Department Of Chemistry

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Browsing Department Of Chemistry by Author "Abdulwahab, K.O."

Now showing 1 - 7 of 7
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    Open Access
    A direct synthesis of water soluble monodisperse cobalt and manganese ferrite nanoparticles from iron based pivalate clusters by the hot injection thermolysis method
    (ELSIVIER, 2014) Abdulwahab, K.O.; Malik, M.A.; O'Brien, P.; Timco, G.A.
    Highly monodisperse water soluble cobalt ferrite (CoFe2O4) and manganese ferrite (MnFe2O4) nanoparticles were synthesised by the hot injection thermolysis of pivalate clusters as single source precursors. The precursors [Fe2CoO(O2CtBu) 6(HO2CtBu)3] (1) and [Fe2MnO(O2CtBu)6 (HO2CtBu)3] (2) were decomposed in a mixture of polyvinyl pyrrolidone (PVP) (capping agent)and triethyleneglycol (TREG) (solvent) at 285 1C to produce cobalt ferrite and manganese ferrite nanoparticles, respectively. The effect of the PVP on the size and morphology of the nanoparticles synthesised was investigated. Smaller sized nanoparticles of cobalt and manganese ferrite nanoparticles were obtained at higher PVP concentration and larger nanoparticles were produced at lower PVP concentrations. The ferrite nanoparticles produced are monodisperse, directly dispersible in water without any further sizes election/post synthesis procedure.The nanoparticles were characterised by powder X-ray diffraction (p-XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS) and selected area electron diffraction (SAED).
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    Open Access
    The effect of alkyl chain length on the structure of lead(II) xanthates and their decomposition to PbS in melt reactions
    (The Royal Society of Chemistry/Dalton Transactions, 2016) McNaughter, P.D.; Saah, S.A.; Akhtar, M.; Abdulwahab, K.O.; Malik, M.A.; Raftery, J.; Awudza, J.A.; O’Brien, P.
    A series of lead(II) alkylxanthates, [Pb(S2COR)2] (R = ethyl (1), n-propyl (2), n-butyl (3), n-hexyl (4) or n-octyl (5)) have been prepared and explored as single source precursors for use in melt reactions to form lead sulfide. X-ray single crystal structures of (2), (3) and (4) were used along with previously reported structures to investigate the influence of structure and chain length on the materials produced. The complexes were decomposed at 150, 175 or 200 °C forming PbS nanocrystals as confirmed by XRD and TEM. Analysis by SEM shows that the choice of precursor had an influence on nanocrystal size with longer alkyl chains resulting in smaller cubic nanocrystals. In addition to cubes, anisotropic growth was observed from decomposition of compound.
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    Open Access
    Hot injection thermolysis of heterometallic pivalate clusters for the synthesis of monodisperse zinc and nickel ferrite nanoparticles
    (The Royal Society of Chemistry, 2014) Abdulwahab, K.O.; Malik, M.A.; O'Brien, P.; Timco, G.A.; Tuna, F.; Winpenny, R.E.; Pattrick, R.A.; Coker, V.S.; Arenholz, E.
