Immaculate N. Michira

Synthesis and Characterization of Sulfonated Polyanilines and Application in Construction of a Diazinon Biosensor

A series of sulfonated polyaniline/derivatized polyaniline nanocomposites was chemically synthesized in the presence of anthracene and naphthalene sulfonic acids. UV-vis and FTIR results indicated the emergence of new bands at 420 and 700 nm and 1100 cm−1 in their spectra, respectively, meaning the dopant/polymer intercalations involved electronic interactions between dopant/polymer sub-lattices. The electroactive composites displayed moderately fast electrode kinetics. A composite-based biosensor for hydrogen peroxide reached a steady state current of 9.2 and 5.3 µA, and when fine-tuned for diazinon detection gave % inhibitions to be 41 and 81% for the polyaniline and poly-o-methoxyaniline biosensors, respectively.

Synthesis and Characterization of Green Tea Stabilized Iron Nanocatalysts for Brymothymol Blue (BTB) Degradation

Iron nanoparticles (FeNPs) were prepared from the green tea extracts at different temperatures through green synthesis procedure and characterized by various physicochemical techniques like UV-Visible spectroscopy, FTIR Spectroscopy, energy dispersive X-ray spectrometry (EDS), X-ray diffraction and high resolution tunneling microscopy (HRTEM) and the results confirmed the synthesis of polydisperse and stable FeNPs by the tea extracts. The catalytic activity of FeNPs was investigated using a common environmental pollutant BTB often used in textile industries for dyeing purposes. In these tests, catalytic degradation of BTB with FeNPs at a 10 μL or 30 μL concentration was done in the presence of 2% hydrogen peroxide. Results show no BTB degradation in the absence of the FeNPs. However, a 38% and 68% degradation of BTB was realized in the presence of 10μL and 30 μL FeNPs respectively indicating that the iron nanocatalysts were responsible for the dye degradation. The BTB degradation kinetics was found to follow pseudo-first order kinetics with rate constants at the two catalyst concentrations being 0.023 min-1 and 0.063 min-1 respectively.

Polydisperse low Diameter ‘Non-toxic’ Silver Nanoparticles Encapsulated by Rooibos Tea Templates

This work reports the synthesis of ‘non-toxic’ polydisperse, low diameter silver nanoparticles (AgNPs). Rooibos extracts at temperatures 25 °C, 30 °C, 50 °C, 70 °C and 90 °C were used. The effect of different extraction temperature on the % yield and nature of the AgNPs were investigated. The characteristics of the ‘green synthesis’ processed AgNPs were evaluated through UV-Vis spectroscopy, high resolution tunnelling microscopy (HRTEM), X-ray diffraction (XRD) and EDX techniques. Results indicated an increase in extraction temperature leads to more polyphenol extraction, increase in the AgNP % yield and greater absorbance. A yellow to brown to dark brown colour change observed during the synthesis indicated AgNPs formation. UV-Vis results indicated the AgNPs surface plasmon peaks at 440, 447, 450, 460 and 489 nm for the 25 °C, 30 °C, 50 °C, 70 °C, 90 °C respectively. SEM results revealed spherical nanosized particles with dense cores and lighter outer region with mean diameters for AgNPs ranged between 4.4-5.8 nm. EDX results indicated prominent Ag peaks at 3.10 keV. XRD results showed vaguely defined amorphous polyol peaks at below 2θ = 27°. The sharp peaks at 2θ = 38°, 45°, 66° and 77° which were assigned as 111, 200, 220 and 321 corresponded to the face-centred cubic crystalline silver phase.