Studies on Structural and Optical Properties of Iron doped Cds Nanoparticles ABSTRACT

Transcription

1 Studies on Structural and Optical Properties of Iron doped Cds Nanoparticles Atheek P., Vidhya M. and Balasundaram O. N Department of Physics, PSG College of Arts & Science, Coimbatore, Tamil Nadu, India *Corresponding Author: p.atheek82@gmail.com ABSTRACT Cadmium Sulphide (CdS) Iron dopping is a novel technique of making semi conductors used in electronic devices. In the present study Iron doped CdS nano particles were prepared by chemical precipitation technique. It s structural (XRD & FTIR) and optical properties were studied. The particle size also calculated at 7-12 nm. The calculated band gap energy for various percentage of iron doped CdS was between ev. UV-Visible spectroscopy showed increasing percentage of Fe doped Cds with increasing band values. Key words: CdS, structural and optical properties, diffraction peaks INTRODUCTION Cadmium Sulphide is one of the important direct band II-VI semi conductors, which has a direct band gap of 2.42 ev. CdS nanocrystals are suitable for optoelectronic applications like laser light-emitting diodes, optical devices based on nonlinear properties, solar cells, quantum size effect semiconductors and electronic devices 1. Semiconductor nanocrystals exhibit quantum confinement effects when their size becomes comparable to the diameter of the bulk exciton, leading to splitting of the continuum of electronic energy levels into discrete states with the effective band gap energy blue shifted from that of the bulk. It is possible to manipulate the properties of nanomaterials for specific application of interest by carefully designing and controlling the parameters that affect their properties. Nanosized CdS particles have a wide band gap than the bulk CdS. In quantum dot CdS nanoparticles, the optical absorption edge shifts towards the lower wavelength side (blue shift). The increase of band gap with decreasing particle size may be due to quantum size effect. In addition to these advantages, quantum dots open up ways to utilize hot electrons and/or generate multiple charge carriers with a single photon. When a photon with energy greater than the band gap of the material is absorbed, the electron in the valance band is promoted to an excited state in the conduction band and the excited electrons are known as hot electrons. The characteristics of these materials are interesting from the PSGCAS Search: A Journal of Science and Technology Volume: 5 No. : 1 ISSN:

2 Studies on Structural And Optical Properties of Irondoped Cds Nanoparticles point of view of applications in infrared detectors, lasers and other optical devices 2,3,4 EXPERIMENTAL PROCEDURE The Cadmium Acetate Dihydrate (Cd(CH 3 COO) 2.2H 2 O), Sodium sulfide (Na 2 S.2H 2 O) and Iron (FeSo 4 ) purchased from the Merck were used as Cadmium, sulphur and dopant precursor respectively. Each 2 gm of Cd and S precursors were dissolved in ethanol in 2ml beaker separately and were added drop wise under vigorous stirring. Iron (FeSo 4 ) precursor [1% (mol)] was added into this solution after 3 minutes of vigorous 5g of Cd(CHOO) 2.. 2H 2 O + FeSO4 dissolved in 1 ml of Ethanol (Stirred for 1 hour) stirring. To this mixture, 12 ml of ethanol was further added and allowed for 8 hours stirring. The ph varying agent liquid ammonia (25 N) was added to fix the ph values at 9., 1. & 11.. The entire solution turned into deep green in color and further allowed to settle down for 12 hours, the optimized ageing period of the growth process. The dark green final products were centrifuged at 28rpm and washed thoroughly with the organic solvents (acetone, ethanol) and dried at 16 C in hot air oven and preserved in moisture free container (Fig. 1). 1g of Na 2 S.2H 2 O dissolved in 1 ml of Ethanol (Stirred for 1 hour) After 1 hour NH4OH was added until ph 9, 1 & 11 is obtained Stirred for 8 hours Green color precipitate was obtained Centrifuged for 28 rpm 2 minutes The sample was dried at 1C for four hours at hot air oven Cadmium sulphide was obtained Fig. 1 Flow Chart for Synthesis of Cadmium Sulfide PSGCAS Search: A Journal of Science and Technology Volume: 5 No. : 1 ISSN:

3 Atheek P., Vidhya M. and Balasundaram O. N FTIR Analysis of CdS Nanoparticle FTIR Analysis of the synthesized CdS Nanoparticle was measured for its FTIR property to assess its nature and confirm the compound formed. peak at 45 cm -1 also corresponded to the characteristic peak of CdS. RESULTS AND DISCUSSION Synthesis of iron doped cds nanoparticles with varying ph values The Iron doped CdS Nanoparticle synthesized was observed to be in green colour after the preparation steps and was further taken for analysis and characterization. FTIR Analysis of CdS Nanoparticle: FTIR analysis of the CdS Nanoparticle has been depicted in Fig.1. FTIR shows the absorption peak in the range of cm -1 attributed to the -OH group of water adsorbed on the samples. The weak absorption band at 1635cm -1 was assigned to CO 2 absorbed on the surface of the particles. Adsorption of water and CO 2 was a common property for all powdered samples exposed to atmosphere and are even more pronounced in case of nanosized particles with high surface area. Small peak near 4-47 cm -1 indicated the presence of CdS nanoparticles as this region was assigned to metal sulphur (M-S) bond. The Fig.1 Fourier Transforms Infrared Radiation X-ray diffraction analysis of CdS Nanoparticle at different ph The X-ray diffraction analysis (Fig. 2) was carried out for the samples at different ph; 1% Fe doped CdS (ph-9) (a), 1% Fe doped CdS (ph-1) (b), 1% Fe doped CdS (ph-11) (c). The XRD pattern shows 2θ values at , corresponding to (2) and (11) plane. The hexagonal phase of the prepared CdS samples is confirmed through the X-ray diffraction analysis which is well in accordance with the JCPDS card number (JCPDS 6-314). The crystalline sizes of the prepared samples are calculated using the Scherer formula D= Kλ / β cos θ. PSGCAS Search: A Journal of Science and Technology Volume: 5 No. : 1 ISSN:

