The properties of lanthanides allow them to be used as contrast agents for magnetic resonance imaging, thereby helping to differentiate between tissues, organs, and pathologies more efficiently. Lanthanides contain thermosensitive energy levels that aid identification of cancer and healthy cells. This work investigates the GdVO4 matrix obtained by the non-hydrolytic sol-gel methodology and doped with the lanthanide ions Er3+ and Yb3+ at a 1:1 molar ratio. The efficiency of the optical parameters was analyzed on the basis of the Er3+ green emission after excitation in the infrared region, namely 980 nm. The temperature-dependent fluorescence intensity ratio (FIR) between the thermally coupled Er3+ levels (2H11/2 and 4S3/2 → 4I15/2) was evaluated. The Er3+ emission depended on the laser power. The calculated number of photons was 2 in this case. Temperatures ranging from 298.3 to 374.5 K were assessed, and the sensitivity varied from 1.2 to 1.9% K-1, respectively. The initial temperature was estimated.

We have incorporated rhodamine into polyamide membranes by additive manufacture selective laser sintering technology. Incorporation into 0.5 cm2 membranes was conducted at different pH values and constant temperature of 25 oC. The amounts of incorporated dye were determined by a calibration curve, and analyses showed rhodamine incorporation in the order of 10-6 mol L-1. The absorption spectra of the solutions and membranes after rhodamine incorporation showed maximum absorption at 553 nm and a shoulder at 522 nm, which indicated that a dimer was formed. Photoluminescence presented maximum emission at 575 nm for the sample incorporated with rhodamine in acid pH. The membranes that were treated with acid presented shorter adsorption time and demanded 180 min to reach equilibrium, whereas the non-treated membrane and the membranes that were treated with base required 1440 min to reach equilibrium. Polyamide membrane has proven to be an excellent material for the incorporation of dyes and compounds for application as luminescent sensors.

This paper reports the synthesis and characterization of Cr3+-doped alumina by the sol-gel non-hydrolytic methodology. The resulting sample was treated at different temperatures. X-ray diffraction revealed that the ruby phase emerged in the sample treated at 1100 ºC, which was later confirmed by absorption bands correspondent to Cr3+ ions allowed transitions at 4A2 → 4T1, 4T2, and forbidden at 4A2 → 2T1, 2E, observed by diffuse reflectance UV-Vis. The luminescence spectroscopy showed the intensity band at 694 nm in red region, characterized of the Cr3+ ion. The peaks at 702 and 705 nm correspond to N1 and N2 lines, respectively, which arose from the second and fourth nearest-neighbor exchange-coupled pairs of chromium(III) ion, respectively, ascribed to high chromium(III) concentration. The Cr3+ cluster formation was observed in electron paramagnetic resonance signal as discussed in this work. Nuclear magnetic resonance evidenced that the 27 Al symmetry changed in the samples treated between 900 and 1100 ºC.

Inorganic matrices have been extensively studied for several applications, mainly doped with lanthanoid ions presenting special spectroscopic properties. The radiation emission can be affected by several factors, such as; matrix, synthesis methodology, activating ions and sensitizers, and concentrations. Thus, in this work the matrix of yttrium vanadate doped with Eu3+ ions as activator and Bi3+ ions as sensitizer was prepared by the non-hydrolytic sol-gel methodology. Europium (III) and Bismuth (III) ions concentrations were varied in 1, 3 and 5% in mol with respect to the Y3+ ion and the samples were heat treated at 1000 °C. The X-ray diffraction analyzes showed a single phase of the yttrium vanadate matrix, indicating the non-influence of the dopant ions on the crystalline structure. The dopants concentrations presented influences on the spectroscopic properties of the emitting ion, the intensity parameters (Ω2 e Ω4), increased as a function of the increase of Bi3+ concentration, affecting the covalence of the bond and the rigidity of the system. The increase of Eu3+ concentration directly affected its environment, decreasing the symmetry and increasing the quantum efficiency. Finally, increasing the dopant ions promoted the decreasing the crystallite size.

