8907
X - ray diffraction ( XRD ) and transmission electron microscopy ( TEM ) measurements have shown that fullerene flowers have a hexagonal structure with cell dimensions of a = 2 . 539 nm and c = 1 . 021 nm , which differ from that of pristine C ( 60 ) .
 Chemical: fullerene; Chemical: C ( 60 )
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: fullerene; Chemical: C ( 60 )