I think that you will see many publications on making vertical nano-tubes of TiO2 and of ZnO as well.

Dear Sir,

I have gone through many publications as you said and also prepared through hydrothermal method at 150C for 48 h. I have taken SEM images in that tube morphology was not appreciable even in FESEM also but there is no particle shape. It seems to be about to get tube morphology. Here I am attaching SEM please go through it and make a comment on it. But in case of TEM tube morphology was clearly observed.

_Thanks,

Chandrasekhar.

Are you using a seed layer? In growing rutile TiO2 nanowires, I found that having a high-quality dip-coated TiO2 seed layer was key to getting good wires. Starting with a very clean reaction vessel is also important, to prevent junk crystals from nucleating on whatever impurities are floating around and precipitating onto your substrate.

I am not using seed layer.

Could you please tell me how to use it?

I will be looking for your reply.

I used to use the growth method in DOI: 10.1021/nl802096a which lists an aqueous TiCl4 soak + anneal. This yields a very thin layer. We had better luck in uniformity forming the seed layer by dip-coating in a TiO2 sol gel made following DOI: 10.1002/adma.200501825, made by heating 10 ml of titanium isopropoxide in a mixture of 50 ml 2-methoxyethanol and 5 ml ethanolamine under argon. We then followed the rest of the growth recipe from above. The dip-coated layer has the problem that the TiO2 is a bit lower quality, it has defects which must be filled by light soaking with UV. However, it provides better surface coverage so crystal growth is more uniform.

The growth method I mention is for rutile wires, though anatase is much better for DSSCs. I havent kept up with the literature though on a good recipe for anatase wires