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Made available in DSpace on 2022-04-28T17:20:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-07-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) CeRTEV Tellurite glasses are considered a potential alternative for applications not achieved by SiO2-based glasses, presenting interesting optical properties, such as high linear and nonlinear refractive indexes, extended optical window, being also suitable for metallic nanoparticle growth, like Te-0. When doped with sulfide species, it can benefit the reduction of Te4+ to Te-0, which can be advantageous to synthesize in-situ chalcogenide nanoparticles and quantum dots. This work presents investigations on the reduction of Te4+ to Te-0 in tellurite glasses doped with PbS and PbO/ZnS, and aims to control this redox process through the processing with pulsed fs-laser. Tellurite glass samples were synthesized by melt-quenching technique and the thermal and structural properties were explored by different techniques, such as DSC, Raman scattering spectroscopy and mapping experiment, TEM and SAED. Reduction of tellurium to Te-0 nanocrystals into tellurite glass after laser irradiation was studied in detail and confirmed by the presence of bands at similar to 120 and 140 cm(-1) in Raman spectroscopy and mapping, assigned to the Te-Te vibrational modes, which suggest that S2- induces in-situ Te4+ reduction. Moreover, quasi spherical tellurium nanoparticles were observed through TEM and confirmed their chemical nature and crystallization by SAED. The study of tellurium reduction in the vitreous matrix becomes particularly important and promising for some applications, since its reduction generates changes in the refractive index by precipitation of Te-0 nanoparticles, allowing the fabrication of waveguides and as photosensitive material for tridimensional data storage. (C) 2021 Published by Elsevier B.V. Univ Sao Paulo, Sao Carlos Inst Chem IQSC, Sao Carlos, SP, Brazil Univ Sao Paulo, Sao Carlos Inst Phys IFSC, Sao Carlos, SP, Brazil Univ Sao Paulo, Sao Carlos Sch Engn EESC, Sao Carlos, SP, Brazil Sao Paulo State Univ, Inst Chem, Araraquara, SP, Brazil Univ Fed Alfenas, Grp Quim Mat, Pocos De Caldas, MG, Brazil Sao Paulo State Univ, Inst Chem, Araraquara, SP, Brazil FAPESP: 2018/164076 FAPESP: 2018/11283-7 FAPESP: 2018/16126-7 CeRTEV: 2013/077936

New glass compositions containing high concentrations of Tb3+ ions were developed aiming at the production of magneto-optical (MO) fibers. This work reports on the structural and MO properties of a new glass composition based on (100 − x)(41GeO2–25B2O3–4Al2O3–10Na2O–20BaO) − xTb4O7. Morphological analysis (HR-TEM) of the sample with the highest concentration of Tb3+ ions confirmed the homogeneous distribution of Tb3+ ions and the absence of nanoclusters. All the samples presented excellent thermal stability against crystallization (ΔT > 100 °C). An optical fiber was manufactured by a fiber drawing process. The UV–Vis spectra of the glasses showed Tb3+ electronic transitions and optical windows varying from 0.4 to 1.6 μm. The magneto-optical properties and the paramagnetic behaviors of the glasses were investigated using Faraday rotation experiments. The Verdet constant (VB) values were calculated at 500, 650, 880, 1050, 1330, and 1550 nm. The maximum VB values obtained at 650 and 1550 nm for the glass with x = 18 mol% were -128 and − 17.6 rad T−1 m−1, respectively. The VB values at 500 and 1550 nm for the optical fiber containing 8 mol% of Tb4O7 were − 110.2 and − 9.5 rad T−1 m−1, respectively, while the optical loss at around 880 nm was 6.4 dB m−1.

Knowledge of relaxation processes is fundamental in glass science and technology because relaxation is intrinsically related to vitrification, tempering as well as to annealing and sev-eral applications of glasses. However, there are conflicting reports -- summarized here for different glasses -- on whether the structural relaxation time of glass can be calculated using the Maxwell equation, which relates relaxation time with shear viscosity and shear modulus. Hence, this study aimed to verify whether these two relaxation times are comparable. The structural relaxation kinetics of a lead metasilicate glass were studied by measuring the re-fractive index variation over time at temperatures between 5 and 25 K below the fictive temperature, which was initially set 5 K below the glass transition temperature. Equilibrium shear viscosity was measured above and below the glass transition range, expanding the current knowledge by one order of magnitude. The Kohlrausch equation described very well the experimental structural relaxation kinetics throughout the investigated temperature range and the Kohlrausch exponent increased with temperature, in agreement with studies on other glasses. The experimental average structural relaxation times were much longer than the values computed from isostructural viscosity, as expected. Still, they were less than one order of magnitude higher than the average relaxation time computed through the Maxwell equation, which relies on equilibrium shear viscosity. Thus, these results demon-strate that the structural relaxation process is not controlled by isostructural viscosity, and that equilibrium shear viscosity only provides a lower boundary for structural relaxation kinetics., 19 pages, 8 figures. Changed title. Minor updates to the text

Glass is a familiar material that requires abundant mineral sources, with devastating consequences for the environment. Rice husk ash (RHA) presents a very high silica content (&gt, 95%) and it can be a very promising alternative source for silica in silica-based glass. However, impurities like manganese and iron, which depend on the rice harvest, might limit RHA use, particularly in the production of optical transparent glasses. In this work, we discussed how Mn and Fe can affect the coloring of the produced glass, and how the effect of these impurities can be removed. First, the RHA was treated with acid solutions, leading to the production of a soda-lime glass with similar transparency to commercial glass (&gt, 70%). Secondly, another simpler approach was studied: a small amount of antimony oxide was added in the composition of the glass, obtaining a transparent glass (&gt, 80%, same thickness) with RHA.

Made available in DSpace on 2020-12-12T01:15:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-06-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The challenge to obtain stable glasses containing monodisperse magnetic nanoparticles with controlled size and shape is an exciting and almost unexplored field of research. Such new materials can be used in magneto-photonics or ultra-sensitive magnetic sensors. In this work, for the first time, colorless and transparent bulk glasses containing monodisperse 20 nm Fe3−δO4 nanoparticles were prepared by a melt-quenching route. Magnetic nanoparticles were synthesized by thermal decomposition and covered with a stellate mesoporous silica shell in order to protect them against dissolution during the glass melting process. The incorporation of nanoparticles into glasses and the ideal parameters obtained for this system are discussed. The new nanocomposite materials were characterized in order to investigate the structure, thermal, and magnetic properties. Such an original approach is a very promising way to incorporate a wide panel of nanoparticles, including metallic, bimetallic and metal oxide nanoparticles, into a variety of glasses providing new properties to these materials. São Paulo State University - UNESP Institute of Chemistry, P. O. Box 355 Université de Strasbourg CNRS Institut de Physique et Chimie des Matériaux de Strasbourg UMR 7504 São Paulo State University - UNESP Institute of Chemistry, P. O. Box 355 CNPq: 153762/2018-7 FAPESP: 2013/07793-6 FAPESP: 2018/07727-7 FAPESP: 2019/19609-1 CAPES: 88881.134870/2016-01

Made available in DSpace on 2020-12-12T01:24:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-08-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A set of glass samples with composition based on ternary 50P2O5–30Na2O–20ZnO (PNZ) matrix doped with different MnO contents was prepared via melt-quenching technique. Thermal, structural and spectroscopic properties were investigated by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), Raman spectroscopy, UV–visible absorption, photoluminescence (PL) and by electron paramagnetic resonance (EPR) using Mn2+ as probe. Glass compositions (100-x)PNZ:xMn (0.01 ≤ x ≤ 1.0 in mol% of MnO) were characterized as glasses after careful analysis of the thermal and structural data. While DSC curves show the presence of the glass transition phenomenon (Tg), XRD analysis identified the non-crystalline arrangement, compatible with glass structure. Raman spectra of PNZ:xMn samples showed that the successive increase in Mn2+ content leads to rise of vibrational modes assigned to phosphate Q1 units, suggesting the breakdown of phosphate glass network chains. UV–Vis absorption spectra of glasses presented absorption bands centered at 250, 318, 341, 358 and 408 nm attributed to the Mn2+ electronic transitions. Glass samples containing above 0.06 mol% of MnO presented a broadband absorption centered at 511 nm assigned to the presence of traces of Mn3+. Additionally, UV–Vis, PL and EPR data showed that Mn2+ ions are occupying octahedral arrangements. Besides, EPR results suggest that the increase in MnO concentration influences on the EPR signal and hyperfine splitting constant suggests the presence of a moderately ionic bond between Mn2+ and PNZ glass network. Instituto de Química de Araraquara Universidade Estadual Paulista UNESP, P.O. Box 355 Instituto de Química de São Carlos Universidade de São Paulo IQSC–USP, P.O. Box 780 Departamento de Física Universidade Federal de São Carlos, Rod. Washington Luis Km. 235 Instituto de Física de São Carlos Universidade de São Paulo IFSC-USP, P.O. Box 369 Instituto de Química de Araraquara Universidade Estadual Paulista UNESP, P.O. Box 355 FAPESP: 2016/16900-9 FAPESP: CERTEV-2013/07793-6

The coacervation process of Graham’s Salt Na(PO3)n enabled the preparation of polyphosphate coacervates (CPPs) by adding different metallic ions (Mn+), and/or low-molecular-weight solvents at a specific solution, which resulted in a phase separation. The more viscous phase is termed as CPP and the less viscous one is the supernatant. CPPs have been extensively studied in recent years as a glass precursor at room temperature. Preparation at room temperature allows the preservation of the physicochemical properties of a wide range of active principles that may be used in controlled drug-delivery systems. Despite the present limitations of CPPs in terms of high hygroscopicity, this vulnerability to water is considered one of the great advantages of this material regarding applications in the controlled release of drugs and tissue engineering. Thus, in the presence of water, CPPs will dissolve in calcium and phosphate ions, which are the major inorganic constituents of bone and hydroxyapatite (HAP). It is believed that, in contact with body fluids, CPPs will degrade and, as this process occurs, they will be replaced by HAP. Therefore, CPPs configure a potential biomaterial that offers excellent properties with a wide range of biomedical applications that will be discussed and reviewed in this paper, including the structural properties and the recent improvements of materials based on CPPs and related devices.

