Showing papers by "G. Vinitha published in 2021"

Thulium-doped barium tellurite glasses: structural, thermal, linear, and non-linear optical investigations

Abstract: A systematic study of structural, thermal, linear, and non-linear optical properties on 60TeO2–20ZnO–(16 − x)BaCO3–4BaF2–xTm2O3 (x = 0.25 to 2 mol%) glasses synthesized by melt-quenching technique is reported. Thermal stability of the samples was found to be around 100 °C, while their energy bandgap values varied between 3.08 and 3.57 eV. Measured properties showed a dominant effect of thulium ions in modifying the properties of the glassy matrix. Structural studies using Raman spectroscopy showed the presence of non-bridging oxygen (NBO) dominated by the matrix effect and also aided by the rare earth dopants, while the presence of hydroxyl impurities was elucidated from infrared spectroscopy. Optical absorption spectra showed characteristic thulium bands and the increment in spectroscopic quality factor calculated from measured absorption data indicating the lasing capability of the material. Luminescence spectra yielded two strong 3H4 → 3F4 and 3F4 → 3H6 emission transitions in the infrared region around 1460 nm and 1863 nm for all the samples, intensities of which were affected by increasing rare earth concentrations. Open aperture Z-Scan measurements indicated a reverse saturable absorption behavior for all the samples owing to two-photon absorption. Formation of more NBO led to the reduction of optical limiting threshold values from 3.91 × 1012 to 2.38 × 1012 W/m2 with thulium doping which indicated that this glass can be tuned to act as mid-infrared source as well as excellent optical limiter.

Structural, thermal, dielectric, nonlinear optical properties and DFT investigations of a novel material 2-(6-chloropyridin-3-yl)-N'-(2,3-dihydro-1,4-benzodioxin-6-ylmethylidene)acetohydrazide for optoelectronic applications

Abstract: A new organic nonlinear optical (NLO) material 2-(6-chloropyridin-3-yl)-N'-(2,3-dihydro-1,4-benzodioxin-6-ylmethylidene)acetohydrazide (CDA) has been synthesized by reflux method. Single crystals were grown by slow evaporation technique and the crystal structure was elucidated by single crystal X-ray diffraction method. Density functional theory (DFT) calculations at B3LYP/6–31+ + G(d, p) basis set was used to predict the molecular geometry and were carried out further to comprehend the electronic structure, vibrational spectra, natural bonding orbitals (NBO), frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP). An optical transparency at the cut-off wavelength of 355 nm was determined by UV–Vis–NIR spectroscopy. Thermal behavior of CDA was studied by TGA/DTA analysis. The dielectric constant (e), dielectric loss (tan δ) and AC conductivity as a function of frequency and temperature was studied. Second Harmonic Generation (SHG) efficiency of the CDA was determined using Kurtz and Perry powder technique and was 0.5 times greater than that of the KDP crystal. The third-order nonlinear optical properties were investigated in solution by Z-scan technique using a continuous wave (CW) DPSS laser at the wavelength of 532 nm. The title compound exhibited significant two-photon absorption (β = 2.228 × 10–4 cm W−1), nonlinear refraction (n2 = 1.095 × 10–8 cm2 W−1) and optical limiting (OL threshold = 2.511 × 103 W cm−2) under the CW regime. The nonlinear optical parameters were calculated using time-dependent Hartree–Fock (TDHF) method. The overall obtained results suggested that the studied CDA molecule could be a potential NLO material for frequency generator, optical limiters and optical switching applications.

