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Surekha R.,Prathyusha Institute of Technology and Management | Sagayaraj P.,Loyola College | Ambujam K.,Queen Marys College
CrystEngComm | Year: 2014

l-Phenylalanine l-phenylalaninium bromide (LPLPB), an amino acid non-centrosymmetric crystal having a large second harmonic generation (SHG) efficiency, being 4.5 times that of KH2PO4 (KDP), has been successfully grown using a slow evaporation method employing a temperature gradient technique. The structure of the grown crystal was solved and refined by single-crystal X-ray diffraction, and this demonstrates that it belongs to a monoclinic system with the space group P21. The confirmation of its functional groups was recorded using Fourier transform infrared spectroscopy. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to study its thermal properties. The optical behaviour was examined and its optical constants were determined by UV-vis analysis. Dielectric spectroscopy reveals the dielectric nature of the grown crystal. The mechanical strength of the grown LPLPB was estimated by microhardness studies, and the Young's modulus of the grown LPLPB was calculated to be 3.310 × 10 10 N m-2. This journal is © the Partner Organisations 2014.


Sudhakar T.,Sathyabama University | Karpagam S.,Queen Marys College
International Journal of ChemTech Research | Year: 2013

The characterization of a Pseudomonas aeruginosa is the production of soluble pigment pyocyanin which has the property of antagonism towards bacteria and fungi. This strain was isolated from the clinical sample and the pigment was optimized by using various solid and liquid media. The pigment was extracted using chloroform resulting in a bluish colored compound and upon addition of 0.2 N HCl giving red color. Further, the pigment was partially purified using chromatographic technique and the maximum absorbance peak at 278 nm, characteristic of pyocyanin. The molecular weight of the compound was analyzed using Gas Chromatography - Mass Spectrometer (GC-MS) and found to be 210.23 kDa with an Rf value 11.94. The pigment was subjected to antagonistic activity against commonly encountered phytopathogens and its inhibitory concentration was observed at 64 μg/ml. The growth suppression phenomenon of this pigment isolated from the strain against fungi. This study reveals that the strain can be economically used as biocontrol agent against common phytopathogenic fungi.


Gnanasekaran L.,Queen Marys College | Hemamalini R.,Queen Marys College | Ravichandran K.,University of Madras
Journal of Saudi Chemical Society | Year: 2015

In the present study, TiO2 quantum dots (QDs) were effectively synthesized by the sol-gel method and it was characterized by several techniques. The structure of the TiO2 QDs, before and after calcination, was analyzed by the powder X-ray diffraction technique. The XRD results indicate that after calcination, TiO2 QDs have pure anatase phase with tetragonal structure without any other phases and impurities. The morphology and size of the TiO2 QDs were determined from FE-SEM and TEM analysis. The optical band gap of TiO2 QDs was estimated using Kubelka-Munk function from diffuse reflectance spectroscopy. The photocatalytic activity and recycling ability of the TiO2 QDs have been investigated. The TiO2 QDs were used to degrade the model dyes such as methyl orange and methylene blue under UV light irradiation and their results have been discussed. A mechanism is proposed and discussed accordingly in detail. © 2015 The Authors.


John R.,University of Madras | Rajakumari R.,Queen Marys College
Nano-Micro Letters | Year: 2012

Zinc oxide (ZnO) doped with erbium at different concentrations was synthesized by solid-state reaction method and characterized by X-ray diffraction (XRD), scanning electron microscopic (SEM), UV- absorption spectroscopy, photoluminescence (PL) study and vibrating sample magnetometer. The XRD studies exhibit the presence of wurtzite crystal structure similar to the parent compound ZnO in 1% Er 3+ doped ZnO, suggesting that doped 3+ ions sit at the regular Zn 2+ sites. However, same studies spread over the samples with 3+ content>1% reveals the occurrence of secondary phase. SEM images of 1% 3+ doped ZnO show the polycrystalline nature of the synthesized sample. UV-visible absorption spectrum of 3+ doped ZnO nanocrystals shows a strong absorption peak at 388 nm due to ZnO band to band transition. The PL study exhibits emission in the visible region, due to excitonic as well as defect related transitions. The magnetization- field curve of 3+ doped ZnO nanocrystals showed ferromagnetic property at room-temperature.


Rahulan K.M.,SRM University | Balamurugan S.,Universiti Sains Malaysia | Meena K.S.,Queen Marys College | Yeap G.-Y.,Universiti Sains Malaysia | Kanakam C.C.,SRM University
Optics and Laser Technology | Year: 2014

3-(4-(dimethylamino)phenyl)-1-(4-(4-(hydroxymethyl)-1H-1,2,3-triazol-1-yl) phenyl)prop-2-en-1-one was synthesized and its third order nonlinear optical properties have been investigated using a z-scan technique with nanosecond laser pulses at 532 nm. The nonlinear absorption behavior of the compound in chloroform presents a distinct difference at different laser intensity. Interestingly, the compound showed a switchover from saturable absorption (SA) to reverse saturable absorption (RSA) with the increase of excitation intensity. Our studies suggest that compound could be used as a potential candidate for optical device applications such as optical limiters. © 2013 Elsevier Ltd.


