Search

Novel luminescent In-based lead-free double halide perovskites co-doped with Yb3+/Er3+ have been synthesized. Their primary thermometer performance was assessed and their biological application to predict temperature was evaluated.

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

One of the main approaches toward obtaining efficient up converting materials with practical applications involves the development of composites with synergism between components. Herein, we reported an optical temperature sensing using up-conversion fluorescence emission at 530 and 550 nm in the Er3+/Yb3+-co-doped NaYF4 nanoparticles and SBA-15/NaYF4:Yb,Er composites excited at 976 nm. Nanoparticles and composites were prepared and investigated by X-ray diffractometry, N2 adsorption–desorption isotherms, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and up-conversion photoluminescence. Spherical like NaYF4:Yb,Er nanoparticles exhibited a mixture of hexagonal and cubic phases, while the rare earth ions incorporated inside of SBA-15 mesopores crystallized in a cubic phase. Optical thermometry property was investigated in the temperature range from 30 to 90 °C, and a maximum absolute sensitivity were 0.03/°C and 0.38/°C for nanoparticles and composites, respectively. The lower temperature range makes the composites with potential for application in biological systems.

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

Glass and glass-ceramics containing nanocrystals of Bi

Er3+/Yb3+-Codoped tellurite glass-ceramics showed luminescence dependent on crystallization, promising to attend needs for the development of efficient photonic devices.

Study to obtain a near-infrared optical thermometer with Nd3+-doped fluoroborontellurite matrix, measured emission intensities of the (4F5/2, 4F3/2) → 4I9/2. For 3.0% Nd, and 300K, the relative sensitivity is 1.48K-1%.

Phosphotellurite based glasses have interesting features such as low characteristic temperatures, high glass forming ability, high thermal stability against crystallization and a broad transparency window from ultraviolet (UV) to near-infrared (NIR), which makes them promising materials for photonic applications. In this work, phosphotellurite binary glasses, having a composition (100 − x)TeO2 − xBa(PO3)2 with x varying from 1 to 20 mol%, were synthesized by the conventional melt-quenching method in covered gold crucibles under air. Optical, physical and structural properties of the new glass samples were investigated by differential scanning calorimetry, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, linear optical absorption from UV to NIR, IR transmittance, and optical limiting experiments. Transparent glass-ceramics in the visible range were obtained for phosphotellurite samples containing 2, 4 and 6 mol% of Ba(PO3)2 and the phase crystallization was investigated through Rietveld analysis and transmission electron microscopy. The incorporation of Ba(PO3)2 into the TeO2 network drastically increases the thermal stability against devitrification and helps to shift the infrared multiphonon absorption edge to longer wavelengths. Nonlinear measurements performed with a picosecond laser at 532 nm indicate large effective nonlinear absorption coefficients for all samples. In summary, the dependence of the spectroscopic properties on the compositions of the samples revealed promising transparent glass and glass-ceramics for photonic applications.

CdTe/Er3+-codoped SiO2–Nb2O5-based nanocomposites were prepared by a sol-gel route. The thermal, structural and photophysical properties were investigated by FTIR spectroscopy, N2 adsorption/desorption isotherms, XRD, TGA and DSC analysis, TEM images, UV–Vis spectroscopy, and photoluminescence. The influence of QDs content and niobium/erbium addition on these properties were studied. It is shown that the QDs content into the nanocomposites influences their average size and photoluminescence properties. High QDs content resulted in larger nanocomposite pore size and higher QDs average size. The average pore size created by QDs-doped samples has dimensions suitable for QD adsorption. The TEM images and photoluminescence results demonstrate the successful incorporation of CdTe QDs into the SiO2–Nb2O5 host, which results in a homogeneous nanocomposite material presenting tunable fluorescence in the range of 513–568 nm in function of QD content. Furthermore, CdTe-doped SiO2–Nb2O5-based mesoporous nanocomposite allows the QD chemical stability capped by MPA. These nanocomposites may have a potentially broad application as photonic devices, such as broadband emission devices, optical amplification and lighting.

