Synthesis and applications of hydroxyl-functionalized chemosensors for selective detection of ions in aqueous systems
- Authors: Hamukoshi, Simeon Shiweda
- Date: 2024-04
- Subjects: Molecular recognition , Solution (Chemistry) , Water chemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63787 , vital:73613
- Description: Fluorescent molecular chemosensors are crucial tools for monitoring toxic metal ions and environmental compounds that pose risks to both humans and wildlife. Continuous sensing is essential for early detection, and chemosensors offer a sensitive and straightforward approach by detecting challenging analyte’s through optical absorption and fluorescence. Current detection methods, such as flame photometry and mass spectrometry, can be expensive, destructive, and impractical for continuous monitoring. Consequently, fluorescent-based methods present a promising, simple, and highly sensitive alternative for chemical recognition and monitoring. In this project, we successfully synthesized ten highly selective small hydroxyl containing molecule fluorescent and colorimetric sensors; Oxime Dye (OD), Small Sensor 1 (SS1), Small Sensor 2 (SS2), Quinoline Dye 1 (QD1), Quinoline Dye 2 (QD2), Quinoline Dye 3 (QD3), Coumarin Dye 1 (CD1), Coumarin Dye 2 (CD2), Naphthalene Dye 1 (ND1), Naphthalene Dye 2 (ND2). These chemosensors contained benzothiazole, naphthalene, quinoline, and coumarin fluorophores. These sensors facilitate both quantitative and qualitative assessment of cationic and anionic species in aqueous organic media. The chemosensors were synthesized using modified Schiff base, azo dye, and oxime-based reactions, enhancing binding and selectivity with analyte’s. They exhibited selectivity towards various metal ions (Cu2+, Fe2+, Ni2+, and Hg2+) and anions (hydroxyl and cyanate), characterized by distinct absorption bands and significant fluorescent quenching and enhancement. While some sensors were selective towards both cations and anions, others exclusively targeted cations, showing lower selectivity or sensitivity towards anions upon further testing. Conversely, certain sensors were selective towards anions, demonstrating reduced sensitivity or selectivity towards the tested cations. The oxime-based chemosensor, OD, was obtained through an oxime-based reaction. The sensor demonstrates remarkable selectivity for Cu2+ and cyanate ions. During titration experiments, the interaction of Cu2+ with OD resulted in a noticeable fluorescence quenching effect, while the presence of OCN ions led to fluorescence enhancement. These distinct behaviors strongly suggest the formation of specific 1:1 complexes between OD and Cu2+ or OCN ions, a conclusion supported by detailed analysis using the Jobs plot technique. In addition to the fluorescence studies, investigations into the influence of pH on the sensor OD, as well as its complexes with Cu2+ and OCN, were conducted to determine the optimum pH conditions for their operation. Moreover, reversible behavior of the complexes was explored in the presence of EDTA, revealing that only the OD-OCN complex displayed reversibility. Furthermore, molecular modeling studies were performed to validate the binding units and calculate the energy differences between the sensor and its respective complexes. Additionally, four chemosensors (SS1, SS2, CD2, and QD2) were synthesized and characterized using Schiff-based reactions, showcasing their unique absorption behaviors. SS1 and SS2, characterized by benzothiazole fluorophores, demonstrated high sensitivity to hydroxyl anions. Jobs plot studies revealed a stable 1:1 binding stoichiometry. Chemosensor CD2, incorporating a coumarin fluorophore, was structurally confirmed but showed no significant spectral changes when screened with various ions. Chemosensor QD2 exhibited remarkable selectivity for Fe2+ ions, and stable 1:1 complexes were confirmed. Further molecular modeling studies were conducted to identify potential binding sites. Furthermore, five chemosensors (CD1, CD3, QD1, ND1, and ND2) were synthesized and characterized using azo dye reactions, revealing their unique absorption behaviors. Chemosensor CD1 showed high selectivity towards Hg2+ under both absorption and emission spectroscopy. Job's plot studies confirmed a stable 1:1 complex formation. The presence of competing cations did not affect complex formation, emphasizing its stability and selectivity. Another coumarin-containing dye chemosensor, CD3, was synthesized as a novel chemosensor. In the presence of TBA anionic solutions, CD3 exhibited strong absorption bands and selectivity for OH- ions, forming a stable complex with them. Quantitative studies, including the determination of LOD and LOQ, were also conducted. The binding stoichiometry of 1:1 between CD3 and OH- was established through Job's plot analysis. Lastly, two naphthalene dyes were synthesized. However, they did not exhibit selectivity towards cations or anions. Interestingly, their absorption spectra were affected by the change in solvent system, a concept worth exploring in future work. Chemosensor ND1 and ND2 did not show any cation or anion selectivity. However, they demonstrated different spectra and colour responses to cations and anions in different water-DMSO solvent systems. , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Hamukoshi, Simeon Shiweda
