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CHAPTER - V

PHOTOCATALYSIS OF ZnO NANORODS5.1 Introduction

Zinc oxide, with a high surface reactivity owing to a large number of native defect

sites arising from oxygen nonstoichiometry, has emerged to be an efficient photocatalyst

material compared to other metal oxides [1-3]. ZnO exhibits comparatively higher

reaction and mineralization rates [4] and can generate hydroxyl ions more efficiently than

titanium oxide (TiO2) [5]. ZnO has been often considered a valid alternative to TiO2

because of its good optoelectronic, catalytic and photochemical properties along with its

low cost. ZnO has a band gap of 3.0 eV that is lower than that of anatase. Due to the

position of the valence band of ZnO, the photo generated holes have strong enough

oxidizing power to decompose most organic compounds [6]. ZnO has been tested to

decompose aqueous solutions of several dyes [7–9], and many other environmental

pollutants [10–12]. So the ZnO has been chosen as a catalyst for this experiment for the

photocatalytic studies. In many cases, ZnO has been reported to be more efficient than

TiO2 [13–14] but the occurrence of photo corrosion and the susceptibility of ZnO to

facile dissolution at extreme pH values, have significantly limited its application in

photocatalysis.

Studies of ZnO hexagonal nanorod structure represent a significant research area,

and it is reported that one dimensional (1D) ZnO nanorods arrays could enhance

photocatalytic efficiency [15]. One dimensional nanostructure, such as nano wires and

nanorods, offer higher surface to volume ratio compared to nanoparticulate coatings on a

flat plate [16] which increase the photocatalytic efficiency. Because of the ultra-high

surface area, ZnO nanowire or nanorod arrays could potentially be a very good class of

catalyst support structures. The effective surface area (adsorbed amount of target

molecules) and the diffusivity are important indices to gauge photocatalytic activity [17].

Surface area and surface defects play an important role in the photocatalytic activity of

metal-oxide nanostructures, as the contaminant molecules need to be adsorbed on to the

photocatalytic surface for the redox reactions to occur. The higher the effective surface

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area, the higher will be the adsorption of target molecules leading to better photocatalytic

activity. ZnO nanorods, which can be strongly attached to any type of substrates through

proper surface treatment before seeding [18], are an attractive option for photocatalytic

applications. From the above findings, the ZnO nanorods have been taken as a catalyst

for the photo degradation of the textile reactive dye Methylene Blue (MB). The

performance of the reactor can also improve ZnO nanorod arrays on the inner wall of the

capillaries for forming high efficiency photocatalysis [19].

Several studies have shown that ZnO was quite active under UV illumination for

the photo degradation of some organic compounds in aqueous solution [20]. Methyl

Green was successfully decolorized and degraded by ZnO under visible light irradiation

at low watt irradiation [21] and the addition of an oxidant (H2O2) enhanced the

degradation rate of the pollutant.

Lu et al. [22] used ZnO to degrade Basic Blue 11 under visible light irradiation

and studied the effects of influential factors like initial dye concentration, catalyst dosage,

and initial pH. Sobana and Swaminathan [23] increased the photocatalytic activity of

ZnO for the solar assisted photocatalytic degradation of Direct Blue 53 by mixing ZnO

and activated carbon at different proportions in an aqueous suspension. The synergistic

effect increased the efficiency of the photocatalyst by a factor of 4.21.

ZnO nanoparticles, prepared using zinc acetate and NaOH as precipitant, were

tested for the photo degradation of Biebrich scarlet in aqueous phase [24]. The

comparison with other commercial semi-conductors (TiO2, ZnO, CdS and ZnS) indicated

that the nano sized ZnO was the best photocatalyst for the decolorization of the dye.

Sakthivel et al. [25] studied the solar photo degradation of Acid Brown 14 as the

model pollutant to evaluate the performance of both ZnO and TiO2. The photo

degradation rate was determined for each experiment and the highest values were

observed for ZnO, suggesting that it absorbs large fraction of the solar spectrum and

absorbs more light quanta than TiO2.

The degradation process was effective at pH 7 and 10, but it was rather slow at pH

4. ZnO nanoparticles prepared from zinc acetate by triethylamine template assisted sol–


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gel precipitation and further hydrothermal treatment exhibited high conversion values for

phenol photo oxidation [26].

