9618
The repulsion development and conformational change of PEI with decreasing pH induce the aggregation of Ag nanoclusters , leading to an obvious color change and fluorescence quenching of Ag nanoclusters at low pH values .
 Chemical: PEI; Chemical: Ag; Chemical: Ag
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: PEI; Chemical: Ag; Chemical: Ag