Aggregation-enhanced fluorescence in organically modified silica nanoparticles: A novel approach toward high-signal-output nanoprobes for two-photon fluorescence bioimaging

A new two-photon fluorescent nanoprobe based on originally modified silica (ORMOSIL) nanoparticles loaded with high concentration of a dye exhibiting aggregation-enhanced two-photon adsorption (TPA) and fluorescence bioimaging was reported. The particle size was analyzed by transmission electron microscopic (TEM) images showing a good agreement with the number-averaged size distribution in aqueous suspension. The results show that after removal of the anoinic surfactant (AOT) by dialysis against deionized water, all the composite nanoparticles have a negative potential. The fluorescence spectrum of the composite nanoparticles are red-shifted with the increasing TPA dye loading, due to an increase in the effective π-conjugation length. The TPA dye in ORMOSIL nanoparticles has the potential to achieve several orders of magnitude improvement in the intracellular TPA signal, over existing fluorescent dye.