ZnO nanoparticles were synthesized in a simple solution route without assistance of base, surfactant, template etc., at relatively very low temperature, by a single-step process. The growth rate was greatly controlled by the presence of water-immiscible non-polar solvent, which led to formation of almost pure ZnO nanoparticles with near UV emission. On the other hand, water-miscible polar solvent generates fully defected deep-level emissive ZnO nanoparticles, which agglomerate on standing due to the solvent homogeneity in the reaction mixture. The growth mechanism of ZnO nanoparticles is discussed based on the effect of solvent polarity and water miscibility with respect to particle growth rate. The structural information provided by XRD, Raman scattering, FE-SEM, TEM, and PL spectra confirms the validity of proposed growth mechanism for the ZnO nanoparticles. The experimental results reveal that the ZnO crystal growths are more sensitive to the mixture of solvents, which depends on the miscibility, polarity, and homogeneity of precursor in the reaction medium. ((C) 2007 Elsevier B.V. All rights reserved.