Growth and characterization of organic material 3,4-dimethoxybenzaldehyde-2,4-dinitroaniline single crystal

Abstract: The organic material 3,4-dimethoxybenzaldehyde-2,4-dinitroaniline was synthesised and the single crystal has been grown by slow evaporation technique. Single-crystal X-ray diffraction studies show that the grown 3,4-dimethoxybenzaldehyde-2,4-dinitroaniline single crystal belongs to the monoclinic system with the centrosymmetric space group P21/n. The FTIR and FT-Raman spectra were recorded to identify the functional groups present in the grown crystal. The optical property of the grown crystal was analyzed by UV–Vis–NIR studies and determines the optical band gap, the refractive index, the optical conductivity and the Urbach energy. The photoluminescence (PL) studies show that the grown crystal has green colour emission. The thermal property of the grown crystal was analysed by thermogravimetric (TG) and differential thermal analyses (DTA). The kinetic parameters such as the activation energy, frequency factor, entropy, enthalpy and Gibbs-free energy are computed from TGA data using Coats–Redfern method. The dielectric studies were analyzed by using the parallel plate capacitor method. The activation energy is calculated from Arrhenius plot. The electronic properties such as the plasma energy, the Penn gap, the Fermi energy and the electronic polarizability are calculated. The third order nonlinear optical properties of 3,4-dimethoxybenzaldehyde-2,4-dinitroaniline was measured by the Z-scan technique using 532 nm diode pumped continuous wave (CW) Nd:YAG laser.

Growth and characterization of 2-aminopyridinium malonate single crystal for photonic device applications

Abstract: An organic conjugated chromophore 2-aminopyridinium malonate (2APM) single crystal was synthesized and grown-up by means of slow solvent evaporation method. The unit cell parameters were assessed from single-crystal X-ray diffraction analysis. The various characteristic fundamental vibration frequencies were identified by FTIR spectroscopic studies. Optical parameters like nature of transmittance, lower cut-off wavelength, and band gap (Eg) were found using UV–Vis–NIR spectrum. The mechanical property like microhardness of the 2APM sample was studied using a Vickers microhardness tester. The thermal stability nature of the grown crystal was determined using differential scanning calorimeter examination. The dielectric behavior of the 2APM crystal was studied at various frequencies and temperature. A Z-scan technique was used to investigate the third-order NLO response in 2APM.

Intensity tunable optical limiting behaviour of an organic material 2-aminopyridinium succinate succinic acid single crystal

Abstract: A mixed solution of 2-aminopyridine and succinic acid, with a 1:1 molar ratio, was kept at room temperature to develop a 2-aminopridinium succinate succinic acid (2APSS) crystal. The crystal structure was confirmed and cell parameter values were carried out using single-crystal XRD analysis. A FTIR spectrometer was used to identify the various functional groups in the 2APSS crystal. UV–Vis–NIR spectral analysis displayed optical parameters of the 2APSS crystal, namely lower cut-off wavelength, percentage of optical transmittance and band gap energy. The estimated values of lower cut-off wavelength and band gap energy are 354 nm and Eg = 5.77 eV, respectively. The dielectric behaviour of the 2APSS crystal was analysed. The thermal properties, namely thermal stability and melting point of the crystal (159 °C), were found by employing differential scanning calorimetry. The 2APSS crystal soft material category was confirmed by Vicker’s microhardness study. A photoluminescence study was implemented to find out the emission spectrum of 2APSS. To demonstrate the third-order susceptibility of the produced crystal, Z-scan technique were used. It is important that the title material has a variety of excellent physicochemical and nonlinear optical characteristics, which assist it in gaining recognition as a prospective candidate for nonlinear optical device applications.

Third-order nonlinear optical characteristics of Er3+-doped BaMoO4 nanostructures

Abstract: We report the third order nonlinear optical properties of Er3+-doped BaMoO4 nanostructures, and its dependence on Er-dopant concentration. BaMoO4 nanostructures with different concentration of Er were synthesized by chemical precipitation method and were characterized by UV–Vis absorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and fluorescence measurements. The incorporation of Er ions shifted the absorption band of BaMoO4 towards higher wavelength and enhanced the light absorption in the visible region. XRD patterns showed that the powders crystallize in scheelite-type tetragonal structure. The nonlinear optical behavior of the nanostructures was investigated by a Z-scan technique at 532 nm using continuous wave Nd:YAG laser. Experimental results suggested that the addition of Er can considerably enhance the nonlinear absorption coefficient and refractive index of BaMoO4 which could be used as a potential for nonlinear optical device applications.

