Showing papers by "G. Vinitha published in 2020"

Influence of gold nanoparticles on the nonlinear optical and photoluminescence properties of Eu2O3 doped alkali borate glasses.

Abstract: Alkali borate glasses activated with trivalent europium ions and rooted with gold (Au) nanoparticles (NPs) were synthesised through a melt quenching process involving a selective thermochemical reduction and their applicability as photonic materials was assessed in detail. Non-linear optical (NLO) measurements were performed using a Z-scan approach in the wavelength range of 700-1000 nm. The open aperture Z-scan signatures for the Eu3+-containing glasses embedded with and without the Au NPs established a reverse saturable absorption (RSA) at all of the studied wavelengths ascribed to the two-photon absorption (2PA). Surprisingly, the nonlinear optical absorption switched to a saturable absorption (SA) with an increase in the concentration of AuCl3. With the incorporation of the Au NPs, the UV excited photoluminescence (PL) intensity of the Eu3+-doped glasses increased first as a consequence of the local field enhancement by the Au NPs, and subsequently decreased at a higher concentration of AuCl3 due to the reverse energy transfer from the Eu3+ ion to the Au0 NPs. The electronic polarization effect of the host glass enhanced the 5D0→7F4 transition intensity on the incorporation of the gold NPs owing to the gold NP-embedded glasses showing a deep-red emission. The NLO and PL studies suggested that the investigated glasses containing a 0.01 mol% of AuCl3 is practically appropriate for photonic applications.

Facile preparation of high fluorescent carbon quantum dots from orange waste peels for nonlinear optical applications.

Abstract: A facile and eco-friendly hydrothermal method was used to prepare carbon quantum dots (CQDs) using orange waste peels. The synthesized CQDs were well dispersed and the average diameter was 2.9 ± 0.5 nm. Functional group identification of the CQDs was confirmed by Fourier transform infrared spectrum analysis. Fluorescence properties of the synthesized CQDs exhibited blue emission. The fluorescence quantum yield of the CQDs was around 11.37% at an excitation wavelength of 330 nm. The higher order nonlinear optical properties were examined using a Z-scan technique and a continuous wave laser that was operated at a wavelength of 532 nm. Results demonstrated that the synthesis of CQDs can be considered as promising for optical switching devices, bio-scanning, and bio-imaging for optoelectronic applications.

Bioinspired fluorescence carbon quantum dots extracted from natural honey: Efficient material for photonic and antibacterial applications

Abstract: Fluorescent carbon quantum dots were extracted from natural honey using the hydrothermal approach. The XRD and HRTEM investigations confirm the morphology of the carbon quantum dots (CQDs) are spherical shape with a diameter of 8.29 nm. The FTIR and XPS analysis indicate the effective incorporation of nitrogen and sulfuratoms into the CQDs. The sample demonstrated the blue fluorescence by the UV-light illumination ( λ ex = 365 nm ). When excited at 350 nm, the quantum yield of honey CQDs was found to be ∼ 4.192 % at the emission wavelength (431 nm). Crucially for the first time, the existing honey CQDs generates a strong nonlinear optical response relative to some semiconductor QDs. The non-linear optical characterization was investigated utilizing the Z-Scan method. These CQDs exhibit self-defocusing nonlinearity and strong nonlinear performance in the absorption. Also, the agar well diffusion method used to investigate the antimicrobial efficacy of the CQDs against the foodborne pathogens. It is inferred from the existing observations that honey CQDs have been used as effective optoelectronic devices and antimicrobial agents.

Investigations on solid-state parameters of third-order nonlinear optical Ni1−xZnxFe2O4 nanoparticles synthesized by microwave-assisted combustion method

