27596
Structural observations of the transition of TiO 2 nanopores into nanotubes by increasing the OH ( - ) concentration in the electrolyte challenge the validity of existing formation mechanisms of anodic TiO 2 nanotubes .
 Chemical: TiO 2; Chemical: OH ( - ); Chemical: TiO 2
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: TiO 2; Chemical: OH ( - ); Chemical: TiO 2