Thesis submitted 23-03-2012.pdf - University of Limpopo ...

and spherical in shape with an average size of 34 – 58 nm with the mean
particle diameter of 42.41 nm ± 12.03 nm and standard deviation of (σ)
0.27 nm indicating broad size distribution for the superparamagnetic iron
oxide nanoparticles (SPION), the particle diameters for the gold coated
SPION are in the range 34-54 nm while the average particle size as
determined from the TEM image for the selected fraction is 44.26 nm
6.93 nm. The relative standard deviation of the sizes of the nanoparticles
is 0.16 nm and the TEM for the functionalized gold coated SPION shows
monodispersed particles which appear in spherical, cubic, irregular
hexagon and oblong shapes with an average diameter of 44.65 nm. The
HRTEM image, shows the existence of lattice planes which confirms the
crystallinity of the material. The spacing between adjacent lattice planes is
about 0.23 nm which corresponds to the (311) interplanar distance of
Fe3O4 nanocrystals. Atomic force microscopy (ATM) was used to confirm
the transmission electron microscopy (TEM) and HRTEM findings.
The UV-Visible absorption spectra of the deionised water used in the
procedure of preparation of the as-synthesized nanoparticles showed no
absorption peak in a wavelength range of 350-750 nm, but after
introducing the suspension of the Au-coated magnetic nanoparticles, an
absorption peak located at 526 nm appeared which is ascribed to the
surface plasmon of nanosized Fe3O4@Au nanoparticles.
The kinetic studies using UV-visible spectrometer and the HRTEM images
confirmed the adsorption of the porphyrin macromolecules as a coat on the
magnetites particles. At a 5000 revolution per second (rps), aliquot sample
of the aqueous phase of the suspension of 0.002 mM Fe3O4@Au in
contact with the organic phase solution of the porphyrin taken for
absorbance measurement at every 600 s showed a decrease in the
concentration of the suspension while a noticeable and appreciable
increase was also noted in the concentration of the porphyrin
macromolecules measured at a λ max of 420 nm representing the
iii