4 Studies on Structural And Optical Properties of Irondoped Cds Nanoparticles Fig 2 [a] Fig 2 [b] Fig 2 [c] Fig.2[a-c] Calculated Grain Size Values for ph 5 1 and 11 of Fe Doped Cds Nanoparticle From XRD pattern analysis, it was found that the grain size for ph 9 was (a), ph 1 was 1.928(b) and for ph 11 is (c). It can be concluded that the grain size of the prepared samples was increased with increasing of ph for Fe doped CdS nanoparticle. A slight shift in peaks observed in the doped samples indicates incorporation of Fe ions in the crystal lattices. Synthesis of iron Doped Cds Nanoparticles with varying Percentage - values The UV absorption spectral analyses for the samples were observed in the range of 2 12 nm. The band gap energy was calculated from the spectrum using the formula, E g = hc\λeev. The band gap energy calculated for 5% Fe doped CdS, 1% Fe doped CdS, 15% Fe doped CdS at ph 11 PSGCAS Search: A Journal of Science and Technology Volume: 5 No. : 1 ISSN:

5 Atheek P., Vidhya M. and Balasundaram O. N Absorbance (a.u) % Fe 1% Fe 15% Fe Wavelenth (nm) Fig.3 Uv-Vis Spectrum Of 5%, 1% &15% Fe Doped Cds Nanoparticles were 2.58 ev, 3.79 ev, ev respectively (Fig. 3). The band gap values of the prepared samples were found to increase when compared to the bulk value (2.4 ev). The increase in the band gap values decreased the size of the nanoparticles which was well in accordance with the observed results. The 2 nd, 3 rd samples exhibited Blue shift by shifting towards the shorter wavelength side. The blue shift in the sample might have been due to the quantum confinement effect. X-ray diffraction analysis of Fe doped CdS Nanoparticles The X-ray diffraction analysis (Fig. 4) was carried out for 5% (a) Fe doped CdS, 1% (b) Fe doped CdS, 15% (c) Fe doped CdS nanoparticles prepared at ph11. The XRD pattern shows 2θ values at , corresponding to (2) and (11) plane. The hexagonal phases of the prepared CdS samples are confirmed through the X- ray diffraction analysis which is well in accordance with the JCPDS card number (JCPDS 6-314). The crystalline size of the prepared samples were calculated using the Scherer formula as D= Kλ / β cos θ. The crystalline sizes when were calculated, A slight shift was absorbed in the doped samples indicating the incorporation of ferrous ion in the crystal lattices. PSGCAS Search: A Journal of Science and Technology Volume: 5 No. : 1 ISSN:

6 Studies on Structural And Optical Properties of Irondoped Cds Nanoparticles Fig 4 [a] Fig 4 [b] Fig.4(a-c) Fig 4 [c] Calculated Grain Size Values for 5% 1% and 11% of Fe Doped Cds Nanoparticle CONCLUSION Visible Spectroscopy (UV-vis). In XRD Iron doped CdS nanoparticles have analysis, the average grain size of iron been prepared by chemical precipitation doped CdS nanoparticle was found to be 7- technique. The detailed characterization of 12 nm for varying ph values and 5-13nm for the nanoparticle was carried out by using X- varying dopant percentage values. The ray diffraction (XRD), Fourier Transmission sharpness of the diffraction peaks suggests Infrared Spectroscopy (FTIR) and UV- that the product was well crystallized. The PSGCAS Search: A Journal of Science and Technology Volume: 5 No. : 1 ISSN:

7 Atheek P., Vidhya M. and Balasundaram O. N FTIR spectrum exhibited the characteristic peaks of iron doped Cds nanaoparticles. UV-VIS spectroscopy showed an increase in band gap values with the increase in dopant percentage. REFERENCE 1. Zhang Y.,Wan J and Ke Y., 21. A Novel Approach of Preparing TiO2 films at...journal of Hazardous Materials, Vol. 177(1 3): MannaL., Scher EC. and Alivisatos A P., 22, Shape controlof colloidal semiconductor nanocrystals. Journal of ClusterScience, Vol. 13(4): MannaL., Scher E C. and Alivisatos A P., 2. Synthesis of Soluble and Processable rod-, arrow-, teardrop-, tetrapod-shaped Cds Nanocrystals. Journal of the American Chemical Society.Vol122, Nanda J., Been Annie Kuruvilla, and Sarma D D., Photoelectron Spectroscopic Study of CdS Nanocrystallites. Physical Review B, Vol.59:7473. PSGCAS Search: A Journal of Science and Technology Volume: 5 No. : 1 ISSN: