By chemical co-precipitation method a series of ZnMgO nanoparticles were synthesized with the particular composition (1-x)ZnO-xMgO (where 0 <= x <= 2, all are in mol%). XRD spectra recorded at room temperature of these samples have shown the typical peaks of the ZnO hexagonal wurtzite structure, such as (1 0 0), (0 0 2), (1 0 1) etc. With the increasing concentration of MgO, the blue shift is attained in the absorption band of ZnO. Due to the Moss-Bustein effect the optical band gap has been widened by shifting towards higher frequency side as the concentration of MgO added progressively in the ZnO. The IR spectra revealed structural modifications in the stretching vibrations of Zn-O units as a function of MgO. (C) 2017 Elsevier B.V. All rights reserved.