Key words
photocatalyst - iodine-doped - TiO
2
- degradation - catalytic activity
Rapid industrialization results in the increase of wastewater containing many industrial
pollutants, including textile organic compounds such as dyes, oils, detergents, cosmetics,
inks, etc. Besides others, textile pollutants exert intense ecological, health, and
aquatic problems since the biodegradation of these pollutants is quite slow. Moreover,
dyes have mutagenic and carcinogenic effects. The separation and degradation of organic
pollutants is vital to ensure a nontoxic and pollution free environment.[1] Previously, ozonation, reverse osmosis, filtration, adsorption, coagulation, etc.,
several conventional methods have been used for wastewater treatment.[2]
[3] However, due to less efficient, long operating time, high cost, pH sensitivity,
production of hazardous byproducts, environment vulnerability, etc., it is essential
to search new methods to mitigate these problems.[3,4] Currently, the degradation of organic materials through advanced oxidation has been
reported using semiconductor metal oxide nanomaterials, which increases the generation
of hydroxyl radical (•OH) in presence of UV and visible light.[3]
,
[5]
[6]
[7] Heterogeneous photocatalysis with metal oxide nanomaterials has gained attention
for the removal of toxic materials from wastes under sunlight.[8] Undoubtably, titanium dioxide (TiO2) is one of the most used and more effective nano photocatalyst for wastewater treatment,
because of its unique properties such as availability, chemical stability, nontoxicity,
low cost, good catalytic activity in presence of light at very low concentration,
and so on[9]
[10] Moreover, the excellent physicochemical properties of TiO2, ecofriendly nature, and its ability to generate innumerable electrons maintaining
its stability under light have made TiO2 a propitious material for numerous applications.[11]
[12] Besides all its advantageous properties, TiO2 has few limitations as a catalyst because of its low charge separation efficiency
(band gap –3.2 eV),[13] and/or it might be toxic for living organisms.[6]
[14] Hence it is essential to improve the catalytical activity of TiO2. Several strategies have been reported to increase the photocatalytic activity of
TiO2, such as adding/doping metals, other semiconductor-based nanomaterials and using
hole scavengers. Doping is one of the superior optimistic strategies that can alter
the conduction band (CB) and/or valence band (VB) of TiO2, and improve the light absorption possessions.[15] However, doping of non-metal with TiO2 showed better photocatalytic activities rather than metal-doped TiO2 due to strong absorption peak with a red shift for non-metal-doped TiO2 under the visible light range.[16]
[17]
[18]
[19] Several non-metal dopants, for example carbon, nitrogen, phosphorus, iodine, fluorine,
boron, sulfur, and so on, are popular to increase catalytic activity of TiO2.[12]
[20]
[21] Iodine-modified TiO2 shows a significant photocatalytic activity in the visible light region. The reduced
band gap for TiO2 is accountable to lessen the recombination of photogenerated electrons and holes.[22] The degradation of several types of dyes using different non-metal-doped TiO2 have been previously reported in the literature.[3]
[23] However, the photocatalytic activity of I-TiO2 has been rarely described for the degradation of several textile dyes like congo
red, methyl orange, nitrophenol, triethanolamine, glycerol monostearate, 2Na-EDTA,
methyl paraben, propyl paraben, and others.
In this work, the synthesis of crystalline I-TiO2 by the sol-gel method (the most versatile and common technique) at room temperature
has been described. The catalytic activities of the I-TiO2 were examined for oxidative degradation of congo red and methyl orange in presence
of UV and visible light.
X-ray Diffraction (XRD) Analysis
X-ray Diffraction (XRD) Analysis
XRD investigation was accomplished to assess phases, size, degree of crystallinity,
chemical composition as well as crystal structure of nanomaterials. Figure [1] displays the XRD patterns of synthesized nanomaterials of TiO2 and I-TiO2, which all were calcined at 450 °C. XRD patterns show the almost similar sharp peaks
of the pure tetragonal anatase phase of TiO2 that demonstrates the purity of the synthesized samples. The diffraction peaks appeared
at 2θ diffraction angle 25.47°, 36.93°, 38.00°, 48.02°, 54.44°, 62.62°, 69.49°, and
75.20° for the lattice planes (101), (103), (004), (200), (105), (204), (116), and
(215), respectively.[24] There are no characteristic peaks observed in the XRD patterns related to rutile,
brookite, iodine, or any other impurities in the samples. The average crystallite
sizes of TiO2 and I-TiO2 were calculated from the most intense anatase peak (101) with the help of Debye–Scherrer’s
equation (Equation 1).
