17920
Incorporation of TiO2 nanowires yields a six - fold increase in the electron mobility relative to unmodified devices , leading to a 19 % improvement in the power conversion efficiency .
 Chemical: TiO2
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: TiO2 
Answer:
 Chemical: TiO2