Crystal structure and physicochemical properties of a new optofunctional metal-organic cocrystal delivering intermolecular charge-transfer-enhanced nonlinear optical and optical limiting properties

Abstract: Crystal structure, physicochemical and intermolecular charge-transfer-enhanced third order nonlinear optical properties of a new metal-organic cocrystal $$\{[\hbox {NiCl}_2(\hbox {C}_4\hbox {H}_{11}\hbox {N}_2)_2(\hbox {OH}_2)_2](\hbox {Cl})_2 (\hbox {OH}_2)_2\hbox {n}\}$$ (PNi) is reported. An intermediate piperazinium chloride created during the pH optimization reacts with the metal centre (Ni), forming mono-substituted piperazine metal-organic cocrystal. The PNi adopts octahedral coordination geometry with triclinic ( $$P\overline{1}$$ ) crystal system at its single crystalline phase. The crystal packing stabilization via $$\hbox {O}-\hbox {H}\cdots \hbox {Cl}$$ , $$\hbox {C}-\hbox {H}\cdots \hbox {Cl}$$ and $$\hbox {O}-\hbox {H}\cdots \hbox {O}$$ noncovalent charge-transfer interactions is observed from single-crystal X-ray diffraction analysis. The PNi single crystal is thermally stable up to 87 $$^\circ$$ C. The $$\hbox {H}_2\hbox {O}$$ molecules tend to evaporate at lower temperatures bringing moderate, rather sufficient thermal stability for using the title material in lasing applications. Vickers microhardness study revealed that the title crystal belongs to the soft material category. Investigation on dielectric properties showed polar dielectric nature of the material with consistent electronic polarizability ( $$\alpha =1.11\times 10^{22}\ \hbox {cm}^3$$ ). The optical bandgap of 5.17 eV from UV-DRS spectroscopic analysis shows PNi belongs to the wide bandgap material category. The third order nonlinear optical absorption ( $$\beta$$ ), nonlinear refractive index ( $$n_2$$ ) and third order nonlinear optical susceptibility ( $$\chi ^{(3)}$$ ) of PNi cocrystal using 532 nm CW DPSS laser are measured to be $$(0.067\pm 0.001)\times 10^{-4}\ \hbox {cmW}^{-1}$$ , $$(0.211\pm 0.0057)\times 10^{-8}\ \hbox {cm}^2\hbox {W}^{-1}$$ and $$(0.511\pm 0.09)\times 10^{-6}$$ esu, respectively. Intermolecular charge-transfer interactions and electronic polarizability well influence nonlinear optical properties and are proved possible by calculating the intermolecular charge-transfer interactions at the B3LYP/6-31G(d,p) level of calculations. Further, the nonlinear absorption coefficient ( $$\beta$$ ) was found to vary with the laser intensities, explicitly indicating the presence of excited state absorption assisted sequential 2PA in PNi cocrystal. Low onset limiting threshold for nanosecond pulsed and continuous-wave laser irradiance ( $$(1.66\pm 0.02)\times 10^{12}\ \hbox {Wm}^{-2}$$ and $$(0.804\pm 0.02)\times 10^{03}$$ $$\hbox {Wcm}^{-2}$$ , respectively) promotes the title material as an efficient candidate for optical limiting application.

Structural, theoretical and third order nonlinear optical properties of (E)-N’-(4-chlorobenzylidene)-4-fluorobenzohydrazide monohydrate

Abstract: The title compound (E)-N’-(4-chlorobenzylidene)-4-fluorobenzohydrazide monohydrate (CBFBH) is a novel hydrazone Schiff base compound, synthesized and characterized by FTIR, 1H and 13C NMR, UV-Vis a...

