Rhodamine B schiff base colorimetric and fluorescent chemosensors for the detection of Cu2+, Al3+ AND Co2+: synthesis, mechanism and application / Chan Wei Chuen
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...
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| Format: | Thesis |
| Published: |
2023
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| Online Access: | http://studentsrepo.um.edu.my/15144/2/Chan_Wei_Chuen.pdf http://studentsrepo.um.edu.my/15144/1/Chan_Wei_Chuen.pdf http://studentsrepo.um.edu.my/15144/ |
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| Summary: | 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+.
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