Made available in DSpace on 2022-04-28T19:41:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Horizon 2020 Framework Programme Agence Nationale de la Recherche Glass forming regions in the system GaO3/2 – GeO2 – LaO3/2 – BaO have been explored using aerodynamic levitation coupled to laser heating synthesis technique. Structure property relationships have been established between the thermal and optical properties of the resulting glass thanks to Raman and Infrared vibrational spectroscopies. The germano-gallate glass networks are mainly made of three-dimensional interconnected corner shared GeO4 and GaO4 tetrahedra forming Ge – O – Ge and Ga – O− – Ge bridges in which gallium tetrahedral GaO4 units are charged-compensated by barium and lanthanum cations. In GeO2-rich compositions, the excess of positive charges produces mainly non-bridging oxygens on germanate moieties, leading to a depolymerization of the glass network. In the case of gallium rich compositions, the infrared cut-off is red-shifted as compared to the germanate glasses, in accordance with the disappearance of germanium associated entities such as germanium and gallium bridges or germanium sites with non-bridging oxygen both vibrating at higher wavenumber. Institut de Chimie de la Matière Condensée de Bordeaux Université de Bordeaux, 87 Avenue du Dr Schweitzer Conditions Extrêmes et Matériaux Haute Température et Irradiation UPR3079 Université d'Orléans 1 Avenue de la Recherche Scientifique Institut des Sciences Moléculaires UMR 5255 Université́ de Bordeaux 351 cours de la Libération Institute of Chemistry São Paulo State University-UNESP Rua Prof. Francisco Degni, 55, CEP 14800-060 Institute of Chemistry São Paulo State University-UNESP Rua Prof. Francisco Degni, 55, CEP 14800-060 FAPESP: 2013/07793-6 FAPESP: 2019/01223-0 Horizon 2020 Framework Programme: 823941 Agence Nationale de la Recherche: ANR-10-IDEX-03-02 Agence Nationale de la Recherche: ANR-18-CE08-0004-02

Made available in DSpace on 2019-10-06T15:19:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-15 In this work, glass compositions in the system NaPO3 - Sb2O3 – CuO (PSbCu) containing different concentrations of CuO and Sb2O3 were prepared through the melt - quenching methodology. Thermal, structural and optical properties of the PSbCu glasses were systematically studied by differential scanning calorimetry (DSC), X – ray powder diffraction (XRD) and Raman, UV–Visible and Photoluminescence (PL) spectroscopies, besides electron paramagnetic resonance (EPR) measurements. The DSC curves for all samples presented the glass transition phenomenon (Tg), while the XRD patterns showed the presence of an amorphous halo, which confirmed the glassy nature of all samples analyzed. UV–Vis spectra of the glasses showed a transparent window from 450 to 800 nm. The EPR signals intensities were investigated as a function of the copper concentration and Sb2O3 content in the (PySb0.5Cu) (20 ≤ y ≤ 80) and (PSb80xCu) (0.25 ≤ x ≤ 1.25) glasses. The EPR results showed that the increase of Sb2O3 concentration on the PySb0.5Cu glasses decreased the Cu2+ signals, which suggests the Sb3+ oxidizing to Sb5+, also transferring electrons to Cu2+ species to create the EPR a silent Cu+ specie. According to EPR parameters and PL spectra (excited at 380 nm) of PySb0.5Cu glasses, the ions Cu2+ ions were preferentially found in a distorted octahedral geometry, while Cu+ is in a square planar geometry according to the Jahn-Teller effect. Instituto de Química da Araraquara Universidade Estadual Paulista — UNESP, P. O. Box 355 Departamento de Química Instituto de Ciências Exatas Universidade Federal de Juiz de Fora Instituto de Física de São Carlos Universidade de São Paulo Departamento de Física Universidade Federal de São Carlos Instituto de Química da Araraquara Universidade Estadual Paulista — UNESP, P. O. Box 355

Made available in DSpace on 2021-06-25T11:03:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-13 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Instituto Nacional de Fotônica Bacterial nanocellulose (BNC) is a natural biopolymer obtained by gram-negative bacteria by means of a green and inexhaustible biotechnological process using glucose as producing source. BCN hydrogels is formed by cellulose nanofibrils that maintain an open network structure, an ideal matrix to produce new class of organic-inorganic nanocomposites (OIN) for multifunctional applications. The polyoxometalates (POMs) are complex molecules with several metallic ions sharing oxide ions, forming a highly symmetrical metal oxide cluster. Phosphotungstic acid (PWA), H3PW12O40 photoreduction process activated under ultraviolet irradiation, promoting color change. In this work, photochromic organic-inorganic nanocomposites were prepared by soaking phosphotungstic acid (H3PW12O40) in wet BNC membranes mats at room temperature. Semi-transparent and free-standing BNC/PWA nanocomposite with paper-like aspect were obtained. BNC network was able to control, stabilize and disperse PWA particles in a narrow nanometric distribution, and FTIR spectra indicated that the primary Keggin structure was also preserved in the nanocomposites, independently on the PWA content. The nanoparticles present a narrow distribution of around 16 nm, independently on the PWA concentration. BNC/PWA nanocomposites showed reversible photochromic behavior characteristic of the equilibrium between different tungsten oxidation states. PWA reduction (W6+→ W5+) and organic matrix oxidation is proposed to occur through a radical process involving the interaction of one electron from the oxygen atom of the PWA and one hydrogen from BNC matrix. The photochromic effect vanishes almost completely after 5 h. This mechanism is real in the presence of oxygen, however, if the membranes are left in nitrogen or under vacuum the blue color remains longer than 45 days. Photo-electrochemical behavior was studied by spectroelectrochemistry measurements. It is worth noting that all processes were still reversible in the timescale of the experiment and color changes were observed in several cycles. Institute of Chemistry São Paulo State University (UNESP) Laboratório de Biopolímeros e Biomateriais (BioPolMat) Universidade de Araraquara Instituto de Química – Universidade de São Paulo USP Departamento de Física Instituto de Ciências Exatas Universidade Federal de Juiz de Fora (UFJF) Deparment of Chemistry Federal University of São Departamento de Física Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio) Institute of Chemistry São Paulo State University (UNESP) FAPESP: 2013/07793-6 FAPESP: 2013/24725-4 FAPESP: 2014/12424-2 FAPESP: 2016/11591-8 FAPESP: 2018/25512-8 FAPESP: 2020/04509-9 Instituto Nacional de Fotônica: 407822/2018-6

Made available in DSpace on 2021-06-25T11:13:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-01 New magnetic glass compositions, based on system (100-x) (60GeO2 -25B2O3 -4Al2O3 -10Na2O-1PbO) - xTb4O7 were prepared by the melt-quenching technique. The materials were systematically characterized with respect to their structural (XRD, EXAFS, XANES and Raman), thermal (DSC), morphological, optical, magnetic and magneto-optical (MO) properties. Morphological and magnetic measurements show the homogeneous distribution of the Tb3+ ions as the magnetic susceptibility increases proportionally to the rare earth content. The optical window covers the range from 0.5 up to 1.6 μm, limited by absorption due to 4f8 -> 4f7 5 d 1and 4f8 -> 4f8 transitions of Tb3+. XANES and EXAFS measurements at the Ge-K edge show that the germanium atoms are always tetrahedrally coordinated, while results at the Tb-LIII edge shows terbium atoms to be eight-coordinated and exclusively present in the oxidation state 3+ independently of the glass composition. MO measurements show that the Verdet constant (VB) increases linearly with the Tb3+ concentration reaching the value of -83.9 rad T-1m-1 at 650 nm for glass containing 8 mol% of Tb4O7. Good thermal stability (ΔT = 200 °C) allowed obtaining an optical fiber of a glass containing 4 mol% of Tb4O7 featuring VB values of -37.9, -23.6 and -5.89 rad T-1 m-1, at 500, 650 and 1550 nm, respectively. Institute of Chemistry São Paulo State University UNESP Institute of Physics Applied Physics Center University of Brasília São Carlos Institute of Physics São Paulo University USP Department of Materials Engineering (DEMa) Federal University of São Carlos UFSCar Centre d'Optique Photonique et Laser Université Laval Institute of Chemistry São Paulo State University UNESP

