Deposition of iron sulfide nanocrystals from single source precursors† Masood Akhtar, Javeed Akhter, M. Azad Malik, Paul O’Brien, * Floriana Tuna, James Raftery and Madeleine Helliwell Received 16th February 2011, Accepted 19th April 2011 DOI: 10.1039/c1jm10703h Symmetrical and unsymmetrical dithiocarbamato complexes of iron(III) with the general formula [Fe (S 2 CNRR 0 ) 3 ] where R ¼ Et, R 0 ¼ i Pr (1); R,R 0 ¼ Hex (2); R ¼ Me, R 0 ¼ Et (3); and R,R 0 ¼ Et (4) have been used as single source precursors to synthesize iron sulfide nanocrystals by thermolysis in oleylamine, hexadecyleamine and octadecene at different temperatures. The nanocrystals obtained were studied by p-XRD and TEM and magnetic measurements. Nanocrystals of iron sulfide with greigite, pyrrhotite and mixed phase were grown at different thermolysis temperatures from each precursor. The precursors with shorter alkyl chain length required higher temperature to give the product. Symmetrical alkyl groups with longer chain alkyl groups gave pure greigite phase at lower thermolysis temperature of 170  C but a mixture of greigite and pyrrhotite at higher temperatures. The unsymmetrical alkyl groups gave mixed phase (greigite and pyrrhotite) iron sulfide nanocrystals at all temperatures. Iron sulfides are an interesting class of materials with many different forms, which include: pyrite (cubic-FeS 2 ), marcasite (calcium chloride structure-FeS 2 ), troilite (FeS), mackinawite (Fe 1+x S), pyrrhotite (Fe 1x S, Fe 7 S 8 ), smythite (hexagonal-Fe 3 S 4 ) and greigite (cubic spinel-Fe 3 S 4 ). 1,2 Iron sulfides exhibit a wide range of properties from the semiconducting, nanomagnetic pyrite (FeS 2 ) to ferromagnetic Fe 3 S 4. 3,4 Various types of iron sulfides with various Fe : S ratios, ranging from 0.5 to 1.05, are found in nature. The magnetic and electrical properties of iron sulfides are dependent on the stoichiometric ratio between iron and sulfur. 5,6 Among the natural iron sulfide minerals, mack- inawite is paramagnetic; pyrite and marcasite are diamagnetic; pyrrhotite and greigite are ferromagnetic; and troilite is antiferromagnetic. 2,7,8 Considerable interest has developed in the synthesis and characterization of iron containing nanocrystals, 9–11 due to their potential applications in: information storage devices, catalysis, biomedicine, imaging, and sensors. 12 Whilst the synthesis of iron oxide nanomaterials is well documented, the preparation of iron chalcogenide [Fe(S, Se, Te)] nanomaterials has remained unex- plored until recently. 13–16 This omission may be due their complex crystal structures and physical properties. 17 Iron sulfide synthesis is challenging as small stoichiometry variations lead to large changes in the structural, chemical, and physical properties. Recently Vanitha and O’Brien prepared pyrrhotite Fe 7 S 8 nanocrystals from a single source cubane-type Fe–S cluster by thermolysis in octyleamine at 180  C and greigite Fe 3 S 4 in dodecylamine at 200  C. 13 Feng et al. prepared uniform 3D Fe 3 S 4 flower-like microspheres by a hydrothermal reaction using L-cysteine as a source of sulfur and as a coordinating ligand. 14 Pyrrhotite nanosheets and nanorods also have been prepared by a high temperature approach in Keck Interferometer (KI) flux using sulfur and iron powders as the starting mate- rials. 18 Intracellular pyrrhotite and greigite nanocrystals are synthesised by some magnetotacticbacteria. 19–21 Rao et al. synthesized the nanowires of iron sulfides such as Fe 7 S 8 and Fe 1x S by the thermal decomposition of Fe 1x S(en) 0.5 (en: ethylenediamine) in ethylenediamine. 22 Alivisatos et al. reported the preparation of pyrite FeS 2 nanocrystals by thermolysing the single source precursor tris(diethyldithiophosphato)iron(III) [Fe (S 2 P (EtO) 2 ) 3 ] in hexadecyltrimethylammonium bromide (CTAB) at 200  C in a Teflon lined stainless steel acid digestion bomb. 23 p-XRD studies on the materials prepared showed the deposition of cubic pyrite FeS 2 without any noticeable impurity peaks from orthorhombic marcasite FeS 2 or hexagonal troilite FeS. Greigite Fe 3 S 4 and pyrrhotite Fe 7 S 8 nanosheets were prepared by Han and Gao from tris(diethyldithiocarbamato)iron (III) (Fe(S 2 CNEt 2 ) 3 ) and bis(diethyldithiocarbamato)Fe (II) : 1,10-phenanthroline [Fe(S 2 CNEt 2 ) 2 (phen)] by thermolysis in oleylamine at 240–320  C. 24 Wang et al. reported the synthesis of various iron sulfide nanostructures including nanocrystals, nanoribbons and nanoplates using the same complexes in The School of Chemistry and the School of Materials, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK. E-mail: paul. obrien@manchester.ac.uk; Fax: +44 (0)161 275 4598; Tel: +44 (0)161 275 4653 † Crystal data: CCDC reference numbers 776129 and 776131. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c1jm10703h This journal is ª The Royal Society of Chemistry 2011 J. Mater. Chem. Dynamic Article Links C < Journal of Materials Chemistry Cite this: DOI: 10.1039/c1jm10703h www.rsc.org/materials PAPER Downloaded by John Rylands University Library on 01 June 2011 Published on 31 May 2011 on http://pubs.rsc.org | doi:10.1039/C1JM10703H View Online