Surekha R.,Prathyusha Institute of Technology and Management | Sagayaraj P.,Loyola College | Ambujam K.,Queen Marys College
Optical Materials | Year: 2014

Optical quality bis glycine hydrobromide (BGHB) single crystal was grown by slow evaporation technique. The third order nonlinear refractive index and nonlinear absorption coefficient of the grown crystal were measured by Z-scan studies. The third order nonlinear susceptibility was found to be 9.612 × 10-4 esu which is fairly higher than the other glycine compounds. The Photoluminescence spectra reveal the emission bands for BGHB crystals. The band gap energy was calculated to be 3.1 eV. The Photoconductivity studies were employed to determine the dependence of photocurrent on the applied electric field. Negative photoconductivity was exhibited by the sample. The d.c. conductivity of the grown crystal was measured by the complex impedance analysis wherein the obtained plot in the form of semicircle finds application in Debye relaxation for materials having large dc conductivity. © 2014 Elsevier B.V. All rights reserved.


Thilagavathy S.R.,Hindustan University | Ambujam K.,Queen Marys College
Transactions of the Indian Institute of Metals | Year: 2011

Single crystals of an organic nonlinear optical (NLO) material, glycine picrate (DGP) has been grown from mixed solution by using the novel uniaxial crystal growth method of Sankaranarayanan and Ramasamy (SR) and conventional method. The novel method allows the crystal to grow in one specified axis with well developed faces. The grown crystals have been subjected to crystal structure studies and characterized by single crystal X-ray diffraction, Powder X-ray diffraction (PXRD), UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), Thermogravimetric/differential thermal analysis (TG/DTA), Vickers microhardness, dielectric measurements, etching and High-resolution x-ray diffraction (HRXRD). The NLO efficiency of the crystal has been confirmed by using the Kurtz powder technique. The present study indicates that the SR method is superior to conventional method for the growth of DGP single crystals. © 2011 Indian Institute of Metals.


Kalaiselvi D.,Queen Marys College | Jayavel R.,Anna University
Applied Physics A: Materials Science and Processing | Year: 2012

A semi-organic nonlinear optical L-proline dimercuricchloride (LPDMC) material has been synthesized. LPDMC single crystals were grown from aqueous solution by a slow cooling method. Good quality single crystals of size 19×6×3 mm 3 have been grown over a period of 3 weeks. The grown crystals have been subjected to single crystal X-ray diffraction analysis to determine the cell parameters. The title compound crystallizes in the triclinic system with a noncentrosymmetric space group P1 and with unit-cell parameters a=7.2742(4) Å, b=9.4472(5) Å, c=10.4767(6) Å, α=108.621(3)°, β=107.260(2)°, γ=97.353(2)° and volume=631.51(6) Å 3. Optical and dielectric properties of the crystals have been studied. The thermal stability of the crystals was determined by thermogravimetric analysis/differential thermal analysis. The second harmonic generation efficiency of the crystals was obtained by the classical powder technique using a Nd:YAG laser and it is found to be 2.5 times that of potassium dihydrogen phosphate. © 2012 Springer-Verlag.


Dhanalekshmi K.I.,Queen Marys College | Meena K.S.,Queen Marys College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

Core-shell type Ag@TiO2 nanoparticles were prepared by one pot simultaneous reduction of AgNO3 and hydrolysis of Ti (IV) isopropoxide and Ag@SiO2 core-shell nanoparticles were prepared by Stober's method. They were characterized by absorption, XRD, and HR-TEM techniques. XRD patterns show the presence of anatase form of TiO2 and amorphous form of SiO2 and the noble metal (Ag). High resolution transmission electron microscopy measurements revealed that their size is below 50 nm. The antibacterial properties of Ag@TiO2 and Ag@SiO2 core-shell nanoparticles against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were examined by the agar diffusion method. As a result E. coli and S. aureus were shown to be substantially inhibited by Ag@TiO 2 and Ag@SiO2 core-shell nanoparticles. These results demonstrated that TiO2 and SiO2 supported on the surface of Ag NPs without aggregation was proved to have enhanced antibacterial activity. © 2014 Elsevier B.V. All rights reserved.


Dhanalekshmi K.I.,Queen Marys College | Meena K.S.,Queen Marys College
Materials Science and Engineering C | Year: 2016

Ag@ZrO2 core-shell nanoparticles were prepared by one pot simultaneous reduction of AgNO3 and hydrolysis of zirconium (IV) isopropoxide. The formation of core-shell nanoparticles was confirmed by absorption, XRD, and HR-TEM techniques. The antibacterial activity of Ag@ZrO2 core-shell nanoparticles against Escherichia coli and Staphylococcus aureus and the antifungal properties against Candida albicans, Candida glabrata, Aspergillus Niger and Aspergillus flavus were examined by the agar diffusion method. DNA intercalation studies were carried out in CT-DNA. As a result ZrO2 supported on the surface of AgNPs not only prevented aggregation, but also proved to have enhanced antimicrobial activity and DNA intercalation than the Ag nanoparticles. © 2015 Elsevier B.V. All rights reserved.

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