Luminescent Tb/Sm co-doped hydroxyapatite nanoparticles as an imaging probe in N2a cells.

This work reports the synthesis of hydroxyapatite (HAp) nanoparticles co-doped with trivalent terbium (Tb) and samarium (Sm) ions by a surfactant free chemical precipitation method. Co-doping enables to combine the optical properties of Tb and Sm ions. Characterization techniques like X-Ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma-optical emission spectroscopy (ICP-OES), energy dispersive X-ray spectroscopy (EDX) were used to determine the crystalline and structural properties.

Experimental and theoretical investigation on the nonlinear optical properties of LDS 821 dye in different solvents and DNA.

Linear and nonlinear optical properties of near-infrared laser grade dye LDS 821 in different solvents and Salmon Deoxyribonucleic acid (DNA) were studied using spectroscopic and Z-scan techniques. UV-Vis absorption spectrum of the dye shows a bathochromic shift with a decrease in the solvent polarity parameter, and in DNA, the dye exhibits a hypochromic shift. The fluorescence spectrum of the dye does not show any notable correlation with the solvent polarity parameter, but in DNA, the fluorescence intensity of the dye decreases with the incremental addition of DNA.

Solvent assisted evolution and growth mechanism of zero to three dimensional ZnO nanostructures for dye sensitized solar cell applications.

We report the structural engineering of ZnO nanostructures by a consistent solution method using distinct solvents such as ethylene glycol, 1-butanol, acetic acid and water. The growth kinetics are found to depend strongly on the physicochemical properties of the solvent and zeta potential of the colloidal solution. Furthermore, the resulting nanostructures as a photoanode material, displayed a prominent structure dependent property in determining the efficiency of dye-sensitized solar cells (DSSCs).

Exploring the LDS 821 dye as a potential NIR probe for the two photon imaging of amyloid fibrils.

We report a commercially available benzothiazolium based dye LDS 821 (Styryl 9M) as a near infrared fluorescent probe for the detection of lysozyme amyloid fibrils. Change in the photophysical properties of the dye with respect to the change in viscosity of the environment is investigated. Increment in fluorescence lifetime and quantum yield with increment in viscosity proves the dye as a molecular rotor.

Optical characterization and tunable antibacterial properties of gold nanoparticles with common proteins.

The interaction of three proteins, viz. Bovine Serum Albumin (BSA), Human Serum Albumin (HSA) and Hen Egg White Lysozyme (HEWL) with gold nanoparticles (GNPs) is investigated using surface plasmon resonance (SPR) spectroscopy, fluorescence spectroscopy and circular dichroism (CD). Size and morphology of the samples was established using Transmission Electron Microscopy (TEM) and stability studies was established using zeta potential analysis.

Fluorescence resonance energy-transfer-based fluoride ion sensor.

The present work describes an energy-transfer-based fluoride sensor using the highly photo-stable Coumarin 540a (C540a)-Rhodamine 6g (Rh6g) dye pair. Rh6g exhibits a decrease in fluorescence emission, whereas C540a shows no change in response to fluoride. The increase in fluoride concentration decreases the energy transfer efficiency between the C540a donor and Rh6g acceptor in acetonitrile, leading to a subsequent recovery of fluorescence emission from C540a molecules.

Ag nanowire-assisted low threshold WGM lasing from polymer optical fiber.

Whispering Gallery Mode (WGM) emission has been observed from Ag nanowire doped polymer optical fiber laser. Low threshold lasing and high photostability of the active medium has been noticed with a given concentration of Ag nanowires in the microcavity of the fiber. Quantum yield and lifetime measurements of the dye (active medium) with and without nanowires confirm that presence of nanowires enhance the rate of radiative decay of the fluorophore, thereby providing low pump pulse energy for the excitation of lasing modes in the cavity, as compared with a bare dye-doped polymer fiber laser.

Photochemical Degradation of Curcumin: a Mechanism for Aqueous Based Sensing of Fluoride.