New glass compositions containing high concentrations of Tb3+ ions were developed aiming at the production of magneto-optical (MO) fibers. This work reports on the structural and MO properties of a new glass composition based on (100-x)(41GeO2-25B2O3-4Al2O3-10Na2O-20BaO) – xTb4O7. Morphological analysis (HR-TEM) of the sample with the highest concentration of Tb3+ ions confirmed the homogeneous distribution of Tb3+ ions and the absence of nanoclusters. All the samples presented excellent thermal stability against crystallization (ΔT > 100 oC). An optical fiber was manufactured by a fiber drawing process. The UV-Vis spectra of the glasses showed Tb3+ electronic transitions and optical windows varying from 0.4 to 1.6 µm. The magneto-optical properties and the paramagnetic behaviors of the glasses were investigated using Faraday rotation experiments. The Verdet constant (VB) values were calculated at 500, 650, 880, 1050, 1330, and 1550 nm. The maximum VB values obtained at 650 and 1550 nm for the glass with x = 18 mol% were − 128 and − 17.6 rad T− 1 m− 1, respectively. The VB values at 500 and 1550 nm for the optical fiber containing 8 mol% of Tb4O7 were − 110.2 and − 9.5 rad T− 1 m− 1, respectively, while the optical loss at around 880 nm was 6.4 dB m− 1.

New glass compositions containing high concentrations of Tb3+ ions were developed aiming at the production of magneto-optical (MO) fibers. This work reports on the structural and MO properties of a new glass composition based on (100 − x)(41GeO2–25B2O3–4Al2O3–10Na2O–20BaO) − xTb4O7. Morphological analysis (HR-TEM) of the sample with the highest concentration of Tb3+ ions confirmed the homogeneous distribution of Tb3+ ions and the absence of nanoclusters. All the samples presented excellent thermal stability against crystallization (ΔT > 100 °C). An optical fiber was manufactured by a fiber drawing process. The UV–Vis spectra of the glasses showed Tb3+ electronic transitions and optical windows varying from 0.4 to 1.6 μm. The magneto-optical properties and the paramagnetic behaviors of the glasses were investigated using Faraday rotation experiments. The Verdet constant (VB) values were calculated at 500, 650, 880, 1050, 1330, and 1550 nm. The maximum VB values obtained at 650 and 1550 nm for the glass with x = 18 mol% were -128 and − 17.6 rad T−1 m−1, respectively. The VB values at 500 and 1550 nm for the optical fiber containing 8 mol% of Tb4O7 were − 110.2 and − 9.5 rad T−1 m−1, respectively, while the optical loss at around 880 nm was 6.4 dB m−1.

Made available in DSpace on 2022-04-28T19:40:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-01 Ho3+-doped YNbO4 and Y3NbO7 phosphors were synthesised via a co-precipitation synthesis route. Structural characterisation and spectroscopic properties were performed as a function of the Ho3+ concentration. The Rietveld type-refinement confirms the stabilisation of the pure monoclinic Fergusonite YNbO4 phase at the highest temperatures, but the quadratic phase is stabilised for the lowest temperature, whereas a pure cubic fluorite Y3NbO7 phase was observed for all of the heat treatments. Raman and infrared spectroscopies were used to compare the cation-oxygen vibrational modes. Emission spectra and up-conversion processes were obtained under excitation at 445 and 975 nm respectively. For a similar Ho3+ content, the energy transfers observed show differences between the two crystalline compounds that are related to a stronger interaction between the holmium cations in the fluorite host lattice. CNRS Univ. Bordeaux, Bordeaux INP, ICMCB, UMR 5026 ISM - Institute of Molecular Science UMR 5255 CNRS-University of Bordeaux Université de Bordeaux CNRS Laboratoire des Composites ThermoStructuraux, UMR 5801 Chemistry Institute São Paulo State University – UNESP Chemistry Institute São Paulo State University – UNESP

Made available in DSpace on 2020-12-12T02:47:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-12-25 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Glasses are materials with highly flexible compositions and high chemical and physical durability. These characteristics make them suitable materials for hosting nanoparticles for different purposes. Hybrid glasses containing magnetic nanoparticles have been highlighted due to their potential for application as ultra-sensitive magnetic sensors and magnetic devices. In this work, phosphate bulk glasses containing 0.5%, 1.0%, and 2.0% in mass of metallic CoPt alloy nanoparticles were prepared by melt-quenching technique. The CoPt nanoparticles were synthesized by reducing metal precursors in a high temperature organic solvent and, in the second step, they were covered with a silica layer in order to protect the nanoparticles for the subsequent melting. The nanoparticles were treated at different temperatures. Heat treatment at 900 °C showed the highest values of saturation magnetization and coercivity, and for that reason these nanoparticles were chosen for incorporation into glass. In the transmission electron microscopy images of the glass containing 2.0% in mass of nanoparticles, the interplanar distance of 0.21 nm was identified and indexed to the 111 plane of CoPt, confirming that the nanoparticles were successfully embedded into the matrix. The UV–Vis spectra presented Co2+ characteristic bands at 528, 578, and 626 nm, indicating that these ions are tetrahedrally coordinated in the matrix. Themagnetic measurements presented behavior close to ferromagnetic, showing that it is possible to prepare a magnetic glass containing bimetallic nanoparticles. Institute of Chemistry - São Paulo State University - UNESP, P. O. Box 355 Federal University of Sao Carlos (UFSCar) Graduate Program in Materials Science and Engineering Department of Materials Engineering Instituto de Física Núcleo de Física Aplicada Universidade de Brasília Instituto Federal Goiano Institute of Chemistry - São Paulo State University - UNESP, P. O. Box 355 CAPES: 001 FAPESP: 2013/07793-6 FAPESP: 2018/07727-7 FAPESP: 2019/19609-1 CAPES: 88882.332718/2019-01

Made available in DSpace on 2020-12-12T01:28:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-25 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) Financiadora de Estudos e Projetos Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Transparent Eu3+-doped tantalum phosphate glass-ceramics containing Na2Ta8O21 nanocrystals were successfully obtained by a two-step heat treatment. Structural analyses were performed using X-ray diffraction, Transmission Electron Microscopy, Nuclear Magnetic Resonance and Raman spectroscopy. Due to the high Ta/P ratio (= 2) the glass network is built from a mixed 3D PO4–TaO6 chain in which TaO6-rich regions are inserted and responsible for crystallization of an alkali tantalum oxide phase Na2Ta8O21. Eu3+ and their optical properties was used as a sensitive probe to study it site structure in the host matrix. The radiative properties of Eu3+ emission levels were predicted using the Judd-Ofelt theory. The chemical environment and local phonon energy around the rare-earth ions have been proposed based on phonon side band associated with the 7F0 → 5D2 transition, 5D0 → 7F2/7F1 relative intensity and narrowing of the emission bands. High tantalum content precursor glass exhibits high photoluminescence quantum efficiency due to low phonon energy and high refractive index (1.9461 at 633 nm). A perovskite-like bronze crystalline structure is formed in the glass-ceramic (nucleated at 925 °C for 0.5 h and grown at 940 °C for different times) and is considered promising for nonlinear optical applications and studies. Institute of Chemistry Sao Paulo State University - UNESP Sao Carlos Institute of Chemistry University of Sao Paulo, São Carlos Grupo de Química de Materiais Universidade Federal de Alfenas Campus Poços de Caldas, Poços de Caldas Institute of Chemistry Sao Paulo State University - UNESP CNPq: 156420/2018-0 FAPESP: 2013/07793-6 FAPESP: 2018/16126-7

Made available in DSpace on 2021-06-25T10:15:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-05 Glasses in the system (85-x)GeO2-(x)B2O3-10Na2O-4Al2O3-1PbO, which are used as matrices for rare-earth ion containing magneto-optic glasses have been prepared and their thermal and structural properties have been characterized by differential scanning calorimetry, Raman scattering, and solid state NMR spectroscopies. Besides showing the features of the corresponding borogermanate binary glasses, the Raman spectra also reveal new features consistent with the occurrence of B-O-Ge connectivities. One- and two-dimensional 23Na, 27Al, and 11B NMR spectra reveal monotonic structural changes as a function of composition, reflecting the competition of the three network former species for charge compensation by the network modifier cations. Aluminum is found in a predominantly four-coordinated environment. Its anionic functionalization and, with second priority, that of the boron oxide component take precedence over that of the germanium oxide component. The glass transition temperature decreases with increasing B2O3 content and shows an excellent correlation with the average network connectivity deduced from the NMR data. Institute of Chemistry São Paulo State University-UNESP, R. Prof. Francisco Degni, 55 São Carlos Institute of Physics São Paulo University - USP, Av. Trabalhador Sãocarlense 400 Institut für Physikalische Chemie Westfälische Wilhelms-Universität, Corrensstraße 28-30 Institute of Chemistry São Paulo State University-UNESP, R. Prof. Francisco Degni, 55

