A near-infrared fluorescent probe for selective and quantitative detection of fluoride ions based on Si-Rhodamine.

A highly selective fluorescent probe (SiROPS) based on Si-rhodamine (SiR) towards F- was investigated. SiROPS can realize the NIR detection of F- because of the long fluorescent wavelength (λex = 650 nm, λem = 669 nm). The near-IR optical and the ratiometric fluorescence type signaling were realized by employing fluoride-selective cleavage of the latent thiophosphinated probe in mixed aqueous media. The cleavage of F- to the ortho positions of dimethylphosphinothionyl group in the meso aryl involves the suppression of internal rotation upon phosphorylation of a reactive phenolate and the activating rotation of o-OH, which resulting in a large fluorescence "Turn-Off" response. The detection limit of the probe to F- was 48 nM in the dynamic range of 0.5 µM-20 µM. In addition, the proposed probe has been used to detect F- in water samples and toothpaste samples with satisfying results.