Electrocatalytic detection of drugs of abuse using onion-like carbon based electrocatalysts
| dc.contributor.author | Ehirim, Tobechukwu Justice | |
| dc.date.accessioned | 2024-01-26T07:44:58Z | |
| dc.date.available | 2024-01-26T07:44:58Z | |
| dc.date.issued | 2024 | |
| dc.description | A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Faculty of Science, School of Chemistry, University of the Witwatersrand, Johannesburg, 2023 | |
| dc.description.abstract | Substance abuse is a serious problem worldwide. Among abused substances, tramadol and alcohol are one of many. There is an urgent need to use electrochemical method for their detection since electrochemistry methods are simple, low-cost, high sensitivity and can easily be miniaturised. This PhD work reports the first investigation on the application of nanodiamond-derived onion-like carbons (OLC) and conductive carbon black (CB) as (i) electrocatalysts for the detection of tramadol, and (ii) as support materials for nano-sized palladium electrocatalysts (Pd/OLC, Pd/CB, Pd-CeO2/OLC) for the detection of ethanol. The catalysts were characterised with X-ray diffraction (XRD), Raman, Brunauer– Emmett–Teller (BET), Thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). For the detection of tramadol, OLC gave the best sensing performance compared to CB. Theoretical calculations (DFT simulations) predict that OLC is better because it allows for weaker interaction energy with tramadol (Ead = -26.656 eV) than CB (Ead = -40.174 eV). OLC-modified glassy carbon electrode (GCE-OLC) shows a wide linear calibration curve (55 – 392 M), high sensitivity (0.0315 A /M), low limit of detection (LoD) and quantification (LoQ) of 3.8 and 12.7 M, respectively. OLCmodified screen-printed electrode (SPE-OLC) successfully detected tramadol in real tramadol drug and human serum. The OLC-based electrochemical sensor promises to be useful for sensitive and accurate detection of tramadol in clinics, quality control and routine quantification of tramadol in pharmaceutical formulations. For the oxidation and detection of ethanol, Pd/CB, Pd/OLC and Pd-CeO2/OLC, were studied as catalysts. In comparison, adding ceria (CeO2) to Pd/OLC, the performance was enhanced significantly than in carbon-only support for palladium. GCE/PdCeO2/OLC shows the best electrocatalytic performance (i.e., high current density, fast electron transport, etc). DFT calculation, supported by XPS and HRTEM data, predict that this high activity may be related to CeO2 modulating the electronic properties of the catalyst. GCE/Pd-CeO2/OLC gave wide linear range for ethanol sensing (38.5 – 286 mM), excellent sensitivity (0.00024 mA mM-1 ) and LoD of ~ 8.7 mM. The GCE/Pd-CeO2/OLC shows excellent potential for application in real samples of commercial alcoholic beverages and human serum, with satisfactory recoveries (89 – 108 %). | |
| dc.description.librarian | TL (2024) | |
| dc.faculty | Faculty of Science | |
| dc.identifier.uri | https://hdl.handle.net/10539/37432 | |
| dc.language.iso | en | |
| dc.phd.title | PhD | |
| dc.school | Chemistry | |
| dc.subject | Substance abuse | |
| dc.subject | Electrochemical | |
| dc.subject | Nanodiamond-derived | |
| dc.title | Electrocatalytic detection of drugs of abuse using onion-like carbon based electrocatalysts | |
| dc.type | Thesis |