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Ewemen Journal of Synthetic Organic Chemistry

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Full Length Research

SYNTHESIS, CHARACTERIZATION OF ZIRCONIA DOPED AND UNDOPED CDSE NANOPARTICLES FOR PHOTOCATALYTIC DEGRADATION OF ORGANIC DYES

EMELDA R. AND *MUTHUCHUDARKODI R.R.

Department of Chemistry, V.O Chidambaram College, Tuticorin –628008, Tamilnadu, INDIA

ABSTRACT

Received 19 January, 2016 Revised on the 25 January, 2016 Accepted 28 January, 2016 *Corresponding Author’s Email: muthu.rajaram@gmail.com

Cadmium selenide, Zirconium doped cadmium selenide nanoparticles were successfully prepared by simple aqueous chemical method. Cadmium acetate [Cd(CH3COO)2] and sodium selenite [Na2SeO3] solutions were used as precursors. The prepared CdSe and Zr doped CdSe nanoparticles are characterized by XRD, PL, SEM, EDX and TEM. From XRD studies, the size of the pure CdSe nanoparticles was found to be 16nm and Zr doped CdSe nanoparticles was found to be 45 nm, calculated from Scherrer formula. The PL spectra of CdSe and Zr doped CdSe nanoparticles showed two peaks around 260 nm and another around 520 nm. PL spectra showed green emission at 520 nm. The morphological studies of the nanoparticles revealed the flower like structure. The energy dispersive analysis confirmed the presence of Zr in CdSe lattice. The nanostructures of the product were characterized with Transmission Electron Microscopic studies and the structure was found to be rod which clearly indicates the presence of CdSe and Zr doped CdSe nanoparticles. The effect of initial dyes and nanoparticle concentrations on the photocatalytic activity has been studied and the results demonstrated that the dye photodegradation follows pseudo-first-order kinetics. The observed maximum degradation efficiency of Zirconia doped CdSe nanoparticles was found to be 92%. Keywords: SEM, EDX, XRD, nanoparticles

INTRODUCTION

At present, a large part of pollution in the public water systems is caused by the industries. Among the chemical contaminants, dyes and dyes intermediates, surfactants and some traces of metals are the objects of major interest in the preservation of the environment. About 10–15% of all the dyes are directly lost to wastewater in the dyeing process

(Oturan, 2008). Thus, the wastewater must be treated before releasing it into the natural environment (Parshetti et al., 2006). These dyes create serious environmental hazards and pollution by releasing toxic and potential carcinogenic substances into the aqueous phase (Kansal et al., 2007). Various chemical and physical processes, such as chemical

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precipitation, coagulation, electrocoagulation, adsorption, air stripping, flocculation, coronation, chlorination, ultra filtration, reverse osmosis, etc., are applied for colour removal from textile effluents (Barjasteh-Moghaddam, 2011). But these processes lead to non-biodegradable contaminations which give rise to new types of pollutants and need to be further treated (Modirshahla et al., 2006). Such textile effluents are Safranin and Crystal Violet. Semiconducting materials are used in the field of optoelectronic devices such as light emitting diode, photovoltaic cells, solar cells, photo detector, high density magnetic information storage, biosensors (Colvin et al., 1994). Cadmium selenide nanoparticles are the most important group of II-VI semiconductors. This material has been widely used for photoelectric devices (RaniBala Devi et al., 2013). The direct band gap of CdSe nanoparticles are 1.74 eV and electron mobility of 450-900 cm2/vs (Jaspal Singh et al., 2011). A variety of technical methods have been widely used in the synthesis of nonmaterial and nanostructures. Ethylene glycol was used as an organic capping agent in case of CdSe nanoparticles. Na2SeO3 is used as the Se source in the synthesis of CdSe nanoparticles (Peng et al., 2005). Synthetic route for CdSe was extended further to produce transition metal doped CdSe nanoparticles. It has been evidenced that the transition metal doped semiconductors behave as improved DMS. The evidence of DMS is available in literature (Hanif et al., 2002). Sunil Kumar et al. (2012) had studied Co doped CdSe and Ni doped CdSe nanoparticles In photocatalysis process, under UV irradiation, semiconductor particles absorb photon of light more energetic than its band gap. In this circumstance, the electrons in semiconductor materials excited from the valence band to conduction band and charge carriers are generated (electrons/holes). These charge carriers (holes) are responsible for the oxidation and formation of hydroxyl radicals (Carlos et al., 2000). The hydroxyl radical possesses inherent properties that enable it to attack refractory organic pollutants in water to possibly obtain a complete mineralization compared to other semiconductor photocatalysts (Wen et al., 2010). In the present work, an attempt has been made to synthesize pure CdSe nanoparticles and Zr ion doped CdSe nanoparticles by simple aqueous wet chemical method. And degradation of safranin and crystal

