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

The l-arginium adipate (LAA) single crystal, is an organic component material efficiently grown by a simple technique called slow evaporation solution technique at ambient temperature. The monoclinic crystal system with the space group of P21 is exhibited for LAA from the X-ray diffraction analysis. FTIR spectroscopy that designates different molecular vibrations existing in LAA crystal was studied. The absorbance spectrum from the UV profile proclaims very less cut-off wavelength down to 206 nm and its wide optical band gap is also calculated. The perfection of the crystal is shown from Urbach's energy determination. The extent of polarization phenomena was examined for selected temperatures at dissimilar frequencies from the dielectric studies. The double harmonic output and triple-order nonlinear response for LAA are inspected from Kurtz-Perry and Z-scan technique, respectively. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

World University root node

School of Advanced Sciences

Chennai Campus

Journal of Materials Science: Materials in Electronics

Linear and nonlinear optical investigation of l-arginium adipate single crystal for photonic applications

Novel cocrystals of 18-crown-6 (18C6) with 5-nitroisophthalic acid (5NIPA) have been prepared by reaction in a solution of CH3OH–H2O (2:3, v/v) and C2H5OH–H2O (2:3, v/v) systems. The cocrystals 18-crown-6.5-nitroisophthalic acid. CH3OH.2(H2O) (I) and 18-crown-6.5-nitroisophthalic acid.3(H2O) (II) have been characterized by X-ray diffraction and constructed supramolecular assembly is thoroughly investigated. CH3OH incorporation inducing centrosymmetric crystallization and acentric crystal packed supramolecular construction in presence of ethanol are the highlights of the study. Intermolecular interactions are quantified by Hirshfeld surface analysis. First-order molecular hyperpolarizability estimated by theoretical calculations indicate a significant microlevel nonlinearity in both cases and Z-scan studies suggest a promising third-order nonlinear optical behaviour. Supramolecular assembly afford multiple strong O–H ….O hydrogen bonds creating a facile atmosphere for optical nonlinearity and mainly these O ….O hydrogen bonds stabilize the structure. © 2019 Elsevier B.V.

Journal of Molecular Structure

Multiple strong hydrogen bonded supramolecular cocrystals of 18-crown-6 with 5-nitroisophthalic acid: Solvent effect and optical nonlinearities

An organic salt, bis (2-methylimidazolium-4-aminobenzoate) (MIAB) was synthesized and single crystals grown successfully by slow solvent evaporation solution growth technique using ethyl acetate as solvent at room temperature. Fourier transform infrared (FTIR) spectral analysis was carried out to detect the presence of functional groups in the MIAB salt crystal. 1H and 13C spectra were recorded to confirm the presence of various kinds of proton and carbon environments thereby establish the molecular structure of MIAB crystal. Single crystal X-ray diffraction analysis (SCXRD) reveal that the crystal belongs to monoclinic system centrosymmetric space group, P21/c. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) confirms that the MIAB crystal is thermally stable up to 250 °C. The mechanical properties of the grown crystal were determined by Vickers Microhardness test. Computational studies were performed using Gaussian 09 software by 6.31 g basis set level. The calculated first order hyperpolarizability (β) of MIAB from computational studies is 5.01 times that of Potassium dihydrogen phosphate (KDP). The laser damage threshold value of the MIAB is found to be 1.44 GW/cm2. Z-scan technique reveals the optical non-linearity of the crystal. © 2019 Elsevier B.V.

Synthesis, structural, thermal, mechanical, laser damage threshold and DFT investigations on bis (2-methylimidazolium-4-aminobenzoate) single crystal

