Electrochemiluminescent polymer films with a suitable redox "turn-off" absorbance window for remote selective sensing of Hg ²⁺

An electrochemiluminescent sensing scheme is presented for remote detection of Hg²⁺ through an ITO-coated nanostructured optical fibre bundle. It is based on the electropolymerisation of CPDT-linked ruthenium phenanthroline complexes carrying azacrown ethers as the receptor units (CPDT = 4H-cyclopenta[2,1-b:3,4-b′]dithiophene). The application of an anodic potential simultaneously induces electrogenerated chemiluminescence (ECL) and turns off the absorbance of the polymer backbone at the ECL emission wavelength. Therefore, the electropolymer film allows ECL light generation and transmission for efficient remote sensing in a synergetic way. As a proof of concept, selective detection of Hg²⁺ was demonstrated remotely by ECL through an optical fibre bundle.