Symbiosis between photoactive nanoparticles and their organic ligands.

Photoactive spherical metal and semiconductor nanoparticles (NPs) are smart systems that exhibit unique properties, such as a high surface-to-volume ratio, a broad absorption spectrum and size-dependent properties. They are capped with a considerable number of ligands required to give rise to stable organic and aqueous NP colloidal solutions. In addition, the ligands can also be used to introduce functionality at the NP periphery. In this case, the NP could act as a 3D-scaffold, which would make a high local concentration of a functional moiety at the NP periphery possible, moreover, the photophysical properties of the NP could be tuned. The combined action of the organic capping and the inorganic core can exert an encapsulating effect, i.e. the organic capping could establish specific interactions with nearby molecules and this would enable the molecules to approach or interact with the NP surface. Therefore, the NP core and the ligand can work together providing the overall hybrid system with new properties or capacities. The relevance of the cooperative action between the spherical photoactive core and the capping are shown in this report with several recent examples developed by my research group, some of them in collaboration with other groups.