The present work describes the enhanced photochemical degradation of natural dye Curcumin in acetonitrile-water mixture in the presence of fluoride upon irradiation with light. The strong basicity of fluoride modifies the solvent environment around Curcumin molecule leading to alkaline mediated degradation of Curcumin which is further accelerated by irradiation with light. The photochemical degradation of Curcumin is studied using absorption and fluorescence spectroscopy and verified using infrared spectroscopy and fluorescence lifetime studies.

Spectral and Lensing Characteristics of Gel-Derived Strontium Tartrate Single Crystals Using Dual-Beam Thermal Lens Technique.

The Dual Beam mode-matched thermal lens spectrometry is a sensible technique for direct measurements of the thermal properties of tartrate crystalline materials. Here we report the measurement of thermal diffusivity of Strontium Tartrate single crystals incorporated with Rhodamine 6G using the thermal lens experiment. The respective crystals were prepared by solution-gel method at room temperature.

Spectral and Non Radiative Decay Studies of Lead Di Bromide Single Crystals by Mode Matched Thermal Lens Technique.

In the present paper, the investigations on the non radiative decay mechanism, optical band gap determination from absorption spectroscopic studies and fluorescence emission by photo luminescence techniques using different excitation wavelengths on gel derived lead di bromide single crystals are reported. Non radiative decay of the sample is studied using high sensitive dual beam mode matched thermal lens technique. For the thermal lensing experiment the crystal in solution phase is incorporated with rhodamine 6G dye for enhancing the absorption of the crystal sample.

Tuning whispering gallery lasing modes from polymer fibers under tensile strain.

Wavelength tuning of whispering gallery lasing modes has been observed from Rhodamine-B-doped polymer fibers under tensile strain. Good quality whispering gallery lasing modes are produced from both solid and hollow fibers by transverse optical pumping. The lasing modes are shifted linearly toward the shorter wavelength side when the fiber is elongated in the axial direction.

Solvent Dependency in the Quantum Efficiency of 4-[(4-Aminophenyl)-(4-imino-1-cyclohexa-2, 5- dienylidene) methyl] Aniline Hydrochloride.

In the present work dual beam thermal lens technique is used for studying the solvent dependency on the quantum efficiency of a novel dye used for biomedical applications. The role of solvent in the absolute fluorescence quantum yield of 4-[(4-Aminophenyl)-(4-imino-1-cyclohexa-2, 5- dienylidene) methyl] aniline hydrochloride is studied using thermal lens technique. It is observed that the variation in solvents and its concentration results considerable variations in the fluorescence quantum yield.

Variations in fluorescence quantum yield of basic fuchsin with silver nanoparticles prepared by femtosecond laser ablation.

Nano structured noble metals have very important applications in diverse fields such as photovoltaics, catalysis, electronic and magnetic devices, etc. In the present work, the application of dual beam thermal lens technique is employed for the determination of the absolute fluorescence quantum yield of the triaminotriphenylmethane dye, basic fuchsin in the presence of silver sol is studied. Silver sol is prepared by femtosecond laser ablation.

Measurement of absolute fluorescence quantum yield of basic Fuchsin solution using a dual-beam thermal lens technique.

The dual beam thermal lens technique is an effective method for the measurement of fluorescence quantum yield of dye solutions. The concentration-dependent quantum yield of a novel dye of triaminotriphenylmethane family in ethanol is studied using this technique. The absolute fluorescence quantum yield is measured and is observed that the reduction in the quantum yield is due to the non-radiative relaxation of the absorbed energy.

Laser emission from the whispering gallery modes of a graded index fiber.

Whispering gallery mode (WGM) laser emission has been observed from rhodamine B doped polymer optical graded index (GI) fiber by transverse pumping with a frequency doubled Q-switched Nd:YAG laser. The propagation and confinement of these modes were also observed. A variation in the free spectral range from 0.

UV-visible photoluminescence of TiO2 nanoparticles prepared by hydrothermal method.

