The synthesis and characterization of chemical sensors and their application to anions and heavy metal ions sensing

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Date
2022
Journal Title
Journal ISSN
Volume Title
Publisher
University of Namibia
Abstract
Cations and anions play a major role in the biological and physiological processes in living organisms attracting more research interest in the area of chemical sensing. However, the excessive accumulation of ions in living organisms, particularly in humans, is toxic and can lead to health problems. Chemosensing is a powerful tool that can be employed to detect these ions in an environment. This is due to their high selectivity and sensitivity for the target analytes. Therefore, this research worked on designing two dual receptors namely A and C. These chemosensors were designed based on the fluorophore-spacer receptor principle and they have been synthesized based on the environmentally friendly and cost-effective Schiff base method. The synthesized chemosensors were characterized using a Proton Nuclear Magnetic Resonance (1H NMR), Fluorescence and Ultraviolet-visible (UV-Vis) spectrophotometer. The research findings have indicated that both receptor A and receptor C are colorimetrically and spectroscopically selective and sensitive to multiple cations and anions. Receptor A displayed a naked eye colorimetric sensitivity and spectrally towards; Co2+, Cu2+, Fe2+ while with the anions only spectral sensitivity was displayed. For both cations and anions a red shift in absorption with isosbestic points at 286 nm and 284 nm respectively, and fluorescence enhancement were observed, except for Fe2+, were no isosbestic point was observed and fluorescence quenching was noted. Similarly, receptor C presented both naked eye colorimetric sensitivity and spectrally towards these anions: CN- , F- , AcO- , OCN- , OH- and these cations: Cu2+, Fe2+ Zn2+, Ni2+, Hg2+. A bathochromic shift and fluorescence enhancement were observed with the anions, while for the cations absorption varies depending on the cations’ identity. Moreover, fluorescence quenching ii was observed with most cations, with an exemption for Hg2+ and Al3+ with fluorescence enhancement.
Description
A mini thesis submitted in partial fullfilment of the requirements for the Degree of Master of Science (Chemistry)
Keywords
Chemosensor, Naked eye detection, Cation, Anion, Multi-sensing
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