6555
Using a combination of high - resolution scanning tunneling microscopy and first - principles calculations , we have determined the exact atomic structure of plasma - etched GNR edges and established the chemical nature of terminating functional groups for zigzag , armchair , and chiral edge orientations .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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