Catalysis and Nanomaterials Research Laboratory

Chennai, India

Catalysis and Nanomaterials Research Laboratory

Chennai, India
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Clament Sagaya Selvam N.,Catalysis and Nanomaterials Research Laboratory | Vijaya J.J.,Catalysis and Nanomaterials Research Laboratory | Kennedy L.J.,Vellore Institute of Technology
Industrial and Engineering Chemistry Research | Year: 2012

ZnO nanomaterials with different morphologies such as nanoflakes, spherical nanoparticles (SNPs), and nanorods have been synthesized via a simple low temperature coprecipitation method. The concentration of the capping agent is a key factor in the morphological control of ZnO nanostructures. Triton X-100 micelles were found to be single molecules at low concentration but spherical and rod-like shaped micellar aggregation at higher concentrations. The formation of different morphologies of ZnO was confirmed by HR-SEM and HR-TEM. XRD data showed the formation of single-phase ZnO with the wurtzite crystal structure. The influence of Zr contents on the structure, morphology, absorption, emission, and photocatalytic activity of ZnO SNPs was investigated systematically. The influence of the ZnO morphologies on the photocatalytic degradation (PCD) of resorcinol as a model reaction is evaluated and discussed in terms of particle size, surface area, crystal growth habits, and oxygen defects. The results indicated that the particle size is an important factor for the PCD, and thus, the 1.5 wt % Zr-doped ZnO SNPs show superior performance toward PCD of resorcinol than other samples due to the small particle size distribution. Furthermore, the effect of different photocatalytic reaction parameters on the resulting PCD efficiency of ZnO SNPs was investigated. © 2012 American Chemical Society.


Ragupathi C.,Catalysis and Nanomaterials Research Laboratory | John Kennedy L.,Vellore Institute of Technology | Judith Vijaya J.,Catalysis and Nanomaterials Research Laboratory
Advanced Powder Technology | Year: 2014

The present study reports a green chemistry approach for the biosynthesis of nano-zinc aluminate by a microwave method using high purity metal nitrates and aloe vera plant extract. Aloe vera extract simplifies the process and provides an alternative process for a simple and economical synthesis of nanocrystalline zinc aluminate. It is prepared by conventional and microwave method by with and without using the plant extract for comparison purpose. The obtained nanomaterials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), high resolution transmission electron microscopy (HR-TEM) diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. The XRD confirmed the formation of cubic structure of zinc aluminate. The formation of zinc aluminate phase is also confirmed by FT-IR. The change in morphology from nanorods to nanosheets from the conventional method to microwave method is clearly shown by HR-SEM. The optical properties were determined by DRS and PL spectra. © 2013 The Society of Powder Technology Japan. Published by Elsevier B.V.


Selvam N.C.S.,Catalysis and Nanomaterials Research Laboratory | Kumar R.T.,Catalysis and Nanomaterials Research Laboratory | Kennedy L.J.,Vellore Institute of Technology | Vijaya J.J.,Catalysis and Nanomaterials Research Laboratory
Journal of Alloys and Compounds | Year: 2011

Magnesium oxide (MgO) was synthesised by a simple microwave-assisted combustion route without using any template, catalyst or surfactant. For the purpose of comparison, it was also prepared using conventional method. The as-synthesized MgO was characterized by powder X-ray diffraction (XRD), Fourier Transform infrared spectra (FT-IR), high resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), Energy Dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy. The XRD results confirmed the formation of cubic phase MgO. FT-IR was used to investigate the adsorption of water and CO2 on MgO surface and confirm the formation of Mg-O phase. The formation of MgO micro cubes structures was confirmed by HR-SEM. The formation of MgO nanosheets was confirmed by HR-SEM and TEM and their possible formation mechanisms were also proposed. The optical absorption and photoluminescence emissions were determined by DRS and PL spectra respectively. An attempt has been made to compare the lattice parameter and the PL intensity. © 2011 Elsevier B.V.


Manikandan A.,Catalysis and Nanomaterials Research Laboratory | Judith Vijaya J.,Catalysis and Nanomaterials Research Laboratory | John Kennedy L.,Vellore Institute of Technology | Bououdina M.,University of Bahrain
Journal of Molecular Structure | Year: 2013