Kislov et al. [27] showed that the photo activity and the photo stability of single

crystal ZnO samples strongly depended on the crystallographic orientation. High surface

area hexagonal ZnO nanoparticles demonstrated an enhanced photocatalytic degradation

of a tough pollutants compared with a commercial ZnO powder [28]. El-Kemary et al.

[29] synthesized ZnO nanoparticles by heating a mixture of zinc acetate dehydrate and

triethylamine in ethanol for 60 min at 50–60 ◦C. The photocatalytic activity for the

degradation of ciprofloxacin was investigated under UV light irradiation.

Kitture et al. [30] prepared polydispersed ZnO nanoparticles with two different

particle size distributions (120nm and 30 nm) that were tested for the degradation of MB

and Methelene Orange under UV irradiation. Shape and size selective ZnO nanorods with

high alignment and uniformity were grown by using a microwave-assisted chemical bath

deposition method on Indium Tin Oxide substrates [31].

The ZnO nanorods were efficient for the degradation of MB under UV irradiation

and exhibited a size-dependent activity. Hierarchically assembled porous ZnO spherical

nanoparticles showed a photo activity the degradation of phenol superior to that of TiO2

nanoparticles [32].

Li et al. [33] found that the photo reactivity of ZnO hollow spheres for the

degradation of reactive Brilliant Red X-3B increased by a factor 4.66 compared with that

of ZnO nanoparticles. Mohajerani et al. [34] synthesized ZnO nanostructures in the shape

of particle, rods, flower-like and microsphere that were tested for the decolorization of CI

Acid Red 27 under direct sunlight irradiation.

The photo activity of the ZnO nanorods was slightly superior to that of the

nanoparticles. The flower-like and microsphere 3D nanostructures showed much lower

photo activity. ZnO nano flowers were more efficient than ZnO nanorods for the

degradation of 4-chlorophenol under UV light irradiation [35].

The superior performance of the nano flowers resulted from the larger content of

oxygen vacancy on the surface of the 1D nano materials. Likewise, 3D flower-like ZnO


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hierarchical microstructures prepared by a low-temperature aqueous solution route were

more active than other nano structured ZnO powders (nanoparticles, nano sheets, and

nanorods) [36].

Doping of metal oxides with metals and / or transition metals creates quasi-stable

energy states within the band gap (surface defects) [37], thereby affecting the optical and

electronic properties [38]. Increased electron trapping due to higher defect sites leads to

enhancement in the photocatalytic efficiency. This increase in photocatalytic efficiency is

possible provided the electron-hole pair recombination rate is lower than the rate of

electron transfer to adsorbed molecules. There are reports on the enhancement of visible

light absorption in ZnO by doping with, e.g., cobalt (Co) [39], manganese (Mn) [40], lead

(Pb) and silver (Ag) [37], etc. Photocatalytic activity comparable to doped ZnO was also

observed with engineered defects in ZnO crystals achieved by fast crystallization during

synthesis of the nanoparticles [41].

5.2 Experimental technique

Fig. 5.1 Photocatalytic experimental setup

Photo catalytic activity was carried out in a specially designed reactor in which the

light source was 8W UV lamp (Philips TUV-08 G5) shown in fig. 5.1. The wavelength

range and peak wavelength were determined to 225–265nm and 254 nm, respectively,

with an average intensity of 0.2mW/cm2, at the irradiation distance of 10 cm. All samples

to be irradiated were placed in a glass beaker of 2 cm inner diameter, at a volume of 20

ml. The hydrothermally grown ZnO nanorods were used as catalyst. 0.5 mol of MB dye


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was taken in a beaker and ZnO nanorods were suspended into the beaker and treated with

UV lamp by varying irradiation time and area of catalyst. The absorption spectra were

recorded using JASCO V-570 UV-Vis spectrophotometer and rate of decolorization was

observed.

