Optimization, Yield Studies and Morphology of WO3Nano-Wires Synthesized by Laser Pyrolysis in C2H2and O2Ambients—Validation of a New Growth Mechanism
1 CSIR, National Centre for Nano-Structured Materials, P.O. Box 395, Pretoria, 0001, South Africa
2 School of Physics, University of the Witwatersrand, Private Bag 3, P.O. Wits 2050, Johannesburg, South Africa
3 Department of Physics and Biochemical Sciences, University of Malawi, The Polytechnic, Chichiri, Private Bag 303, Blantyre, 0003, Malawi
4 CSIR National Laser Centre, P.O. Box 395, Pretoria, 0001, South Africa
5 School of Physics, University of Kwazulu-Natal, Private Bag X54001, Durban, 4000, South Africa
Nanoscale Research Letters 2008, 3:372-380 doi:10.1007/s11671-008-9169-6Published: 25 September 2008
Laser pyrolysis has been used to synthesize WO3nanostructures. Spherical nano-particles were obtained when acetylene was used to carry the precursor droplet, whereas thin films were obtained at high flow-rates of oxygen carrier gas. In both environments WO3nano-wires appear only after thermal annealing of the as-deposited powders and films. Samples produced under oxygen carrier gas in the laser pyrolysis system gave a higher yield of WO3nano-wires after annealing than the samples which were run under acetylene carrier gas. Alongside the targeted nano-wires, the acetylene-ran samples showed trace amounts of multi-walled carbon nano-tubes; such carbon nano-tubes are not seen in the oxygen-processed WO3nano-wires. The solid–vapour–solid (SVS) mechanism [B. Mwakikunga et al., J. Nanosci. Nanotechnol., 2008] was found to be the possible mechanism that explains the manner of growth of the nano-wires. This model, based on the theory from basic statistical mechanics has herein been validated by length-diameter data for the produced WO3nano-wires.