8141
In the case of pyridine - containing ligands , only PPCA with two N - containing rings is able to provide NP stabilization and functionalization whereas other pyridine - containing acids did now allow sufficient steric stabilization .
 Chemical: pyridine; Chemical: PPCA; Chemical: N; Chemical: pyridine
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: pyridine; Chemical: PPCA; Chemical: N; Chemical: pyridine