Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 34: Particles and clusters II

O 34.5: Talk

Thursday, March 30, 2006, 12:15–12:30, WIL A317

Optical and structural changes of embedded silver nanoparticles during photochromic transformation — •Christian Dahmen, Alexander N. Sprafke, Henning Dieker, Florian Hallermann, Matthias Wuttig, and Gero von Plessen — I. Physikalisches Institut (IA), RWTH Aachen, 52056 Aachen

Photochromic materials reversibly change their color under light illumination. We have recently reported that dc-sputter deposition can be employed to prepare a multicolor photochromic material consisting of silver nanoparticles embedded in TiO₂. The explanation for photochromism in this system is spectral hole burning in the inhomogeneously broadened particle-plasmon band, which is probably caused by photoemission of electrons from the Ag nanoparticles. In this work, we investigate how the particle-plasmon line of optically excited silver nanoparticles is modified to give rise to the photochromic effect. We find that the spectral hole is mainly due to a reduction of the plasmon extinction peak of the excited nanoparticles. From a comparison with x-ray diffraction experiments we conclude that this decrease of the extinction peak is caused by a photoinduced reduction of the mean size of the silver nanocrystals.