Fig. 5.2 Phillips TUV-08 G5 lamp

The UV lamp used for photocatalytic application in our study is Philips TUV-08

G5 lamp shown in fig. 5.2. Phillips is the largest manufacturer of standard low pressure

mercury lamps. These Philips TUV lamps consist of a tubular glass envelope emitting

short-wave ultraviolet (UV) radiation with a peak at 254 nm (UVC) for germicidal action.

The Philips in-house made glass filters out the 185 nm ozone forming line thus

preventing the creation of ozone. Low pressure mercury lamps are very efficient, up to

40%. A protective coating on the inside limits the depreciation of the useful UVC output.

This allows application manufacturers to design their systems to the highest efficiency.

Philips invented and pioneered the use of technology to reduce the mercury level of the

lamps. As a result this has been brought down to by far the lowest mercury level in UV

lamps in the industry. Main applications of the Philips TUV-08 G5 lamp are:

Residential drinking water units

Stand alone air purifiers

Germicidal actions.


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The measurement conditions of the Philips TUV-08 G5 lamp is given in table 5.1.

Table 5.1 Measurement conditions of Phillips TUV-08 G5 lamp

Instrument name Philips TUV-08 G5Tube diameter 16 cmArc length 237 mmLamp wattage 7 wattsLamp voltage 56 voltsLamp current 0.15 AUV C 100h 2.1 wattsmW/cm2 at 1 meter 21Depreciation 9000h 25 %Bf – Bf mm 288.3 A

The photo catalyzed decolorization of a dye in solution is initiated by the photo

excitation of the semiconductor, followed by the formation of electron–hole pair on the

surface of catalyst (Eq. 1). The high oxidative potential of the hole h+VB in the catalyst

permits the direct oxidation of the dye to reactive intermediates (Eq. 2).

(MO/MO2) + hυ → (MO/MO2) (e-CB + h-

CB) (1)

h+VB + dye → dye●+ → Oxidation of dye (2)

Another reactive intermediate which is responsible for degradation is hydroxyl

radical (OH•). It is either formed by the decomposition of water (Eq.3) or by reaction of

the hole with OH-(Eq. 4).

h+VB + H2O → H+ + ●OH (3)

h+VB + OH- → ●OH (4)

●OH + dye → degradation of the dye (5)

The hydroxyl radical is an extremely strong, non-selective oxidant (Eo = +3.06 V),

which leads to the partial or complete mineralization of several organic chemicals [9].

The photocatalytic activity of the materials was investigated by degrading an organic

pollutant MB. MB is one of the generally accepted organic pollutants for degradation

studies and is used as an industrial standard.


133

Methylene Blue (CI 52015) is a heterocyclic aromatic chemical compound with

the molecular formula C16H18N3SCl. It has many uses in a range of different fields, such

as biology and chemistry. At room temperature it appears as a solid, odorless, dark green

powder, which yields a blue solution when dissolved in water. The hydrated form has 3

molecules of water per molecule of MB [42].

MB is widely used as a redox indicator in analytical chemistry. Solutions of this

substance are blue when in an oxidizing environment, but will turn colorless if exposed to

a reducing agent. The redox properties can be seen in a classical demonstration of

chemical kinetics in general chemistry, the "blue bottle" experiment. Typically, a solution

is made of glucose (dextrose), MB, and sodium hydroxide. Upon shaking the bottle,

oxygen oxidizes methylene blue, and the solution turns blue.

In this work a model textile reactive dye methelene blue is taken for the

photocatalytic degradation using grown ZnO nanorods. The structure and the properties

of the MB dye were given in the fig.5.3 and table 5.2 respectively.

Fig. 5.3 Structure of the methelene blue dye

Table 5.2 Properties of methylene blue dye

Dye name Methylene blueMolecular formula C16H18N3SClMolar mass 319.85 g / molMelting point 100 - 110°CBoiling point Decomposes


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5.3 Results and discussion

The photo degradation of MB by undoped ZnO nanorods and ZnO nanorods

doped with aluminium, strontium and lithium under Phillips TUV-08 G5 lamp were

carried out. The efficiency of the dye degradation was reported by varying the irradiation

time and area of the catalyst. Extent of methylene blue degradation was estimated from

absorbance spectra as intact MB shows strong absorbance at 665 nm. Loss of intensity

and shift in this peak position was considered as degradation of methylene blue. The

percentage degradation (% D) was calculated using Equation (6).