Equation 1
Where D is the average size of the nanomaterials, k denotes the constant with the value 0.94, λ represents the wavelength of the X-ray
radiation of Cu-Kα (λ = 1.5406 Å) and β denotes the full width at half maximum, and
θ is Bragg’s diffraction angle.[25] The crystallite size was found to be 6.76, 6.96, 7.35, 6.35, 5.70 nm for bare TiO2, I-TiO2 (2%), I-TiO2 (10%), I-TiO2 (15%), and I-TiO2 (20%), respectively. The crystallite size decreases with increasing of I into the TiO2 matrix. Similar results were found in previous work.[26]
Figure 1 XRD patterns for TiO2 and I-TiO2 nanomaterials
FESEM Analysis
The morphology of surface and microstructure of both synthesized TiO2 and I-TiO2 were thoroughly examined by FESEM analysis. In Figure [2], the FESEM images depict distinct characteristics of these nanomaterials. Notably,
Figure [2](a) illustrates that particles exhibit a more pronounced agglomeration in the case
of pure TiO2 in comparison to I-TiO2 nanomaterials, as evident in Figure [2](b). The introduction of iodine into the TiO2 matrix contributes to reduction in agglomeration, reaching its minimum at 10% I doping,
followed by a slight increase at 15% I doping. All FESEM images of the synthesized
bare TiO2 and I-TiO2 nanomaterials reveal a spherical shape. However, it is crucial to note that in the
sol-gel chemical synthesis method, the microstructure, surface morphology, and crystalline
structure of both TiO2 and I-TiO2 are influenced by various parameters such as the precursor, reaction temperature,
and pH value.[27]
Figure 2 SEM image of (a) TiO2, (b) I-TiO2 (10%), and (c) I-TiO2 (15%) with magnification of 50,000× and (d) I-TiO2 (10%) with magnification of 100,000×
EDS Analysis
Figure [3] displays the EDS results for I-TiO2 (15%) nanoparticles. The EDS spectrum of I-TiO2 reveals sharp peaks corresponding to the elements titanium (Ti), oxygen (O), and
iodine (I). Specifically, the highest peak at 0.525 KeV (energy) confirms the presence
of oxygen (O), the peak at 4.508 KeV (energy) signifies titanium (Ti), and the peak
at 3.936 KeV (energy) validates the existence of iodine (I). The spectrum unequivocally
demonstrates the incorporation of iodine into the TiO2 structure, substantiating successful deposition of iodine atoms on TiO2. Moreover, it exhibits higher percentage of iodine in I-TiO2 (15%) compared to that of I-TiO2 (10%), (Table S1 in the Supporting Information).
Figure 3 EDS spectrum of I-TiO2 (15%)
FTIR Spectral Analysis
FTIR analysis is employed to find out chemical characterization of numerous functional
groups on the surface of synthesized nanomaterials. The FTIR spectra presented in
Figure [4] depicts TiO2 and I-TiO2 with varying amounts of iodine, all calcined at 400 °C. The pronounced peak observed
around 1623.5 cm–1 is attributed to the presence of hydroxyl groups from water absorbed on the catalyst’s
surface.[28] The peak at 3407.25 cm–1 evidences the presence of Ti–OH bonds and hydrogen-bonded water species. The decreasing
intensity of the peak for iodine indicates the smaller part of iodine in the composite
materials of I-TiO2 (Figure [4]). These findings contrast with previously reported results in iodine-doped composites.[6]
[29] Consequently, it can be explained that iodine as hydrophobic repels water molecules
and deposits on the surface of TiO2. The broader peaks at 3139.8 cm–1 and small peaks at 1395.34 cm–1 correspond to H–I–H stretching and bending vibrations of hydroxyl groups absorbed
on the catalyst’s surface.[30]
In the FTIR spectrum, sharp peaks at 442.6 and 849.5 cm–1 attributed the lattice vibrations of anatase O–Ti–O bonding in TiO2.[12] Additionally, the peak at 2343 cm–1 indicates the presence of asymmetric stretching of CO2 molecules.[31] Notably, this peak is slightly stronger in the undoped sample compared to the doped
sample, as CO2 formed adducts with I– ions on the surface of I-TiO2 composites.
