U.S. Raikar

Core-cladding mode resonances of long period fiber grating in concentration sensor

Long period fiber grating (LPFG) is photoinduced fiber device that facilitates the coupling of core mode to different cladding modes resulting into series of transmission dips in the transmission spectrum. Here we present LPFG chemical sensor to determine the concentration of Manganese in water at ppm level. We fabricated LPFG of period 600µm in single mode communication fiber using 12W carbon dioxide laser applying point by point method. The fabricated LPFG is directly used as chemical sensor since cladding modes coupled to core mode directly come in contact with surrounding chemicals. Concentration of manganese in our collected sample is found to be 0.0329ppm. The result is verified with sophisticated Atomic Absorption Spectrometer (AAS).

Chemical sensor for nitrate in water using long period optical fiber grating fabricated by point by point method

We present long period grating (LPG) fabrication and application of LPG as chemical sensor. We fabricated LPG of grating period 610μm in single mode communication grade fiber using point by point method. Here we used 12watt CO2 laser to irradiate the fiber. The behavior of resonance wavelength of LPG was studied by immersing it in nitrate solution of concentration ranging from 10ppm to 50ppm. The results showed the linear behavior of resonance wavelength of LPG that can be used to determine the concentration of nitrate in water.

Studies of the photophysics of highly fluorescent Red Mega 480 laser dye in solutions: Steady state spectroscopy.

The absorption and fluorescence spectra of highly fluorescent industrially useful medium sized Red Mega 480 dye have been studied in various solvents at 298 K. The solute photophysical behavior depends strongly on the solute-solvent interactions. In order to understand the effect of inter molecular interactions on spectral behaviors of the dye in different solvents extent of this behavior can be analyzed by linear solvation energy relationships. In addition, ground and excited state dipole moments were evaluated by various methods. It is observed that excited state dipole moment (μe) is larger than the ground state (μg), absorption spectra show a bathochromic shift with increasing polarity indicating that transition involved is π→π(∗) and Onsager cavity radius is determined by atomic increment method.

Photo physical studies of silver nanoparticles on ADS740WS fluorescent dye

This paper describes the results of a new fluorescent laser dye ADS740WS is in attachment with silver nanoparticles of size 4-12nm. The main purpose of our research is to know the influence of silver nanoparticles on our chosen ADS740WS fluorescent dye. The attachment of AgNPs with ADS740WS possesses quenching in optical absorption and fluorescence. Photo physical investigations reveal strongly that quenching is due to size, shape and coupling between nanoparticles with adsorbed dye. It is also due to the energy transfer between silver nanoparticles to the dye. Quenching in fluorescence using AgNPs with ADS740WS leads to advancement in printing, painting, lithographic industries and biomolecular labeling.

Green biosynthesis of CuO & Ag–CuO nanoparticles from Malus domestica leaf extract and evaluation of antibacterial, antioxidant and DNA cleavage activities

The reactivity of metallic and bimetallic nanoparticles of copper and silver towards in vitro study has been quantitatively investigated. Here, we report an easy synthesis of nanoparticles by the green method using Malus domestica leaf extract, which acts as a good stabilizing agent. The synthesized CuO and Ag–CuO nanoparticles have shown Surface Plasmon Resonance maxima (SPR) at 335 and 440 nm, respectively. The particles are spherical and crystalline in nature with average sizes between 18 and 20 nm. The Malus domestica leaf-capped nanoparticles have exhibited interesting antibacterial activity with both Gram-positive and Gram-negative bacteria at microgram concentrations. The antioxidant activity of the synthesized nanoparticles has also been measured on the basis of the free radical scavenging activity by the DPPH (1,1-diphenyl 2-picrylhydrazyl) method. Moreover, the DNA cleavage activities of the synthesized nanoparticles have been screened by agarose gel electrophoresis using the E. coli pBR322 plasmid as a target. Hence. owing to the biologically active nature of the synthesized nanoparticles, these greenly synthesized NPs act as a potent therapeutic agent.

Green synthesized multifunctional Ag@Fe2O3 nanocomposites for effective antibacterial, antifungal and anticancer properties

Multifunctional Ag@Fe2O3 nanoparticles were synthesized by employing a green Adathoda vasica leaf extract assisted process. The synthesized nanoparticles were subjected to FTIR, UV-Vis, PXRD and HRTEM measurements for chemical, structural and morphological studies. It is found that vasicine/quinazoline alkaloids present in the extract are responsible for the stability of the nanoparticles. The green synthesized Ag@Fe2O3 nanoparticles showed excellent antibacterial, antifungal and anticancer activity. The green synthesized Ag@Fe2O3 nanoparticles showed better antibacterial activity against Gram positive as well as Gram negative bacteria as compared to previous communications. They have less hazardous effects because of the involvement of the leaf extract in the synthesis of the nanoparticles rather than hazardous chemicals. The present investigation points out that the synthesized nanoparticles are promising in targeted drug delivery systems, bactericides and fungicides, and may be used for magnetic hyperthermia cancer therapy.

Fluorescence Enhancement of C 314 Laser Dye Based on ICT between C 314 Laser Dye and Green Synthesized Gold Nanoparticles

This paper describes synthesis of gold naoparticles (AuNP’s) using green tea leaves and the effect of Coumarin 314 (C314) laser dye is in attachement with the gold and silver nano particles. The main purpose of our research is to study the green synthesis of nanoparticles and to know the influence of green synthesized gold nano particles on C314 laser dye. The attachment of AuNP’s with C314 laser dye possesses enhancement in optical absorption and fluorescence. Photo physical investigations reveal strongly the enhancement is due to Plasmon resonance effect over the ICT excited state promoting an increase of its radiative rate constant (metal Plasmon-coupled emission effect) and also due to the energy transfer between gold nano particles to the dye. Enhancement in fluorescence using AuNP’s with C314 laser dye leads to advancement in important industrial applications like optical brighteners, fluorescence indicators, laser dyes, enzymology, blood thinners, treating the cancer affected cells, and even as sunburn preventives.