Nanocrystals of yttrium oxysulfide doped with trivalent europium has been synthesized using a two step sol-gel polymer thermolysis method employing urea formaldehyde resin in the presence of ethylene diamine tetra acetic acid as chelating agent. In this synthesis, marginal tunability in crystallite size (phi = 7-15 nm) was achieved by varying the concentration of reactants and organic precursors. In this nanocrystalline system, various luminescence transitions, in particular D-5(0) --> F-7(2) transition of Eu3+ shows moderate (similar to60%) lifetime shortening which can be explained by considering possible increase in non-radiative rate (tau(nr)) and also possible modification in optical electronegativity induced by surface states of the crystallites. (C) 2004 Elsevier B.V. All rights reserved.