Magnetic Iron Sulfide Nanoparticles for Potential Applications in Gas Sensing
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Magnetic Iron Sulfide Nanoparticles for Potential Applications in Gas Sensing Sixberth Mlowe,1 Shivram Sopan Garje,2 Thomas Moyo3 and Neerish Revaprasadu1 1 Department of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa, 3886, South Africa. E-mail: [email protected] 2 Department of Chemistry, University of Mumbai Vidyanagari, Santacruz (E), Mumbai 400 098, India. 3 School of Chemistry and Physics, Westville Campus, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa. ABSTRACT The crystal structure and phase transformations of iron sulfide nanomaterials have interesting properties that can be utilized in solar cells, biological and other applications. Iron (III) complexes piperidine (1) and tetrahydroquinoline (2) dithiocarbamate have been synthesized and subsequently utilized as single source precursors for the preparation of iron sulfide nanoparticles by solvothermal and pyrolysis methods. The powder X-ray diffraction (pXRD) studies gave crystalline information of the iron sulfide nanoparticles which were dependent on the reaction conditions. Only the greigite phase (Fe3S4) was obtained when the solvothermal method was used during the synthesis. The pyrolysis method gave a mixture of pyrite (FeS2) and pyrrhotite phases when complex (1) was used while complex (2) gave pure pyrrhotite. Well interconnected microstructures and nanoflakes-like structures were obtained by scanning electron microscopy imaging. Furthermore, magnetic properties of the as-synthesized nanoparticles displayed ferromagnetic and antiferromagnetic behaviour, typical of greigite and pyrrhotite nanoparticles respectively. A direct band gap of 2.70 eV was obtained according to optical absorption studies. INTRODUCTION Iron sulfide nanomaterials are among interesting classes of nanomaterials which support and enhance solar cells, biological and catalytic applications [1-4]. The iron sulfide compound exists in several phases which include greigite (Fe3S4), pyrrhotite (Fe1-xS), pyrite (FeS2), marcasite (FeS2), troilite (FeS) and mackinawite (FeS) [5]. The phase transformations on the crystal structure of iron sulfide are complex. The phase diagrams of iron-sulfur compounds are multifaceted, and a small variation in stoichiometry often leads to drastic changes in structural, magnetic, electronic and physical properties of the material. Thus, the preparation of a purephase iron sulfide compounds still remains a challenge. Disale et al. prepared nanocrystalline FeS and FeS2 from iron(II) cinnamaldehyde thiosemicarbazone complexes as single source precursors by solvothermal and pyrolysis methods [6].Wang and co-workers synthesized phase pure Fe3S4 and Fe7S8 nanostructures by thermal decomposition of iron(III) diethyldithiocarbamate complexes in a mixture of solvents (oleic acid/oleylamine/octadecene) [7]. Furthermore, other examples of iron(III) xanthates complexes have been explored to fabricate iron sulfide nanoparticles using various coordinating solvents [8]. The overall observation was that both morphol
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