CdSe nanocrystals (NCs) were obtained from cadmium sulfate and sodium selenosulfate in aqueous gelatin solutions. A near-bandgap emission of CdSe NCs was noticeably enhanced after passivation with CdS or ZnS. Resonant Raman scattering spectra of the passivated NCs revealed new peaks attributed to the formation of the sulfide shells around CdSe cores. The peaks observed for the CdSe/CdS core-shell NCs near 280 cm −1 were attributed to LO vibrations within a thin CdS passivating layer. Observation of the peak in the same frequency range for CdSe/ZnS is discussed within an assumption of alloying at the core-shell interface. Notable changes in the Raman spectra at different excitation wavelengths and shell parameters were attributed to the resonant and size-selective nature of the Raman process.

The results of a resonant Raman scattering (RRS) study of polymer-stabilized colloidal CdSe nanoparticles (NPs) are reported. The size-selective nature of the RRS is demonstrated by analysing the NP ensembles with different average size [Formula: see text] and size distribution Δd using a set of excitation wavelengths. The effect of size selection on the estimation of [Formula: see text] and Δd values from the RRS spectra is discussed, as well as some peculiarities of RRS on surface optical phonons. From the experimentally observed small variation of the I(2LO)/I(LO) ratio for 2-5 nm NPs a minor effect of [Formula: see text] on the electron-phonon coupling strength in this [Formula: see text] range is supposed.

The effect of shells of various thicknesses on the vibrational resonant Raman spectra of CdSe/ZnS core-shell nanoparticles is studied. The dependence of the core-shell structure on the method of shell deposition is derived from a comparison of the vibrational and photoluminescence spectra of nanoparticles. Along with the appearance of peaks attributed to the shell, the phonon spectrum of the core undergoes significant changes upon shell growth. The change of the CdSe LO peak lineshape in core-shell nanoparticles is discussed with respect to possible changes in the spectrum of both optical and acoustical phonons upon shell formation. Based on the observed decrease of the CdSe 2LO/LO peak intensity ratio, a weakening of exciton coupling to the CdSe LO phonon upon ZnS shell deposition is supposed. The change in the carrier localization volumes upon shell formation is discussed as a possible reason for the reduced coupling.

CdSe nanocrystals were synthesized in aqueous solutions using gelatin as a stabilizer. An appreciable improvement of photoluminescence efficiency of nanocrystal-containing polymeric films was achieved by passivation of asformed nanocrystals in solutions with CdS and ZnS. The passivation-induced variation of the photoluminescence efficiency and its maximum position was found to be dependent on the total volume of the passivating material and the sequence of the reagents involved. The photoluminescence of both unpassivated and passivated nanocrystals was noticeably (∼200 meV) red-shifted from the first absorption maxima. A possible origin of the emission observed is discussed.

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