Papers by Author: Norbani Abdullah

Abstract: In this investigation, it was successfully shown that variation of heating media for infused substrates in precursor solution, affects the growth density and size of nanostructured ZnO rods. ZnO rods were prepared by precipitation on a template of cleaned p-type silicon wafer, sputter-coated with a thin layer of gold, infused in prepared precursor solution. The precursor solution consists of 0.01M zinc nitrate hexahydrate (Zn(NO3)2.6H2O) added with equal concentration of stabilizer hexamethylenetetramine, C6H12N4 (HMTA). The set-up was heated in water-bath or dry-oven at a constant low temperature of 80°C. Structural images of the prepared ZnO rods were captured using scanning electron microscope (SEM), its structural phase orientation was characterized by x-ray diffraction (XRD) and its optical property was analyzed from photoluminescence (PL) emission spectra.

Abstract: Low-temperature solution immersion growth of low-dimensional ZnO nanostructures on gold-seeded Si substrate has been demonstrated. pH environment of the precursor solution, Zn(NO3)2.6H2O (zinc nitrate hexahydrate) and C6H12N4 (HMTA) was found to have considerable effect to ZnO morphology and photoluminescence. Structural, morphological and photoluminescence (PL) properties of the samples were obtained from XRD, SEM and PL-Raman characterisation. A near neutral (pH = 6.8) and acidic (pH = 5) precursor solution aided a dense near-aligned ZnO nanorods growth with smallest rods diameter of 30 and 20 nm respectively. Whereas alkaline precursor solution (pH = 9) gave rise to flower-like structures of ZnO. Chemical equations for the reactions and the role of H+ and OH- ions role in affecting the XRD diffraction peaks and morphology, are suggested. Room temperature PL emission spectra of ZnO were collected after excitation at 325 nm. UV and visible emission distinctive of ZnO were formed and the rationale for significant shifts of the visible emission was also discussed.

Abstract: Copper(II) mixed-valence complex, [Cu(II)Cu(I)(R)3(RH)2L4].CH3COCH3 (R = C6H5COO; L = CH3COCH2C(OH)(CH3)2) (1), is a potential photovoltaic material with low bandgap It is formed as a black solid from a facile carbon-carbon bond-forming reaction involving [Cu2(C6H4COO)4(C2H5OH)2] (2) and CH3COCH3 under acidic condition. The complex was soluble in most common organic solvents, but insoluble in water. Its formula was deduced from FTIR, UV-vis, and 1H-NMR spectroscopies, TGA and GCMS. Its effective magnetic moment was 1.33 B.M. at 298 K, suggesting strong antiferromagnetic coupling between the two Cu centres. Cyclic voltammetry shows an anodic peak at +0.70 V and two cathodic peaks at +0.53 V and -1.0 V. The HOMO and LUMO energy levels are 4.9 eV and 3.7 eV respectively, and hence the bandgap energy is 1.2 eV.

Abstract: We report an optimisation of reaction conditions leading to successful growth of aligned ZnO nanorods by a simple aqueous immersion method. Si substrates were immersed in aqueous Zn2+ solution at various temperatures ranging between 50 - 90°C and at various immersion times. Degree of crystallisation, thermal decomposition, surface morphology and crystallite size were analysed by FT-IR, TGA, SEM and XRD. Seeded noble metals like gold, platinum and nickel on Si substrate were found to improve the vertical alignment of rods’ growth and reduce the diameter of ZnO nanorods.

Abstract: A wet chemical approach, originating from sol-gel preparation, was adopted with the intention to develop a low-temperature benign method of preparation. ZnO nanorods are successfully grown in an aqueous medium. The precursor, zinc nitrate hexahydrate (Zn(NO3)2.6H2O), is stabilized by hexamethylene tetraamine (HMTA). The effect of changing the molarity of HMTA to the structural orientation of ZnO nanorods is investigated. X-ray diffraction of the synthesized ZnO shows hexagonal zincite structure. The structural features of the nanocrystalline ZnO were studied by SEM. Structural features, surface morphology and differences in lattice orientation are seemingly influenced by varying the Zn2+: HMTA molar ratio. The formation of ZnO nanorods with blunt and sharp tips is found to be significantly affected by this ratio.