25451
Towards the preparation of nano - interface , Fe3O4 nanoparticles were synthesized by thermal co - precipitation method and structural , morphological characterizations were carried out using X - ray diffraction ( XRD ) , field emission scanning electron microscope ( FE - SEM ) and field emission transmission electron microscope ( FE - TEM ) respectively .
 Fe3O4
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Fe3O4