Eriochrome Black T-Eu Complex as a Ratiometric Colorimetric and Fluorescent Probe for the Detection of Dipicolinic Acid, a Biomarker of Bacterial Spores.

A novel ratiometric colorimetric and fluorescent dual probe based on Eriochrome Black T (EBT)-Eu complex was designed to detect dipicolinic acid (DPA), a major constituent of bacterial spores, with high sensitivity and selectivity. UV-vis titration experiments demonstrated that EBT and Eu ions formed a 1:1 coordination pair in water. In the presence of Eu ions, the blue solution of EBT changed to magenta, however, upon the addition of DPA, the magenta color changed to blue immediately and characteristic fluorescence emission from DPA-Eu complex was observed. In addition, the sensitivity of the system was further evaluated on Geobacillus stearothermophilus spores and as low as 2.5 × 10 spores were detected.