Abstract: In this study, Ni1−xZnxFe2O4 (x = 0, 0.25, and 0.5) nanoparticles were successfully synthesized via microwave-assisted combustion method and characterized by XRD, FTIR, and SEM–EDAX. XRD results enunciate that the nanoparticle crystallizes in cubic spinel structure with an average crystallite size (40.2, 37.2, 35.1 nm), and also, the lattice strain, specific surface area, X-ray density were evaluated. The morphology and chemical compositions of Ni, Zn, Fe, and O elements were confirmed by the SEM–EDAX studies. For all the samples, vibrational stretching modes of Mtetra–O site (597 (S1), 593 (S2), 583 (S3) cm−1) and Moctra–O site (416 (S1), 421 (S2), 422 (S3) cm−1) were related to the distribution of the cation Ni2+/Zn2+ and Fe3+ ions among the octahedral and tetrahedral sites. From the UV–Vis–DRS spectra, the optical energy band gap has been estimated to be 1.75–2.01 eV. The dielectric constant and loss were measured by varying the applied frequency (50 Hz to 200 kHz) at room temperature. The electronic polarizability (α) was calculated using Penn analysis, Clausius–Mossotti equation, and energy band gap value. Third-order nonlinear optical parameters such as the nonlinear absorption coefficients (10−5 cm/W), refractive index (10−9 cm2/W) and the third-order nonlinear susceptibilities (10−6 esu) were determined by Z-scan technique. The antibacterial studies were tested against Bacillus cereus, Staphylococcus aureus, Shigalla flexneri and Klebsiella pneumonia bacterial strains. The existing results point out that the synthesized Ni/Zn/Fe2O4 nanoparticles are possible candidates for photonic devices, optical switches, optical limiting and also for pharmaceutical applications.

Synthesis, growth, optical and third order nonlinear optical properties of l -Phenylalanine d -Mandelic acid single crystal for photonic device applications

Abstract: Organic nonlinear optical l-phenylalanine d-mandelic acid (LPDMA) single crystals have been harvested adopting slow solvent evaporation solution growth technique (SSEST) with growth period of 15 days. The XRD studies of the crystal confirm the non-centrosymmetric nature of the crystal. The presence of functional groups for the formation of the compound was confirmed by Fourier Transform Infrared (FTIR) analysis. The UV–Visible spectral studies ascertained linear optical quality and estimation of optical parameters. The nonlinear optical property was studied from Kurtz-Perry powder technique and Z-scan technique. The quantum chemical calculations such as HOMO–LUMO and Molecular Electrostatic Potential (MEP) were calculated and presented. In order to find out various mechanical parameters such as Vicker’s hardness number (Hv), Mayer’s index (n), yield strength (σy) and stiffness constant (C11), Vicker’s microhardness tester was utilized.

Visible light photocatalytic activity of Mn-doped BiFeO3 nanoparticles

Abstract: The discharges of effluents from the Textile industries contain bleaching and dyeing chemicals which are very harmful to the environment. Thus, managing textile effluents to make zero discharge of ...

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

Abstract: 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.

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

Abstract: 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.

Synthesis, growth, optical and third-order nonlinear optical properties of glycine sodium nitrate single crystal for photonic device applications

Abstract: Glycine and its related compounds play a prominent role in the field of nonlinear optical studies and of fibre optical communication. In the present work, glycine sodium nitrate (GSN) crystal was grown using the method of slow evaporation method. The GSN crystal belongs to space group Cc in the monoclinic system. Using the FTIR spectrophotometer, the different functional groups have been qualitatively identified. A UV–Vis–NIR spectroscopy was used to record the optical absorption spectra, and the optical energy bandgap of GSN crystal is reported. The SHG conversion efficiency of GSN is determined by Kurtz and Perry technique. The Z-scan experiment was conducted to analyze GSN crystal for third-order NLO behavior and it is used to calculate the values of the nonlinear absorption coefficient, nonlinear refractive index, and third-order nonlinear susceptibility. Third-generation harmonic studies reveal that GSN is an excellent material useful in the fabrication of NLO devices due to its nonlinear response characteristics. The thermal stability of the grown crystal was determined through TG/DTA examination. Also photoconductivity studies confirm the negative photoconductive behavior of GSN and I–V characteristics measurement that have been carried out. The dielectric loss is significantly low and this supports defect-free growth of the crystal. These properties of GSN make it a good candidate in the fabrication of NLO devices.

Synthesis, structural, dielectric, laser damage threshold, third order nonlinear optical and quantum chemical investigations on a novel organic crystalline material: Pyrrolidin-1-ium 2-chloro-4-nitrobenzoate 2-chloro-4-nitrobenzoic acid for opto-electronic applications

Abstract: It is reported that a novel third order organic nonlinear optical material namely, Pyrrolidin-1-ium 2-chloro-4-nitrobenzoate 2-chloro-4-nitrobenzoic acid (PCNCN) has been synthesized and grown by isothermal solvent evaporation solution growth technique. Single crystal X-ray diffraction analysis revealed that PCNCN belonged to monoclinic crystal system with a centrosymmetric space group of P21/c. The morphology of the as grown PCNCN crystal compared well with that obtained by theoretically generated morphology. The molecular vibrations of PCNCN were analyzed through Fourier transform infrared and NMR spectrum analyses. Optical properties such as transmittance, photoluminescence, and laser damage threshold were studied. The thermal stability of PCNCN was measured through TG-DTA measurement. The dielectric properties such as dielectric constant, dielectric loss, ac conductivity and activation energy of PCNCN single crystal were studied as a function of frequency at different temperatures. The PCNCN single crystals were further characterized for their third order nonlinear optical properties such as nonlinear absorption coefficient, nonlinear refractive index and optical limiting behavior using continuous wave Nd: YAG laser. The quantum chemical investigations were performed using B3LYP/6-311++G(d, p) basis set.

