School of Natural and Environmental Sciences

Event items

Mimicking the Antenna System of Green Plants

Chemistry Seminar Series - Professor Gion Calzaferri, University of Bern

Date/Time: Tuesday 23 October 2018, 14:00 - 15:00

Venue: Room 2.76, Bedson Building

Supramolecular organization of dyes in nanochannels highlights and challenges

Natural photosynthesis is the essential process for life on earth. Its overall thermodynamic efficiency for the production of fuel is low, however, and depends much on optimal soil, temperature, and humidity conditions.

Natural photosynthesis has many other important tasks to fulfill than just conversion of solar light into a chemical fuel.

Artificial photosynthetic challenge

A long-standing challenge has therefore been the development of an artificial photosynthetic system that is specialized on the energy conversion process. [1]

Green plants have developed sophisticated and highly efficient tools for harvesting light and transporting electronic excitation energy. Their antennas consist of regular arrangements of chlorophyll molecules held by proteins at fixed positions.

Light absorbed by any of these chromophores is transported to the reaction center, providing the energy necessary for the chemical processes to be initiated. A green leaf consists of millions of such well organized antenna devices.

Mimicking light harvesting of the natural antenna

Mimicking the light harvesting property of the natural antenna has been an old dream of photo chemists. Different strategies for achieving this goal have been followed. [2]

We have focused on a design based on the incorporation of chromophores into the one-dimensional (1D) channels of zeolite L (ZL). [3]

Sequential insertion of different dyes into the 1D channels of ZL leads to supramolecular sandwich structures and allows the formation of sophisticated antenna composites for light harvesting, transport, and trapping. The first report in literature on Time- and Space-Resolved Luminescence of a Photonic Antenna was based on such a composite.[4]

Our concept

Our concept also lead to the invention of the stopcock principle [5] which turned out to be very successful for designing materials of interest as smart composites for luminescent solar concentrators (LSC), optoelectronics, sensing, and diagnostics. [6,7,8]

A possibility to achieve higher levels of organization is by assembling the composites into ordered structures.[6] The usually strong light scattering of ZL can be suppressed by refractive index matching and avoidance of micro phase separation. [7]

The tiny nanochannels of ZL facilitate achieving well organized sandwich structures, but many interesting molecules are simply too large for entering these channels. The use of mesoporous hosts extends the field of possibilities and therefore bears many promises. [8,9]

References

[1] The Future of Energy Supply: Challenges and Opportunities. N. Armaroli, V. Balzani, Angew. Chem. Int. Ed.
46, 2007, 52.
[2] Excitation energy transfer in multiporphyrin arrays with cyclic architectures: towards artificial light-harvesting antenna complexes. J. Yang, M.-C. Yoon, H. Yoo, P. Kim, D. Kim. Chem. Soc. Rev. 41, 2012, 4808.
[3] Dye-Loaded Zeolite L Sandwiches as Artificial Antenna Systems for Light Transport. M. Pauchard, A. Devaux,
G. Calzaferri, Chem. Eur. J. 6, 2000, 3456.
[4] Time- and Space-Resolved Luminescence of a Photonic Dye-Zeolite Antenna. M. Pauchard, S. Huber, R. Méallet-Renault, H. Maas, R. Pansu, Calzaferri, Angew. Chem. Int. Ed. 40, 2001, 2839.
[5] Trapping Energy from and Injecting Energy into Dye-Zeolite Nanoantennae. H. Maas, G. Calzaferri, Angew. Chem. Int. Edition, 41, 2002, 2284.
[6] Nanochannels: Hosts for the Supramolecular Organization of Molecules and Complexes. G. Calzaferri, Langmuir 28, 2012, 6216.
[7] Synthesis, Properties, and Composite Materials. P. Cao, O. Khorev, A. Devaux, L. Sägesser, A. Kunzmann, A. Ecker, R. Häner, D. Brühwiler, G. Calzaferri, P. Belser, Chem. Eur. J. 22, 2016, 4046.
[8] Supramolecular Organization in Confined Nanospaces. G. Tabacchi, ChemPhysChem 19, 2018, 1249.
[9] Mesoscopic FRET Antenna Materials by Self-Assembling Iridium(III) Complexes and BODIPY Dyes. A. J. Bagnall, M. Santana Vega, J. Martinelli, K. Djanashvili, F. Cucinotta, Chem. Eur. J. 24, 2018, 11992.