Percentage of degradation = A0 - At / A0 x100 (6)

Where A0 = absorbance at t = 0 minute

At = absorbance at t minute

The degradation of methylene blue dye was carried out using ZnO nanorods with

varying irradiation time, area of the catalyst and the effect of doping with aluminium,

strontium and lithium.

5.3.1 Effect of Irradiation time

Fig. 5.4 Time-dependent UV–Vis absorption spectra for decolorization of methylene blueusing ZnO nanorods

450 500 550 600 650 700 7500.0

0.3

0.5

0.8

1.0

1.3

1.5

1.8

2.0

ZnO-3 hourZnO-2 hourZnO-1 hourmethelene blue

Abso

rban

ce(a

.u)

Wavelength(nm)

BCDE


135

Fig. 5.4 shows the time dependent UV–Vis spectra of methylene blue dye during

photo irradiation with ZnO nanorods. The rate of decolorization was recorded with

respect to the change in the intensity of absorption peak in visible region. The prominent

peak was observed at λmax i.e., 665 nm which decreased gradually with increase in

irradiation time from 1 hour, 2 hour and 3 hour indicating that the dye had been degraded.

The decolorization of dye was achieved as 42%, 47% and 74% for the irradiation time of

1hour, 2hour and 3 hour respectively.

Fig. 5.5 Photo catalytic decolorization of methelene blue dye with various irradiationtime

Fig 5.5 shows the effect of irradiation time on the decolorization of methelene blue

at natural pH. It can be seen that initial slopes of the curves representing rate of

decolorization, increase greatly by increasing irradiation time from 1hour, 2hour and 3

hour for MB.

5.3.2 Effect of Area of catalyst

Fig. 5.6 shows the area dependent UV–Vis spectra of MB dye during photo

irradiation with ZnO nanorods. The ZnO nanorods are used as catalyst. The area of the

ZnO nanorod thin films are varied and dipped in MB and exposed to UV-light. The rate

of decolorization was recorded with respect to the change in the intensity of absorption

0 20 40 60 80 100 120 140 160 1800

10

20

30

40

50

60

70

80

90

100

U V + ZnO

% D

ecolo

rizat

ion

T im e (m ins)


136

peak. No shift in absorbance at 665 nm was recorded. In this case, the absorbance of MB

shows the decrease in intensity of MB.

Fig. 5.6 Area-dependent UV–Vis absorption spectra for decolorization of methelene blueusing ZnO nanorods

When the mixture of ZnO nanorods and MB was exposed to UV-light with

variation in the area of the catalyst, 75% decomposition of MB was recorded. The

absorbance observed at 665 nm has been decreased gradually with increase in area of the

catalyst from 1cm2 to 2cm2, indicating the degradation of the dye.

Fig. 5.7 Photo catalytic decolorization of methelene blue dye with varying area ofcatalyst

500 550 600 650 700 7500.0

0.3

0.5

0.8

1.0

1.3

1.5

1.8

2.0

ZnO-2cm x 2cmZnO-1cm x 1cmm ethelene blue

Abso

rban

ce(a

.u)

W avelength(nm )

B C D

0 10 20 30 400

10

20

30

40

50

60

70

80

90

100

UV + ZnO

% D

ecol

orisa

tion

Area of catalyst (mm x mm)


137

The decolorization of dye was achieved as 43% and 75% for the variation in area

of the catalyst from 1cm2 to 2cm2. Fig 5.7 shows the effect of area of catalyst on the

decolorization of methelene blue. The photo catalytic destruction of other organic

pollutants has also exhibited the same dependency on catalyst dose [43]. This can be

explained on the basis of catalyst loading. It is found to be dependent on initial solute

concentration because with the increase in catalyst dosage, total active surface area

increases. Hence availability of more active sites on catalyst surface increases [44].

The results indicate that ZnO exhibits higher photo catalytic activity when

irradiation time and area of catalyst is increased for the decolorization of MB. The

decolorization efficiencies are given in tables 5.3 and 5.4.

