Size-dependent two-photon excitation spectroscopy of CdSe nanocrystals

Abstract
Two-photon excitation spectra of highly monodisperse colloidal CdSe nanocrystals with sizes ranging from 22 to 43 Å are compared to one-photon excitation data and to a spherically confined effective-mass model. The main experimental features are well described by this model. However, the first one-photon and two-photon transitions appear indistinguishable, though the model predicts a 20-meV splitting. This discrepancy may reflect the sensitivity of the band-edge structure to deviations from the assumed spherical symmetry. © 1996 The American Physical Society.