Effect of Zn2+ ions on third order nonlinear optical behavior and power limiting properties of manganese ferrite nanoparticles

Abstract: Zinc-doped manganese ferrites synthesized by chemical co-precipitation technique showed significant linear and nonlinear optical properties and have been utilized to realize optoelectronic device applications. Mn1−xZnxFe2O4 (0 ≤ x ≤ 0.25) nanoparticles were characterized by various spectroscopic and microscopic techniques along with Z-scan studies. The formation of a single phase cubic spinel structure is confirmed from XRD analysis, whereas the FTIR spectra indicated corresponding bond formations between the ions. The micrographs of doped and undoped samples show a clear difference in morphology. The absence of additional/impure peaks in EDX spectra confirms phase purity. The optical band gap decreases with increasing Zn2+ ion concentration, which indicates the blue shift. In PL spectra, the peak at 386 nm is attributed to the defects which are originated because of oxygen vacancies. Calculated nonlinear parameters such as nonlinear absorption coefficient (β), nonlinear refractive index (n2), real and imaginary parts of third order nonlinear susceptibility (χ3) of doped systems are found to be enhanced compared with pure ferrite. Limiting threshold values indicate that the Zn2+ doped manganese spinel ferrites are one of the efficient materials for broadband optical limiting applications.

Investigations on Structural, Mechanical, Optical, Electrical, Third-Order Nonlinear Optical and Antibacterial Activity of 4-Aminopyridine Monophthalate Single Crystal

Abstract: An organic 4-aminopyridine monophthalate (PA4AP) single crystal grown by solvent evaporation at room temperature was studied for third-order nonlinear optical and antibacterial applications. The title material was found to crystallize in a non-centrosymmetric orthorhombic system with space group P212121, and the crystallographic information was acquired by its response to X-ray diffraction analysis. The functional groups and their different modes of vibration were studied by FTIR spectroscopy to identify the various chemical bonds present in PA4AP. Optical absorption study revealed less absorption in the visible region with an absorption cut-off wavelength at 315 nm, below which the material shows complete absorption. The title crystal was characterized for luminescence and based on this the inter-band structures were analysed for crystal defects. Mechanical and dielectric properties with an emphasis on solid-state parameters were investigated to understand the crystal stability for device applications. Kurtz–Perry powder analysis revealed that the PA4AP crystal has comparable second harmonic generation efficiency with the well-known KDP crystal. The third-order nonlinear optical susceptibility (χ(3)), nonlinear absorption coefficient (β) and nonlinear refractive index (n2) of title material were found to be 1.06 × 10−6 (esu), 6.51 × 10−5 (cm W−1) and 2.33 × 10−8 (cm2 W−1), respectively. The reverse saturable absorption observed in open aperture Z-scan indicates the suitability of PA4AP for optical limiting application. The antibacterial activity was investigated against few foodborne pathogens which show the antibacterial stability of PA4AP against Shigella flexneri and Vibrio cholerae bacteria.

Structural, spectral, experimental, and theoretical investigations of (E)-4-fluoro-N′-(pyridin-2-ylmethylene)benzohydrazide monohydrate

Abstract: The structural and nonlinear optical properties of the Schiff base material, (E)-4-fluoro-N′-(pyridin-2-ylmethylene)benzohydrazide monohydrate (FPMBH) were studied. The experimental investigations were performed using Fourier transform infrared (FTIR), ultraviolet (UV) and nuclear magnetic resonance (NMR) spectral techniques. The computational analyses were made by DFT method. A comparison between experimental and theoretical predictions was made and interpreted. The maximum absorption wavelength was found by both experimental and theoretical analyses. The Hirshfeld surface analysis was performed to understand the various molecular interactions. Highest occupied and lowest unoccupied molecular orbitals (HOMO–LUMO) analysis was performed for the title molecule to know about the possible charge transfer taking place within the molecule. Reactivity features were also determined by molecular electrostatic potential (MEP) analysis. The third-order nonlinear optical studies were done by z-scan experiment, and the results were discussed.