Table 5.3 Photo degradation efficiencies of ZnO nanorods with various irradiation time

Irradiation time Efficiency (%)1 hour 42 %2 hour 47 %3 hour 74 %

Table 5.4 Photo degradation efficiencies of ZnO nanorods with varying area of catalyst

Area of catalyst Efficiency (%)1 cm2 43 %2 cm2 75 %

5.3.3 Effect of doping with aluminium, strontium and lithium

Fig. 5.8 and 5.9 show time and area dependent UV–Vis spectra of MB dye during

photo irradiation with aluminium doped ZnO nanorods. The rate of decolorization was

recorded with respect to the change in the intensity of absorption peak.

For Al doped ZnO nanorods the degradation efficiency was found to increase from

28%, 32% to 34.2% for the irradiation time of 1hour, 2hour and 3 hour

respectively.


138

It was also found that the degradation efficiency increases from 32% to 37% as the

area of catalyst was increased from 1cm2 to 2cm2.

Fig. 5.8 Time-dependent UV–Vis absorption spectra for decolorization of methylene blue

using aluminium doped ZnO nanorods

Fig. 5.9 Area-dependent UV–Vis absorption spectra for decolorization of methylene blueusing aluminium doped ZnO nanorods

Fig. 5.10 and 5.11 show time and area dependent UV–Vis spectra of MB dye during

photo irradiation with strontium ZnO nanorods. Exposure of the mixture of strontium

doped ZnO nanorods and MB to UV light resulted in 42% and 45% degradation of MB.

450 500 550 600 650 700 7500.0

0.3

0.5

0.8

1.0

1.3

1.5

1.8

2.0

Al doped ZnO-3hourAl doped ZnO-2hourAl doped ZnO-1hourmethelene blue

Abso

rban

ce(a

.u)

Wavelngth(nm)

B C D E

500 550 600 650 700 7500.0

0.3

0.5

0.8

1.0

1.3

1.5

1.8

2.0

Al doped ZnO-2cmx2cmAl doped ZnO-1cm x 1cmmethelene blue

Abso

rban

ce(a

.u)

Wavelength(nm)

B C D


139

Fig. 5.10 Time-dependent UV–Vis absorption spectra for decolorization of methyleneblue using strontium doped ZnO nanorods

Fig. 5.11 Area-dependent UV–Vis absorption spectra for decolorization of methyleneblue using strontium doped ZnO nanorods

For Sr doped ZnO nanorods the degradation efficiency was found to increase from

27%, 32% to 42% for the irradiation time of 1hour, 2hour and 3 hour respectively.

It was also found that the degradation efficiency increases from 30.5% to 44.7% as

the area of catalyst increases from 1cm2 to 2cm2.

450 500 550 600 650 700 7500.0

0.3

0.5

0.8

1.0

1.3

1.5

1.8

2.0

St doped ZnO - 3hourSt doped ZnO - 2hourSt doped ZnO - 1hourmehtelene blue

Abso

rban

ce(a

.u)

Wavelength(nm)

B C D E

500 550 600 650 700 7500.0

0.3

0.5

0.8

1.0

1.3

1.5

1.8

2.0

St dop ZnO-2cmx2cmSt dop ZnO-1cmx1cmmethelene blue

Abso

rban

ce(a

.u)

Wavelength(nm)

B C D


140

Fig. 5.12 and 5.13 show time and area dependent UV–Vis spectra of MB dye

during photo irradiation with lithium doped ZnO nanorods. Interesting results were

obtained when lithium doped ZnO nanorods and MB mixtures were exposed to UV light.

Rapid degradation of MB was recorded which showed maximum of 34.2% and 30.5%

degradation of MB.

Fig. 5.12 Time-dependent UV–Vis absorption spectra for decolorization of methyleneblue using lithium doped ZnO nanorods

Fig. 5.13 Area-dependent UV–Vis absorption spectra for decolorization of methyleneblue using lithium doped ZnO nanorods

500 550 600 650 700 7500.0

0.3

0.5

0.8

1.0

1.3

1.5

1.8

2.0

Li dop ZnO-2cmx2cmLi dop ZnO-1cmx1cmmethelene blue

Abso

rptio

n(a.

u)

Wavelength(nm)

B C D

500 550 600 650 700 7500.0

0.3

0.5

0.8

1.0

1.3

1.5

1.8

2.0

Li doped ZnO-3hourLi doped ZnO-2hourLi doped ZnO-1hourmethelene blue

Abso

rban

ce(a

.u)

Wavelength(nm)

B C D E


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For Li doped ZnO nanorods the degradation efficiency was found to increase from

25.2%, 28% to 34.2% for the irradiation time of 1hour, 2hour and 3 hour

respectively.

