14862
Two main barriers to its widespread use are the lack of ( 1 ) fabrication protocols leading to tailored functionalization of the graphene sheet with oxygen - containing chemical groups , and ( 2 ) understanding of the impact of such functional groups on the stability and on the optical and electronic properties of rGO .
 Chemical: graphene; Chemical: oxygen; Chemical: rGO
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; Chemical: oxygen; Chemical: rGO