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

This study is focused on the development of a nanodevice for loading and release of 5-Fluorouracil (5-FU) with a view to improving its therapeutic efficiency, using as strategy the fabrication of a nanoconjugate through drug anchorage on the surface of carbon quantum dots (CQD). Several physicochemical and analytical techniques were employed to obtain information about materials morphology, structure, and optical properties. The results indicated that the interactions between both entities resulted in good physicochemical properties and photostability. Acid pH favored drug release, indicating a tendency to release 5-FU from 5-FU-CQD into the tumor microenvironment. The cytotoxicity of CQD and 5-FU-CQD nanoconjugate was evaluated against normal human lung fibroblast (GM07492A) and human breast cancer (MCF-7) cell lines. The CQD was non-toxic, indicating that these materials are biocompatible and can be used as a nanocarrier for 5-FU in biological systems. For the 5-FU-CQD nanoconjugate, it was observed a reduction in toxicity for normal cells compared to free 5-FU, suggesting that drug anchoring in CQD reduced drug-associated toxicity, while for cancer cells exhibited an antitumor effect equivalent to that of the free drug, opening perspectives for the application of this material in anticancer therapy.

In this work we used two glass stability (GS) parameters, which best correlate with the glass-forming ability (GFA), in an extensive study for analyzing the influence of alkali and alkaline earth modifiers and five glass-formers, in the crystallization resistance of binary oxide glasses. For the good glass formers silica, boria and germania, the addition of small amounts of modifiers rapidly reduces the GS, whereas for the conditional glass formers telluria and alumina, it initially increases the GS. Lower liquidus temperatures are associated with a better GS, and above 50 molar percent of modifier oxide, the liquidus temperature seems to be the main factor controlling GS (except for telluria). Lithium containing glasses show the lowest GS between the alkali systems, while the alkaline earth modifiers show the same effect on the GS. The TeO2 is the only exception, for which the barium tellurites show better GS. The pure oxides rank in the following order of GS: B2O3>SiO2>GeO2>TeO2>Al2O3.

Tellurite-zinc glasses doped with Er3+, Yb3+ and Tm3+ were fabricated by conventional melt-quenching technique and characterised by absorption spectroscopy, refractive index, lifetime measurements, excitation, luminescence and up-conversion spectroscopy. Tunable blue to cold white light emission based on the colour mixing of red, green and blue light was obtained via up-conversion under 980 nm and by adjusting the laser excitation intensity. The balancing of the relative intensity of each colour is provided by the energy transfer process between the rare-earth ions. Moreover, luminescence spectroscopy was performed with a 405 nm laser to further understand the energy transfer mechanism that produce the white light. The Judd-Ofelt intensity parameters ( Ω 2 , Ω 4 and Ω 6 ) were calculated for all samples and present the trend Ω 2 > Ω 4 > Ω 6 . The spectroscopic parameters were computed with the Judd-Ofelt theory as well as the energy transfer micro-parameters (critical radius of interaction and energy transfer coefficient). Such results shall be used to give a comprehensive explanation for the energy transfer process between these rare earth ions.

Made available in DSpace on 2020-12-12T02:30:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-03-01 This study was performed to prove the feasibility of a direct impedimetric DNA genosensor by using biotin self-assembled monolayer (SAM). The sensor was composed of a gold rod with a SAM of biotin-modified 19-base oligonucleotide probe (5´-AAA GAT TAA TCC TGG G -3´,) for HIV-1. The electrode modification was characterized by Surface-Enhancement Raman Spectroscopy (SERS), cyclic voltammetry and the hybridization with the complementary oligonucleotide was monitored by impedimetric technique. SERS was used to confirm the linking of Biotin-DNA on the surface of the Au electrode. The coverage was 89% of the surface and a concentration of complementary oligonucleotides of 2.5 10− 12 molL−1 could be detected. Department of Analytical Chemistry University of Havana AIDS Research Laboratory (LISIDA) Department of Analytical Chemistry São Paulo State University (UNESP) São Carlos Institute of Chemistry Department of Chemistry and Molecular Physics University of São Paulo (USP) Department of Analytical Chemistry São Paulo State University (UNESP)

