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Made available in DSpace on 2022-05-01T08:44:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) In this research, the influence of synthesis process under Te4+ ion formation in lithium tellurite glass was investigated based in their optical and structural characteristics. The same 80TeO2 + 20Li2O nominal composition (in mol%) was used to prepare glasses with different synthesis temperatures (Ts = 600, 700, 750, 800 and 850 °C) and atmospheres (room, oxygen and argon). The study was based in the investigation of the UV–Vis absorption spectroscopy, Raman spectroscopy, photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. The linear refractive index was measured in function of the wavelength ranging all the visible region. The results indicate that Te4+ concentration into the glass is strongly dependent on both synthesis temperature and atmosphere. A more intense emission is observed in glasses prepared in oxygen atmosphere and in the 750–800 °C temperature range. Programa de Pós-Graduação em Recursos Naturais - PGRN Universidade Estadual de Mato Grosso do Sul - UEMS Grupo Vidros e Cerâmicas Universidade Estadual Paulista - UNESP Instituto de Física de São Carlos - IFSC Universidade de São Paulo - USP Grupo Vidros e Cerâmicas Universidade Estadual Paulista - UNESP CAPES: 00.889.834/0001-08

Near-near infrared (N-NIR) Thermal Lens Spectroscopy (TLS) was used to monitor the transesterification reaction during biodiesel production. Fifteen aliquots were extracted from the reaction during 20 min and their thermo-optical properties were measured as a function of the reaction time. A spectroscopic investigation was performed between 855 and 990 nm to identify overtone absorptions bands (markers) to monitor the chemical reaction. The results show that the OH absorption overtone (∼970 nm) from alcohol, which is used in the reaction, is the most appropriated marker to monitor the biodiesel production. The time dependence of the thermo-optical parameter A(dn/dQ), which is the product between the absorption coefficient (A) and the refractive index dependence with the sample deposited heat (dn/dQ), exhibits a very good correlation with the ester production measured by chromatography. Besides, the measured thermal diffusivity values as function of reaction time indicates a strong dependence with the viscosity of the aliquots. It is possible to conclude that the used TLS in the N-NIR region contributes to the optimization of biodiesel production process by indicating the best time to stop the reaction.

Nano-catalysts based on ZnO-Ca x% (with x = 0, 0.1, 0.3, 0.5, 0.7, and 1.0 mol % Ca2+) were synthesized with a bio-friendly adaptation of the sol-gel method using gelatin as template. These materials were characterized by Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Micro-Raman, transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 physisorption, photoacoustic absorption spectroscopy (PAS), and photoluminescence spectroscopy (PL). The Raman results indicated that the signal, attributed to an E1(LO) mode at 580 cm−1, was characteristic of oxygen vacancies that decreased with the increased Ca2+ content in doped oxides. This agreed with the PL results, which showed that the green emission centered at 510 nm and attributable to structural defects in ZnO decreased for Ca-doped ZnO. Our oxides are constituted by nanoparticles with rod-like and spherical morphologies. All the nano-catalysts exhibited the band gap characteristics of semiconductor materials around 3.0 eV. ZnO-Ca 1.0% exhibited the best photocatalytic performance for degradation of Methyl Orange (MO) model dye, degrading about 82% after 240 min of UV–Vis irradiation at pH 7.0. The reaction mechanism was influenced by hydroxyl ( OH) and superoxide (O2 -) radicals and mainly by active holes (h+). This doped oxide also demonstrated efficiency in wastewater disinfection against heterotrophic bacteria and total coliforms, exhibiting a potential use as an antimicrobial agent for the treatment of hospital wastewater. Furthermore, our nanoparticles did not show significant cytotoxic effects on L929 fibroblast cells.

In this report, Pr3+-doped calcium aluminosilicate (CAS) glasses were synthesized and their spectroscopic properties investigated. The present subject was motivated by the red emission of the Pr3+ ion that can be combined with the green-yellow emission of other luminescent ions like Ce3+ or Eu2+ for white light generation. This combination of materials has been required since commercial diode devices for white lighting exhibit low color rendering index (CRI) and high correlated color temperature (CCT) due to their low emission intensity in the red region. The results showed that when Pr3+-doped CAS glasses are excited at 445 nm, red and green broadband emissions (FWHM ∼ 1300 and 1800 cm−1, respectively) with a strong dependence on the ion concentration can be observed. The (x, y) coordinates in the CIE-1931 chromaticity diagram changed from (0.61, 0.36) to (0.47, 0.41) when the Pr3+ concentration varied from 0.2 to 2.0 wt.%, what was explained in terms of cross-relaxation mechanisms between Pr3+ ions. The luminescence quantum yield (QY), in the visible range from 450 to 800 nm, of the Pr3+-doped CAS glass was determined by an integrating sphere as 0.37, which is a relatively high value for Pr3+-doped glasses. At high Pr3+ concentrations, the studied system is appropriate to be combined with other green-yellow phosphor material for white light generation.

Background absorption has been studied for an YLF:10%Yb3+ crystal at different intensities at room temperature. The cooling efficiency was measured by both the DLT (Differential Luminescence Thermometry) and TLS (Thermal Lens Spectroscopy) methods. Results show that background and coolant absorption saturate differently at room temperature. A cw Ti:sapphire pump beam was tuned from 920 nm to 1040 nm with an intensity range from 100 W/cm2 to 20,000 W/cm2. Changes of temperature and thermal strength were measured by DLT and TLS methods, respectively. The cooling efficiencies with these approaches at different wavelengths were then compared based on theoretical fits to the experimental results. The cooling efficiency at 1000 nm was found to be independent of pump intensity. There, the saturation of intensity of background absorption had the same value as that of Ytterbium. The cooling efficiency below 1000 nm dropped at elevated intensity. In this range, Ytterbium absorption saturated easily, reducing the cooling ion absorption, while the absorption of background impurities did not saturate as much as Ytterbium. Consequently the cooling efficiency was lowered. For wavelengths above 1000 nm, increases in the pump intensity led to improved cooling efficiency. In this range, background absorption saturated more easily than absorption of coolant ions and parasitic heating was reduced, leading to higher cooling efficiency. Thus we have devised a method of measuring differential absorption saturation and determined its effect on laser cooling at room temperature. Saturation effects of this kind have important consequences in the heat equation for radiation-balanced lasers.

