Synthesis and characterization of metal oxide thin films, metal sulfide and metal oxide polymer nanocomposites and studies of their application in water treatment
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Date
2017-08-10
Authors
Xaba, Thokozani
Journal Title
Journal ISSN
Volume Title
Publisher
Vaal University of Technology
Abstract
The study based on thiourea derivatives has received significant interest from several
disciplines due to their variable bonding modes, promising biological implications and
their complexation capacity. Thiosemicarbazones are a stimulating type of ligands that
reveals a diverse range of biological activities. They are effectual intermediates for the
production of pharmaceutical and bioactive materials which makes them very useful in
the field of medicinal chemistry. The FTIR spectral variations in the stretching
frequencies of C=N, C–N and C=S that appeared at 1663, 1327 and 726 cm-1,
respectively confirmed the formation of the ligand. The present study describes the
preparation of (Z)-2-(pyrrolidin-2-ylidene)thiourea ligand for the synthesis of ZnS, CdS
and Ag2S nanoparticles via homogeneous/chemical precipitation technique. The effect
of different capping agents such as starch, PVP, PEG, PVA, and the role of ammonium
hydroxide solution during the synthetic processes was investigated and distinguished.
The study based on the effect of capping molecule on the formation of nanoparticles
proved that the capping agent has a great influence on the formation of nanoparticles.
The FTIR spectra of the capped nanoparticles revealed the shift toward the higher
frequencies compared with the uncapped metal sulfide nanoparticles. The metal sulfide
nanoparticles also showed an increased in energy band gaps which were different from
the bulk materials.
The 2-hydroxy-1-naphthaldehyde is regarded as a low-cost ligand which has also been
widely used in biological synthesis to determine free amino acid groups. The metal
complexes of this ligand are easily prepared and can be used to synthesize metal oxide
nanomaterials at low cost which are environmentally friendly that can be expended in
bio-applications. The preparation of the Zn, Cd and Ag complexes based on the bis(2-
hydroxy-1-naphthaldehydate ligand through the reaction desired metal acetate are
reported and confirmed by FTIR spectroscopy, elemental analysis and
thermogravimetric analysis (TGA). There has been a great research significance for the
synthesis of metal oxide since such materials have high specific surface area and a high
fraction of surface atoms. The synthesis of ZnO, CdO and Ag2O nanoparticles through
thermal decomposition of the Zn(II), Cd(II) and Ag(I) complexes into trioctylphosphene
oxide (TOPO) and/or hexadecylamine (HDA) at different decomposition temperatures
is reported. The study proved that the combination of oleylamine as a solvent and TOPO
as a capping molecule produced controlled shaped and reasonably dispersed particles.
The XRD patterns of all the metal oxide nanoparticles synthesized with TOPO were
showing face-centred cubic structures.
These metal oxide based complexes were also used as single source precursors to
prepare metal oxide thin films at different annealing temperatures on the glass substrate
using different methods such as annealing, thermal decomposition, aerosol assisted
chemical vapour deposition (AACVD) methods. The optical absorption and size
distribution of the synthesized nanoparticles and thin films have been explored using
XRD, SEM, AFM, FTIR, PL and UV-Vis spectroscopy techniques. The results show that
the decomposition temperature has a huge effect on the formation of the nanomaterials.
The SEM images of the as synthesized nanoparticles revealed different shapes of the
particles as the decomposition temperature is increased. A change in X-ray diffraction
parttern was observed when the decomposition temperatures were increased. The
capped metal sulphides and metal oxide nanoparticles were then allowed to react with
polydadmac or chitosan to form the polymer nanocomposites. The optical absorption,
luminescence properties, size distribution and the bonds distribution of the polymer
nanocomposites were characterized with UV-Vis, PL and FTIR spectroscopy. The
structural and morphological properties have been studied by XRD, TEM and SEM. The
absorption analysis of the prepared nanocomposites revealed the properties of both
nanoparticles and polymers. Chitosan and polydadmac are biopolymers that have been
proven as the best adsorbents to remove the heavy metal ions from wastewater.In this
study, polydadmac and chitosan based metal sulphide and metal oxide
nanocopmposites were used as adsorbents for the removal of Fe(III) from the
wastewater. The batch experiments were conducted to achieve the optimum conditions.
The effect of pH, contact time, and initial metal ion concentration were also determined.
The pH = 8 was found to be the optimum pH for the removal of Fe(II) ions from the water
sample by utilizing pure chitosan and chitosan nanocomposites as adsorbents.
Description
Ph. D. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology.
Keywords
Metal oxide polymer, Nanocomposites, Water treatment, Metal sulfide nanoparticles