Figure 7. FTIR spectra of as-synthesized TZO, TZO300 and TZO600 samples in the wavenumber range of 4000–400 cm⁻¹.

The broad absorptions at about 3352 and 1639 cm⁻¹ are assigned to the hydroxyl groups of chemisorbed and/or physisorbed H₂O molecules on the samples. A strong absorption band near 540 cm⁻¹ reveals the vibration properties of ZnO NRs. Other unsigned peaks are attributed to remnant organic species in the samples.