Fig. 3

FTIR spectrum of A ZnO NPs, B trisodium citrate, C Fe₃O₄ NPs, and D magnetic composite NPs (MCPs) from 4000 to 300 cm⁻¹. Characteristic peaks of metal oxide were observed at 410 and 545 cm⁻¹ corresponding to vibrational mode of Zn–O and Fe–O bonds, respectively. Peaks corresponding to 1200–1600 cm⁻¹ in ZnO NPs are of symmetric and asymmetric stretching of COO⁻ bond. These significant peaks of both ZnO and Fe₃O₄ NPs are also observed in MCPs signifying successful conjugation