Made available in DSpace on 2020-12-12T02:36:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Herein we report the synthesis of highly-doped silver nanocluster in fluorophosphate glasses through the melting-quenching method in order to achieve sensitization with Tm3+ and Mn2+ ions. Blue and red emission belonging to Tm3+ (470 to 490 nm) and Mn2+ (550 to 750 nm) ions could be obtained via non-resonant excitation of Tm3+ and Mn2+. Slight decrease of the fluorescence decay times confirmed an energy transfer as a possible mechanism to explain the Tm3+ and Mn2+ emission. The composition of 5 mol% of AgNO3, 0.4 mol% of Tm2O3 and 0.2 mol% of MnF2 in our sample leads to distance between donor (silver nanoclusters) and acceptor (Tm3+-Mn2+) as short as 11 Å, which suggests that the main mechanism for blue and red emission from Tm3+ and Mn2+ is Förster Resonance Energy Transfer (FRET). The results presented here show that the studied material has potential application for multicolor generation as luminophore in white light emitting diodes (W-LED). Institute of Chemistry - São Paulo State University - UNESP Department of Chemical Physics and Optics Faculty of Mathematics and Physics Charles University, Ke Karlovu 3 Department of Chemistry and Chemical Engineering Chalmers University of Technology Institute of Chemistry - São Paulo State University - UNESP FAPESP: #2013/07793-6 FAPESP: #2016/16343-2 FAPESP: #2016/16900-9

Made available in DSpace on 2020-12-12T01:30:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) ASCRS Research Foundation Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A series of new transparent and magnetic germanoborate glasses in the system (100-x)[60GeO2–25B2O3–10Na2O–4Al2O3–1PbO] – (x) Gd2O3, with x = 0, 1, 2, 5, 10, 15 and 20 mol%, was prepared and studied with respect to their thermal and structural changes in the presence of Gd2O3. Based on Differential Scanning Calorimetre (DSC) analysis, a glass with 5% of Gd2O3 showed a high thermal stability, which progressively decreases for samples with higher content of Gd2O3. By the analysis of Raman and Fourier Transform Infrared (FTIR) spectra, it was possible to identify that by increasing the amount of Gd2O3, a progressive depolymerization of 6-membered Ge[IV] rings is promoted, concomitant with an increase of Ge[IV] tetrahedra units with non-briding oxygens. The structural analysis through the local-sensitive techniques EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near Edge Structure) showed that the short-range structural modification around the elements Ge and Gd3+ does not change with the addition of Gd2O3 and the presence of germanium four-fold coordination [GeIV] and Gd3+ states, respectively. A simulation of the coordination number (N), the interatomic distance (R) of Ge–O and Gd–O bonds and the Debye-Waller factor was also carried out. The microstructure, after crystallization, of the sample with 15 mol% of Gd2O3 was evaluated using optical and electron microscopes. Finally, the paramagnetic behaviour and ion probe quantification of Gd3+ ions were obtained based on magnetic susceptibility measurements. São Paulo State University (Unesp) Institute of Chemistry São Carlos Institute of Physics University of São Paulo (USP) ICMCB CNRS Université de Bordeaux São Paulo State University (Unesp) Institute of Chemistry FAPESP: 2013/07793-6 FAPESP: 2019/01223-0

Made available in DSpace on 2021-06-25T10:16:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-19 Bismuth-containing rare-earth codoped fluoride phosphate glasses are promising materials for superbroadband near-infrared (NIR) emission with potential applications in optical amplification. To elucidate their structural organization, this contribution develops a comprehensive multinuclear solid-state single and 31P/19F double resonance NMR strategy, applied to glasses in the system (BiF3)y(50NaPO3-20Ba(PO3)2-20NaF-10BaF2)100-y (y = 0, 5, 10, 20, 30, 40). To separately assess the influence of bismuth and fluorine constituents on the network structure, an additional set of (NaPO3)50-2x(Ba(PO3)2)20-x(NaF)20+2x(BaF2)10+x (x = 0, 2.5, 5.0, 7.5) glasses was also investigated. Introduction of alkali fluoride ions into phosphate glasses is shown to follow a new network modification scheme involving depolymerization of polyphosphate chains under the formation of F-bonded fluorophosphate units. However, a significant part of the fluoride stays separate, interacting exclusively with metal-ion species. 23Na MAS and 23Na{31P} double resonance NMR results are consistent with a local sodium ion environment dominated by phosphate ions in the Bi-free system, whereas in the BiF3-containing glasses, the successive reduction of the dipolar second moment M2(Na-P) with increasing BiF3 content reflects the expected dilution effect, accompanied by increasing competition of the fluoride ions for ligation with the Na+ ions. São Carlos Institute of Physics São Paulo University-USP, Avenida Trabalhador Saocarlense 400 Institut für Physikalische Chemie Westfälische Wilhelms-Universität Münster, Corrensstrasse 30 Institute of Chemistry São Paulo State University-UNESP, Avenida Professor Francisco Degni, 55 Institute of Chemistry São Paulo State University-UNESP, Avenida Professor Francisco Degni, 55

CdFe2O4 nanoparticles of around 3.9 nm were synthesized using the coprecipitation method and protected by a silica layer. The nanoparticles were mixed with a coacervate and transformed into phosphate glasses with 1, 4 and 8% in mass of nanoparticles by the melt-quenching method. TEM images confirm that the nanoparticles were successfully incorporated into the matrix without inducing crystallization. 31P NMR and Raman spectral analyses show that new P-O-Si bonds are formed in the glasses containing nanoparticles. The glass transition increases as a function of the nanoparticle content due to an increase in the connectivity of the phosphate glass chains. The UV-Vis spectra show bands at 415 and 520 nm assigned to Fe3+ ions and at 1025 nm, characteristic of Fe2+ ions, indicating that some of the nanoparticles dissolve during the melting process. The sample with 8% CdFe2O4 presents a paramagnetic behavior. The glasses obtained are transparent, non-hygroscopic and possess enormous thermal stability which is important for the production of optical devices.

Made available in DSpace on 2018-12-11T16:47:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-10-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fluoro-tellurite glasses co-activated with Samarium (Sm3+) ions and silver nanoparticles (Ag NPs) were prepared using melt quenching technique. The nucleation and growth of Ag NPs were controlled by thermal annealing process. X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), UV–vis–NIR absorption spectroscopy, photoluminescence (PL) and PL lifetime spectroscopy were used to examine the annealing time dependence of the structural and luminescent properties. The amorphous nature of glasses has been confirmed by XRD spectra. The transmission electron microscopy images show the presence of silver NPs having an average diameter in the range of 20–40 nm. Selected area electron diffraction pattern (SAED), as well as EDX analysis spectrum confirm the presence of Ag NPs. Based on the absorption results, the intensity parameters Ωt (t=2, 4, 6), the radiative transition probability (AT), fluorescence branching ratio (βJJ’) and radiative lifetimes (τr) of Sm3+ ions were calculated using Judd-Ofelt theory. The results suggest that Sm3+ ions have been incorporated into Ag NPs, which intensified the electromagnetic field around Sm3+ ions. The luminescence properties of Sm3+ doped glasses were investigated. It was found that the presence of silver NPs nucleated and growth during the annealing process, improves the photoluminescence (PL) intensity and the PL lifetime relative to the transition from the 4G5/2 state to 6H5/2, 6H7/2, 6H9/2 and 6H11/2 states. Maximum enhancement is observed for the sample heat treated for 8 h. Such enhancement is mainly attributed to the local electric field created by the SPR of Ag NPs. whereas; the quenching is due to the energy transfer from Sm3+ ions to the silver nanoparticles as well as to the non-plasmonic, molecule likes Ag-particles (ML-Ag). The present results indicate that the glass heat-treated for 8 h has good prospect for Laser emissions at 600 nm. Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications Centre National de Recherches en Sciences des Matériaux, B.P. 95 Institute of Chemistry - São Paulo State University - UNESP, P. O. Box 355 Center for Photonic and Smart Materials (CPMS) Zewail City of Science and Technology, Sheikh Zayed District, 6th of October City Département de Physique Faculté des Sciences de Tunis University of Tunis El Manar Institute of Chemistry - São Paulo State University - UNESP, P. O. Box 355 FAPESP: #2013/07793-6 FAPESP: #2016/16343-2