Figure 4 FT-IR spectra of TiO2 and I-(2–20%) TiO2 nanomaterials
UV-Visible Absorption Spectral Analysis
UV-Visible Absorption Spectral Analysis
Figure [5] shows the UV-visible absorption spectra for the prepared TiO2 and I-TiO2 materials. The optical absorption spectra for I-TiO2 exhibits a stronger absorption edge in the 250–380 nm range compared to pure TiO2 confirms the insertion of iodine in composite materials.[32]
Figure 5 UV-vis absorption spectra for TiO2 and I-TiO2
The decreasing band gap energy with increasing concentration of iodine in I-TiO2 composites was confirmed by the red shift in the absorption edge. Furthermore, the
optical activity of I-TiO2 increases in the visible range with increasing iodine dopant.[33]
[34]
The band gap (Eg
) was calculated using Tauc’s relation (Equation 2).
Equation 2
Here, α is the absorption coefficient, A represents a constant, and n = 1/2 for direct
or n = 2 for indirect allowed transitions of semiconductors.[35] The value of the optical band gap (Eg
) has been calculated by extrapolating the linear region to α = 0 from the plotting
(αhν)2 against hν (Figure [6]). The calculated band gap of modified composite materials was found to be 2.277,
2.448, 2.634, 2.686, and 3.312 eV for I-TiO2 (2%), I-TiO2 (20%), I-TiO2 (15%), I-TiO2 (10%), and pure TiO2, respectively. The band gap of all I-TiO2 composites is significantly reduced compared to pure TiO2. The band gap gradually decreased with increasing amount of iodine doping from I-TiO2 (10%) to I-TiO2 (20%). However, I-TiO2 (2%) showed minimum band gap. The reduction of band gap and modification of light
absorption ability of I-TiO2 compared to pure TiO2 indicates the synergic interaction between TiO2 and doped iodine in I-TiO2.
Figure 6 Tauc plot of pure TiO2 and I-TiO2 (2–15%) photocatalysts
Photocatalytic Activity
The photocatalytic activity of prepared pure TiO2 and all I-TiO2 composite materials was inspected to degrade 100 mL of 10 ppm MO using 100 mg of
photocatalyst under the irradiation of both UV and visible light. Figure [7a] shows the photocatalytic degradation of MO using different photocatalysts under
the irradiation of UV light. The photolysis reaction of MO with UV light was also
monitored. As shown in Figure [7a] the MO was not degraded without photocatalyst with the irradiation of only UV light.
The MO was stable at UV photolysis reaction. It was also observed that only small
amounts of dye are adsorbed during the reaction using different catalysts. The 15%
I-TiO2 shows maximum photocatalytic activity.
Figure 7 (a) Photocatalytic degradation of MO using pure TiO2 and different I-TiO2 catalysts with the irradiation of UV light and (b) the corresponding plot of –ln(C/C
0) versus irradiation time
The kinetics and reaction rate of the photocatalytic degradation process has been
studied according to the Langmuir–Hinshelwood (L–H) model, which was developed by
Turchi and Ollis. The model is expressed as Equation 3.[36]
[37]
Equation 3
Where r
0 is the degradation rate on the reaction, k is the rate constant, and K and C are the adsorption equilibrium constant and reactant concentration, respectively.
If the initial concentration C
0 is very small, it can be simplified to Equation 4.[36]
[37]
Equation 4
The equation becomes a linear expression on time t with respect to –ln(C/C
0), where k
obs is reaction rate constant. The values of k
obs were calculated by plotting –ln(C/C
0) versus t (Figure [7b]). As shown in Table [1], it was observed that the degradation rate of MO by I-TiO2 (15%) with the UV light irradiation (1.114 h–1) was 6.75 times higher than that attained by pure TiO2 (0.165 h–1).
Table 1 Kinetic Parameters for Photocatalytic Degradation of MO under Irradiation of UV Light
|
Photocatalyst
|
Rate constant (h–1)
|
t
1/2 (h)
|
R2
|
|
pure TiO2
|
0.165
|
4.20
|
0.96
|
|
I-TiO2 (2%)
|
0.285
|
2.43
|
0.99
|
|
I-TiO2 (10%)
|
1.098
|
0.63
|
0.99
|
|
I-TiO2 (15%)
|
1.114
|
0.62
|
0.99
|
|
I-TiO2 (20%)
|
0.264
|
2.63
|
0.99
|
The photocatalytic degradation of MO using different photocatalysts with the irradiation
of visible light was also investigated. As shown in Figure [8a], it was observed that I-TiO2 (15%) showed maximum photocatalytic activity. The pseudo first order reaction rate
constant of MO degradation using I-TiO2 (15%) under the visible light irradiation (0.664 h–1) is 36.89 times higher than that attained using pure TiO2 (0.018 h–1) (Figure [8b] and Table [2]).
