Green Synthesis of Silver Nanoparticles using Litsea glutinosa L. Leaves and Stem Extracts and their Antibacterial Efficacy

The present study explores the green approach for the preparation of silver nanoparticles (AgNPs) through the reduction of silver nitrate by the cell-free stem and leaf aqueous extracts of Litsea glutinosa (L.glutinosa) and its potential antibacterial activity. The analytical instruments include scanning electron microscopy, Fourier transforms infrared spectroscopy, UV-visible spectroscopy, and X-ray diffraction spectroscopy confirmed the synthesis of smaller, uniformly spherical AgNPs (10-40 nm). The average crystalline size of prepared AgNPs produced by L. glutinosa leaf extract was found to be 19 mm. From UV-visible spectral analysis, the maximum absorbance peak appeared at 444 nm for leaf extract AgNPs different from stem extract AgNPs (422 nm), which are found to be specific for AgNPs. The L.glutinosa stem extract-assisted AgNPs have shown significant antibacterial activity against Bacillus subtilis (Gram-positive) and Escherichia coli (Gram-negative) in comparison to Gentamycin. Hence, the AgNPs obtained by green synthesis can be therapeutically explored against bacterial infections

Spectral Analysis of Nd 3+ Doped Lead Borosilicate Glasses for Efficient Broadband Laser Amplification

International audienceIn this investigation, Nd 3+ doped lead borosilicate glasses (LBS) were prepared with chemical composition of (30-x) PbO – 40 H3BO3 –10 SiO2 – 10 Al2O3 – 10 LiF – x Nd2O3 (where x varies from 0.0, 0.1, 0.5, 1.0 and 2.0 mol%) by conventional melt-quenching method. The spectroscopic analysis can be done using absorption, emission and decay measurements. The oscillator strengths (fexp and fcal) and the evaluated Judd-Ofelt (JO) intensity parameters (Ωλ, λ = 2, 4 and 6) determined from the absorption spectrum. From the emission spectra, three NIR bands observed at 903, 1060 and 1334 nm corresponding to the 4 F3/2→ 4 I9/2, 4 F3/2 → 4 I11/2 and 4 F3/2 → 4 I13/2 transitions, respectively for which the effective bandwidths (ΔλP), radiative transition probabilities (AR) branching ratios (βR) and stimulated emission cross-sections (σse) are also evaluated. The intensities of emission bands increased with the increase of Nd 3+ ions concentration upto 1.0 mol% and then decreased at higher concentrations due to the concentration quenching. From the analysis of emission properties, it is concluded that the Nd 3+ doped LBS glasses could be useful for various photonic applications in different fields. Introduction. In the present scenario, the multicomponent oxide glasses have been attracted the several researchers and technologists due to their unique properties such as trouble-free casting, good transparency, solubility of rare earth ions and long term stability [1]. However, due to the increasing demand of the rare earth doped multi-component oxide laser glasses in various applications such as higher order harmonic generation [2], time-resolved laser spectroscopy [3], plasma generation [4] and in many areas, a good host is highly essential to improve the quantum efficiency to meet the aforesaid applications. In the process of searching various oxide glasses, the host glasses with heavy metallic components such as lead oxide, aluminum oxide and silicon dioxide are found to have the ultrafine transparency, high thermal stability, low melting point, infrared transparency, corrosion resistance and also good solubility of rare earth ions [5]. In these multiconstituents, the role of lead in the glass network is to reduce the phonon energy of borate (~1400cm-1) and also to increase the mechanical stability by lowering the melting temperature. Hence, in the present study lead borosilicate glasses (LBS) are chosen as a host matrix to meet the specified applications. Among the available rare earth ions, the neodymium (Nd 3+) ion is identified as one of the most efficient ions for solid state lasers with the emission wavelength at 1060 nm as well as the possibility for lasing action at other wavelengths such as 1800, 1350 and 880 nm which are be useful for broadband laser amplifiers and other photonic applications

Luminescence properties of Dy3+ doped lithium zinc borosilicate glasses for photonic applications

Different concentrations of Dy3+ ions doped lithium zinc borosilicate glasses of chemical composition (30-x) B2O3 - 25 SiO2 -10 Al2O3 -30 LiF - 5 ZnO - x Dy2O3 (x = 0, 0.1, 0.5, 1.0 and 2.0 mol%) were prepared by the melt quenching technique. The prepared glasses were investigated through X-ray diffraction, optical absorption, photoluminescence and decay measurements. Intensities of absorption bands expressed in terms of oscillator strengths (f) were used to determine the Judd-Ofelt (J-O) intensity parameters Ωλ (λ = 2, 4 and 6). The evaluated J-O parameters were used to determine the radiative parameters such as transition probabilities (AR), total transition probability rate (AT), radiative lifetime (τR) and branching ratios (βR) for the excited 4F9/2 level of Dy3+ ions. The chromaticity coordinates determined from the emission spectra were found to be located in the white light region of CIE chromaticity diagram

Acoustic Response of an Isotropic Beam Under Axially Variable Loads Using Ritz and Rayleigh Integral Methods

Vibro-acoustic response of an isotropic beam under the action of variable axial loads (VALs), is presented in the study. Effects of six different types of VALs and three types of end conditions on buckling, free vibration and sound radiation characteristics are investigated. Static buckling and free vibration behaviours using shear and normal deformable theorem and Ritz method. However, the forced vibration response is evaluated using modal superposition method and the acoustic radiation characteristics are obtained using Rayleigh integral. The nature of variation of VALs and end conditions are influencing buckling and free vibration characteristics remarkably. Results indicate that the acoustic response is highly sensitive to the nature of VAL and intensity of the VAL. In general, sound power at resonance decreases when the magnitude of VAL is increased

Effect of lamination schemes on natural frequency and modal damping of fiber reinforced laminated beam using Ritz method

The current study focussed on analysing natural frequency and damping of laminated composite beams (LCBs) by varying fiber angle, aspect ratio, material property and boundary conditions. Ritz method with displacement field based on the shear and normal deformable theory is used and the modal damping is calculated using modal strain energy method. Effects of symmetric angle-ply and cross-ply, anti symmetric cross-ply, balanced and quasi-isotropic lay up schemes on modal damping are presented for the first time. Results revealed that influence of lay-up scheme on natural frequencies is significant for the thin beams while the modal damping of the thin beams are not sensitive to lay-up scheme. However, the lay-up scheme influences the damping significantly for the thick beams. Similarly, high strength fiber reinforced LCBs have higher natural frequency while low strength fiber reinforced LCBs have higher damping due to the better fiber-matrix interaction

Structural and electrical properties of Li4Ti5O12 anode material for lithium-ion batteries

In this work we investigate Li4Ti5O12 (LTO) anode material synthesized by conventional solid state reaction method calcined at 850 °C for 16 h. Thermal analysis reveals the temperature dependence of the material properties. The phase composition, micro-morphology and elemental analysis of the compound are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectra (EDS) respectively. The results of XRD pattern possessed cubic spinel structure with space group Fd-3m. The morphological features of the powder sample are in the range of 1.1 μm. The EDS spectra confirm the constituent elemental composition of the sample. Electrical conductivity measurement at different frequencies and temperatures had been carried out; and at room temperature it is found to be 5.96 × 10−7 S/cm. Besides, for the different frequencies applied, the activation energies were calculated and obtained to be in the range of 0.2–0.4 eV. Keywords: Anode, Spinel Li4Ti5O12, Solid-state reaction, XRD, Electrical propertie