Made available in DSpace on 2018-12-11T16:46:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-04-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Organic–inorganic hybrids (OIH) synthesized by sol gel process containing phosphotungstic acid (PWA) entrapped have been attracted much attention for ultraviolet sensitive materials. However, the limitations for practical photochromic application of these materials are the poor interaction with flexible polymer substrates such as Poly(ethyleneterephthalate) (PET) and also photo response under ultraviolet radiation. This paper describes the use of the d-ureasil HOI, based on siliceous network grafted through linkages to both ends of polymer chain containing 2.5 poly(oxyethylene) units with PWA entrapped prepared as films on recycled PET. Films were characterized by IR-ATR, XRD, TG/DTG, UV–Vis and Contact angle. XRD patterns showed that both pristine hybrid matrix and those containing PWA are amorphous. IR showed that PWA structure is preserved in the matrix and interactions between them occur by intermolecular forces. Films are thermally stable up to 325 °C and contact angle of 25.1° showed a good wettability between substrate and hybrid matrix. Furthermore, films showed fast photochromic response after 1 min of ultraviolet exposure time. The bleaching process revealed that the relaxation process is dependent of the temperature and the activation energy of 47.2 kJ mol−1 was determined. The properties of these films make them potential candidates for applications in flexible photochromic materials. Institute of Environmental Chemical and Pharmaceutical Sciences – Federal University of São Paulo Chemistry Institute São Paulo State University - UNESP Chemistry Institute São Paulo State University - UNESP

Made available in DSpace on 2018-12-11T16:51:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-01 Highly photoluminescent glasses were prepared by embedding silver nanoclusters (Ag NCs) in a fluorophosphate matrix using a melt-quenching method. The NCs sizes were varied through silver concentration and thermal annealing. Depending on the NC size and excitation wavelength, different colors can be generated ranging from blue to yellow. The tunable photoluminescence and the excellent stability of Ag NCs even after heat treatment are attractive features for photonic applications. In this sense, we demonstrated the fabrication of luminescent tridimensional waveguides in as-prepared glasses by femtosecond laser micromachining. The waveguides were found to emit and guide white light when excited at 325 nm. We foresee that this study presents promising results for the development of new photonic devices and data storage. Institute of Chemistry São Paulo State University UNESP São Carlos Institute of Physics University of São Paulo IFSC-USP Institute of Chemistry of São Carlos University of São Paulo Institute of Chemistry São Paulo State University UNESP

Made available in DSpace on 2019-10-06T15:54:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-10-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The incorporation of polyoxometalates in suitable matrices has been a main effort to produce transparent photochromic materials. Polymeric films based on high transparent polymethylmethacrylate (PMMA) containing phosphotungstic acid (PWA) have been obtained by casting and also by inkjet printing. In this investigation, polymeric PMMA matrix containing PWA were developed in an appropriate ratio of CH2Cl2/THF solvents to provide suitable transparent solution. PMMA/PWA composites obtained by casting were characterized by IR-ATR, Raman, XRD, TG/DTG, UV–Vis. Inkjet printing solution were characterized by surface tension (ST), viscosity and contact angle (CA) on glass substrate and films by optical microscopy. Infrared-ATR and Raman spectroscopies showed that the polyoxometalate structure was preserved in the polymeric matrix and the interaction between them occurred due to electrostatic forces. XRD indicated that PMMA and photochromic films were amorphous and display thermal stability up to 300 °C. Upon the UV irradiation, transparent films become blue and the photobleaching process were performed as a function of the temperature in a presence of air. These high transparent and photosensitive photochromic films present potential application as coating by casting and miniatured devices by inkjet printing. Deparment of Chemistry Federal University of São Paulo (UNIFESP) Chemistry Institute São Paulo State University - UNESP Araraquara University of Araraquara – Uniara Chemistry Institute São Paulo State University - UNESP Araraquara FAPESP: 2012/02708-8 FAPESP: 2013/07793-6

Made available in DSpace on 2019-10-06T17:09:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-08-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Agence Nationale de la Recherche Silver-containing glasses are promising candidates for photonic applications, due to the potentiality of spectroscopic properties of silver nanoclusters (NC's)and/or silver metallic nanoparticles. In this framework, silver-containing fluorophosphate glasses are candidates with a strong potential. Indeed, combined with femtosecond laser irradiation, silver NC's may be tailored in three-dimensional fluorescent micro-structures, whose spectroscopic properties have been investigated, revealing the creation of silver NC's but also of NP's during laser irradiation in the studied fluorophosphate glass. Additionally, the photo-inscription of silver NC's is correlatively accompanied by a positive index change, which has led to the demonstration of optical waveguiding behavior. Finally, the management of the reservoir of available silvers for laser inscription is investigated. Unlike previous observations made in standard oxide phosphate glasses, the considered silver-containing fluorophosphate glass exhibes an intriguing ability to be re-written when subjected to successive overlapping laser irradiations. Upon the optimization of compositions with tailored photo-sensitivity, the re-writable ability of fluorophosphate glasses paves the way to the design of advanced photonic devices such as photonic optical circuits, evanescent sensors or 3D high-density optical data storage. Institute of Chemistry São Paulo State University UNESP University of Bordeaux CNRS ICMCB UPR 9048, 87 avenue du Dr. A. Schweitzer University of Bordeaux CNRS CEA CELIA UMR 5107, 351 Cours de la Libération Institute of Chemistry São Paulo State University UNESP FAPESP: 2013/07793-6 FAPESP: 2016/16343-2 FAPESP: 2018/09296-3 Agence Nationale de la Recherche: N°ANR-17-CE08-0042-01

Made available in DSpace on 2019-10-06T15:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-03-01 A series of germanium glasses in the systems (100-x)[40GeO 2 -30Bi 2 O 3 -20PbO-10TiO 2 ] – (x) AgCl with x = 0, 1, 3 and 5 (mol%) was prepared using the melt-quenching method and then characterized taking into account their crystallization kinetics mechanisms and microstructural analysis. Through Differential Scanning Calorimetry (DSC) performed in different linear heating rate programs, the experimental data obtained were based on non-isothermal models of phase transformation, since their versatility allows us to calculate kinetic parameters, for example, activation energy for crystallization (E c ) and Avrami index n. Thus, it is possible to obtain information on the crystallization mechanism of these glasses. Independent of the model, the values of the Avrami index for each composition are the same, considering the uncertainty attributed to them. It is safe to affirm that bulk and surface nucleation contribute to the crystallization of compositions containing 0 and 1 mol% of AgCl, whereas internal and surface crystallization with one-dimensional growth occur in samples with 3 and 5 mol% of AgCl, respectively. These results were supported by a microstructural analysis from bulk samples that underwent non-isothermal heat treatment at different temperatures according to DSC crystallization peak. São Paulo State University (Unesp) Institute of Chemistry São Paulo State University (Unesp) Institute of Chemistry

Made available in DSpace on 2019-10-06T15:25:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-02-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Oxyfluoride glasses with composition x WO3 - 30 NaPO3 - (70-x) NaF, with 30 ≤ x ≤ 70 were prepared by melt-quenching and characterized with respect to their bulk physical properties and ionic conductivities. As the NaF content increases, the glass transition temperature, Tg, decreases systematically. Impedance measurements reveal no clear effect of NaF content upon room temperature electrical conductivities and activation energies. There is, however, a significant decrease of the Arrhenius pre-exponential factor with increasing WO3 content, suggesting that the electrical conductivities measured in this glass series are increasingly influenced by an electronic contribution. This contribution may be related to a W5+ → W6+ electron hopping process detected in the optical absorption spectra. Detailed spectroscopic investigations by Raman scattering and multinuclear one- and two-dimensional solid-state NMR experiments indicate that NaF acts like a network modifier resulting in the formation of W-F bonds via breakage of W-O-W and W-O-P linkages, with the former process being the preferred one. The concomitant decrease in network connectivity caused by these processes accounts for the experimentally observed decrease in glass transition temperatures with increasing NaF contents. Chemistry Institute São Paulo State University – UNESP Chemistry Department Federal University of São Carlos -UFSCar São Carlos Institute of Physics University of São Carlos -USP Department of Materials Engineering Federal University of São Carlos -UFSCar Institut für Physikalische Chemie Westfälische Wilhelms-Universität Münster Chemistry Institute São Paulo State University – UNESP FAPESP: 2013/07793-6 FAPESP: 2013/23490-3

Made available in DSpace on 2019-10-06T15:44:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Here, we report the luminescence properties of Yb3+/Pr3+ dual-doped fluorophosphate glasses containing silver clusters. Through the solubility of silver into the glass system as function of its initial concentration, charged species characterized as Ag+ and Agmn+ were formed and identified according to their absorption and emission spectral responses. By changing the transition metal concentration, multi-energy transfer mechanisms were observed between silver and Yb3+/Pr3+ co-doped glasses. The stabilization of silver species seems to be detrimental to the radiative processes of the rare earth ions under excitation at 444 nm (Pr3+3H4 → 3P0 absorption line). In other words, the main visible emissions of Pr3+ and the NIR emission of Yb3+ decrease with increment of Ag concentration. However, energy transfer occurs for large spectral range by the excitation of the silver species. In consequence, the visible and NIR emission could be activate in a broadband from ultraviolet to the blue part of the spectral region. These two observations highlight the competitive absorption processes and probabilities between the cationic elements and the interest to use the transition metal species as sensitizers to excite the rare earth elements. Institute of Chemistry - São Paulo State University - UNESP, CP 355 University of Bordeaux CNRS ICMCB UPR 9048, 87 Avenue du Dr. A. Schweitzer University of Bordeaux CNRS CEA CELIA UMR 5107, 351 Cours de la Liberation Institute of Chemistry - São Paulo State University - UNESP, CP 355

