We synthesized colloidal CdSe nanocrystals through solution process. Nanocrystals showed quantum confinement effects well in solution form. The CdSe nanocrystals coated on Si(1 0 0) wafers were vacuum annealed and analyzed in situ using X-ray absorption and photoelectron spectroscopy to investigate the electronic energy structure of CdSe nanocrystals. As nanocrystalline solids were annealed at high temperature, the absorption edge of Cd M level and valence band maximum of CdSe decreased as the core level binding energy of Cd 3d. In addition, a red shift with the increase of annealing temperature was also confirmed by the photoluminescence observation of CdSe nanocrystals on glass substrate. (c) 2004 Published by Elsevier B.V.