The hexagonal bi-pillar structures of undoped and sulfur-doped ZnO particles have been synthesized by hydrothermal method to study the relationship between UV and long wavelength emissions, green emission (GE) and orange emission (OE) bands. A room temperature photoluminescence comparison between undoped and sulfur-doped ZnO shows an increase of long wavelength emission, that is presumably due to an increase of defects in doped ZnO. Spatial cathode luminescence (CL) analysis on a single ZnO particle shows a competitive behavior between GE and OE bands. The long wavelength emissions in ZnO are all related to Zn vacancies. GE will dominate if the Zn vacancy-related oxygen stays at lattice point; otherwise OE will dominate if this oxygen atom leaves lattice point to form a interstitial atom. (c) 2013 Elsevier B.V. All rights reserved.