High photoluminescence efficiency, unusual NIR broadband and tunable emission are possible in erbium-doped and tantalum germanate glasses and nanostructured glass-ceramics. The chemical microenvironment around erbium ions and their influence on optical properties are dependent on the TaO6 clusters formation and tantalum perovskite-like bronze crystallization, which are strongly related to the tantalum oxide content and annealing. Erbium ions are preferably distributed close to tantalum-rich environment, providing an intense emission with minimized nonradiative processes and inhomogeneous broadband NIR emission with increasing site numbers. A more pronounced broadening in the nanocrystalline samples is due to the multi-sites of the tantalum perovskite-like bronze crystalline structure. Green/red tunable emission from up conversion processes was observed since the erbium ions occupy a chemical environment with low phonon energy in the tantalum germanate glass and with close neighbors in the tantalum germanate glass-ceramics. Accordingly, the highly tantalum germanate glasses and glass ceramics are promising for photonic applications in optical amplification, lighting and lasing, as well as for nonlinear optical applications and studies considering the perovskite-like bronze crystalline samples.

Spectroscopic and structural properties of Er 3+ :Yb 3+ :Tm 3+ triply doped Gd 2 O 3 nanocrystals were investigated. Materiais were heat treated at 800, 900, 1000 and 1100 oC for 4h, and heat treatment effect in the luminescence was discussed. The doping process with RE 3+ was effective on Gd 2 O 3 cubic phase, and structural parameters were determined for this phase. The morphology of the particles did not showed difference on shape and size, demonstrating the reproducibility of the synthesis methods. The luminescence at visible and infrared regions was studied when samples are excited at 980 nm. Materials present intense visible up-conversion and infrared emissions at 1550 nm, and Er 3+ emissions are favored in the materials, concluding that in Er 3+ :Yb 3+ :Tm 3+ triply doped materials the transfer between Yb 3+ and Er 3+ occurs preferentially. Materials due absorption at UV and IR regions can be availed in solar concentrators, as well as 1550nm for optical telecom applications in the C-band.

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

Phosphotellurite based glasses have interesting features such as low characteristic temperatures, high glass forming ability, high thermal stability against crystallization and a broad transparency window from ultraviolet (UV) to near-infrared (NIR), which makes them promising materials for photonic applications. In this work, phosphotellurite binary glasses, having a composition (100 - x)TeO2 - xBa(PO3)2 with x varying from 1 to 20 mol%, were synthesized by the conventional melt-quenching method in covered gold crucibles under air. Optical, physical and structural properties of the new glass samples were investigated by differential scanning calorimetry, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, linear optical absorption from UV to NIR, IR transmittance, and optical limiting experiments. Transparent glass-ceramics in the visible range were obtained for phosphotellurite samples containing 2, 4 and 6 mol% of Ba(PO3)2 and the phase crystallization was investigated through Rietveld analysis and transmission electron microscopy. The incorporation of Ba(PO3)2 into the TeO2 network drastically increases the thermal stability against devitrification and helps to shift the infrared multiphonon absorption edge to longer wavelengths. Nonlinear measurements performed with a picosecond laser at 532 nm indicate large effective nonlinear absorption coefficients for all samples. In summary, the dependence of the spectroscopic properties on the compositions of the samples revealed promising transparent glass and glass-ceramics for photonic applications.

