6544
By small - angle approximation , the shear modulus of the ZnO NR , which has a radius of 166 nm and a length of 4 mu m , is measured to be 8 . 1 +/- 1 . 9 GPa .
 Chemical: ZnO
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: ZnO