Platinum nanoparticles supported on carbon nanodots as anode catalysts for direct alcohol fuel cells
- Authors: Gwebu, Sandile Surprise , Nomngongo, Philiswa Nosizo , Mashazi, Philani Nkosinathi , Maxakato, Nobanathi Wendy , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233118 , vital:50058 , xlink:href="https://doi.org/10.20964/2017.07.09"
- Description: Carbon nanodots (CNDs) were successfully synthesized employing a cheap and green method using oats as a starting material. The Pt/CNDs electrocatalyst was synthesized using carbon nanodots as a reductant and support material without adjusting the pH of the solution. The synthesized materials were characterized using Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller Nitrogen adsorption (BET), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Inductively coupled plasma optical emission spectroscopy (ICP-OES). The FTIR results proved that the synthesized carbon nanodots contain carboxylic acid functional groups which facilitate the attachment of Pt nanoparticles. The BET surface area for carbon nanodots was found to be 312.5 m2 g -1 two times higher than that of commercial carbon. XPS results revealed the composition of the materials and the oxidation states of Pt in Pt/CNDs electrocatalyst. TEM images proved that the materials were of the nanoscale. XRD peaks proved that the carbon nanodots were amorphous and Pt (111) was present in the Pt/CNDs electrocatalyst. ICPOES determined the platinum concentration in Pt/CNDs electrocatalyst to be 8.12%. The electrochemical oxidation of methanol and ethanol were studied by cyclic voltammetry (CV) and chronoamperometry (CA). Cyclic voltammetry results showed that the Pt/CNDs electrocatalyst prepared by this method exhibit superior performance for methanol and ethanol electro-oxidation at room temperature.
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- Date Issued: 2017
Electrochemical sensing and immunosensing using metallophthalocyanines and biomolecular modified surfaces
- Authors: Mashazi, Philani Nkosinathi
- Date: 2012
- Subjects: Phthalocyanines , Electrochemistry , Electrodes, Enzyme , Measles -- Measurement
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5580 , http://hdl.handle.net/10962/d1018248
- Description: The synthesis of cobalt and manganese phthalocyanine complexes bearing eight hexylthio and four amino substituents was carried out. The formation of thin films of these complexes using different modification methods was also studied. Hexylthio functionalized metallophthalocyanine complexes were immobilized onto gold electrode surfaces using the self-assembly techniques. Surface modifications using cobalt and manganese tetraamino phthalocyanine as polymers, monolayers (onto electrografted surfaces) and as carbon nanotube – metallophthalocyanine conjugates was also carried out. The new method of modifying gold electrodes with metal tetraamino phthalocyanine complexes was investigated. The modified electrode surfaces were studied for their electrocatalytic properties and as potential electrochemical sensors for the detection of hydrogen peroxide (H₂O₂). The limits of detection for the H₂O₂ were of the orders of ~10⁻⁷ M for all the modified electrodes. The modified electrodes gave very good analytical parameters; such as good sensitivity, linearity at studied concentration range and well-defined analytical peaks with increased current densities. The modification methods were reproducible, highly conducting thin films were formed and the modified electrodes were very stable. The design of electrochemical immunosensors for the detection of measles-specific antibodies was also carried out. The modified surface with measles-antigen as sensing element was accomplished using covalent immobilization for an intimate connection of the measles-antigen as a sensing layer onto an electrode surface. Two methods of detecting measles-specific antibodies were investigated and these methods were based on electrochemical impedance, i.e. label-free detection, and voltammetric method using horse-radish peroxidase (HRP) labeled antibody as a reporter. The detection of measles-specific antibodies was accomplished using both these methods. The potential applications of the designed immunosensor were evaluated in real samples (human and newborn calf serum) and the electrodes could detect the antibodies in the complex sample matrix with ease.
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- Date Issued: 2012
Study of metallophthalocyanines attached onto pre-modified gold surfaces
- Authors: Mashazi, Philani Nkosinathi
- Date: 2007
- Subjects: Phthalocyanines , Electrochemistry , Electrodes, Enzyme , Glucose -- Measurement
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4361 , http://hdl.handle.net/10962/d1005026 , Phthalocyanines , Electrochemistry , Electrodes, Enzyme , Glucose -- Measurement
- Description: Tetra-carboxy acid chloride phthalocyanine complexes of cobalt, iron and manganese were synthesized and characterized using spectroscopic and electrochemical techniques. These complexes were fabricated as thin films on gold electrode following a covalent immobilization and self-assembling methods. Surface electrochemical and spectroscopic characterization showed that these complexes are surface-confined species. The characterization using spectroscopic and electrochemical methods confirmed the formation of thiol and MPc SAMs on gold electrode. The electrocatalytic behaviour of the SAM modified gold electrodes was studied for the detection of L-cysteine and hydrogen peroxide. The limits of detection (LoD) for Lcysteine were of the orders of 10[superscript -7] mol.L[superscript -1] for all the MPc complexes studied and the LoD for hydrogen peroxide at cobalt phthalocyanine modified gold electrode was of the orders of 10[superscript -7]mol.L[superscript -1] for both electrocatalytic oxidation and reduction. The modification process for gold electrodes was reproducible and showed good stability, if stored in pH 4 phosphate buffer solutions and can be used over a long period of time. The cobalt phthalocyanine modified gold electrode was also investigated for the fabrication of glucose oxidase (GOx)-based biosensor and as an electron mediator between the enzyme and gold electrode. The behaviour of the enzyme modified gold electrode towards the detection of glucose was studied and the results gave a limit of detection of the orders of 10[superscript -6] mol.L[superscript -1] with low binding constant (4.8 mM) of enzyme (GOx) to substrate (glucose) referred to as Michaelis-Menten constant. The practical applications, i.e. the real sample analysis and interference studies, for the enzyme modified gold electrodes were investigated. These studies showed that the enzyme electrode is valuable and can be used for glucose detection.
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- Date Issued: 2007