- Date: 2024-04
- Subjects: Molecular recognition , Solution (Chemistry) , Water chemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63787 , vital:73613
- Description: Fluorescent molecular chemosensors are crucial tools for monitoring toxic metal ions and environmental compounds that pose risks to both humans and wildlife. Continuous sensing is essential for early detection, and chemosensors offer a sensitive and straightforward approach by detecting challenging analyte’s through optical absorption and fluorescence. Current detection methods, such as flame photometry and mass spectrometry, can be expensive, destructive, and impractical for continuous monitoring. Consequently, fluorescent-based methods present a promising, simple, and highly sensitive alternative for chemical recognition and monitoring. In this project, we successfully synthesized ten highly selective small hydroxyl containing molecule fluorescent and colorimetric sensors; Oxime Dye (OD), Small Sensor 1 (SS1), Small Sensor 2 (SS2), Quinoline Dye 1 (QD1), Quinoline Dye 2 (QD2), Quinoline Dye 3 (QD3), Coumarin Dye 1 (CD1), Coumarin Dye 2 (CD2), Naphthalene Dye 1 (ND1), Naphthalene Dye 2 (ND2). These chemosensors contained benzothiazole, naphthalene, quinoline, and coumarin fluorophores. These sensors facilitate both quantitative and qualitative assessment of cationic and anionic species in aqueous organic media. The chemosensors were synthesized using modified Schiff base, azo dye, and oxime-based reactions, enhancing binding and selectivity with analyte’s. They exhibited selectivity towards various metal ions (Cu2+, Fe2+, Ni2+, and Hg2+) and anions (hydroxyl and cyanate), characterized by distinct absorption bands and significant fluorescent quenching and enhancement. While some sensors were selective towards both cations and anions, others exclusively targeted cations, showing lower selectivity or sensitivity towards anions upon further testing. Conversely, certain sensors were selective towards anions, demonstrating reduced sensitivity or selectivity towards the tested cations. The oxime-based chemosensor, OD, was obtained through an oxime-based reaction. The sensor demonstrates remarkable selectivity for Cu2+ and cyanate ions. During titration experiments, the interaction of Cu2+ with OD resulted in a noticeable fluorescence quenching effect, while the presence of OCN ions led to fluorescence enhancement. These distinct behaviors strongly suggest the formation of specific 1:1 complexes between OD and Cu2+ or OCN ions, a conclusion supported by detailed analysis using the Jobs plot technique. In addition to the fluorescence studies, investigations into the influence of pH on the sensor OD, as well as its complexes with Cu2+ and OCN, were conducted to determine the optimum pH conditions for their operation. Moreover, reversible behavior of the complexes was explored in the presence of EDTA, revealing that only the OD-OCN complex displayed reversibility. Furthermore, molecular modeling studies were performed to validate the binding units and calculate the energy differences between the sensor and its respective complexes. Additionally, four chemosensors (SS1, SS2, CD2, and QD2) were synthesized and characterized using Schiff-based reactions, showcasing their unique absorption behaviors. SS1 and SS2, characterized by benzothiazole fluorophores, demonstrated high sensitivity to hydroxyl anions. Jobs plot studies revealed a stable 1:1 binding stoichiometry. Chemosensor CD2, incorporating a coumarin fluorophore, was structurally confirmed but showed no significant spectral changes when screened with various ions. Chemosensor QD2 exhibited remarkable selectivity for Fe2+ ions, and stable 1:1 complexes were confirmed. Further molecular modeling studies were conducted to identify potential binding sites. Furthermore, five chemosensors (CD1, CD3, QD1, ND1, and ND2) were synthesized and characterized using azo dye reactions, revealing their unique absorption behaviors. Chemosensor CD1 showed high selectivity towards Hg2+ under both absorption and emission spectroscopy. Job's plot studies confirmed a stable 1:1 complex formation. The presence of competing cations did not affect complex formation, emphasizing its stability and selectivity. Another coumarin-containing dye chemosensor, CD3, was synthesized as a novel chemosensor. In the presence of TBA anionic solutions, CD3 exhibited strong absorption bands and selectivity for OH- ions, forming a stable complex with them. Quantitative studies, including the determination of LOD and LOQ, were also conducted. The binding stoichiometry of 1:1 between CD3 and OH- was established through Job's plot analysis. Lastly, two naphthalene dyes were synthesized. However, they did not exhibit selectivity towards cations or anions. Interestingly, their absorption spectra were affected by the change in solvent system, a concept worth exploring in future work. Chemosensor ND1 and ND2 did not show any cation or anion selectivity. However, they demonstrated different spectra and colour responses to cations and anions in different water-DMSO solvent systems. , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
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
- 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
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