Sifiso Albert Nsibande
Doctor of Philosophy

Supervisor:
Prof Patricia Forbes

Development of quantum dot fluorescence sensors for detection of targeted pesticides and polycyclic aromatic hydrocarbons 

Pesticides and polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants that continue to be of great concern due to their potential toxic and human health effects. Human activities play a significant role in the release of these compounds into the environment. The occurrence of these pollutants in low concentration and the need for their continuous monitoring presents a challenge for the environmental analytical chemist. Sensitive analytical techniques that can selectively detect these compounds without being affected by the environmental matrix are required. Advances in nanotechnology have allowed for the design of sensitive and selective nanomaterials which provide alternative analytical tools for such challenges.

In this work, therefore, extensive reviews on the current application of quantum dots (QDs) and nanoparticles in designing probes for detection of pesticides and PAHs were conducted. Through these reviews, the current status on the application of QDs sensors for these compounds was assessed. Knowledge gaps were identified where it was noted that there were no QD-based sensors for atrazine and GQD sensors for PAHs. The reviews further assessed the advantages and challenges for coupling QDs to various analyte receptors to enhance selectivity and how these impact on the scaling of such sensors for routine applications.

View full abstract here.

Kayode Adesina Adegoke
Doctor of Philosophy

Supervisor:
Prof Emil Roduner

In his thesis entitled, Electrochemical reduction of carbon dioxide to liquid fuels: Conversion of a thermal catalyst to an electrocatalyst, he overcame the previous view that formic acid is a dead end of the electrochemical conversion of carbon dioxide to hydrocarbons or alcohols containing more than one carbon atom. In the co-electrolysis of water and formic acid, indium oxide with a small amount of added polytetrafluoroethylene is an efficient electrocatalyst for the conversion to alcohols. This results in a mixture of methanol, ethanol and iso-propanol with a maximum combined Faraday efficiency of 82.5%, a current density of 70 mA/cm² and a space-time-yield that compares well with results from heterogeneous indium oxide catalysis. Reduction works more efficiently with dissolved carbon dioxide than with formic acid, primarily via a competing pathway that bypasses formic acid as an intermediate. Chronoamperometric experiments showed the build-up of a diffusion-gradient that impedes the reaction in the unstirred reactor. This offers ways for further improvement of the experimental setup towards a process of industrial interest.

Rasheed Adewale Adigun
Doctor of Philosophy

Supervisor:
Dr Natasha October

Synthesis and structure-activity relationships of resistance reversal dihydropyrimidinone-based antimalarials
Recent data indicates that the challenge to overcome malaria still continues, regardless of the all the significant efforts and advances in drug and medical technologies. The rise of drug resistance, particularly in the virulent parasitic plasmodia strains in many malarial prone regions is the principal contributor to this trend. Even a greater cause of concern is the growing resistance to current anti-malarials like artemisinin-based compounds, which lacks CQ’s simplicity and low cost, threatens to derail all attempts to control this disease. The on-going task that researchers are faced with is to design new strategies and technologies to develop novel drugs which may fair better than the existing antimalarial drugs or improve their efficacy.

View detailed abstract here.

Mathibela Elias Aphane
Doctor of Philosophy

Supervisor:
Prof Liezel van der Merwe

Silica nanoparticles from South African coal fly ash derived sodium silicate solutions

This study successfully demonstrated the synthesis of amorphous mesoporous silica nanoparticles from sodium silicate solutions, which were prepared from South African coal fly ash. It further validated the suitability of the silica nanoparticles as catalyst support in heterogeneous catalysis and proved that these products could be successfully employed as alternative to commercially available mesoporous silica. The research proposes the transformation of a by-product from coal-fired power stations into novel products of technical and commercial value and contributes significantly to the development of new practices for the utilisation of South African coal fly ash.

You can view the full abstract here.

Lebogang Malemela
MSc Thesis

Supervisor:
Dr Nolwazi Nombona

Two-dimensional semiconductor transition metal dichalcogenide nanosheets as charge carriers in metallophthalocyanine based solar cells

In this work we explore the use of molybdenum sulfide (MoS₂) and tungsten (WS₂) TMDs as electron transporting layers for solar cell application. The TMDs were successfully synthesised using the chemical exfoliation method and they were further doped with gold (Au) in order to enhance charge carrier mobility. The doped and undoped TMDs were characterised using X-ray diffraction (XRD), Raman spectroscopy, energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM).  In our study we show the photovoltaic properties of TMDs combined with a variety of MPc’s. The utilisation of these TMDs with MPc’s has led to the generation of cost-effective solar cells that can be exploited for future technological applications.

View full abstract here.