19785
Moreover , the initial accumulation of chlorine radicals is considered as the rate - determining step of photochlorination of graphene .
 Chemical: chlorine; Chemical: graphene
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: chlorine; Chemical: graphene