Fluorous Nanoemulsion Optodes with Förster Resonance Energy Transfer-Based Fluorescence Amplification Toward Highly-Sensitive and Selective Detection of Perfluorooctanesulfonate

Abstract

As a fundamental study toward highly sensitive perfluorooctanesulfonate (PFOS−) sensing using fluorous nanoemulsion (NE) optodes, fluorescence enhancement by Förster resonance energy transfer (FRET) was investigated. By incorporting fluoroalkyl-containing donor and acceptor dyes into hydrophobic nanodroplets, efficient FRET was realized, and the acceptor fluorescence intensity was enhanced by approximately 9.3 times compared to the conventional system without FRET. Fluorous NE optodes with FRET exhibited higher sensitivity to low PFOS− concentrations and the lowest detectable PFOS− concentration was on the order of 10−8 to 10−7 M. On the other hand, the response of interfering anions was suppressed by introducing fluoroalkyl chains into the donor dye matrix. It was revealed that the relative selectivity of PFOS− against interfering anions was improved by one to three orders of magnitude in logarithmic selectivity coefficient (log "K" _(〖"PFOS" 〗^"-" ",j" )^"opt" ). Furthermore, the applicability of the method was further demonstrated by PFOS− detection in tap water and artificial seawater, where concentration-dependent responses were maintained under appropriate conditions.