16213
Uncharged ( polyethylene glycol ; PEG ) , positively charged ( amino - terminated : NH2 ) and negatively charged ( carboxyl - modified ; COOH ) cadmium selenide / zinc sulfide quantum dots were used to monitor ingestion , uptake and depuration of nanometals in Daphnia magna and Ceriodaphnia dubia over 24h of exposure .
 Chemical: polyethylene glycol; Chemical: PEG; Chemical: amino; Chemical: NH2; Chemical: carboxyl; Chemical: COOH; Chemical: cadmium selenide; Chemical: zinc sulfide
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: polyethylene glycol; Chemical: PEG; Chemical: amino; Chemical: NH2; Chemical: carboxyl; Chemical: COOH; Chemical: cadmium selenide; Chemical: zinc sulfide