    The heterometallic pivalate clusters- [Zn4Fe2O2(O2CtBu)10] (1) and [Fe2NiO(O2CtBu)6(HO2CtBu)3] (2) have been used as single source precursors to synthesise monodispersed zinc ferrite (ZnFe2O4) and nickel ferrite (NiFe2O4) nanoparticles respectively. The precursors were thermolysed with a mixture of oleylamine and oleic acid in either diphenyl ether or benzyl ether as the solvent at their respective boiling points of 260 and 300 C. The effect of reaction time, temperature and concentration (0.25 or 0.50 mmol) on the stoichiometry, the phase or morphology of the nanoparticles were studied. TEM showed that highly monodispersed spherical nanoparticles of zinc ferrite (3.2 0.2 nm) and nickel ferrite (3.3 0.2 nm) respectively were obtained from (1) and (2) using 0.50 mmol precursor concentration at 260 C. The decomposition of the precursors at 0.25 mmol and 300 C gave larger nanoparticles of zinc ferrite (5.6 0.5 nm) and nickel ferrite (5 0.6 nm) from (1) and (2) respectively. The effect of reaction time was investigated for both precursors at 0.25 mmol by withdrawing aliquots at 5 minutes, 15 minutes, 30 minutes, 1 hour and 2 hours. Aliquots withdrawn at reaction times of less than 1 hour contain traces of iron oxide whilst only pure cubic zinc or nickel ferrite was obtained after one hour. Magnetic measurements revealed that all the ferrite particles are superparamagnetic at room temperature with high saturation magnetisation values. XMCD confirmed that in nickel ferrite particles, most of the Ni2+ cations are in the octahedral site. The hysteresis loop observed on the zinc ferrite nanoparticles indicated that there is cation redistribution, this is further evident in the XMCD analysis and EPMA result.
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    Open Access
    A One-Pot Synthesis of Monodispersed Iron Cobalt Oxide and Iron Manganese Oxide Nanoparticles from Bimetallic Pivalate Clusters
    (American Chemical Society, 2013-11-06) Abdulwahab, K.O.; Malik, M.A.; O'Brien, P.; Timco, G.A.; Tuna, F.; Muryn, C.A.; Winpenny, R.E.; Pattrick, R.A.; Coker, V.S.; Arenholz, E.
    Monodispersed iron cobalt oxide (Fe2CoO4) and iron manganese oxide (Mn0.43Fe2.57O4) nanoparticles have been synthesized using bimetallic pivalate clusters of [Fe2CoO-(O2CtBu)6(HO2CtBu)3] (1), Co4Fe2O2(O2CtBu)10(MeCN)2] (2), and [Fe2MnO(O2CtBu)6(HO2CtBu)3] (3) respectively as single source precursors. The precursors were thermolyzed in a mixture of oleylamine and oleic acid with either diphenyl ether or benzyl ether as solvent at their respective boiling points of 260 or 300 °C. The effect of reaction time, temperature and precursor concentration (0.25 or 0.50 mmol) on the stoichiometry, phases or morphology of the nanoparticles were studied. TEM showed that highly monodispersed spherical nanoparticles of Fe2CoO4 (3.6 ± 0.2 nm) and Mn0.43Fe2.57O4 (3.5 ± 0.2 nm) were obtained from 0.50 mmol of 1 or 3, respectively at 260 °C. The decomposition of the precursors at 0.25 mmol and 300 °C revealed that larger iron cobalt oxide or iron manganese oxide nanoparticles were obtained from 1 and 3, respectively, whereas the opposite was observed for iron cobalt oxide from 2 as smaller nanoparticles appeared. The reaction time was investigated for the three precursors at 0.25 mmol by withdrawing aliquots at 5 min, 15 min, 30 min, 1 h, and 2 h. The results obtained showed that aliquots withdrawn at reaction times of less than 1 h contain traces of iron oxide, whereas only pure cubic iron cobalt oxide or iron manganese oxide was obtained after 1 h. Magnetic measurements revealed that all the nanoparticles are superparamagnetic at room temperature with high saturation magnetization values. XMCD confirmed that in iron cobalt oxide nanoparticles, most of the Co2+ cations are in the octahedral site. There is also evidence in the magnetic measurements for considerable hysteresis (>1T) observed at 5 K. EPMA analysis and ICP-OES measurements performed on iron cobalt oxide nanoparticles obtained from [Fe2CoO(O2CtBu)6(HO2CtBu)3] (1) revealed that stoichiometric Fe2CoO4 was obtained only for 0.50 mmol precursor concentration. All the nanoparticles were characterized by powder X-ray diffraction (p-XRD), transmission electron microscopy (TEM), inductively coupled plasma-optical emission spectroscopy (ICP-OES), electron probe microanalysis (EPMA), X-ray magnetic circular dichroism (XMCD), and superconducting quantum interference device (SQUID) magnetometry.
