Department of Physics

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Physics

Synthesis of hydrazine hydrate assisted manganese doped zinc selenides by hydrothermal technique led to the formation of good quality nanospheres which are controlled by Ostwald ripening process. Structural studies using XRD showed the incorporation of manganese in zinc selenide matrix with their crystallite sizes ranging between 10 and 15 nm, which corroborate with the TEM measurements. Dominant emission (517 nm) corresponds to the near band edge emission as observed from photoluminescence spectra. Presence of impurities and defects were identified from various other emissions as well as from the bandgap variation obtained from reflectance spectra. The third order nonlinearity of manganese doped zinc selenide nanoparticles were calculated by the standard Z-scan technique using 532 nm CW DPSS and nanopulsed Nd:YAG laser. Mn doped ZnSe nanoparticles which exhibits near resonant excited state absorption were found to be an ideal candidate to be exploited as optical limiters in protecting optical components from high intense laser pulses. Further, lower onset optical limiting threshold under pulsed laser excitation of manganese doped zinc selenides (2.92 × 1012 Wm−2) compared to pure zinc selenide (4.98 × 1012 Wm−2) confirms that doping of Mn in ZnSe can yield efficient energy absorbing optical limiters. © 2020 Elsevier B.V.

VIT School for Agricultural Innovations and Advanced Learning

Vellore Campus

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School of Advanced Sciences

Chennai Campus

Optical Materials

Investigations on the structural, morphological, linear and third order nonlinear optical properties of manganese doped zinc selenide nanoparticles for optical limiting application

4-methyl N-(4-chlorobenzylidene)aniline (4CBT) single crystal with dimension of 10 × 7 × 2 mm3 has been grown by the slow evaporation solution growth method. 4CBT crystal belonging to the monoclinic crystal system with space group of P21/c was studied by single-crystal X-ray diffraction. Fourier transform infrared analysis shows the existence of functional groups in 4CBT crystal. The existence of different protons position is confirmed using 1HNMR analysis. The optical nature of 4CBT is illustrated with help of cut-off wavelength and the transparency of the titled compound. The thermal stability of the grown crystal was analysed by thermogravimetric technique. Dielectric studies were also studied with respect to temperature and frequency. The energy values of highest occupied molecular orbital and lowest unoccupied molecular orbital have been measured by frontier molecular analysis. Third-order nonlinear optical properties of 4-methyl N-(4-chlorobenzylidene) aniline crystal were measured by Z-scan technique and the measured values of the nonlinear index of refraction and absorption coefficient shows the suitability of grown crystal for photonic applications. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

Journal of Materials Science: Materials in Electronics

Studies on growth, optical, dielectric, and third-order nonlinearity of 4-methyl N-(4-chlorobenzylidene)aniline (4CBT) crystal

Organic non-linear optical Benzimidazolium salicylate (BISA) single crystals have been harvested from methanol solution by slow evaporation method. The grown crystals belong to the monoclinic crystal system with space group P21/c. Good crystalline nature of grown BISA crystal was confirmed by PXRD. The FTIR spectrum analysis affirms the presence of functional groups in BISA crystal. From the UV‒Vis-Absorption spectrum, the lower cut-off wavelength (356 nm) and its energy band gap and linear refractive index were calculated. Luminescence spectrum was recorded to explore the emission peak at 426 nm. The mechanical strength of BISA crystal was determined by Vickers microhardness tester and mechanical parameters like Elastic stiffness constant (C11), Knoop hardness (Hk), Fracture toughness (Kc), and Brittleness index (Bi) were calculated for the first time. Dielectric properties of grown crystals were systematically investigated for different temperatures. Further, electronic polarizability (α) were calculated using Penn analysis and Clausius‒Mossotti equation. Z‒scan measurement was taken to explore the third-order NLO properties of BISA crystal and calculated values was found to be β (3.856×10‒5 cm/W), n2 (1.7882×10‒9 cm2/W), and χ(3) (6.3088×10‒7 esu). For the first attempt, the BISA crystals were tested against five human pathogenic bacterial, i.e. Bacillus cereus, Staphylococcus aureus, Shigella flexneri, Vibrio cholerae, and Klebsiella pneumoniae. Existing results established that Benzimidazolium salicylate crystals might find useful applications in nonlinear optics and antimicrobial field. © 2020 Precarpathian National University. All rights reserved.

