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Sol-gel materials may found plenty of applications, e.g., as carriers for various substances, which can be exploited for sensing purposes or as drug releasing carriers. In this work, the fluorescence properties of two photosensitizers immobilized in silica based sol-gel materials were examined. The sol-gel materials were produced from silica precursor TEOS and 96% ethyl alcohol as solvent. Materials with various ratios R (solvent to precursor molar ratio) 5, 15, 20, 32, 40, and 50, were prepared. Photolon and protoporphyrine PPIX were used as dopants in concentrations 0.001%, 0.005%, 0.01% and 0.05%. The excitation wavelength from a blue laser was 415 nm. The highest luminescence was observed for the material prepared with R = 20, whereas for R = 5 it was the lowest one. The fluorescence quenching for highest photosensitizer concentration was observed, as well. [ABSTRACT FROM AUTHOR]

In this work, the series of Tb3+/Eu3+ co-doped xerogels and derivative glass-ceramics containing CaF2 nanocrystals were prepared and characterized. The in situ formation of fluoride crystals was verified by an X-ray diffraction technique (XRD) and transmission electron microscopy (TEM). The studies of the Tb3+/Eu3+ energy transfer (ET) process were performed based on excitation and emission spectra along with luminescence decay analysis. According to emission spectra recorded under near-ultraviolet (NUV) excitation (351 nm, 7F6 → 5L9 transition of Tb3+), the mutual coexistence of the 5D4 → 7FJ (J = 6–3) (Tb3+) and the 5D0 → 7FJ (J = 0–4) (Eu3+) luminescence bands was clearly observed. The co-doping also resulted in gradual shortening of a lifetime from the 5D4 state of Tb3+ ions, and the ET efficiencies were varied from ηET = 11.9% (Tb3+:Eu3+ = 1:0.5) to ηET = 22.9% (Tb3+:Eu3+ = 1:2) for xerogels, and from ηET = 25.7% (Tb3+:Eu3+ = 1:0.5) up to ηET = 67.4% (Tb3+:Eu3+ = 1:2) for glass-ceramics. Performed decay analysis from the 5D0 (Eu3+) and the 5D4 (Tb3+) state revealed a correlation with the change in Tb3+–Eu3+ and Eu3+–Eu3+ interionic distances resulting from both the variable Tb3+:Eu3+ molar ratio and their partial segregation in CaF2 nanophase. [ABSTRACT FROM AUTHOR]

In this work, new films containing composite materials based on blends of thermoplastic polymers of the polyurethane (TPU) and polyolefin (TPO) type, in the absence and presence of BaTiO3 nanoparticles (NPs) with the size smaller 100 nm, were prepared. The vibrational properties of the free films depending on the weight ratio of the two thermoplastic polymers were studied. Our results demonstrate that these films are optically active, with strong, broad, and adjustable photoluminescence by varying the amount of TPU. The crystalline structure of BaTiO3 and the influence of thermoplastic polymers on the crystallization process of these inorganic NPs were determined by X-ray diffraction (XRD) studies. The vibrational changes induced in the thermoplastic polymer's matrix of the BaTiO3 NPs were showcased by Raman scattering and FTIR spectroscopy. The incorporation of BaTiO3 NPs in the matrix of thermoplastic elastomers revealed the shift dependence of the photoluminescence (PL) band depending on the BaTiO3 NP concentration, which was capable of covering a wide visible spectral range. The dependencies of the dielectric relaxation phenomena with the weight of BaTiO3 NPs in thermoplastic polymers blends were also demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Transparent Nd:YAG ceramics composed of nanosized grains were fabricated by the low temperature high pressure (LTHP) sintering technique. The effect of concentration of ions on luminescence properties of Nd3+ doped YAG nanoceramics and nanopowders was investigated. It was found that at room temperature the intensity ratio of 4F3/2 → 4I9/2 and 4F3/2 → 4I11/2 transitions in nanoceramics was strongly dependent on concentration of Nd3+. This behavior was not observed for the Nd:YAG nanopowders. The nature of such behavior was briefly discussed in terms of lowering the site symmetry of Nd3+ ions with applied pressure. [Copyright &y& Elsevier]