Al2O3-Zn x% NPs, with x = 0, 1, 3, 5 or 10 mol% Zn2+ were synthesized by a modified sol–gel method. The influence of the insertion of Zn2+ dopant on the crystal lattice, morphology, optical and cytotoxic properties of Al2O3 was investigated. Rietveld refinement applied to DRX data revealed that the oxides are constituted by four crystalline phases: α-Al2O3, θ-Al2O3, δ-Al2O3 and α-Al2O3(*), and that the doping promoted changes in unit cell volume for all the crystalline phases. Raman signals indicated that the insertion of Zn2+ caused changes in the vibrations of bonds Al–O, mainly in tetrahedral sites of transition phases of Al2O3, which are preferentially occupied by Zn ions. The oxides exhibited photoluminescence emission in the visible and near-infrared region, but Al2O3-Zn 10% showed increased emission intensity in the visible region. The nanoparticles with spherical and elongated morphologies did not exhibit cytotoxic effects on L929 fibroblast cells. Zn-doped Al2O3 nanoparticles were synthesized by a modified sol-gel method. The influence of the insertion of Zn2+ dopant on the crystal lattice, morphology, optical and cytotoxic properties of Al2O3 was investigated.

Photoluminescence quantum yields denote a critical variable to characterise a fluorophore and its potential performance. Their determination, by means of methodologies employing reference standard materials, inevitably leads to large uncertainties. In response to this, herein we report for the first time an innovative and elegant methodology, whereby the use of neat solvent/reference material required by thermal lens approaches is eliminated by coupling it to photoluminescence spectroscopy, allowing for the discrimination between materials with similar photoluminescence quantum yields. To achieve this, both radiative and non-radiative transitions are simultaneously measured using a photoluminescence spectrometer coupled to a multiwavelength thermal lens spectroscopy setup in a mode-mismatched dual-beam configuration, respectively. The absorption factor independent ratio of the thermal lens and photoluminescence signals can then be used to determine the fluorescence quantum yield both accurately and precisely. We validated our reported method using rhodamine 6G and further applied it to three novel structurally related diketopyrrolopyrrole based materials, which, in contrast to results obtained by other methods, unveiled significant differences in their photoluminescence quantum yields.

Made available in DSpace on 2018-12-11T16:51:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-06-01 Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul In this work, a lithium tellurite glass (80TeO2− 20Li2O, in mol%) was synthesized and its optical properties were analyzed. This glass matrix has been extensively studied, mainly due to its highly nonlinear optical properties, but there have been no reports concerning its luminescence properties. To the best of our knowledge, this is the first observation of visible emission related to Te4+ centers in a lithium tellurite glass. A broad and intense emission band was centered at 650 nm and there was a broad excitation band in the UV–Vis region. The emission lifetime at room temperature was approximately 7.0 ± 0.2 µs and the fluorescence quantum efficiency was 63 ± 6%. These characteristics indicated that the system consisting of Te4+ centers in lithium tellurite glass is a good candidate as a phosphor material for various applications. Grupo de Espectroscopia Óptica e Fototérmica Universidade Estadual de Mato Grosso do Sul, C. P. 351 Grupo de Pesquisa de Materiais Fotônicos e Energia Renovável Universidade Federal da Grande Dourados Grupo Vidros e Cerâmicas Faculdade de Engenharia de Ilha Solteira – UNESP Laboratório de Laser e Aplicações Universidade de São Paulo, C. P. 369 Grupo Vidros e Cerâmicas Faculdade de Engenharia de Ilha Solteira – UNESP Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul: 23/200.735/2014

Very few devices are capable to measure temperature with high precision and sensitive, mainly in the micro and nanoscale. It is known that for biological applications it is required high sensitivity devices in a short temperature range (288–323 K). Recent reports are proposing the use of ratiometric thermometers based in the luminescence of trivalent lanthanide ions. In this paper, the ratiometric thermometer characteristic was investigated in an alumino-phosphate glass doped with Eu2O3. The studied temperature range was 288 – 333 K, and the material presents high sensitivity values (1.25–1.68% per K). The luminescence of Eu3+-doped alumino-phosphate glass does no present losses by energy transfer mechanism in this temperature range, making a quick predicable thermometric parameter by use of ratio between the integrated intensities of 5D0 → 7F2 and 5D0 → 7F0 transitions, respectively. Both excitation and emission are in wavelengths not strongly absorbed by living tissues, becoming promising material to applications in the laboratories scale, as the temperature measurements of cell cultures, and monitoring of tissues that does not require high penetration of excitation wavelengths.

A dual-beam mode-mismatched configuration of the Thermal Lens (TL) technique was applied to characterize biodiesel, diesel and diesel/biodiesel blends. The excitation was performed using a tunable laser in the near-near infrared region in order to assess overtones and combination bands of the vibration modes. The thermo-optical properties of the fuels were also determined. The results showed that the biodiesel contents in diesel/biodiesel blends can be monitored with this technique, by excitation the third overtone of the C–H (4ν(C–H)) bond stretching vibration at 916 nm. Both the amplitude of the photothermal signal and thermal diffusivity are important parameters to quantify the biodiesel content in diesel/biodiesel blends.

