Synthesis and Characterization of Zns Nanoparticles - IJIRCCE

ISSN(Online): 2320-9801 ISSN (Print) : 2320-9798

International Journal of Innovative Research in Computer and Communication Engineering (An ISO 3297: 2007 Certified Organization)

Vol. 4, Special Issue 4, August 2016

Synthesis and Characterization of Zns Nanoparticles Priyanka Tonk1,Tashi Dawa1, Mindu Dorji1, Dorji Chozam1, Harmeet Singh Bhullar1, Vikas Thakur2, Tarun Chandel3, M. Muthuvinayagam4 and Urvashi Verma 1* Department of Physics, A.P.Goyal Shimla University, Shimla, India1 Dept. of ECE, Manav Rachna University, Haryana, India2 School of Studies in Physics, Jiwaji University Gwalior, India3 Department of physics, Kalasalingam University, Krishnankoil, Tamil Nadu, India 4 ABSTRACT: Achemical route method was used to synthesis zinc sulphide (ZnS) nanoparticles using zinc acetate dehydrate, thiourea,triethanolamineand ammonia in aqueous solution as starting materials. Triethanolamine was used as capping agent in precipitation. Characterization of nanoparticles was done using x-ray diffraction (XRD), scanning electron microscope (SEM), UV Visible spectroscopy. The XRD pattern of the sample contains many peaks which show that there is the presence of impurities in the sample. Also, the SEM result shows the spherical morphology of the nanoparticles. KEYWORDS: Nanoparticles, XRD, SEM, Quantum confinement effect. I. INTRODUCTION Zinc sulphide, a direct wide band gap (3.8 eV) transparent semiconductor, is one of the most important materials used in photonics research.ZnS is a potential candidate for variety of applications such as electroluminescent devices, soalr cells and other optoelectronic devices [1,2]. One-dimensional nanostructures of ZnS are attractive because they are candidates for electronic and optoelectronic nanodevices [3-5]. ZnScan crytallize in either the Zinc blende or the wurtzite structures, but for technological applications, wurtzite is probably the most useful one because of its non central symmetry and polar surfaces. It is very attaractive material for the detection, emission and modulation of visible and near ultraviolet light [6,7], and is believed to be one of the most promising materials for blue emitting laser diodes [8] and thin film electroluminescent displays and mulitlayers dielectric filters [9,10]. The preparation of ZnS particles is of particular interest due to their potential excellent optical and optoelectronics properties, however, only a few numbers of publications related to ZnSnanocrystals can be found in the literature due probably to the difficulty in their preparation since there is no chemical precursor which can give directly ZnSparticles. It is thus, a great challenge to generate ZnS nanoparticles into the channels of porous media. In this paper, we present a simple chemical method to synthesize the ZnS nanoparticles and their structural, morphological and optical characteriztaions. II. EXPERIMENTAL DETAILS AR graded zinc acetate dehydrate (Zn(CH3OO)2.2H2O), thiourea (CH4N2S) and triethanol ammine (TEA) (C6H15NO3), ammonia in aqueous solution as starting materials. TEA was used as capping agent in precipitation. Ammonia solution was used as a stabilizer. The solution was obtained by dissolving a weighted amount of zinc acetate and thiourea in distilled water. 3mL of TEA was added to the solution. The pH of the solution was adjusted to 9 by adding ammonia solution. The solution Copyright to IJIRCCE