Lanthanide ions have special light emission, which can occur through descending and ascending energy conversion. Ascending energy conversion is especially interesting for bioapplications because excitation in the infrared region does not excite biomolecules and therefore does not interfere in detection, not to mention that it penetrates deeper in the skin. Here, we synthesized yttrium and aluminum oxide doped with Yb3+and Er3+ions via the non-hydrolytic sol-gel methodology. The doped matrix was incorporated and dispersed over a polyamide membrane obtained by Additive Manufacturing. X-ray diffraction revealed that a mixture of yttrium aluminum monoclinic and garnet phases emerged. Upon excitation at 980 nm in the Yb3+ion, the Er3+ presented more intense emission as a function of the laser power, which favored red emission. The intensities of the bands corresponding to the 4S3/2 → 4I15/2 (563 nm) and 5F9/2 → 4I15/2 (660 nm) transitions involved the absorption of two photons. The oxide incorporated into the polyamide membrane presented the same behavior. After coating with polyetherimide, the latter system was resistant to 5.1 W laser, which paves the way for new applications.

In this study, Dy3+-doped LaNbO4 phosphors with a blue to white emission that can be tuned by varying the activator concentration were prepared by one-step spray pyrolysis process. According to the powder X-ray diffraction results, increasing Dy3+ concentration favored the tetragonal phase. Slight changes were observed in the recorded Raman spectra as a function of Dy3+ concentrations while SEM (scanning electron microscopy) micrographs presented similar profiles regardless the Dy3+ amount. Investigation of Dy3+ emission data in the visible range showed that rising the Dy3+ concentration progressively shifted the emission towards the white color. All samples presented a wide excitation range from 254 to 475 nm.

Conductive thin films have various applications in different technological fields. Indium tin oxide (ITO) is a mixed oxide. In the film form, ITO has been widely employed as electrode in many optoelectronic devices. Methods like thermal evaporation, sputtering, chemical vapor deposition (CVD), electron beam, spray coating, and sol-gel synthesis give ITO thin films. In this work, we prepared ITO thin films by dip coating of a glass substrate into ITO obtained by spray pyrolysis. ITO consisted of spherical particles with different diameters. The ITO thin films were treated with laser. X-ray diffraction (XRD) analysis confirmed that spray pyrolysis produced spherical ITO particles. Transmittance analyses revealed the production of transparent films with thickness ranging from 0.800 to 1.200 µm. The four-wire test showed that the porosity of the films led to low conductivity. Film resistance was a function of the number of layers of ITO thin film.

Over the last decades, the combination of different technologies to search for systems with new properties and features has brought various segments of biological and earth sciences together. Additive manufacturing, known as rapid prototyping, combined with the sol-gel methodology enables the production of novel systems with applications in many scientific fields. In this work, flexible polyamide membranes were obtained by additive manufacturing, functionalized by the sol-gel methodology, and incorporated with the coordination compound between Eu(III) and 1,10-phenanthroline. The presence of vibrations at 1100 cm-1 in the FTIR spectrum of the material, which is a band typical of the Si-O-Si group in the alkoxide employed during the process, confirmed the polyamide membrane functionalization. The thermogravimetric curve showed that a residue remained after heating at 700 ºC, which was attributed to SiO2. The membrane was highly luminescent, which confirmed incorporation of the Eu3+ compound into the material and pointed to the possible application of this system as a topical medication for the treatment of skin diseases.

Bentonite is a natural clay that presents characteristics such as good capacity to exchange cations, large specific surface area, large porosity, and possibility to undergo intercalation and/or functionalization. This work reports on bentonite functionalization with organomodified alkoxides. Functionalization afforded hybrid materials displaying desirable properties for adsorption of chromium trivalent ions. Infrared absorption spectroscopy, X-ray powder diffraction, thermal analysis, specific surface area analysis, and adsorption experiments with methylene blue helped to characterize the materials and evaluate their cationic exchange capability. These techniques evidenced functionalization of the Brazilian bentonite. Kinetic and equilibrium experiments on the adsorption of chromium trivalent ions aided determination of the equilibrium time of kinetic adsorption isotherms and revealed whether the functionalized matrices adsorbed chromium trivalent ions. Chromium displayed S1 type adsorption isotherms, which confirmed that adsorption capacity originated from cooperative forces between the adsorbate and the hybrid adsorbents.