Fulltext

Physics and Chemistry of Solid State

Crystal growth and characterization of benzimidazolium salicylate single crystal for nonlinear optical studies and antibacterial activity [Вирощування та характеристика монокристалів саліцилату бензимідазолію для нелінійних оптичних досліджень та антибактеріальної дії]

An impressive, nonlinear optically active single crystal, acid potassium hydrogen fumarate (2KC4H3O4.C4H4O4)(APHF)was grown by slow evaporation technique. Single crystal X-ray diffraction analysis confirms packing array and attribute of molecular geometry. FTIR and FT Raman studies aid to identify basic functional groups present in the crystal. UV–Vis spectral analysis predicts cut off wavelength as 295 nm. The Photo luminescence spectra shows an emission around 453 nm and its lifetime was also detected. Low dielectric constant of APHF can be utilized for microelectronics device fabrications. Vicker's microhardness test reveals the greater mechanical strength of APHF. TG and DSC studies shows thermal stability up to 253 °C.The total charge spread is described by Molecular electrostatic potential. Low HOMO-LUMO energy gap affirms the chemical softness of the material. The negative third order nonlinear parameters like refractive index (n2), absorption coefficient (β) and susceptibility (χ3) were estimated by Z-scan studies. © 2020 Elsevier B.V.

Journal of Molecular Structure

Growth, spectroscopic, HOMO-LUMO energies, MEP, hardness and TG/DTA studies of acid potassium hydrogen fumarate as an efficient nonlinear optical material

Organic single crystals of 2-picolinictrichloroacetate (PTCA) have been successfully grown by slow evaporation technique. The structural and optical characterization of the PTCA is analysed experimentally by Fourier transform infrared and UV–visible spectroscopic technique and theoretical studies, by density functional theory method. The charge transfer interactions leading to nonlinear properties taking place in the molecule have been studied by highest energy occupied molecular orbital and lowest energy unoccupied molecular orbital analysis and natural bond orbital analysis. Open-aperture Z-scan results on evaluating the nonlinear optical properties experimentally, confirm these materials as good optical limiters. In addition, the PTCA exhibits a blue luminescence emission which shows that it is a potential material for OLED device applications. © 2020, Indian Academy of Sciences.

Bulletin of Materials Science

Spectroscopic and third-order nonlinear optical properties of organic single-crystal 2-picolinictrichloroacetate: an overview

To delineate the ammonia sensing mechanism by amperometric sensors a series of lanthanum gallate based electrolytes having nominal compositions of La0.8Sr0.2Ga0.8Mg0.2-xNixO3 (0 ≤ x ≤ 0.2) and La0.8Sr0.2Ga1-yFeyO3 (0.01 ≤ y ≤ 0.1) were prepared by solution combustion technique. Phase purity of electrolyte pellets was achieved by high temperature sintering process. Aforementioned electrolyte compositions were investigated for NH3 sensing performance in the temperature range of 300 °C-550 °C. Exposing the sensors alternately to the base gas (5% O2 + N2) and 3-40 ppm NH3 in base gas. Effect of oxygen pumping current on sensing mechanism was studied. The electrolytes with 10 mol% Ni and 5 mol% Fe doping showed the highest sensitivity of 35 and 43 μA decade-1 at 400 °C and 450 °C respectively. Conductivity measurements showed conductivity of 526 × 10-5 at 400 °C and 1080 × 10-5 S cm-1 at 450 °C for La0.8Sr0.2Ga0.8Mg0.1Ni0.1O3 and La0.8Sr0.2Ga0.95Fe0.05O3 respectively. A correlation between conductivity and gas sensing was established. Finally, a mechanism based on the hypothesis of defect cluster formation due to aliovalent doping that enhanced conductivity coupled with oxygen pumping current was proposed. © 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

Journal of the Electrochemical Society

Sensing Behaviour Investigation of Amperometric Electrochemical NH3Sensor: Optimization of Lanthanum Gallate Based Electrolyte Composition

Optical quality crystal piperazine calcium chloride (PCC) was synthesized and grown successfully by slow evaporation solution growth technique at room temperature. Well-defined Bragg’s peak in powder x-ray diffraction analysis confirms the crystalline nature of the grown sample PCC. Unit cell parameters values that were calculated using single crystal x-ray diffraction analysis confirms that the crystal belongs to the monoclinic crystal system. The wave number band assignments of the synthesized material are identified by using Fourier Transform Infrared spectroscopy. Linear optical study shows that the UV cut-off wavelength was found to be 260 nm and also the optical energy band gap was calculated using UV data. Maximum emission spectra of wavelength 441 nm and 477 nm are evident in the emission of blue laser from the Florescence (PL) spectra. The dielectric constant and dielectric loss of the grown PCC crystal were analyzed as a function of different frequencies for different temperatures. As grown PCC crystal was subjected to thermal analysis to find the weight-loss and decomposition point using TG–DTA curve. Work hardening coefficient of as grown PCC crystal was 2.36, which is evidence that the crystal belongs to soft category material and also the mechanical parameters are calculated. Third order nonlinear optical property was analyzed using Z-scan technique, which shows that the crystal PCC obeys the third harmonic generation properties to enhance the optical device applications. © 2019, The Minerals, Metals & Materials Society.