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was then kept in hot air oven at 60 °C for 2 hrs. Finally the solution was placed in air for 24 hrs, filtered and washed with deionized water several times and dried in oven at 80 °C. Powder of ZnS so obtained was collected and characterized by structural, morphological and optical studies. III. RESULT ANDDISCUSSION A. Structural studies: The crystalline nature of the prepared nanosizedZnS powder is evident from the X-ray diffraction pattern (Fig. 1). The indexed peaks at 2θ = 19.409˚, 2θ = 27.786˚, 2θ = 33.053˚ and 2θ = 33.521˚ corresponding to the (111), (220) and (222) planes, respectively, matches with the reported value (JCPDS card, No. 5-0566) [11].The peaks are identified as spherically cubic (blend) structure. The calculated lattice parameters are depicted in table 1.The broad feature of the peaks indicatesthe crystal size is in nanometres range.The isostructural phase may be caused by the presence of substitutional impurities of similar atomic size but differing atomic number that give rise to deviation in intensity. Deviations in peak positions are observed due to thermal expansion while XRD peak profile shape and width are the result of imperfections in both the experimental setup and the sample. The ZnS samples with controllable vacancies were obtained via adding tri ethanolamine (TEA) as capping agent. Table 1.Calculation of lattice parameters

The

2θ(degree)

r (atomic radius of Zn) nm

λ (wavelength of X-ray(nm)

(interplanar distance) d =

(unit cell dimension) a= 2√2 Å

19.409

0.1332

0.154

0.456973

1.032083

2

111

27.786

0.1332

0.154

0.3207

1.032083

3

220

33.053

0.1332

0.154

0.270745

1.032083

4

222

average

crystalline

of

the

+

Peak

=

was calculated by the Scherrer equation [12] 0.9 = cos Where, D is the mean crystallite size, λ is the wavelength of X-ray (0.154 nm), θ is the degree of the diffraction peak/the Bragg’s angle, and β is the full width at half maximum of the XRD peak appearing at the diffraction angle θ. The average crystallite size of ZnS nanoparticles calculated using the above formula is found to be 0.227nm.

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size

ℎ +

powder

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Fig. 1 XRD pattern of ZnS nanoparticles

Fig. 2 SEM micrographs of ZnS nanoparticles

B. Morphological studies: The scanning electron micrographs (SEM) were obtained with non-conducting mode with different magnifications for different amount of capping agents used are shown in Fig. 2 (a- 2ml, b-3ml, c-4ml & d-higher magnification of c). The SEM microstructural analysis shows that the synthesized ZnS contains mainly the grains of ZnS particles (crystallite) with regular shape. The SEM image for ZnS nanoparticles seen in fig. 2(a) indicates that spherical nanoparticles are homogeneous and the micro-particles become crimped gradually with increasing the amount of TEA because s-vacancies enhance the stress in the nanoparticles of ZnS. The average particle size of ZnS nanoparticles is around 15-20 nm. C. Optical studies: Fig. 3 (a) shows the UV-VIStransmission spectra of ZnS samples obtained in the the wavelength range 200 to 900 nm. The UV- VIS studies show the strong absorption by ZnS around 400 nm corresponding to the band gap. The optical energy band gap of the ZnS nanoparticles was determined by the following Tauc relationship [13] ( ℎ ) = (ℎ − ) where, α is the absorption coefficient, hυ is the photon energy in electron volts (eV), A is an energy independent constant, Eg is the band gap and m is constat, which determines the type of optical transmission (m=2 for indirect transition and m=1/2 for direct transition). The absorption coefficient can be approximately calculated from transmission spectrum using following equation: 1 1 = here d is the thin sample thickness and T is the percentage transmission. The variation of (αhυ)2 versus hυis shown in fig. 3(b) and the linear intercept on the horizontal gives the optical band gap Eg . The values of the optical band gap are estimated to be 4.87 eV, 4.89 eV and 4.91 eV for the nanoparticles grown using 2ml, 3ml and 4ml TEA, respectively. The values are higher that the reported bangap value of 3.8 eV perhaps due to the quantum confinement effect.


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Fig. 3(a) Transmission spectra of ZnS nanoparticles, 3(b) (αhυ)2 versus hυ plots. IV. CONCLUSIONS ZnS nanoparticles were synthesized using a simple chemical route using different volume of capping agent. SEM micrographs shows that the uniformly sized particles about 15-20 nm in size are obtained in all the cases. The cubic blende structure is determined using XRD study. Owing to optical properties the particles showed the blue shift. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

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