Table 2 Kinetic Parameters for Photocatalytic Degradation of MO under Irradiation of Visible
Light
|
Photocatalyst
|
Rate constant (h–1)
|
t
1/2 (h)
|
R2
|
|
pure TiO2
|
0.018
|
38.50
|
0.93
|
|
I-TiO2 (2%)
|
0.219
|
3.16
|
0.99
|
|
I-TiO2 (10%)
|
0.204
|
3.40
|
0.97
|
|
I-TiO2 (15%)
|
0.664
|
1.04
|
0.99
|
|
I-TiO2 (20%)
|
0.191
|
3.63
|
0.99
|
Figure 8 (a) Photocatalytic degradation of MO using pure TiO2 and different I-TiO2 catalysts irradiated by visible light and (b) the corresponding plot of –ln(C/C
0) versus irradiation time
I-TiO2 (15%) showed maximum photocatalytic MO degradation activity even though it
has a higher band gap compared to the band gap of I-TiO2 (2%) and I-TiO2 (20%). The slower photogenerated electron-hole pair recombination rate and higher
charge transfer of I-TiO2 (15%) would be responsible for its enhanced photocatalytic activity. However, excess
iodine in the I-TiO2 (20%) may function as electron–hole pair recombination centers and decrease photoinduced
charge separation.[38]
[39]
The photocatalytic degradation ability of I-TiO2 (15%) to degrade another textile dye CR was also compared with the pure TiO2 under UV and visible light irradiation. As shown in Figure [9] and Table [3], the pseudo first order reaction rate constant of MO degradation using I-TiO2 (15%) under UV light irradiation (0.595 h–1) is 1.82 times higher than that attained using pure TiO2 (0.327 h–1). On the other hand, the rate constant using I-TiO2 (15%) under the visible light irradiation (0.325 h–1) was about 36 times better than that attained using pure TiO2 (0.009 h–1) (Figure [10] and Table [3]).
Figure 9 (a) Photocatalytic degradation of CR using pure TiO2 and I-TiO2 (15%) catalysts with the irradiation of UV light and (b) the corresponding plot of
–ln(C/C0) versus irradiation time
Figure 10 (a) Photocatalytic degradation of CR using pure TiO2 and I-TiO2 (15%) catalysts with the irradiation of visible light and (b) the corresponding plot
of –ln(C/C
0) versus irradiation time
Table 3 Kinetic Parameters for Photocatalytic Degradation of CR
|
Photocatalyst
|
Type of irradiated light
|
Rate constant (h–1)
|
t
1/2 (h)
|
R2
|
|
pure TiO2
|
UV
|
0.327
|
2.12
|
0.99
|
|
I-TiO2 (15%)
|
UV
|
0.595
|
1.16
|
0.98
|
|
pure TiO2
|
visible
|
0.009
|
77.00
|
0.95
|
|
I-TiO2 (15%)
|
visible
|
0.325
|
2.13
|
0.97
|
In order to inspect the influence of pH on the photocatalytic degradation of textile
dye using I-TiO2 (15%), the photocatalytic degradation of CR was performed at different pH using 15%
I-TiO2 under visible light irradiation.
It has been shown that 15% I-TiO2 showed higher dye removal efficiency at near neutral pH (pH 6) (Figure [11]). A massive decline was seen when pH of the solution changes to basic or acidic.
Similar results were reported in previous works.[5]
[30] The lowering of dye removal efficiency for TiO2 indicates the agglomeration of TiO2 in acidic conditions, which may cause a reduction of the available surface area for
dye adsorption and photon absorption. Moreover, at higher pH, the rate of degradation
decreases. The catalyst surface gets negatively charged and limiting photocatalytic
degradation.[5] It has been reported that at higher pH values, OH– react with photogenerated h+ and form •OH resulting the reduction of degradation efficiency.[40]
Figure 11 Effect of pH on the rate of the degradation of CR using 15% I-TiO2 under visible light irradiation
Stability and Reusability of Catalysts
Stability and Reusability of Catalysts
The recyclability or reusability of catalyst is very important feature to determine
the stability of catalyst in practical applications.[5] The reusability as well as stability of the I-TiO2 (15%) photocatalyst on the degradation of MO under UV light irradiation was studied.
The catalyst was separated by centrifugation and reused for further degradation of
CR at same condition. The catalytic efficiency of each cycle was calculated using
Equation 5.
