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Abstract: Results of structural and spectroscopic measurements of Sm3+ doped calcium aluminates: Ca1−x Sm x Al4O7 and Ca1−2x Sm x Na x Al4O7 (x=0.0005, 0.002, 0.01, 0.02, 0.03, 0.05) obtained by the modified Pechini method are presented. All samples yield intense orange–red emission under violet excitation (404.5nm). Narrow bands corresponding to characteristic f–f intraconfigurational transition of Sm3+ in excitation and emission spectra were observed. The influences of the concentration of Sm3+ as well as charge compensation by co-doping with Na+ ions on the luminescent properties of the phosphor were investigated. Detailed analysis of the emission spectra of Sm3+ doped and Sm3+,Na+ co-doped CaAl4O7 powders proved that activator ions substitute Ca2+ in the host. Co-doping with Na+ ions enhanced greatly the intensity of the luminescence. Concentration dependencies of the intensity of luminescence and its decay kinetics proved the emission quenching at higher dopant contents due to cross-relaxation processes between Sm3+ ions. Fitting of the 4G5/2 state fluorescence decay to the Inokuti–Hirayama model indicated dipole–dipole interaction as the dominant mechanism of the cross-relaxation processes. [Copyright &y& Elsevier]

Powders and thin films of nanocrystalline yttrium disilicate (Y2Si2O7) doped with Ce3+ have been prepared by a sol–gel method. Structure and morphology of the synthesised samples have been determined and spectroscopic properties compared. The triclinic α-Y2Si2O7 form (space group P 1-) for the powders annealed between 1000°C and 1200°C has been found. A total conversion into a thortveitite-type monoclinic β-Y2Si2O7 polymorph after annealing of powder samples at 1400°C (space group C2/m) has been observed. In the case of films even at 1300°C the basically pure triclinic α-Y2Si2O7 phase was observed with luminescent spectroscopy. The influence of grain size, controlled by thermal treatment, on the structure and luminescence properties of the fabricated materials are presented and discussed. [ABSTRACT FROM AUTHOR]

Abstract: HfO2 and HfO2:Eu powders were synthesized with Pechini method at temperatures in the range of 600–1500°C. Structural, radioluminescence and photoluminescence properties of the powders were investigated. The highest light output of about 20% of the efficiency of commercial GOS:Eu was found for materials containing 0.5% of Eu and prepared at 1500°C. The data shows, that further improvement of light output could be obtained if materials are processed at yet higher temperatures. Emission spectra indicate that Eu3+ experiences variety of symmetries of its surroundings. Undoped materials produce broad band emission peaking at 480nm and showing a significant afterglow. [Copyright &y& Elsevier]

Abstract: A comparative analysis of the luminescent properties of YAG and YAG:Ce nanopowders (NP) in comparison with single crystalline film (SCF) and single crystal (SC) analogues was performed under excitation by a pulsed synchrotron and X-ray radiation. It was shown that the natural defects concentration in NP was between the SC with a large (∼0.18–0.19at.%) concentration of YAl antisite defects (AD) and SCF of these garnets where YAl AD were completely absent. At the same time, Ce3+ doped YAG NP showed luminescent properties close to those of YAG:Ce SCF. [Copyright &y& Elsevier]

Abstract: Nanocrystalline Lu2O3 doped with 1at.% of Eu was obtained precipitating hydroxide of lutetium with urea at 80°C from water solution and decomposing the hydroxide to oxide at 500°C. Polyvinyl alcohol was used to hinder the particles growth during precipitation. The average size of the fabricated particles was 2–5nm. Although at 500°C the hydroxide decomposed to Eu-doped Lu2O3 traces of OH impurities were present in the material unless heated at 1200°C. Radioluminescence was very poor for samples heated at 800°C or lower temperature. After heating the precipitated powder at or above 1200°C the efficiency jumped 45 times reaching 75% of the output from commercial microcrystalline Gd2O2S:Eu. The properties make nanocrystalline Lu2O3:Eu prepared in the described way a promising X-ray phosphor for planar digital medical imaging. [Copyright &y& Elsevier]