Made available in DSpace on 2018-12-11T16:42:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-07-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Recent advances in glass chemistry have led to new multifunctional optical glasses of great technological importance. Glasses containing high amounts of antimony have been studied for use in nonlinear optics, near-infrared transmission, and as hosts for rare-earth ions in photonic devices. This work describes a luminescence study of Er3+ and Er3+/Yb3+ co-doping in a new SbPO4-GeO2 binary glass system. Near-infrared and visible up-conversion emissions were observed in the green and red regions, which are enhanced when the samples are co-doped with Yb3+. Near-infrared emissions have good quantum efficiency and full width half maximum of 61 nm. Visible up-conversion emissions are governed by two photons and described by excited state absorption, energy transfer and cross-relaxation processes. Institute of Chemistry São Paulo State University UNESP Department of Engineering Physics Polytechnique Montréal, P.O. Box 6079, Station Centre-ville Department of Chemistry São Carlos Federal University UFSCar Institute of Chemistry São Paulo State University UNESP FAPESP: 2010/20776-5 FAPESP: 2013/07793-6 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 2018-12-11T16:52:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-08-01 In this work, Er3+-containing fluoroindate glasses were synthesized by the conventional melt-quenching method varying Er3+ content from 0.1 to 7 mol%. The series of fluoroindate glass were investigated according to their luminescent properties. Upon excitation at 1550 nm, all glass samples showed green, red and near-infrared emissions centered at 550, 667 and 978 nm. Energy transfer upconversion (ETU) is the main mechanism responsible for the upconverted emissions and involves neighbour erbium ions. The highest near-infrared emission intensity at 1000 nm is observed for the glass sample containing 7 mol% of Er3+, which was used to evaluate the photovoltaic response of monocrystalline and monofacial silicon solar cell. This approach represents a beneficial strategy to stud spectral modification in upconverter materials. Institute of Chemistry São Paulo State University – UNESP São Carlos Institute of Chemistry University of São Paulo Institute of Chemistry São Paulo State University – UNESP

International audience; Glasses in the binary system (100-x)Pb2P2O7-xMoO3, with x = 10 – 80 mol%, were synthesized by conventional melt-quenching technique. Thermal analysis, linear optical absorption, refractive index measurements, Raman scattering and nonlinear (NL) optical experiments were performed to characterize the samples. The dependence of MoO3 content on thermal, structural and optical properties was investigated. Molybdenum oxide increases both the glass transitions temperature and thermal stability against devitrification up to 50mol% due to formations of P-O-Mo linkages and the glass network connectivity increases. The nonlinear optical properties were studied at 1064 nm and 532 nm with pulses of ≈17 ps. The NL refractive index measured was +10-19 m2/W at both wavelengths for samples with different relative concentrations of the constituent compounds. At 1064 nm we determined that the two-photon absorption coefficient, , is smaller than the minimum that we can measure (

Made available in DSpace on 2018-12-11T17:29:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Empresa Brasileira de Pesquisa Agropecuária Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Reliable gas sensors operating at room temperature are in demand for monitoring the environment for hazardous pollutants, such as ammonia (NH3) gas that may become toxic to humans and animals above a threshold concentration. In this paper we report on the combination of three materials, namely polyaniline (PANI), graphene oxide (GO) and zinc oxide (ZnO), to produce hybrid layer-by-layer (LbL) films used for sensing NH3 with impedance spectroscopy measurements. The deposition of tetralayered PANI/GO/PANI/ZnO LbL films was confirmed with UV–vis. absorption and Raman spectroscopies, while atomic force microscopy (AFM) served to investigate film morphology. Exposure of these LbL films to NH3 caused film roughness to vary, in an effect that depended on the number of tetralayers. Because of synergy in the materials properties, the films with 3 tetralayers were found to be the most adequate for detecting NH3 in the range from 25 ppm to 500 ppm with a response time of 30 s. These figures of merit are adequate for monitoring working environments regarding gas exposure, and highlight the usefulness of the control of film architecture provided by the LbL technique. National Laboratory for Nanotechnology in Agribusiness (LNNA) Embrapa Instrumentation Center for Exact Sciences and Technology Department of Chemistry Federal University of São Carlos (UFSCar) São Carlos Institute of Physics (IFSC) University of São Paulo (USP), P.O. Box 369 CCTS Federal University of São Carlos (UFSCar) Institute of Physics Gleb Wataghin Unicamp Institute of Chemistry São Paulo State University (UNESP) Institute of Chemistry São Paulo State University (UNESP) CNPq: 141894/2013-0 FAPESP: 2012/15543-7 FAPESP: 2012/23880-3 FAPESP: 2013/14262-7 FAPESP: 2014/16789-5 CNPq: 502391/2014-6

