Methylene blue sensitized dichromated gelatin holograms: a study of their storage life and reprocessibility

The results of an experimental investigation on the storage life and reprocessibility of methylene blue sensitized dichromated gelatin (MBDCG) holograms are reported. The major conclusions of the investigation are: (i) Storage of MBDCG holograms in normal laboratory conditions for long periods is possible and it diminishes somewhat their diffraction efficiency. (ii) The results on short time storage and long time storage are almost similar, thus indicating that the diffraction efficiency can be stabilized through storage in a relatively short period of time. (iii) The deterioration in the diffraction efficiency on storage is less [D(eta) < 20%] for gratings of low/medium initial efficiency (eta < 70%) and it is more for gratings of high initial efficiency. (iv) About 65-95% restoration of the diffraction efficiency can be accomplished through reprocessing. (v) The restoration of diffraction efficiency is almost perfect [R(eta) > 80%] for gratings of low/medium initial efficiency (eta <75%) whereas it is rather imperfect for gratings having high initial efficiency.

Facile hydrothermal synthesis and observation of bubbled growth mechanism in nano-ribbons aggregated microspherical Covellite blue-phosphor

Well uniform microspheres of phase pure Covellite were synthesized through a simple hydrothermal approach using poly vinyl pyrrolidone (PVP) as surfactant. The micro-spheres were constituted of numerous self-organized knitted nano-ribbons of similar to 30 nm thickness. The effect of conc. PVP in the hydrothermal precursor solution on the product morphology was investigated. Based on the out-coming product micro-architecture a growth mechanism was proposed which emphasized bubbled nucleation inside the hydrothermal reactor. In a comparative study on linear optical properties, enhancement of luminescent intensity was observed for nano-ribbon clung microspheres rather than that of agglomerates of distorted particles, which may be attributed to better crystallinity as well as reduced surface defects and ionic vacancies for ribbon-like nano-structures.

Pulsed laser deposited ZnO/ZnO:Li multilayer for blue light emitting diodes

Thin films of ZnO, Li doped ZnO (ZLO) and multilayer of ZnO and ZLO (ZnO/ZLO) were grown on silicon and corning glass substrates by pulsed laser deposition technique. Single phase formation and the crystalline qualities of the films were analyzed by X-ray diffraction and Li composition in the film was investigated to be 15 wt% by X-ray photoelectron spectroscopy. Raman spectrum reveals the hexagonal wurtzite structure of ZnO, ZLO and ZnO/ZLO multilayer and confirms the single phase formation. Films grown on corning glass shows more than 80% transmittance in the visible region and the optical band gaps were calculated to be 3.245, 3.26 and 3.22 eV for ZnO, ZLO and ZnO/ZLO, respectively. An efficient blue emission was observed in all films which were grown on silicon (1 0 0) substrate by photoluminescence (PL). PL measurements at different temperatures reveal that the PL emission intensity of ZnO/ZLO multilayer was weakly dependent on temperature as compared to the single layers of ZnO and ZLO and the wavelength of emission was independent of temperature. Our results indicate that ZnO/ZLO multilayer can be used for the fabrication of blue light emitting diodes. (C) 2011 Elsevier B.V. All rights reserved.

Ba(3)(P(1-x)Mn(x)O(4))(2): Blue/green inorganic materials based on tetrahedral Mn(V)

We describe a blue/green inorganic material, Ba(3)(P(1-x)-Mn(x)O(4))(2) (I) based on tetrahedral MnO(4)(3-):3d(2) chromophore. The solid solutions (I) which are sky-blue and turquoise-blue for x <= 0.25 and dark green for x >= 0-50, are readily synthesized in air from commonly available starting materials, stabilizing the MnO(4)(3-) chromophore in an isostructural phosphate host. We suggest that the covalency/ionicity of P-O/Mn-O bonds in the solid solutions tunes the crystal field strength around Mn(V) such that a blue colour results for materials with small values of x. The material could serve as a nontoxic blue/green inorganic pigment.

Kinetics of adsorption of methylene blue and rhodamine 6G on acrylic acid-based superabsorbents

Superabsorbent polymers (SAPs) of acrylic acid, sodium acrylate, and acrylamide (AM), crosslinked with ethylene glycol dimethacrylate, were synthesized by inverse suspension polymerization. The equilibrium swelling capacities of the SAPs were determined and these decreased with increasing AM content. The adsorption of the two cationic dyes, methylene blue and rhodamine 6G, on the dry as well as equilibrium swollen SAPs was investigated. The amount of the dye adsorbed at equilibrium per unit weight of the SAPs and the rate constants of adsorption were determined. The amount of the dye adsorbed at equilibrium by the SAPs decreased with increasing mol % of AM in the SAPs. The amount of the dye adsorbed at equilibrium was almost equal for the dry and equilibrium swollen SAPs. However, the equilibrium swollen SAPs adsorbed dyes at a higher rate than the dry SAPs. The higher rate of adsorption was attributed to the availability of all the anionic groups present in the fully elongated conformation of the SAPs in the equilibrium swollen state. The effect of initial dye concentration on the adsorption was also investigated and the adsorption was described by Langmuir adsorption isotherms. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Microspherical, hierarchical structures of blue-green-emitting Dy:GdOOH and Dy:Gd2O3

Dy-doped GdOOH microspherical structures were prepared in minutes without using any structure-directing agents, through the microwave irradiation route. The as-prepared product consists of nearly monodisperse sphere-like entities with each one representing a three-level hierarchy in its formation. Dy:GdOOH powder samples show a bright blue-green luminescence under UV excitation, making these structures potentially important in the field of optical and luminescent devices. Finally, thermal conversion to the corresponding oxide structures occurs at modest temperatures, spherical morphology intact and with enhanced luminescence behaviour. (C) 2014 Elsevier B.V. All rights reserved.

