Rhodamine B schiff base colorimetric and fluorescent chemosensors for the detection of Cu2+, Al3+ AND Co2+: synthesis, mechanism and application / Chan Wei Chuen

Chan , Wei Chuen (2023) Rhodamine B schiff base colorimetric and fluorescent chemosensors for the detection of Cu2+, Al3+ AND Co2+: synthesis, mechanism and application / Chan Wei Chuen. PhD thesis, Universiti Malaya.

	PDF (The Candidate's Agreement) Restricted to Repository staff only Download (199Kb)
	PDF (Thesis PhD) Download (3926Kb)

Abstract

Essential trace elements such as metal ions play an important role in biological system and are fundamental to the health of living organisms. However, overload of these elements may cause several diseases. Metal pollution has been a regular environmental concern for human and the whole ecosystem. The traditional approaches for tracing these metal ions, however are hampered by certain drawbacks which make it impractical and inconvenient for real-time on-site detection. Hence, an alternative method (chemosensor) is highly sought after. Four new rhodamine Schiff base chemosensors were synthesized through the condensation reaction of rhodamine B hydrazide with 2,3,4- trihydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde, (3-formyl-4- hydroxybenzyl)triphenylphosphonium chloride and 4-propoxybenzaldehyde to form sensors R234, R34, RTPP, R4P respectively. Structure of these four chemosensors were elucidated using spectroscopic techniques such as IR, 1H NMR, 13C NMR, MS and X-ray crystallography. Performances (sensitivity, selectivity and reversibility) of the synthesized sensors were analyzed using UV-Vis and fluorescence spectroscopy. The results indicated that sensor R234 was able to selectively detect Co2+ and Cu2+; whereas sensor R34, RTPP and R4P were able to selectively detect Al3+ and Cu2+. High association constant (Ka > 103) and low limit of detection even to nano-molar level (LOD of R34 to Al3+ = 5.63 nM) indicate the good sensitivity of the synthesized sensors toward the targeted metal ions. Reusability of the sensors studied through utilization of EDTA, showed that most of the sensor-metal complexes were showing reversible interaction except for R234-Co2+ and RTPP-Al3+. Binding mode of sensors with metal ions were investigated through Job’s plot, IR, 1H NMR and MS. The results corroborate that the complexation with metal ions is through the oxygen and nitrogen atom of the amide carbonyl which led to the opening of the spirolactam ring. The findings from Job’s plot showed that the four synthesized sensors were bonded to their target metal ions in different binding stoichiometry (1:1, 1:2, 1:3 and 2:1 sensor:metal). Application of sensors were evaluated using spike-and-recovery water sample analysis where all the four sensors demonstrated the ability to detect target metal ions in the two selected water samples, tap water and natural mineral water with recovery range of 80-120%. Other than that, fluorescence bio-imaging studies showed that RTPP, can be successfully uptaken by HCT116 cell lines and behaved as an acidic pH indicator in the cell. Taken togehter, we have successfully synthesized four new rhodamine Schiff base “OFF-ON” colorimetric and fluorometric chemosensors that support rapid real-time “naked-eye” detection of metal ions. The ease of synthesis and portability of these ligands suggest the potential application as an on-site test kit for Al3+, Co2+ and Cu2+.

Actions (For repository staff only : Login required)