ZnO-Al x% nanoparticles (NPs), with x = 0, 1, 3, 5 or 10 mol% Al3+, were synthesized by a modified sol-gel method. The effects of Al3+ content on the structure, morphology and optical properties of Al-doped ZnO were investigated by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, photoacoustic absorption spectroscopy (PAS), photoluminescence spectroscopy (PL) and specific surface area determination. A single crystalline phase characteristic of ZnO with wurtzite structure was detected for all synthesized oxides. With increasing dopant content, the average crystallite size of the NPs decreased from 25 to 7 nm. ZnO-Al x% NPs exhibited enhanced optical properties with the absorption slightly shifted to the visible region and with the band gap energy (Eg) decreased from 3.12 (undoped ZnO) to 2.95 eV (ZnO-Al 3%). Undoped ZnO showed intense PL above 430 nm, which was considerably decreased with the insertion of Al3+. Despite the increase of the surface area with Al3+ doping of ZnO NPs, its catalytic activity in the decomposition reaction of Congo red showed a decrease with doping. Research has shown that ZnO NPs can selectively target and kill cancer cells and that its cytotoxicity is dependent of the concentration. The doping can be a method of shape the cytotoxicity of ZnO NPs and their optical and photocatalytic properties. In-vitro cytotoxicity studies showed that both undoped ZnO and Al-doped ZnO NPs synthesized were highly cytotoxic for fibroblast cells, suggesting that these nanomaterials could be promising anticancer agents.

SUMMARY The purpose of this study was to evaluate the chemical bonds of a self-etch 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) adhesive to natural noncarious cervical lesions (NCCLs) and compare them with those occurring in sclerotic dentin in artificially prepared defects (APDs). Four human teeth with natural NCCLs on the buccal surface were selected. Artificial defects matching the natural lesions were prepared on the lingual surface of the same teeth serving as control. Micro-Raman (MR) spectroscopy was used to quantify mineral content in natural NCCLs and in APDs. Fourier transform infrared-photoacoustic spectroscopy (FTIR-PAS) readouts were taken before and after adhesive application to analyze the protein matrix/mineral (M:M) ratio and chemical interactions between 10-MDP adhesive and dentin. The MR and FTIR-PAS spectra collected from natural NCCLs demonstrated a larger area of the band (961 cm−1, PO4) and lower M:M ratio, respectively, characterizing a hypermineralized dentin, compared with APDs. FTIR-PAS demonstrated emergence of a peak (1179 cm−1, P=O) in spectra after adhesive treatment, demonstrating a more intense chemical interaction in natural NCCLs. The results demonstrated that chemical bonding of 10-MDP adhesive to natural NCCLs is more intense, due to the hypermineralized surface, and suggest that it is unnecessary to remove the hypermineralized layer with burs, as this may decrease the chemical bonding potential of 10-MDP.

International audience; In this work Thermal Lens Spectroscopy (TLS) is used for sensitive characterization of absorption in optical materials with particular application for solid-state laser cooling (optical refrigeration). TLS is used to characterize key parameters involved in 4f-4f transition in Yb3+:YLF and 4f-5d transition in Ce3+:YAG systems. The results confirm the excellent laser cooling results found in previous works on Yb3+:YLF crystal. In addition, although no cooling effect was observed in Ce3+:YAG sample, the TLS showed that this material exhibits promising characteristics towards laser cooling applications, such as high external quantum efficiency (>92%), and low parasitic background absorption of (1.2 ± 0.2) × 10−4 cm−1 at 885 nm. The key mechanisms that appear to inhibit net cooling in Ce3+:YAG are attributed to the intrinsic excited state absorption and/or 4f-4f transitions between the two lowest levels of Ce3+. This investigation was turned possible due to the high sensitivity of TLS for very low absorptions.

Made available in DSpace on 2019-10-06T16:57:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-04-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul Te4+/Yb3+ co-doped 80%TeO2–20%Li2O glasses (amounts in mol%) were prepared by the conventional melt-quenching method in an ambient atmosphere, in order to investigate their optical characteristics for application in solar cells. An efficient near-infrared down-conversion mechanism was observed in these samples, involving the emission of two near infrared photons (at around 978 nm) after the absorption of one photon in the ultraviolet-blue region. This effect occurred by means of a process of cooperative energy transfer (CET) from Te4+ to Yb3+ ions. The CET efficiency (ηCET) was calculated from radiative transitions (lifetime) and also by a new method, developed in this work, based on rate equations quantifying the non-radiative transitions (thermal effect) involved in the system. The two methods showed very good agreement, with ηCET between 82 and 100% obtained for the sample prepared using a higher Yb3+ concentration (4 mol%). The results suggested that these tellurite materials could have potential applications in improving the efficiency of silicon-based solar cells. Grupo de Espectroscopia Óptica e Fototérmica Universidade Estadual de Mato Grosso do Sul, C.P. 351 Grupo Vidros e Cerâmicas Faculdade de Engenharia de Ilha Solteira – UNESP Laboratório de Laser e Aplicações Universidade de São Paulo Grupo Vidros e Cerâmicas Faculdade de Engenharia de Ilha Solteira – UNESP FAPESP: 2013/19747-9 Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul: 23/200.735/2014 Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul: 59/300.031/2015

The objective of this study was to evaluate the efficiency of Laser-Induced Breakdown Spectroscopy (LIBS) to detect the presence of bioaccumulated Fe and Pb in scales of Salminus brasiliensis and Prochilodus lineatus, and to compare the results from this technique with those obtained using the conventional atomic absorption spectrometry technique. The study used fish collected in the Amambai River, Upper Parana River, Brazil. The LIBS technique detected the presence of Fe in S. brasiliensis scales and Fe and Pb in P. lineatus scales on different regions. Using atomic absorption spectrometry, we verified a significant difference in Fe concentration in scales between the species analyzed, with a higher concentration in S. brasiliensis than in P. lineatus (p = 0.0004). Pb was not detected using atomic absorption spectrometry in either species because the concentration of this element was below the limit of detection of this technique. The LIBS technique was efficient in detecting Fe and Pb in scales of the two species analyzed, proving to be a promising tool for environmental monitoring.

The dual-beam mode-mismatched thermal lens (TL) technique in the near infrared (NIR) and visible spectral regions, as well as mid-infrared (MIR) absorption conventional spectroscopy, were applied to carry out a full spectroscopic characterization of chloroform, dichloromethane, methanol, and ethanol. Absorption spectra due to overtones and combination bands of C−H and O−H bond stretching were acquired in a wide spectral region (870–1040 nm) using a tunable Ti3+:sapphire laser, enabling determination of the anharmonicity constants (χ) and dissociation energies. Moreover, the solvents thermal diffusivities were obtained and absorption coefficients ~10−4 cm−1 or lower were found in some spectral transparence windows in chloroform and dichloromethane. The TL technique proved to be a very sensitive methodology able to determine of overtones with low absorption coefficients.

