Energy transfer analysis and realization of cool to warm white light in Dy3+ /Sm3+ /Er3+ triply doped multicomponent borosilicate glass for white light generation.

A series of Dy3+ /Sm3+ /Er3+ triply doped multicomponent borosilicate glasses (DSE) was synthesized using varying Er3+ ions concentrations through a conventional melt quenching technique. The influence of triple doping on the optical characteristics of the prepared glass was evaluated to estimate the possibility of achieving white light emission through optical absorption, photoluminescence excitation (PLE), and emission (PL) measurements. Based on the PLE and PL spectral profiles, the presence of energy transfer processes between Dy3+ , Sm3+ , and Er3+ was confirmed. Furthermore, for Dy3+ /Sm3+ /Er3+ triply doped glass, an enhancement in Er3+ green luminescence and a noticeable decrease in Dy3+ and Sm3+ emissions were detected with the increase in Er3+ concentration. The nature of energy transfer in DSE glass was investigated through Dexter's energy transfer mechanisms and the obtained result suggested that a dipole-dipole interaction was responsible for the dominant Sm3+ to Dy3+ and Dy3+ to Er3+ energy transfer processes. The precise characteristic colours that emanated from the as-prepared samples were evaluated using Commission Internationale de l'Éclairage co-ordinates and correlated colour temperature values and suggested its suitability for white light emission. The quantum efficiency of the prepared glass was determined experimentally. The aforementioned results recommend that the Dy3+ /Sm3+ /Er3+ triply doped multicomponent borosilicate glass irradiated with ultraviolet light sources might be useful for the generation of cool/warm white light-emitting applications.

Spectroscopic analysis of Eu3+ doped silica-titania-polydimethylsiloxane hybrid ORMOSILs.

Eu3+ doped silica-titania-polydimethylsiloxane hybrid ORMOSILs were synthesized via a non-hydrolytic sol-gel route. The structural and thermal analyses of the samples confirmed that the matrix structure remains unaffected by doping with different concentrations of Eu3+ ions. Photoluminescence (PL) studies performed at 394 nm on Eu3+ doped ORMOSILs imply that they emit broad blue host emission and the characteristic Eu3+ red emissions simultaneously. Also, the samples were excited at the charge transfer (CT) band and this confirmed the existence of an energy transfer path from the host to the Eu3+ ions via Ti4+-O2--Eu3+ bonds. The phonon energy of the host matrix was estimated by phonon sideband (PSB) analysis and the results were substantiated by Raman analysis. Judd-Ofelt (JO) parameters were also evaluated which give details about the local surroundings of the Eu3+ ions in the system and these parameters were further used for predicting the radiative properties of 5D0 → 7F1,2,4 transitions of Eu3+ ions. Furthermore, the quantum efficiency and CIE co-ordinates were evaluated and it was found that Eu3+ doped silica-titania-polydimethylsiloxane ORMOSIL has an intense pinkish red emission with a quantum efficiency of 30.7%.

Structural and spectroscopic investigations on the quenching free luminescence of europium oxalate nanocrystals.

The structural features leading to the intense quenching free luminescence exhibited by europium oxalate nanocrystals, poly[[hexaaquatri-µ2-oxalato-dieuropium] 4.34-hydrate], {[Eu2(C2O4)3(H2O)6]·4.34H2O}n, is the focal point of this report. Europium oxalate nanocrystals were synthesized by a simple microwave-assisted co-precipitation method. Powder X-ray diffraction analysis revealed the monoclinic structure of the nanocrystals and the phase purity. The morphology and particle size were examined by transmission electron microscopy (TEM) analysis. Luminescence measurements on a series of samples of La2-xEux(C2O4)3·10H2O, with x varying in the range 0.1 to 2, established the quenching free nature exhibited by the europium oxalate nanocrystals. A single-crystal structure analysis was carried out and the quenching free luminescence is explained on the basis of the crystal structure. A detailed photoluminescence characterization was carried out using excitation and emission studies, decay analysis, and CIE coordinate and colour purity evaluation. The various spectroscopic parameters were evaluated by Judd-Ofelt theoretical analysis and the results are discussed on the basis of the crystal structure analysis.

Development of Thick Superhydrophilic TiO2-ZrO2 Transparent Coatings Realized through the Inclusion of Poly(methyl methacrylate) and Pluronic-F127.

A thick coating of hierarchically porous double-templated TiO2-ZrO2-PMMA-PF127 with excellent self-cleaning properties and high transmittance has been developed for the first time on glass substrates using a simple dip-coating technique. Comparative studies of this sample with a thick and transparent coating of single-templated TiO2-ZrO2-PMMA have been performed to probe the origin of its exceptional properties. The formation of the composites, successful incorporation of the polymer into the matrix, and the porous nature of the films have been studied. The presence of Ti2+ in the double-templated samples has been confirmed, which suggest the chemisorption of water on the surface of the film. The variation in the self-cleaning properties of the samples on UV-illumination has also been studied. The double-templated film is found to possess the capability of good hydrophilic retention even 2 days after UV-irradiation.

