crystals by static mechanical method, while it is important for the luminescence. It was found that many twin defects were formed in wurtzite-type ZnMgS crystals by shock compression of >15 GPa in stress, and the absorption and luminescence spectra changed.

Synthesis of wurtzite-type ZnMgS by the pulsed plasma in liquid

Wurtzite-type ZnMgS (w-ZnMgS) nanoparticles were synthesized using the pulsed plasma in liquid method. By the pulsed plasma generated between two electrodes made of ZnMg alloy in liquid sulfur, we produced w-ZnMgS nanocrystals mixed with Zn2Mg and MgS. Higher purity w-ZnMgS sample was achieved by annealing at 773 K. The synthesized ZnMgS nanoparticles were of spherical shape and contained of many crystal defects (stacking faults). Ultraviolet?visible (UV?vis) absorption spectroscopy analysis of the synthesized w-ZnMgS showed absorption edge broadening and appearance of a small absorption band at around 400 nm even without doping.

Synthesis of WO3·H2O nanoparticles by pulsed plasma in liquid

Pure orthorhombic-phase WO3·H2O nanoparticles with sizes of about 5 nm were synthesized by pulsed plasma in deionized water, in which tungsten electrodes provide the source of tungsten and the water is the source of oxygen and hydrogen. The quenching effect and liquid environment inherent in this pulsed plasma in liquid method resulted in ultra-small particles with lattice lengths (a = 5.2516 A, b = 10.4345 A, c = 5.1380 A) larger than those of reference lattices. The emission lines of W I atoms, W II ions and H I atoms were observed by an optical emission spectrum in order to gather information on the synthetic mechanism. These nanoparticles showed higher absorption in the visible region than did ST-01 TiO2 and Wako WO3 nanoparticles. The WO3·H2O nanoparticles displayed more activity in the photocatalytic test than did the commercial TiO2 sample (ST-01). Also, the absorption edge of WO3·H2O shifted to longer wavelengths in the UV-Vis absorption pattern relative to that of the anhydrous tungsten oxide.

Magnetite Nanoparticles Synthesized Using Pulsed Plasma in Liquid

Iron oxide nanoparticles have attracted much attention over the last few years owing to their fundamental importance and technological applications. In this work, spherical ferromagnetic Fe3O4 nanoparticles with an average diameter of 19 nm were synthesized by a simple and one-step method, pulsed plasma in liquid. Pulsed plasma, induced by a low-voltage spark discharge, was submerged in a dielectric liquid at a voltage of 200 V, a current of 6 A, a frequency of 60 Hz, and a single discharge duration of 10 µs. Water with different concentrations of 1-hexadecylpyridinium bromide (CPyB) was applied as a liquid, and several experiments made evident that the surfactant concentration affects the phase compositions of the produced materials. The purity of the magnetite phase in the sample increased (from 65 to 98%) with increasing CPyB concentration (from 0.10 to 0.84 g) in 200 ml of water. The crystal structure of magnetite (Fe3O4) nanoparticles with the Fdm space group and a lattice parameter of a = 0.8393 nm was evident from X-ray diffraction results. Magnetite nanoparticles were investigated further by high-resolution transmission electron microscopy/energy-dispersive spectroscopy and thermogravimetrical analysis, and using a vibrating sample magnetometer.

Shock compression of synthetic opal

Structural change of synthetic opal by shock-wave compression up to 38.1 GPa has been investigated by using SEM, X-ray diffraction method (XRD), Infrared (IR) and Raman spectroscopies. Obtained information may indicate that the dehydration and polymerization of surface silanole due to high shock and residual temperature are very important factors in the structural evolution of synthetic opal by shock compression. Synthetic opal loses opalescence by 10.9 and 18.4 GPa of shock pressures. At 18.4 GPa, dehydration and polymerization of surface silanole and transformation of network structure may occur simultaneously. The 4-membered ring of TO4 tetrahedrons in as synthetic opal may be relaxed to larger ring such as 6-membered ring by high residual temperature. Therefore, the residual temperature may be significantly high at even 18.4 GPa of shock compression. At 23.9 GPa, opal sample recovered the opalescence. Origin of this opalescence may be its layer structure by shock compression. Finally, sample fuse by very high residual temperature at 38.1 GPa and the structure closes to that of fused SiO2 glass. However, internal silanole groups still remain even at 38.1 GPa.

Graphitic Carbon-Coated ZrC- and Co-Nanoparticles Synthesized by Pulsed Plasma in Liquid

Graphitic carbon coated ZrC- and Co-nanoparticles were prepared by pulsed plasma in liquid (PPL); their structures were then investigated by high resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD) and Raman spectroscopy. In the process, metal electrodes were used as the metal source and liquid ethanol as the carbon source. The nanoparticles, with a small diameter size of 10 nm, have clear core/shell structures, indicating their potential for improving anti-oxidation properties and other applications.