15221
In contrast , the 4 , 4 ' - dibromobiphenyl monolayer is observed when the aqueous solution is used as a medium to carry out the grafting experiment .
 Chemical: 4 , 4 ' - dibromobiphenyl
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: 4 , 4 ' - dibromobiphenyl