The aqueous solution growth process of ZnO rods, starting from zinc hydroxide formed during the ultrasonic precipitation of zinc acetate and ammonium hydroxide has been demonstrated here. A dispersion consisting of 0.3 (w/v) % zinc hydroxide in water on heating at 80 +/- 5 degrees C for 6 h has resulted in the formation of ZnO rods having an aspect ratio between 8 and 12. We have monitored the growth of ZnO rods as a function of different reaction parameters. The as-prepared rods have also been characterized by optical and Raman spectroscopic methods in addition to other techniques. Further, we also investigated the photocatalytic degradation of methyl violet, which is a well known textile pollutant by using the as-prepared ZnO rods and found that the degradation was more effective using a 365 nm light source than using a 254nm light source. This result confirms that the as-processed ZnO rods could be used directly under sunlight for the degradation of methyl violet present in polluted water. Our experimental results, confirmed that the sample with more oxygen defects shows better photocatalytic degradation of the dye molecule due to the involvement of oxygen vacancy defects and oxygen interstitials in the charge recombination process and helps in better catalytic reaction under a UV lamp. (C) 2014 Elsevier B.V. All rights reserved.