Synthesis of metal-oxide nanotubes by using template-directed growth in conjunction with the sol-gel process and a spin-coating technique

We present a systematic analysis of the nanotube-synthesis method of template-directed growth in conjunction with the sol-gel process and a spin-coating technique (TSS). Advantages and disadvantages of the TSS method are described. The method is a simple, highly reproducible, and time-saving method to prepare multi-functional complex metal-oxide nanotubes with high aspect-ratios. However, the method still has delicate problems to be solved: the low-solid content of the sol-gel precursor solution, the interaction between the surfaces of the pore walls of the porous alumina template (PAT) and the sol particles, and the unwanted interaction between the PAT and the deposited sol-gel solution. Precise control of the experimental parameters, such as the pH of the precursor solution, the volume of the drop during the spin-coating process, the spinning speed, and the spinning time, is needed.