Optical analysis of samarium doped sodium bismuth silicate glass.

Samarium doped sodium bismuth silicate glass was synthesized using the melt quenching method. Detailed optical spectroscopic studies of the glassy material were carried out in the UV-Vis-NIR spectral range. Using the optical absorption spectra Judd-Ofelt (JO) parameters are derived. The calculated values of the JO parameters are utilized in evaluating the various radiative parameters such as electric dipole line strengths (Sed), radiative transition probabilities (Arad), radiative lifetimes (τrad), fluorescence branching ratios (ß) and the integrated absorption cross- sections (σa) for stimulated emission from various excited states of Sm3+‡ ion. The principal fluorescence transitions are identified by recording the fluorescence spectrum. Our analysis revealed that the novel glassy system has the optimum values for the key parameters viz. spectroscopic quality factor, optical gain, stimulated emission cross section and quantum efficiency, which are required for a high performance optical amplifier. Calculated chromaticity co-ordinates (0.61, 0.38) also confirm its application potential in display devices.

NIR emission studies and dielectric properties of Er(3+)-doped multicomponent tellurite glasses.

Multicomponent tellurite glasses containing altered concentrations of Er2O3 (ranging from 0 to 1 mol%) were prepared by the standard melt quenching technique. Investigations through energy dispersive X-ray spectroscopy (EDS), Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy, near-infrared (NIR) emission studies and dielectric measurement techniques were done to probe their compositional, structural, spectroscopic and dielectric characteristics. The broad emission together with the high values of the effective linewidth (~63 nm), stimulated emission cross-section (9.67 × 10(-21) cm(2)) and lifetime (2.56 ms) of (4)I13/2 level for 0.5 mol% of Er(3+) makes these glasses attractive for broadband amplifiers. From the measured capacitance and dissipation factor, the relative permittivity, dielectric loss and the conductivity were computed; which furnish the dielectric nature of the multicomponent tellurite glasses that depend on the applied frequency. Assuming the ideal Debye behavior as substantiated by Cole-Cole plot, an examination of the real and imaginary parts of impedance was performed. The power-law and Cole-Cole parameters were resolved for all the glass samples. From the assessment of the emission analysis and dielectric properties of the glass samples, it was obvious that the Er(3+) ion concentration had played a vital role in tuning the optical and dielectric properties and the 0.5 mol% of Er(3+) -doped glass was confirmed as the optimum composition.

Spectroscopic and photoluminescence characterization of Dy(3+) in Sr0.5Ca0.5TiO3 phosphor.

The spectroscopic and photoluminescence characteristics of trivalent dysprosium (Dy(3+))-doped Sr0.5Ca0.5TiO3 phosphor materials synthesized via solid-state reaction method were studied. The X-ray diffraction profile confirmed the orthorhombic perovskite structure of the prepared samples. Judd-Ofelt analysis was carried out to obtain the intensity parameters and predicted radiative properties of Sr0.5Ca0.5TiO3:2wt%Dy(3+). The photoluminescence spectrum of Dy(3+)-doped Sr0.5Ca0.5TiO3 showed three emission peaks at 481, 574 and 638 nm corresponding to (4)F9/2 →(6)H15/2, (4)F9/2 →(6)H13/2 and (4)F9/2 →(6)H11/2 transitions respectively. The variation of luminescence intensity with different excitation wavelengths and Dy(3+) concentrations is discussed. The decay profiles of (4)F9/2 excited levels of Dy(3+) ions show bi-exponential behaviour and also a decrease in average lifetime with increase in Dy(3+) concentration. Yellow to blue luminescence intensity ratio, CIE chromaticity co-ordinates and correlated color temperature were also calculated for different concentrations of Dy(3+)-doped Sr0.5Ca0.5TiO3 phosphor at different λex.

Synthesis and luminescence characterization of Sr(0.5)Ca(0.5)TiO3:Sm(3+) phosphor.