violet dyes were studied using doped and undoped CdSe nanoparticles with the combination of different processes, viz., UV/CdSe, and UV/doped CdSe. The effects of the operating parameters catalyst loading and initial dye concentration on degradation rate were also evaluated. Finally, kinetics study was also performed by varying operating conditions of the system. MATERIALS AND METHODS Materials

Cadmium acetate [Cd (CH3COO)2.2H2O], Dimethyl formamide (DMF), Polyethylene glycol(PEG), Sodium selenite (Na2SeO3), Zirconium oxychloride were supplied by Aldrich. All materials were used without further purification. Preparation of CdSe nanoparticles

CdSe nanoparticles were synthesized by aqueous chemical method using cadmium acetate and sodium selenite as precursors. All the steps of the synthesis were performed at low temperature and ambient conditions. 2.0 g of cadmium acetate dihydrate and 50 mL of dimethylformamide are stirred in an ambient atmosphere to make a solution. To this solution 1.0 mL of polyethylene glycol solution was mixed with constant stirring and then 1.0 g of sodium selenite dissolved in 10 mL of double distilled water added into the solution. The resulting solution was stirred for 30 min by a magnetic stirrer and further refluxed for 3hrs at ~80°C without stirring. The size selective precipitation was carried out using acetone as a non-solvent. The resulting white precipitate was washed five times in methanol and then the wet precipitate was dried and used (Fujishima et al., 1972). Preparation of Zr ion doped CdSe nanoparticles

Two grams (2.0 g) of cadmium acetate dihydrate and 50 mL of DMF were stirred to make a solution. To this solution 1.0 mL of PEG and 1% of zirconium oxychloride solution was mixed with constant stirring. And 10mL of separately prepared solution of sodium selenite was added drop by drop.The resulting solution was stirred for 30min using a magnetic stirrer and further refluxed for 3 hrs at ~80° without stirring. The white precipitate was settled down.The size selective precipitate was carried out using acetone as a non-solvent. The resulting mixture

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was filtered and washed with methanol for five times. Then the wet precipitate was dried and used (Shuo Liu et al., 2008). (CH3COO) 2Cd.2H2O +Na2SeO3 CdSe+2CH3COOH+2NaOH+H2O

Photocatalytic measurements

The photocatalytic activity of CdSe and Zr: CdSe nanoparticles were examined by studying the degradation of Crystal Violet (CV) dye [C25N3H30Cl] aqueous solution under laboratory made UV-photoreactor. For a typical photocatalytic experiment, 12 mg of the prepared sample was added to 100 mL of 0.1 g of Crystal Violet dyes aqueous solution. The prepared sample was dispersed under ultrasonic vibration for 10 min. The aqueous suspension was put under constant stirring in dark for 1 hr, so that the CV dyes are adsorbed on the surface of nanoparticles. The stable suspension was then exposed to the UV- radiation with continuous magnetic stirring. About 10 mL of suspension solution was taken out after every 10 min of UV light exposure. The photo degradation of CV dyes mixed with each synthesized samples were examined using UV-Vis absorption peaks (Zhihong Jing et al., 2013). Characterizations

The solution of the metal doped and undoped CdSe nanoparticles in water was used for recording the UV-VIS spectra. For recording the UV-Visible absorption spectra, a computer controlled JascoV-500 spectrophotometer was used. The X-ray diffraction (XRD) patterns were recorded for the powdered materials using a BRUKER AXS (D8 ADVANCE) X-ray diffractometer. EDAX and SEM measurements were carried out by JEOL JSM-6360F field emission scanning electron microscope. TEM images were recorded using Philips CM 200 model with the operating voltage range of 20-200 and with a resolution of 2.4Ao. RESULTS AND DISCUSSION:

XRD Analysis

Figure 1a shows the XRD pattern of the CdSe nanoparticles. The broad peaks entail that the

nanoparticle size was very small. The diffraction peaks at around 32.7°corresponding to (111) planes of cubic type CdSe. The crystallite size of the CdSe nanoparticles was found to be 16 nm. The XRD pattern of Zr ion doped CdSe nanoparticles are shown in Figure 1b and the diffraction peaks at 2θ values of 23.9°, 29.8°, 32.5°, 46.9° and 57.3°. The peaks were identified to originate from (111), (102), (200), (112) and (200) planes. The sharp diffraction peaks confirmed the high crystallinity of the synthesized nanoparticles. The crystallite size of the Zr ion doped CdSe nanoparticles was found to be 45 nm. All the peaks were indexed and found to be well matched to wurtzite structure of CdSe having hexagonal phase.

