Antonio Cardone

High third-order nonlinear optical susceptibility in new fluorinated poly(p-phenylenevinylene) copolymers measured with the Z-scan technique

The third-order nonlinear optical properties of a series of copoly(2, 3, 5, 6-tetrafluoro-1, 4-phenylenevinylene-2, 5-dioctyloxy-1, 4-phenylenevinylene) that contain variable ratios of two differently substituted monomers have been studied in chloroform solutions at l=1064 nm by the picosecond Z-scan technique. Nonlinear refractive index n(2) of the samples investigated has been found to be negative, and a strong dependence of its magnitude on the copolymers composition has been observed. The highest third-order nonlinear optical susceptibility, |x((3))|=(6 +/- 2)x 10(-10) esu, was measured for a copolymer obtained by reaction of equimolar quantitites of the parent monomers.

Melanin Layer on Silicon: an Attractive Structure for a Possible Exploitation in Bio-Polymer Based Metal- Insulator-Silicon Devices

Dr. M. Ambrico , Dr. P. F. Ambrico CNR-Istituto di Metodologie Inorganiche e dei Plasmi-UOS di Bari70125 Bari, Italy E-mail: marianna.ambrico@ba.imip.cnr.it Dr. A. Cardone , Dr. S. R. Cicco CNR-Istituto di Chimica dei Composti OrganoMetallici-UOS di Bari70125 Bari, Italy Ligonzo , Dr. . T Prof. Augelli . V Dipartimento Interateneo di FisicaUniversita degli Studi di Bari “Aldo Moro”70125 Bari, Italy Dr. R. Di Mundo , Prof. G. M. arinola F Dipartimento di ChimicaUniversita degli Studi di Bari “Aldo Moro”70125 Bari, Italy

Engineering polydopamine films with tailored behaviour for next-generation eumelanin-related hybrid devices

Eumelanin-type biopolymers have attracted growing interest in the quest for soft bioinspired functional materials for application in organoelectronics. Recently, a metal-insulator-semiconductor device with a good quality interface was produced by spin coating of a commercial synthetic eumelanin-like material on a dry plasma-modified silicon surface. As a proof-of-concept step toward the design and implementation of next-generation eumelanin-inspired devices, we report herein an expedient chemical strategy to bestow n-type performance to polydopamine, a highly popular eumelanin-related biopolymer with intrinsic semiconductor behaviour, and to tune its electrical properties. The strategy relies on aerial co-oxidation of dopamine with suitable aromatic amines, e.g. 3-aminotyrosine or p-phenylenediamine, leading to good quality black polymeric films. Capacitance–voltage experiments on poly(dopamine/3-aminotyrosine) and poly(dopamine/p-phenylenediamine)-based metal insulator semiconductor devices on p-Si indicated a significant increase in flat band voltage with respect to polydopamine and previous synthetic eumelanin-based diodes. Variations of the flat band voltage under vacuum were observed for each device. These results point to polydopamine as a versatile eumelanin-type water-dependent semiconductor platform amenable to fine tuning of its electronic properties through incorporation of π-conjugating aromatic amines to tailor functionality.

Design and synthesis of fluorenone-based dyes: two-photon excited fluorescent probes for imaging of lysosomes and mitochondria in living cells

Three fluorenone-derived two-photon fluorescent probes (TK) targeting the lysosomes (TK-Lyso) and mitochondria (TK-Mito1 and TK-Mito2) were synthesized by introducing different diphenylamine moieties into the fluorenone core. The TK dyes showed high biocompatibility and long-term retention, low cytotoxicity, large Stokes shift and good fluorescence quantum yield. The results of the present work disclose a class of organic dyes with potential wide applications as specific and efficient probes for lysosomes and mitochondria in the study of various biological processes.

Fluorinated Poly(p-phenylenevinylene)s: Synthesis and Optical Properties of an Intriguing Class of Luminescent Polymers

This review is an overview of our previous work on the synthesis and properties of poly(p-phenylenevinylene)s (PPVs) selectively fluorinated in different positions of the conjugated backbone. Both the synthetic challenges and the effects of functionalization with fluorine atoms on the optical behavior are discussed, highlighting the peculiarities and the interest of this class of conjugated polymers. A general polymerization protocol for PPVs, that is based on the Pd-catalyzed Stille cross-coupling reaction of bis-stannylated vinylene monomers with aromatic bis-halides, has been successfully extended to the synthesis of selectively fluorinated poly(p-phenylenevinylene)s. The properties of a series of these PPVs differing in the number and positions of the fluorine atoms on the conjugated backbone have been studied, even in comparison with the non-fluorinated counterparts. The intriguing optical features of the resulting materials are discussed considering not only the role of the electronic and steric effects induced by the fluorine substituents, but also the impact of the fluorination on the solid state organization and intermolecular interactions.

