Table 1.

Fourier transform infrared spectral assignments of pure Fe₃O₄, HAp, and Fe₃O₄-HAp nanoparticles

S No	Wave number (cm−1)			Spectral assignments
	Fe3O4	HAp	Fe3O4-HAp
1	–	3,639	3,639	OH− group, CaO
2	–	3,561	3,570	Stretching mode of OH− group
3	3,420	–	3,420	H2O, OH− group
4	–	2,080	–	Phosphate group (PO43−)/absorbed CO32−
5	–	2,003	–	Phosphate group (PO43−)/absorbed CO32−
6	–	–	1,638	O-H in-plane bending
7	1,625	–	–	(H-O-H) adsorbed water
8	–	1,473	1,473	CO32−
9	1,383	–	–	N-O nitro compounds
10	1,151	–	–	C-O
11	–	–	1,091	Phosphate group (PO43−)
12	1,062	–	–	C-O
13	–	1,046	1,046	Phosphate group (PO43−)
14	–	–	960	Phosphate group (PO43−)
15	891	–	–	C-H
16	–	–	875	C-H
17	797	–	–	C-H
18	–	–	629	C-Cl
19	–	–	601	O-P-O bending
20	588	–	–	Fe-O-Fe bond (Fe ions in tetrahedral and octahedral site)
21	–	566	566	O-P-O bending

Abbreviations: Fe₃O₄, iron oxide; HAp, hydroxyapatite.