2967
Hierarchical rutile TiO2 flower cluster - based high efficiency dye - sensitized solar cells via direct hydrothermal growth on conducting substrates .
 Chemical: TiO2
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: TiO2