Synthesis of Sulfide Nanoparticles by the Pulsed Electric Discharge
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Synthesis of Sulfide Nanoparticles by the Pulsed Electric Discharge Emil Omurzak*1, Tsutomu Mashimo2, Saadat Sulaimankulova3 1 Priority Organization for Innovation and Excellence, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan. Tel./Fax: 81 96 342 3934. 2 Shock Wave and Condensed Matter Research Centre, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan. 3 Institute of Chemistry and Chemical Technology, National Academy of Sciences, Chui pr. 267, Bishkek 720071, Kyrgyzstan. *Corresponding author’s e-mail address: [email protected] ABSTRACT Synthesis of wurtzite-type ZnS nanoparticles by an electric discharge submerged in molten sulfur is reported. By the pulsed plasma between two zinc electrodes of 5 mm diameter in molten sulfur, we have synthesized high-temperature phase (wurtzite-type) ZnS nanocrystals with an average size of about 20 nm. Refined lattice parameters of the synthesized wurtzite-type ZnS nanoparticles were found to be larger than those of the reported ZnS (JCPDS 36-1450). UVVisible absorption spectroscopy analysis showed that the absorption peak of the as-prepared ZnS sample (319 nm) displays a blue-shift comparing 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. Synthesis of ZnMgS (solid solution of ZnS and MgS) was achieved by using ZnMg alloys as both cathode and anode electrodes. Also, rocksalt structure MgS was synthesized by using magnesium rods as both cathode and anode electrodes. INTRODUCTION Electric discharge based synthesis methods have proven to be non-toxic, low temperature, simple and promising process for various nanomaterials production. So far, the application of electric discharge for the sulfides was only in the form of assisting process or for purposes other than synthesis (such as coating or sintering). FeS coating was deposited on steel substrate using nano-sized FeS powder as starting material and argon as atmosphere by plasma spraying equipment, where plasma was utilized for coating purpose only [1]. Lithium sulfide – carbon (Li2S-C, Li4SiS4-La2S3) composite material was prepared using mechanical ball-milling and then were sintered by spark-plasma-sintering (SPS) process, where plasma was used for making better bonding between lithium sulfide and carbon [2, 3]. Recently, synthesis of Bi and Sb sulfides using electric discharge assisted mechanical milling was reported [4]. Also, indium sulfide (In2S3) thin film was prepared by plasma-assisted co-evaporation technique, where the indium was supplied by thermal evaporation of indium, while the sulfur was activated using inductively coupled plasma treatment of H2S gas [5]. Synthesis of metal sulfides by anode discharge electrolysis under argon atmosphere at 723 K was reported [6], which is quite different than the electric discharge (spark, arc, glow, etc) methods, on top of that it requires high-temperature and is a slow process to produce sulfides. Here we report
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