310 research outputs found
Studi in memoria di Antonio Romano Tassone. Vol. 1
No full textAnalisi del criterio "funzionale" di qualificazione delle fondazioni di diritto pubblico da parte di Antonio Romano Tasson
Dynamic Microscopy Study of Ultrafast Charge Transfer in a Hybrid P3HT/Hyperbranched CdSe Nanoparticle Blend for Photovoltaics
No full textWe present a spectroscopic investigation on a new hyperbranched cadmium selenide nanocrystals (CdSe NC)/poly(3-hexylthiophene) (P3HT) blend, a potentially good active component in hybrid photovoltaics. Combined ultrafast transient absorption spectroscopy and morphological investigations by means of an ultrafast confocal microscope reveal a strong influence of the complex local structure on the photogenerated carrier dynamics. In particular, we map the electron-transfer process across the hybrid NC/polymer interface, and we reveal that charge separation occurs through a preferential pathway from the CdSe nanobranches to the P3HT chains. Efficient charge generation at the distributed heterojunction is also confirmed by scanning kelvin probe force microscopy measurements
Reduction of the thermal expansion of unsaturated polyesters by chain-end modification
No full textThe use of di-isocyanates, such as diphenylmethane-4,4'-di-isocyanate (MDI), isophorone di-isocyanate (IPDI) and 1,6-hexamethylene-di-isocyanate (HDI), with different molecular rigidity as modifiers of the thermal expansion behaviour of cured unsaturated polyester. resins was investigated.
The addition of the di-isocyanate in a stoichiometric amount comparable to the predicted number of free OH groups of the resin does not affect the curing process and the resin workability; the reaction monitored by FT-IR shows a complete chemical conversion of the OH groups at the end of the curing process. The resin modified with MDI is characterized by a reduced thermal expansion coefficient and by an increase of the glass transition temperature. Very modest effect was observed with IPDI while no changes could be detected with HDI. Experiments with variable amounts of MDI indicate that the decrease of the expansion coefficient is paralleled by the increase of the glass transition temperature. The observed effect is discussed and related to the formation of rigid bridges among the dangling chains of the polymer deriving from the reaction of the MDI with the OH groups. (c) 2005 Elsevier Ltd. All rights reserved
Band-edge ultrafast pump–probe spectroscopy of core/shell CdSe/CdS rods: assessing electron delocalization by effective mass calculations
No full textUnraveling electron and hole relaxation dynamics in colloidal CdTe nanorods: A two-dimensional electronic spectroscopy study
No full textIn this work we study the ultrafast exciton dynamics in CdTe nanorods by using two-dimensional electronic spectroscopy (2DES). By simultaneously exciting the lowest three excitonic transitions (i.e. S1, S2 and S3) we extract the electron and hole relaxation pathways, owing to the combined temporal and spectral resolution of 2DES. In particular, we directly observe hot hole relaxation from the second to the first exciton state in about 30 fs by excitation of the S2 transition. Additionally, we extract a direct charge relaxation to S1 by disentangling the overlapping bleach and excited state induced energy level shifts after excitation of S3
La ragione del dubbio
No full textLibro pubblicato per la Retrospettiva di Francesco Rosi del Premio internazionale Maestri del Cinema di Fiesole 200
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