21342
Designed as a high - capacity alloy host for Na - ion chemistry , a forest of Sn nanorods with a unique core - shell structure was synthesized on viral scaffolds , which were genetically engineered to ensure a nearly vertical alignment upon self - assembly onto a metal substrate .
 Chemical: Na; Chemical: Sn
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: Na; Chemical: Sn