Multicomponent nanomaterials consisting of dense scintillating
particles functionalized by or embedding optically active conjugated
photosensitizers (PSs) for cytotoxic reactive oxygen species (ROS)
have been proposed in the last decade as coadjuvant agents for radiotherapy
of cancer. They have been designed to make scintillation-activated
sensitizers for ROS production in an aqueous environment under exposure
to ionizing radiations. However, a detailed understanding of the global
energy partitioning process occurring during the scintillation is
still missing, in particular regarding the role of the non-radiative
energy transfer between the nanoscintillator and the conjugated moieties
which is usually considered crucial for the activation of PSs and
therefore pivotal to enhance the therapeutic effect. We investigate
this mechanism in a series of PS-functionalized scintillating nanotubes
where the non-radiative energy transfer yield has been tuned by control
of the intermolecular distance between the nanotube and the conjugated
system. The obtained results indicate that non-radiative energy transfer
has a negligible effect on the ROS sensitization efficiency, thus
opening the way to the development of different architectures for
breakthrough radiotherapy coadjutants to be tested in clinics.