It was also found that the degradation efficiency increases from 25% to 30.5% as

the area of catalyst increases from 1cm2 to 2cm2.

The results indicate that ZnO nanorods doped with aluminium, strontium and lithium

exhibit photo catalytic activities when irradiation time and area of catalyst is increased

for the decolorization of MB. In the above three cases, strontium doped ZnO nanorods

exhibit better photocatalytic efficiency than the aluminium and lithium doped ZnO

nanorods. The photo degradation efficiencies were tabulated for various irradiation time

and area of catalyst in tables 5.5 and 5.6

Table 5.5 Photo degradation efficiencies of doped ZnO nanorods for various irradiationtime

Irradiation time Efficiency (%)Al doped ZnO Sr doped ZnO Li doped ZnO

1 hour 28% 27% 25.2%2 hour 32% 32% 28%3 hour 34.2% 42% 34%

Table 5.6 Photo degradation efficiencies of doped ZnO nanorods with varying area ofcatalyst

Area of catalyst Efficiency (%)Al doped ZnO Sr doped ZnO Li doped ZnO

1 cm2 32% 30.5% 25%2 cm2 37% 44.7% 30.5%

When comparing the photocatalytic activity of the undoped ZnO nanorods and the

ZnO nanorods doped with aluminium, strontium and lithium, the efficiency of the photo

degradation of methylene blue dye is high in the undoped ZnO nanorods. The above

degradation efficiencies were the result of 8W- UV irradiation. The textile reactive dye

MB is degraded at the maximum of 75% efficiency with 8W-UV source. It is an

encouraging result and it can be taken for future research.


142

References

[1] Ali, A. M.; Emanuelsson, E. A. C.; Patterson, D. A. Appl. Catal. B, 97, 168–181. doi:

10.1016 /j.apcatb.2010.03.037 (2010).

[2] Pardeshi, S. K.; Patil, A. B. J. Mol. Catal. A: Chem. 2009, 308, 32–40. doi:10.1016

/j.molcata. 2009.03.023.

[3] Qamar, M.; Muneer, M. Desalination 2009, 249, 535–540, doi:10.1016

/j.desal.01.022 (2009).

[4] Poulios, I.; Makri, D.; Prohaska, X. Global NEST, 1, 55–62 (1999).

[5] Carraway, E. R.; Hoffman, A. J.; Hoffmann, M. R. Environ. Sci. Technol., 28, 786–

793. doi:10.1021/es00054a007 (1994).

[6] M. Miyauchi, A. Nakajima, T. Watanabe, K. Hashimoto, Photocatalysis and photo

induced hydrophilicity of various metal oxide thin films, Chem. Mater. 14, 2812–2816

(2002).

[7] A. Akyol, M. Bayramoglu, Photocatalytic degradation of Remazol Red F3B using

ZnO catalyst, J. Hazard. Mater. B 124, 241–246 (2005).

[8] N. Daneshvar, D. Salari, A.R. Khataee, Photocatalytic degradation of azo dye acid red

14 in water on ZnO as an alternative catalyst to TiO2, J. Photochem. Photobiol. A: Chem.

162, 317–322 (2004).

[9] R. Comparelli, E. Fanizza, M.L. Curri, P.D. Cozzi, G. Mascolo, G. Agostiano, UV-

induced photocatalytic degradation of azo dyes by organic-capped ZnO nanocrystals

immobilized onto substrates, Appl. Catal. B: Environ. 60, 1–11 (2005).

[10] V. Kandavelu, H. Kastien, K.R. Thampi, Photocatalytic degradation of isothiazolin-

3-ones in water and emulsion paints containing nanocrystalline TiO2 and ZnO catalysts,

Appl. Catal. B: Environ. 48, 101–111 (2004).