The phosphor-converted light-emitting diode technique is an important solid-state illumination strategy. Sulfide-based materials are the most often employed red phosphors, but they are chemically unstable and present lower efficiency in comparison to the blue and green phosphors. Therefore, it is important to find a new red phosphor source that can emit intense red light while absorbing light in the near ultraviolet (UV) spectral region. This paper describes the photoluminescence properties of Nb2O5:La3+,Eu3+ obtained by the non-hydrolytic sol-gel process. The X-ray results indicated that the thermal treatment allowed to obtain the different crystalline structures such as, the orthorhombic and monoclinic phases for the Nb2O5 and the orthorhombic phase for the La2Nb10O28. This polymorphism was also confirmed by the Raman spectroscopy. The luminescence spectra revealed the existence of the Eu3+ ions in both crystalline phases for the samples annealed at higher temperature, depending of the excitation wavelength. The emission spectrum showed that increasing the annealing temperature promotes the narrowing of all intraconfigurational f-f transitions for the Eu3+ ions, due to the structural changes. In addition, all samples present good CIE (International Illumination Committee) chromaticity coordinates when excited in the UV (275 and 394 nm), blue (465 nm) and green (525 nm) radiation.

Utilizouse a metodologia solgel para obtenção de uma matriz de sílica modificada com íons de cálcio e fosfato. Preparouse a matriz, por hidrólise e condensação dos precursores trietil fosfato, nitrato de cálcio, e tetraetilortosilicato, que foram as fontes de fosfato, de cálcio, e de silício, respectivamente. As amostras foram secas e tratadas termicamente a 110 e 900°C e colocadas em contato com fluido corporal simulado (SBF) por três dias. Realizouse microscopia eletrônica de varredura, difração de raios X, espectroscopia na região do infravermelho, o que evidenciou que a amostra tratada a 110°C continha silicato de cálcio, fosfato e hidroxiapatita, antes e após o contato com SBF, respectivamente. A amostra tratada a 900°C exibiu a fase hidroxiapatita, antes e após o contato com SBF, mas a fase cristalina foi mais evidente após o contato. Em conclusão, o método de solgel forneceu amostras bioativas para regeneração óssea.

We employed the solgel methodology to obtain a silica matrix modified with calcium and phosphate ions. We prepared the matrix by hydrolysis and condensation of the precursors triethyl phosphate, calcium nitrate, and tetraethylorthosilicate, which were the sources of phosphate, calcium, and silicon, respectively. We dried and heattreated the samples at 110 or 900°C and placed them in simulated body fluid (SBF) for three days. We conducted scanning electron microscopy, Xray diffraction, and infrared spectroscopy analyses, which evidenced that the sample treated at 110°C contained calcium phosphate silicate and hydroxyapatite before and after contact with SBF, respectively. The sample treated at 900°C exhibited a hydroxyapatite phase before and after contact with SBF, but the crystalline phase was more evident after the contact. In conclusion, the solgel methodology provided bioactive samples for bone regeneration.

The thermal stability of vegetable oils is an important factor that affects their quality. In this study, we investigated the thermal stability of oil and lecithin extracted from soybeans by two distinct processes: mechanical extraction (pressing) and physical extraction (solvent). Thermal analysis was used to obtain information about different methodologies of extraction. The physically extracted products proved more stable than those extracted mechanically. Raman and UV-Vis techniques were applied to underpin the discussion of process differences.

In this work, we report the synthesis and the photoluminescence features of Eu(III)-doped yttrium-aluminium oxide obtained by non-hydrolytic sol-gel routes. After heating the powders above 600 ºC the XRD patterns show the presence of the Y4Al2O9 (YAM) and Y3Al5O12 (YAG) phases. At 800 and at 1500 ºC the PL spectra display the Eu(III) lines characteristic of the YAM monoclinic phase. The 5D0->7F2 transition is favored relatively to the 5D0->7F1 lines. However, at 1100 ºC the cubic YAG is the preferential phase and the 5D0->7F1 transition dominates the spectrum. The Eu(III) ions lie in a centrosymmetrical site. The different solvents used in the sol-gel synthesis also change the relative proportion between these two phases. This is monitored analyzing the modifications in the relative intensity between the 5D0->7F2 and the 5D0->7F1 transitions.