International audience; In this report, Ti3+, 4+/Eu2+, 3+ co-doped OH− free low silica calcium aluminosilicate glasses (LSCAS) were synthesized and their optical properties investigated aiming applications as phosphors for white light generation. This research explores the possibility of combining the broad emission bands in the visible of these glasses co-doped with Ti3+,4+/Eu2+ ions with those in the red emitted by Eu3+, in addition to the high luminescence quantum yield they present. The excitation and emission results show that exciting the samples at 300 nm, a broad emission band is generated, embracing very well the visible region. The emission spectra were analyzed by (x-y) CIE-1931 chromaticity diagram and the color rendering index (CRI) presented Ra values up to 80, with the correlate color temperature (CCT) varying from 4995 to 6609 K. The luminescence quantum yield determined by Thermal Lens Spectroscopy showed values of 38 and 42% for the samples with (in wt%) 0.1Eu2O3-2.0TiO2 and 0.5Eu2O3-2.0TiO2, respectively. Finally, the energy transfer processes between these luminescent ions were discussed, highlighting the potential of the Eu–Ti LSCAS glasses as candidates for the development of devices for white light generation.

Films and fibers of PMMA/ZnO nanocomposites (100/0, 99/01, 97/03, 95/05, 90/10, and 85/15 wt.%) were produced by casting and electrospinning, respectively. Their structural, thermal, and optical properties were investigated by XRD, SEM, TGA, PAS, and PL. The incorporation of ZnO NPs reduced the diameter of PMMA fibers and the presence of beads. The surfaces of the fibers exhibited greater hydrophobicity, compared to the films, with contact angles of around 120° and 94°, respectively. PMMA films containing ZnO exhibited higher thermal stability than the pure polymer, while the corresponding fibers did not show any changes in thermal stability. The dispersion of the ZnO NPs at the surface and in the bulk of the nanocomposites appeared to be relatively homogeneous. ZnO improved the optical properties of the PMMA, with an intense absorption band near 370 nm observed for all the nanocomposites, which also exhibited luminescence with emission in the near-UV region, both attributed to ZnO. Biological tests demonstrated that fibers and films with up to 1% of ZnO exhibited good performance in the proliferation of fibroblast cells, indicating their potential for applications in tissue engineering. The fibers provided higher cell viability than the films, presumably due to their greater surface area and/or more suitable surface morphology. Nanocomposites with 15% ZnO inhibited cell proliferation, due to the cytotoxicity of the ZnO NPs. Although several applications of PMMA have been suggested by biomedical researchers, until now there have been no reports on the specific uses of fibers and films of PMMA/ZnO nanocomposites as scaffolds for fibroblast cell proliferation.

Via this article, the optical features and ionizing radiation shielding competences of xTeO2 − (100 − x)Li2O, where x = 70 to 95 in steps of 5 mol% glasses to be used in nuclear shielding areas were evaluated. These glasses were coded as TL05-TL30 according to x value. Refractive index (noptical), molar (refractivity (Rmolar) and polarizability (αmolar)), reflection loss (Rloss), Optical transmission factor (Toptical), dielectric constants (estatic and eoptical), and metallization criterion (Mcriterion) of TL-glasses have been investigated. The mass (MAC) and linear (LAC) attenuation coefficients were examined via Geant4 toolkit simulation code and verified via Phy-X/PSD. Results revealed that the (noptical) was increased from 2.24 to 2.30. The Rmolar varied from 17.432 to 19.122 (cm3/mol), the αmolar increased from 6.917 to 7.588 (×10−24 cm3), and the (estatic) varied from 5.022 to 5.308. The TL30 glasses possess the lowest values, while TL05 found to possess the maximum MAC values. The MAC values were in the order of (MAC)TL05 > (MAC)TL10 > (MAC)TL15 > (MAC)TL20 > (MAC)TL25 > (MAC)TL30 which highlights the role of Te addition to the glass matrix to enhance the shielding capacity of theses glasses. The HVL of these TL-glasses can be arranged in reverse order with MAC, where (HVL)TL30 > (HVL)TL25 > (HVL)TL20 > (HVL)TL15 > (HVL)TL10 > (HVL)TL05. The highest Zeff values are found at the low photon energy and ranged from 48.91 to 49.47 at 0.015 MeV for TL30 and TL05, respectively. While at 15 MeV, Zeff values are found 28.42 and 32.97 for TL30 and TL05, respectively. The TL05 glass with the highest TeO2 ratio has the largest Zeq values. The TL05 glass owns very low values of energy absorption buildup factor (EABF) and exposure buildup factor (EBF). This indicates that the TL05 sample was more effective than other samples in absorbing gamma radiation. One can conclude that the investigated TL-glasses have high ability to attenuate gamma-ray, especially TL05 glass sample. Therefore, these glasses can be applied in the field of nuclear protection.

In this work, thermal lens spectroscopy was performed simultaneously with photoluminescence experiments for determining the absolute external quantum efficiency (EQE) of luminescent materials. The procedure involved measurements of nonradiative (heat) and radiative (photon) emission rates after excitation of the material with a tunable laser. The main advantage of this combined methodology was that the amount of light absorbed by the sample was not required for EQE determination, which minimized the experimental error. In order to validate the methodology, the well-known Ce3+:YAG crystal was used for EQE determination, with the value obtained being in agreement with previous experiments. This shows that the method is a promising tool for accurate measurements of the EQE for materials with a single excited emission state.

