Showing papers by "G. Vinitha published in 2018"

Growth, spectral, optical, laser damage threshold and DFT investigations on 2-amino 4-methyl pyridinium 4-methoxy benzoate (2A4MP4MB): A potential organic third order nonlinear optical material for optoelectronic applications

Abstract: In present investigation, single crystals of organic charge transfer complex, 2-amino-4-methyl pyridinium-4-methoxy benzoate (2A4MP4MB) was grown by controlled slow evaporation solution growth technique using methanol as a solvent at room temperature. Single crystal XRD analysis confirmed the crystal system and lattice parameters of 2A4MP4MB. The crystalline nature, presence of various vibrational modes and other chemical bonds in the compound have been recognized and confirmed by powder X-ray diffraction, FT-IR and FT-Raman spectroscopic techniques respectively. The presence of various proton and carbon positions in title compound was confirmed using 1H NMR and 13C NMR spectral studies. The wide optical operating window and cut-off wavelength were identified and band gap value of the title compound was calculated using UV-vis-NIR study. The specific heat capacity (cp) values of the title compound, 1.712 J g−1·K−1 at 300 K and 13.6 J g−1 K−1 at 433 K (melting point) were measured using Modulated Differential Scanning Calorimetric studies (MDSC). From Z-scan study, nonlinear refractive index (n2), nonlinear absorption (β) and third order nonlinear susceptibility (χ(3)) values were determined. The self-defocusing effect and saturable absorption behavior of the material were utilized to exhibit the optical limiting action at λ = 532 nm by employing the same continuous wave (cw) Nd: YAG laser source. The laser damage threshold (LDT) study of title compound was carried out using Nd: YAG laser of 532 nm wavelength. The Vickers’ micro hardness test was carried out at room temperature and obtained results were investigated using classical Meyer’s law. In addition, DFT calculations were carried out for the first time for this compound. These characterization studies performed on the title compound planned to probe the valuable and safe region of optical, thermal and mechanical properties to improve efficacy of 2A4MP4MB single crystals in optoelectronic device applications.

Crystal structure, molecular packing, FMO, NBO, nonlinear optical and optical limiting properties of an organic imidazolium diphenylacetate diphenylacetic acid single crystal

Abstract: An organic nonlinear optical (NLO) crystal, imidazolium diphenylacetate diphenylacetic acid (IDA), was synthesized and grown by the slow evaporation method. Formation of the new crystalline compound was confirmed by single crystal X-ray diffraction study. The title compound crystallizes in the triclinic crystal system with the space group P. UV-vis-NIR spectral study showed that the grown crystal is transparent in the entire visible region with a lower cut-off wavelength of 275 nm. Density functional theory (DFT) calculations were carried out to calculate the frontier molecular orbitals and natural bonding orbitals of the IDA compound. The frontier energy gaps calculated theoretically were useful to understand the charge transfer taking place in the molecule. The natural bonding orbital analysis provides a convenient basis for the investigation of the charge transfer or conjugative interactions in the molecular system. Vicker's microhardness study revealed that the title material belongs to the soft material category. The values of fracture toughness, brittleness index and yield strength have also been calculated for Palmqvist and median types of cracks. The title compound IDA is thermally stable up to 201 °C, as assessed by thermogravimetric and differential thermal (TG-DTA) analyses. The specific heat capacity of IDA is found to be 3.25 J kg−1 K−1 at 65 °C. The laser induced surface damage threshold of the grown crystal was measured to be 0.2645 GW cm−2 with 1064 nm Nd:YAG laser radiation. The nonlinear refractive index (n2), absorption coefficient (β) and third order nonlinear susceptibility (χ(3)) were determined using the Z-scan technique. An optical limiting study revealed that the transmitted output power increases linearly with the input power up to an irradiance of around 3.6 mW cm−2.

