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Materials Letters 01/2013; · 2.31 Impact Factor
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Chemistry of Materials 01/2013; 25:266. · 7.29 Impact Factor
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01/2013;
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ABSTRACT: The iron pivalate clusters [Fe(3)O(O(2)C(t)Bu)(6)(H(2)O)(3)](O(2)C(t)Bu)·HO(2)C(t)Bu (), [Fe(8)(OH)(4)(O(2)C(t)Bu)(12)(OC(6)H(4)C(6)H(5))(8)] () and [Fe(3)O(O(2)C(t)Bu)(6)(C(5)H(5)N)(3)] () have been used as single source precursors to synthesise iron oxide nanoparticles by a hot injection thermal decomposition method in oleylamine, hexadecanol, oleic acid, oleylamine/oleic acid with dodecanol or octyl ether as solvent. The effect of the different reaction parameters such as temperature, reaction time and capping agents on the phase and morphology were studied. The reaction time was studied for () by thermolysis in a mixture of oleylamine, oleic acid, hexadecanol and dodecanol (solvent) at 260 °C. The results obtained showed that a mixture of maghemite-C (Fe(2)O(3)) and magnetite (Fe(3)O(4)) were obtained for aliquots withdrawn for reaction times of less than 30 minutes whilst only magnetite was obtained after one hour. The nanoparticles were characterised by p-XRD, TEM and magnetic measurements. TEM showed that monodispersed magnetite particles were obtained when the precursor was injected at the boiling point of the solvent. The diameter of the monodispersed nanoparticles obtained by the thermolysis of [Fe(3)O(O(2)C(t)Bu)(6)(H(2)O)(3)](O(2)C(t)Bu)·HO(2)C(t)Bu () in oleylamine, hexadecanol, oleic acid with dodecanol or octyl ether as solvent were 4.3 ± 0.4 and 4.9 ± 0.5 nm respectively. Magnetic measurements revealed that all the particles are superparamagnetic.
Dalton Transactions 11/2012; · 3.84 Impact Factor
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ABSTRACT: The complex tris(N,N-diethyl-N’-naphthoylselenoureato)iron(III) was synthesised and its X-ray single crystal structure determined. Thermolysis of this complex in oleylamine at all temperatures produced nanocrystals of FeSe2 whereas Aerosol Assisted Chemical Vapour Deposition produced FeSe thin films on silicon substrates. Nanocrystals and thin films were characterised by powder X-ray Diffraction (p-XRD), Scanning Electron Microscopy (SEM), Atomic Force microscopy (AFM), and Transmission Electron Microscopy (TEM).
Journal of Materials Chemistry 06/2012; · 5.97 Impact Factor
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ABSTRACT: Power generation through photovoltaics (PV) has been growing at an average rate of 40% per year over the last decade; but has largely been fuelled by conventional Si-based technologies. Such cells involve expensive processing and many alternatives use either toxic, less-abundant and or expensive elements. Kesterite Cu(2)ZnSnS(4) (CZTS) has been identified as a solar energy material composed of both less toxic and more available elements. Power conversion efficiencies of 8.4% (vacuum processing) and 10.1% (non-vacuum processing) from cells constructed using CZTS have been achieved to date. In this article, we review various deposition methods for CZTS thin films and the synthesis of CZTS nanoparticles. Studies of direct relevance to solar cell applications are emphasised and characteristic properties are collated.
Chemical Communications 04/2012; 48(46):5703-14. · 6.17 Impact Factor
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ABSTRACT: CuInSe(2), CuGaSe(2) and CuIn((1-x))Ga(x)Se(2) (CIGS) nanoparticles were synthesised from the diisopropyldiselenophosphinatometal complexes M(x)[(i)Pr(2)PSe(2)](n) (M = Cu(I), In(III), Ga(III); n = 1, 3) by thermal decomposition of the precursors in HDA/TOP at 120-210 °C or 250 °C. The semiconductor nanoparticles obtained were characterized by powder X-ray diffraction (p-XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis. The diameters of the nanoparticles for CuInSe(2), CuGaSe(2) and CuIn(0.7)Ga(0.3)Se(2) were found to be 4.9 ± 0.6 nm (at 180 °C), 13.5 ± 2.9 nm (at 250 °C) and 14 ± 2.22 nm (at 250 °C) respectively. The p-XRD patterns for the nanoparticulate samples were assigned to the corresponding ICDD patterns for tetragonal chalcopyrite phase.
