Blue upconversion enhancement by a factor of 200 in Tm 3+-doped tellurite glass by codoping with Nd 3+ ions

We investigated near-infrared-to-blue upconversion from thulium (Tm 3+) doped in tellurite glasses upon continuous wave excitation near 800 nm. We observed an enhancement of over two orders of magnitude of the upconverted emission at ∼480nm when neodymium (Nd 3+) ions were codoped with Tm 3+ ions. For comparison, using a Tm 3+:Nd 3+ codoped fluorozirconate glass as a reference material we observed a 40-fold enhancement of the blue emission. Analysis of the blue emission for samples with different doping levels of Nd 3+ ions showed that energy transfer between Nd 3+ and Tm 3+ is the mechanism responsible for the enhancement in upconversion. © 2002 American Institute of Physics. © 2002 American Institute of Physics.

Frequency upconversion in rare-earth doped fluoroindate glasses

We present recent results on frequency upconversion (UPC) obtained in fluoroindate glasses (FIG) doped with Ho3+, Tm3+ and Nd3+ ions and codoped with Pr3+/Nd3+ and Yb3+/Tb3+ ions. The results for the Ho3+-doped samples show strong evidence of energy transfer (ET) between Ho3+ ions resonantly excited at 640 nm. The origin of the blue-green upconverted fluorescence observed was identified and the dynamics of the signals revealed the pathways involved in the UPC process. In the case of Tm3+-doped FIG, the samples were resonantly excited at 650 nm and the main mechanism that contributes for the red-to-blue upconversion is excited-state absorption (ESA). The FIG samples codoped with Pr3+/Nd3+ were excited at 588 nm in resonance with transitions starting from the ground state of the Nd 3+ and the Pr3+ ions. It was observed that the presence of Nd3+ ions enhanced the Pr3+ emission at 480 nm by two orders of magnitude. Multiphonon (MP)-assisted upconversion is also discussed for Nd3+-doped FIG pumped at 866 nm. Emission at 750 nm with a peculiar linear dependence with the laser intensity was observed and explained. A rate-equation model that includes MP absorption via thermally coupled electronic excited states of Nd3+ was developed and describes well the experimental results. The role played by effective phonon modes is clearly demonstrated. MP-assisted UPC process was also studied in Yb3+/ Tb3+-codoped FIG samples excited at 1064 nm, which is off-resonance with electronic transitions starting from the ground state. It was determined that the mechanism leading to Tb3+ emission in the blue is due to ET from a pair of excited Yb3+ ions followed by ESA in the Tb 3+ ions. © 2002 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS.

Spectroscopic properties of Tm3+ doped fluoroindate glass

Optical absorption and fluorescence were investigated in Tm3+ doped fluoroindate glass. The spectroscopic parameters for transitions in the 4f11 configuration were determined. The fluorescence study revealed the origin of the frequency upconversion process as well as allowed to quantify the interaction between Tm3+ ions.

Red, green, and blue upconversion luminescence in ytterbium-sensitized praseodymium-doped lead-cadmium-germanate glass

Blue, green, red, and near-infrared upconversion luminescence in the wavelength region of 480 - 740 nm in Pr3+/Yb3+-codoped lead-cadmium-germanate glass under 980 nm diode laser excitation, is presented. Upconversion emission peaks around 485, 530, 610, 645, and 725 nm which were ascribed to the 3P0 - 3HJ (J=4, 5, and 6), and 3P0 - 3FJ (J=2, and 3,4), transitions, respectively, were observed. The population of the praseodymium upper 3P0 emitting level was accomplished through a combination of ground-state absorption of Yb3+ ions at the 2F7/2, energy-transfer Yb3+(2F 5/2) Pr3+(3H4), and excited-state absorption of Pr3+ ions provoking the 1G4 - 3P0 transition. The dependence of the upconversion luminescence upon the Yb3+-concentration and diode laser power, is also examined, in order to subsidize the proposed upconversion excitation mechanism.

