Synthesis, Morphological Characterization and Photocatalytic Property

Mechanics, Materials Science & Engineering, May 2017 – ISSN 2412-5954

Synthesis, Morphological Characterization and Photocatalytic Property of Silver Molybdate2 S. Muthamizh1, S. Munusamy1, S. Praveen Kumar1, V. Narayanan1,a 1 – Department of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai, India a – vnnara@yahoo.co.in DOI 10.2412/mmse.94.18.722 provided by Seo4U.link

Keywords: Ag2MoO4, microcubes, photocatalyst.

ABSTRACT. Silver molybdate (Ag2MoO4) microcubes were synthesized by simple and cost effective precipitation method by reacting 1:1 mole ratio of silver acetate and ammonium molybdate. The synthesized nanoparticles were characterized byXRD, Raman and DRS-UV spectroscopy, morphology of the Ag2MoO4 was investigated by FE-SEM analysis. The XRD pattern reveals that the synthesized Ag2MoO4 has cubic structure. In addition, by using the XRD data lattice parameter values also calculated. The Raman analysis of Ag2MoO4 confirms the presence of Ag-O and Mo-O bonds in synthesized microcubes. FE-SEM analysis revels that the synthesized Ag2MoO4 has cube like morphology. The optical property of Ag2MoO4 microcubes were carried out by DRS UV-Visible spectroscopy. The synthesized Ag2MoO4 was utilized for the degradation of organic dye under visible light irradiation.

Introduction. Transition metal-based molybdates nanostructures (M = Fe, Ni, Co, Ag, Mn etc., ) are considered as an important inorganic material which are widely explored in various applications such as Li-ion storage batteries, [1] supercapacitors, [2] optical fibers, [3] photoluminescence, [4] photocatalyst, [5] humidity sensors, [6] magnetic properties and catalysts. [7] However, low dimensional metal molybdates have attracted more interest in recent years. In particular, silver molybdate (Ag2MoO4) has attracted considerable attention because of its unique properties such as, photoluminescence environmental friendly, excellent antimicrobial activity, high electrical conductivity, good photocatalytic activity and extraordinary electrochemical energy storage performance. Due to these properties, the Ag2 MoO4 is potentially used in several applications including ion-conducting glasses, gas sensor, antibacterial material, photo switches and ceramics. In photocatalysis, Ag2MoO4 has paid significant attention owing to its photosensitivity which make this material with high photocatalytic activity under UV or visible-light irradiation. Recent literature is reported based on Ag2MoO4 and its composite that act as a photocatalyst for the degradation of organic dyes into the wastewater. [8] The photocatalytic activity mainly depends on the crystal and electronic structures of materials that affect the energy band structure and the efficiency of charge carrier transfer. Moreover, to improve their physicochemical properties of the photocatalyst, researchers have developed a number of attempt to obtain the different morphologies of Ag2 MoO4 including nanoparticles, nanorods, nanowires, wire-like nanostructures, nanoclusters, broom-like, flower-like microstructures and microcrystals.

Experimental.

Reagent. Silver nitrate, ammonium molybdate and methylene blue were purchased from Qualigens and used as received. Other chemicals used were of analytical reagent grade. Double distilled water was used thought the experiment. All chemicals were used without further purification.

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© 2017 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

MMSE Journal. Open Access www.mmse.xyz

Mechanics, Materials Science & Engineering, May 2017 – ISSN 2412-5954

Synthesis of Ag2MoO4 nanoparticles. Ag2MoO4 microcubes were prepared via co-precipitation reaction in aqueous media by addition of Ag+ solution, in molybdate solution under vigorous stirring.

When the mixing process was completed, the formed Ag2MoO4 suspension was filtered and washed with distilled water and ethanol for three times and then dried in oven at 90 °C for 2 h. In order to form crystalline Ag2 MoO4 particles, the prepared samples were annealed at 600 °C. Instrumentation. The XRD pattern of the synthesized sample was analyzed by using Rich Siefert 3000 diffractometer with CuKα1 radiation (λ =1.5406 Å). Raman spectrum was recorded using laser Raman microscope, Raman-11 Nanophoton Corporation, Japan. DRS UV–Vis absorption spectrum was recorded using a Perkin–Elmer lambda 650 spectrophotometer. The morphology of synthesized Ag2MoO4 was analyzed by HITACHI SU6600 Field Emission Scanning Electron Microscopy (FESEM) coupled with EDAX. Result and discussion.

