Photochemistry of Colloidal Semiconductors 10. Exclusion Chromatography and Stop Flow Experiments on the Formation of Extremely Small CdS Particles

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Abstract
A solution of Q‐CdS (particles of extremely small size, prepared by precipitation in the presence of hexametaphosphate, separated as solid, and redissolved) was fractionated by exclusion chromatography. The various fractions had absorption spectra, in which the maximum of the exciton transition is shifted to shorter wavelengths with increasing elution time. This result proves that the various absorption maxima in the spectrum of Q‐CdS are caused by particles of different size. ‐ The development of the absorption spectrum of CdS at different times after the mixing of NaSH and Cd(ClO4)2 solutions in the presence of hexametaphosphate was observed with a stop flow apparatus. As the particles grow, the beginning of absorption is shifted to longer wavelengths. Spectra with several absorption maxima are observed in a certain range of hexametaphosphate concentration. The rate and structure of size distribution are dependent on whether precipitation occurs in bulk solution or on the Cd2+ loaded metaphosphate matrix.

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