Anion-exchangeable modulated fluorescence strategy for sensitive ascorbic acid detection with luminescent Eu hydroxy double salts nanosunflowers derived from MOFs

To improve the sensitivity and avoid the interference of other substances to the detection of ascorbic acid (AA), luminescent Eu hydroxy double salts (Eu HDSs) sunflowers were developed for fluorescence turn-off detection of AA based on anion-exchangeable strategy. Such Eu HDSs nanoprobe was synthesized by using a leaf-like metal-organic-framework-5 (MOF-5-L) as both precursor and template and europium (III) trifluoroacetate trihydrateas a second precursor. The mechanism of the luminescence inhibition of the Eu HDSs nanosunflowers was studied, and the intercalation of anionic AA-species into an interlayer of Eu HDSs helped to enhance luminescence inhibition, which was quite different from the reported redox-based fluorescent sensing system. Because of the existence of space effect and hydrogen bond between the AA and the OH group on the Eu HDSs surface, such nanoprobe showed excellent sensitivity and selectivity for AA detection, with the detection limit of 1.46 nM. Moreover, the nanoprobe was successfully used for sensitive and selective AA assays in human body fluids, proving that the proposed sensing platform has great potential in the clinical diagnosis and drug screening.