Synthesis and applications of novel coumarin-based chemosensors for the detection of metal ions using UV-visible spectroscopy
- Authors: Myburgh, Lisa
- Date: 2024-04
- Subjects: Biosensors , Molecular recognition , Chemical detectors
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64239 , vital:73668
- Description: Current methods for ion detection are expensive and require trained personnel to operate the instruments. This led to the desire for alternative techniques that are quicker, easier to operate, cheaper, and highly efficient. With this in mind, coumarinbased derivatives were designed and synthesised using Knoevenagel condensation. These compounds were designed to incorporate different functional groups at the 3- position. Compounds S1, S2, and S3 contained keto, ester, and carboxylic acid groups, respectively. The structures of these compounds were confirmed using NMR, FT-IR, and X-ray crystal structures. During UV-Vis analysis, these compounds displayed a maximum absorption band between λmax= 289 and 295 nm, attributed to the coumarin moiety. Furthermore, the absorption behaviour of S2 was analysed in different solvent systems. It was noted that when S2 was dissolved in toluene, a significant absorbance increase and a hypsochromic shift were observed. The chemosensing capabilities of S1, S2 and S3 were investigated using UV-Vis for metal cations in acetonitrile. S1 and S3 showed selectivities towards Fe²⁺ ions, with S2 being selective for Fe³⁺ ions in a 1:1 binding ratio. Reversibility studies were performed using EDTA and revealed that S1 and S3 were partially reversible, with S2 showing nonreversibility properties. Lastly, the binding modes of these compounds with metal ions were determined using molecular modelling studies. These calculations concluded that the complexation occurs via the two carbonyl moieties from the coumarin ring and the ester group and is stabilised by nitrate counterions and water molecules. To change the selectivity of S2 towards Hg2+ ions, thiocarbonyl analogues of this compound were synthesised using Lawessons reagent. The reagent replaced the carbonyl oxygen of the coumarin backbone and the ester moiety with sulphur to form their respective analogues, S5 and S6. A switch in the selectivity of S5 and S6 was noted when tested as potential chemosensors for metal ions. S5 showed a high affinity for Hg²⁺, whereas S6 strongly interacted with both Hg²⁺ and Cu²⁺ ions in a 1:1 binding ratio. The mode of interaction was confirmed to occur between the thiocarbonyl and ester carbonyl group for S5 and between the two thiocarbonyl functional groups in S6. The viability of these novel chemosensors for detecting metal ions was then further tested in water samples obtained from local dams with positive results. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Converged data and sensing over optical fiber networks
- Authors: Shumane, Vela
- Date: 2022-12
- Subjects: Optical fiber subscriber loops -- South Africa , Chemical detectors , Internet -- Technological innovations
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59968 , vital:62722
- Description: Internet connectivity, data and sensors have become increasingly important across all spheres of business and industry, especially in the mining sector. Recent years have seen deeper mining explorations as a result of the depletion of natural resources in shallow strata. Due to complex and unexpected geological conditions as well as significant ground stresses, deep stratum mining operations encounter a number of difficulties. It is essential that the mining industry be more innovative with their equipment and monitoring systems given the rise in expenses caused by energy consumption, concessions to surface integrity, worldwide freshwater shortage, as well as health and safety of miners. Any attempt to eliminate these mining consequences must start with early discovery. An effective plan to anticipate, prevent, or manage geohazards events must be in place because to these complex and unpredictably occurring geological circumstances. Due to their capacity to combine gigabits of data from remote locations within the mine to a centralized control centre, optical fiber offers a variety of distinctive advantages within the mining industry. In order to attain maximum productivity, modern and effective mining operations use enhanced control techniques and increasing mechanization. Additionally, optical fibers can be utilized in a mine to safely monitor seismic activity, methane, roof collapses, rock bursts, explosions, and dangerous underground mine settings. Multimode or multi-core fibers represent a particularly intriguing alternative for transmissions over small distances, especially for broad band local area networks like LANs, as they enable the use of affordable components. Due to the current state of these issues, there is a drive to create fiber optic communication links that can also function as distributed optical fiber sensors, where each point along the fiber can function as a continuous array of sensors. In this thesis, we suggested and experimentally demonstrated a converged solution for precise vibration sensing and high-speed data in mining applications. With wireless access for people and equipment inside cavities, the solution uses multimode fiber to link nearby mining cavities. To track vibrations and earth tremors causing rock falls, polarization-based vibration sensors over multimode fiber is used. With a modal dispersion penalty of just 1.6 dB, photonic data transmission across 100 m of multimode fiber is successfully accomplished. Successful 1.7 GHz wireless transmission across a distance of 1 m is demonstrated, and vibrations between 50 Hz and 1 kHz may be reliably detected to within 0.02 percent of the true value. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12