Due to the rising concentration of toxic nitrogen oxides (NO x ) in the air, effective methods of NO x removal have been extensively studied recently. In the present study, the first developed WO 3 /S-doped g-C 3 N 4 nanocomposite was synthesized using a facile method to remove NOx in air efficiently. The photocatalytic tests performed in a newly designed continuous-flow photoreactor with an LED array and online monitored NO 2 and NO system allowed the investigation of photocatalyst layers at the pilot scale. The WO 3 /S-doped-g-C 3 N 4 nanocomposite, as well as single components, were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller surface area analysis (BET), X-ray fluorescence spectroscopy (XRF), X-ray photoemission spectroscopy method (XPS), UV-vis diffuse reflectance spectroscopy (DR/UV-vis), and photoluminescence spectroscopy with charge carriers' lifetime measurements. All materials exhibited high efficiency in photocatalytic NO 2 conversion, and 100% was reached in less than 5 min of illumination under simulated solar light. The effect of process parameters in the experimental setup together with WO 3 /S-doped g-C 3 N 4 photocatalysts was studied in detail. Finally, the stability of the composite was tested in five subsequent cycles of photocatalytic degradation. The WO 3 /S-doped g-C 3 N 4 was stable in time and did not undergo deactivation due to the blocking of active sites on the photocatalyst's surface.

The series of Gd 3- x Ce x Ga 3 Al 2 O 12 nanopowders doped with different concentrations of Ce 3+ ions were prepared by Pechini (sol-gel) and combustion methods. The structure and morphology of the powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. It was found that the synthesis method has a great impact on the morphology and, consequently, spectroscopic properties of the powders. Optical properties of the powders were examined using excitation, emission, and luminescence kinetic measurements. For all powders, persistent luminescence and emission decay processes were studied. The most intense luminescence was observed for the powder with 0.5 mol % of Ce 3+ synthesized using the combustion method and 1 mol % in the case of the sol-gel sample. The longest and brightest persistent luminescence was observed for the powders doped with 0.1 mol % (combustion) and 0.2 mol % of Ce 3+ ions (sol-gel). The thermoluminescence measurements were done for the powders prepared using different methods to understand the impact of the synthesis conditions on the number and depths of the traps involved in persistent luminescence. On the basis of spectroscopic measurements, the mechanism of persistent luminescence was constructed and discussed.

The aim of this work was to check the influence of Tb 3+ ion concentration and synthesis method on the persistent luminescence properties. A series of Gd 3-x Tb x Ga 3 Al 2 O 12 nanopowders were obtained by using two different synthesis methods. The crystal structure refinement was performed to check the impact of the preparation method and doping level on the crystallization process. This revealed the influence of doping level on conventional and persistent luminescence color, intensity and decay time. It was demonstrated that it is possible to tune the persistent luminescence color by changing the Tb 3+ doping level. The spectroscopic measurements show that persistent luminescence appears only under UV excitation, suggesting that the 5d levels of Tb 3+ play an active role in this process. Thermoluminescence measurements indicate that the depth and number of electron traps in the samples are associated with the synthesis method and dopant concentration. Based on the results, the possible mechanism of energy transfer between the traps and luminescence centers is proposed and discussed.

Nanocrystalline La 0.9 A 0.1 MnO 3 (where A is Li, Na, K) powders were synthesized by a combustion method. The powders used to prepare nanoceramics were fabricated via a high-temperature sintering method. The structure and morphology of all compounds were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). It was found that the size of the crystallites depended on the type of alkali ions used. The high-pressure sintering method kept the nanosized character of the grains in the ceramics, which had a significant impact on their physical properties. Magnetization studies were performed for both powder and ceramic samples in order to check the impact of the alkali ion dopants as well as the sintering pressure on the magnetization of the compounds. It was found that, by using different dopants, it was possible to strongly change the magnetic characteristics of the manganites.