An experimental and computational approach to electronic and optical properties of Diglycine barium chloride monohydrate crystal: Applications to NLO and OLED

Abstract: Diglycine Barium Chloride Monohydrate have been synthesized and characterized by the 13C and 1H NMR spectroscopy and single crystal X-ray structural studies with a detailed analysis of Hirshfeld surface and fingerprint plots facilitating the interactions within the crystal structure. The Protonated N H⋯O and intermolecular interaction responsible for the NLO activity are studied using DFT studies as well as experimental spectroscopic techniques. The molecular geometry, first & second hyperpolarizability studies and harmonic vibrational wavenumbers were calculated using density functional theory with B3LYP/SDD methods. The detailed interpretation of the vibrational spectra (FTIR and Raman) was carried out with the Normal Coordinate Analysis (NCA) following the scaled quantum mechanical force field methodology. The inter and intra molecular interactions responsible for the stabilization of the molecule were revealed by the NBO and AIM analyses. Photoluminescence spectrum shows that the luminescence is at the blue region. The observed saturable absorption and self-defocusing effect lead to optical limiting action at 532 nm for a CW diode-pumped Nd: YAG laser (50 mW) beam. Optical nonlinearity studies (z-scan) give the nonlinear refractive index, nonlinear absorption coefficient, third order nonlinear susceptibility, second order hyperpolarizability and optical limiting. The obtained results indicate that the synthesised compound is a good candidate for optical limiting and OLED applications.

Synthesis, growth, structural modeling and physio-chemical properties of a charge transfer molecule: Guanidinium tosylate

Abstract: An organic nonlinear optical material, guanidinium tosylate was synthesized adopting slow evaporation method and the crystals were harvested from aqueous methanolic medium with dimensions 13 × 9 × 3 mm3. Constitution of crystalline material was confirmed by single crystal X-ray diffraction study. The title compound crystallizes in the monoclinic crystal system with space group P21/c. The UV–vis–NIR spectral study of the grown crystal exhibits high transparency of 80% in the entire visible region with lower cut-off wavelength at 282 nm. Optimized molecular geometry of the grown crystal was obtained using density functional theory (DFT) and the frontier energy gaps calculated from the DFT aids to understand the charge transfer taking place in the molecule. The dielectric properties were studied as a function of temperature and frequency to find the charge distribution within the crystal. The titular compound is thermally stable up to 230 °C assessed by thermogravimetric and differential thermal analysis. Anisotropy in the mechanical behavior was observed while measuring for individual planes. The laser induced surface damage threshold of the grown crystal was measured to be 0.344 GW/cm2 for 1064 nm Nd:YAG laser radiation. Z-scan technique confirms the third-order nonlinear optical property with the ascertained nonlinear refractive index (n2), nonlinear absorption coefficient (β) and third order nonlinear susceptibility (χ(3)). Optical limiting study divulges that the transmitted output power step-up linearly with the increase of the input power at lower power realms and saturates from the threshold 24.95 mW/cm2 and amplitude 0.23 mW/cm2.

Third order nonlinear optical properties of monoclinic and orthorhombic CuNb2O6 under CW laser illumination

Abstract: Third-order nonlinearity of monoclinic and orthorhombic phase of CuNb2O6 is studied in low power regime of 532 nm by Z-scan technique. In open aperture, monoclinic CuNb2O6 possess stronger saturable absorption due to the distorted structure arising from unequal arrangement of copper atoms. Closed aperture exposes the self-defocusing nature and orthorhombic phase exhibits stronger nonlinear refraction. Variation in third-order NLO coefficient due to change in phase and morphology of CuNb2O6 confirms the influence of sintering temperature and time. Microrod monoclinic CuNb2O6 possess maximum nonlinear absorption coefficient (6.47 × 10−3 cm/W) and pure orthorhombic CuNb2O6 attains maximum nonlinear refractive index (5.13 × 10−8 cm2/W) along with higher third-order nonlinear optical susceptibility (1.91 × 10−6 esu). Higher thermal nonlinearity resulted in stronger optical limiting action with pure orthorhombic CuNb2O6 (5.16 mW, 1.26 mW) compared to other phases. For understanding the material suitability for laser safety device, nonlinearity and limiting action of CuNb2O6 thin films were demonstrated. Earlier formation of monoclinic phase with morphology change (700 °C) and transition of monoclinic rich mixed orthorhombic phase to pure orthorhombic phase (900 °C) with increase in sintering time (3–12 h) was confirmed by XRD, FTIR and SEM analysis. Thus orthorhombic CuNb2O6 material with stronger self-defocusing and optical limiting action makes it more preference than monoclinic CuNb2O6 for third-order NLO applications.

