Hi

TEOS and NH4OH both affect heterogeneous growth almost equally. Speed is more important than concentration. Slower speeds yield higher growth on FTO. Usually, the rods' growth requires a passivating polymer (PVP, PVA etc). In the presence of polymers the growth is not dense enough. The best way to achieve a denser growth is to use the seeded growth method, i.e. first coat the silica nuclei/extremely small particles on FTO. Then sinter them on 200+ degrees for their conformal attachment on FTO. Use this modified FTO for the heterogeneous growth. The previously attached silica particles will serve as seeds/center for the growth of silica rods. For a better quality of rods, lower concentration of reactants and longer reaction time (24 - 48 + hours)are preferred.

Best Regards.

Then, should I consider only controlling the concentration of reagents or speed to increase the density without seeds?

If you are not using any polymer for passivation then you can vary the concentration/speed only. However, if there is any polymer then seeded growth is the only solution.

Thank you for your answer. then if I use pvp as a polymer, is seeded growth the only way to make growth dense?

in my case also it was in PVP, so the growth was not dense. the hydrophilic treatment of FTO with UV or UV ozone or plasma treatment help the denser growth. however, still it is not dense enough as compared to seeded growth. I think you can try with seeded growth method, that will give you better results.

I'm also considering the treatment of substrates.

Considering other variables such as temperature, concentration, growth time, etc., I think substrate treatments will be effective in increasing density(of course its effect is not so powerful compared to seeded growth), can I take it that way?

for better results, i need to try with seeded growth method. thanks!

TEOS and NH4OH both affect heterogeneous growth almost equally. Speed is more important than concentration. Slower speeds yield higher growth on FTO.

1. Can you explain more about this part?

I wonder why the speed of TEOS decreases, the higher growth is showed.

2. You said that Slower speeds yield higher growth on FTO.

Then is it right that you 're talking about the length of the nanorod? Is TEOS related to the density of nanorods?

Thank you:)