Electrical devices obtained from polymeric precursors process

Nowadays, many investments have been made in the area of superconductor materials, with the aim to improve their potential technological applications. Applications on the energy transport using cables, to get high resolution images in the medicine use high magnetic fields, high speed signals use superconductor devices all of them are in crescent evidence and they are showing that the future is coming and next for this new kind of materials. Obviously that everything of this is possible due to the increasing of research with new materials, where the synthesis, characterization and applications are of the mainly objective of these researches. The production of cable for the energy transport has been in advanced stage as the bulks production is too. However, the film production that to aim at the electronic devices area is not as developed or it still need expensive investments. Thinking about that, we are developing a research where we may increase the relation of cost/benefits. Thereby, we are applying the polymeric precursors method to obtain films that will be used in the built of electronic devices. Thin films (mono and multilayers, on crystalline or metallic substrates, controlled thickness) of the BSCCO system have been obtained from dip coating deposition process with excellent results in terms of preferential orientation, controlled thickness, a large area, which may indicate future applications. Based on these results, we present an electrical circuit and their principal characteristics as superconductor transition (85K), transport current density and structure. DC four probes method, scanning electron microscopy, digital optical microscopy and X-ray diffractometry were some techniques used for the characterization of this superconductor electric device. © 2006 Materials Research Society.

The nuclear matter effects in π0 photoproduction at high energies

The in-medium influence on π0 photoproduction from spin zero nuclei is carefully studied in the GeV range using a straightforward Monte Carlo analysis. The calculation takes into account the relativistic nuclear recoil for coherent mechanisms (electromagnetic and nuclear amplitudes) plus a time dependent multi-collisional intranuclear cascade approach (MCMC) to describe the transport properties of mesons produced in the surroundings of the nucleon. A detailed analysis of the meson energy spectra for the photoproduction on 12C at 5.5 GeV indicates that both the Coulomb and nuclear coherent events are associated with a small energy transfer to the nucleus (≲ 5 MeV), while the contribution of the nuclear incoherent mechanism is vanishing small within this kinematical range. The angular distributions are dominated by the Primakoff peak at extreme forward angles, with the nuclear incoherent process being the most important contribution above θπ0 ≲ 20. Such consistent Monte Carlo approach provides a suitable method to clean up nuclear backgrounds in some recent high precision experiments, such as the PrimEx experiment at the Jefferson Laboratory Facility.

Structural control of photoluminescence of four poly(urethane-urea-co-1,3,5-triazine)s: Synthesis and characterization

A series of segmented poly(urethane-urea)s containing 1,3,5 triazine in the hard block and hexamethylene spacers in the soft block was prepared. The hard to soft segment ratio was varied systematically, to afford a series of polymers in which the chromophore concentration varied from 4.2% to 18.1%. Although triazine emission is located in the UV region, the films with higher content of the chromophore emitted a visible blue light (425 nm) when excited at the very red-edge of the absorption band. The photophysical properties of the materials were strongly dependent on the relative amount of triazine moieties along the main chain. Isolated moieties emit in copolymers with small amount of triazine groups, indicating that even though in solid state, these moieties tend to be apart. Two photophysical consequences were observed when the amount of triazine increases: there is some energy transfer process involving isolated moieties with consequent decrease of the lifetime and an additional red-edge emission attributed to aggregated lumophores. The mono-exponential decay observed for the isolated form is substituted by a bi-exponential decay of the aggregated species. The materials were not strong emitters, but since the N-containing triazine moieties are good electron transport groups, the polymers have potential application as electron transport enhancers in various applications. © 2006 Elsevier B.V. All rights reserved.