Made available in DSpace on 2021-06-25T10:21:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-25 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Glass-ceramics containing rare earth gallium garnets were obtained using glass compositions as reactional medium. This work reports on the synthesis, and structural, morphological, and optical characterizations of Er3+ and Tm3+-doped Yb3Ga5O12 crystals prepared from controlled cooling of heavy metal oxide glass melts. Micrometric cubic crystals were obtained by controlling the cooling of a rare earth-supersaturated glassy composition melted at high temperature. Crystals with sizes ranging between 5 and 150 µm were formed into the glass matrix. A gallium garnet phase corresponding to space group Ia-3d was identified by X-ray diffraction and confirmed by Rietveld simulations. The morphology of crystals was studied by optical and scanning electron microscopies, while chemical elements were mapped by electron dispersive X-Ray spectroscopy. The glass phase was studied by XRD, thermal analysis and Raman spectroscopy. The optical properties of both glass and glass-ceramic materials were evaluated by UV–Vis and luminescence spectroscopies. Micro-luminescence measurements confirmed that rare earths were incorporated into the crystalline phase. Intense upconversion emissions of Er3+ (550 and 660 nm) and Tm3+ (800 nm) were observed when the glass-ceramics were pumped at 980 nm. These new glass-ceramics are excellent candidates for the development of photonic devices. Institute of Chemistry – São Paulo State University – UNESP São Carlos Institute of Physics University of São Paulo University of Bordeaux CNRS ICMCB UPR 9048 University of Bordeaux CNRS ISM UPR 5803 Institute of Chemistry – São Paulo State University – UNESP FAPESP: 2013/07793-6 FAPESP: 2019/01223-0 CNPq: 502391/2014-6

Made available in DSpace on 2018-12-11T17:23:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-01 Nickel polyphosphate coacervates have been prepared through the coacervation process of sodium polyphosphate and Ni2+ chloride solutions by the addition of different solvents with low molecular weight. The great potential of nickel polyphosphate coacervates as a material precursor was demonstrated by preparation of nickel polyphosphate glass-ceramics. Structural and spectroscopic properties were analyzed by thermal analysis, X-ray powder diffraction, Raman spectroscopic and UV-VIS techniques. Raman spectra for the nickel polyphosphate coacervates and nickel polyphosphate coacervates glass-ceramics samples shows that the addition of solvents leads to a depolymerization of the polyphosphate chains, resulting in an increase of shorter chains species based on pyrophosphates. The identification and quantification of Ni2P4012, β-Ni2P2O7 and δ-Ni2P2O7 crystalline phases present in the nickel polyphosphate glass-ceramics were carried out by X-ray powder diffraction using the Rietveld method. Quantitative phase analyses of the three polymorph forms were also evaluated. Based on interpretation of reflectance spectroscopy and Rietveld refinement, Ni2+ ions may occupy distorted octahedral and tetrahedral sites. LAVIE Department of Chemistry Federal University of São Carlos-UFSCar, CP 676 Institute of Chemistry Universidade Estadual Paulista-Unesp, P. O. Box 355 Laboratório de Biopolímeros e Biomateriais (BioPolMat) Centro Universitário de Araraquara (UNIARA) Núcleo de Espectroscopia e Estrutura Molecular-NEEM Departamento de Química Instituto de Ciências Exatas Universidade Federal de Juiz de Fora-UFJF Institute of Chemistry Universidade Estadual Paulista-Unesp, P. O. Box 355

Made available in DSpace on 2018-12-11T17:38:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-12-20 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Surface-enhanced Raman scattering (SERS) is one of the most sensitive methods for the detection of adsorbed molecules on the nanostructured coinage-metal surface. The enhancements in the order of 104–106 are routinely observed. Such an effect makes SERS spectroscopy a technique applicable to the study the adsorption of analytes in the submonolayer regime. Novel SERS sensors require novel substrates with high activity for great sensibility detection of different molecules applied in many fields, such as detections of narcotics, explosives, and molecules with biological interest. In this work, silver nanoparticles embedded in niobium lead-pyrophosphate glasses (Pb2P2O7-Nb2O5-Na2O) were prepared by ion exchange process, where silver ions were introduced into glass surface by Ag+/Na+ ion exchange (NaNO3:AgNO3 batch), and reduced to metallic silver by heat treatment at glass transition temperature (ca. 480 °C). The new substrate was characterized by Raman spectroscopy, optical absorption, transmission electron microscopy (TEM) and atomic force microscopy (AFM). Its application in SERS was demonstrated by studying the adsorption of 2,2-bipyridine (bpy) on the glass surface, which has marker bands for the coordination of the adsorbate with silver atoms. The optimal surface features in terms of SERS enhancement were also discussed and the sensing ability of this new substrate was demonstrated. São Carlos Institute of Chemistry – IQSC University of São Paulo – USP Institute of Chemistry São Paulo State University – UNESP Materials Engineering Department – DEMA Federal University of São Carlos – UFSCar Department of Chemistry Federal University of Juiz de Fora – UFJF Institute of Chemistry São Paulo State University – UNESP FAPESP: 2013/07793-6 FAPESP: 2016/16900-9 CNPq: 502391/2014-6

Made available in DSpace on 2018-12-11T16:54:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-11-15 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) This work presents the production and characterization of a new prolific binary glass system based on SbPO4-GeO2. The dependence of GeO2 content on thermal, structural and optical properties were investigated by means of thermal analysis, Raman, UV–Vis-NIR, infrared, M-lines and EPR spectroscopy. Glass transition temperatures remain constant around 410 °C when GeO2 content is increased, indicating that GeO4 units are not responsible for increasing the connectivity of PO4 units. Thermal stability linearly increases as a function of GeO2 content, reaching a value around 400 °C for glass containing 90 mol% of GeO2. Raman spectroscopy was used to evaluate the glass structural changes when GeO2 is incorporated from 30 to 90 mol% indicating a gradual change from a phosphate to a germanate glass skeleton. The optical window extends from 350 nm at UV region, up to 2.7 μm in the middle-infrared region limited by the multiphonon cut-off due to the strong OH absorption. M-lines technique shows that increasing GeO2 content decreases the refractive index, mainly because the lower concentration of higher polarizable antimony atoms. EPR spectra of heat treated V2O5 doped glasses, at different temperatures above the glass transition temperature, shows the characteristic eight-line hyperfine splitting spectrum. The spin Hamiltonian parameters obtained from the simulated spectra indicates that the paramagnetic tetravalent vanadium ions in the glasses exist as vanadyl form VO2+, located in axially distorted octahedral sites. For glasses treated at higher temperatures a second VO2+ component appears in the EPR spectra and the analysis of the spin-Hamiltonian parameters suggests that these vanadyl ions are in more tetragonal distorted octahedral sites than those in the glass. Institute of Chemistry São Paulo State University – UNESP São Carlos Institute of Chemistry University of São Paulo – USP-IQSC São Carlos Institute of Physics University of São Paulo -USP-IFSC Dipartimento di Chimica Università di Torino, Via P. Giuria, 7 Chemistry Department Federal University of São Carlos Institute of Chemistry São Paulo State University – UNESP FAPESP: 2013/07793-6

Made available in DSpace on 2018-12-11T17:37:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-11-01 The various synthesis conditions to obtain a material based on SiO2-TiO2 co-doped with Er3+/Yb3+/Eu3+ were investigated, searching for those that present the greatest potential to improve the efficiency of solar cells. Conditions adjusted included heat-treatment temperatures, concentrations of matrix, and concentrations of dopants. Raman spectroscopy results demonstrated the effect of the annealing temperatures on the TiO2 phase transition and the crystalline phase of the materials, which interfere with the photoluminescence of the materials. The band gap of the materials was evaluated by diffuse reflectance and it decreased due to the doping. The materials were able to absorb UV and IR energy and emit in the visible region, verified by the down conversion, up conversion and the double excitation of the materials. The results showed that the materials may be used as a strategy to use a greater portion of the solar spectrum, improving solar cell efficiency. Grupo de Pesquisa em Química de Materiais – (GPQM) Departamento de Ciências Naturais Universidade Federal de São João Del Rei Campus Dom Bosco, Praça Dom Helvécio, 74 São Carlos Institute of Chemistry – IQSC University of São Paulo – USP Instituto de Química UNESP, P.O. Box 355 Department of Chemistry and Physics University of Tennessee at Martin Desenvolvimento de Materiais Inorgânicos com Terras Raras – (DeMITeR) Instituto de Química – (IQ), Universidade Federal de Uberlândia – (UFU) Av. João Naves de Ávila, 2121, Bairro Santa Mônica Instituto de Química UNESP, P.O. Box 355