XRD analysis. Synthesized Ag2MoO4 was subjected to XRD analysis in order to confirm the phase, crystal structure and the lattice parameter of the sample. The obtained XRD pattern is shown in Fig. 1it is well matched with cubic phase of JCPDS Card No 00-08-0473 with space group of Fd-3 m (227).The sharp peaks indicate the high crystalline nature of the sample without any impurities.

Fig. 1. XRD pattern of Ag2MoO4 microcubes.

Raman analysis. Ag2MoO4 was subjected to Raman analysis, which is shown in Fig. 2. The band region from 872-926 cm−1 with high intensity is due to the symmetric stretching of Mo–O bond in [MoO4]. Asymmetric bending mode of MoO4 falls under the region of 357–372 cm−1. 357–372 and 282–297 cm−1 are corresponds to Asymmetric and symmetric bending of MoO4 in Ag2 MoO4. [9]

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Mechanics, Materials Science & Engineering, May 2017 – ISSN 2412-5954

Fig. 2. Raman spectrum of Ag2MoO4 microcubes.

DRS-UV. Synthesized Ag2MoO4 was subjected to DRS-UV–Vis analysis to examine the optical property and to find out the band gap of the material. Observed spectrum is shown in Fig. 3 and the inset shows the band gap plot of Ag2MoO4. The band gap value (Eg) of micro cubes was determined by using Tauc's plot. (hυα)1/n=A (hυ-Eg) where h – Planck's constant, ν – frequency of vibration, α – absorption coefficient, Eg – band gap, A – proportional constant. n = 2 (for direct band gap), or n = 1/2 (for indirect band gap).

The synthesized Ag2MoO4 showed band gap of band gap of 2.87 eV which is shown in Fig. 3.

Fig. 3. DRS-UV–Vis spectrum of Ag2MoO4 micro cubes. Inset shows the Tauc's plot.

Morphological analysis. Synthesized Ag2MoO4was subjected to FE-SEM analysis in order to confirm the shape and size of the particles. Fig. 4 shows the image of Ag2MoO4 which resembles the cubes shape with size in micro meter.

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Mechanics, Materials Science & Engineering, May 2017 – ISSN 2412-5954

Fig. 4. FE-SEM image of Ag2MoO4 microcube.

Photocatalytic activity. The photocatalytic activity of the fabricated pure Ag2MoO4 investigated on the degradation of organic dyes Methylene blue (MB) shown in Fig. 5. 25 mg of photocatalyst was taken and transferred into a beaker which contains 100 mL of 1 × 10−5 M MB solution. Prior to light exposure, the mixture of dye and photocatalyst was kept under dark in order to attain adsorption– desorption equilibrium between the photocatalyst and dye. After 30 min the reaction mixture is exposed to visible light under constant magnetic stirring. The reaction mixture was collected every 10 min and subjected to UV–Vis analysis. It can be seen that the intensity of the absorption peaks decreased as the reaction progressed with Ag2MoO4 microcube as the catalyst.

Fig. 5. Absorption spectra of aqueous MB solution at 60 min during photodegradation by using Ag2MoO4 microcube as a photocatalyst.

Summary. Ag2MoO4 microcube were synthesized by simple precipitation method. The phase and crystal structure of the Ag2MoO4 microcube nanoparticles was characterized byXRD and Raman spectroscopy. The optical property of Ag2MoO4 examined by DRS-UV spectroscopy. The morphology of the Ag2MoO4 microcube was confirmed by FE-SEM analysis. The synthesized micro cubes were employed for the degradation of methylene blue dye.

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Mechanics, Materials Science & Engineering, May 2017 – ISSN 2412-5954

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