Dual channel detection for anthrax biomarker dipicolinic acid: The combination of an emission turn on probe and luminescent metal-organic frameworks

Dipicolinate (DPA) is a biomarker for Bacillus anthracis spores. In this effort, an optical sensing composite with two sensing channels for the detection of dipicolinate (DPA) was reported. This composite material was constructed using luminescent metal-organic framework (MOF) as supporting substrate and a rhodamine-liked dye as sensing probe, respectively. By means of electron microscopy images, XRD, IR, TGA, absorption and emission spectra, this composite sample was characterized carefully. It was found that there were two sensing channels for DPA, including colorimetric sensing and ratiometric fluorescent sensing. Linear sensing response was observed for both sensing channels. LOD value was as low as 4.5 μM with good selectivity. Corresponding sensing mechanism was revealed as a rhodamine structural transformation initiated by DPA released protons and an emission quenching caused by energy transfer from Eu(BTC) to DPA (pyridine ring). This composite material showed a superior sensing performance in virtue of its dual sensing channels and the possibility of naked eye detection.