8039
Nanocluster size is tuned from ~ 20 to ~ 40 nm by experimentally varying the final Au nanoparticle concentration and the polymer / Au ratio , along with the charge on the initial Au nanoparticle surface .
 Chemical: Au; Chemical: Au; Chemical: Au
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: Au; Chemical: Au; Chemical: Au