prepare Hg doped ZnO, zinc acetate dihydrate andmercury acetate (0.1,
0.3 and 0.5 weight ratios) were mixed and grounded for 3 h. Thermal
analysis results of (Hg (0.5)/Zn (99.5))mixed acetate sample are similar
to that of the results obtained for pure zinc acetate dehydrate.
2.1. Characterization details
The crystalline structure of Hg doped ZnO was confirmed using
X-ray diffraction (XRD) analysis, which was done by Rich Siefert
3000 diffractometer using Cu Kα1 radiation (λ=0.15405 nm) with
Ni filter. Philips CM20 transmission electron microscope (TEM) was
used to study the shape and size of the nanorods. Samples for TEM
studies were nanorods dispersed in ethanol on a carbon-coated copper
grid and the solvent was evaporated at room temperature. The
band gap values were calculated from UV–Vis absorption spectra,
obtained on a CARY 5E UV–Vis–NIR Spectrophotometer. The morphology
and chemical composition of the samples were examined by field
emission scanning electron Microscopy (FE-SEM) and Energy Dispersive
X-ray Spectroscopy analysis using HITACHI-SU6600 instrument.
FT-IR spectrum was taken using a Bruker-Tensor 27 Fourier Transform
Infra Red spectrophotometer and the photocatalytic activity was measured
by Perkin-Elmer UV–visible spectrometer RX1.
2.2. Measurement of photocatalytic activity
The photocatalytic decomposition of MB and MO dyes using Hg
doped ZnO catalyst was done by visible light irradiation. The photoreaction
was carried out in a photoreactor with a projection lamp (7748XHP
250 W, Philips, 532 nm) on the light source. The UV light from the
source was filtered using an acetone jacket. Reaction suspensions were
prepared by adding the 500 mg catalyst into 500 ml of 3×10−5mol/l
MB and MO solution. The aqueous suspension containing MB/MO and
the photocatalyst were irradiated under constant stirring. The analytical
samples from the suspension were collected at regular intervals of time,
centrifuged and filtered. The concentration ofMB andMOin each sample
was analyzed using UV–visible spectrophotometer at a wavelength of
664 and 464 nm respectively. The photocatalytic efficiency is calculated
from the expression
η ¼ ð1−C=C0
Þ 100 ð1Þ
where C0 is the concentration of MB or MO before illumination and C
is the concentration after a certain irradiation time.