Made available in DSpace on 2018-12-11T16:49:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The emission properties of Ag nanoclusters (Ag NCs) dispersed in a transparent fluorophosphate glass host have been studied. The as-prepared glass shows that the Ag NCs emit a broad white emission band almost covering the entire visible region. By changing the excitation wavelength it is possible to tune the emission from blue to yellow. The spectral width of the white light is most likely due to the presence of a variety of Ag NCs with different sizes, particularly emitting in the blue, green and red regions. The possible interaction mechanism between the different Ag species was also elucidated. The observed results provide a new platform to acquire a broad band tunable light source. Institute of Chemistry São Paulo State University UNESP, P. O. Box 355 Institute of Chemistry São Paulo State University UNESP, P. O. Box 355 FAPESP: #2013/07793-6 FAPESP: #2016/16343-2

Made available in DSpace on 2019-10-04T13:15:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-10-01 Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) FINEP Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Niobium alkali germanate glasses doped with Er3+ up to 4.0 mol% were synthesized by the melt-quenching technique. Glass-ceramics were obtained by controlled heat treatment of the pristine glass. Thermal and optical properties were investigated and are shown to depend on the erbium content. The main radiative parameters were obtained based on the Judd-Ofelt theory. The change of radiation energy processes and modification of the environment of the earth-rare ion occurs in samples with high erbium concentrations. In general, strong enhancement of upconversion emission occurs due to the efficient process of excited-state absorption for the high erbium content samples. Visible tunable phosphors emitting either red-to-green light depends on the erbium content and heat treatment. In addition, these glasses and glass-ceramics samples have high thermal stability and wide transmission window. For these reasons, Er3+-doped niobium germanate glasses and glass-ceramics may be suitable for photonic device applications, especially as visible laser. Univ Fed Alfenas, Grp Quim Mat, Campus Pocos Caldas, Pocos De Caldas, MG, Brazil Univ Sao Paulo, Fac Filosofia, Dept Quim Ciencias & Letras Ribeirao Preto, Ribeirao Preto, SP, Brazil Univ Sao Paulo, Inst Fis Sao Carlos, Sao Carlos, SP, Brazil Univ Sao Paulo, Inst Quim Sao Carlos, Sao Carlos, SP, Brazil Univ Estadual Paulista, Inst Quim, Araraquara, SP, Brazil Univ Estadual Paulista, Inst Quim, Araraquara, SP, Brazil FAPESP: 2013/07793-6

We have prepared heavy metal oxide glasses containing metallic copper nanoparticles with promising nonlinear optical properties which were determined by Z-scan and pump-probe measurements using femtosecond laser pulses. For the wavelengths within the plasmon band, we have observed saturable absorption and response times of 2.3 ps. For the other regions of the spectrum, reverse saturable absorption and lifetimes shorter than 200 fs were verified. The nonlinear refractive index is about 2.0 × 10−19 m2/W from visible to telecom region, thus presenting an enhancement effect at wavelengths near the plasmon and Cu+2 d–d band.

Made available in DSpace on 2018-12-11T17:23:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-09-01 This paper describes the preparation of Sodium Polyphosphates Coacervates (NaPC) through the direct addition of different methanol molar fractions to a sodium polyphosphate solution. The presence of methanol reduces the dielectric constant medium and it promotes the coacervate formation. Rheology measurement shows that the NaPC viscosity is dependent on a methanol molar fraction, which is caused by the dielectric constant reduction of the water-methanol mixture. Raman spectra for the lyophilized NaPC show that the symmetric P-Ot stretching mode is more sensitive than the symmetric P-Ob stretching mode, due to the approach of the adjacent polyphosphate chains. The 31P NMR spectra also confirm a decrease in the Q2/Q1 ratio because of the methanol content. Besides, we have obtained transparent soft Glass-Materials to melt NaPC at 800 °C. Institute of Chemistry – São Paulo State University – Unesp, P.O. Box 355 Laboratório de Biopolímeros e Biomateriais (BioPolMat) – Centro Universitário de Araraquara (UNIARA) Núcleo de Espectroscopia e Estrutura Molecular – NEEM Departamento de Química Instituto de Ciências Exatas Universidade Federal de Juiz de Fora NUPIS (Núcleo de Pesquisa em Instrumentação e Separações Analíticas) Departamento de Química Instituto de Ciências Exatas Universidade Federal de Juiz de Fora School of Pharmaceutical Sciences São Paulo State University – UNESP Institute of Chemistry – São Paulo State University – Unesp, P.O. Box 355 School of Pharmaceutical Sciences São Paulo State University – UNESP

Made available in DSpace on 2018-12-11T17:23:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-07-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The preparation of composite materials has gained tremendous attention due to the potential synergy of the combined materials. Here we fabricate novel thermal/electrical responsive photonic composite films combining cellulose nanocrystals (CNC) with a low molecular weight nematic liquid crystal (NLC), 4′-(hexyloxy)-4-biphenylcarbonitrile (HOBC). The obtained composite material combines both intense structural coloration of photonic cellulose and thermal and conductive properties of NLC. Scanning electron microscopy (SEM) results confirmed that liquid crystals coated CNC films maintain chiral nematic structure characteristic of CNC film and simultaneously, transversal cross-section scanning electron microscopy images indicated penetration of liquid crystals through the CNC layers. Investigated composite film maintain NLC optical properties being switchable as a function of temperature during heating/cooling cycles. The relationship between the morphology and thermoresponsive in the micro/nanostructured materials was investigated by using transmission optical microscopy (TOM). Conductive response of the composite films was proved by Electrostatic force microscopy (EFM) measurement. Designed thermo- and electro-responsive materials open novel simple pathway of fabrication of CNC-based materials with tunable properties. São Paulo State University (Unesp) Institute of Chemistry, CP 355 Group ‘Materials + Technologies’ (GMT) Department of Chemical and Environmental Engineering Engineering College of Gipuzkoa University of the Basque Country (UPV/EHU), Plaza Europa 1 Laboratório de Biopolímeros e biomateriais (BioPolMat) Universidade de Araraquara São Paulo State University (Unesp) Institute of Chemistry, CP 355

Made available in DSpace on 2018-11-27T16:00:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-07-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Air Force Office of Scientific Research Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In this study we present the production and characterization of Pb2P2O7-Nb2O5 glasses and optical fibers. The dependence of Nb2O5 content on thermal, structural and optical properties were investigated by thermal analysis (DSC), Raman spectroscopy, IN-Visible absorption, M-Lines and Z-scan techniques. Glass transition temperature (T-g) increased linearly with Nb2O5 content up to 60 mol%, while thermal stability against crystallization (AT) reached a maximum value of 225 C at 40 mol% of Nb2O5. Raman spectra showed a significant structural change by the insertion of Nb06 octahedral units in the glass network. The increase of Nb2O5 concentration shifts the glasses absorption edge to lower energies, and also increases the linear refractive indexes (no) due to the high polarizability of niobium atoms and formation of non -bridging oxygen. Similarly to no, an increase in the positive values of nonlinear refractive indexes was observed using Z-Scan technique with increase of Nb205 content, based on structural changes caused by the replacement of Pb2P2O7 instead Nb205. The average of n(2) values at 500-1500 nm raised from 2.2 x 10(-19) to 3.8 x 10(-19) m(2)/W, when the Nb2O5 content was increased from 10 to 60 mol%. Lastly, a core -cladding preform was produced by suction method and the optical fiber drawn. The sample containing 40 mol% of Nb2O5 was used for presenting the highest thermal stability against crystallization and no values >2 from green to near-infrared wavelengths. Multimode step index fiber with good core circularity and concentricity was produced and the optical losses were determined by cut-back method at visible and near infrared ranges. (C) 2016 Elsevier B.V. All rights reserved. Univ Estadual Paulista UNESP, Inst Quim, CP 355, BR-14801970 Araraquara, SP, Brazil Univ Sao Paulo, Sao Carlos Inst Phys, Sao Carlos, SP, Brazil Univ Fed Sao Carlos, Dept Chem, BR-13560 Sao Carlos, SP, Brazil Univ Estadual Paulista UNESP, Inst Quim, CP 355, BR-14801970 Araraquara, SP, Brazil FAPESP: 2010/20776-5 FAPESP: 2013/07793-6 FAPESP: 2011/12399-0 FAPESP: 2011/21434-3 Air Force Office of Scientific Research: FA9550-12-1-0028 CNPq: 502391/2014-6

Made available in DSpace on 2022-04-28T19:45:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The development of glasses containing nanoparticles dispersed homogeneously with controlled size and optimum parameters for functionality is a big challenge. In the present work, the ternary system 60SbPO4-30ZnO-10PbO containing CdFe2O4-SiO2 nanoparticles was studied. CdFe2O4 nanoparticles, with average size of 3.9 nm, were synthesized using the coprecipitation method and, in a second step, protected by a silica layer. Different mass percentages of nanoparticles were mixed to the glass precursors and then transformed into glasses by melt-quenching method. Thermal and structural properties were evaluated by differential scanning calorimetry, Raman spectroscopy, scanning electronic microscopy and transmission electron microscopy. While the optical properties were studied by M-Lines spectroscopy and UV-Vis spectroscopy. The glasses obtained were completely transparent, with yellow color and showed no sign of crystallization according to the techniques used. Scanning and transmission electron microscopy confirm that the methodology used for the incorporation of nanoparticles was efficient. The methodology used to protect the nanoparticles prior to incorporate them to glasses, strongly contributes towards the development of new functional glasses useful for magneto-optics devices. São Paulo State University (Unesp) Institute of Chemistry, 55 Prof. Francisco Degni St, São Paulo São Paulo State University (Unesp) Institute of Chemistry, 55 Prof. Francisco Degni St, São Paulo FAPESP: #2013/07793-6 CNPq: 141258/2014-4

Vitreous samples were prepared in the NaPO3–BaF2–WO3 ternary system with high WO3 concentrations. These glasses exhibit a strong absorption in the visible due to the presence of reduced tungsten species and the use of oxidizing species is required. The couple Sb2O3/NaNO3 was introduced in the composition and allowed to obtain transparent glasses. These oxidized samples were illuminated by visible laser radiation and showed an efficient volumetric photochromic effect. The photosensitive effect appeared as a dark spot throughout the entire volume of the glasses. The effect was investigated by several techniques such as, UV-visible absorption, Raman and XANES at the L1 and L3 tungsten absorption edges. The results suggest a photoreduction of tungsten atoms without structural changes of the viteous network. Finally, the photochromic effect can be erased by thermal treatment at 200 °C for a few minutes.

