3.1.4. Fourier Transform Infra-Red Spectroscopy

The characteristic FTIR peaks for metal oxides appear in the fingerprint region of 1700 to 600 cm−<sup>1</sup> due to vibrations among the metal and other atoms (O or OH) associated with it [37]. The NaOH (RA) ZnNPs exhibited specific peaks in this region at 663.0, 815.2, 952.0, 1016 (ν<sup>1</sup> frequency), and 1624 cm−<sup>1</sup> featuring Zn-O bond deformation and stretching vibrations respectively [37]. The presence of adsorbed water molecules can be identified due to the appearance of a broad peak at 3443.0 and a sharp peak at 1103.0 cm−<sup>1</sup> which can be ascribed to stretching and deformation vibrations of the O-H bond (Figure 5). Further, the occurrence of the hydrozincite phase in the starch (RA), albumin (CA), and starch (CA) ZnNPs, the stretching vibrations of the C=O and C–O bonds in the carbonate functional group (CO<sup>3</sup> <sup>2</sup>−) can be ascribed to bands at 1360 and 1407 cm−<sup>1</sup> . The conspicuous broadband (3690 to 2975 cm−<sup>1</sup> ) was observed in starch (RA), and albumin, starch and cellulose (CA) which can be ascribed to hydroxyl (O–H) and amine (N–H) group vibrations. Similar peaks have also been reported for thiourea derived ZnNPs [26].

**Figure 5.** FT-IR cumulative spectra of the prepared ZnNPs for the mid-IR region (2000 to 650 cm−<sup>1</sup> wavenumbers) indicating variability in the occurrence of chemical functional groups.