Nano-sized copper doped zinc ferrite powders, Zn1-xCu xFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized by microwave combustion method. The structural, morphological and magnetic properties of the products were determined and characterized in detail by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometer (VSM). X-ray analysis showed that all compositions crystallize with a cubic spinel-type structure. The lattice parameter decreased from 8.443 to 8.413 Å with increasing Cu content. The average crystallite size was found in the range of 41.20-45.84 nm. Magnetic measurements revealed that for lower Cu concentration (x ≤ 0.2), the system shows a superparamagnetic behavior whereas for higher concentration (x ≥ 0.2), it becomes ferromagnetic. It has been explained in terms of random distribution of Zn2+ and Fe 3+ ions at tetrahedral [A] and octahedral [B] sites. The saturation magnetization (Ms) varies considerably with Cu content to reach a maximum value for Cu0.5Zn0.5Fe2O4 composition, i.e. 58.58 emu/g. The high saturation magnetization of these samples suggests that this method is suitable for preparing high quality nanoparticles for magnetic applications. The broadband visible emission is observed in the entire photoluminescence (PL) spectrum and the estimated energy band gap is about 2.1 eV. The composition with x = 0.5 showed the highest intensity and was explained on the basis of disordered cluster model. © 2012 Elsevier B.V. All rights reserved.


Manikandan A.,Catalysis and Nanomaterials Research Laboratory | Judith Vijaya J.,Catalysis and Nanomaterials Research Laboratory | John Kennedy L.,Vellore Institute of Technology
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2013

Nickel oxide (NiO) nano- and microstructures were synthesized by the microwave combustion method (MCM) and the conventional combustion method (CCM) using urea as the fuel. The as-synthesized NiO powders were characterized by X-ray powder diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, Brunauer-Emmett-Teller (BET) analysis and vibrating sample magnetometer (VSM) analysis. The XRD results confirmed the formation of cubic phase NiO. The formation of NiO nano- and microstructures were confirmed by HR-SEM and HR-TEM and their possible formation mechanisms were also proposed. The optical absorption and photoluminescence emissions were determined by DRS and PL spectra respectively. The band gap was measured using the Kubelka-Munk model and it shows 3.36 eV for NiO (MCM) and 2.70 eV for NiO (CCM). The magnetic properties of the synthesized NiO nano- and microstructures were investigated with a vibrating sample magnetometer (VSM) and their hysteresis loops were obtained at room temperature. The relatively high saturation magnetization (21.22 emu/g) of NiO-MCM shows that it is ferromagnetic and low saturation magnetization (7.43 emu/g) of NiO-CCM confirms the superparamagnetic behavior. © 2013 Elsevier B.V.


Ragupathi C.,Catalysis and Nanomaterials Research Laboratory | Vijaya J.J.,Catalysis and Nanomaterials Research Laboratory | Kennedy L.J.,Vellore Institute of Technology
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2014

Microwave combustion method (MCM) is a direct method to synthesize NiAl2O4 nanoparticles and for the first time we report the using of Sesame (Sesame indicum L.) plant extract in the present study. Solutions of metal nitrates and plant extract as a gelling agent are subsequently combusted using microwave. The structure and morphology of NiAl2O4 nanoparticles are investigated by X-ray diffraction (XRD), Fourier transforms infrared spectra (FT-IR), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), high resolution transmission electron microscopy (HR-TEM), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy, Brunauer-Emmett- Teller (BET) analysis and vibrating sample magnetometer (VSM). XRD pattern confirmed the formation of cubic phase NiAl2O4. The formation of NiAl2O4 is also confirmed by FT-IR. The formation of NiAl2O4 nanoparticles is confirmed by HR-SEM and HR-TEM. Furthermore, the microwave combustion leads to the formation of fine particles with uniform morphology. The magnetic properties of the synthesized NiAl2O4 nano and microstructures were investigated by vibrating sample magnetometer (VSM) and their hysteresis loops were obtained at room temperature. Further, NiAl2O4 prepared by MCM using Sesame (S. indicum L.) plant extract is tested for the catalytic activity toward the oxidation of benzyl alcohol. © 2014 Elsevier B.V.


Manikandan A.,Catalysis and Nanomaterials Research Laboratory | Kennedy L.J.,Vellore Institute of Technology | Bououdina M.,University of Bahrain | Vijaya J.J.,Catalysis and Nanomaterials Research Laboratory
Journal of Magnetism and Magnetic Materials | Year: 2014

Spinel zinc ferrite (Zn1-xCoxFe2O 4) nanoparticles with various particle sizes were prepared by the microwave combustion method using urea as a fuel. The composites were prepared with the addition of cobalt at different molar ratios (x=0.0 to 0.5) to ZnFe2O4. The obtained spinel ferrites were characterized by X-ray powder diffraction (XRD) and their mean grain size and morphology were determined by the high resolution scanning electron microscopy (HR-SEM). The magnetic properties of the synthesized ferrites were investigated using room temperature vibrating sample magnetometer (VSM) and their hysteresis loops were obtained. The optical reflectance and photoluminescence (PL) emissions were determined by UV-visible diffuse reflectance spectra (DRS) and PL spectra respectively. The formation of single cubic spinel phase was confirmed by XRD and Rietveld analysis with an average crystallite size is in the range of 43-49 nm. The broadband visible emission band is observed in the entire PL spectrum and the estimated energy band gap is about 2.1 eV. The variation of saturation magnetization (Ms) value of the samples was studied. The prepared lower compositions (0.0, 0.1 and 0.2) show a superparamagnetic behavior and the higher compositions (0.3, 0.4 and 0.5) show a ferromagnetic behavior with hysteresis and that the Ms increases with increasing Co content to reach a maximum value of 65.20 emu/g for Zn0.5Co0.5Fe 2O4. The relatively high Ms of the samples suggests that this method is suitable for preparing high-quality nanocrystalline magnetic ferrites for practical applications. Different mechanisms to explain the obtained results and the correlation between magnetism and structure are discussed. © 2013 Elsevier B.V. All rights reserved.


