21177
Hydrogen production tests confirmed the improved catalytic activity of CdSe / CdS dimers , which was enhanced 3 - 4 times upon etching treatment .
 Chemical: Hydrogen; Chemical: CdSe; Chemical: CdS
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: Hydrogen; Chemical: CdSe; Chemical: CdS