Fabrication of an electrochemical sensor based on spiropyran for sensitive and selective detection of fluoride ion

• Endogenous redox group in spiropyran skeleton avoids the appearance of the false positive signals.
• SWCNTs effectively amplify the electrochemical signal to improve the detection sensitivity.
• The specific reaction between F− and silica shows excellent anti-interference ability in urine and blood samples.

In the past decades, numerous electrochemical sensors based on exogenous electroactive substance have been reported. Due to non-specific interaction between the redox mediator and the target, the instability caused by false signal may not be avoided. To address this issue, in this paper, a new electrochemical sensor based on spiropyran skeleton, namely SPOSi, was designed for specific electrochemical response to fluoride ions (F−). The breakage of Si–O induced by F− based on the specific nucleophilic substitution reaction between F− and silica would directly produce a hydroquinone structure for electrochemical signal generation. To improve the sensitivity, SPOSi probe was assembled on the single-walled carbon nanotubes (SWCNTs) modified glassy carbon electrode (GCE) through the π–π conjugating interaction. This electrode was successfully applied to monitor F− with a detection limit of 8.3 × 10−8 M. Compared with the conventional F− ion selected electrode (ISE) which utilized noncovalent interaction, this method displays higher stability and a comparable sensitivity in the urine samples.

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