Role of the surface polarity in governing the luminescence properties of ZnO nanoparticles synthesized by Sol-gel route

► Luminescence properties of the washed and unwashed ZnO nanoparticles are different. ► It is explained in terms of the dissimilar nature of the surface charge polarity. ► Zeta potential study shows that the intrinsic surface of ZnO nanoparticles have negative polarity. ► Hydroxyl groups are found to be the primary cause for GL emission for these ZnO nanoparticles. ► The origin for the remnant GL emission which survives the evacuation is found to be different.