18534
Here we report a new method for synthesizing high optical quality monolayer MoS2 single crystals up to 25 mu m in size on a variety of standard insulating substrates ( SiO2 , sapphire , and glass ) using a catalyst - free vapor - solid growth mechanism .
 Chemical: MoS2; Chemical: SiO2; Chemical: sapphire
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: MoS2; Chemical: SiO2; Chemical: sapphire