Manikandan A.,Catalysis and Nanomaterials Research Laboratory | Judith Vijaya J.,Catalysis and Nanomaterials Research Laboratory | John Kennedy L.,Vellore Institute of Technology | Bououdina M.,University of Bahrain
Ceramics International | Year: 2013

Pure and strontium doped zinc ferrite (Zn1-xSr xFe2O4) nanoparticles were prepared by the microwave combustion method using urea as the fuel. Rietveld refinements of X-ray diffraction pattern confirm the formation of single cubic spinel phase with an average crystallite size in the range of 25-42 nm. The broad visible emission band is observed in the entire photoluminescence spectrum. The estimated band gap energy is found to decrease with increasing Sr content, i.e. 2.1-1.72 eV. Magnetic measurements at room temperature revealed that at lower Sr concentration (x≤0.2), the system shows a superparamagnetic behavior, whereas at higher Sr concentration (x≥0.2), it becomes ferromagnetic. The relatively high saturation magnetization of the as-prepared Sr-doped ZnFe 2O4 nanoparticles suggest that this method is suitable for preparing high-quality nanocrystalline magnetic ferrites for practical applications. The mechanism for the formation of ZnFe2O4 by the microwave combustion method is also discussed in the present study. Microwave combustion produced sufficient energy for the formation of ZnFe 2O4, because of its homogeneous distribution within the raw materials. This results in the formation of nanoparticles and early phase formation within few minutes of time. © 2013 Elsevier Ltd and Techna Group S.r.l.


Clament Sagaya Selvam N.,Catalysis and Nanomaterials Research Laboratory | Judith Vijaya J.,Catalysis and Nanomaterials Research Laboratory | John Kennedy L.,Vellore Institute of Technology
Journal of Colloid and Interface Science | Year: 2013

A simple, low temperature co-precipitation method was developed to synthesize ZnO nanomaterials with different morphologies such as nanoflakes, spherical nanoparticles (SNPs), and nanorods. The concentration of the capping agent, Triton X-100, is a key factor in the morphological control of ZnO nanostructures. The formation of different morphologies of ZnO was confirmed by HR-SEM and HR-TEM. XRD data showed the formation of single-phase ZnO with the wurtzite crystal structure. The influence of La contents on the structure, morphology, absorption, emission, and photocatalytic activity of ZnO SNPs was investigated systematically. The influence of the ZnO morphologies on the photocatalytic degradation (PCD) of Bisphenol A (BPA) as a model reaction is evaluated and discussed in terms of surface area, crystal growth habits, particle size, and oxygen defects. The results indicated that the particle size is an important factor for the enhancement of PCD. Furthermore, the effect of different photocatalytic reaction parameters on the resulting PCD efficiency of ZnO SNPs was investigated. © 2013 Elsevier Inc.


Selvam N.C.S.,Catalysis and Nanomaterials Research Laboratory | Manikandan A.,Catalysis and Nanomaterials Research Laboratory | Kennedy L.J.,Vellore Institute of Technology | Vijaya J.J.,Catalysis and Nanomaterials Research Laboratory
Journal of Colloid and Interface Science | Year: 2013

ZrO 2 nanocrystals were synthesized by the microwave combustion method (MCM) using urea as the fuel without using any template, catalyst or surfactant. For the purpose of comparison, it was also prepared using the conventional combustion method (CCM). The as-synthesized ZrO 2 was characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. The results indicated that the ZrO 2 nanocrystals obtained by MCM show high crystallinity and uniform size distribution than the ones prepared by CCM. Hence, the influence of the preparation methods on the structure, morphology and optical activity of ZrO 2 was investigated systematically. Photocatalytic degradation (PCD) of 4-Chlorophenol (4-CP), a potent endocrine disrupting chemical in aqueous medium was investigated by ZrO 2 nanocrystals obtained by MCM. The kinetics of PCD was found to follow pseudo first-order. Having established that ZrO 2 was photo catalytically active, the mixed oxide catalysts of ZrO 2-TiO 2 were also tested for the PCD of 4-CP. © 2012 Elsevier Inc.

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