Silica cross-linked nanoparticles encapsulating fluorescent conjugated dyes for energy transfer-based white light emission and porphyrin sensing

This work demonstrated that water-soluble fluorescent hybrid materials can be successfully synthesized by use of silica cross-linked micellar nanoparticles (SCMNPs) as scaffolds to encapsulate fluorescent conjugated dyes for pH sensing, porphyrin sensing and tunable colour emission. Three dyes were separately encapsulated inside SCMNPs (short to dye-SCMNPs). Each of the dye-SCMNPs indicated longer lifetime in water than that of free dye dissolved in organic solvent. The 7-(hexadecyloxy) coumarin-3-ethylformate (HCE) encapsulated inside SCMNPs (HCE-SCMNPs) exhibited fluorescence quenching by pH change in aqueous media. Furthermore, it was confirmed that the radiative and nonradiative energy transfer processes both occurred between HCE-SCMNPs and tetraphenyl-porphyrin (TPP), which were used to synthesize the water-soluble TPP sensor. Significantly, HCE-SCMNPs doped with 5,12-dicotyl-quinacridone (8CQA) and TPP showed water-soluble white light emission (CIE (0.29, 0.34)) upon singlet excitation of 376 nm due to colour adjustment of 8CQA and energy transfer from HCE (donor) to TPP (acceptor).