Fluorescent phenylethynylene calix[4]arenes for sensing TNT in aqueous media and vapor phase

Abstract

The upper-rim of calix[4]arene is modified with phenylacetylene derivatives via Sonogashira coupling reaction to produce a wider cavity for entrapping TNT. The modified calix[4]arene with amino groups on the wider rim exhibits highly selective fluorescence quenching toward TNT compared to other nitro aromatic compounds in an aqueous medium due to the shape and hydrophobicity of the modified cavity. The limit of detection of TNT is 0.3 μM (68 ppb) in water and the Stern–Volmer fluorescence quenching constant is 1.09 × 10⁵ M⁻¹.