A napthelene-pyrazol conjugate: Al(III) ion-selective blue shifting chemosensor applicable as biomarker in aqueous solution

A newly synthesized and crystalographically characterized napthelene-pyrazol conjugate, 1-(5-phenyl-1H-pyrazole-3-ylimino)-methyl]-naphthalen-2-ol (HL) behaves as an Al(III) ion-selective chemosensor through internal charge transfer (ICT)-chelation-enhanced fluorescence (CHEF) processes in 100 mM HEPES buffer (water-DMSO 5 : 1, v/v) at biological pH with almost no interference of other competitive ions. This mechanism is readily studied from electronic, fluorimetric and H-1 NMR titration. The probe (HL) behaved as a highly selective fluorescent sensor for Al(III) ions as low as 31.78 nM within a very short response time (15-20 s). The sensor (HL), which has no cytotoxicity, is also efficient in detecting the distribution of Al(III) ions in HeLa cells via image development under fluorescence microscope.

Comparison of the photocatalytic degradation of trypan blue by undoped and silver-doped zinc oxide nanoparticles

Zinc oxide (ZnO) and silver doped zinc oxide (ZnO:Ag) nanoparticles were prepared using nitrates of zinc and silver as oxidizers and ethylene diaminetetraacetic acid (EDTA) as a fuel via low-temperature combustion synthesis (LCS) at 500 degrees C. X-ray diffraction (XRD) pattern indicates the presence of silver in the hexagonal wurtzite structure of ZnO. Fourier transform infrared (FTIR) spectrum indicates the presence of Ag-Zn-O stretching vibration at 510 cm(-1). Transmission electron microscopy (TEM) images shows that the average particle size of ZnO and ZnO:Ag nanoparticles were found to be 58 nm and 52 nm, respectively. X-ray photoelectron spectroscopy (XPS) data clearly indicates the presence of Ag in ZnO crystal lattice. The above characterization techniques indicate that the incorporation of silver affects the structural and optical properties of ZnO nanoparticles. ZnO:Ag nanoparticles exhibited 3% higher photocatalytic efficiency than pure ZnO nanoparticles. ZnO:Ag nanoparticles show better photocatalytic activity for the degradation of trypan blue (TrB) compared to undoped ZnO nanoparticles. (C) 2014 Elsevier Ltd. All rights reserved.

Negative hyperconjugation and red-, blue- or zero-shift in X-Z center dot center dot center dot Y complexes

A generalized explanation is provided for the existence of the red-and blue-shifting nature of X-Z bonds (Z = H, halogens, chalcogens, pnicogens, etc.) in X-Z center dot center dot center dot Y complexes based on computational studies on a selected set of weakly bonded complexes and analysis of existing literature data. The additional electrons and orbitals available on Z in comparison to H make for dramatic differences between the H-bond and the rest of the Z-bonds. The nature of the X-group and its influence on the X-Z bond length in the parent X-Z molecule largely controls the change in the X-Z bond length on X-Z center dot center dot center dot Y bond formation; the Y-group usually influences only the magnitude of the effects controlled by X. The major factors which control the X-Z bond length change are: (a) negative hyperconjugative donation of electron density from X-group to X-Z sigma* antibonding molecular orbital (ABMO) in the parent X-Z, (b) induced negative hyperconjugation from the lone pair of electrons on Z to the antibonding orbitals of the X-group, and (c) charge transfer (CT) from the Y-group to the X-Z sigma* orbital. The exchange repulsion from the Y-group that shifts partial electron density at the X-Z sigma* ABMO back to X leads to blue-shifting and the CT from the Y-group to the sigma* ABMO of X-Z leads to red-shifting. The balance between these two opposing forces decides red-, zero- or blue-shifting. A continuum of behaviour of X-Z bond length variation is inevitable in X-Z center dot center dot center dot Y complexes.