Journal of the Brazilian Chemical Society : JBCS 26(12), 2607-2614 (2015). doi:10.5935/0103-5053.20150289 special issue: "Special Issue International Year of Light", Published by SBQ, São Paulo

Glasses in the ternary system (Sb 2 O 3 ) (0.6-x) (SbPO 4 ) (0.4) (WO 3 ) (x) , with composition 0.1 £ x £ 0.5 were studied. The structural changes due to the replacement of Sb 2 O 3 by WO 3 have been investigated. It was found that the incorporation of WO 3 enhances the thermal stability of the glasses against devitrification when compared to the binary Sb 2 O 3(0.6) - SbPO 4(0.4) composition. The connectivity of the network increases with WO 3 content which is consistent with the high values of the glass transition temperature. Raman studies suggest that WO 3 incorporation breaks the primary network, constituted by antimony oxide, while a second network containing WO 6 octahedral units is built up. Thermal and structural properties were evaluated by differential scanning calorimetry, infrared and Raman spectroscopies, 31 P Magic Angle Spinning NMR and X-ray absorption near edge structure (XANES) at L 1 and L 3 edges of Sb and L 1 edge of W atoms.

The third-order optical properties of GeO2–Bi2O3–PbO–TiO2 glasses at 532 nm and 1,064 nm were studied to evaluate their potential for optical limiting and all-optical switching. The Z-scan technique was used to determine the nonlinear (NL) refractive index, n 2, and the NL absorption coefficient, α 2, of samples with different amounts of the constituent oxides. Values of n 2 ≈ + 0.7 × 10−14 cm2/W at 1,064 nm and ≈+1.5 × 10−14 cm2/W at 532 nm were measured. The NL absorption coefficient, α 2, was smaller than the minimum that our apparatus can measure (α 2 < 0.01 cm/GW) in the near-infrared (1,064 nm); in the visible region (532 nm), we obtained α 2 ≈ 4.4 cm/GW. The set of NL parameters measured indicates the potential usefulness of the GeO2–Bi2O3–PbO–TiO2 glasses for all-optical switching at 1,064 nm and for optical limiting at 532 nm.

International audience; The influence ofboththermaltreatmentandlaserirradiationonthestructuralandopticalpropertiesoffilms intheSb2O3–Sb2S3 systemwasinvestigated.The films werepreparedbyRF-sputteringusingglassThe influence of both thermal treatment and laser irradiation on the structural and optical properties of films in the Sb2O3–Sb2S3 system was investigated.The films were prepared by RF-sputtering using glass compositions as raw materials. Irreversible photodarkening effect was observed after exposure of the films to a 458nm solid state laser. It is shown, for the first time, the use of holographic technique to measure “in situ”, simultaneously and independently, the phase and amplitude modulations in glassy films. The films were also photo-crystallized and analysed “in situ” using a laser coupled to a micro-Raman equipment. Results showed that Sb2S3 crystalline phase was obtained after irradiation. The effect of thermal annealing on the structure of the films was carried out. Different from the result obtained by irradiation, thermal annealing induces the crystallization of the Sb2O3 phase. Photo and thermal induced effects on films were studied using UV–Vis and Raman spectroscopy, atomic force microscopy (AFM), thermal analysis (DSC), X-raydiffraction, scanning electron microscopy (MEV) and energy-dispersive X-ray spectroscopy (EDX).

Glass formation has been investigated in binary systems based on antimony oxide as the main glass former: (100 - x)Sb 2 O 3-x WO 3 , (5 < x < 65), (100 - x)Sb 2 O 3-x SbPO 4 , (5 < x < 80) and (100 - x)Sb 2 O 3-x [Sb(PO 3 ) 3 ] n , (10 < x < 40). Ternary systems derived from the Sb 2 O 3 -WO 3 binary glass have also been studied: Sb 2 O 3 -WO 3 -BaF 2 , Sb 2 O 3 -WO 3 -NaF and Sb 2 O 3 -WO 3 -[Sb(PO 3 ) 3 ] n . Glass transition temperature ranges from 280°C to 380°C. It increases as the concentration in tungsten oxide or antimony phosphate increases. Refractive index is larger than 2. Tungsten-containing glasses are yellow in transmission and turn green at the largest WO 3 content. Optical transmission and temperatures of glass transition, T g , onset of the crystallization, T x , and maximum of crystallization, T p , have been measured using differential scanning calorimetry (DSC). These glasses have potential photonic applications.

Holographic techniques are powerful tools to study photosensitive materials due to the high sensitivity of diffraction measurement and the ability to detect dynamic gratings. The self diffraction technique consists in to project an interference fringe pattern into the photosensitive material and to measure, in real time, the self-diffraction of the interfering beams, at the grating generated in the photosensitive material. Besides the higher sensitivity, such measurement allows to measure simultaneously and separately the phase and the amplitude grating contributions, as well as thin or thick gratings. In order to demonstrate potentiality of this technique we measured the kinetic constant of the photo-reaction in positive photoresists (AZ types) and negative SU-8 photoresist, as well as the maximum values of the refractive index and of the absorption coefficient modulations induced in these materials at different wavelengths of exposure. The same measurements were performed in SB based chalcogenide glasses in order to evaluate the potential of such materials to be used as optical data storage devices.

In this work, we designed and recorded two-dimensional Hexagonal Photonic Crystals (2D-HPC) layers, with a linear waveguide, in erbium doped GeO 2 -Bi 2 O 3 -PbO-TiO 2 glassy films, by combining the techniques of holographic recording and femtosecond (fs) laser micromachining. The 2D-HPC is recorded holographically in a photoresist film coated on a glass substrate by exposing the sample to the same interference pattern twice and rotating the sample of 60° between the exposures. After the development a two dimensional hexagonal array of photoresist columns remain on the glass substrate. The recording of the waveguide is made by a fs laser micromachining system focused at sample surface. The laser spot produces the ablation of the photoresist columns generating a defect line in the periodic hexagonal array. After the recording of the photoresist template, the erbium doped GeO 2 -Bi 2 O 3 -PbO-TiO 2 film is evaporated on the photoresist and finally the photoresist template is removed using acetone. The design of the geometrical parameters of the 2D-HPC is performed by calculation of the dispersion mode curves of the photonic crystal using a 2D finite element method. The proper geometrical parameters depend on both the refractive index of the glass film and thickness. Such parameters as well as the period of the 2D-HPC have been defined in order to obtain a photonic band gap in the region of erbium luminescence band. In such condition the erbium luminescence will propagate only through the waveguide.

Made available in DSpace on 2018-12-11T16:44:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-11-01 Polychromatic tunable visible light emission in the region of the low correlated color temperature range using Dy3+/Tb3+ codoped PbGeO3:PbF2:CdF2 glass phosphor under UV-blue LED light excitation is presented. The glass phosphor was synthesized and the light emission feature was examined under UV-blue (353, 375, 385, and 405 nm) excitation. Emission around 484, 573, 663, and 754 nm due to dysprosium, and 488, 545, 585, 620, and 690 nm owing to terbium ions, was observed and analyzed as a function of the dysprosium and terbium contents and excitation wavelength. The excitation spectrum was examined and showed resonance peaks around 385 nm for the 573-nm emission of Dy3+, and 375 nm for the 545 nm of Tb3+. Energy-transfer process from Dy3+(F49/2) to Tb3+(D54) was also observed. Results indicated that the polychromatic visible light emitter herein reported produced light possessing tunable color tone via excitation wavelength and ions' mass ratio. The tint of the tunable overall emission resided in the warm region of the white-light boundary of the CIE-1931 chromaticity diagram. Universidade Federal de Alagoas Instituto de Física Universidade Federal Do ABC Santo André CEMCSA Instituto de Química UNESP Instituto de Química UNESP