Figure 1: XRD pattern of (a) CdSe nanoparticles (b) Zr:

CdSe nanoparticles

PL Studies

To investigate the luminescence properties, the Photo luminescence spectra of nanoparticles are performed.PL investigation evidenced the high crystalline nature of the CdSe nanoparticles. The excitation and emission spectra of pure CdSe, Zr ion doped CdSe was obtained in the wavelength range of 200 – 800 nm.

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PL spectra of nanoparticles were presented in Figures 2a and 2b. The primary broad emission peak at 260nm and the secondary sharp emission peak at 520 nm were observed for CdSe. The emission wavelength namely 520 nm was due to green emission (Sayilkan et al., 2007), this might be due to the interaction between Zr ion and CdSe.

Figure 2: PL spectrum of (a) CdSe nanoparticles (b) Zr:

CdSe nanoparticles

SEM Analysis

Scanning Electron Microscope was employed to analyze the morphology and the growth features of the as prepared nanoparticles. Figures 3a and 3b shows the SEM micrographs of pure CdSe and Zr ion doped CdSe nanoparticles. The surface morphology of CdSe nanoparticles exhibits flower like structure andZr ion doped CdSe nanoparticles exhibits bundle of rods like structure.

EDAX Analysis:

The chemical compositional analysis of the CdSe nanoparticles and Zr ion doped CdSe nanoparticles has been carried out using EDAX analysis. The strong peaks observed in the spectrum are related to Cd and Se. The elemental constitution of cadmium selenide nanoparticles with two major peaks was found to have atomic percentage at 25.81% of Cd and 37.84% of Se as shown in Figure 3a. EDAX Spectrum of Zirconium ion doped cadmium selenide nanoparticles are shown in Figure 3b. Zr ion doped CdSe nanoparticles were found to have atomic percentage 34.2% of Cd, 35.6% of Se and 12.2% of Zr. The above observations confirmed the respective elements in the synthesized CdSe and Zr ion doped CdSe nanoparticles. TEM Analysis

TEM analysis was carried out for Zr ion doped CdSe nanoparticles is shown in Figure 4a. The morphology of the synthesized Zr ion doped CdSe nanoparticles was found to be rod like appearance. It shows the size to be in nanometer range. The selection Area Electron Diffraction (SAED) pattern shows the particle size is observed to be 100 nm for Zr ion doped CdSe nanoparticles as shown in Figure 4b. Photocatalytic Activity

The photocatalytic activity of transition metal doped CdSe nanoparticles was examined through the degradation of crystal violet dye in aqueous solution by UV-Visible spectrophotometer. When a photon of UV light strikes the metal doped CdSe nanoparticles surface an electron (e-) from its valence band jumps to the conduction band leaving behind a positively charged hole (h+) in valence band. The photocatalytic active centers are formed on the surface of metal doped CdSe due to increase negative charge in the conduction band. The valence band hole (h+) reacts with the chemisorbed H2O molecules to form reactive species such as OH radicals, which subsequently react with dye molecules to cause their complete degradation.

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Figure 3: SEM and EDAX pattern of (a) CdSe Nanoparticles (b) Zr: CdSe nanoparticles .