At the present time there is no doubt that almost every country is experiencing a revolutionary change in the used devices for artificial lighting whether for public, for domestic or for work place illumination. This movement is taking place towards the substitution of fluorescent lamps to LED-phosphor based devices under the justification of reduction in energy consumption and mitigation of the contamination of environment produced by the mercury of fluorescent lamps. In this aspect, despite of the great effort of worldwide scientists to obtain a white lighting source with the emitting spectrum similar to that of the sunlight, it is recognized that there is still a challenge to be faced of getting luminescent materials with broad band excitation in the UV–Vis regions and large emission in the visible in order to allow tunable white lighting generation. Motivated by this interest, in this paper, Eu2+,3+/Pr3+ co-doped calcium aluminosilicate glasses were synthesized and spectroscopically investigated aiming at the development of smart white lighting devices. A prototype was developed to study the sample with excitation at 445 nm light emission diode (LED). The results indicate high color rendering index (CRI Ra ∼92–95) and tunable correlated color temperature (CCT from 5700 to 6600 K), covering the whole spectral daylight range. By using a second 405 nm LED together with the 445 nm one, the calculated Du’v’ values are suitable for indoor illumination. In this configuration, by adjusting the LEDs intensities it is possible to tune the CCT close to the white lighting region with CRI Ra nearly 95. These characteristics demonstrate that the Eu2+,3+/Pr3+ co-doped OH− calcium aluminosilicate glass is a strong candidate for smart white lighting with LEDs.

We report the first observation of laser cooling in Yb3+:KYW and validate the results by comparison with experiments in the well-studied material Yb3+:YAG. Radiation from a single-mode Ti:Al2O3 laser was used to achieve cooling of 1.5 K/W in 1% Yb:KYW at 1025 nm, comparing well with the reference material 3% Yb:YAG which cooled by 3.5 K/W at 1030 nm under open lab conditions. Experimental results for KYW crystals mounted on aerogels and doped with 1-20% Yb were in excellent agreement with the theoretical dependence of cooling power on the Yb absorption spectrum. Elimination of thermal conduction through the sample support structure was found to permit the attainment of lower temperatures and to simplify modeling of radiation balance conditions in self-cooled lasers with longitudinal thermal gradients. Contrary to the notion that more coolant ions yield higher cooling power, concentrations of Yb over 1% caused re-absorption of luminescence in KYW crystals, leading to a progressive red shift in the optimal cooling wavelength and the prevention of laser cooling altogether in a 20% sample at room temperature. The prospect of attaining radiation-balanced lasing in commercially-available tungstate crystals is evaluated.

In this work, the time dependence of the crude glycerol production was obtained experimentally in different reactions by fluorescence spectroscopy, and the curves were fitted by a new mathematical model, derived from rate equations, in order to elucidate the behavior of the compounds involved in transesterification reactions, including the speed and ester yield. The values were validated by comparison with the results of analyses performed using gas chromatography with flame ionization detection. The fitting of the glycerol fluorescence signal as a function of time by the proposed theoretical model was shown to be highly suitable for indicating the time at which the reaction should be stopped, hence minimizing costs and the time required for biodiesel production.

SUMMARY Objectives: To characterize the chemical interactions and analyze the interface of adhesive systems containing 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) and N-methacryloyl glycine (methacrylamide) functional monomers with the dentin in noncarious cervical lesions (NCCLs) compared with artificial defects (ADs). Methods and Materials: Twenty human teeth with natural NCCLs on the buccal surface were used. Class V cavities, similar to NCCLs, were created on the lingual surface to serve as controls. Teeth were randomly allocated to two groups according to the functional monomer in the adhesive (N=10): G1, 10-MDP; and G2, methacrylamide. NCCLs and ADs were characterized by their mineral composition (MC) and degree of demineralization (DD) using micro-Raman spectroscopy, adhesive/dentin chemical interactions (CIs) were assessed with infrared photoacoustic spectroscopy, and interface morphology was evaluated with scanning electron and light microscopy. MC, CI, and DD data were submitted to Shapiro-Wilk and Student t-tests (p Results: Compared with ADs, dentin in NCCLs was hypermineralized (p Conclusions: Results suggest that the G1 adhesive could be applied directly on the superficial sclerotic layer in NCCLs. In contrast, previous cavity preparation should be conducted to improve the micromechanical interaction of G2 with the dentin.

During beer production, the mashing process is fundamental for extraction of the main sugars from the starch. The quantification of these fermentable sugars during the process provides a measure of the alcoholic content of the final beer. Therefore, monitoring of the sugar composition during beer production is very important for obtaining a quality product. This paper demonstrates the potential of white light interferometry (WLI) for monitoring the extraction of sugars in different mashing processes, by observing the refractive index of the mixture. All the mashings presented linear increases of the refractive index during the temperature steps, which were influenced by the concentrations of sugars produced in each step. Cauchy parameters obtained by refractive index interpretation showed the influence of carbohydrates on absorption in the infrared region, and amino acids on absorption in the ultraviolet region. Strong correlation was obtained between the refractive index and °Bx values, indicating that the WLI technique is a potential analytical method for monitoring the mashing process during beer production.

We report the anomalous dispersion and group refractive index (ng) of the Er3+: tellurite glass measured by Windowed Fourier Transform from interferometric measurements and compared with the dispersion calculated from absorption spectra by known Kramers-Kroing relations.

The relationship between emission tunability and the local environment of europium ions in OH−-free calcium aluminosilicate glasses was investigated, focusing on the development of devices for artificial lighting. Significant conversion of Eu3+ to Eu2+ was obtained by means of melting the glasses under a vacuum atmosphere and controlling the silica content, resulting in broad, intense, and tunable luminescence ranging from blue to red. Electron spin resonance and X-ray absorption near edge structure measurements enabled correlation of the luminescence behavior of the material with the Eu2+/Eu3+ concentration ratio and changes in the surrounding ions' crystal field. The coordinates of the CIE 1931 chromaticity diagram were calculated from the spectra, and the contour maps showed that the light emitted from Eu2+ presented broad bands and enhanced color tuning, ranging from reddish-orange to blue. The results showed that these Eu doped glasses can be used for tunable white lighting by combining matrix composition and the adjustment of the pumping wavelength.