Nanoscale 11/2011; 3(12):5132-9. · 5.91 Impact Factor
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ABSTRACT: Zinc and cadmium complexes of 1,1,5,5-tetraalkyl-2-4-dithiobiurets [M(N(SCNR2)2)2] [M = Zn, R = methy (1), ethyl (2) and M = Cd, R = methyl (4), ethyl (5)] and 1,1,5,5-tetraalkyl-2-thiobiurets [M(SON(CNR2)2)2] [M = Zn, R = isopropyl (3) and M = Cd, R = isopropyl (6)] have been synthesized. The single crystal X-ray structures of complexes (2), (3), (4), and (5) were determined. Thermogravimetric analysis confirmed that all six complexes decomposed in a single step to their corresponding metal sulfides. The complexes were used as single source precursors for the deposition of zinc sulfide (ZnS), cadmium sulfide (CdS), and zinc cadmium sulfide (ZnxCd1−xS) thin films by aerosol assisted chemical vapor deposition (AACVD). The zinc complexes (1) and (3) deposited cubic ZnS films with small rods and granular crystallites at 300 and 350 °C, whereas at 400 and 450 °C hexagonal ZnS with granular crystallites were dominant. Complex (2) gave granular hexagonal ZnS films at all deposition temperatures. Cadmium complexes (4), (5), and (6) gave granular hexagonal CdS films at all deposition temperatures. ZnxCd1−xS films were deposited by varying the relative concentration of precursors (1) and (4), (2) and (5), and (3) and (6) at 400 °C. The formation of a solid solution was confirmed by UV−vis spectroscopy and powder X-ray diffraction. The morphology of the films was studied by scanning electron microscopy and atomic force microscopy. The elemental composition of films was confirmed by energy dispersive X-ray spectroscopy.Keywords: single source precursors; zinc sulfide; cadmium sulfide; zinc cadmium sulfide; thin films
Chemistry of Materials 02/2011; 23:1471. · 7.29 Impact Factor
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Chemical science (Royal Society of Chemistry) 01/2011; 2:1170. · 7.53 Impact Factor
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01/2011;
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Journal of Materials Chemistry 01/2011; 21:17888. · 5.97 Impact Factor
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ABSTRACT: The nickel(II) complexes of several 1,1,5,5-tetraalkyl-2-thiobiurets (R = methyl (1); methyl, ethyl (2); ethyl (3); isopropyl (4)) and 1,1,5,5-tetraalkyl-2,4-dithiobiurets (R = methyl (5); methyl, ethyl (6); ethyl (7)) have been synthesized. The single crystal X-ray structures of complexes (1), (3), (4), (6), and (7) have been determined. Thermogravimetric analysis shows all seven complexes decompose in a single step to one or another form of nickel sulfide. The complexes were used as single-source precursors for the deposition of nickel sulfide thin films by aerosol assisted chemical vapor deposition (AACVD) at temperatures between 320 and 480 °C. Complex (1) gave orthorhombic Ni7S6 at all temperatures with spherical tipped wirelike crystallites and plates. Complex (2) gave mixtures of hexagonal Ni17S18 and orthorhombic Ni7S6 with wires and plates. Complex (3) also led to a mixture of hexagonal Ni17S18 and orthorhombic Ni7S6 phases but with platelike crystallites. In contrast complex (4) gave orthorhombic Ni9S8 with flowerlike structures at 320 and 360 °C and branched structures at 400 °C. Complex (6) gave hexagonal NiS1.03 at 360 and 400 °C, and orthorhombic Ni7S6 at 440 and 480 °C with wires and rods composed of spherical particles. Complex (7) gave rods composed of hexagonal plates with hexagonal NiS1.03 phase at 360 and 400 °C and orthorhombic Ni7S6 at 440 and 480 °C. The composition of films deposited from all these complexes was confirmed by EDX analysis. The influence of the precursors on the nature of the deposited films is discussed.
Chemistry of Materials 11/2010; 22:6328. · 7.29 Impact Factor
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ABSTRACT: Cobalt complexes of 1,1,5,5-tetramethyl-2,4-dithiobiuret, [Co{N(SCNMe(2))(2)}(3)] (1), and 1,1,5,5-tetraisopropyl-2-thiobiuret, [Co{N(SOCN(i)Pr(2))(2)}(2)] (2), have been synthesized and characterized. Both complexes were used as single-molecule precursors for the preparation of cobalt sulphide nanoparticles by thermolysis in hexadecylamine, octadecylamine or oleylamine. The powder X-ray diffraction pattern of as-prepared nanoparticles showed the hexagonal phase of Co(1-x)S from complex 1 and mixtures of cubic and hexagonal Co(4)S(3) from complex 2. Transmission electron microscopy images of material prepared from complex 1 showed spherical and trigonally shaped particles in the size range of 10-15 nm; whereas spheres, rods, trigonal prisms and pentagonally and hexagonally faceted crystallites were observed from complex 2. This observation is the first of the Co(4)S(3) phase in a nanodispersed form.
Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 09/2010; 368(1927):4249-60. · 2.77 Impact Factor
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ABSTRACT: The iron(III) complexes of several 1,1,5,5-tetraalkyl-2-thiobiurets [Fe(SON(CN(i)Pr(2))(2))(3) (1), Fe(2)(μ-OMe)(2)(SON(CNEt(2))(2))(2) (2), Fe(SON(CNEt(2))(2))(3) (3), and Fe(SON(CNMe(2))(2))(3) (4)] have been synthesized, and the single-crystal X-ray structures of 1, 2, and 4 have been determined. The magnetic properties of complex 2 as a function of the temperature and field were studied. Thermogravimetric analysis of complexes 1-4 showed the decomposition in one major step to iron sulfide residues. All four complexes were used as single-source precursors for the deposition of iron sulfide thin films by aerosol-assisted chemical vapor deposition. Complex 1 gave hexagonal troilite FeS films with a small amount of tetragonal pyrrhotites Fe(1-x)S at 300 °C, whereas only troilite FeS was deposited at 350, 400, or 450 °C. Complexes 2 and 3 deposited a mixture of hexagonal troilite FeS and cubic pyrite FeS(2) films at all temperatures. Complex 4 deposited very thin films of FeS at all temperatures as troilite. Scanning electron microscopy images of the films deposited from all complexes showed that the morphology consisted of plates, granules, rods, and sheets like crystallites. The size and shapes of these crystallites were dependent on the growth temperature and the precursor used. This is the first time that iron(III) thiobiuret complexes have been used as single-source precursors for iron sulfide thin films.
Inorganic Chemistry 09/2010; 49(18):8495-503. · 4.60 Impact Factor
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ABSTRACT: The cobalt(III) complexes of 1,1,5,5-tetramethyl- and 1,1,5,5-tetraethyl-2,4-dithiobiuret and the cobalt(II) complex of 1,1,5,5-tetra-iso-propyl-2-thiobiuret have been synthesized. The single-crystal X-ray structure of the thiocyanide (1) and cobalt tetrachlorate (2) salts of the parent cyclized ligand, together with complexes [Co{N(SCNMe2)2}3] (3), [Co{N(SCNEt2)2}3] (4) and [Co{N(SOCNiPr2)2}2] (5) have been determined. The thermal decomposition of 3, 4, and 5 was studied. The complexes were used as single source precursors for the deposition of cobalt sulfide thin films by aerosol assisted chemical vapor deposition (AACVD). The X-ray diffraction (XRD) of the deposited films showed hexagonal Co1−xS from complexes (3) and (4) whereas complex (5) gave a mixture of cubic and hexagonal Co4S3. The morphology of films was characterized by scanning electron microscope (SEM) and showed rod like crystallites from 3, granular crystallites from 4 and stalagmitic structures from 5. Transmission electron microscopy (TEM) of the samples obtained from thin films from 3 and 4 show that the films are composed of hexagonal nanoplates with nanocubes from 5. Magnetic measurements showed the para or ferro-magnetic behavior from crystallites. The mechanism for decomposition of precursors to the cobalt sulfide was studied by pyrolysis gas chromatography (Py-GC-MS).
Chemistry of Materials 08/2010; 22:4919. · 7.29 Impact Factor
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ABSTRACT: The series of nickel dichalcogenoimidodiphosphinates [Ni{(i)Pr(2)P(X1)NP(X2)(i)Pr(2)}(2)]: X1 = S, X2 = Se (1), X1 = X2 = S (2), and X1 = X2 = Se (3) have been successfully used as single-source precursors (SSPs) to deposit thin films of nickel sulfide, selenide or phosphide; the material deposited depended on both temperature and method used for the deposition. Aerosol-assisted (AA) chemical vapour deposition (CVD) and low-pressure (LP) CVD were used. The as-deposited films were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). A variety of phases including: Ni(2)P, Ni(0.85)Se and NiS(1.03) were deposited under different conditions. The mechanism of decomposition to the phosphide, selenide, or sulfide was studied by pyrolysis gas chromatography mass spectrometry (Py-GC-MS) and modelled by density functional theory (DFT).
Dalton Transactions 07/2010; 39(26):6080-91. · 3.84 Impact Factor
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ABSTRACT: Nanoparticles of Au, Ag, CdS, and CdSe have been linked together by a chemical reaction to form controlled assemblies of similar or different types of nanoparticles through amido or azo linkage. The capping of nanoparticles was exchanged with bifunctional groups containing active functional groups at the tails. The reaction between the tails of the capping agents resulted in the formation of amido or azo linkages. These reactions were carried out under very dilute conditions to control the assembly and avoid the polymerization. The assemblies formed included the dimers, trimers, tetramers, and hexa- or heptamers. These reactions are the first examples for the systematic approach to establish the chemical route for the controlled assembly of nanoparticles and open the way for the fabrication of nanoparticle based devices for various application.
Journal of the American Chemical Society 02/2010; 132(6):1780-1. · 9.91 Impact Factor
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ABSTRACT: A series of new metal complexes of thiobiurets and dithiobiurets have been synthesized and characterized. The compounds are potentially useful as novel single source precursors for the deposition of metal sulfide thin films or nanoparticles.
Dalton Transactions 02/2010; 39(6):1460-3. · 3.84 Impact Factor
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Inorganica Chimica Acta,. 01/2010;
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Appl. Organometal. Chem.,. 01/2010; 24:720.
