Nanocrystalline Ag-doped ZnO powders were synthesized directly from an aqueous solution of zinc acetate dihydrate and silver nitrate in the presence of poly(ethylene oxide)-b-poly(propylene oxide). (PEO)(19)-b-(PPO)(3). and sodium hydroxide at 70 degrees C. The ZnO powders had an urchin-like shape without any dopant and this turned to an agglomerated rod-like structure when the Ag loading was less than or equal to 0.5 mol%. lithe Ag content was further increased, the urchin-like shape reappeared. This may occur because the Ag aggregates at the grain boundary. The finding that the diameter of the urchin-like shape decreases as the Ag concentrations increase, can be explained by the pinning effect of the Ag particles as obstacles that inhibit the grain migration and grain growth. An increase of the photocatalytic efficiency for degrading methylene blue increases with the Ag loading up to 1.0 mol% while the best of the antibacterial activity against Staphylococcus aureus was found at 0.5-0.8 mol% of Ag. However, the different Ag loadings in the ZnO powders had no effect on the antibacterial effect on Escherichia coli. (C) 2011 Elsevier B.V. All rights reserved.