For the optical detection of anthrax biomarker using a luminescent rare earth-organic framework modified by rhodamine molecules: Synthesis, characterization and two sensing channels.

This work was devoted to the synthesis and performance report of an optical sensing platform for dipicolinate (DPA), which was known as a biomarker for Bacillus anthracis spores. This DPA optical sensing platform (denoted as EuBTC@RB) was composed of luminescent rare earth MOF and rhodamine-derived sensing probe. Its structure was discussed and confirmed by means of XRD, IR, TGA, absorption, emission and excitation spectra. EuBTC@RB showed two sensing channels for DPA, including colorimetric sensing and ratiometric fluorescent sensing. Linear response was found for both sensing channels, with LOD value of 3.4 μM. Its sensing mechanism was discussed and confirmed as the combination of an emission turn off effect caused by energy transfer process (EuBTC → DPA pyridine) and an emission turn on effect of rhodamine molecules triggered by DPA-released protons. EuBTC@RB showed its advantage over traditional DPA optical sensing systems due to its dual sensing skills and the possibility of naked eye detection.