Controllable growth of multi-level tower ZnO for biodiesel production

Multi-level tower ZnO with bulk quantity has been grown by a simple aqueous solution technique. Detailed structural characterization revealed that, the multi-level tower ZnO showed perfect hexagonal sectional morphology, with the length and diameter being 1-2 mu m and 200-300 nm, respectively. When multi-level tower ZnO was used as the solid base catalyst to synthesize biodiesel, a biodiesel yield of 73.5% was achieved, much higher than the 46.2% of particle-like ZnO. Preferred nucleation and growth of ZnO nuclei along [0 0 0 1] direction resulted in hexagonal rod-like ZnO, and further layer-by-layer stacking of rod-like ZnO led to multi-level tower architectures, which predominantly exposed active O(2-) on (0 0 0 2), (1 0 (1) over bar 0), (0 1 (1) over bar 0) and ((1) over bar 1 0 0) planes of ZnO, resulting in obvious enhancement of catalytic activity and high yield of biodiesel. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.