In this work, a simple, effective and reproducible synthetic route (single-pot (SP) approach) for the preparation of high quality core-shell CdSe-ZnSe quantum dots without the use of any pyrophoric organometallic precursors is presented and their properties are compared with those prepared by the conventional double-pot (DP) approach. Effective surface passivation of stoichiometric, monodispersed, small-sized (similar to 5 nm) CdSe nanocrystallites is achieved by coating them with a ZnSe shell by single-pot approach. The resulting core-shell nanocrystallites exhibit high quantum yield values similar to 11.33%, narrow line-width of the PL band, stable surface-bonds configuration and superior structural properties at lower Zn content (similar to 10 at.%). With increasing Zn content (>= 20 at.%), a composition-tunable emission across the visible spectrum has been demonstrated by a systematic blue-shift in emission wavelength due to the formation of ternary ZnxCd1-x Se quantum dots with acceptable luminescence properties. Here, contribution to emission process from surface states of nanocrystallites increases with zinc content. The core-shell and ternary QD's formed by different routes are modeled, based on the observations of several complimentary techniques (XPS depth-profiling, PL, UV-VIS absorbance, TEM/SAED). The improved properties of core-shell CdSe-ZnSe quantum dots with similar zinc content using single-pot synthesis approach as compared to the corresponding samples obtained by double-pot synthesis, is due to better-passivation effect rendered by thin ZnSe-shell in the SP approach. Their strong luminescence, narrow emission bands and wide colour-tunability makes such quantum dot structures attractive for various scientific and commercial applications.(C) 2010 Elsevier B.V. All rights reserved.