TiO(2) colloidal nanoparticles and nanocrystals are prepared by hydrolysis of titanium isopropoxide employing a surfactant-free synthetic hydrothermal method. The synthesized samples are characterized by X-ray diffraction (XRD), HRTEM and FTIR. The XRD study confirms that the size of the colloidal nanoparticle is around 4 nm which the HRTEM analysis indicates the sizes of the colloidal nanoparticles are in the range of 2.

Shifting of fluorescence peak in CdS nanoparticles by excitation wavelength change.

CdS nanoparticles with different size are prepared by chemical bath deposition method. These particles show strong fluorescence at emission wavelength of 507 nm. It has been observed that this emission peak changes through a range of 147 nm, by varying the excitation wavelengths through 370-480 nm.

Selective mode excitation in dye-doped DNA polyvinyl alcohol thin film.

A solid-state laser based on a dye-doped deoxyribonucleic acid (DNA) matrix is described. A thin solid film of DNA has been fabricated by treating with polyvinyl alcohol (PVA) and used as a host for the laser dye Rhodamine 6G. The edge emitted spectrum clearly indicated the existence of laser modes and amplified spontaneous emission.

Linear and nonlinear optical characteristics of ZnO-SiO2 nanocomposites.

We present the spectral and nonlinear optical properties of ZnO-SiO2 nanocomposites prepared by colloidal chemical synthesis. Obvious enhancement of ultraviolet (UV) emission of the samples is observed, and the strongest UV emission of a typical ZnO-SiO2 nanocomposite is over three times stronger than that of pure ZnO. The nonlinearity of the silica colloid is low, and its nonlinear response can be improved by making composites with ZnO.

Luminescence tuning and enhanced nonlinear optical properties of nanocomposites of ZnO-TiO2.

In this article we present the spectral and nonlinear optical properties of ZnO-TiO(2) nanocomposites prepared by colloidal chemical synthesis. Emission peaks of ZnO-TiO(2) nanocomposites change from 340 nm to 385 nm almost in proportion to changes in E(g). The nanocomposites show self-defocusing nonlinearity and good nonlinear absorption behaviour.

Photoluminescence studies on rare earth titanates prepared by self-propagating high temperature synthesis method.

The laser-induced luminescence studies of the rare earth titanates (R2Ti2O7) (R=La, Nd and Gd) using 355 nm radiation from an Nd:YAG laser are presented. These samples with submicron or nanometer size are prepared by the self-propagating high temperature synthesis (SHS) method and there is no known fluorescence shown by these rare earths in the visible region. Hence, the luminescence transitions shown by the La2Ti2O7 near 610 nm and Gd2Ti2O7 near 767 nm are quite interesting.

Side illumination fluorescence emission characteristics from a dye doped polymer optical fiber under two-photon excitation.

Two-photon excited (TPE) side illumination fluorescence studies in a Rh6G-RhB dye mixture doped polymer optical fiber (POF) and the effect of energy transfer on the attenuation coefficient is reported. The dye doped POF is pumped sideways using 800 nm, 70 fs laser pulses from a Ti:sapphire laser, and the TPE fluorescence emission is collected from the end of the fiber for different propagation distances. The fluorescence intensity of RhB doped POF is enhanced in the presence of Rh6G as a result of energy transfer from Rh6G to RhB.

Fabrication and characterization of dye mixture doped polymer optical fiber as a broad wavelength optical amplifier.

Rhodamine 6G and Rhodamine B dye mixture doped polymer optical fiber amplifier (POFA), which can operate in a broad wavelength region (60 nm), has been successfully fabricated and tested. Tunable operation of the amplifier over a broad wavelength region is achieved by mixing different ratios of the dyes. The dye doped POFA is pumped axially using 532 nm, 10 ns laser pulses from a frequency doubled Q-switched Nd: YAG laser and the signals are taken from an optical parametric oscillator.

Chemical sensing with microbent optical fiber.

We propose and demonstrate the possibility of using a permanently microbent bare optical fiber for detecting chemical species. Two detection schemes, viz., a bright-field detection scheme (for the core modes), and a dark-field detection scheme (for the cladding modes) have been employed to produce a fiber-optic sensor.