DOI: 10.1002/asia.201300936 Promotion of Fçrster Resonance Energy Transfer in a Saponite Clay Containing Luminescent Polyhedral Oligomeric Silsesquioxane and Rhodamine Dye Francesco Olivero, [a] Fabio Carniato, [a] Chiara Bisio, [a, b] and Leonardo Marchese* [a] Introduction The development of artificial light-harvesting systems repre- sents an important research field for the design and fabrica- tion of innovative energy-storage devices. Taking inspiration from photosynthetic natural systems, great efforts and stud- ies have been carried out to build so-called “photonic anten- nae”, whereby the chromophoric units are specifically or- ganized in space, so that the harvested light is all channeled through energy-transfer steps to a common reaction center. [1, 2] In this regard, several systems have been developed and studied for energy-transfer processes, including multinuclear metal complexes, [3] dendrimeric species, [4] dye molecules em- bedded in polymeric matrices, [5] and quantum dots. [6] Host–guest assemblies have received much attention, es- pecially for the possibility that they offer in improving the photostability of chromophores, avoiding aggregation and conferring high organization through spatial constraints, which is an important requirement for building up more complex nanoarchitectures. [7–12] The pioneering works reported by the groups of Tolbert [7] and Brühwiler [8] have demonstrated that the control of Fçr- ster resonance energy transfer (FRET) for polymers and dyes encapsulated in porous materials is possible. Lumines- cent entities entrapped in micro- or mesoporous silica can be characterized by efficient FRET; this allows the emission processes of hybrid materials to be tuned. [13] As an alterna- tive to porous solids, layered materials could be good candi- dates for the fabrication of photonic antennae for several reasons: 1) it is possible to tune the amount of luminescent dyes by modifying the charge density of the clay lamellae thus reducing dye aggregation, [14] and 2) the clay inorganic layers can limit oxygen diffusion [15] thus chemically and/or thermally stabilizing the guest molecules located in the in- terlayer space. Moreover, layered materials can be, in gener- al, processed in film form, [16] and this is a key step for the fabrication of new light-emitting devices. In recent years, finely controlled FRET was achieved for organic dyes intercalated in layered silicates. [17] In this case, dye molecules arranged in two-dimensional molecular as- semblies are confined in the interlayer space of silicate layers. Few examples report on the use of clay minerals as host solids for the fabrication of artificial photonic anten- nae. [18] In such cases, FRET processes were promoted in the interlayer space of clays with a low cation exchange capacity (CEC) to avoid dye aggregation. In our approach, a new hybrid photonic antenna was opti- mized by realizing a photostable layered system, in which an intercalated donor molecule transferred excitation energy directly to an acceptor dye located in close proximity. The hybrid solid was prepared by intercalating a luminescent polyhedral oligomeric silsesquioxane (POSS), [19] containing a fluorescein derivative and an amino group suitable for Abstract: A new hybrid photostable saponite clay with embedded donor– acceptor dyes was prepared and char- acterized in this work. The saponite is intercalated with a luminescent poly- hedral oligomeric silsesquioxane, which transfers the photoexcitation energy di- rectly to an acceptor dye (rhodami- ne B). The obtained composite materi- al was characterized by means of XRD, TEM microscopy, and UV/Vis and photoluminescence spectroscopy. A physicochemical study showed that the system behaved as an efficient Fçrster resonance energy transfer pair, owing to the very good spectral overlap of donor emission (l em = 510–540 nm) and acceptor absorption in the l = 530– 570 nm range. The hybrid material rep- resents the first example of a photonic antenna based on a synthetic saponite clay and can be considered a step for- ward in the search for new, efficient, and stable materials suitable for light- harvesting applications. Keywords: clays · donor–acceptor systems · dyes/pigments · FRET · photochemistry [a] F. Olivero, Dr. F. Carniato, Dr. C. Bisio, Prof. L. Marchese Dipartimento di Scienze e Innovazione Tecnologica and Nano-SISTEMI Interdisciplinary Centre Università del Piemonte Orientale “A. Avogadro” V. Teresa Michel, 11, 15121 Alessandria (Italy) Fax: (+ 39) 0131360250 E-mail : leonardo.marchese@mfn.unipmn.it [b] Dr. C. Bisio ISTM-CNR Istituto di Scienze e Tecnologie Molecolari Via G. Venezian, 21 Milano (Italy) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201300936. Chem. Asian J. 2014, 9, 158 – 165  2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 158 FULL PAPER