Photo-Luminescence study of Ba3Gd1-x(BO3)3 : X Ce3+ phosphor

The polycrystalline powder sample of Ce3+ activated barium gadolinium borate phosphors Ba3Gd1-x(BO3)3 : X Ce3+(0.01 ≤ X ≤ 0.06 ) are prepared by solution combustion. Formation of phosphor in desired crystalline phase confirmed by powder XRD characterization & FTIR. A SEM image shows the irregular grains with average particle size 2.5μm. The excitation spectrum consists of a single broad absorption band from 200 to 400 nm with the prominent excitation peak at 343 nm [2F5/2 to 5D1 of Ce3+ ions]. Strongest emission peak of 488nm [5D1→ 2F5/2] and weak of 501nm [5D1→ 2F7/2] wavelength which is of blue light is observed at 343nm UV light excitation. Ba3Gd1-x(BO3)3 : X Ce3+ phosphor emits blue light under UV excitation. Maximum PL emission takes place at 3 mole percentage of Ce3+. Concentration quenching for Ce3+ ions is studied. Hence Ba3Gd1-x(BO3)3 : X Ce3+ is new UV excited blue emitting phosphor useful for UV/Blue chip WLEDs.

EXTH-54. PHOTODYNAMIC ONCOLYTIC VIROTHERAPY INCORPORATING GENETICALLY ENGINEERED PHOTOSENSITIZER KILLERRED FOR THE TREATMENT OF CENTRAL NERVOUS SYSTEM MALIGNANCIES

BACKGROUND Photodynamic therapy (PDT) is a targeted cancer therapy utilizing tumor-specific accumulation of photosensitizers and generation of reactive oxygen species (ROS) upon receiving specific light. The deadly CNS malignancies, high-grade gliomas and malignant meningioma, represent excellent candidates for this therapeutic method due to accessibility to light irradiation at the time of surgery. On the other hand, oncolytic virotherapy using a genetically engineered oncolytic herpes simplex virus (oHSV), has been intensively investigated as a multi-mechanistic therapy against these tumors. One of the advantages of oHSV is its ability to incorporate therapeutic transgenes. Our study aims to address our hypothesis that incorporating KillerRed, the first fully genetically encoded photosensitizing fluorescent protein, into oHSV will establish photodynamic oncolytic virotherapy that enhances tumoricidal efficacy as a novel treatment approach to CNS neoplasms. METHOD The optical properties of the intracellular KillerRed protein expressed in cells were determined by scanning by a multi-mode microplate reader to determine the optimal irradiation wavelength. In vitro efficacy of KillerRed-mediated PDT was tested using human glioblastoma and malignant meningioma cell lines. oHSV G47delta expressing KillerRed was constructed by a bacterial artificial chromosome-based method. KillerRed-transduced cells were confirmed to express red fluorescence, followed by irradiation by an amber color LED. Cell death and viability were assessed by DAPI staining and MTS assay, respectively. ROS generation post light treatment was assessed by DCF-DA cellular ROS assay. RESULTS KillerRed had an excitation peak at 580-585nm in transduced cells. Light irradiation by an amber LED after infection with G47delta-KillerRed induced increased cell growth inhibition and death compared with virus infection without light or light alone. Increased ROS production was observed following KillerRed PDT. CONCLUSION G47delta-KillerRed enables a combination of oncolytic virus therapy and PDT to augment tumor killing. This approach is being tested in in vivo mouse models using potent focused laser irradiation.

Red-Emitting Phosphor Ca2MgSi2O7: Sm3+, Eu3+ for UV White Light-Emitting Diodes

In this research, a series of Ca2MgSi2O7: 2% Sm3+, x% Eu3+ (x=4, 5, 6, 7, 8) red phosphors were synthesized using the high-temperature solid-phase method. The phase and luminescence properties of the samples were investigated using an X-ray diffractometer and a photoluminescence spectrometer. The results showed that the synthesized samples were of pure phase, and the introduction of small amounts of Sm3+ and Eu3+ had no significant impact on the crystal structure of the phosphors. It is observed from the phosphor spectra that the co-doped samples exhibited intense red-light emission corresponding to that of Eu3+ at 613 nm when excited at the strongest excitation peak of Sm3+ (401 nm); here, the emission peak intensity of Eu3+ increased by a factor of 5.3. It is found that resonant nonradiative energy transfer occurs from Sm3+ to Eu3+ in the sample, and the energy transfer efficiency reaches up to 44%. The calculated critical distance for energy transfer is 16.117 Å and the concentration interrupt mechanism is an electric dipole-dipole (d-d) interaction. The color coordinates of the samples are all located in the red region (0.6319, 0.3676) with a color purity of ~ 89.3%. The samples exhibited thermal stability of up to 68.6% of that at room temperature when heated to 150˚C . The LED samples packaged with the phosphors emitted warm white-light with a color temperature (CCT) of 5553 K and a color rendering index (Ra) of 84.8. The magnesium yellow feldspar silicate phosphor is suitable as the red component in white LED trichromatic phosphors and has potential applications in solid-state lighting.