[11] P. Percherancier, R. Chapelon, B. Pouyet, Semiconductor-sensitized pho-

todegradation of pesticides in water: the case of carbetamide, J. Photochem. Photobiol. A:

Chem. 87, 261–266 (1995).


143

[12] A.A. Khodja, T. Sehili, J.F. Pihichowski, P. Boule, Photocatalytic degradation of 2-

phenylphenol on TiO2 and ZnO in aqueous suspensions, J. Photochem. Photobiol. A:

Chem. 141, 231–239 (2001).

[13] C.C. Chen, Degradation pathways of ethyl violet by photocatalytic reaction with

ZnO dispersions, J. Mol. Catal. A: Chem. 264, 82–92 (2006).

[14] C.A.K. Gouvêa, F. Wypych, S.G. Moraes, N. Durán, N. Nagata, P. Peralta-Zamora,

Semiconductor assisted photocatalytic degradation of reactive dyes in aqueous solution,

Chemosphere 40, 433–440 (2000).

[15] G. Wang, D. Chen, H. Zhang, J.Z. Zhang, J.H. Li, Tunable photocurrent spectrum in

well-oriented zinc oxide nanorod arrays with enhanced photocatalytic activity, J. Phys.

Chem. C 112, 8850–8855 (2008).

[16] Hornyak, G. L.; Dutta, J.; Tibbals, H. F.; Rao, A. Introduction to nanoscience; CRC

Press: Boca Raton, (2008).

[17] Kimura, T.; Yamauchi, Y.; Miyamoto, N. Chem.–Eur. J., 16,12069–12073.

doi:10.1002/chem.201001251 (2010).

[18] Baruah S, Thanachayanont C and Dutta J.Sci. Technol. Adv. Mater. 9, 025009

(2008).

[19] Z.Y.He, Y.G.Li, Q.H.Zhang, H.Z.Wang, Capillary microchannel-based

microreactors with highly durable ZnO/TiO2 nanorod arrays for rapid, high efficiency

and continuous flow photocatalysis, Appl.Catal.B:Environ. 93, 376–382 (2009).

[20] A. Sharma, P. Rao, R.P. Mathur, S.C. Ameta, Photocatalytic reactions of xylidine

ponceau on semiconducting zinc oxide powder, J. Photochem. Photobiol. A 86, 197–200

(1995).

[21] F.D. Mai, C.C. Chen, J.L. Chen, S.C. Liu, J. Chromatogr. A 1189, 355–365 (2008).

[22] C. Lu, Y. Wu, F. Mai, W. Chung, C. Wu, W. Lin, C. Chen, Degradation efficiencies

and mechanisms of the ZnO-mediated photocatalytic degradation of Basic Blue 11 under

visible light irradiation, J. Mol. Catal. A: Chem. 310, 159–165 (2009).


144

[23] N. Sobana, M. Swaminathan, Combination effect of ZnO and activated carbon for

solar assisted photocatalytic degradation of Direct Blue 53, Sol. Energy Mater. Sol. Cells

91, 727–734 (2007).

[24] S.K. Kansal, A.H. Ali, S. Kapoor, Photocatalytic decolorization of biebrich scarlet

dye in aqueous phase using different nanophotocatalysts, Desalination 259, 147–155

(2010).

[25] S. Sakthivel, B. Neppolian, M.V. Shankar, B. Arabindoo, M. Palanichamy, V.

Murugesan, Solar photocatalytic degradation of azo dye: comparison of pho-tocatalytic

efficiency of ZnO and TiO2, Sol. Energy Mater. Sol. Cells 77, 65–82 (2003).

[26] G. Colón, M.C. Hidalgo, J.A. Navío, E. Pulido Melián, O. González Díaz, J.M.

Do˜na Rodríguez, Highly photoactive ZnO by amine capping-assisted hydrothermal

treatment, Appl. Catal. B 83, 30–38 (2008).

[27] N. Kislov, J. Lahiri, H. Verma, D.Y. Goswami, E. Stefanakos, M. Batzill,

Photocatalytic degradation of methyl orange over single crystalline ZnO: orientation

dependence of photoactivity and photostability of ZnO, Langmuir 25, 3310–3315 (2009).

