20336
However , a significant problem in this field is the unexplained abnormally low fluorescence brightness ( or number of fluorescence photons detected per one excitation photon ) exhibited by most of CP single chains in solid polymer hosts .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None