Browsing by Author "Mersha Wassie"

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    Optical and Metal Ion Sensing Properties of Electronically Conducting Monomers and Polymer
    (Addis Ababa Universty, 2011-06) Mersha Wassie; Admassie Shimelis (PhD)
    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