A europium (III) based nano-flake MOF film for efficient fluorescent sensing of picric acid

Abstract

The authors describe a fast response-recovery characteristics of optical sensing platform based on a luminescent thin film composed of a nano-flake metal organic framework (MOF) of the type [Eu4(NDC)6(H2O)5]·3H2O (referred to as Eu-NDC), where NDC stands for naphthalene-2,6-dicarboxylate. The film can be prepared within 20 s and shows strong luminescence (with excitation/emission maxima at 355/614 nm) that is characteristic for Eu(III) ion sensitized by the electron-rich ligands. The structure of the MOF films is confirmed by powder X-ray diffraction, and their surface morphology is examined by scanning electron microscopy. The luminescence of the sensor film is strongly quenched by picric acid (PA), and this finding is exploited in a sensing scheme for PA with good selectivity over other nitroaromatic explosives. The limit of detection for PA is 0.67 μM. The luminescence quenching mechanisms were also investigated. The sensor is easily prepared, stable, and can be recycled by rinsing with water. It was also applied to the determination of PA in Pearl River water that was spiked with PA.