Here, we present the optical detection of chloride ions with co-extraction based anion-selective optodes containing a BODIPY derivative (BDP-OH) and the ionophore In(OEP)Cl. Spectroscopic studies suggested that BDP-OH and In(OEP)Cl formed an adduct BDP-O-In(OEP), which was converted to BDP-OH and In(OEP)Cl upon increasing sample Cl- concentration, and induced signal changes in both fluorescence and absorbance modes. The method was evaluated in polystyrene-graft-poly(ethylene oxide) (PS-PEO) nanospheres (ca. 40 nm in diameter) and on cellulose paper. In contrast to Cl- probes based on fluorescence quenching, the nanospheres exhibited turn-on fluorescence and ratiometric absorbance responses to a tunable Cl- concentration range (10 μM-1 M). Through fluorescence microscopy, the nanospheres were able to respond to Cl- concentration changes in HeLa cells. Cellulose paper-based Cl- optodes with colorimetric response were successfully used to measure Cl- in artificial sweat, providing a potential analytical tool for clinical diagnosis of cystic fibrosis.
Keywords: Cellulose paper; Chloride ion; Ion-selective optode; Ionophore; Nanosphere.
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