Efficient UV-visible upconversion luminescence and thermal effects in terbium-ytterbium codoped fluorogermanate vitroceramic

Cooperative energy-transfer upconversion luminescence in Tb 3+/Yb 3+-codoped PbGeO 3-PbF 2-CdF 2 vitroceramic and its precursor glass under resonant and off-resonance infrared excitation, is investigated. Bright UV-visible emission signals around 384, 415, 438 nm, and 473-490, 545, 587, and 623 nm, identified as due to the 5D 3( 5G 6 → 7F J(J=6,5,4) and 5D 4 → 7F J(J=6,5,4,3) transitions, respectively, were readily observed. The results indicate that cooperative energy-transfer between ytterbium and terbium ions followed by excited-state absorption are the dominant upconversion excitation mechanisms herein involved. The comparison of the upconversion process in a vitroceramic sample and its glassy precursor revealed that the former present much higher upconversion efficiency. The dependence of the upconversion emission upon pump power, temperature, and doping content is also examined.

Upconversion ultraviolet random lasing in Nd 3+ doped fluoroindate glass powder

An upconversion random laser (RL) operating in the ultraviolet is reported for Nd 3+ doped fluoroindate glass powder pumped at 575 nm. The RL is obtained by the resonant excitation of the Nd 3+ state 2G 7/2 followed by energy transfer among two excited ions such that one ion in the pair decays to a lower energy state and the other is promoted to state 4D 7/2 from where it decays emitting light at 381 nm. The RL threshold of 30 kW/cm 2 was determined by monitoring the photoluminescence intensity as a function of the pump laser intensity. The RL pulses have time duration of 29 ns that is 50 times smaller than the decay time of the upconversion signal when the sample is pumped with intensities below the RL laser threshold. © 2011 Optical Society of America.

State Dependent Riccati Equation (SDRE) control method applied in cancellation of a parametric resonance in a magnetically levitated body

Here, a simplified dynamical model of a magnetically levitated body is considered. The origin of an inertial Cartesian reference frame is set at the pivot point of the pendulum on the levitated body in its static equilibrium state (ie, the gap between the magnet on the base and the magnet on the body, in this state). The governing equations of motion has been derived and the characteristic feature of the strategy is the exploitation of the nonlinear effect of the inertial force associated, with the motion of a pendulum-type vibration absorber driven, by an appropriate control torque [4]. In the present paper, we analyzed the nonlinear dynamics of problem, discussed the energy transfer between the main system and the pendulum in time, and developed State Dependent Riccati Equation (SDRE) control design to reducing the unstable oscillatory movement of the magnetically levitated body to a stable fixed point. The simulations results showed the effectiveness of the (SDRE) control design. Copyright © 2011 by ASME.

On nonlinear dynamics in a free fluid surface of a tank excited by a non-ideal power source

We investigate the nonlinear oscillations in a free surface of a fluid in a cylinder tank excited by non-ideal power source, an electric motor with limited power supply. We study the possibility of parametric resonance in this system, showing that the excitation mechanism can generate chaotic response. Additionally, the dynamics of parametrically excited surface waves in the tank can reveal new characteristics of the system. The fluid-dynamic system is modeled in such way as to obtain a nonlinear differential equation system. Numerical experiments are carried out to find the regions of chaotic solutions. Simulation results are presented as phase-portrait diagrams characterizing the resonant vibrations of free fluid surface and the existence of several types of regular and chaotic attractors. We also describe the energy transfer in the interaction process between the hydrodynamic system and the electric motor. Copyright © 2011 by ASME.

Purification, characterization, and specificity determination of a new serine protease secreted by penicillium waksmanii

The purpose of this work was to purify a protease from Penicillium waksmanii and to determine its biochemical characteristics and specificity. The extracellular protease isolated that was produced by P. waksmanii is a serine protease that is essential for the reproduction and growth of the fungus. The protease isolated showed 32 kDa, and has optimal activity at pH 8.0 and 35 C towards the substrate Abz-KLRSSKQ-EDDnp. The protease is active in the presence of CaCl2, KCl, and BaCl, and partially inhibited by CuCl2, CoCl2 and totally inhibited by AlCl3 and LiCl. In the presence of 1 M urea, the protease remains 50 % active. The activity of the protease increases 60 % when it is exposed to 0.4 % nonionic surfactant-Triton X-100 and loses 10 % activity in the presence of 0.4 % Tween-80. Using fluorescence resonance energy transfer analysis, the protease showed the most specificity for the peptide Abz-KIRSSKQ-EDDnp with k cat/K m of 10,666 mM-1 s-1, followed by the peptide Abz-GLRSSKQ-EDDnp with a k cat/K m of 7,500 mM -1 s-1. Basic and acidic side chain-containing amino acids performed best at subsite S1. Subsites S2, S3, S′ 2, and S′ 1, S ′ 3 showed a preference for binding for amino acids with hydrophobic and basic amino acid side chain, respectively. High values of k cat/K m were observed for the subsites S2, S3, and S′ 2. The sequence of the N-terminus (ANVVQSNVPSWGLARLSSKKTGTTDYTYD) showed high similarity to the fungi Penicillium citrinum and Penicillium chrysogenum, with 89 % of identity at the amino acid level. © 2012 Springer Science+Business Media New York.

