Felice Sarcinelli

Fluorescence efficiency of four infrared polymethine dyes

We report on the fluorescence efficiency of four infrared (IR) polymethine dyes. These figures have been determined using an indirect method based on a fluorescence standard (Rhodamine B in ethanol). The fluorescence decay times have been measured too and their correlation with the quantum efficiency data has been shown. The optical behavior of the IR dyes in three solvents with different polarities has been compared and discussed.

Optical characterization of alkyl-thiophenic monomers functionalized with second-order nonlinear chromophores

A series of thiophenic monomers functionalized with different chromophoric groups have been optically characterized in view of preparation of polymeric films for second-order nonlinear optics and electrooptics. In order to investigate the optical behaviour inside a solid host matrix, the molecules have been physically dispersed in poly(methylmethacrylate) (PMMA) films and poled through high-temperature corona-poling for characterization through in situ second harmonic generation and ex situ angle-resolved spectroscopy. The values of dipole moment μ and optical hyperpolarizability β have been estimated inside the host matrix and related to the molecular structure. For one of the chromophores the long-term reorientation dynamics has been monitored in order to investigate the stability and the interaction with the polymeric environment.

Hybrid organic–inorganic materials containing poled zwitterionic push–pull chromophores

Dihydroxy 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 � 50� 70 pm V � 1 at the wavelength of 1.064 mm.

Entrapping of Push-Pull Zwitterionic Chromophores in Hybrid Matrices for Photonic Applications

A 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, Φ, 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.

Effects of composition and catalyst on the optical properties of ZrO2-based Ormosil films

Abstract FTIR spectroscopy measurements were performed to investigate zirconia-based Ormosil thin films. Samples synthesized with a sol–gel technique were prepared starting from 3-glycidoxypropil-trimethoxysilane (GLYMO) and zirconium(IV)-propoxide (Zr–OPr). Acetic or nitric acid were used as a catalyst. The effects induced by the Zr content and the catalyst type on the mid-infrared spectra of the sol–gel hybrid films were studied and a detailed assignment of the vibrational absorption bands is presented. The thermal evolution of the hybrid systems was also followed by monitoring the release of the organic groups, the thickness, and refractive index changes by means of FTIR, diffuse reflectance spectroscopy, and ellipsometry.