The paper reports on the course of decomposition of hydrated lutetium nitrate and lutetium chloride to Lu2O3 in the eutectic mixture of NaNO2 and KNO2. It was shown that a crystallographically pure phase of the cubic Lu2O3 is formed at temperature as low as 250 °C. IR spectra revealed that the recovered powder contains some OH-contamination, however. The powders are characterized by crystallites sizes in the range of 18–30 nm in average. Emission and excitation spectra of Eu-doped powders show characteristic features for Eu3+ ion in an oxide host, which indicates that the procedure is appropriate for making activated nanoparticulate oxide phosphors. Most profound emission appears around 611 nm and the luminescence from the powder made starting with Lu(NO3)3 was noticeably higher compared to the product obtained from LuCl3. The excitation spectrum of Eu3+ emission at 611 nm contains a band related to the fundamental absorption of the lutetia host lattice, which indicates an existence of the host-to-activator energy transfer. [Copyright &y& Elsevier]

Two series of Lu2O3:Eu nanocrystalline phosphors were prepared using either combustion procedure with urea fuel or the Pechini procedure. The dopant concentration varied in both series from 0.2 to 13% with respect to Lu. Despite full crystallization and very similar microstructure of materials of both series, we found profound variations in their spectroscopic properties. The combustion-made phosphors were much less efficient emitters and their emission was strongly concentration-quenched above 3% of the dopant content. For the Pechini-derived materials, the concentration quenching was not observed below 10% of the dopant content and even for the dopant concentrations equal to 10 and 13% the quenching was insignificant. In EPR spectra for Gd3+-doped materials, a significant broadening of lines was found for the combustion-made powders. All these observations imply a strong agglomeration of the dopant ions in the specimens made by applying urea fuel in the combustion process. A semi-two-phase composition was suggested in the combustion-prepared powders. In the Pechini-derived nanocrystalline powders, the dopant ions are uniformly, statistically distributed in the host lattice. [Copyright &y& Elsevier]

Efforts to obtain translucent pellets of BAM for Martian UV-dosimeter were undertaken. Sinterability of both commercial BAM powder and a Pechini-derived one was examined. The commercial phosphor sinters with difficulty only, while the one made with Pechini procedure sinters easily and translucent pellets could be obtained in such a way. Vacuum sintering at 1750 °C for 15 h was also enough to fully convert Eu3+ into Eu2+ in the sintered pellets without the necessity of using hydrogen-containing gas. The spectroscopy of the sintered BAM differs noticeably from its commercial powdered counterpart. The excitation is much more flat in the entire UV and especially strong enhancement of the excitation efficiency is observed in the near-Vis part of the UV region. Decay kinetics is exactly the same for commercial powder and sintered ceramic, which proves the lack of luminescence quenching in the latter. The sintered pellets of BAM made in our laboratory show mechanical and spectral characteristics, which make the material suitable for Martian UV-dosimeter. [Copyright &y& Elsevier]

Nanocrystalline powders of Lu2O3:Eu with the activator content varying in the range of 0.2–10% were prepared through a combustion technique. The powders were only slightly agglomerated and the size of crystallites were about 30 nm. Some of the powders were co-doped with Mg, Ca, Sr, Ba, La of various concentrations. Such powders were cold-pressed and sintered at 1750°C for 5 h in vacuum. X-ray-excited luminescence spectra of both the powders and the sintered ceramics were recorded and the efficiency was compared to the commercial standard Gd2O2S:Pr,Ce,F X-ray phosphor. It was found that the nanocrystalline powders of Lu2O3:Eu,Ca emit photons four-times less than the commercial micron-sized Gd2O2S:Pr,Ce,F powder. In the case of sintered materials the emission efficiency from our Lu2O3:Eu5%, Ca was roughly equal to the efficiency of the commercial-sintered Gd2O2S:Pr,Ce,F. The co-doping ions were shown to have various effects on the transparency of the sintered Lu2O3:Eu. Mg hindered the sintering process producing completely opaque pellets. Other ions facilitated the sintering course and the best results were obtained by co-doping the samples with 0.5% of Ba. Sr and La also significantly stimulated the sintering and the final pellets were only slightly cloudy. [Copyright &y& Elsevier]

