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. 2011;11(5):4598-608.
doi: 10.3390/s110504598. Epub 2011 Apr 27.

Fluorescent sensing of chlorophenols in water using an azo dye modified β-cyclodextrin polymer

Phendukani Ncube  1 , Rui W Krause, Bhekie B Mamba
Affiliations

Fluorescent sensing of chlorophenols in water using an azo dye modified β-cyclodextrin polymer

Phendukani Ncube et al. Sensors (Basel). 2011.

Abstract

A water soluble azo dye modified β-cyclodextrin polymer 4 was synthesized and used as a chemosensor for the detection of chlorinated phenols, model chlorinated by-products (CBPs) of water treatment for drinking purposes. The characterization of the intermediates and the azo dye modified β-CD polymer was done by UV/Vis Spectrophotometry, FT-IR and (1)H-NMR spectroscopies. The chlorophenols were capable of quenching the fluorescence of the polymer. The polymer showed greater sensitivity towards 2,4-dichlorophenol, with a sensitivity factor of 0.35 compared to 0.05 and 0.12 for phenol and 4-chlorophenol, respectively. The stability constants (K(s)) of the pollutants were also determined by the Benesi-Hildebrand method to be 2.104 × 10(3) M(-1) for 2,4-dichlorophenol and 1.120 × 10(2) M(-1) for 4-chlorophenol.

Keywords: azo dye; chemosensor; chlorinated by-product; fluorescence; β-cyclodextrin polymer.

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Figures

Figure 1.
Figure 1.
Effect of pH on (A) azo dye modified β-CD and (B) azo dye modified β-CD polymer.
Figure 2.
Figure 2.
Fluorescence spectra of the azo dye CD polymer in different solvents. (λexc = 305 nm).
Figure 3.
Figure 3.
Fluorescence spectra of dye modified CD polymer on addition of different pollutants. {[Dye-CD-Polymer] = 50 ppm; [Pollutant] = 2.0 mM}.
Figure 4.
Figure 4.
Fluorescence quenching by addition of increasing amounts of 2,4-DCP. {[Dye-CD-Polymer] = 50 ppm; [2,4-DCP] = 0 mM to 2.7 mM}.
Figure 5.
Figure 5.
Plot of concentration of 2,4-DCP versus the change in fluorescence intensity (ΔI) with each addition of 2,4-DCP.
Figure 6.
Figure 6.
Benesi-Hildebrand plot of CD dye polymer in presence of 2,4-DCP (0–2.7 mM).
Scheme 1.
Scheme 1.
Structure of azo dye modified β-cyclodextrin.
Scheme 2.
Scheme 2.
Synthetic route to cyclodextrin polymer 4.
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