Equation 5
Where A
0 is the absorbance of MO dye at initial time and A
t is the absorbance of MO dye after 3.5 hours of UV irradiation in each cycle.
It was found that the catalyst is very stable for up to three cycles and degradation
ability decreased by small amount after three cycles (Figure [12]). The possible explanation for a small decrease in photocatalytic activity is the
chemisorption of CR molecules or reaction intermediate products on the active sites
of the catalyst, which remain after the saturation of accessible sites for further
reactions. The results indicate that the I-TiO2 (15%) photocatalyst can be reused on the photocatalytic degradation study.
Figure 12 Reusability of I-TiO2 (15%) in the photocatalytic degradation of MO under UV light irradiation
Evaluation of the Mineralization of Real Water Sample by Chemical Oxygen Demand (COD)
Studies
Evaluation of the Mineralization of Real Water Sample by Chemical Oxygen Demand (COD)
Studies
Chemical oxygen demand (COD) values for untreated textile effluent solutions and treated
textile effluent solutions using different catalysts under the same reaction conditions
were calculated. The percentage decline of COD values using different catalysts was
calculated using Equation 6.
Equation 6
As shown in Table [4], it was observed that the COD decrement rate of I-TiO2 increased with increasing doped amount of iodine with maximum COD decrement observed
for I-TiO2 (15%). However, the COD decrement rate slightly decreased with when doping increased
to I-TiO2 (20%).
Table 4 Decrement Rate for COD Values of Textile Effluent Using TiO2 and Different I-TiO2 composite materials.
|
Photocatalyst
|
COD removal efficacy (%)
|
|
pure TiO2
|
29.25
|
|
I-TiO2 (2%)
|
31.13
|
|
I-TiO2 (10%)
|
66.98
|
|
I-TiO2 (15%)
|
79.25
|
|
I-TiO2 (20%)
|
62.26
|
Proposed Mechanism
On the basis of literature, superoxide, hydroxyl radical and holes are participated
in the photocatalytic degradation of dyes.[5]
,
[41]
[42]
[43] The possible mechanism for the degradation of dyes using I-TiO2 under the irradiation of light is shown Figure [13].
Figure 13 Proposed mechanism of photocatalytic degradation of CR/MO using I-TiO2
In brief, under light irradiation, electrons and holes are generated in the conduction
band and valence band of the I-TiO2. Iodine may take part in slower the recombination of photogenerated electrons and
holes. Hence, photogenerated electrons and holes reacted with environmental oxygen
and water to produce superoxide (O2
•–) and hydroxyl (•OH) radicals, respectively. After that, the superoxide, hydroxyl, and photogenerated
holes react with dye solution to produce degradation products. The steps involved
in the mechanism of photocatalytic degradation of dyes using I-TiO2 are shown below and in Figure [13]
I-TiO2 + hν → I-TiO2 (e– + h+)
I-TiO2 (h+) + H2O → I-TiO2 + H+ + •OH
I-TiO2 (h+) + OH– → I-TiO2 + •OH
I-TiO2 (e–) + O2 → I-TiO2 + O2
•–
dyes + •OH/O2
•–/h+ → degraded products
Conclusions
The prepared I-TiO2 composite materials were formed using the simple sol-gel method at room temperature.
The crystallinity and the morphology of the prepared I-TiO2 samples was analyzed using XRD and SEM. UV-visible measurements showed the tuning
of the optical band gap of I-TiO2 with significant reduction in the optical band gap of I-TiO2 composites compared to pure TiO2. I-TiO2 (15%) showed better catalytic activity for the degradation reaction of the aforementioned
dyes, MO, and CR. The reusability test indicated the I-TiO2 (15%) was photostable for three catalytic cycles. The presence of iodine in the prepared
different I-TiO2 composite materials is responsible for the advancement of the catalytic activity
for the degradation reaction.
Materials and Methods
Tetrabutyl titanate (C16H36O4Ti), iodic acid (HIO3), and EtOH were purchased from Sigma Aldrich. HNO3, NaOH, congo red, and methyl orange were obtained from Merck, Germany. These chemicals
and reagents are of analytical grade of purity and used without further treatment.
