1,721,012 research outputs found
Spectroscopic investigations of nanostructured LiNbO3 doped with Eu3+
No full textStructural and optical properties of the sol-gel derived nanocrystalline lithium niobate (LiNbO3) powders doped with Eu3+ ions have been studied. In particular, the influence of the sizes of nanoparticles controlled by temperature on the structural and luminescence properties has been investigated. Emission bands corresponding to 5D0 emission became more resolved with increasing nanocrystal size and changed to a typical Eu3+:LiNbO3 single crystal spectrum for nanocrystals having an average size of more than 40 nm. Nonlinear optical properties of nanostructured LiNbO3 have been confirmed by simple observation of second harmonic generation effect (SHG). The possibility of using nanostructured LiNbO3 doped with rare-earth ions as self-doubling elements in integrated optoelectronic devices has been discussed
Effect of Ce3+ concentration on persistent luminescence of YAGG:Ce3+,Cr3+,Nd3+ nanophosphors obtained by the co-precipitation method
No full textSynthesis of Y3Al2Ga3O12 garnet (YAGG) nanophosphors co-doped with Ce3+, Cr3+, and Nd3+ ions by co-precipitation is reported. The effect of Ce3+ concentration on the structure of garnet and on optical properties including persistent luminescence was investigated. The X-ray diffraction measurements showed that single garnet phase was obtained. The contraction of the crystallites size was observed with increasing the cerium concentration. The combined emission of three used co-dopants together allows to extend persistent luminescence spectral range. The photoluminescence, excitation and persistent luminescence spectra were collected and the optimal Ce3+ concentration for the highest efficiency conversion of UV and blue light into the red and the near infrared emission was determined. Based on thermoluminescence data, the effect of Ce3+ concentration on the traps redistribution was also investigated
Luminescent YPO4:Eu@PVA dispersions for anti-counterfeiting ink applications
No full textA method was developed to obtain YPO4:Eu dispersions of PVA as a luminescent inks. YPO4:Eu nanoparticles were prepared by precipitation followed by hydrothermal treatment. The dispersion preparation included systematic studies to prepare a stable colloidal system and to investigate the role of parameters affecting its stability and UV-excited YPO4:Eu emission intensity. The effect of PVA concentration was studied in detail for two different PVAs to determine the optimal parameters for its use as ink with specific luminescent properties. The type of interactions responsible for the dispersion stability was also investigated
Controlling a defect structure of the ZnGa2O4:Cr3+ spinel through synthesis parameters for persistent luminescence optimization
No full textZnGa2O4:Cr3+ (ZGO:Cr) is one of the most promising red persistent phosphors for in-vivo imaging due to its
650–750 nm emission band in the range of the so-called first biological window. In this paper, we report on how
to control the high brightness persistent luminescence of the smallest ZGO:Cr nanoparticles by optimization of
hydrothermal synthesis parameters. The influence of pH solution, the temperature of synthesis, and calcination
on the degree of inversion, lattice parameters, morphology, and crystallite size were systematically investigated.