Journal of Electronic Materials

Third Order Nonlinear Optical Properties of Piperazine Calcium Chloride (PCC) Crystal to Enhance the Optical Device Applications

Newman Penrose (NP) formalism is a new approach to general relativity was presented. In various geometrical groups are estimate on a chosen null tetrad basis for tetrad formalism. This approach widely used in analytical and numerical studies of Einstein's equations. The reasonable utilization of explicit complex straight emulsions of Ricci rotation coefficients which present, in the product, the spinor relative association. And we construct a null tetrad for general case and special attension for Bertrand's space-time type-1 metric for special case k=0. © Published under licence by IOP Publishing Ltd.

Journal of Physics: Conference Series

A newman penrose approach to Bertrand spacetime in general relativity

The 2-amino-5-bromopyridinium trifluoroacetate (2A5BPTFA) crystal has been successfully grown by solvent slow evaporation technique. The grown crystal is found to non-centrosymmetric space group Pna21 with orthorhombic crystal system, which has been confirmed from single crystal X-ray diffraction analysis. The crystalline nature of the 2A5BPTFA is supported by powder X-ray diffraction technique. The molecular structure and different functional groups in 2A5BPTFA were confirmed by 1H, 13C NMR and FTIR spectral analyses. The intermolecular charge transfer that occurs in 2A5BPTFA molecule due to the presence of N–H⋯O and C–H⋯O hydrogen bondings have been studied by Hirshfeld surface analysis. From the UV–Vis absorption and photoluminescence spectra, the lower cutoff wavelength and emission peak are found to be 364 nm and 392 nm, respectively. In addition, the optical band gap of grown crystal has been calculated as 3.47 eV. Powder second harmonic generation efficiency of the crystal is observed to be 2.44 times greater than that of potassium dihydrogen phosphate. A positive photoconducting nature and low dielectric constant values have been obtained from photoconductivity and dielectric studies. From the Z-scan study reveals the self-defocusing nature of the grown crystal. Optical limiting study shows the optical limiting response of 2A5BPTFA crystal. In addition, the intermolecular charge transfer interactions and existence of N–H⋯O hydrogen bonding of the 2A5BPTFA have been confirmed by density functional theory methods and are discussed in detail. © 2019 Elsevier Ltd

Department of Multimedia

School of Design

Department of Biotechnology

School of Bio Sciences and Technology

Journal of Physics and Chemistry of Solids

Experimental and quantum chemical studies on SHG, Z-scan and optical limiting investigation of 2-amino-5-bromopyridinium trifluoroacetate single crystal for optoelectronic applications

A conventionally grown organic nonlinear optical crystal bisguanidinium isophthalate monohydrate was structurally investigated using single crystal X-ray diffraction study. The lattice constants, supramolecular arrangements and the hydrogen bond formation of the title compound confirm the formation of novel organic crystalline material. The various functional groups present in the crystalline material were resoluted by employing FT-IR spectral analysis. The wide-range optical transparency of the compound in the entire visible region ensures the optical quality with a lower cut-off wavelength at 298 nm was analysed experimentally using UV–vis–NIR spectrometer. The support of DFT was scrutinized to report the optimized structure, electronic state properties, hyper-conjugative interactions and frontier molecular energy gap of the bisguanidinium isophthalate compound. The charge transfer mechanism of bisguanidinium isophthalate compound from isophthalic acid to guanidine compound was also interpreted using theoretical DFT. The computational evaluation of charge stabilities as a result of charge delocalization was construed with the ratification of natural bonding orbital (NBO). The assessed thermal stability of bisguanidinium isophthalate crystal is 120 °C which was analysed by thermogravimetric and differential thermal analyses. To determine the third-order nonlinear optical property with quantitative results of nonlinear refractive index, nonlinear absorption coefficient and optical susceptibility was ascertained using Z-scan technique. © 2019 Elsevier B.V.