Efficient Dispersion of Organic Fluorophores by Size Matching with a Difunctionalized Spacer Interleaved into Layered Double Hydroxide

Strongly luminescent when diluted in aqueous solution, Sulforhodamine B (SRB) is an organic dye suffering from aggregation-caused quenching in its solid state. Its cointercalation in very small quantities (0.12 mol %) in a layered double hydroxide (LDH) matrix with phenylenedipropionate (PPA) anions, a difunctionalized spacer matching its size, is found to be highly effective, with more than 99% of the SRB molecules taken up. The resulting hybrid material enables luminescence, with an absolute photoluminescence quantum yield (PLQYabs) reaching 39% under UV excitation and even reaching 60% at its maximum. The dispersion of the LDH dye powder in silicone results in homogeneous composite films with loading as high as 40 wt % useable as a masterbatch. The optical properties are found to remain after thermal treatment up to 120 °C, with a decrease in PLQYabs of only 5%, making it a good candidate for the development of rare-earth-free phosphors.