Uranium(3+) doped Cs2NaYBr6 single crystals with a 2.1 and 0.09 mol% U3+ concentration have been obtained by the Bridgman–Stockbarger method. The U3+ ions replaced the Y3+ ions at an octahedral site of Oh symmetry. Luminescence spectra of the crystal were recorded at 4.2 K. The emission bands observed in the visible and near infrared regions have been assigned to transitions from the lowest components of the 4G7/2 and 4F3/2 multiplets to the crystal-field components of the 4I9/2 ground state. Absorption spectra were recorded in the 3900–35,000 cm−1 range at 4.2 K. The analysis of these spectra enabled the assignement of 28 energy levels, which were fitted to seven parameters of an empirical Hamiltonian representing the combined atomic and crystal-field interactions, with a rms deviation of 43 cm−1. The energies of the most prominent vibronic features have been measured and assigned to the specific vibrational modes of the UCl63− moiety or to lattice modes. Above 14,000 cm−1 vibronic transitions associated with the electric dipole allowed 5f3–5f26d1 transitions were observed. The unresolved zero-phonon lines are accompanied by a number of vibrational progressions combined with the even S1(a1g) mode. [Copyright &y& Elsevier]

The size effect of nanoparticles on optical properties of Lu2O3:Eu3+ was investigated. No pronounced effect was observed for structure of emission spectra. It was found that effect is mainly manifested in the decay profiles of Eu3+ emission. We have noticed that the decay times were almost the same for low concentrations of Eu3+ ions. It is concluded that the size effect is associated with agglomeration of Eu3+ in nanorange particles. [Copyright &y& Elsevier]

Nanoparticulate powders of Eu-doped Lu2O3 were prepared using combustion process and glycine as a fuel. Such powders could be relatively easily sintered to translucent bodies at 1700 °C. Excitation and emission spectra were recorded for both types of the materials. The excitation spectra revealed the existence of much more efficient energy transfer from the host to the dopant in the sintered ceramics. Strong variations in the relative intensities of the excitation transitions are seen when comparing the powder and its sintered analog. This was explained assuming preferential occupation of the C3i site in the glycine-derived powder in comparison with the pellets. Most profound emission under X-ray excitation was found for the sintered ceramic doped with 5% of Eu. [Copyright &y& Elsevier]

Using combustion synthesis and urea as a fuel, Lu2O3 powders were prepared and their morphology defined with HRTEM measurements. The powders were sintered at 1700 °C for 5 h and the microstructure of the obtained ceramics was characterized. It turned out that the as-made powders were strongly agglomerated compositions with a mean particle size of 15–25 nm. High-temperature sintering caused some increase in the size of the crystallites, diameter increased to an average of 25–35 nm. However, domains of about 200–300 nm diameter were formed. These were separated by relatively broad transient regions. The inter-domain regions of rather ample thickness are blamed for relatively high scattering of the sintered ceramic specimens. The formation of the domains is correlated to the existence of agglomerates in the urea-derived nanoparticulate powders. [Copyright &y& Elsevier]

Lu2O3 doped with Eu of varying concentrations was prepared using a convenient combustion technique. Emissions from two different crystallographic sites, C2 and S6, were found and analyzed. Using various spectroscopic techniques, luminescence of Eu3+ exclusively from site C2 or site S6 could be detected. Kinetics of both emissions was characterized and time constants of 1.5 and 4.3 ms were found, respectively. Energy transfer from Eu3+ in site S6 to Eu3+ in site C2 was proved to take place when the dopant content reaches about 1% or higher. For rising activator concentration the transfer becomes more efficient and for heavily doped samples the emission from S6 site lasts in a vestige form only. The only emission transitions detected from Eu in centrosymmetric site S6 were the 5D0–7F1 three-line band. [Copyright &y& Elsevier]

Abstract: La2Hf2O7 nanopowders doped with different Pr concentrations (0.05–10mol.%) were synthesized by the Pechini method. XRD measurements confirmed the single crystalline phase formed already at 800°C and the structure was cubic pyrochlore. Luminescence excitation and emission as well as radioluminescence spectra were recorded for the materials. Both optical and X-ray excitation of La2Hf2O7:Pr produced a red emission resulting from the 4f–4f transitions of Pr3+ ions. Luminescence of materials synthesized at low temperatures was characterized by broadband glass-type emissions, while heat treatment at 1400°C led to spectra showing the typical for crystalline hosts narrow and intense 4f–4f transitions of Pr3+. [Copyright &y& Elsevier]

