Aug 09, 2012 |
Charge separation in silver clusters
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(Nanowerk News) Center for Nanoscale Materials (CNM) users from the Ecole Polytechnique Federale de Lausanne in Switzerland, working with the CNM Nanophotonics Group, have demonstrated the existence of long-lived charge-separated states in silver clusters ("Long-Lived Charge-Separated States in Ligand-Stabilized Silver Clusters"). The clusters, synthesized chemically in solution, consist of exactly 44 silver atoms and are stabilized by exactly 30 organic molecules.
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Artist’s rendering of silver clusters capped with organic ligand molecules.
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Thus, the clusters exist at the boundary between the quantum-mechanical regime of small molecules and the classical regime of metal nanoparticles. Time-resolved optical measurements carried out at the CNM established that absorption of a photon by a cluster is followed very quickly — within a few picoseconds — by the separation of positive and negative charges within the cluster. The charges remain separated for a long time, as much as 300 nanoseconds.
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The stable charge-separated state, together with the fact that the clusters absorb light over a wide range of wavelengths, mean that the clusters represent a new and promising class of materials for solar energy applications.
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