Sixberth Mlowe

Bis(piperidinedithiocarbamato)pyridinecadmium(II) as a single-source precursor for the synthesis of CdS nanoparticles and aerosol-assisted chemical vapour deposition (AACVD) of CdS thin films

The synthesis and single-crystal X-ray structure of bis(piperidinedithiocarbamato)pyridinecadmium(II), [Cd(S2C(NC5H10))2(NC5H5)] are reported and its use as a precursor for the synthesis of hexagonal CdS nanoparticles and CdS thin films is presented. Thermogravimetric analysis (TGA) of this complex showed clean decomposition in two steps to give CdS. Thermolysis of the complex in hexadecylamine at different temperatures in the range 190–270 °C gave CdS nanostructures including nanorods and oval shaped particles. The band gap of the as-synthesized CdS nanoparticles varied as the temperature was increased. CdS thin films with optical direct band gaps of ca. 2.4 eV were deposited by aerosol-assisted chemical vapour deposition (AACVD) in the temperature range 350 to 450 °C using the same precursor. Powder X-ray diffraction (p-XRD) patterns of CdS nanoparticles and thin films confirmed the hexagonal phase of CdS.

CdSe quantum dots capped with naturally occurring biobased oils

We report a green synthesis of CdSe quantum dots (QDs) using bio-based materials (castor oil and ricinoleic acid) as capping agents. The absorption spectra of the as-synthesized CdSe QDs showed typical features of quantum confinement. The particle sizes of QDs were determined using the absorption band edges and found to be 3.81 to 6.80 nm and 5.91 to 8.31 nm for the entire range of reaction temperatures for QD-capped with castor oil (CSTO) and ricinoleic acid (RA), respectively. The photoluminescence spectra showed narrow emission peaks. The transmission electron microscopy (TEM) images showed spherical particles with sizes comparable to those determined from the absorption spectra. Comparatively, large particles were observed for RA capped CdSe QDs than those stabilized by CSTO. X-ray diffraction patterns revealed that the synthesized CdSe quantum dots have cubic structure. The particle sizes of CdSe deduced from X-ray diffraction measurements were in excellent agreement with those deduced from absorption spectra and TEM images. The d-spacings from the HRTEM images were consistent with those reported in literature. The surface area and the agglomeration number for as-synthesized CdSe QDs of different sizes are also reported.

Evidence of oriented attachment in the growth of functionalized ZnTe nanoparticles for potential applications in bio-imaging

This study reports a solution based, low temperature route towards the synthesis of water soluble cysteine capped zinc telluride (ZnTe) nanoparticles under the influence of variations in pH and reaction time. The optical properties of the ZnTe nanoparticles display broad emission peaks ranging between 365–415 nm, which make them useful for imaging and biological labelling applications. Transmission electron microscopy (TEM) and high resolution TEM studies indicated that the particles are uniform in size and shape, however at the 2 hour reaction time interval the nanoparticle growth enters a transition phase where the morphology changes from nanospheres to nanorods. The formation of the ZnTe nanoparticles relative to reaction temperature, pH and time is typical of the oriented attachment growth mechanism. X-ray diffraction patterns confirmed the crystalline cubic phase. The surface charge of the functionalised ZnTe was also determined. The fluorescence properties and optical stability of the ZnTe nanoparticles in DNA plasmid pGEMT Easy were studied using fluorescence (365–395 nm filter) and phase-contrast (UV 2A 330–380 nm filter) microscopy techniques.

Phase pure Ni3S2 and NiS from bis(N′-ethyl-N-piperazinylcarbodithioato-S,S′)–nickel(II) via solvent thermolysis and aerosol assisted chemical vapour deposition

A bis(N′-ethyl-N-piperazinylcarbodithioato-S,S′)–nickel(II) complex was prepared and characterized using infrared spectroscopy, thermogravimetric and elemental analyses. The crystal X-ray structure for bis(N′-ethyl-N-piperazinylcarbodithioato-S,S′)–nickel(II) was determined. The complex was subsequently used as a single source precursor (SSP) for the synthesis of phase pure Ni3S2 and NiS nanoparticles and thin films via hot injection thermolysis and aerosol assisted chemical vapour deposition (AACVD) routes, respectively. For the hot injection thermolysis route, hexadecylamine (HDA) and oleylamine (OLA) were used as capping groups at varying temperatures. Chloroform was used as the solvent in the AACVD experiments. Powder X-ray revealed that the capping group does not change the phase of nanoparticles formed whereas the AACVD technique produced different phases. Variation of temperature did not affect the phase purity of the nanomaterials formed. The morphology of the thin films obtained via AACVD depended largely on the deposition temperature, whereas for the nanoparticles, temperature and the capping group had a significant impact.