Optical and Metal Ion Sensing Properties of Electronically Conducting Monomers and Polymer
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Date
2011-06
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Addis Ababa Universty
Abstract
Herein, the optical metal ion sensing properties of monomers (M1 and M2) containing imidazole
group as molecular recognition units and conjugated polymer (P1) carrying thiophine and
thiazole in their backbone were studied. Absorption and fluorescence emission spectra of the
materials considered were not significantly changed in different solvents. Sensing ability of the
monomers and the polymer solutions to metal ions was carried out using fluorescence
spectrometer. Both monomers were highly selective and sensitive optical chemosensor only to
Fe3+ ion in THF, chloroform, and dioxane. The sensing principle was based on fluorescence
quenching by forming complex between Fe3+ and imidazole group in the monomers backbone.
The limit of detection values (LOD) for M1 and M2 in THF were 1.386x10-5 mol/L and
3.902x10-6 mol/L, respectively. Moreover, LOD values for M1 and M2 in chloroform obtained
were 1.315x10-5 mol/L and 3.707x10-5 mol/L, respectively. The sensitivity of the monomers
towards Fe3+ ion was compared by calculating Stern-Volumer constant (Ksv). The Ksv values
found for M1 and M2 in THF were 6.474x102 M-1 and 1.495x103 M-1, respectively, and in
chloroform the Ksv values obtained for M1 and M2 were 3.928x102 M-1 and 5.535x102 M-1,
respectively. Results obtained showed that monomer M2 was more sensitive than M1 towards
Fe3+ in all solvents considered. The fluorescence spectra of conjugated polymer P1 in THF,
toluene, chloroform, and dioxane was insensitive to all metal ions considered.
Key words optical chemical sensor; molecular recognition; fluorescence quenching; Stern-
Volumer constant
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Keywords
Optical chemical sensor, Molecular recognition, Fluorescence quenching, Stern- Volumer constant