Herein we report the tunable optical limiting property of a metal–organic cesium tetroxalate dihydrate (CTD) complex. Temperature and pH were optimized to be 40°C and 3.5 respectively to grow CTD single crystal using the solvent evaporation method. The compound formation was confirmed by its response to single crystal and powder x-ray diffraction analysis. Thermal, mechanical, dielectric, linear optical, photoconductivity and photoluminescence properties of title crystal are reported. Nonlinear coupling between delocalized π-electrons of metal–ligand interaction and the oscillating electric field of a laser beam enhanced the nonlinear optical parameters. The third order nonlinear refractive index (n2), absorption coefficient (β) and susceptibility (χ(3)) of CTD complex under continuous-wave laser excitation are found to be (3.26±0.033)×10−8 cm2W−1, (10.33±0.41)×10−4 cmW−1 and (8.98±0.35)×10−5 esu respectively. Variation in two-photon absorption (2PA) coefficient measured under nanosecond pulsed laser excitation of different intensities confirmed the presence of sequential 2PA in CTD complex. The optical limiting threshold was investigated under different intensities were found to vary from (1.09±0.05)×1012 Wm−2 to (2.49±0.05)×1012 Wm−2 showing the intensity tunable optical limiting property of CTD material. © 2020 Elsevier B.V.

Optical Materials

Physicochemical properties of cesium tetroxalate dihydrate single crystal: An efficient material for nonlinear optical applications

In this article, Ni0.5Zn0.5Fe2O4 nanoparticles (NPs) were synthesized by differing concentrations of fuel (lean, stoichiometric, and rich) via microwave-assisted combustion route. The effect of fuel content was used to explore their chemical, electrical, and nonlinear optical properties along with their antibacterial activity of the as-prepared Ni/Zn/ferrite NPs were studied. The XRD assures the cubic crystal structure of prepared NPs with no secondary phase. It is also clear that as lattice parameters increases, the mean crystallite size decreases as a change in fuel ratio. The optical energy bandgap values are estimated as 2.88, 3.28, and 3.0 eV, respectively. From the luminescence spectra, the Ni/Zn ferrite NPs exhibits strong green emission and weak violet emission color. The fuel ratio has a significant influence on the electronic polarizability properties of synthesized NPs. Closed and open aperture Z-scan technique reveals that the Ni/Zn ferrites NPs have self-defocusing nature, and reverse saturable absorption. The calculated values are NLA coefficients (10-5 cmW−1), NLR index (10−9 cm2W−1), and third-order NLO susceptibility χ(3) values of fuel lean (1.408 × 10−5 esu), stoichiometric (2.75 × 10−6 esu), and rich (2.634 × 10−5 esu). Several identified microorganisms such as gram + Ve (S. aureus, B. cereus), and gram -Ve (P. aeruginosa, V. cholerae, and E. coli) have been tested for antibacterial activity against Ni/Zn ferrite nanoparticles. The ZOI values are 27 (lean), 24 (stoichiometric), and 25 mm (rich) which suggest great antibacterial activity against Pseudomonas aeruginosa gram-negative bacterium. However, this study shows excellent feasibility of applying prepared ferrite nanoparticles for optoelectronic devices and pharmaceutical processing applications. © 2020 Elsevier B.V.

Journal of Photochemistry and Photobiology A: Chemistry

Investigations on structural, optical, dielectric, electronic polarizability, Z-scan and antibacterial properties of Ni/Zn/Fe2O4 nanoparticles fabricated by microwave-assisted combustion method

Monoclinic ZnWO4 nanostructures with various concentration of Er were prepared by hydrothermal approach. The synthesized nanostructures were characterized by UV–vis spectra, X-ray diffraction (XRD) technique, steady-state and time-resolved fluorescence lifetime measurements. XRD results confirmed that Er3+ ions were successfully incorporated into ZnWO4 lattice without any secondary phase formation. The incorporation and energy transfer of Er into ZnWO4 were revealed by emission spectra and lifetime decay curves. The nonlinear optical properties of the nanostructures were studied by continuous wave Z-scan technique at 532 nm using Nd: YAG laser. From the open aperture and closed aperture Z-scan traces, the extracted nonlinear absorption and refraction data are attributed to reverse saturable absorption and self-defocusing nature of the samples. The optical nonlinearity of the nanostructures was found to be increasing with increased Er3+ dopant concentration. The observed nonlinearity suggests that the synthesized nanostructures could be explored for its applications in advanced photonic devices. © 2019 Elsevier B.V.

