Quenching of CdS Colloids

Studies on luminescence of CdS colloids provide useful knowledge on the energy and nature of recombination sites of charge carriers in the colloidal particles. The regularities of the colloid photoluminescence quenching provide the information on the dynamics of electrons and holes in semiconductor particles as well as on the kinetics of interfacial electron transfer. Of a particular interest are studies on the luminescence of colloidal solutions of the so-called Q-semiconductors, their properties depending on the size of semiconductor particles due to the quantum size effects. 

This chapter presents results of the studies on photoluminescence spectra of CdS Q-colloids in the size range of 2R = 20-100 A as well as on the luminescence quenching of Q-CdS by various quenchers under variation of the colloidal particle sizes. 

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Fig. 2.16 displays experimental data on the luminescence quenching of CdS colloidal particles of four different size in the Stem-Folmer s coordinates. The data correspond to different luminescence bands. This figure presents also the curves approximating the experimental points to equation (2.19). From these curves, the values of the both parameters, KadS and A, may be extracted. One may see from Fig. 2.16 that the luminescence quenching of CdS by methylviologen differs for different bands and depends on the size of colloidal particles. In particular, the methylviologen adsorption constant rises as the size of the CdS colloidal particles increases. It follows from Fig. 2.17 that the obtained values of rate constant Kads decrease exponentially with an increase of the value opposite to the colloidal particle diameter. 

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