In this work we report the observed downconversion (DC) mechanism in Er 3+ /Yb 3+ -codoped tellurite glasses (in mol%, 80TeO 2 –10Li 2 O–10TiO 2 ). The samples were synthesized by the conventional melt-quenching method and then studied using optical spectroscopy and thermal lens spectroscopy (TLS). These characterizations enabled investigation of the radiative and nonradiative processes involved in energy transfer from erbium to ytterbium. The visible Er 3+ fluorescence intensities decreased as a function of the Yb 3+ concentration, and there was a corresponding increase in the ytterbium emission at around 980 nm. Simultaneously, there was a reduction in the heat-generated due nonradiative decays (~21%) when ytterbium was added. This temperature change was measured by TLS measurements and the results corroborate with the indicated by spectroscopic interpretation.

Mashing is an enzymatic procedure for the extraction of sugars from malt. It has strong temperature dependence, so monitoring the sugar production is very important for optimization of the brewing process. In this work, Fourier transform infrared spectroscopy (FTIR) was used to monitor three different mashing programs. These all presented high concentrations of maltose and dextrin, enabling their differentiation according to the FTIR absorption bands at 991 and 1022 cm−1, characteristic of maltose and dextrin, respectively. The absorption intensities of these bands were used to monitor the concentrations of the compounds during mashing, and the values were compared to HPLC data. Multivariate analysis of variance was applied to the FTIR absorption intensities in order to separate groups corresponding to the temperature steps of each mashing program. The results demonstrated that infrared absorption offers an alternative to the HPLC method for monitoring the mashing process.

This work reports on the energy transfer efficiency for Nd3+/Yb3+ co-doped tellurite glasses (80TO2-20WO3, in mol%,). The correlation between Yb3+ ion concentration and the downconversion mechanism was investigated using optical and thermal lens spectroscopies, which enabled investigation of the radiative and nonradiative processes, respectively, involved in energy transfer from neodymium to ytterbium. The Nd3+ near-infrared fluorescence disappeared almost entirely when the maximum concentration of Yb3+ ions (4 mol%) was doped into the host. In contrast, there was a corresponding increase in the ytterbium emission at around 980 nm. When ytterbium was added, there was also a simultaneous reduction in the amount of heat generated by the sample due to a reduction in the nonradiative decay rate, corroborating the suspected high energy transfer efficiency of Nd3+→Yb3+. The results indicate that tungsten-tellurite glasses may be of potential use in solar cells for matching the solar emission spectrum to the semiconductor cell.

Made available in DSpace on 2019-10-06T17:19:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-11-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul Lithium tellurite glasses with xTeO2 + (100 − x)Li2O nominal composition, where x = 95, 90, 85, 80, 75 and 70 mol%, have been prepared to investigate the dependence of the Te4+ emission as a function of the lithium modifier. Optical and structural properties of the glasses were explored by using UV–Vis absorption, photoluminescence and photoluminescence excitation spectroscopies, photoluminescence lifetime and Raman spectroscopy. Besides, the influence of Li2O in the glass structure was verified by density, glass transition temperature, thermal stability, glass-forming tendency, optical band edge and the number of non-bridging oxygen. The results support there is a good correlation between the glass structure and the Te4+ center concentration: the Li2O content contributes to increase the Te4+ in the glass structure. Grupo Vidros e Cerâmicas Universidade Estadual Paulista – UNESP Grupo de Espectroscopia Óptica e Fototérmica Universidade Estadual de Mato Grosso do Sul Laboratório de Laser e Aplicações Universidade de São Paulo Physics Department Faculty of Science Menofia University Grupo Vidros e Cerâmicas Universidade Estadual Paulista – UNESP Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul: 59/300.031/2015

Erbium doped tellurite glasses (TeO 2 + Li 2 O + TiO 2 ) were prepared by conventional melt-quenching method to study the influence of the Er 3+ concentration on the luminescence quantum efficiency ( η ) at 1.5 μm. Absorption and luminescence data were used to characterize the samples, and the η parameter was measured using the well-known thermal lens spectroscopy. For low Er 3+ concentration, the measured values are around 76%, and the concentration behavior of η shows Er–Er and Er–OH − interactions, which agreed with the measured lifetime values.

Ni0.04Zn0.96O and Fe0.03Zn0.97O with average diameter of 23 and 19 nm, respectively, have been syn- thesized by a modified solegel method to be used in the preparation of (100 � x)/x poly(vinyl alcohol)/ oxide nanocomposite films, with x ¼ 0,1, 3 and 5 (in wt.%). A 125 W-Hg vapor lamp with emission above 254 nmwas used to irradiate PVA/Ni0.04Zn0.96O and PVA/Fe0.03Zn0.97O films. The effect on their structural, thermal, morphological and optical properties was studied by TG, DSC, DRX, AFM, UVevis and PL spectrophotometry. The Ni0.04Zn0.96O addition on PVA films decreases the thermal stability of the polymer in inert and in oxidative atmosphere. In contrast, the Fe0.03Zn0.97O presence in the PVA films seems to increase the thermal stability of the polymer. The characteristic peak of the crystalline phase of PVA and wurtzite phase of the zinc oxide were identified through X-ray diffraction in both films. The crystallinity of the PVA film increases with UV irradiation and with the presence of Ni0.04Zn0.96O and Fe0.03Zn0.97O. The roughness of the PVA film was not modified by the addition of the doped oxides; however, it increases after UV irradiation, more significantly in the films containing the oxides. The PVA film exhibits absorption around 280 nm characteristic of pep* transitions related to carbonyl groups from residuals acetate, while the 95/05 PVA/Ni0.04Zn0.96O and 95/05 PVA/Fe0.03Zn0.97O nanocomposite films show absorption at the visible region which is characteristics of the band gap reduction of the doped oxides. The photoluminescence of PVA was modified by the presence of the oxides in the film. These nanocomposite films are interesting due to their thermal, mechanical (flexible) properties and low cost of production. In addition they are also able to exhibit peculiar optical properties showing potential to be used in photonic devices, gas sensors and organic solar cell applications.

