Large Enhancement of the Luminescence Properties of an Eu(III) Dye upon Association with the DNA-CTMA Matrix

In this study, the photophysical properties of thin films of an Eu³⁺ dye, namely europium tetrakis(dibenzoylmethide) triethylammonium (EuD₄TEA), within deoxyribonucleic acid (DNA) biopolymer functionalized with hexadecyltrimethylammonium chloride (CTMA) were extensively investigated and compared with those of thin films of the same dye embedded in more conventional polymers, like poly(methyl methacrylate) and polycarbonate. The new materials obtained have good optical properties, as shown by their absorption and emission spectra. Remarkably, a large enhancement in photoluminescence was observed upon the interaction of EuD₄TEA with DNA-CTMA (2- and 17-fold increase in luminescence quantum yield with respect to PMMA and PC). Photophysical analyses suggest that the emission enhancement was mainly due to the increase in the sensitization efficiency (η_sens) from the ligands to the Eu³⁺ ion along with the suppression of the vibrational deactivation upon immobilization onto the DNA-CTMA matrix, as the concentration of the complex increased from 20 to 50%. These phenomena are primarily driven by the transformation of the Eu³⁺ micro-environments, which are created by the interactions between complex ligands and the DNA-CTMA matrix.