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

Abstract

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).