Growth and characterization of L-Serine: A promising acentric organic crystal

Abstract: An organic competent l -Serine (LS) single crystal which corresponds to the division of acentric category has been grown-up and harvested efficiently by the method of slow solvent evaporation. The orthorhombic structure, P212121 space group and crystallinity of LS have been ascertained employing the analysis of single crystal and powder X-ray diffraction. The existence of functional groups in LS molecule was discovered by FT-Raman and FTIR studies. The transmittance spectrum in UV–Visible profile has been utilized to proclaim its substantial optical constant and to establish its crystalline perfection by means of Urbach energy. The investigations of dielectric and ac conductivity have been employed to estimate the activation energy. To evaluate its mechanical stability, Vickers microhardness examination has been executed and significant mechanical parameters have also been assessed. The fluorescence analysis emphasis the electronic excitation and also its life time was also computed. The findings of laser damage threshold signify exquisite resistance to powerful laser radiation. Using the process of Kurtz-Perry, the efficiency of SHG for LS has been examined and it was found to be 0.84 times of standard KDP. The third order nonlinearity were checked by the approach of Z-scan and affirmed that LS exhibit two photon absorption and self-defocusing effect. The results procured in the current work declared that LS is an enticing applicant for the practicable applications in nonlinear optics.

Growth and characterizaion of urea p -nitrophenol crystal: an organic nonlinear optical material for optoelectronic device application

Abstract: Urea p-nitrophenol, an organic nonlinear optical crystal was synthesized and grown adopting slow evaporation and seed rotation method. Single crystal X-ray diffraction study confirmed the formation of the desired crystal. High resolution X-ray diffraction study showed the defect nature of the crystal. The presence of functional groups in the material was confirmed by FTIR analysis. UV-Vis-NIR study indicates that the grown crystal has a wider transparency region with the lower cutoff wavelength at 423 nm. The grown crystal is thermally stable up to 120 °C as assessed by TG-DTA analysis. The optical homogeneity of the grown crystal was confirmed by birefringence study. The 1064 nm Nd-YAG laser was used to obtain laser induced surface damage threshold which was found to be 0.38, 0.25 and 0.33 GW/cm2 for (0 1 0), (1 1 − 1) and (0 1 1) planes, respectively. The dielectric study was performed to find the charge distribution inside the crystal. The hardness property of the titular material has been found using Vicker’s microhardness study. The optical nonlinearity obtained from third order nonlinear optical measurements carried out using Z-scan technique showed that these samples could be exploited for optical limiting studies.

Analysis on linear and nonlinear optical properties of an efficient semi-organic crystal: Thiourea borate

Abstract: Single crystals of thiourea borate, a novel semi organic nonlinear material has been grown by slow evaporation method at ambient temperature. The compound has been subjected to single crystal XRD to characterise the lattice parameters. Results show that the crystal belongs to Triclinic crystal structure. FTIR spectra were recorded to identify the functional groups present in the sample. The transparency of the optical material was analysed by the UV–Vis-NIR studies. The absorption studies illustrate the UV cut-off wavelength to be 255 nm. The transmission studies indicate rapid and intensive transition to maximum transmission at the cut-off wavelength. The third order nonlinear optical properties of the crystal were studied by Z scan technique using continuous wave 532 nm diode pumped Nd:YAG laser. Closed aperture Z scan studies reveal the crystal to possess negative nonlinearity. Open aperture Z scan pattern indicate saturation absorption within the material. The nonlinear optical parameters such as nonlinear refractive index n2, nonlinear absorption coefficient β and nonlinear susceptibility χ(3) were also determined.

Growth and characterization of unidirectional benzil single crystal for photonic applications

Abstract: Organic nonlinear optical benzil single crystal of fine quality with the dimensions of 168 × 14 mm2 was successfully grown in (100) plane from saturated solution by unidirectional SR method. The structural identity of the grown crystal was confirmed by powder XRD. High-resolution X-ray diffraction analysis indicates the crystalline perfection of the grown benzil crystal. The optical analysis was carried out by UV–visible spectroscopy which shows that the benzil crystal’s cut off wavelength is 437 nm. The dielectric constant and dielectric loss of benzil crystal are found to be very much depending upon temperature and frequency. Ferroelectric nature of grown crystal was identified by P–E hysteresis analysis and to find the values of spontaneous polarization and coercive field. The laser damage threshold energy was studied with the help of Nd:YAG laser. The presence of third harmonic generation was identified by z-scan techniques.

