synthesis and characterisation of lanthanum added zno ...joics.org/gallery/ics-1925.pdf · zno...
TRANSCRIPT
Synthesis and Characterisation of Lanthanum added
ZnO Nanostructures
M. Sudha1, A. Balamurugan2*, S. Surendhiran3, P. Manoj Kumar3,
Y.A. Syed Khadar4
1 Department of Physics, Government Arts College
Udhagamandalam – 643002, Tamilnadu, India
2 Department of Physics, Government Arts and Science College
Avinashi – 641654, Tamilnadu, India
3 Centre for Nano Science and Technology, K.S. Rangasamy College of Technology
Tiruchengode -637215,Tamilnadu, India
4Department of Physics, K.S.R College of Arts and Science for Women
Tiruchengode -637215, Tamilnadu, India
Abstract
The pure ZnO and La doped ZnO nanorods were prepared by sonochemical routeand
followed by calcination at 500℃. The prepared nanorods were comprehensively investigated
through X-ray diffraction (XRD), Ultra-violet spectroscopy (UV-Vis), Fourier transform
infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM),
Particle size analysis (PSA) to get a broader understanding about the influence of processing
parameter over the ZnO and La doped ZnO nanorods, structural, optical physico-chemical,
and photo catalytic property, a comparative evaluation was performed. The Degradation
performance on methylene blue (MB) under UV light irradiation was done to explore the
photo catalytic activity.
Keywords: La doped ZnO nanorods; Sonochemical method; Photo catalytic activity
1. Introduction
Nanomaterials deal with promising opportunities for improved and tailored properties
for application in environmental catalysis due to their unique size and dimensional properties
[1-4]. Past few decades, several natural and engineered nano metal oxides have been studied
about their strong dye degradation performances, antimicrobial properties and so on. Among
them, ZnO is increasingly recognized as a proper alternative due to its easily controllable
properties with the wide band gap semiconductors (3.37 eV). Already ZnO was also reported
to exhibit higher quantum efficiency and photocatalytic activity than nano TiO2. It is one of
the widely used photocatalysts due to its high catalytic efficiency, quick response, low cost,
and environmental sustainability [5-8]. However, ZnO still exhibits low photoenergy
conversion efficiency because of their low charge separation efficiency and fast
recombination of charge carriers, and more modification is indeed needed. In order to
increase the physical and chemical properties of ZnO to better photocatalyst, one possible
approach is to dope ZnO with different metal oxides. Recently, a large number of studies
have been focused on improving the ZnO properties by doping with other metal oxides [8-
Journal of Information and Computational Science
Volume 9 Issue 12 - 2019
ISSN: 1548-7741
www.joics.org396
11]. A large of synthesis methods have been used to prepare ZnO, such as sol gel, co
precipitation, spray pyrolysis, pulsed laser deposition, chemical vapour deposition, electro-
deposition, the sonication technique. Among these methods, the sonication method is an
attractive process due to the easiness, reproducibility and controllability of physical and
chemical properties [12].
In this present study, pure and lanthanum doped ZnO prepared by sonochemical
method. The influence of La doping, structural and morphology on photocatalytic activity of
ZnO was elaborately investigated.
2. Experimental details
2.1 Materials and Methods
ZnO and Lanthanum doped ZnO nanorods were prepared by sonication method. AR
grade zinc acetate (ZnC4H6O4 - 99.99%), Lanthanum nitrate (H12LaN3O15 - 99.99%), sodium
hydroxide, double distilled water (DD) were used as precursor. The stoichiometry ratio of
zinc acetate and Lanthanum nitrate were dissolved separately in double distilled water. The
Lanthanum nitrate solution in required stoichiometry was slowly added into vigorously
stirred zinc acetate solution. After 15 mins, sodium hydroxide solution was added drop wise
into the above solution. Then this solution was transferred to sonication chamber and
sonicated for 30 mins with 40Hz power. The resultant solid product was dried at 100°C for 6
h and calcined at 500°C for 2 h. The pure ZnO particles were also prepared by the same
procedure without the adding lanthanum nitrate to zinc solution. The lanthanum doping
concentrations (0.1, 0.3, 0.5%) are expressed in wt. %. The synthesis procedure was
schematically shown in figure 1.
