Electrochemistry and photophysicochemical studies of titanium, tantalum and vanadium phthalocyanines in the presence of nanomaterials

Chauke, Vongani Portia (2012) Electrochemistry and photophysicochemical studies of titanium, tantalum and vanadium phthalocyanines in the presence of nanomaterials. PhD thesis, Rhodes University.

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Abstract

The syntheses of tetra- and octa-substituted phthalocyanine complexes of titanium (IV) oxide vanadium (IV) oxide and tantalum (V) hydroxide and their electrochemical characterisation are presented in this work. The structures and purity of these complexes were confirmed by NMR,infrared and mass spectroscopies and elemental analysis. They show good solubility in most common solvents especially non-viscous solvents such as dichloromethane and chloroform. The cyclic voltammograms (CV) showed reversible to quasi reversible behavior for all the reduction couples and the oxidation peaks were irreversible. Spectroelectrochemistry of the complexes confirmed metal and ring redox processes for TaPc and TiPc derivatives and ring based processes only for VPc complexes. The synthesis of gold nanoparticles and their conjugation with the new phthalocyanines was carried out. Similarly, single walled carbon nanotubes were conjugated to selected tantalum complexes and the characterization of all the nanomaterials and their conjugates using different techniques that include TEM, XRD and AFM is also presented in this work. The photophysical and photochemical properties and photocatalytic oxidation of cyclohexene properties of the newly synthesised in the presence of gold nanoparticles were investigated. The compounds were stable, well within the stability range for phthalocyanines. The singlet oxygen quantum yield values increased drastically in the presence of gold nanoparticles. The photocatalytic products obtained from the reaction were cyclohexene oxide, 2-cyclohexen-1-ol, 2-cyclohexene-1-one and 1,4-cyclohexanediol. The percentage conversion values, yields and selectivity values improved significantly in the presence of AuNPs. Singlet oxygen was determined to be the main agent involved in the photocatalytic oxidation of cyclohexene. The electrocatalytic oxidation of bisphenol A and p-nitrophenol was carried out using nickel tetraamino phthalocyanine and all the newly synthesised metallophthalocyanine in the presence of gold nanoparticles and single walled carbon nanotubes. The charge transfer behaviour of AuNPs was enhanced in the presence of TaPc, TiPc and VPc complexes. The presence of single walled carbon nanotubes further improved electron transfer and minimised electrode passivation.

Item Type:Thesis (PhD)
Uncontrolled Keywords:Phthalocyanines, Titanium, Tantalum, Vanadium, Electrochemistry, Spectroscopies, Elemental analysis, Nanomaterials
Subjects:Q Science > QD Chemistry > QD71 Analytical chemistry
T Technology > TA Engineering (General). Civil engineering (General)
T Technology > TP Chemical technology
Divisions:Faculty > Faculty of Science > Chemistry
Supervisors:Nyokong, Tebello
ID Code:2891
Deposited By: Philip Clarke
Deposited On:30 May 2012 06:27
Last Modified:30 May 2012 06:27
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