Thermal lens (TL) spectroscopy in a dual-beam configuration was applied in a study on biodiesel and oil–biodiesel blends. The goal of this work was to evaluate the behavior of the thermal and mass diffusivities that arose when oil was added to biodiesel and to verify the capability of the method to identify small concentrations of triacylglycerol in biofuel. When transitioning from pure biodiesel to a blend consisting of 98% biodiesel and 2% soybean oil, the thermal diffusivity decreased 15% and the mass diffusivity increased 59%, which indicated that both parameters can provide significant information about the presence of oil in biodiesel. Therefore, TL spectroscopy can be a useful method for certifying the quality of biodiesel and biodiesel blends.

A dispersive white-light Michelson interferometer was used to determine the wavelength dependence of the refractive index (n) in the visible range from 425 to 775 nm and the thermo-optical coefficient (dn/dT) of fused silica (FS) and borosilicate glass (BK7). For FS, the values obtained for n and dn/dT at 546 nm were 1.46079 and 11.3×10−6 K−1, respectively, while the values for BK7 glass were 1.51825 and 2.2×10−6 K−1, respectively, which is in good agreement with the literature. The accuracy of the methodology used for n was almost 10−6, enabling precise spectroscopic characterization of materials across a wide spectral range.

From initial calcium aluminosilicate glass, transparent glass-ceramics have been successfully synthesized under simultaneous high pressure and temperature (SHPT). Possible homogeneous volumetric crystallization of this glassy system, which was not achieved previously by means of conventional heat treatment, has been put in evidence with a SHPT procedure. Structural, mechanical, and optical properties of glass and glass-ceramic obtained were investigated. Raman spectroscopy and X-ray diffraction allowed to identify two main crystalline phases: merwinite [Ca3Mg(SiO4)2] and diopside [CaMgSi2O6]. A Raman scanning profile showed that the formation of merwinite is quite homogeneous over the bulk sample. However, the sample surface also contains significant diopside crystals. Instrumented Berkovich nanoindentation was applied to determine the effect of SHPT on hardness from glass to glass-ceramic. For Eu-doped samples, the broadband emission due to 4f65d1 → 4f7 transition of Eu2+ was studied in both host systems. Additionally, the 5D0 → 7FJ transition of Eu3+ was used as an environment probe in the pristine glass and the glass-ceramic.

In situ micro-Raman spectroscopy was used to investigate the structural evolution of OH(-)-free calcium aluminosilicate glasses, under high pressure and at room temperature. Evaluation was made of the role of the SiO2 concentration in percalcic join systems, for Al/(Al + Si) in the approximate range from 0.9 to 0.2. Under high pressure, the intensity of the main band related to the bending mode of bridging oxygen ([Formula: see text][T-O-T], where T = Si or Al) decreased gradually, suggesting that the bonds were severely altered or even destroyed. In Si-rich glasses, compression induced a transformation of Q (n) species to Q (n-1). In the case of Al-rich glass, the Al in the smallest Q (n) units evolved from tetrahedral to higher-coordinated Al (([5])Al and ([6])Al). Permanent structural changes were observed in samples recovered from the highest pressure of around 15 GPa and, particularly for Si-rich samples, the recovered structure showed an increase of three-membered rings in the Si/Al tetrahedral network.

Eu 3+ and Eu 2+ co-doped calcium aluminosilicate glass–ceramics have been prepared by devitrification of calcium aluminosilicate glass using heat-treatment. Control of crystallization in the glass–ceramics was studied by X-ray diffraction (XRD) and Raman spectroscopy. The results showed that crystalline phases in glass–ceramic belong to the family of melilite Ca 2 Mg 0.25 Al 1.5 Si 1.25 O 7 as the major phase and anorthite CaAl 2 Si 2 O 8 as the minor phase. Luminescent properties were investigated by emission; lifetime and the color points were calculated. Emission spectra showed that Eu 2+ entered into the crystalline phase in a two steps mechanism: first as Eu 3+ which is then reduced to Eu 2+ . This incorporation in the crystal enhanced Eu 2+ emission with increasing time of heat-treatment and therefore crystallization.

In this paper, we report results concerning tunable light emission and color temperature in cerium-doped low-silica-calcium-alumino-silicate (LSCAS) glass for smart white-light devices. Spectroscopic results, analyzed using the CIE 1931 x – y chromatic diagram, show that this glass presents two broad emission bands centered at 475 and 540 nm, whose intensities can be tuned by the excitation wavelength. Moreover, the same emission can be achieved from a color temperature range from 3200 to 10,000 K, with a color-rendering index (CRI) of around 75% obtained by changing the optical path length of the sample. Our new phosphor LSCAS glass, which is a unique system that exhibits tunable yellow emission, combines all qualities for white-light devices.

ZnO nanoparticles with average diameter of 25 nm were synthesized by a modified sol–gel method and used in the preparation of (in wt.%) (100 − x) poly(vinyl alcohol) (PVA)/x ZnO nanocomposite films, with x = 0, 1, 2, 3, 4, and 5. The PVA/ZnO films were exposed to UV radiation for 96 h and their thermal, morphological, and spectroscopic properties were investigated. In inert atmosphere, the nanocomposite films showed lower thermal stability than the pure PVA film, and the calorimetric data suggest an interaction between PVA and ZnO in the nanocomposite films. Some crystalline phases could be seen in the films with ZnO, and a direct dependence on the ZnO concentration was also observed. The original structure of ZnO nanoparticles remained unaltered in the PVA matrix and they were uniformly distributed on the film surface. The roughness of the PVA film was not modified by the addition of ZnO; however, it increased after 96 h of UV irradiation, more significantly in the nanocomposite films. The films showed an absorption band centered at 370 nm and a broad emission band in the UV–vis region when excited at 325 nm.

