Time filter

Source Type

Lukowiak A.,CNR Institute for Photonics and Nanotechnologies | Lukowiak A.,Institute of Low Temperature And Structure Research | Wiglusz R.J.,Institute of Low Temperature And Structure Research | Chiappini A.,CNR Institute for Photonics and Nanotechnologies | And 6 more authors.
Journal of Non-Crystalline Solids | Year: 2014

Nanoparticles of lithium lanthanum tetraphosphates doped with different concentration of Eu3 + ions were synthesized. The selected tetraphosphate was used to fabricate a transparent composite where nanocrystals were immobilized in a sol-gel-derived silica-hafnia amorphous film. The structural and spectroscopic properties of the systems were investigated by XRD analysis, Raman spectroscopy, and photoluminescence measurements. For all the samples with the Eu3 + ions concentration from 1 to 100 mol% the monoclinic structure with a space group C12/c1 was determined. The mean diameter of nanocrystals determined by Scherrer equation was in the range of 40-55 nm. The luminescence of 10%Eu3 +:LiLa(PO3)4 in silica-hafnia matrix indicated the immobilization of Eu3 + ions into a distorted environment. The dependence of both luminescence intensity and lifetime on the Eu3 + concentration demonstrated effective reduction of concentration quenching in the tetraphosphate nanopowders. © 2013 Elsevier B.V.


Lukowiak A.,Institute of Low Temperature And Structure Research | Marciniak L.,Institute of Low Temperature And Structure Research | Vasilchenko I.,CNR Institute for Photonics and Nanotechnologies | Vasilchenko I.,University of Trento | And 7 more authors.
International Conference on Transparent Optical Networks | Year: 2016

A group of nanocrystalline polyphosphates is presented showing the advantages arising from their spectroscopic properties. Their unique optical features are related, among others, with their structural properties. For example, reduced cross relaxation processes between doped lanthanide ions are observed in tetraphosphate matrices due to the relatively large active ions distance. For selected praseodymium doped polyphosphates, such as LiPr(PO3)4, a cascade emission transitions can be observed due to the two-step 4f2 transitions that take place under UV excitation into 4f5d levels. Such property could be used for scintillation devices. Other interesting behavior is the efficient anti-Stokes white broadband emission induced by NIR laser diode in LiYb(PO3)4 nanocrystals. Additionally, the properties of planar waveguides based on SiO2-HfO2 system and doped with P2O5 or tetraphosphate nanocrystals are presented. © 2016 IEEE.


Zmojda J.,University of Bialystok | Kochanowicz M.,University of Bialystok | Miluski P.,University of Bialystok | Lukowiak A.,Institute of Low Temperature And Structure Research | And 9 more authors.
International Conference on Transparent Optical Networks | Year: 2016

In this article we present possibility of obtaining nano-phase structures in glasses and optical fibers doped with RE ions. Effect of phosphate on structural and optical properties of antimony-germanate glasses doped with Eu3+ions have been investigated. Modification of Sb2O3 - GeO2 - SiO2 - Al2O3 - Na2O glass system by P2O5 (up to 10 mol.%) shows possibility of creation of the EuPO4 phosphate nanophase. Controlled heat-treatment process selected glasses are used as a core of optical fiber. The luminescence spectra of glass, glass-ceramics and optical fibers were compared and discussed in terms of embedding nano-crystalline phase structures in RE - doped optical fiber. © 2016 IEEE.


Ristic D.,Ruder Boskovic Institute | Guddala S.,Indian Institute of Technology Kanpur | Chiappini A.,CNR Institute for Photonics and Nanotechnologies | Alombert Goget G.,University Claude Bernard Lyon 1 | And 7 more authors.
Journal of Applied Physics | Year: 2015

The thermo-optic coefficient of tin-oxide thin films on silicon substrates was measured using fixed wavelength ellipsometry. The applicability of ellipsometry for these measurements is discussed with special considerations to the problem of measurement of the thermo-optic coefficient of materials with very low values of the thermo-optic coefficient (<2 × 10-5). The effect of thermal annealing on the thermo-optic coefficient and on the film-substrate boundary properties of the tin oxide film is also discussed. © 2015 AIP Publishing LLC.


Valligatla S.,CNR Institute for Photonics and Nanotechnologies | Valligatla S.,University of Trento | Valligatla S.,University of Hyderabad | Chiasera A.,CNR Institute for Photonics and Nanotechnologies | And 12 more authors.
Optical Materials | Year: 2015

We report on optical field enhanced nonlinear absorption and on the optical limiting properties of a 1-D photonic crystal with ZnO defect, fabricated by rf sputtering technique. The structural properties of the photonic crystal are studied using scanning electron microscopy (SEM) images. Light transmission spectroscopy measurement shows a broad photonic band gap with a defect mode. Open aperture Z-scan measurement with 532 nm pulsed laser illustrates a four times enhancement in the nonlinear absorption coefficient, due to local field enhanced two-photon absorption in the photonic crystal structure with respect to the single layer of ZnO reference. The enhancement of the nonlinear absorption in the photonic crystal, due to the strong confinement of the optical field around ZnO defect layer, leads to an optical power limiting behavior in the photonic crystal. The limiting threshold of the photonic crystal is found to be 0.74 J/cm2 @ 532 nm with 6 ns pulse width, 10 Hz repetition rate. © 2015 Published by Elsevier B.V.


