23049
We developed an etching - free ozone treatment method to continuously tune the electrical resistance and optical transmittance of graphene films by simply varying the time and temperature of graphene exposure to ozone .
 Chemical: ozone; Chemical: graphene; Chemical: graphene; Chemical: ozone
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: ozone; Chemical: graphene; Chemical: graphene; Chemical: ozone