Highly selective “turn-on” fluorescent sensing of fluoride ion based on a conjugated polymer thin film-Fe3+ complex

• The thin film was prepared by electropolymerization of the electroactive monomer M.
• The thin film could effectively detect Fe3+ as a turn-off sensor, and exhibited outstanding reversibility.
• The film-Fe3+ complex showed a highly selective turn-on response toward F− over other anions.

We designed a new fluorescent conjugated polymer thin film sensor via direct electropolymerization of the corresponding electroactive monomer M onto the surface of ITO electrode, and the thin film-Fe3+ complex was used for the highly-selective detection of fluoride ion (F−) in water environmental samples. The as-obtained thin film could effectively detect Fe3+ as a selective turn-off fluorescent sensor, and exhibited outstanding reversibility. This film in the presence of Fe3+ showed a highly selective turn-on response toward F− over other anions with a 5-fold enhancement in the fluorescence intensity. F− with a relatively wide concentration range from 10 μM to 3 mM could be determined in a rather simple and sensitive manner with a detection limit of 6.78 μM (0.128 ppm). Analytical applicability of the film-Fe3+ complex for determining the levels of F− in environmental water samples has been successfully demonstrated by fluorescent analysis with satisfactory results. This strategy will provide a new approach for the facile design of new molecular sensing devices and practical application in environments.

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