Spectral characteristics of CdS quantum dots and their associates with dye molecules dispersed in gelatin

Original approaches to the production of semiconductor quantum dots (QD) and their associates with dye molecules are currently being developed [1-3]. These matters are urgent from the standpoint of a wide range of applications in contemporary nanophotonics. Here most of the methods of high-temperature colloidal synthesis are complicated and expensive to use in comparison with, for example, the sol–gel method for the production of QDs. However, procedures for the “low-temperature” sol–gel synthesis of good luminescent QDs that clearly exhibit dimensional characteristics are rarely encountered in the literature [4]. It is noted that that for QDs produced in such a way the shift of the luminescence band in relation to the absorption spectrum amounts to ~100-150 nm. The half-width of the emission band here is ~70-120 nm. The analogous parameters in the case of high-temperature colloidal synthesis amount to 15-20 and 20-30 nm respectively. These relationships arise from the fact that in the “low-temperature” synthesis the impurity centers responsible for the recombination and localization of the non-equilibrium charge carriers are not “burnt out” from the volume of the QD [4, 5]. Such objects must be considered extremely interesting models. They are important for studying a variety of photophysical and photochemical processes involving localized states in the QDs and particularly in their hybrid associates with dye molecules [6-9]. In the last case the experiments were mostly conducted in QDs located in shells formed at the concluding stage of synthesis from surfactant molecules or crystals of wide-band-gap semiconductors, which levels out the role of surface radiationless recombination. During hybrid association part of the stabilizer molecules is substituted by the molecules (J-aggregates) of the dyes. However, the direct interaction of the dyes and the QD is blocked by the presence of protecting shells.