The spectroscopic properties of trivalent samarium doped Sr0.5Ca0.5TiO3 perovskite phosphor material (Sr0.5Ca0.5TiO3:xSm(3+), x=0.05, 0.1, 0.5, 1, 1.5) synthesized by the solid state method have been studied. The X-Ray Diffraction profile confirms the orthorhombic perovskite Sr0.5Ca0.5TiO3 structure of the prepared samples. The SEM study reveals the surface morphology. The Judd-Ofelt intensity parameters were calculated for 0.5 wt% Sm(3+) doped Sr0.5Ca0.5TiO3. Transition probabilities, branching ratios and radiative lifetime were evaluated by using Judd-Ofelt analysis. The emission spectra under 405 nm excitation shows five emission peaks at 564 nm, 599 nm, 645 nm, 707 nm and 776 nm corresponding to the transitions (4)G5/2→(6)Hj (j=5/2, 7/2, 9/2, 11/2 and 13/2) respectively. The higher values of branching ratio and stimulated emission cross-section for (4)G5/2→(6)H7/2 transition of Sr0.5Ca0.5TiO3:0.5 wt% Sm(3+) shows its suitability in the field of visible lasers and optical fiber amplifiers. The experimental lifetimes of Sm(3+) doped samples were estimated using the decay curves corresponding to (4)G5/2→(6)H7/2 transition upon 405 nm excitation. Concentration dependence on emission intensity and experimental lifetime were also studied. From the CIE diagram we can see that as the concentration of Sm(3+) ions increases from 0.05 wt% to 1.5 wt% the CIE color co-ordinates changes from greenish yellow to yellowish orange.

Structural and spectral investigation of terbium molybdate nanophosphor.

Terbium molybdate nanophosphors were synthesized through a facile sol-gel route. The structure of the phosphors was characterized by X-ray diffraction, Raman spectra and Fourier transform infrared spectroscopy analysis. The X-ray diffraction studies revealed that the structure of the nanophosphor gradually changes from monoclinic to orthorhombic phase as heated from 700 to 900 °C. High resolution transmission electron microscopy, SAED and EDS were also employed to characterize the size, crystallinity and composition of the samples. Detailed spectroscopic investigations were carried out by Judd-Ofelt analysis based on UV-Visible-NIR absorption and emission spectra. The luminescence spectra suggest that phosphors with orthorhombic structure have better luminescence properties than the monoclinic structure. The phosphors showed intense green emission under near-UV excitation due to the energy transfer from the host lattice to Tb(3+) ions. The CIE coordinates suggest enhanced color purity for green emission and short fluorescence decay values proposes the suitability for LED applications. These phosphors can be applied as promising candidates for blue and near-UV excited WLEDs.

Synthesis and luminescence characterization of Pr(3+) doped Sr1.5Ca0.5SiO4 phosphor.

Luminescence properties of Pr(3+) activated Sr1.5Ca0.5SiO4 phosphors synthesized by solid state reaction method are reported in this work. Blue, orange red and red emissions were observed in the Pr(3+) doped sample under 444nm excitation and these emissions are assigned as (3)P0→(3)H4, (3)P0→(3)H6 and (3)P0→(3)F4 transitions. The emission intensity shows a maximum corresponding to the 0.5wt% Pr(3+) ion. The decay analysis was done for 0.05 and 0.5wt% Pr(3+) doped samples for the transition (3)P0→(3)H6. The life times of 0.05 and 0.5wt% Pr(3+) doped samples were calculated by fitting to exponential and non-exponential curve respectively, and are found to be 156 and 105µs respectively. The non-exponential behaviour arises due to the statistical distribution of the distances between the ground state Pr(3+) ions and excited state Pr(3+) ions, which cause the inhomogeneous energy transfer rate. The XRD spectrum confirmed the triclinic phase of the prepared phosphors. The compositions of the samples were determined by the energy dispersive X-ray spectra. From the SEM images it is observed that the particles are agglomerated and are irregularly shaped. IR absorption bands were assigned to different vibrational modes. The well resolved peaks shown in the absorption spectra are identical to the excitation spectra of the phosphor samples. Pr(3+) activated Sr1.5Ca0.5SiO4 phosphors can be efficiently excited with 444nm irradiation and emit multicolour visible emissions. From the CIE diagram it can be seen that the prepared phosphor samples give yellowish-green emission.

Synthesis, structural and spectroscopic investigations of nanostructured samarium oxalate crystals.

Nanostructured samarium oxalate crystals were prepared via microwave assisted co-precipitation method. The crystal structure and morphology of the sample were analyzed using X-ray powder diffraction, Scanning electron microscopy and Transmission electron microscopy. The presence of functional groups is ascertained by Fourier transform infrared spectroscopy. Samarium oxalate nanocrystals of average size 20 nm were aggregated together to form nano-plate structure in sub-microrange. Detailed spectroscopic investigation of the prepared phosphor material was carried out by Judd-Ofelt analysis based on the UV-Visible-NIR absorption spectra and photoluminescence emission spectra. The analysis reveals that the transition from energy level (4)G5/2 to (6)H7/2 of Sm(3+) ion has maximum branching ratio and the corresponding orange emission can be used for display applications.