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Reversible tunability of the near-infrared valence band plasmon resonance in Cu2- xSe nanocrystals

: Dorfs, D.; Härtling, T.; Miszta, K.; Bigall, N.C.; Kim, M.R.; Genovese, A.; Falqui, A.; Povia, M.; Manna, L.


Journal of the American Chemical Society 133 (2011), No.29, pp.11175-11180
ISSN: 0002-7863
ISSN: 1520-5126
Journal Article
Fraunhofer IZFP, Institutsteil Dresden ( IKTS-MD) ()

We demonstrate that colloidal Cu2 - xSe nanocrystals exhibit a well-defined infrared absorption band due to the excitation of positive charge carrier oscillations (i.e., a valence band plasmon mode), which can be tuned reversibly in width and position by varying the copper stoichiometry. The value of x could be incrementally varied from 0 (no plasmon absorption, then a broad peak at 1700 nm) to 0.4 (narrow plasmon band at 1100 nm) by oxidizing Cu 2Se nanocrystals (upon exposure either to oxygen or to a Ce(IV) complex), and it could be incrementally restored back to zero by the addition of a Cu(I) complex. The experimentally observed plasmonic behavior is in good agreement with calculations based on the electrostatic approximation.