Berneschi S.,Centro Of Studi E Ricerche Enrico Fermi | Berneschi S.,CNR Institute of Neuroscience | Chiappini A.,CNR Institute for Photonics and Nanotechnologies | Ferrari M.,CNR Institute for Photonics and Nanotechnologies | And 2 more authors.
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2011

Aim of this paper is to present a short review of the main results obtained in our laboratories on Er3+-doped SiO2: HfO2 glass ceramic waveguides fabricated by sol-gel route and dip-coating technique, employing either top-down or bottom-up approach. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Farnesi D.,CNR Institute of Neuroscience | Farnesi D.,University of Florence | Barucci A.,CNR Institute of Neuroscience | Berneschi S.,CNR Institute of Neuroscience | And 7 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Microbubble resonators (MBRs) combine the unique properties of whispering gallery mode resonators with the intrinsic capability of integrated microfluidics. Here an improved fabrication method of MBRs is presented, based on the heating of a slightly pressurized capillary by a rotating arc discharge. Rotation of the electrodes ensures an homogeneous distribution of the heat all over the capillary surface. The demonstrated MBRs have Q factors up to 10 7 at 773 nm. Microbubbles were filled with water and aqueous solutions of ethanol in order to test the refractive index sensing capabilities of such resonators, which also show a good temporal stability. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).


Dinuzzo M.,Centro Of Studi E Ricerche Enrico Fermi | Giove F.,Centro Of Studi E Ricerche Enrico Fermi | Giove F.,University of Rome La Sapienza | Maraviglia B.,Centro Of Studi E Ricerche Enrico Fermi | And 2 more authors.
Journal of Neurochemistry | Year: 2013

The non-metabolizable fluorescent glucose analogue 6-(N-(7-nitrobenz-2-oxa- 1,3-diazol-4-yl)amino)-2-deoxyglucose (6-NBDG) is increasingly used to study cellular transport of glucose. Intracellular accumulation of exogenously applied 6-NBDG is assumed to reflect concurrent gradient-driven glucose uptake by glucose transporters (GLUTs). Here, theoretical considerations are provided that put this assumption into question. In particular, depending on the microscopic parameters of the carrier proteins, theory proves that changes in glucose transport can be accompanied by opposite changes in flow of 6-NBDG. Simulations were carried out applying the symmetric four-state carrier model on the GLUT1 isoform, which is the only isoform whose kinetic parameters are presently available. Results show that cellular 6-NBDG uptake decreases with increasing rate of glucose utilization under core-model conditions, supported by literature, namely where the transporter is assumed to work in regime of slow reorientation of the free-carrier compared with the ligand-carrier complex. To observe an increase of 6-NBDG uptake with increasing rate of glucose utilization, and thus interpret 6-NBDG increase as surrogate of glucose uptake, the transporter must be assumed to operate in regime of slow ligand-carrier binding, a condition that is currently not supported by literature. Our findings suggest that the interpretation of data obtained with NBDG derivatives is presently ambiguous and should be cautious because the underlying transport kinetics are not adequately established. In this study, we used the four-state carrier model for brain GLUT1 to examine whether cellular glucose metabolism can be inferred from the accumulation of the fluorescent glucose analogue 6-NBDG, which is increasingly employed for indirect determination of glucose transport and utilization in neurons and astrocytes. However, our findings show that the relation between 6-NBDG uptake and glucose transport and utilization configures antiport not symport of the two substrates. © 2013 International Society for Neurochemistry.


Berneschi S.,Centro Of Studi E Ricerche Enrico Fermi | Berneschi S.,CNR Institute of Neuroscience | Brenci M.,CNR Institute of Neuroscience | Nunzi Conti G.,CNR Institute of Neuroscience | And 11 more authors.
Optical Engineering | Year: 2011

Slab optical waveguides were fabricated in tung-sten-tellurite glass doped with Er3 ions by means of nitrogen ion implantation at 1.5 MeV. A wide range of ion doses (from 51012 to 8.1016 ionscm 2) was used. Optical characterization, performed by dark-line spectroscopy, revealed that the waveguides were of optical barrier type: the implanted layer exhibited a decrease of the refractive index with respect to the virgin bulk glass, while the region comprised between the sample surface and the end of the ion track acted as an optical guiding structure. It was also demonstrated that a post-implantation annealing process, performed at various temperatures on the samples implanted at higher doses, contributes to the reduction of the barrier region. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).


Moraschi M.,Centro Of Studi E Ricerche Enrico Fermi | DiNuzzo M.,Centro Of Studi E Ricerche Enrico Fermi | Giove F.,Centro Of Studi E Ricerche Enrico Fermi | Giove F.,University of Rome La Sapienza
Journal of Neurophysiology | Year: 2012

Several brain regions exhibit a sustained negative BOLD response (NBR) during specific tasks, as assessed with functional magnetic resonance imaging. The origin of the NBR and the relationships between the vascular/metabolic dynamics and the underlying neural activity are highly debated. Converging evidence indicates that NBR, in human and non-human primates, can be interpreted in terms of decrease in neuronal activity under its basal level, rather than a purely vascular phenomenon. However, the scarcity of direct experimental evidence suggests caution and encourages the ongoing utilization of multimodal approaches in the investigation of this effect. © 2012 the American Physiological Society.

Loading Centro Of Studi E Ricerche Enrico Fermi collaborators
Loading Centro Of Studi E Ricerche Enrico Fermi collaborators