$$\chi ^{(3)}$$ χ ( 3 ) measurement and optical limiting behaviour of novel semi-organic cadmium mercury thiocyanate crystal by Z-scan technique

Abstract: Slow evaporation solution growth technique was used to grow cadmium mercury thiocyanate (CMTC), an organometallic thiocyanate crystal. Single crystal XRD and FTIR spectroscopic analyses confirmed the CMTC compound formation. The grown crystal was characterised for linear optical properties, photoluminescence, thermal stability, dielectric properties, mechanical stability and surface quality. The single-beam Z-scan technique, employing a 532 nm diode-pumped Nd:YAG laser of 50 mW, was used to study the third-order nonlinear optical properties and the optical limiting behaviour of the novel semi-organic CMTC crystal. The nonlinear refractive index ( $$n_2$$ ), the nonlinear absorption coefficient ( $$\beta$$ ), and third-order nonlinear susceptibility ( $$\chi ^{(3)}$$ ) were calculated to be $$8.89\times 10^{-8}\, (\text{cm}^2\,\text{W}^{-1}), 0.021\times 10^{-4}\, (\text{cm W}^{-1})$$ and $$14.27\times 10^{-6}$$ (esu) respectively. Studies on the optical limiting behaviour of the title compound show the linear variation of output power with respect to input power at low intensities and start saturating at higher intensities. The optical limiting threshold value of the title crystal was found to be 31.3 mW.

Investigation on optical, thermal, mechanical, dielectric and ferroelectric properties of non linear optical single crystal guanidinium manganese sulphate

Abstract: Semi organic nonlinear optical crystal of guanidinium manganese sulphate hydrate (GuMnS) was grown from its aqueous solution by slow evaporation solution growth technique. Formation of the crystalline compound was confirmed by powder X-ray diffraction analysis (PXRD).The compound crystallizes in the triclinic crystal system with space group Pī. The functional groups present in the crystal have been identified by FTIR spectroscopic analysis. UV–Vis–NIR spectral study indicates that the grown crystal is transparent in the entire visible region with a lower cut off wavelength 229 nm and the band gap value is found to be 5.06 eV. Nonlinear refractive index (n2), absorption coefficient (β) and third order nonlinear susceptibility (χ(3)) were determined using Z-scan technique. Thermo gravimetric and differential thermo gravimetric analyses (TG-DTG) were performed to analyse the thermal behaviour of the grown crystal. The dielectric constant and dielectric loss were studied as a function of frequency of the applied field. The ferroelectric nature of the grown crystal was analysed by P–E hysteresis loop. The mechanical behaviour of the grown crystal was studied by Vickers’s micro hardness test. The laser induced surface damage threshold (LDT) of the grown crystal was found to be 1.157 GW/cm2. The obtained results show that guanidinium manganese sulphate crystals are potential materials in NLO device applications.

Investigations on 4-methyl benzophenone (4MB) single crystal grown by Czochralski method and its characterization

Abstract: Bulk size 4-methyl benzophenone (4MB) single crystals have been grown by Czochralski method in a period of 8 h. The unit cell parameters of the grown crystals were confirmed by single crystal X-ray diffraction analysis. The lower UV cut-off wavelength of 4MB crystal was studied by UV–Vis NIR spectrum analysis and the cut-off wavelength was found to be 379 nm. The FTIR spectrum confirms the presence of different functional groups present in the crystal. The luminescence properties of 4MB single crystal were described by Photoluminescence spectra. Thermal stability, material decomposition and melting point of the grown crystals were determined by Thermogravimetric/differential thermal analysis measurements. The mechanical stability of the 4MB single crystal was examined using Vickers microhardness test and it was found that the crystal belongs to soft material category. Laser damage threshold measurement was carried out by using Nd:YAG laser. The nonlinear refractive index, nonlinear absorption coefficient and third order nonlinear susceptibility were measured from Z-Scan measurements. The density functional theory calculations for isolated 4MB molecule were performed with B3LYP/6-311 + + G(d,p) level. The electronic properties and polarizabilities of title molecule were calculated.

