Abstract
A two‐photon photosensitizer with four triethoxysilyl groups is synthesized through the click reaction. This photosensitizer allows the design of bridged silsesquioxane (BS) nanoparticles through a sol–gel process; moreover, gold core BS shells or BS nanoparticles decorated with gold nanospheres are synthesized. An enhancement of the two‐photon properties is noted with gold and the nanoparticles are efficient for two‐photon imaging and two‐photon photodynamic therapy of cancer cells.