Strongly luminescent, highly ionic europium in a lanthanum diphenylphosphinate matrix

A series of insoluble, chemically inert and thermally stable compounds La1-xEux(DPP)3 (x = 0.50, 0.20, 0.10, and 0.050; DPP = diphenylphosphinate) was synthesized and characterized by elemental and thermogravimetric analysis, FT Infrared spectroscopy and X-ray powder diffraction. Luminescence spectroscopy at both 77 and 298 K showed changes in the intensity of the hypersensitive transition 5D 0 → 7F2 of Eu3+ which are dependent of the excitation wavelength, suggesting that the europium occupies two different sites in the compounds. The large quantum efficiency and quantum yield, as well as the long radiative lifetime of the 5D0 Eu3+ level of the series of compounds, which are desirable qualities for light-conversion molecular devices, are discussed in terms of the interactions and the energy transfer process between the ligands and the metal ion. © 2012 Elsevier B.V. All rights reserved.

First crystal structures of lanthanide-hydrocinnamate complexes: Hydrothermal synthesis and photophysical studies

Five new lanthanide(III) complexes of hydrocinnamic acid (Hcin), [Ln(cin)3(H2O)3]·3Hcin (Ln = Tb(III) (1), Dy(III) (2), Er(III) (3), Eu(III) (4) and Gd(III) (5)) have been synthesized and characterized. The X-ray structures of 1-5 reveal that all compounds are isostructural and that each lanthanide ion is nine-coordinated by oxygen atoms in an overall distorted tricapped trigonal-prismatic geometry. Six oxygen atoms are provided by carboxylate moieties, and the other three by water molecules. The supramolecular architectures of 1-5 show the presence of uncoordinated hydrocinnamic acid molecules which induce the formation of numerous hydrogen bonds. The photophysical properties of these complexes in the solid state at room temperature were studied using diffuse reflectance (DR), fluorescence excitation and emission spectra. An energy level diagram was used to establish the most relevant channels involved in the ligand-to-metal energy transfer, indicating that cin- ligands can act as intramolecular energy donors for Tb(III), Dy(III) and Eu(III) ions. © 2012 Elsevier B.V.

Upconversion luminescence in Er3+ doped Ga10Ge 25S65 glass and glass-ceramic excited in the near-infrared

The infrared-to-visible frequency upconversion was investigated in Er 3+-doped Ga10Ge25S65 glass and in the transparent glass-ceramic obtained by heat-treatment of the glass above its glass-transition temperature. Continuous-wave and pulsed lasers operating at 980 nm and 1480 nm were used as excitation sources. The green (2H 11/2 → 4I15/2; 4S3/2 → 4I15/2) and red (4F9/2 → 4I15/2) photoluminescence (PL) signals due to the Er3+ ions were characterized. The PL decay times were influenced by energy transfer among Er3+ ions, by cross-relaxation processes and by energy transfer from the Er3+ ions to the host material. The PL from the Er3+ ions hosted in the crystalline phase was distinguished only when the glass-ceramic was excited by the 1480 nm pulsed laser. The excitation pathways responsible for the green and red PL bands are discussed to explain the differences between the spectra observed under continuous-wave and pulsed excitation. © 2013 American Institute of Physics.