Azobenzene-derivatized mesostructured silica particles were loaded with guest molecules and release molecules from the pores by the back-and-forth wagging motion of light-activated azobenzenes.

The photophysical properties of azobenzene derivatives connected to silica surface were examined in solution and frozen glass. 

Azobenzene derivatives act as both impellers and gatekeepers when they are tethered in and on mesoporous silica nanoparticles once they are photoactivated.

The controlled release of luminescent probe molecules (opening of the nanovalves) from the supramolecular nanovalves is triggered by weakening the donor-acceptor interactions between the BHEEEN stalks and the CBQPT 4+ rings. The controlled release can be performed by a chemical reduction or photoactivation with built-in photosensitizers.

Upon irradiation (351 nm), the isomerization of trans-to-cis azobenzene units leads to the dissociation of Py--CD or CD rings from the stalks, thus opening the gates to the nanopores and releasing the cargo.

Designed pore interiors of the light-activated mesostructured silica (LAMS) nanoparticles functionalized with azobenzene derivatives. Continuous illumination at 413 nm causes a constant trans–cis photoisomerization about the N–N bond causing dynamic wagging motion of the azobenzene derivatives and results in the release of the molecules through and out of the mesopore.

Excitation with 448 nm light induces the dynamic wagging motion of the nanoimpellers, but the nanovalves remain shut and the contents are contained. Addition of NaOH opens the nanovalves, but the static nanoimpellers are able to keep the contents contained. Simultaneous excitation with 448 nm light AND addition of NaOH causes the contents to be released.