The results have shown that different synthesis conditions modify the trap depths distribution, by mixing the
occupancy of Zn2+ and Ga3+ sites in the spinel structure, which affects the duration and intensity of persistent
luminescence. The correlation between structural changes and optical properties is established and it is possible
to control them by selecting the appropriate hydrothermal synthesis parameters
Multimodal anti-counterfeiting inks: modern use of an ancient pigment in synergy with a persistent phosphor
No full textMulti-level luminescent, transparent and non-permanent inks for anti-counterfeiting systems and security were developed. The inks emit radiation at different wavelengths based on the type of radiation used to illuminate them, providing multiple layers of safety. The red persistent phosphor Y2O2S:Eu3+,Mg2+,Ti4+ (YOS) was mixed with Egyptian Blue (EB) and dispersed in an aqueous solution of arabic gum. Imaging techniques, excitation and emission spectra, the study of luminescence over time and the duration time were used to verify that the obtained systems showed the desired optical characteristic both in the infrared and in the visible spectral ranges. The two luminescent materials act synergistically: when illuminated with UV light, YOS emits red photons over time and EB, absorbing this energy, emits infrared photons. The resulting emission characteristics are non-obvious and can be designed at the ink developing stage. The tests performed on several substrates showed that the developed luminescent inks are well suited for use in the field of security and anti-counterfeiting
Structural and luminescence properties of Eu3+ doped BaxSr1−xTiO3 (BST) nanocrystalline powders prepared by different methods
No full textEu3+ doped BaxSr1-xTiO3 (BST) nanocrystalline powders have been prepared using molten salts, sol-gel and hydrothermal techniques in order to compare their structural and luminescence properties. The sizes of the particles are around 50 nm for the BST powders obtained by the sol-gel and hydrothermal methods while they are around 400 nm for the samples prepared by the molten salts method. The Eu3+ doped BST samples show strong emission in the visible range. The luminescence spectra of the Eu3+ ions for the investigated samples depend strongly upon the preparation method. The luminescence bands are affected by a notable amount of inhomogeneous broadening. The broadening of the emission bands and the non-exponential behavior of the emission decay curves point to the presence of significant structural disorder
Comment on "Colossal dielectric and magnetodielectric effect in Er(2)O(3) nanoparticles embedded in a SiO(2) glass matrix"
No full textIn a recent paper, Mukherjee et al. [Phys. Rev. B 82, 104107 (2010)] reported a colossal enhancement of dielectric constant along with magnetodielectric (MD) behavior in a SiO2-Er2O3 system synthesized via the sol-gel route. In the opinion of the authors of the criticized paper, such a colossal MD effect in the measured samples is a direct consequence of exploiting magnetoresistance changes associated with the size and concentration of Er2O3 nanoparticles. We point out that the disappearing MD behavior depends on the crystallite size and dopant concentration, as shown by the authors of the criticized paper, but also on the nature and the crystal structure of the compound
Preparation and upconversion properties of Er3+,Yb3+:Y2Si2O7 nanocrystallites embedded in PVA polymer nanocomposites
No full textThe preparation of polymer nanocomposites consisting of a poly(vinyl) alcohol (PVA) network and RE3+: Y2Si2O7 nanocrystalline particles (RE = Yb, Er) is presented. Optical properties of the nanocomposites were preliminarily studied. In particular, efficient upconversion was observed in Er3+ and Yb3+, co-doped Y2Si2O7 nanoparticles embedded in the polymeric PVA host. It was found that the luminescence features of the RE3+: Y2Si2O7 nanoparticles were affected by the polymeric host, resulting in a shortening of their luminescence lifetimes. This effect is discussed in terms of the effective refractive index
Infrared induced red luminescence of Eu3+-doped polycrystalline LiNbO3
No full textPolycrystalline lithium niobate powders were prepared by the sol-gel method. Different grain sizes were obtained by controlling the annealing temperature. The Eu3+ ion was used as a luminescent probe of the nonlinear optical properties of the grains. Strong red emission deriving from Eu3+ ions was observed under pulsed infrared laser irradiation at 936.0 nm due to absorption of the light produced in the second harmonic generation process. A measurable emission was observed only for grains having a size of the least 200 nm, depending on the annealing temperatur
Composite Nanostructures for the Production of White Light
No full textIn this work, two different composite nanostructures, YAG:Ce and Ga0.9In0.1N, were prepared by the Urea Glass Route method and tested for the production of white light. The first composite was prepared by synthetizing the Ga0.9In0.1N nanoparticles in the presence of YAG:Ce nanoparticles. The second one was prepared by synthetizing YAG:Ce nanoparticles in the presence of Ga0.9In0.1N nanoparticles. These systems can be useful for the production of white light. X-ray Diffraction and Transmission and Scanning Electron Microscopies (TEM and SEM) were used to evaluate their structural and morphological properties. Excitation and emission spectra, the quantum yield and colour of the emitted light were acquired to evaluate the optical properties of the systems
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