Charge carrier dynamics in colloidal semiconductors
Charge carriers on colloidal semiconductors were characterized by their optical absorption spectra. They were produced in a laser flash or by means of pulse radiolysis whereby the reactions of these charge carriers could be followed. In a biphotonic process, hydrated electrons were formed from CdS. After covering the surface with Cd[OH]2, the fluorescence of the particles appeared at the band edge with a quantum yield of more than 0.5 and the photochemical stability was enhanced by several orders of magnitude to become comparable to that of fluorescence dyes, like rhodamine. Colloids of CdS or Cd3P2 could be attached to TiO2 or ZnO, respectively. In these sandwich colloids an electron transfer occurred from the exicited CdS or Cd3P2 to the TiO2 or ZnO part, whereas the positive holes remained in the excited part of the sandwich.
Key wordsPhotochemistry colloidal semiconductors charge carriers surface modification sandwich-colloid
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