The Optical Properties of Dy3+ Doped LaPO4 Phosphors Prepared by Solid State Reaction Method

Luminescent nanomaterials are used in everyday life due to their employment in distinct fields of science and technology, like cathode ray tubes (CRTs), flat panel display devices, temperature sensors, lasers, solar-cells, biological imaging, and solid-state lighting but also as carriers for miscellaneous therapeutic drugs. We have prepared dysprosium Dy3+ (0.5 mol %) doped lanthanum phosphate (LaPO4) phosphor by solid state reaction method. The excitation spectra of synthesized phosphor at 595 nm monitoring were composed of broadband and a series of sharp peaks, the strongest excitation peak at 254, 271, and 350 nm. The main emission spectra of samples under 254, 271, and 350 nm excitation are Dy3+ (0.5 mol %) doped LaPO4 phosphor observed at 477 and 573 nm corresponding to blue and yellow color. The broadband emission is the characteristic of the allowed f-h transition of Dy3+ ions. The corresponding emission band is observed due to the (blue emission) 4f9/2→6h15/2, (yellow emission) 4f9/2→6h13/2 transition of Dy3+ ions. All the samples have been characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL) techniques.

INTERACTION OF 3-HYDROXY PYRIDINE AND SURFACTANT MICELLES: A FLUORESCENCE STUDIES

Objective: Micellar solubilization is a powerful alternative for dissolving hydrophobic compound in aqueous environment. 3-hydroxy pyridine (3- HP) derivatives are the potential endogenous photosensitizers. 3-HP derivatives show protective effect in clinical extreme condition such as hypoxia, hyperthermia, hypokinesia. Micellization of 3-HP followed by solubilization would catalyze its pharmaceutical activities which may serve better results in medicinal and analytical fields. Methods: Fluorescence and absorption spectroscopy techniques are used to monitor the micellar solubilization studies of 3-HP. Solubilization studies of 3-HP with various anionic, cationic and nonionic surfactants have been performed in aqueous medium around 23–25°C temperature. The solubilization action of the surfactant has also been determined by theoretical calculated spectral parameters such as empirical fluorescence coefficient, quantum yield, stokes, shift and molar absorption coefficient. Results: 3-HP shows fluorescence excitation peak at 315 nm and emission peak at 390 nm respectively while the absorbance of 3-HP has been found to be maximum at 305 nm. The fluorescence as well as the theoretically calculated spectral data has been used to characterize the hetero environment of the micelles in terms of their polarity, probe solubilization site and critical micelle concentration. Conclusion: This article briefly discusses the importance of surfactants in biological system model as well as the use of micelles in pharmacy as an important tool that finds numerous applications.

Higher order mode supercontinuum generation in tantalum pentoxide (Ta2O5) channel waveguide

We fabricated tantalum pentoxide (Ta2O5) channel waveguides and used them to experimentally demonstrate higher-order mode supercontinuum (SC) generation. The Ta2O5 waveguide has a high nonlinear refractive index which was in an order magnitude of 10–14 cm2/W and was designed to be anomalously dispersive at the pumping wavelength. To the best of our knowledge, this is the first time a higher-order mode femtosecond pump based broadband SC has been measured from a nonlinear waveguide using the phase-matching method. This enabled us to demonstrate a SC spectrum spanning from 842 to 1462 nm (at − 30 dB), which corresponds to 0.83 octaves, when using the TM10 waveguide mode. When using the TE10 mode, the SC bandwidth is slightly reduced for the same excitation peak power. In addition, we theoretically estimated and discussed the possibility of using the broadband higher-order modes emitted from the Ta2O5 waveguide for trapping nanoparticles. Hence, we believe that demonstrated Ta2O5 waveguide are a promising broadband light source for optical applications such as frequency metrology, Raman spectroscopy, molecular spectroscopy and optical coherence tomography.