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 2018-11-27T16:00:01Z (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 2018-11-26T17:55:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-04-01. Added 1 bitstream(s) on 2021-07-15T14:32:23Z : No. of bitstreams: 1 S0100-40422016000300328.pdf: 5545326 bytes, checksum: 7e6829c8c6880aa7e049f21c77f3decb (MD5) 2015 is the Year of Light, according to UNESCO. Chemistry has a close relationship with light and one of the materials that allows such synergy is glass. Depending on the chemical composition of the glass, it is possible to achieve technological applications for the whole range of wavelengths extending from the region of the microwave to gamma rays. This diversity of applications opens a large range of research where chemistry, as a central science, overlaps the fields of physics, engineering, medicine, etc., generating a huge amount of knowledge and technological products used for humanity. This review article aimed at discussing some families of glasses, illustrating some applications. Due to the extension of the theme, and all points raised, we thought it would be good to divide the article into two parts. In the first part we focus on the properties of heavy metal oxide glasses, fluoride glasses and chalcogenide glasses. In the second part we emphasize the properties of glassy thin films prepared by sol-gel methodology and some applications, of both glasses as the films in photonics, and more attention was given to the nonlinear properties and uses of photonic fibers. Univ Estadual Paulista, Inst Quim, CP 355, BR-14800060 Araraquara, SP, Brazil Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Quim, BR-14040901 Ribeirao Preto, SP, Brazil Univ Fed Alfenas, Inst Ciencia & Tecnol, Campus Pocos De Caldas, BR-37715400 Pocos De Caldas, MG, Brazil Univ Presbiteriana Mackenzie, BR-01302907 Sao Paulo, SP, Brazil Univ Sao Paulo, Inst Fis Sao Carlos, BR-13566590 Sao Carlos, SP, Brazil Univ Fed Pernambuco, Dept Quim, BR-50740560 Recife, PE, Brazil Univ Laval, Ctr Opt Photon & Laser, Quebec City, PQ G1K 7P4, Canada Univ Estadual Paulista, Inst Quim, CP 355, BR-14800060 Araraquara, SP, Brazil

Made available in DSpace on 2018-11-26T17:55:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-04-01. Added 1 bitstream(s) on 2021-07-15T14:32:24Z : No. of bitstreams: 1 S0100-40422016000300340.pdf: 4072751 bytes, checksum: 635ad996b95ebc83868fbdbb081d0bae (MD5) In this second part it will be discussed some photonic applications of glassy and glass ceramic thin films which can be used as planar waveguides. Some photonic applications require certain specifications of glass, which can be quantified by studying the nonlinear optical properties of the materials. Therefore, a brief introduction of these phenomena is discussed, as well as the use of femtosecond lasers to manipulate the composition or for the preparation of waveguides into glasses. Finally, the article will address a brief introduction on microstructured optical fibers and commercial application prospects for these devices. Univ Estadual Paulista, Inst Quim, CP 355, BR-14800060 Araraquara, SP, Brazil Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Quim, BR-14040901 Ribeirao Preto, SP, Brazil Univ Fed Alfenas, Inst Ciencia & Tecnol, Campus Pocos De Caldas, BR-37715400 Pocos De Caldas, MG, Brazil Univ Presbiteriana Mackenzie, BR-01302907 Sao Paulo, SP, Brazil Univ Sao Paulo, Inst Fis Sao Carlos, BR-13566590 Sao Carlos, SP, Brazil Univ Fed Pernambuco, Dept Quim, BR-50740560 Recife, PE, Brazil Univ Laval, Ctr Opt Photon & Laser, Quebec City, PQ G1K 7P4, Canada Univ Estadual Paulista, Inst Quim, CP 355, BR-14800060 Araraquara, SP, Brazil

Infrared photoluminescence properties are investigated for Pr3+ containing fluoroindate glasses with formula (mol% compositions) (99-x)[ 40InF(3)-20SrF(2)-20BaF(2)-20ZnF(2)]:xPrF(3) (x= 0.1, 0.2, 0.5, 1.0 and 2.0 mol%). Different mechanisms of population and quenching for Pr3+ D-1(2) and (1)G(4) levels are shown from photoluminescence (PL), photoluminescence excitation (PLE) and decay time values. Cross relaxation processes are put in evidence in different ways for the population of excited levels as a function of the Pr3+ concentration, depending on the excitation wavelength. Different dependences on Pr3+ concentrations are observed for D-1(2) and (1)G(4) levels.