Synthesis and third order optical nonlinearity studies of toluidine tartrate single crystal supported by photophysical characterization and vibrational spectral analysis

Abstract: The organic nonlinear crystal Toluidine Tartrate (TT) was synthesized, its structure was reinvestigated by X-ray diffraction analysis and investigated theoretically as well as experimentally to examine its nonlinear optical (NLO) behavior. The electron transport mechanism and hydrogen bonding interactions in TT have been explored using the Natural Bond Orbital analysis and optimized geometry calculations. The vibrational spectral investigations of the compound have been carried out using the experimental and computational FT-IR and FT-Raman analyses. UV–vis spectral investigations show the optical absorption of TT crystal at 271 nm and 319 nm and reveal its optical transparency in the visible region. The HOMO LUMO study reveals a 4.5388 eV energy gap which shows its reactivity. Photoluminescence and lifetime studies show a near violet emission with considerable lifetime. The thermal property of the sample was analyzed by TG and DTA analysis and it was found that the TT crystalline compound is stable up to 201 °C. Hyperpolarizability calculations give an augmented value of hyperpolarizability. Z-scan measurements in the pulsed as well as continuous wave laser excitation regimes reveal a substantial decrease in normalized transmittance at higher laser fluences, substantiating the nonlinear behavior and optical limiting application of TT crystals.

Spectral, dielectric, mechanical and optical characteristics of LPDMCl single crystal for nonlinear optical applications

Abstract: A potent semiorganic third order acentric crystal Poly[μ-chlorido-heptachlorido-μ3- l -proline-μ2- l -proline-tetramercury(II)] (LPDMCl) with the chemical formula [Hg4Cl8(C5H9NO2)2]n was crystallized by slow evaporation in water and thereby its second and third order optical nonlinearities are explored using the technique of SHG powder test of Kurtz-Perry and Z-scan single beam respectively. The grown crystalline material was analyzed by single crystal XRD, which discloses the acentric space group P1 of the material with the crystal system of triclinic. From XRD analysis, the obtained peaks were indexed correlated to the orientations of (hkl) plane thus displaying the crystalline purity and perfection. FTIR spectrum detailed the diverse vibrational modes, which signifies the functional groups in LPDMCl. Surface topology of the crystallized salts was accomplished by the examination of SEM. Mechanical, dielectric, linear and nonlinear optical investigation were performed to affirm LPDMCl as an aspiring candidate in establishing proficient nonlinear optical and optical power limiting device for practical applications.

Supramolecular cocrystals of O-H...O hydrogen-bonded 18-crown-6 with isophthalic acid derivatives: Hirshfeld surface analysis and third-order nonlinear optical properties.

Abstract: Two cocrystals of 18-crown-6 with isophthalic acid derivatives, 5-hy­droxy­isophthalic acid and trimesic acid, have been successfully grown by the slow evaporation solution growth technique. Crystal structures of (18-crown-6)·6(5-hy­droxy­isophthalic acid)·10(H2O) (I) and (18-crown-6)·2(trimesic acid)·2(H2O) (II) elucidated by single crystal X-ray diffraction reveal that both cocrystals pack the centrosymmetric triclinic space group P{\overline 1}. The molecules are associated by strong/weak hydrogen bonds, π⋯π and H⋯H stacking interactions. Powder X-ray diffraction analyses, experimental and simulated from single-crystal diffractogram data have been matched. The vibrational patterns in FT–IR spectra are used to identify the functional groups. The band gap energy is estimated by the application of the Kubelka–Munk algorithm. Hirshfeld surfaces derived from X-ray diffraction analysis reveal the type of molecular interactions and their relative contributions. The constructed supramolecular assembly of crown ether cocrystal is thoroughly described. Both cocrystals exhibit a significant third-order nonlinear optical response and it is observed that (I) possesses a significant first-order molecular hyperpolarizability whereas it is negligible for (II).