7078
Strong photoluminescence , a current on / off ratio exceeding 10 ( 8 ) in field - effect transistors , and efficient valley and spin control by optical helicity have recently been demonstrated in this material .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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