Synthesis of CdSe colloidal quantum dots and quantum transitions under action of low power optical excitation

CdSe colloidal quantum dots were synthesized at low temperature (80-85 0C) on the basis of chemical reactions in colloidal solutions using trioctylphosphine (TOP), pure Se, oleic acid and cadmium acetate Cd(CH3COO)2. The average size of the synthesized nanocrystals is 2.04 nm, that is less then exciton Bohr radius in the bulk material, which is equal to 5.6 nm. Therefore in such QDs the electron with spin ? and the hole with total angular momentum 3/2 are in localized or slightly delocalized states. In absorption spectra in the UV-VIS range the lines corresponding to quantum transitions between hole state 1S3/2(h), 2S3/2(h), 1P3/2(h) and electron state 1S1/2(e), 1P1/2 (1S3/2(h)→1S1/2(e), 2S3/2(h)→1S1/2(e) and 1P3/2(h) →1P1/2(e)) are detected. The location of photoluminescence maxima of QDs in hexane and in powder state coincide in the limits of experimental errors (570 and 568 nm, respectively). In photoluminescence spectra of powder QDs a broad long-wavelength band of low intensity with maximum at 570 nm was detected. (authors)