Excitation energy transfer in artificial antennas: from photoactive materials to molecular assemblies

Abstract

The development of nanometrically templated artificial light harvesting antennas and energy transfer devices is a highly active area with outstanding challenges. The herein presented review deals with the design of photoactive nanomaterials and multichromophoric arrays looking towards the development of artificial antenna systems. In particular we have focused in the conditions which rule the excitation energy transfer processes in each case. To this aim, a wide variety of luminescent fluorophores encapsulated into either inorganic or organic hosts, as well as molecular systems based on scaffolding of suitable laser dyes have been deeply studied. The main goal is to design systems which harvest the light over a broad spectral region (in particular the ultraviolet-visible section of the electromagnetic spectrum) and transfer it to the target place and with a desired energy (especially in the red edge of the visible) via successive energy transfer hops. To this purpose, three different approaches have been considered to develop optical antennas: (i) hybrid materials based on LTL zeolite aluminosilicate doped with laser dyes absorbing and emitting in different regions of the visible (blue, green or red); (ii) dye-doped latex nanoparticles, in which luminescent fluorophores undergoing intermolecular energy transfer processes are encapsulated; (iii) molecular antennas based on donor and acceptor dyes covalently linked through a spacer. These luminescent antennas have been designed for photonic purposes such as tunable dye lasers, light modulators or polarity probes.