The aim of this work is to provide a comparative evaluation of luminescence efficiency of Lu 2 O 3 :Eu phosphors screens, in transmission mode, prepared with different grain shape and size, and manufactured by the sedimentation method. More specific, three screens were prepared with spherical grains of size 50 nm, 200 nm and 5 μm. Furthermore, two screens with rod-like shape grains and size of 500 nm and 1–8 μm. The behavior of Absolute Luminescence Efficiency (AE) at low energy X-rays (50 kVp) appeared to differ with the grains size and shape. Furthermore the rod-like grain screens appeared with reduced luminescence efficiency values. [ABSTRACT FROM AUTHOR]

This work is dedicated to the preparation and characterization of the radio-, thermo-, and photoluminescent properties of Lu2O3:Eu and Lu2O3:Tb nanopowder (NPs) scintillators, prepared by means of hydrothermal processing, and their film analogues made of these NPs by the spin coating method. The luminescent properties of NPs and films were characterized by cathodoluminescence (CL), photoluminescence (PL), X-ray excited radioluminescence (RL), and thermoluminescence (TL) at low and high temperatures. In Lu2O3:Eu NPs and films, mostly the luminescence of Eu3+ ions occupying the C2 site of the host, with the most intensive peaks at 611.6 nm and a decay time of 1.5 ms, was observed. On the contrary, two types of Tb3+ centers in the C2 and C3i sites with the main emission lines at 542.4 and 544.0 nm and the corresponding 4f→5d excitation bands at 270 and 305 nm and decay times of t1/e = 2.17 and 3.96 ms were observed in the case of Lu2O3:Tb NPs and films. Indications were noted that Tb3+ in the C3i symmetry position was most active in the CL spectra of Lu2O3:Tb NPs and a respective film. Thermoluminescent peaks at 110 °C and 170 °C for Lu2O3:Eu NPs and at 75 °C and 120 °C in Lu2O3:Tb NPs were observed corresponding to the hole and electron traps, respectively. Significantly different onsets of temperature quenching of Eu3+ and Tb3+ luminescence in Lu2O3:Eu and Lu2O3:Tb NPs were found at ~90 °C and ~320 °C, respectively. [ABSTRACT FROM AUTHOR]

The study concerned with the current work is to provide a comparative investigation of the detective quantum efficiency (DQE) of Lu2O3:Eu phosphor screens, prepared with different grain shape/size grains, specifically spherical grains, with sizes 50 nm, 200 nm, and 5 µm and two screens with rod-like shape grains and sizes 500 nm and 1-8 µm. The phosphors were deposited by the sedimentation method. It was found that the influence of the grains shape on image quality is more important than the grain size. The rod-like grains show higher noise levels, at low frequencies. The influence of grains size, between 50 nm, 200 nm, and 5 µm, is negligible on the normalize noise power spectrum (NNPS) at higher spatial frequencies due to structural non-uniformities. The spherical grains exhibited higher DQE values. [ABSTRACT FROM AUTHOR]

Phase-pure orthorhombic α′- and monoclinic β-Sr2SiO4 and its Ce3+- or Eu2+-doped versions are prepared by reaction of stoichiometric amounts of SrCO3, SiO2, CeO2 or Eu2O3 in the presence of 1 wt% H3BO3 or 1-50 wt% SrCl2 as fluxes in different atmospheres (1200-1400 °C, 4 h; in air, vacuum, 5% H2/N2, or 25% H2/N2). [ABSTRACT FROM AUTHOR]

The present paper concerns the potential use of montmorillonite as a drug carrier and focusses on the intercalation of the studied clay with gentamicin (an aminoglycoside antibiotic) at various temperatures (20, 50 and 80 °C). The experiments were performed to identify the temperature required for the optimum intercalation of gentamicin into the interlayer of montmorillonite. The structural and microstructural properties of gentamicin and the potential for introducing it between smectite clay layers were investigated by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopic techniques, and SEM with EDS analysis. Additionally, the in vitro drug release behaviour of the montmorillonite-gentamicin complex and its antibacterial activity against Escherichia coli ( E. coli ) bacteria was investigated. Based on these studies, the impact of temperature on the intercalation of the drug between layers of smectite was evaluated. It was found that an intercalation temperature of 50 °C resulted in the highest shift in the position of principle peak d (001) as measured by XRD, suggesting, that the greatest amount of gentamicin had been introduced into the interlayer space of montmorillonite at this temperature. Subsequently, the montmorillonite-gentamicin complex material obtained at 50 °C revealed the greatest capacity for killing E. coli bacteria during an in vitro test. [ABSTRACT FROM AUTHOR]