[28] S. Daniele, M.N. Ghazzal, L.G. Hubert-Pfalzgraf, C. Duchamp, C. Guillard, G.

Ledoux, Mater. Res. Bull. 41, 2210–2218 (2006).

[29] M. El-Kemary, H. El-Shamy, I. El-Mehasseb, Photocatalytic degradation of

ciprofloxacin drug in water using ZnO nanoparticles, J. Lumin. 130, 2327–2331 (2010).

[30] R. Kitture, S.J. Koppikar, R. Kaul-Ghanekar, S.N. Kale, Catalyst efficiency, pho-

tostability and reusability study of ZnO nanoparticles in visible light for dye degradation,

J. Phys. Chem. Solids 72, 60–66 (2011).

[31] V. Shinde, T.P. Gujar, T. Noda, D. Fujita, A. Vinu, M. Grandcolas, J. Ye, Growth of

shape- and size-selective zinc oxide nanorods by a microwave-assisted bath deposition

method: effect on photocatalysis properties, Chem. Eur. J. 16, 10569–10575 (2010).

[32] F. Xu, P. Zhang, A. Navrotsky, Z.-Y. Yuan, T.-Z. Ren, M. Halasa, B.-L. Su, Hierar-

chically assembled porous ZnO nanoparticles: synthesis, surface energy, and

photocatalytic activity, Chem. Mater. 19, 5680–5686 (2007).


145

[33] X. Li, K. Lv, K. Deng, J. Tang, R. Su, J. Sun, L. Chen, Synthesis and

characterization of ZnO and TiO2 hollow spheres with enhanced photoreactivity, Mater.

Sci. Eng. B 158, 40–47 (2009).

[34] M.S. Mohajerani, A. Lak, A. Simchi, Effect of morphology on the solar photocat-

alytic behavior of ZnO nanostructures, J. Alloys Compd. 485, 616–620 (2009).

[35] Y. Wang, X. Li, N. Wang, X. Quan, Y. Chen, Controllable synthesis of ZnO

nanoflowers and their morphology-dependent photocatalytic activities, Sep. Purif.

Technol. 62, 727–732 (2008).

[36] B. Li, Y. Wang, Facile synthesis and enhanced photocatalytic performance of

flower-like ZnO hierarchical microstructures, J. Phys. Chem. C 114, 890–896 (2010).

[37] Wang, R.; Xin, J. H.; Yang, Y.; Liu, H.; Xu, L.; Hu, J. Appl. Surf. Sci., 227, 312–

317. doi:10.1016/j.apsusc.2003.12.012 (2004).

[38] Vanheusden, K.; Warren, W. L.; Voigt, J. A.; Seager, C. H.; Tallant, D. R. Appl.

Phys. Lett., 67, 1280–1282. doi:10.1063/1.114397 (1995).

[39] Colis, S.; Bieber, H.; Begin-Colin, S.; Schmerber, G.; Leuvrey, C.; Dinia, A. Chem.

Phys. Lett., 422, 529–533. doi:10.1016/j.cplett.2006.02.109 (2006).

[40] Ullah, R. Dutta, J. J. Hazard. Mater., 156, 194–200, doi:10.1016 /j.jhazmat

2007.12.0 33 (2008).

[41] Baruah, S.; Rafique, R. F.; Dutta, J. NANO, 3, 399–407. doi:10.1142

/S17932920080 0126X (2008).

[42] http://www.methylene-blue.com/substance.php

[43] A. Akyol, H.C. Yatmaz, M. Bayramoglu, Appl. Catal. B Environ. 54, 19 (2004).

[44] M.S.T. Gonclaves, A.M.F. Oliveira-Campose, E.M.M.S. Pinto, P.M.S. Plasencia,

M.J.R.P Queiroz, Chemosphere 39:781, doi:10.1016/S0045-6535(99)00013-2, (1999).


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CHAPTER - V PHOTOCATALYSIS OF ZnO NANORODSshodhganga.inflibnet.ac.in/bitstream/10603/33622/10/10_chapter4.pdf · Lu et al. [22] used ZnO to degrade Basic Blue 11 under visible light