17 research outputs found
Synthesis and Nonlinear Optical Properties of Methacrylate Polymers Based on 2-[4-(N-Methyl,N-hydroxyethylamino)phenylazo]-phenyl-6- nitrobenzoxazole Chromophore
No full textMethacrylate polymers containing different molar contents of nonlinear
optical (NLO) active molecular segments based on 2-[4-(N-methyl,N-hydroxyethyl-amino)phenylazo]-phenyl-6-nitrobenzoxazole chromophores were synthesized, and their phase behavior and second-order NLO properties were investigated. Polymers containing 6 –17 mol % chromophore segments allowed the preparation of amorphous
and optically clear thin films. Some mesomorphic structuration was exhibited by a polymer with 33 mol % chromophoric units. However, this feature did not prevent the possibility of investigating the NLO properties. Nonlinear resonance-enhanced d33 coefficients were determined by second harmonic generation experiments on spin-coated, corona-poled thin films at lambda= 1064 nm. Values ranging from 40 to 60 pm/V were
measured with increasing chromophore molar contents
Hybrid organic–inorganic materials containing poled zwitterionic push–pull chromophores
No full textDihydroxy functionalised zwitterionic push-pull chromophores have been introduced in 3-glycidoxypropyltrimethoxysilane, tetraethylorthosilicate and N-[(3-trimethoxysilyl)propyl]ethylenediamine derived hybrid materials. Hybrid films have been deposited as thick layers via spin-coating. The amine groups introduced with the organically modified alkoxide bearing amine functionalities have been found to have an effective scavenger effect of the dye photobleaching.The addition, during the synthesis of the precursor sol, of N-hydroxyl carbazole has allowed to reach up to 20% of chromophore concentration avoiding the formation of aggregates within the matrix. The NLO properties of the material, after poling, have shown a good temporal stability, with retention of ca. 70% of the initial signal value, after several months, providing a d(33) value of similar to50divided by70 pm V-1 at the wavelength of 1.064 mum
Rileggendo i volumi di Paolo Baffi Studi sulla moneta e Nuovi studi sulla moneta: Riflessioni su un protagonista del '900 (Reading Paolo Baffi's "Studi sulla moneta" and "Nuovi studi sulla moneta": reflections on a leader of the last century)
No full textThe article is a revised version of a speech the author gave at a conference in memory of Paolo Baffi, former Governor of Italy's Central Bank. The author recalls his personal experience at the Banca d'Italia and his intellectual exchanges with the Governor and other leading officers, within the day-to-day activities of the Central Bank.Paolo Baffi, monetary policy, Central Banking
Incorporation of zwitterionic push-pull chromophores into hybrid organic-inorganic matrixes
No full textDihydroxy-functionalized zwitterionic push-pull chromophores have been synthesized and
incorporated into 3-glycidoxypropyltrimethoxysilane- and N-[(3-trimethoxysilyl)propyl]-
ethylenediamine-derived hybrid materials. The functionalization allowed the dye to form
covalent bonds to the matrix network, reaching up to 5% molar concentration without
aggregation. The host hybrid material was also specifically designed to reduce photobleaching
of the dye and to avoid the protonation of the carbanionic species that occurs in acidic media.
The host material exhibits very good film-forming properties, and thick highly transparent
doped layers can be fabricated via dip-coating. Upon incorporation into the matrix, the dye
exhibits a reduction of photobleaching due to the scavenger effect of the amine groups. The
strong negative solvatochromism exhibited by this class of chromophores was used to probe
the physical-chemical environment within the pores. Dye-functionalized hybrid sol-gel
materials were submitted to poling experiments, and the second harmonic signal was
measured. Good temporal stability of the NLO materials (retention of ca. 85% of the initial
signal value) was recorded after 3 months, providing a d33 value equal to 0.66 pm/V. This
system represents one of the few examples of the successful incorporation of zwitterionic
push-pull chromophores in sol-gel materials
Poled sol-gel materials doped with heterocycle-based push-pull chromophores with second-order optical non-linearity
No full textIn this work, a previously studied system of a hybrid sol-gel material doped with a push pull chromophore is optimized by co-doping the matrix with carbazole functionalized units, and achieving enhanced second order NLO properties. The microstructure modifications of the hybrid sol-gel matrix have been investigated during the thermal treatment and the poling procedure, together with the stability of the dopants. The thermal treatment performed during the poling process determines the carbazole units degradation while the chromophore molecules remain unaltered and their absorbance features are strongly modified
Entrapping of push-pull zwitterionic chromophores in hybrid matrices for photonic applications
No full textA new class of heterocycle-based push-pull chromophores showing enhanced nonlinear properties characterized by an aromatic and highly zwitterionic ground state and a quinoid/neutral excited state have been synthesized to be incorporated in sol-gel hybrid systems. This class of compounds shows very large first molecular hyperpolarizabilities (βμ as high as 27000 × 10-48 esu) and is a promising candidate for photonic applications where large second order non-linearities are required. In spite of their very large hyperpolarizability and chemical and thermal stability, these chromophores are decomposed in presence of light and oxygen (photobleaching) and are sensitive to acidic environments due to the carbanionic nature of the donor moiety. A hybrid matrix, based on N-[(3-trimethoxysilyl)propyl]ethylenediamine and 3-glycidoxypropyltrimethoxysilane, has been specifically designed to allow the incorporation of such zwitterionic compounds assuring at the same time a good temporal stability of the optical properties. Amine functionalisation has been found very effective in reducing the photobleaching by acting on these chromophores via the singlet oxygen. Second harmonic generation has been observed on poled films, and an order parameter, ф, of 0.17 has been estimated. The nonlinear coefficient deff of the samples has been thus estimated at a value two times larger than for d11 of quartz that, from literature data, is about 0.335 pm/V
Poled sol-gel materials with heterocycle push-pull chromophores that confer enhanced second-order optical nonlinearity
No full textHybrid organic-inorganic materials doped with zwitterionic push-pull chromophores with high hyperpolarizability have been synthesized by a sol-gel procedure. A large chromophore concentration was reached by using N-(hydroxyethyl)carbazole as a physical spacer (preventing the dye aggregation). Spin-coated doped films were electrically poled and second harmonic generation measurements performed in situ. During the thermally assisted poling under a N2 atmosphere, only the carbazole molecules degraded. Second-harmonic generation measurements gave an estimation of the nonlinear coefficient, r33, of 38 pm V-1 at 1064 nm
Preparation and characterization of thiophene copolymers with second order non-linear optical properties
No full textAzobenzene-substituted polythiophenes were prepared by copolymerization of 3-alkylthiophenes functionalized with an azo-chromophore and 3-alkylthiophenes as plastifying comonomers to improve solubility. Monomers with different oligomethylenic spacer and alkylic chain lengths were synthesized and copolymerized via FeCl3 oxidative polymerization. Polymer soluble fractions were characterized by H-1 and C-13 NMR, FTIR, UV-Vis spectroscopy, and GPC, DSC and TGA. Second-order non-linear optical properties were measured by the second harmonic generation technique
ENACT. Enhancing the capacity of civil society organisations to support victims of anti-LGBTQI hate crimes. National Report: Italy
No full textNational report containing the results of the research carried out in the context of the ENACT project, by Rete Lenford Avvocatura per i diritti LGTBI, ItalyThe project "ENACT - Enhancing the capacity of civil society organizations to support victims of anti-LGBTQI hate crimes" (reference code 101141894) is co-funded by the European Commission under the call CERV-2023-CHAR-LITI of the Citizens program, Equality, Rights and Values Program. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them