Incorporation of Fluorescent Dyes in Electrospun Chitosan/Poly(ethylene oxide)

Polymeric films have been increasingly investigated due to the ease of miniaturization and integration in several sensor devices. Films obtained from the electrospinning technique have a controlled diameter and homogeneity, and substances can be incorporated into the polymeric network. Electrospinning fiber of chitosan (Ch) and poly(ethylene oxide) (PEO) was obtained from solutions prepared at different concentrations in acetic acid, and varying the distance and the voltage applied. The obtained films were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and UV-Visible specular reflectance spectra (UV-SRS). The best conditions for electrospinning were obtained for a 2% m/v (Ch + PEO) solution in the ratio 90:10% m/m (Ch:PEO), applied voltage of 18 kV, and 18 cm distance between the capillary tube and collector. Acridine orange, sodium fluorescein, and erythrosine fluorescence dyes were successfully incorporated into Ch:PEO films. The spectrofluorometric spectra of the films showed excitation and emission processes and the acridine orange film showed evidence of excimer formation by the presence of an excitation peak at 569 nm. Ch-PEO films with the incorporation of fluorescent dyes may well be used as flexible probes or sensors in colorimetric devices in biochemical applications.

Highly sensitive detection of Cr(VI), Pb(II) and Cd(II) ions by a new fluorescent sensor based on 4-amino-3-hydroxynaphthalene sulfonic acid-doped polypyrrole

A new electrosynthesized, fluorescent 4-amino-3-hydroxynaphthalene-1-sulfonic acid-doped polypyrrole (AHNSA-PPy) was used for the detection of Cr(VI), Pb(II) and Cd(II) heavy metallic ions. The optical properties of AHNSA-PPy were studied by UV-VIS absorption and fluorescence spectrometry in diluted DMSO solutions. UV-VIS spectrum showed a main band at 260 nm, a moderate band at 240 nm, and shoulders at 285, 295, 320 and 360 nm, whereas the fluorescence spectrum presented an excitation peak at 330 nm and a main emission peak at 390 nm with a shoulder at 295 nm. The effects of heavy metallic ions, including Cr(VI), Pb(II), and Cd(II), on the AHNSA-PPy UV-VIS absorption and fluorescence spectra were investigated. AHNSA-PPy fluorescence spectra were strongly quenched upon increasing the Cr(VI), Pb(II) and Cd(II) concentrations. Linear Stern-Volmer relationships were established, and polynomial equations for Pb(II) and Cd(II) were obeyed, indicating the existence of a AHNSA-PPy dynamic fluorescence quenching mechanism for Cr(VI) and a combination of dynamic and static fluorescence quenching for Pb(II) and Cd(II). The AHNSA-PPy sensor showed high sensitivity for fluorescence detection of the three heavy metallic ions, with very low limits of detection (3σ) of 1.4 nM for Cr(VI), 2.7 nM for Cd(II) and 2.6 nM for Pb(II). Therefore, this very sensitive quenching fluorimetric sensor is proposed for the detection of trace, toxic heavy metallic ions in the environment.

Real-time monitoring of the in vivo redox state transition using the ratiometric redox state sensor protein FROG/B

The intracellular redox state is one of the key factors regulating various physiological phenomena in the cell. Monitoring this state is therefore important for understanding physiological homeostasis in cells. Various fluorescent sensor proteins have already been developed to monitor intracellular redox state. We also developed fluorescent redox sensor proteins named Oba-Q and Re-Q, the emissions of which are quenched under oxidized and reduced conditions, respectively. Although these sensors were useful to visualize the redox changes in the cell over time, they have the weakness that their emission signals are directly influenced by their in situ expression levels. To overcome this problem, we developed a redox sensor protein with a single excitation peak and dual variable emission peaks. This sensor protein shows green emission under oxidized conditions and blue emission under reduced conditions. We therefore named this sensor FROG/B, fluorescent protein with redox-dependent change in green/blue. By using this sensor, we successfully measured the changes in intracellular redox potentials in cyanobacterial cells quantitatively caused by light/dark transition just by calculating the ratio of emission between green and blue signals.