Abstract: Novel materials for regenerative medicine are usually composites or nanocomposites. Their main task is to stimulate damaged tissue for faster regeneration caused by enhanced activity of cells prone to intense proliferation within the defect area. One of the main requirements for such materials is bioactivity, which accelerates fixation between the material and surrounding tissue. After implanting into the body, bioactive materials create new physicochemical bonds between the material and the surrounding tissue. In their case apatite layers are formed on the implant surface without inducing growth of fibrous tissue around them. Some differences in bioactivity phenomena observed on the surface of materials depend on the mechanism of bonding and/or time required to create a new bonding and its strength. In the case of some polymers, especially with highly porous or fibrous structures, the bioactivity phenomenon is initiated by local increase in concentration of calcium and phosphate ions which become nuclei of apatite crystallization. The work presents time-dependent results of interactions between nanocomposite foils and simulation body fluid solution (SBF). Nanocomposite foils were produced from chitosan (CS) and montmorillonite (MMT). The obtained foils, CS and CSM (CS+MMT) were subjected to bioactivity tests by incubation in SBF for different time. FTIR measurements were carried out on an Excalibur spectrometer using ATR method in the wave number region from 550cm−1 to 4000cm−1. The reaction between foils and SBF was analyzed by 2D IR correlation spectroscopy The data obtained show local supersaturation of some characteristic groups in CS-MMT material which seems to be the result of apatite nucleation. [Copyright &y& Elsevier]

Abstract: Bulk alkaline earth fluorides co-doped with optically active ions are prominent materials for luminescent applications. However, for phosphor materials the changeover to the nanoscale is a tightrope walk between achieving desirable features of small particles such as reduced light scattering and unwanted drawbacks such as a high surface defect concentration which is likely to result in quenching of luminescence. A new preparation route via ionic liquids allows obtaining pure and oxygen-free alkaline earth fluorides co-doped with Eu3+ and Gd3+ on the nanoscale with excellent quantum cutting abilities. [Copyright &y& Elsevier]

Abstract: Ca1− x Eu x Al4O7 (x =0, 0.002, 0.01, 0.02, 0.05, 0.1) and Ca1−2 x Eu x Na x Al4O7 (x =0.002, 0.02, 0.05, 0.1) crystalline phosphor powders have been synthesized by modified Pechini method and their spectroscopic properties at room and liquid nitrogen temperature were measured. Excitation spectra of synthesized materials contain broad band attributed to ligand to metal, O2−→Eu3+, charge transfer absorption and narrow lines related to 7F0→5D J , 5H J , 5L J , 5G J transitions of europium ions. Upon excitation at 395nm, the Eu3+-doped calcium dialuminates exhibit red photoluminescence due to parity forbidden f–f intra-configurational transitions with the most intense component at 612nm resulting from the 5D0→7F2 hypersensitive transition. The quantum efficiency of the powders emissions does not exceed 12%. The luminescence decay kinetics reveals that some quenching appears for higher concentrations. Site selective spectroscopy disclosed the presence of at least two well defined individual spectroscopic sites of Eu3+ and increasing disturbance of their local symmetries with raising concentration of the activator was observed. The increasing symmetry disorder led to a significant asymmetrical broadening of the luminescence lines at higher concentrations. Concentration dependence of the luminescence kinetics of the two diverse Eu3+ ions is different, as only one of them, with the characteristic luminescence at 579.5nm, exhibits shortening of the decay time at higher Eu contents. The inexpensive CaAl4O7:Eu powders are potentially good candidates for photonics applications. For Eu, Na co-doped powders the Eu3+ ions producing emission at 579.7nm dominates strongly over those with luminescence at 577.2nm. [Copyright &y& Elsevier]