Local structure and near-infrared emission features of neodymium-based amine functionalized organic/inorganic hybrids

Nd3+-based organic/inorganic hybrids have potential application in the field of integrated optics. Attractive sol-gel derived di-urea and di-urethane cross-linked poly (oxyethylene) (POE)/siloxane hybrids (di-ureasils and di-urethanesils, respectively) doped with neodymium triflate (Nd(CF3SO3)(3)) were examined by Fourier transform mid-infrared (FT-IR), Raman (FT-Raman), Si-29 magic-angle spinning (MAS) nuclear magnetic resonance (NMR) and photoluminescence spectroscopies, and small-angle X-ray scattering (SAXS). The goals of this work were to determine which cation coordinating site of the host matrix (ether oxygen atoms or carbonyl oxygen atoms) is active in each of the materials analyzed, its influence on the nanostructure of the samples and its relation with the photoluminescence properties. The main conclusion derived from this study is that the hydrogen-bonded associations formed throughout the materials play a major role in the hybrids nanostructure and photoluminescence properties.

Room temperature visible/infrared emission and energy transfer in Nd3+-based organic/inorganic hybrids

The photoluminescence features and the energy transfer processes of Nd3+-based siloxanepoly(oxyethylene) hybrids are reported. The host matrix of these materials, classed as di-ureasils, is formed by a siloxane backbone covalently bonded to polyether chains of two molecular weights by means of urea cross-links. The room-temperature photoluminescence spectra of these xerogels show a wide broad purple-blue-green band (350-570 nm), associated with the emitting centres of the di-ureasil host, and the typical near infrared emission of Nd3+ (700-1400 nm), assigned to the 4F3/2 → 4I9/2,11/2,13/2 transitions. Self-absorptions in the visible range, resonant with intra-4f3 transitions, indicate the existence of an energy conversion mechanism of visible di-ureasil emission into near infrared Nd3+ luminescence. The existence of energy transfer between the di-ureasil's emitting centres and the Nd3+ ions is demonstrated calculating the lifetimes of these emitting centres. The efficiency of that energy transfer changes both with the polymer molecular weight and the Nd3+ concentration.

Structure, characterization and near-infrared emission of a novel 6-connected uninodal 3D network of Nd(III) containing 2,5-thiophenedicarboxylate anion

The novel coordination polymer with the formula {[Nd2(2,5-tdc)3(dmf)2(H2O)2].dmf.H2O}n (2,5-tdc2-=2,5-thiophedicarboxylate anion and dmf=dimethylformamide) has been synthesized and characterized by thermal analysis (TG/DTA), vibrational spectroscopy (FTIR) and single crystal X-ray diffraction analysis (XRD). Structure analysis reveals that Nd(III) ions show dicapped trigonal prism coordination geometry. The 2,5-tdc2- ligands connect four Nd(III) centers, adopting (κ1 - κ1) - (κ1 - κ1) - μ4 coordination mode, generating an interesting 6-connected uninodal 3D network. Photophysical properties were studied using diffuse reflectance spectroscopy (DR) and excitation/emission spectra. The photoluminescence data show the near infrared emission (NIR) with the characteristic 4F3/2→4IJ (J=9/2, 11/2 and 13/2) transitions of Nd(III) ion, indicating that 2,5-tdc2- is able to act as a sensitizer for emission in NIR region. © 2013 Elsevier B.V.

Efficient energy upconversion emission in Tm3+/Yb3+-codoped TeO2-based optical glasses excited at 1.064 mu m

Efficient energy upconversion of cw radiation at 1.064 mum into blue, red, and near infrared emission in Tm3+-doped Yb3+-sensitized 60TeO(2)-10GeO(2)-10K(2)O-10Li(2)O-10Nb(2)O(5) glasses is reported. Intense blue upconversion luminescence at 485 nm corresponding to the Tm3+ (1)G(4)--> H-3(6) transition with a measured absolute power of 0.1 muW for 800 mW excitation power at room temperature is observed. The experimental results also revealed a sevenfold enhancement in the upconversion efficiency when the sample was heated from room temperature to 235 degreesC yielding 0.7 muW of blue absolute fluorescence power for 800 mW pump power. High brightness emission around 800 nm (F-3(4)--> H-3(6)) in addition to a less intense 655 nm ((1)G(4)--> H-3(4) and F-3(2,3)--> H-3(6)) fluorescence is also recorded. The energy upconversion excitation mechanism for thulium emitting levels is assigned to multiphonon-assisted anti-Stokes excitation of the ytterbium-sensitizer followed by multiphonon-assisted sequential energy-transfer processes. (C) 2001 American Institute of Physics.

1.5 mu m and visible up-conversion emissions in Er3+/Yb3+ co-doped tellurite glasses and optical fibers for photonic applications

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Local Er(III) environment in luminescent titanosilicates prepared from microporous precursors