Fluoranthene-Based Molecules as Electron Transport and Blue Fluorescent Materials for Organic Light-Emitting Diodes

Herein we report the synthesis, characterization, and potential application of his (4- (7,9,10-triphenylfluoranthen-8-yl)pheny)sulfone (TPFDPSO2) and 2,8-bis (7,9,10-triphenylfluoranthen-8-yl) dibenzo b, d]-thiophene 5,5-dioxide (TPFDBTO2) as electron transport as well as light-emitting materials. These fluoranthene derivatives were synthesized by oxidation of their corresponding parent sulfide compounds, which were prepared via Diels-Alder reaction. These materials exhibit deep blue fluorescence emission in both solution and thin film, high photoluminescence quantum yield (PLQY), thermal and electrochemical stability over a wide potential range. Hole- and electron-only devices were fabricated to study the charge transport characteristics, and predominant electron transport property comparable with that of a well-known electron transport material, Alq(3), was observed. Furthermore, bilayer electroluminescent devices were fabricated utilizing these fluoranthene derivatives as electron transport as well as emitting layer, and device performance was compared with that of their parent sulfide molecules. The electroluminescence (EL) devices fabricated with these molecules displayed bright sky blue color emission and 5-fold improvement in external quantum efficiency (EQE) with respect to their parent compounds.

Spectral characterizations and photophysical properties of one-step synthesized blue fluorescent 4 `-aryl substituted 2,2 `:6 `,2 `'-terpyridine for OLEDs application

We have synthesized a series of 4'-aryl substituted 2,2':6',2 `'-terpyridine (terpy) derivatives, namely 4'-(4-methylphenyl)-2,2':6',2 `'-terpyridine (C-1), 4'-(2-furyl)-2,2':6'2 `'-terpyridine (C-2), and 4'-(3,4,5-trimethoxyphenyl)-2,2':6',2 `'-terpyridine (C-3). The synthesized terpy compounds were characterized by elemental analyses, FTIR, NMR (H-1 and C-13), and ESI-Mass spectrometry. Photophysical, electrochemical and thermal properties of terpy compounds were systematically studied. Maximum excitation band was observed between 240 and 330 nm using UV-visible spectra, and maximum emission peaks from PL spectra were observed at 385, 405 and 440 nm for C-1, C-2 and C-3 respectively. Fluorescence lifetime (tau) of the fluorophores was found to be 035 and 1.55 ns at the excitation wavelength of 406 nm for C-1 and C-2 respectively, and tau value for C-3 was found to be 0.29 ns at the excitation wavelength of 468 nm. We noticed that the calculated values of HOMO energy levels were increased from 5.96 (C-1) to 6.08 (C-3) eV, which confirms that C-3 derivative is more electrons donating in nature. The calculated electrochemical band gaps were 2.95, 2.82 and 3.02 eV for C-1, C-2 and C-3 respectively. These blue fluorescent emitter derivatives can be used as an electron transport and electroluminescent material to design the blue fluorescent organic light emitting diode (OLED) applications. (C) 2015 Elsevier B.V: All rights reserved.

Development and Evaluation of Prussian Blue Mediated Glucose Sensor for Reverse Iontophoresis Application

The screen printed electrochemical glucose sensor is developed suitable for revere iontophoresis (RI) application. Glucose oxidase is immobilized on screen printed sensor using crosslinking method. Electrochemical and material characterization studies are conducted on the developed sensor and the obtained results confirm the suitability of the developed sensor for RI application. The developed sensor is validated by conducting clinical investigations on 10 human subjects through RI. A correlation is established between the blood glucose and extracted glucose, and correlation is found to be 0.73. (C) 2015 The Electrochemical Society. All rights reserved.

Boron-doped carbon nanoparticles: Size-independent color tunability from red to blue and bioimaging applications

Here, we report the hydrothermal synthesis of boron-doped CNPs (B-CNPs) with different size/atomic percentage of doping and size-independent color tunability from red to blue. The variation of size/atomic percentage of B is achieved by simply varying the reaction time, while the color tunability is obtained by diluting the solution. With dilution, the luminescence spectra are not only blue-shifted, the intensity increases as well. The huge blue-shift in the emission energy (similar to 1 eV) is believed to be due to the increase in the interparticle distance. The quantum yield with optimum dilution is found to increase with boron doping though it is very low as compared to CNPs and nitrogen-doped CNPs. Finally, we show that B-CNPs with a quantum yield of 0.5% can be used for bioimaging applications. (C) 2015 Elsevier Ltd. All rights reserved.

Fluoranthene derivatives as blue fluorescent materials for non-doped organic light-emitting diodes

In this study, we report synthesis of symmetrically and non-symmetrically functionalized fluoranthene-based blue fluorescent molecular materials for non-doped electroluminescent devices. The solid state structure of these fluorophores has been established by single crystal X-ray diffraction analysis. Furthermore, a detailed experimental and theoretical study has been performed to understand the effect of substitution of symmetric and non-symmetric functional groups on optical, thermal and electrochemical properties of fluoranthene. These materials exhibit a deep blue emission and high PLQY in solution and solid state. The vacuum deposited, non-doped electroluminescent devices with the device structure ITO/NPD (15 nm)/CBP (15 nm)/EML (40 nm)/TPBI (30 nm)/LiF (1 nm)/Al were fabricated and characterized. A systematic shift in the peak position of EL emission was observed from sky blue to bluish-green with EL maxima from 477 nm to 490 nm due to different functional groups on the periphery of fluoranthene. In addition, a high luminance of >= 2000 cd m(-2) and encouraging external quantum efficiency (EQE) of 1.1-1.4% were achieved. A correlation of the molecular structure with device performance has been established.