Green synthesis of nanoparticles using various plant materials opens a new scope for the phytochemist and discourages the use of toxic chemicals. In this article, we report an eco-friendly and low-cost method for the synthesis of silver nanoparticles (AgNPs) using Andean blackberry fruit extracts as both a reducing and capping agent. The green synthesized AgNPs were characterized by various analytical instruments like UV-visible, transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The formation of AgNPs was analyzed by UV-vis spectroscopy at = 435 nm. TEM analysis of AgNPs showed the formation of a crystalline, spherical shape and 12-50 nm size, whereas XRD peaks at 38.04°, 44.06°, 64.34° and 77.17° confirmed the crystalline nature of AgNPs. FTIR analysis was done to identify the functional groups responsible for the synthesis of the AgNPs. Furthermore, it was found that the AgNPs showed good antioxidant efficacy (>78%, 0.1 mM) against 1,1-diphenyl-2-picrylhydrazyl. The process of synthesis is environmentally compatible and the synthesized AgNPs could be a promising candidate for many biomedical applications.

The linewidth narrowing observed in Brillouin fiber ring lasers is studied within the framework of the usual three-wave model of stimulated Brillouin scattering. We show that the phase noise of the pump laser is transferred to the emitted Stokes wave after being strongly reduced and smoothed under the combined influence of the acoustic damping and the cavity feedback. We then derive a simple analytical relation connecting the full width at half maximum of the Stokes linewidth to that of the pump laser.PACS number͑s͒: 42.55.Ϫf, 42.65.Es, 42.25.Kb The Brillouin fiber ring laser is a highly coherent light source. Experiments have shown that the linewidth of the Stokes radiation emitted by this laser can be several orders of magnitude narrower than that of the incident beam used to pump it ͓1͔. Although this effect is commonly used in many applications such as gyroscopes ͓2͔ or temperature sensors ͓3͔, it is not clearly understood. In fact, the questions related to the noise properties or to the temporal coherence of Brillouin lasers have not yet been attentively examined from the theoretical point of view. Brillouin lasers and conventional lasers have common noise sources. For instance, fluctuations of the pumping mechanism or of the cavity length alter the spectral purity of the emitted wave in both systems. However, contrary to lasers with population inversion, it is not spontaneous emission but spontaneous scattering that fundamentally limits the degree of monochromaticity of the Stokes radiation. The aim of this paper is to analyze the role of the different noise sources existing in Brillouin fiber ring lasers and to characterize their influence on the temporal coherence of the laser. In particular, we will show that the phase noise of the pump laser is the predominant noise source and we will study in detail the connection between the linewidth of the Brillouin laser and that of its pump laser.Our theoretical study enters within the framework of the usual three-wave model of stimulated Brillouin scattering ͑SBS͒. This model reproduces properly most of the dynamical behaviors experimentally observed in Brillouin generators ͓4͔ or lasers ͓5͔. It readswhere p , p , and B represent, respectively, the complex amplitudes of the pump, Stokes, and acoustic waves. These equations in dimensionless form have been obtained by neglecting the weak attenuation of the fiber. The time is normalized to the transit time of the light inside the fiber. is the space coordinate that is normalized to the fiber length. The fields p and s are measured in units of the maximum pump field available at the entrance end of the fiber. g is the SBS coupling constant and ␤ A represents the normalized damping rate of the acoustic wave. f (,) is a Langevin noise term describing the random thermal fluctuations of density ͑i.e., spontaneous scattering͒ occurring inside the fiber ͓6͔. This noise is a zero-mean Gaussian process and it is ␦ correlated both in space and time. In the chosen normalization, f is of the order of 10 Ϫ6 whereas the amplit...

Silver nanoparticles (AgNPs) are fabricated using Sacha inchi (SI) or (Plukenetia volubilis L.) leaf extract as non-toxic reducing agent with particle size ranging from 4 to 25 nm. Optical, structural and morphological properties of the synthesized nanoparticles have been characterized by using Visual, UV-Vis spectrophotometer, transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis. Selected area electron diffraction (SAED) confirmed the formation of metallic Ag. Infrared spectrum measurement was carried out to hypothesize the possible phytochemicals responsible for stabilization and capping of the AgNPs. It shows the significant antioxidant efficacy in comparison with SI leaf extracts against 1,1-diphenyl-2-picrylhydrazyl. From the results obtained it is suggested that green AgNPs could be used effectively in future engineering and medical concerns.

Biofabrication of copper oxide nanoparticles (CuO-NPs) of a desired size remains a significant challenge. In this report, CuO-NPs were fabricated by treating 10 mM copper nitrate with Andean blackberry fruit (ABF) and leaf (ABL); and evaluated its antioxidant activity. As-prepared NPs characterization were determined by UVvisible spectrophotometry, Dynamic light scattering (DLS), Transmission electron microscopy (TEM) with selected area electron diffraction (SAED) and X-Ray Diffraction (XRD) analysis. UV-visible spectroscopy showed an electronic excitonic transition at 250 to 255 nm clearly reveals the formation of ABF and ABL CuO-NPs. DLS analysis demonstrated mean diameter of ABF CuO-NPs (43.3 nm) smaller than ABL CuO-NPs (52.5 nm). TEM with SAED confirmed the CuO-NPs are spherical and partial crystalline nature. Furthermore, the antioxidant efficacy of ABF CuO-NPs showed (89.02%, 1mM) whereas ABL CuO-NPs (75.92 %, 1mM) against 1, 1-diphenyl-2-picrylhydrazyl. From the results obtained it is suggested that green CuONPs could be used effectively in future biomedical concerns.

A novel approach was applied to synthesize silver nanoparticles using starch under sonication. Colloidal silver nanoparticles solution exhibited an increase of absorption from 420 to 440 nm with increase starch quantity. Transmission electron microscopy followed by selected area electron diffraction pattern analysis indicated the formation of spherical, polydispersed, amorphous, silver nanoparticles of diameter ranging from 23 to 97 nm with mean particle size of 45.6 nm. Selected area electron diffraction (SAED) confirmed partial crystalline and amorphous nature of silver nanoparticles. Silver nanoparticles synthesized in this manner can be used for synthesis of 2-aryl substituted benzimidazoles which have numerous biomedical applications. The optimized reaction conditions include 10 ml of 1 mM AgNO3, 25 mg starch, 11 pH range, and sonication for 20 min at room temperature.