The local environment of Er3+ ions in microporous titanosilicate ETS-10 and in synthetic narsarsukite and glassy materials obtained by calcination of ETS-10 has been investigated by EXAFS, Raman and photoluminescence spectroscopies. Er L-III-edge EXAFS studies of Er3+-doped ETS-10 support the view that the exchanged Er3+ ions reside close to the (negatively charged) TiO6 octahedra. In ETS-10, Er3+ is partially bonded to framework oxygen atoms and hydration water molecules. The Er...Ti distance (3.3 Angstrom) is similar to the Na...Ti distances (3.15-3.20 Angstrom) reported previously for Na-ETS-10. Although the exact location of the ErO6 units within the host structure of Er3+-doped synthetic narsarsukite is still an open question, it is most likely that Er3+ substitutes Ti4+ rather than Na+ ions. EXAFS spectroscopy indicates that no significant clustering of erbium atoms occurs in the titanosilicate samples studied. Evidence for the insertion of Er3+ ions in the framework of narsarsukite has been obtained by Raman spectroscopy. This is indicated by the increasing full-width at half-maximum (FWHM) of the 775 cm(-1) peak and the increasing intensity of the anatase peaks as the erbium content increases. In addition, as the narsarsukite Er3+ content increases a band at ca. 515 cm(-1) firstly broadens and subsequently a new peak appears at ca. 507 cm(-1).Er3+-doped narsarsukite exhibits a characteristic local vibrational frequency, (h) over bar omega ca. 330 cm(-1), with an electron-phonon coupling, g ca. 0.2, which constitutes additional evidence for framework Er3+ insertion. The number of lines in the infrared emission spectrum of synthetic narsarsukite indicates the presence of two optically-active erbium centres with very similar local environments and an average I-4(13/2) lifetime of 7.8 +/- 0.2 ms.

New glasses in the system InF3-BaF2-ErPO4

New glasses have been obtained in the system InF3-BaF2-ErPO4. Glass compositions with up to 30% mol Er3+ were shown to exist and characterized by thermal analysis, x-ray: diffraction, IR absorption and electronic spectroscopy. The systems with high Er3+ content were studied recording IR and visible emission spectral characteristics. A specially elaborated technique allowed the preparation of a high purity phosphate precursor ErPO4. X-ray identification of the crystalline phases appearing during thermal treatment have been carried out and parameters of a mixed fluoride Ba4In3-nErnF17 calculated.

Avaliação óptica de vidros teluritos preparados com Er3+ e Er3+/Yb3+ para aplicação em fotônica

Pós-graduação em Ciência dos Materiais - FEIS

Vidros a base de óxido de telúrio para dispositivos fotônicos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of Ag nanoparticles on the radiative properties of tellurite glasses doped with Er3+, Yb3+ and Tm3+ ions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Intense red upconversion emission in infrared excited holmium-doped PbGeO3-PbF2-CdF2 transparent glass ceramic

Intense red upconversion emission around 650 nm in PbGeO3-PbF2-CdF2 transparent glass ceramic containing beta-PbF2:Ho3+ nanocrystals, is presented. The holmium-doped vitroceramic samples were excited by a 980 nm diode laser source. The 650 nm upconversion signal was assigned to the F-5(5) --> I-5(8) transition of holmium ions. Very low intensity signals around 490 and 540 nm corresponding to the F-5(2,3) --> I-5(8) and S-4(2), F-5(4) --> I-5(8) transitions, respectively, were also detected. The upconversion excitation mechanism was achieved through a combination of stepwise phonon-assisted multiphoton absorption, cross-relaxation processes involving pairs of holmium ions, and excited-state absorption. Using a diode laser pump source around 850 nm green upconversion emission around 540 nm was the observed predominant signal. (C) 2004 Elsevier B.V. All rights reserved.

1.5 mu m emission and infrared-to-visible frequency upconversion in Er+3/Yb+3-doped phosphoniobate glasses

Sodium phosphoniobate glasses with the composition (mol%) 75NaPO(3)-25Nb(2)O(5) and containing 2 mol% Yb3+ and x mol% Er3+ (0.01 <= x <= 2) were prepared using the conventional melting/casting process. Er3+ emission at 1.5 mu m and infrared-to-visible upconversion emission, upon excitation at 976 nm, are evaluated as a function of the Er3+ concentration. For the lowest Er3+ content, 1.5 mu m emission quantum efficiency was 90%. Increasing the Er3+ concentration up to 2 mol%, the emission quantum efficiency was observed to decrease to 37% due to concentration quenching. The green and red upconversion emission intensity ratio was studied as a function of Yb3+ co-doping and the Er3+-Er3+ energy transfer processes. (c) 2006 Elsevier B.V. All rights reserved.

Infrared to visible up-conversion emission in Er3+/Yb 3+ codoped fluoro-phosphate glass-ceramics

Erbium Er3+ and ytterbium Yb3+ codoped fluoro-phosphate glasses belonging to the system NaPO3-YF 3-BaF2-CaF2 have been prepared by the classical melt-quenching technique. Glasses containing up to 10 wt% of erbium and ytterbium fluorides have been obtained and characterized using differential scanning calorimetry (DSC) and UV-visible and near-infrared spectroscopy. Transparent and homogeneous glass-ceramics have been then reproducibly synthetized by appropriate heat treatment above glass transition temperature of a selected parent glass. Structural investigations of the crystallization performed through X-ray diffractometry (XRD) and scanning electron microscopy (SEM) have evidenced the formation of fluorite-type cubic crystals based during the devitrification process. Finally, infrared to visible up-conversion emission upon excitation at 975 nm has been studied on the Er3+ and Yb 3+ codoped glass-ceramics as a function of thermal treatment time. A large enhancement of intensity of the up-conversion emissions-about 150 times- has been observed in the glass-ceramics if compared to the parent glass one, suggesting an incorporation of the rare-earth ions (REI) into the crystalline phase. © 2012 The American Ceramic Society.

Infrared to visible up-conversion in biocellulose yttrium vanadate nanoparticle composite membranes. Demonstration of chloroaluminum phthalocyanine light emission under up-converted light excitation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

New far-infrared laser lines from CH3OD methanol deuterated isotope

We report on a study of the CH3OD molecule in a search for new far-infrared (FIR) laser lines. For optical pumping of large offset vibrational absorption transitions, a continuous-wave waveguide CO2 laser with 300 MHz tunability around each line was used for the first time. As a consequence, 17. new far-infrared laser emissions were observed. For these lines, we also present data on wavelength, intensity, offset, relative polarization, and optimum operation pressure.