Figure 4: (a) TEM image of Zr: CdSe nanoparticles, (b)SAED pattern of Zr: CdSe nanoparticles

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Photocatalytic degradation of Crystal violet dye in the presence of doped and undoped CdSe nanoparticles

The UV visible absorbance values of pure crystal violet dye solution shows maximum wavelength at 586nm. The characteristic absorption value at 586nm was used to track the photocatalytic degradation process. It can be clearly noticed from the recorded absorbance values that there was no significant changes of the concentration of crystal violet after 3.0 hrs UV irradiation, which indicated that pure crystal violet dye solution cannot be easily degraded by UV light as shown in Figure 5a. The degradation efficiency of pure crystal violet dye was about 42% at 3.0 hrsfor UV irradiation. The results of the photocatalytic degradation of an aqueous solution of crystal violet with synthesized nanoparticles of CdSe and Zr ion doped CdSe are shown in Figure 5b & 5c. It can be seen that the maximum absorption band of crystal violet solution at λ = 586nm was completely disappeared after 60min of UV irradiation with nanoparticles. As a consequence, the absorption intensity decreased due to decolouration of the dye. Figure 6a shows the bleaching of crystal violet dye on photodegradation in the presence of CdSe nanoparticles and Zr ion doped CdSe nanoparticles as photocatalyst. The degradation efficiency was higher in the presence of Zr ion doped CdSe nanoparticles than CdSe nanoparticles. The photocatalytic bleaching was faster in case of Zr ion doped CdSe nanoparticles and almost completed after 60 min. The degradation

efficiency of metal doped CdSe nanoparticles was increased with increasing irradiation time due to the function of UV light. It was observed that the maximum degradation efficiency of crystal violet dye within 60min irradiation time was about 53% and 92% for CdSe nanoparticles and Zr ion doped CdSe nanoparticles. Therefore, it is observed that the Zr ion doped CdSe nanoparticles possessed high photocatalytic activity. The results showed that Zr deposited on the surface of CdSe is more efficient. The decolourization rate constant was determined from ln (C0/ C) = - kt Where Co is the initial concentration of the dye and C is the concentration of the dye after irradiation in selected time interval t. k is the apparent first-order rate constant. A plot of ln Co/C versus time represents a straight line, the slope of which on linear regression equals the apparent first-order rate constant k. The correlation constant for the fitted line was calculated to be 0.958 and 0.970 for CdSe and Zr: CdSe nanoparticles, respectively. From Figure 6b the rate constants were calculated to be 0.012 and 0.041 min-1 for CdSe and Zr: CdSe, respectively. Accordingly the metal loaded semiconductors possess greater photocatalytic activity than pure semiconductors. Therefore, the colour removal rate was increased significantly by using Zr: CdSe as a catalyst.

Figure.5 (a) UV-Vis absorption spectrum of crystal violet dye

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Figure.5.UV-Vis absorption spectra of crystal violet dye in the presence of (b) CdSe and (c) Zr ion CdSe nanoparticles

Figure.6 (a) Degradation efficiency of crystal violet dye catalyzed by CdSe and Zr: CdSe nanoparticles

Figure. 6 (b) Pseudo-first-order plots for the kinetics of Photodegradation of crystal violet dye in Zr: CdSe (a)

and (b) CdSe Nanoparticles.

Table 1: Degradation efficiency of pure Crystal violet dye

Time (min) Degradation (%) Degradation Efficiency (%) pure Crystal violet dye CdSe Nanoparticles Zr ion doped CdSe Nanoparticles Initial 0 - - 10 - 13 54 20 - 14 73 30 - 24 80 40 - 34 81 50 - 42 85 60 (1 hr) 24 53 92 120 (2 hrs) 32 - - 180 (3 hrs) 41 - -

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CONCLUSION

CdSe nanoparticles were prepared by simple chemical route. XRD study clearly reveals that Zr-doped CdSe nanoparticles possess wurtzite structure. The average crystalline size of CdSe nanoparticle is 16 nm and 45 nm for Zr ion doped CdSe nanoparticles. In PL spectra, peaks were observed at 260 and 520 nm. The emission wavelength namely 520 nm is due to the green emission. SEM studies show the bundle of rod like morphology in the case of Zr-doped CdSe nanoparticles. The nanostructure Zr:CdSe exhibits very high photocatalytic activity under UV irradiation.

The photocatalytic degradation of crystal violet dye was more effective with Zr:CdSe nanoparticles. ACKNOWLEDGEMENT

The authors are extremely grateful to Department of Science and Technology (FAST TRACK and FIST) New Delhi, Jasco UV-VISIBLE Spectrophotometer at V.O.C.College, Tuticorin-8. CONFLICT OF INTEREST

None declared. REFERENCE:

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Article Citation: Emelda R and Muthuchudarkodi RR (2016). Synthesis, characterization of Zirconia doped and undoped CdSe nanoparticles for photocatalytic degradation of organic dyes. Ew J Syn Org Chem 1(1): 1 – 8.