19481
The resulting nanosheets , having =~ 2 nm thickness and N / C atomic ratio of 1 . 31 , show an optical bandgap of 2 . 65 eV .
 N, C
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 N, C