micrograph is shown in Fig. 5(c). The particle distribution curve represents
the average size of these nanorods which are about 45 nm.
3.4. FTIR analysis
In the FTIR spectra shown in Fig. 6 the broad absorption band at
~3428 cm−1 corresponds to the OH stretching vibrations of water
present in ZnO and the other absorbance band at ~2923 cm−1 is
assigned to a residual organic component. The band at ~1645 cm−1
can be associated with the bending vibrations of H2O molecules. The
absorption bands at ~1570 cm−1 and ~1412 cm−1 in both the samples
are due to the carbonyl groups of the carboxylate ions which
might remain adsorbed on the surface of ZnO. The stretching of ZnO
bond appears at 546 cm−1. This helps in explaining the chemical
bonds and also confirms the rod shaped ZnO particles. This can be
proved from the literature values of the IR spectra in the range
680–300 cm−1 for ZnO. M. A. Verges et al. and M. Bitenc et al. have
explained the shape of ZnO using FT-IR [33,34]. Fig. 6(b), (c) & (d)
show the FT-IR spectra of Hg doped ZnO which are almost similar to
that of the ZnO nanorods. The vibration mode at wave number
546 cm−1 changes slightly, because of ionic radii mismatch between
Hg2+ and Zn2+ ion [32].
3.5. Absorption properties
The optical band gap of ZnO and Hg doped ZnO nanorods were
determined by room temperature UV–Vis absorption spectrum which
are shown in Fig. 7. It is clearly observed that the absorptionwavelength
range of Hg doped ZnO is wider and has extended into the red region
when compared to ZnO. The band gap values of ZnO and Hg doped
ZnO (0.1, 0.3, and 0.5) are ~3.20 eV, ~3.10 eV, ~3.02 and ~2.80 eV
respectively. The narrower band gap allows the electron transfer from
valence band to the conduction band easily thus indicating that the
photocatalytic efficiency of Hg doped ZnO nanorods will be higher
than that of the ZnO nanorods.