Reversible Tunability of the Near-Infrared Valence Band Plasmon Resonance in Cu_(2-x)Se Nanocrystals

摘要

We demonstrate that colloidal Cu_(2-x)Se 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 ran) to 0.4 (narrow plasmon band at 1100 nm) by oxidizing Cu2Se nanocrystals (upon exposure either to oxygen or to a Ce(1V) 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.