26792
In contrast , for a commonly used polarity probe pyrene , the ratio of I3 / I1 varies only from ~ 0 . 6 to ~ 1 . 7 , where I3 and I1 stand for the intensities of the fluorescence emission at peak 3 and peak 1 , respectively .
 Chemical: pyrene
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: pyrene