Rare earth doped organic–inorganic hybrid polyhedral oligomeric silsesquioxane phosphors applied for flexible sheet and anti-counterfeiting

We have developed organic–inorganic hybrid polyhedral oligomeric silsequioxane (POSS) type monomer ligand 2,6-pyridinediamine-bis-propanylheptaisobutyl POSS (PDC-POSS) and synthesized rare earth (RE =Eu3+) doped hybrid complex PDC-POSS phosphors. The PDC-POSS precursor was prepared using (3-aminopropyl)heptaisobutyl POSS, 2,6-pyridinedicarboxylic acid chloride (PDC) as the host material, and then coordinated with RE3+ using europium nitrate regents to synthesize PDC-POSS:Eu3+ phosphors. The photoluminescence (PL) spectra of the PDC-POSS:Eu3+ hybrid phosphors were detected at 592, 616, 649, 693 nm under UV light (λ= 288 nm) excitation. In addition, the synthesized hybrid phosphors showed red light emission under UV light. The phosphors were demonstrated on a flexible sheet that could be applied for red emitting LEDs, and for anti-counterfeiting, which requires the film to remain hidden and identifiable only by UV light.

Analysis of structural, morphological and magnetic properties of diluted magnetic semiconductor ZnO:Eu obtained by combustion reaction

Eu-doped semiconductor matrix of ZnO at concentrations of 0.05 and 0.10 mols was synthesized by combustion reaction, using zinc nitrate, europium nitrate, and urea as fuel. In order to analyze the effect of europium concentration and sintering on the structure, band gap, magnetic and morphological properties of ZnO, the samples were sintered at 1100 °C for 30 min and analyzed before and after sintering via X-ray diffraction, ultraviolet and visible spectroscopy, vibrant sample magnetometry, and scanning electron microscopy. From the results obtained, it was found that there was the formation of the semiconductor phase ZnO and also a second-phase (Eu2O3). It was observed that the samples before and after sintering presented band gap values within the semiconductor range and ferromagnetism at room temperature.

Differences in Emission Properties for Triboluminescent EuD4TEA Synthesized Using Europium Nitrate or Europium Acetate

Europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA) is one of the most intense triboluminescent (TL) materials currently known. It was recently reported that the triboluminescent yield was increased by 82% by changing the starting europium salt from europium chloride to europium nitrate. Unfortunately, europium nitrate has been classified as a hazardous material that cannot be shipped by air, which limits the availability of manufacturers and increases the cost. In an effort to further reduce the synthesis cost of EuD4TEA, we explore the effects of europium acetate on the triboluminescent properties of EuD4TEA by comparing the triboluminescent yield. The photoluminescent spectra as well as crystal structure using an optical microscope will also be explored.

Luminescent Properties of Eu3+-Doped Hybrid SiO2-PMMA Material for Photonic Applications

Hybrid organic-inorganic materials are of great interest for various applications. Here, we report on the synthesis and optical characterization of silica-PMMA samples with different Eu3+ molar concentrations. The optical properties of this material make it suitable for photonic applications. The samples were prepared using the sol-gel method, mixing tetraethyl orthosilicate (TEOS) as a silica glass precursor and methyl methacrylate (PMMA) as a polymer component. Europium nitrate pentahydrate was then added in six different molar concentrations (0.0, 0.1, 0.25, 0.5, 0.75, and 1%) to obtain as many different samples of the material. The absorption spectra were obtained applying the Kubelka–Munk formula to the diffuse reflectance spectra of the samples, all in the wavelength range between 240 and 2500 nm. The emission and excitation measurements were made in the visible range. Five bands could be identified in the emission spectra, related to electronic transitions of the ion Eu3+ (4D0→7Fi, i from 0 to 4). In the excitation spectra, the following bands were detected: 7F0→5G3 (379 nm), 7F0→5G2 (380 nm), 7F0→5L6 (392 nm), 7F0→5D3 (407 nm), 7F0→5D2 (462 nm), and 7F0→5D1 (530 nm). The emission decay times were measured for the different samples and showed an inverse dependence with the Eu3+ concentration.

Spectroscopic Studies of the Behavior of Eu3+on the Luminescence of Cadmium Tellurite Glasses

The effect of europium doping on the photoluminescence of ZnO-CdO-TeO2glasses is analyzed. TeO2-based glasses are of high interest as hosts for laser glasses. The Eu-doped oxide glasses were prepared by the conventional melt-quenching method. Five different concentrations of europium nitrate hexahydrate that varied from 0.3 to 1.5 mol% were used. SEM observations revealed the formation of zinc aluminate spinel and disperse droplets of liquid-liquid phase separation in the glasses. X-Ray diffraction reveals the amorphous structure of the fabricated glasses. FT-IR and Raman spectra show the presence of TeO4and TeO3+1/TeO3units that conform with the glass matrix. Raman spectra evidenced a band located at 1556 cm−1that can be related to interstitial molecular oxygen in the glass matrix. Photoluminescence of the glasses showed light emission due to the following europiumtransitions from itsD52,D51, andD50levels to itsF7Jmanifolds:D52→F70(468 nm),D52→F72(490 nm),D52→F73(511 nm),D51→F71(536 nm),D51→F72(554 nm),D50→F70(579.5 nm),D50→F71(592 nm),D50→F72(613 nm),D50→F73(652 nm), andD50→F74(490 nm). The estimated decay time,τ, was 0.4 ms for all the glasses.