Synthesis of Pure and I-Doped TiO2
Synthesis of Pure and I-Doped TiO2
I-TiO2 were prepared by following a very simple schematic hydrolysis method where tetrabutyl
titanate (TBOT) and iodic acid were used as precursors.[28] The two solutions were prepared, one containing TBOT and another containing various
portions of iodic acid. A mixture of EtOH and HNO3 was used as a solvent to dissolve TBOT. Double distilled water was used to dissolve
iodic acid for preparation of different I-TiO2 composites with various amounts of iodine to TiO2 (2–20%). Both the solution of HIO3 and TBOT were mixed properly over a mechanical stirrer (stirring rate 950 rpm, 8
h). The resultant mixture was dried (100 °C), ground, and calcined (400 °C, 2 h).
Pure TiO2 was prepared following the same procedure without using any iodic acid solution.
Photocatalytic Activity Measurement Under UV Light
Photocatalytic Activity Measurement Under UV Light
The UV photoreactor equipped with an open Pyrex glass tube and a thermosetting jacket
(maintaining 25 °C), three fluorescent lamps (Vilber-Lourmat T-6L UV-A, 6 W, λ max = 365 nm) was used for photocatalysis under UV light. Photocatalyst (100 mg) was
used to degrade the dye solution (100 mL). The reaction mixture was kept in the dark
for 30 min to ensure the adsorption–desorption equilibrium before illumination under
UV light irradiation. The irradiation time varied from 2 to 5 h. Aliquot portions
(4 mL) of the suspensions were collected every 30 min and photocatalyst was removed
by centrifugation (Eppendorf Centrifuge 5810R, 4000 rpm, for 5 min).
Photocatalytic Activity Measurement Under Visible Light
Photocatalytic Activity Measurement Under Visible Light
Tungsten halogen lamp (200 W), filter made up of glass, quartz cylinder and fan (for
cooling) were used to assemble a photoreactor for photocatalysis in presence of visible
light (λmax < 420 nm). Photocatalyst (100 mg) was used to degrade dye solution (100 mL). The
investigation was carried out at ambient temperature. The sample was kept 20 cm away
from the lamp on magnetic stirrer. To establish absorption–desorption equilibrium
the reaction mixture was kept in the dark before light irradiation at room temperature.
At regular intervals (30 min), portions of the reaction mixture (4 mL) were taken
out and centrifuged to remove the photocatalyst.
Regeneration of Used Photocatalyst
Regeneration of Used Photocatalyst
The prepared I-TiO2 (15%) composites were reused four times as catalyst for the degradation of aforementioned
dyes. To separate the catalyst the reaction mixture was centrifuged (20 min, 3000
rpm) and washed using double distilled water. The separated catalyst was dried (100
°C) and calcined (400 °C, 2 h) in a crucible.
Chemical Oxygen Demand (COD) Test
Chemical Oxygen Demand (COD) Test
In order to evaluate the mineralization ability of pure TiO2 and iodine-doped TiO2 composites, an industrial effluent containing CR and MO dyes was treated with the
photocatalyst in presence of visible light for up to 6 h. Then the COD of the untreated
and treated industrial effluents was calculated using the standard FAS method. Briefly,
the sample was refluxed with K2Cr2O7 (10 mL, 0.25 M) and H2SO4 (30 mL, 2 M). (NH4)2Fe(SO4)2·6H2O (0.25 M) was used to titrate the remaining dichromate in the sample after reflux.[44]
Characterization Techniques
Characterization Techniques
Field Emission Scanning Electron Microscope (JSM-7600F, JEOL) was employed to investigate
the surface morphology and microstructure of the fabricated samples. SEM images of
different magnification were taken by maintaining an accelerating voltage of 5 kV
and current of 10 μA. Functional groups as well as successful formation of bare TiO2 and doped TiO2 were investigated at room temperature by FTIR analysis (IRTracer, Shimadzu, Japan).
The recorded FTIR spectra with average scan of 40 in the range of wavenumber 400–4000
cm–1 of synthesized samples were performed using the KBr disk preparation method. In order
to characterize the light absorption ability of the TiO2 and doped TiO2, the absorption spectra were recorded in the range of 200–800 nm wavelengths by UV-visible
spectroscopy (UV-1800, Shimadzu, Japan). Moreover, photodegradation study was carried
out by recording the absorption spectra of MB and CR dyes by UV-visible spectroscopy
(UV-1800, Shimadzu, Japan). In order to investigate compositional and structural information
about the synthesized nanomaterials XRD analysis were performed by Rigaku smartlab
diffractometer using Cu-Kα radiation (λ = 1.5406 Å). The XRD patterns were recorded
at room temperature over the 2θ angle range from 10 to 90 with scan rate of 0.02°.
The average crystalline sizes of synthesized nanomaterials were calculated with the
help of the Scherrer formula.