Department of Thermal and Energy Engineering

School of Mechanical Engineering

Vellore Campus

Luminescence and nonlinear optical properties of Er3+- doped ZnWO4 nanostructures

Urea-adipic acid (UHA) co-crystal was synthesized and harvested at room temperature by the slow evaporation method. The single X-Ray diffraction of the crystal system and its lattice parameters of the UHA co-crystal were determined. The functional nature of the compound was analyzed using FT-IR and FT-Raman spectra. By the UV–Vis spectrum, the optical transmission property was estimated and the mechanical stability was found by Vickers microhardness experiment. Further, the thermal stability and melting point was studied by TG/DSC methods. In the range of frequencies 50 Hz -5 MHz at different temperatures 313 K, 333 K, 353 K, and 373 K the crystal dielectric behavior has been observed. Fluorescence study and lifetime-resolved decay computation were also performed. The SEM picture rendered the surface morphology of UHA crystal. The structural properties of the UHA crystal were computed utilizing the CAM-B3LYP method and 6–311++G(d,p) basis set and found agreeable with the experiment data (XRD). The linear polarizability (α) and hyperpolarizability (β) of first-order have also been determined. The HOMO and LUMO (bandgap) energies, molecular electrostatic potential and Non-linear optics (NLO) explain the chemical activity of the UHA confirming the advantage of the material. The UHA nonlinear optical characteristics of third-order have been analyzed by the Z-scan technique. © 2019 Elsevier B.V.

Co-crystals of urea and hexanedioic acid with third-order nonlinear properties: An experimental and theoretical enquiry

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.

Department of Bio-Medical Sciences

School of Bio Sciences and Technology

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

A novel semi-organic single-crystal exhibiting third order optical nonlinearity was grown by the method of slow evaporation. Single crystal X-ray diffraction technique (XRD) was employed to confirm the crystal structure and powder XRD was used to determine the cell parameters. The sample was characterized using FT-IR, FT-Raman and UV–visible absorption and analysed with density functional theory (DFT) calculations. The detailed interpretation of the vibrational spectra has been carried out using normal coordinate analysis (NCA) through the scaled quantum mechanical force field methodology. The red shifting of NH stretching wavenumbers, both the observed and calculated, affirm that N–H……O type bonds are present in GuLG. The Natural Bond Orbital (NBO) analysis also points to a strong intermolecular N–H….O hydrogen bond. Thermal stability of the crystal was studied making use of the TG/DTA technique. The third-order nonlinearity studies, along with the optical limiting behaviour were investigated by Z-scan technique using diode-pumped Nd: YAG laser with 50 mW power at 532 nm.H © 2020 Elsevier B.V.

Growth, Z-scan and density functional theoretical study for investigating the nonlinear optical properties of guanidinium L-glutamate for optical limiting applications

The nanoparticles of pure and Co doped CeO2 were synthesized by means of auto ignition combustion process. Phase purity and structure of the synthesized nanostructures were examined by X-ray diffraction analysis. Crystal structure and cell parameters were refined by Rietveld analysis. The modifications in the position of Raman peaks, intensityand linewidth of F2g mode can be associated with factors such as confinement of phonons, defects and non-homogeneous distribution of particle sizes which in turn results in fluctuations in phonon relaxation. The Z-scan technique in the open and closed aperture modes reveals the self-defocusing nature and third order nonlinearity of the samples as arising due to reverse saturable absorption. Z-scan studies brought to light that the NLO properties of the Co doped CeO2 nanoparticles were significantly magnified when compared to pure CeO2, the doping of Co increased the time of electron transfer and photon transition, suppressed the electron hole recombination, and prolonged the working time of the free carrier, finally magnifying the nonlinear optical properties of the nanoparticles. Photocatalytic activity study of methylene blue and eosin yellow dye on Co doped CeO2 NPs were carried out using solar irradiation. Percentage of dye degradation and the rate at which degradation occur were calculated. High percentage of degradation shown by Co doped CeO2 NPs on EY dye. Mechanism of degradation of MB and EY dyes under solar irradiation had studied. The mechanism reveals that transition metal doping improve the trapping of e--h+ recombination during solar irradiation. © 2020 Elsevier Ltd and Techna Group S.r.l.