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Such a monolithic graphene pattern shows low optical contrast , a clean and more hydrophilic surface , indicating the promising use of ozone treatment to achieve high - performance graphene - based optoelectronic devices .
 Chemical: graphene; Chemical: ozone; Chemical: 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: graphene; Chemical: ozone; Chemical: graphene