In this work we report on the use of the Thermal Lens method to verify the evolution of the thermal diffusivity of sunflower and soybean vegetable oils utilized in preparation of twenty five snacks portions. Our results show that the thermal diffusivity for sunflower oil does not change between 1 and 25 portions of fried snacks. By another hand, the soybean thermal diffusivity exhibits a little decrease for higher portion of fried snacks, indicating that for this oil the triglyceride level is reduced as a degradation process.

This work presents the results of the investigation of structural and thermal properties of Nd3+-doped tellurite glasses with low OH content. The samples were characterized by XRD, FTIR, DTA, UV/VIS/NIR and Archimedes’ method. Tellurite glasses of composition (100 – x)(0.8TeO2 + 0.2WO3) + xNd2O3 (x = 0, 0.05, 0.5, 1, 2, and 4 mol%) were prepared in both ambient and oxygen atmospheres. All samples showed an increase of the values of Tg, Tx, and Tx-Tg with Nd2O3 addition. The reduction of OH content implies a slight decrease of Tg. The density and the molar volume of the glasses increased with Nd2O3. The intensity of the absorption bands associated with Te-O bonds of TeO4 units decreased compared with the bands associated with Te-O bonds of TeO3+1/3 units. This indicates that Nd2O3 favors the transformation of the TeO4 groups in TeO3 groups via TeO3+1, increasing the NBOs and contributing to the formation of strongly hydrogen-bonded OH groups. The samples made in O2 showed a reduction of 48% of “free” OH ions compared with the Amb ones.

Made available in DSpace on 2018-12-11T16:39:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-09-25 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In this work, we investigate the spectroscopy properties of neodymium doped tungsten-tellurite glasses prepared in ambient and O2-rich atmospheres. A conversion of TeO4 to TeO3 units was caused by the addition of Nd3+ into the glass, which was confirmed by absorption spectra and by Judd-Ofelt parameter behavior. The relaxation of the 4F3/2 level is dominated by radiative decay and cross-relaxation between Nd3+ and Nd3+ ions. The energy transfer from Nd3+ to the hydroxyl group is negligible when compared to the cross-relaxation. The luminescence quantum efficiency values of the 4F3/2 level decreases as the Nd3+ concentration increases, independently if determined by the Judd-Ofelt method or by the thermal lens technique. The observed reduction in the IR absorption associated to OH groups was not effective to improve the luminescence quantum efficiency. Faculdade de Engenharia, UNESP - Univ Estadual Paulista, Campus de Ilha Solteira Laboratório de Laser e Aplicações, IFSC UFGD Grupo de Espectroscopia Óptica e Fototérmica, UEMS Faculdade de Engenharia, UNESP - Univ Estadual Paulista, Campus de Ilha Solteira CAPES: 042/2010 CNPq: 305063/2012-0 CNPq: 445286/2014-8

In this work, low-cost substrates with rough silver surfaces were prepared from commercial copper foil-covered phenolic board (CPB) and an aqueous solution of AgNO3, and were used for surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) measurements. A maximum SERS amplification factor of 1.2 × 107 was obtained for Rhodamine 6G (R6G), and use of the CPB resulted in a detection limit for Thiram pesticide of 0.5 µmol L−1. The minimum detection level was limited by residual traces of phenolic groups that originated from the substrate resin, which became solubilized in the aqueous Ag+ solution. It was found that the bands corresponding to the impurities had less influence in the Thiram analysis, which could be explained by the high affinity of sulfur for Ag surfaces. The influence of impurities in the SERS analyses therefore depended on the linkage between the rough silver surface and the analyte. The findings demonstrated the ease and effectiveness of using CPB to prepare a nanostructured surface for SERS.

An interferometric technique was used to determine the temperature coefficient of the optical path length (dS/dT) as a function of the temperature in several optical glasses. The temperature range was between 25 � C and 180 � C. The studied samples included undoped and doped oxide glasses, such as low silica calcium aluminosilicate, phosphates, borates and also chalcogenides. The oxide glasses had dS/dT between 10 · 10 � 6 K � 1 and 20 · 10 � 6 K � 1 , while for the chalcogenides, these were around 70 · 10 � 6 K � 1 . The results showed that dS/dTs increased with the temperature in all samples. For samples doped with Nd the dS/dT values were found to be independent of concentration. On the other hand, for the phosphate glass doped with Cr, dS/dT increased about 5% when compared with the Nd doped one. In conclusion, the used interferometric method, which is a considerably simpler and a lower cost technique, and is a useful tool to measure dS/dT in semi-transparent glasses as a function of the composition and temperature. � 2004 Elsevier B.V. All rights reserved.

The absorption and luminescence spectra for the poly( p -phenylene vinylene)/sol–gel silica with different thermal treatments were measured. A considerable increase in the luminescence was observed for the polymer introduced into SiO 2 matrix with thermal treatment at 120 °C. The thermal diffusivity of these samples was measured using the thermal lens technique, and the obtained value 3.3 × 10 −5 cm 2 /s (sample treated at 37 °C) is practically independent of the thermal treatment (37–150 °C).

In this work the ability of thermal lens spectrometry for different temperature studies in transparent materials is discussed. The method was applied in polymers and optical glasses to measure the thermo-optical properties as a function of the temperature. The focus of the discussion will be on the temperature range where the glass transition occurs. The perspectives of future studies in this area will be discussed.

Mid-infrared absorption spectroscopy was used to analyze soybean oil, ethylic and methylic soybean biodiesel, and blends prepared with soybean oil mixed with biodiesel, in order to evaluate this method as an alternative to assess oil as impurities or adulterant in biodiesel. We also aimed to determine whether the biodiesel was prepared by the ethyl or methyl routes, by inspecting the infrared spectra. The C-O functional groups between 1100 and 1200 cm-1 are different for oil and biodiesel, which allows them to be used to distinguish impurities (residual oil) in biofuel. The peak C-O-C at 1017 cm-1 is characteristic for methylic biodiesel, and the peak O-C-C at 1035 cm-1 for ethylic biodiesel. These vibrational modes can therefore be used to indicate the route used to prepare the biofuel. Results indicated that infrared spectroscopy is appropriate for monitoring the quality of biofuel for commercial sale.