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The chemical structure and electronic properties of two - dimensional ( 2D ) carbon - supported TiO 2 , TiO 2 - graphdiyne , and TiO 2 - graphene composites have been studied by first - principles density functional theory .
 Chemical: carbon; Chemical: TiO 2; Chemical: TiO 2 - graphdiyne; Chemical: TiO 2 - graphene
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: carbon; Chemical: TiO 2; Chemical: TiO 2 - graphdiyne; Chemical: TiO 2 - graphene