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The mortar thickness can be precisely tuned from 2 . 01 to 3 . 31 nm by the weight feed ratio of PVA to graphene , as demonstrated by both atomic force microscopy and X - ray diffraction measurements .
 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