  The knowledge of the carrier dynamics in nanostructures is of fundamental
importance for the development of (opto)electronic devices. This is true for
semiconducting nanostructures as well as for plasmonic nanoparticles (NPs).
Indeed, improvement of photocatalytic efficiencies by combining semiconductor
and plasmonic nanostructures is one of the reasons why their ultrafast dynamics
are intensively studied. In this work, we will review our activity on ultrafast
spectroscopy in nanostructures carried out in the recently established EuroFEL
Support Laboratory. We have investigated the dynamical plasmonic responses of
metal NPs both in solution and in 2D and 3D arrays on surfaces, with particular
attention being paid to the effects of the nanoparticle shape and to the
conversion of absorbed light into heat on a nano-localized scale. We will
summarize the results obtained on the carrier dynamics in nanostructured
perovskites with emphasis on the hot-carrier dynamics and in semiconductor
nanosystems such as ZnSe and Si nanowires, with particular attention to the
band-gap bleaching dynamics. Subsequently, the study of semiconductor-metal NP
hybrids, such as CeO$_2$-Ag NPs, ZnSe-Ag NPs and ZnSe-Au NPs, allows the
discussion of interaction mechanisms such as charge carrier transfer and
F{\"o}rster interaction. Finally, we assess an alternative method for the
sensitization of wide band gap semiconductors to visible light by discussing
the relationship between the carrier dynamics of TiO$_2$ NPs and V-doped
TiO$_2$ NPs and their catalytic properties.
