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Additionally , weakly coupled Au - Ag heterodimers generated strong second harmonic signals which were invisible in the Au - Au homodimers .
 Chemical: Au - Ag; Chemical: Au - 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 - Ag; Chemical: Au - Au