2.2. Characterization techniques
Crystalline nature of samples were detected through XRD measurements (X’Pert PRO;
PANalytical, the Netherlands) with CuKα as a radiation source (λ = 1.54060 Å). The
functional groups were traced through Fourier transform infrared spectrometer (FTIR)
(Spectrum 100; Perkin Elmer, USA) in the frequency range between 4000 to 400 cm−1.
Particle size and morphologies was exploited to field emission scanning electron microscopy
(Quanta FEG 250, Germany) and Particle size analyser (Nanophox; Sympatec, Zellerfeld,
Germany) respectively. Optical absorptions and photo degradation studies were absorbed
using UV-Vis spectrometer (UV - Vis; UV-2450, Shimadzu, USA).
Photocatalytic degradation of methylene blue dye (MB) in prepared nanorods solution
under UV light was used to evaluate the photocatalytic activity of the prepared pure and La
doped ZnO nanorods. In an aqueous methylene blue solution, prepared ZnO nanorods were
dispersed and kept under constant agitation using a magnetic stirrer connected to the reactor.
For the photocatalytic assessment, 10 ml sample was taken out from the reaction solution at
30 min interval. Before the assessment, to remove any suspended particles the aqueous
samples were centrifuged at 4000 rpm. Following which, the residual solution of methylene
blue was measured at 665 nm against UV–Vis spectrophotometer (Cary 8454; Agilent,
Singapore). The rate of degradation (D%) of methylene blue dye by prepared pure and La
doped ZnO nanorods under UV irradiation was calculated with in virtue of initial absorbance
A0, absorbance At with respect to (t) minutes and is given by [13]
Journal of Information and Computational Science
Volume 9 Issue 12 - 2019
ISSN: 1548-7741
www.joics.org397
𝐃 % = 𝐀𝟎 − 𝐀𝐭
𝐀𝟎 %
3. Result and discussion
The powder X-ray diffraction patterns of ZnO and La-doped ZnO with different
lanthanum concentrations (0.1, 0.3, 0.5 % of La) are shown in Fig. 2. The diffraction peaks
and their relative intensities of both pure and La doped ZnO nanorods were in good
agreement with the standard JCPDS card no. 36-1451. The XRD patterns of all the La-doped
ZnO nanorods are almost similar to that of ZnO, suggesting that there is no major change in
the crystal structure upon La doping. However, it should be noted that the La-doped nanorods
have a wider and lower intense diffraction peaks than pure ZnO and also small variation in
peak positions. Moreover, the XRD peaks of La-doped ZnO continuously get broader and
shifts with increasing the La doping. Hence, it was clear that the dopant could not alter the
crystal structure of ZnO, whereas it dispersed uniformly in the ZnO. It is fascinating to note
that the crystal size of La doped ZnO calculated using Debye - Scherrer equation is much
smaller as compared with that of the pure ZnO, which decreases with increasing the La
doping concentration in ZnO [14]. This decrease in the crystal size is due to distortion in the
ZnO by La dopant ions, which control the rate of growth of ZnO [15-16].
The FT-IR spectra of pure and La doped ZnO nanorods were shown in Figure 3. The
absorption band at 1400 - 1500 cm-1 can be interpreted as C=O bonding vibrations arisen
from very small unavoidable traces of carbonate absorbed from environment. The broader
band peaks at 3400 – 3500 cm-1 indicates the presence of O-H molecules in prepared
samples it may be KBr which was used as medium for FTIR analysis. The strong intensity
band at around 505 cm-1 clearly indicates the Zn-O stretching vibration and the band at 607
cm-1 endorses the presence of ZnO and La [17-19]. The 880 cm-1 corresponds to N-O
deformation vibration.It was noted from the FT-IR spectra that the Zn-O vibrational mode
was more obviously observed and this clearly concludes a strong doping exist in La doped
ZnO nanorods.
The surface morphology of prepared nanorodswas scanned and showed in Fig 4, b, c,
d respectively for pure ZnO and different level of La content in ZnO. FESEM image of pure
and La doped ZnO nanorods illustrates that the morphology is well ordered and clearly
indicated the rod-like morphology. The size of the nanoparticle particles are in the range 50 -
100 nm, suggesting a wide range of band gap value in the ZnO nanorods. Furthermore, from
the fig. 3a-d it was noted that as La concentration increases, particle size of the samples
reduced, which was reliable with the XRD results.