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    Open Access
    The synthesis of a monodisperse quaternary ferrite (FeCoCrO4) from the hot injection thermolysis of the single source precursor [CrCoFeO (O2CtBu)6(HO2CtBu)3]
    (The Royal Society of Chemistry, 2018) Abdulwahab, K.O.; Malik, M.A.; O'Brien, P.; Vitorica-Yrezabal, I.J.; Timco, G.A.; Tuna, F.; Winpenny, R.E.
    Monodisperse cobalt chromium ferrite (FeCoCrO4) nanoparticles have been synthesised using the trimetallic pivalate cluster [CrCoFeO(O2CtBu)6(HO2CtBu)3]. The precursor was thermolysed in oleylamine and oleic acid, with diphenyl ether as the solvent at 260 °C. The effect of time and the concentration of the precursor on the stoichiometry of the phase formed and/or the morphology of the nanoparticles was studied. The reaction time was investigated by withdrawing aliquots at different times. No products were formed after 5 minutes and aliquots withdrawn at reaction times of less than 1 hour contain traces of iron oxide (Fe2O3); only cubic cobalt chromium ferrite (FeCoCrO4) was obtained after one hour. Transmission Electron Microscopy (TEM) showed that more monodisperse spherical ferrite nanoparticles (4.0 ± 0.4 nm) were obtained at higher precursor concentrations. Magnetic measurements revealed that all the ferrite particles are superparamagnetic at room temperature but showed large hysteresis at low temperature. The nanoparticles were characterised by Powder X-Ray Diffraction (p-XRD) and Transmission Electron Microscopy (TEM). A Superconducting Quantum Interference Device (SQUID) was used to analyse the magnetic properties of the nanoparticles.
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    Open Access
    Synthesis of monodispersed magnetite nanoparticles from iron pivalate clusters
    (The Royal Society of Chemistry/Dalton Transactions, 2013) Abdulwahab, K.O.; Malik, M.A.; O'Brien, P.; Govender, K.; Muryn, C.A.; Timco, G.A.; Tuna, F.; Winpenny, R.E.
    The iron pivalate clusters [Fe3O(O2CtBu)6(H2O)3](O2CtBu)·HO2CtBu (1), [Fe8(OH)4(O2CtBu)12(OC6H4C6H5)8] (2) and [Fe3O(O2CtBu)6(C5H5N)3] (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 (1) 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 (Fe2O3) and magnetite (Fe3O4) 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 [Fe3O(O2CtBu)6(H2O)3](O2CtBu)·HO2CtBu (1) 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.
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    Open Access
    WATER-DISPERSIBLE MAGNETITE NANOPARTICLES OBTAINED BY CO-PRECIPITATION AND THERMAL DECOMPOSITION METHODS.
    (UNIVERSITY OF LAGOS, 2014) Abdulwahab, K.O.; Malik, M.A.; O'Brien, P.
    Water-dispersible magnetite (Fe3O4) nanoparticles were synthesised by the co-precipitation of iron salts (dual-source) and the hot injection thermolysis of iron pivalate complex (single source). The iron pivalate complex was thermolysed in a mixture of polyvinylpyrrolidone (PVP) as capping agent and triethylene glycol (TREG) as solvent at the boiling point of the solvent (285 °C). The co-precipitation method involved precipitating iron(II) and iron(III) salts with ammonium hydroxide at room temperature. This was then followed by the addition of polyallylamine hydrochloride (PAH). The p-XRD patterns obtained for the nanoparticles revealed that magnetite was synthesised by both methods. TEM showed that the magnetite nanoparticles obtained from the thermal decomposition method are more monodispersed (4.1 ± 0.3 nm) than those obtained from co-precipitation method (7.0 ± 1.0 nm). The nanoparticles were characterised by powder X-ray diffraction (p-XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED).