Light-induced and redox-triggered uptake and release of substrates to and from mesoporous SiO₂ nanoparticles

The photonic- and redox-triggered cyclic uptake and release of organic substrates in functionalized mesoporous SiO₂ nanoparticles (NPs) is demonstrated. The mesoporous SiO₂ NPs are functionalized with nitrospiropyran photoisomerizable units. Rhodamine B is encapsulated in the channels of the SiO₂ NPs and trapped by the hydrophobic nitrospiropyran capping units. Photoisomerization of the capping units to the protonated nitromerocyanine groups opens the channels and releases the encapsulated dye. Similarly, modification of the SiO₂ channels by chloronaphthoquinone units traps eosin Y in the channels, by means of donor-acceptor interactions. The reduction of the quinone units to the chloronaphth hydroquinone donor groups opens the channels and releases the encapsulated substrate. The novelty of the study rests on the demonstration of the reversible and cyclic photostimulated or redox-activated uptake and release of substrates from the mesoporous SiO₂ NPs.