The average particle size distributions of prepared samples are shown in Fig. 5.
Average particle size was distributed in the range of 85 - 60 nm size, respectively, for pure
and La doped ZnO samples. Moreover, the mean size distribution (d50) of particles is 83.2±3,
72.9±3, 67.2±3 and 64.1±3 nm, respectively, for Pure ZnO and La doped ZnO (0.1, 0.3, 0.5
%). The size of nanorods decreases from 83.2 to 64.1 nm as the dopant (La ions)
concentration increases in ZnO nanorods. The above results indicate that the doping La ions
can be reason for size effects in ZnO nanorods and plays a dominant role in reducing size of
the prepared nanorods [20-24].
Journal of Information and Computational Science
Volume 9 Issue 12 - 2019
ISSN: 1548-7741
www.joics.org398
The optical absorption properties of pure and La doped ZnO nanorods with different
doping concentrations of La were investigated by UV–Vis absorption spectra and shown in
Figure 6. From Figure 5, it was noted that the band-edge absorption of the prepared pure and
La doped ZnO nanorods traced at around 399-369 nm. The optical band gap of Eg is
calculated using the following equation [25]
Band gap energy (Eg) = 𝒉 𝒄
𝝀
The wavelength to the absorbance edge for Pure and La doped ZnO nanorods are 399,
380, 375 and 369 nm, respectively. The band gap which corresponds to the absorption edge
found in UV – Vis spectra of the prepared nanorods are 3.11, 3.26, 3.32, 3.40 eV for pure and
La doped ZnO nanorods, respectively. The energy band gap for the prepared samples was
calculated by using Tauc plot equation. The transition plot of direct band gap [( Ephot) n vs.
Ephot, Ephot is the photon energy] is tabulated in table 1. Here n is a constant, equal to 1/2
for the direct and 2 for indirect band gap semiconductors. The energy band gap values (Eg)
obtained from direct plot of transitions are 2.97, 3.04, 3.10 and 3.27 eV and from indirect
transitions are 2.81, 2.90, 2.99 and 3.18 eV for respectively pure and La doped ZnO. From
the above results, the Eg values increases while La doping concentrations increase in pure
ZnO [26-30]. It clearly shows that the prepared ZnO and La doped ZnO samples revelation
the semiconducting behaviour due to its band gap values.
The photocatalytic behaviour of the as prepared pure and La doped ZnO nanorods
with different La doping concentrations are explored by analysis the photocatalytic
degradation of methylene blue dye. In order to conclude the best dopant and doping
concentration to synthesise the most effective ZnO as photocatalyst to demonstrate its
potential environmental application for the removal of contaminants in waste water is tested,
where in methylene blue is used as a typical contaminant [31].
It confirms that the degradation decolourisation of methylene blue is due to the
photocatalytic reaction of ZnO nanorods under UV illumination. The photocatalytic
degradation process is confirmed out by noticing the absorption peak of methylene blue at λ=
665 nm [32-35]. It is noted that the photo degradation decolourisation of methylene blue dye
with the pure and La doped ZnO nanorods are very steep for the first 30 min. and then it
slows down with time.
The 0.5 % La doped ZnO nanorods shows higher degree of dye degradation (91%)
than that of lower La concentration doped and pure ZnO nanorods during the assessed time
(210 min.). This adverse photocatalytic behaviour of high concentration La doped ZnO
nanorods can be coined to the fact that the 0.5 % La doped ZnO nanorods shows lower
crystal size and lower average particle size distribution and also shows distinct rod like
structure [36-41]. It is observed from the results that the prepared ZnO nanorods samples
show higher effectiveness with respect to photocatalytic degradation of MB dye, a
comparative assessment with earlier reports on ZnO as well as doped ZnO nanorods was
done and tabulated in table 2.
4. Conclusion
In summary, pure and La-doped ZnO with different concentrations of La were
successfully prepared by sonication method and characterized elaborately. The crystalline
Journal of Information and Computational Science
Volume 9 Issue 12 - 2019
ISSN: 1548-7741
www.joics.org399
size of the prepared pure and La doped ZnO nanorods are ranged from nm. The average
crystal size and particle sizes were decreased while La doping concentration increases. From
the FESEM results, the nanorods are in rod like morphology. The calculated band gap
energies of pure and La doped ZnO nanorods were increased from 3.11 eV to 3.40 eV with
increasing the lanthanum doping concentration. Hence, these results indicated that the
lanthanum doping concentration plays an important role in tuning the size, band gap and
photoluminescence property of the ZnO nanorods. In addition the prepared La doped ZnO
nanorods possess the significant degradation property against methylene blue dye.The 0.5%
La doped ZnO nanorods possess the outstanding degradation property against methylene blue
dye has been concluded.
References
[1] M Fu, Y Li, P Lu, J Liu and F DongAppl Surf Sci.258,1587 (2011)
[2] G Poongodia, P Anandan, R MohanKumar and R JayavelSpectrochimicaActa Part A:
Molecular and Biomolecular Spectroscopy (SAA).148,237 (2015)
[3] C Karunakaran, V Rajeswari, P GomathisankarMat SciSemicon Proc.14,133 (2011)
[4] KThongsuriwong, P Amornpitoksuk, SSuwanboonJ Sol-Gel SciTechnol62,304 (2012)
[5] N V Kaneva, DTDimitrov, C D, DushkinAppl Surf Sci. 257,8113 (2011)
[6] K Thongsuriwonga, P Amornpitoksukac and S SuwanboonAdv Powder Technol.24 275
(2013)
[7] M Mittal M Sharma and PPandeyJ. Sol. Energy110,386 (2014)
[8] I Polat, S Yılmazbİlknur, AEmin and BMSökmenMater Chem Phys. 148,528 (2014)
[9] V Kavitha, J Mayandi, P Mahalingam, NSethupathiMaterials Today: Proceedings, (2019)
[10] C Wu, L Shen, YC Zhang and Q HuangMater Lett.65,1794 (2011)
[11] C Wu, YC Zhang and Q HuangMater Lett.119, 104 (2014)
[12] JC Sin, SM Lam, I Satoshi and KT Lee ApplCatal B-Environ.148, 258 (2014)
[13] H Moussa, E Girot, K Mozet, H Alem, G MedjahdiApplCatal B-Environ.185,11 (2016)
[14] N Talebian, SM Amininezhad and M DoudiJ PhotochPhotobio B. 120, 66 (2013)
[15] S Kant and A KumarAdv. Mat. Lett.,3,350 (2012)
[16] S Klosek and D RafteryJ. Phys. Chem. B, 105,2815(2001)
[17] M Ajili, M Castagné and NK TurkiSuperlatticeMicrost.53,213(2013)
[18] R Mohan, K Krishnamoorthy and SJ KimSolid State Commun.152,375 (2012)
[19] Y Caglar, S Aksoy, S Ilican, M CaglarSuperlatticeMicrost.46, 469 (2009)
[20] K Meziane, A Elhichou and A ElhamidiJ Phys.758, 012019(2016)
[21] FZ Bedia, A Bedia, N Maloufi, M Aillerie and F GentyJ Alloy Compd. 616, 312 (2014)
[22] G Jayakumar, AA Irudayaraj, AD RajMaterials Today: Proceedings4,11690(2017)
[23] OAYıldırım, HE Unalan, CDurucanJ. Am. Ceram. Soc.,96, 766 (2013)
[24] B Subash, B Krishnakumar and M SwaminathanMat SciSemicon Proc.16,1070(2013).
[25] A Phuruangrat, O Yayapao, T Thongtem, and S ThongtemJ. Nanomater,367529, 9 (2014)
[26] RA Zargar, M Arora, M Ahmad and AK HafizJ. Mater. Sci.196545, 6(2015)
[27] J Yang, J Lee, K Im and S LimPhysica. E 42, 51 (2009)
[28] FSeveriano, GGarcía, LCastañeda, and VLGayouJ. Nanomater.1629702, 8(2017)
Journal of Information and Computational Science
Volume 9 Issue 12 - 2019
ISSN: 1548-7741
www.joics.org400
[29] KS Ahmad and SB JaffriOpen Chem.16, 556 (2018)
[30] N Nithya G Bhoopathi G Magesh C Daniel andNesaKumarMat SciSemicon Proc.83, 70
(2018)
[31] Y Zhang, MK Ram EK Stefanakos and DY GoswamiSurf Coat Tech. 217,119(2013)
[32] Q Zhang, JK Liu, JD Wang, HX Luo and Y LuIndEngChem Res.53,13236 (2014)
[33] K Kandasamy, M Venkatesh, YAS Khadar and P RajasinghMaterials Today: Proceedings.