Synthesis, crystal structure, optical and third order nonlinear optical properties of phosphoric acid pyridine-1-ium-2-carboxylate

Abstract: A semi-organic nonlinear optical material phosphoric acid pyridine-1-ium-2-carboxylate (PAPC) crystal has been synthesized and grown. Vibrational spectral analysis and NMR spectral analysis has been carried out. Mechanical studies on the grown crystal has been performed which disclose the material belongs to soft materials category. The thermal behaviour of the grown crystal has been investigated by thermogravimetric and differential thermal analysis. UV–Visible spectral analysis has been carried out which reveals that the grown crystal is transparent in the entire visible region with the lower cut-off wavelength of 298 nm and the derived optical constant attests the suitability of this material for non-linear optical applications. The third order nonlinearity has been studied by z-scan method and the enhanced third-order nonlinearity shows PAPC is a potential material for device applications. Second harmonic generation efficiency has been studied by Kurtz and Perry powder test and is found as 0.14 times greater than the KDP.

Enhancement of third-order nonlinear optical properties of HMTA stabilized pure and doped ZnS nanoparticles and their electronic structures

Abstract: This study reports the third-order nonlinear optical (NLO) properties of hexamethylenetetramine (HMTA) stabilized pure and transition metals (Cu, Co and Mn) doped ZnS nanoparticles (NPs) and their ...

Growth and characterization of a nonlinear optical material: l -alanine dl -mandelic acid hemihydrate

Abstract: l-Alanine dl-mandelic acid hemihydrate (LADLMAH) an organic nonlinear optical chromophore crystal was synthesized using water as solvent and the crystals were grown by a slow solvent evaporation method. The single crystal X-ray diffraction study reveals that the crystals possess to triclinic system with acentric space group P1. The coordination of different moieties present in the compound and molecular structure were elucidated by vibrational and NMR spectroscopic studies. The lower cut-off wavelength is observed down to 258 nm and direct optical band gap was calculated as 5.20 eV. Second harmonic generation was confirmed by Kurtz–Perry powder method. Discrete thermodynamic properties were carried out by TG–DTA techniques. A multiple shot laser technique was adopted to investigate the surface laser damage of the crystal. The microhardness test was carried out employing one of the as-grown hard crystals and there by hardness number (Hv) and Meyer’s index (n) were assessed. The dielectric behaviour of the grown crystal was studied for different temperatures at different frequencies. The third-order optical nonlinearity parameters of LADLMAH were investigated in detail using a Z-scan technique with Nd:YAG laser at 532 nm.

Optical properties of Eu3+ activated SrLa2O4 red-emitting phosphors for WLED applications

Abstract: The SrLa2−xO4:xEu3+ phosphors are synthesized through high-temperature solid-state reaction method at 1473 K with various doping concentration. Their phase structures, absorption spectra, and luminescence properties are investigated by X-ray diffraction (XRD), UV–Vis spectrophotometer and photoluminescence spectrometry. The intense absorption of SrLa2−xO4:xEu3+ phosphors have occurred around 400 nm. The prominent luminescence spectra of the prepared phosphors exhibited bright red emission at 626 nm. The doping concentration 0.12 mol% of Eu3+ is shown to be optimal for prominent red emission and chromaticity coordinates are x = 0.692, y = 0.3072. Considering the high colour purity and appropriate emission intensity of Eu3+ doped SrLa2O4 can be used as red phosphors for white light emitting diodes (WLEDs).

N-Methylurea Succinic Acid (NMUSA): an optically non-linear organic crystal for NLO device application

Abstract: Slow evaporation solution growth technique was adopted to grow an optically non-linear N-Methylurea Succinic acid crystal. High resolution x-ray diffraction studies showed that the sample was free from crystal imperfection. Single crystal XRD studies showed that these crystals belonged to monoclinic system with P21/n being their space group. Relevant functional groups were identified from their FTIR spectra, while their band gap was evaluated to be 4.35 eV from UV–vis spectra. The grown crystals possess good thermal and mechanical stabilities as elucidated from TG-DTA and Vickers hardness measurements respectively. Laser damage threshold of the sample was found to be 6.9 GW cm−2 when measured using a 1064 nm, 5 Hz, 10 ns Nd:YAG laser. The third order nonlinear optical parameters of the grown NMUSA crystal were found out using Z-scan measurement, which was further used to exploit these crystals for optical limiting applications.