Actually i made this TNTs a couple of years before but this time its not though i used the same electrolytes before.I think the electrolytes i am using have higher resistance because i observe very little bubbles on counter electrode.
Electrolytes i am using are
1.Ethylene Glycol ((anhydrous, 99.8%, Sigma Aldrich)
2.Ammonium fluoride (NH4F) ( (98% + ACS reagent, Sigma Aldrich))
3. D.I water
After anodization i do annealing...
Less bubbling with the new electrolyte than that you observed before indicates that the water content of your electrolyte is low. Higher the water content say > 2wt%, faster the NT growth kinetics. There are so many papers and reviews available on this topic.
When you are adding water you do not have to have anhydrous ethylene glycol (EG). Pay attention to water content of the electrolyte. The purity of titanium foil also play a significant role in determining the quality and electrical properties of the TiO2 nanotubes. Impurities such as iron, silicon, manganese etc. that are inherently present in the Ti substrate may be incorporated in the TiO2 nanotubes as unintentional dopants and affect the semiconducting properties. If these elements dissolve out during anodization, then the quality of the nanotubes could be affected.
Typically we use electrolytes with 2 -5 wt% NH4F and 2 - 5 wt% water in EG, 20 - 60 V, 3 -10 h anodization time and get desired results.
Annealing in reducing or non-oxidizing atmospheres could introduce carbon from EG as band gap states in the TiO2 which improves the electrical conductivity and photo activity.
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