(2019)
[34] H Qin, W Li, Y Xia and T HeACS Appl. Mater. Interfaces 3, 3152 (2011)
[35] S Suwanboon, P Amornpitoksuk and P Bangrak Ceram Int.37, 333(2011).
[36] YA Syed Khadar, A Balamurugan, VP Devarajan and R SubramanianOrient j. chem.33, 2405
(2017)
[37] S Liu, C Li, J Yu, Q XiangCryst. Eng. Comm. 13, 2533 (2011)
[38] A Balamurugan, M Sudha, S Surendhiran, R Anandarasu, S Ravikumar and YA Syed
KhadarMaterials Today: Proceedings. (2019)
[39] C Xu, L Cao, G Su, W Liu, X Qu and Y Yu J Alloy Compd.497, 373 (2010)
[40] YA Syed Khadar, A Balamurugan, VP Devarajan, R Subramanian and S Dinesh KumarJ
Mater Res Technol. 8, 267 (2019)
[41] S Anandan, A Vinu, KLP SheejaLovely, N Gokulakrishnan, P Srinivasu, T Mori, V
Murugesh, V Sivamurugan and K ArigaJ Mol Catal A-Chem. 266, 149 (2007)
Journal of Information and Computational Science
Volume 9 Issue 12 - 2019
ISSN: 1548-7741
www.joics.org401
Table 1. The crystal size, particle size and band gap values of pure ZnO and La doped
ZnO nanorods
Sample code
Crystal
size
(nm)
Particle
size
(nm)
λmax
(nm)
Energy band
gap (eV)
by absorption
peak
Energy band gap (eV)
by Tauc plot
Direct Indirect
Pure ZnO 33 83.2 399 3.11 2.97 2.81
ZnO: 0.1 % La 29 72.9 380 3.26 3.04 2.90
ZnO: 0.3 % La 27 67.2 375 3.32 3.10 2.99
ZnO: 0.5 % La 24 64.1 369 3.40 3.27 3.18
Table. 2. Comparative assessment with earlier reports on photocatalytic performance of pure
ZnO and Doped ZnO nanorods
S. No Photocatalyst – Method Degradation
efficiency (%) Dopant
Improvement
in degradation
efficiency (%)
Reference
1. ZnO – Sol Gel 75 Ni 88 15
2. ZnO – Precipitation 72 Ag 81 29
3. ZnO – Sol Gel 73 Sr 86 30
4. ZnO – Hydrothermal 70 Co 78 39
5. ZnO – Sonication
(proposed work) 76 La 94 -
Journal of Information and Computational Science
Volume 9 Issue 12 - 2019
ISSN: 1548-7741
www.joics.org402
Fig. 1. Schematic representation of La doped ZnO synthesis procedure
Fig. 2. XRD pattern of pure and La doped ZnO nanorods calcined at 300° C
Journal of Information and Computational Science
Volume 9 Issue 12 - 2019
ISSN: 1548-7741
www.joics.org403
Fig. 3. FTIR spectra of pure and La doped ZnO nanorods
Fig. 4. FESEM images of pure and La doped ZnO nanorods
Journal of Information and Computational Science
Volume 9 Issue 12 - 2019
ISSN: 1548-7741
www.joics.org404
Fig. 5 Particle size distribution of pure and La doped ZnO nanorods
Fig. 6. UV-Vis absorption spectra of pure and La doped ZnO nanorods
Journal of Information and Computational Science
Volume 9 Issue 12 - 2019
ISSN: 1548-7741
www.joics.org405
Fig. 7. Photocatalytic activity of pure and La doped ZnO nanorods
Journal of Information and Computational Science
Volume 9 Issue 12 - 2019
ISSN: 1548-7741
www.joics.org406