23050
Initially , ozone exposure dramatically decreases the electrical resistance of graphene films by p - doping , but this is followed by increases in the resistance and optical transmittance as a result of surface oxidation .
 Chemical: ozone; 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: ozone; Chemical: graphene