18259
Its excellent mechanical performance results from a brick - and - mortar like architecture , which combines strong covalent bonding within the single - crystalline nanofibers with an intricate hydrogen bonding network between them .
 Chemical: hydrogen
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