1,721,170 research outputs found
Information and Communication Technology: Verso il futuro delle telecomunicazioni.
No full textEducazione, innovazione, conoscenza, creatività, ricerca scientifica e didattica. Ecco alcuni dei pilastri culturali che sostengono il progetto degli Stage a Tor Vergata, destinato a studentesse e studenti del IV e V anno della scuola secondaria di secondo grado.
Trenta studenti, meritevoli ma soprattutto motivati, vengono inseriti per cinque giorni e in due distinte fasi formative, in tre gruppi di ricerca, del Dipartimento di Fisica dell'Università di Roma Tor Vergata, attivi in settori d'avanguardia della scienza dei materiali e dei materiali innovativi per l'astrofisica sperimentale.
Per cinque giorni "vivono" nei laboratori di ricerca, esplorano e apprendono le più recenti novità e tecnologie nella ricerca di materiali innovativi per lo sviluppo dell'ICT (Information and Communication Technology), della conversione fotovoltaica e dell'astrofisica dello spazio.
Lavorano in piccoli gruppi, guidati da docenti universitari, identificano gli obiettivi a cui giungere, si distribuiscono incarichi e responsabilità, si confrontano, organizzano, gestiscono e presentano le fasi della ricerca tenendo in considerazione la teoria di riferimento
Positive curvature in Stern-Volmer plot described by a generalized model for static quenching
No full textThe fluorescence quenching effect of unfolded-fullerene nanoparticles (UFNPs) in the presence of Cu2+ ions in water solution has been investigated for a broad range of fluorophore/quencher concentrations. The experimental Stern-Volmer plot exhibited a nonlinear behaviour with an initial upward curvature even though carbon nanoparticles are known to form stable complexes with metal ions and thus a dominant static quenching with a linear plot is expected according to the classical Stern-Volmer equation. A generalized model for static quenching, applicable to any value of fluorophore/quencher concentrations, provided a very good fit with the experimental data without the need to introduce any second-order effect, such as in the sphere of action model or diffusion-limited processes. Moreover, by changing the dilution of the UFNP solution, we could study how the quenching ratio depended on the fluorophore concentration, whereas it is predicted to be constant by the standard model. In addition to providing a significant test of the nonlinear model for static quenching, we believe this study could help find the best parameters for the optimization of sensitivity and signal-to-noise ratio in applications such as fluorescence sensing
Femtosecond laser selective intramolecular double-proton transfer in [2,2′-bipyridyl]-3,3′-diol
No full textWe report an excitation energy dependence of the dynamics of the excited-state intramolecular double-proton transfer of [2,2′-bipyridyl]-3,3′-diol in liquid solution. By means of femtosecond fluorescence upconversion experiments it is shown that an increase of the vibrational energy in the excited electronic S1 state results in an increase of the ratio of the reaction yields of the monoketo and diketo tautomeric products. The dominance of the concerted double-proton transfer process at the lower excitation energies is evidence for an energy barrier in the dienol-monoketo reaction pathway
Detection of heavy metals in water using graphene oxide quantum dots: an experimental and theoretical study
Full text linkIn this work, we investigate by ab initio calculations and optical experiments the sensitivity
of graphene quantum dots in their use as devices to measure the presence, and concentration, of
heavy metals in water. We demonstrate that the quenching or enhancement in the optical response
(absorption, emission) depends on the metallic ion considered. In particular, two cases of opposite
behaviour are considered in detail: Cd2+, where we observe an increase in the emission optical
response for increasing concentration, and Pb2+ whose emission spectra, vice versa, are quenched
along the concentration rise. The experimental trends reported comply nicely with the different
hydration patterns suggested by the models that are also capable of reproducing the minor quenching/
enhancing effects observed in other ions. We envisage that quantum dots of graphene may be
routinely used as cheap detectors to measure the degree of poisoning ions in water
Photonics and Plasmonics: New Challenges for Optical Nanostructured Materials in Sensing
Full text linkIn the last decade, new technologies have undertaken an extraordinary development, based not only on new materials and new processes but also on design, modelling, information technology, and artificial intelligence [...
Picosecond spectroscopy of color center in KBr:OH-
No full textThe rapid decay of the excited state of the F centers in KBr:OH- has been measured by mean of a pump and probe technique with picosecond time resolution. The lifetime of the F centers (τ ~ 1 μs at 77 K) is shortened in the OH- doped samples, to τ ∼ 310 ps. The quenching of the normal radiative lifetime seems to be related to librational excitation of the OH- molecular ion. © 1993
Doubly patternable epoxy based sol-gel structures by UV and soft lithography
No full textThe sol-gel synthesis of hybrid materials offers special opportunities to combine polymer and glass properties and to create promising candidates for photonic applications.
We report on the optical and morphological characterization of a new photosensitive epoxy based solegel system. Germanium ethoxide and 3-Glycidoxypropyltrimethoxysilane were used as precursors for hybrid sol-gel planar coatings. A photoacid generator was added to solution in order to allow the epoxy photopolymerization when the films are selectively exposed to UV light. The refractive index increase (Dn 1⁄4 0.015) induced by UV light allows the direct patterning of waveguiding structures having good morphological quality. Stripes and beam splitters were defined by direct UV exposition on silicon substrates. Moreover, we present structures made by thermal imprinting method. Silicon masters have been used to transfer relief gratings on the photopolymerizable epoxy sol-gel materials. Combining thermal imprinting technique and UV light exposition through a photomask, complex structures can be realized such as light couplers, sensors and wavelength filters
Refractive index measurements of thin films using both Brewster and m-line technique: A combined experimental setup
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