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Our experimental results further proved that TiO 2 ( 001 ) - graphdiyne composites could be a promising photocatalyst .
 Chemical: TiO 2; Chemical: graphdiyne
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: graphdiyne