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The structure of hydrated Co ions confined in the nanospace of single - walled carbon nanotubes ( SWNTs ) has been studied using the X - ray absorption fine structure ( XAFS ) technique .
 Chemical: Co; Chemical: carbon
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: Co; Chemical: carbon