A tailor-made fluorescent ionic liquid integrating tetrapropylammonium hydroxide with 1-naphathoic acid to construct a dual-emitting fluoroprobe for sensing hydroquinone in environmental waters

Abstract

Herein, a dual-emitting fluoroprobe was pioneered for the sensitive and selective detection of hydroquinone (HQ) in environmental waters, which was based on integration of a tailor-made fluorescent ionic liquid ([TBAOH][NA]) with Eu3+ (([TBAOH][NA]/Eu3+). HQ could substantially enhance the 365-nm fluorescence intensity (FI365) of [TBAOH][NA]/Eu3+, whereas no prominent variation ocurred in FI615. After HQ binding with [TBAOH][NA], the electronic structure of S1 was completely pi-pi*, and the orbital overlap of the latter was much higher, thereby promoting photon transitions. After some key factors were optimized using a central-composite-design (CCD) approach, this fluroprobe provided a linear response from 0.5 to 100 μM and detection limit of 0.15 μM for HQ assay, which was comparable to analytical performance by conventional HPLC-DAD analysis. Overall, the prominent advantages of as-developed fluoroprobe lie in two aspects: (1) Employing the ratio of two well-resolved emission and significantly differential responses to HQ greatly enhance sensitivity and accuracy through a self-calibration system; and (2) [TBAOH][NA] has not only the superiority of “green solvent” like conventional ionic liquids, but also possesses strong luminescence signal owing to introducing 1-naphathoic acid as an anion into tetrapropylammonium hydroxide. Consequently, this dual-emitting fluoroprobe is endowed with great potential in on-site and outdoor HQ monitoring.