Synthetic Aspects and Electro-Optical Properties of Fluorinated Arylenevinylenes for Luminescence and Photovoltaics

In this review, the main synthetic aspects and properties of fluorinated arylenevinylene compounds, both oligomers and polymers, are summarized and analyzed. Starting from vinyl organotin derivatives and aryl halides, the Stille cross-coupling reaction has been successfully applied as a versatile synthetic protocol to prepare a wide series of π-conjugated compounds, selectively fluorinated on the aromatic and/or vinylene units. The impact of fluoro-functionalization on properties, the solid state organization and intermolecular interactions of the synthesized compounds are discussed, also in comparison with the non-fluorinated counterparts. Luminescent and photovoltaic applications are also discussed, highlighting the role of fluorine on the performance of devices.

An aryleneethynylene fluorophore for cell membrane staining.

The use of an amphiphilic aryleneethynylene fluorophore as a plasma membrane marker in fixed and living mammalian cells and liposome model systems is demonstrated. We show here that the optical properties of the novel dye are almost independent on pH, in the range 5.0-8.0. Spectroscopic characterization performed on unilamellar liposomes ascertained that the fluorescence intensity of the aryleneethynylene fluorophore greatly increases after incorporation in lipidic membranes. Experiments performed on different mammalian cells demonstrated that the novel membrane marker exhibits fast staining and a good photostability that make it a suitable tool for live cell imaging. Importantly, the aryleneethynylene fluorophore was also shown to be a fast and reliable blue membrane marker in classical multicolor immunofluorescence experiments. This study adds new important findings to the recent exploitation of the wide class of aryleneethynylene molecules as luminescent markers for biological investigations.

Synthesis of substituted conjugated polymers: Tuning properties by functionalization

The review addresses features of special interest concerning two classes of functionalized semiconducting polymers: poly(aryleneethynylene)s (PAEs) bearing biomolecules as chiral nonracemic pendant groups and poly(phenylenevinylene)s (PPVs), which are fluorinated in various positions of the repeating units. Molecular design and choice of specific substituents, synthetic protocols, and the effect of functionalization on properties of the polymers both in solution and in the solid state are discussed.

Fluoro-functionalization of vinylene units in a polyarylenevinylene for polymer solar cells

A low band-gap copolymer PDTBTFV alternating bis-thienyl-(bis-alkoxy)-benzothiadiazole blocks with difluorovinylene units and its non-fluorinated counterpart PDTBTV have been synthesized and characterized as donor materials in bulk heterojunction (BHJ) solar cells with PCBM as the acceptor. The solar cells with the fluorinated polymer show better photovoltaic performances than those recorded with the non-fluorinated material. Comparative spectroscopic and computational studies, together with morphological, electrical and optical characterization of thin films, have been carried out to shed light on the reasons for the improvement of performances as induced by the double bond fluorination. Our study introduces the fluorinated double bond as a new conjugated unit in donor polymers for BHJ solar cells.

[1]Benzothieno[3,2-b]benzothiophene-Based Organic Dyes for Dye-Sensitized Solar Cells.

Three new metal-free organic dyes with the [1]benzothieno[3,2-b]benzothiophene (BTBT) π-bridge, having the structure donor-π-acceptor (D-π-A) and labeled as 19, 20 and 21, have been designed and synthesized for application in dye-sensitized solar cells (DSSC). Once the design of the π-acceptor block was fixed, containing the BTBT as the π-bridge and the cyanoacrylic group as the electron acceptor and anchoring unit, we selected three donor units with different electron-donor capacity, in order to assemble new chromophores with high molar extinction coefficients (ε), whose absorption features well reflect the good performance of the final DSSC devices. Starting with the 19 dye, which shows a molar extinction coefficient ε of over 14,000 M(-1) cm(-1) and takes into account the absorption maximun at the longer wavelength, the substitution of the BFT donor unit with the BFA yields a great enhancement of absorptivity (molar extinction coefficient ε > 42,000 M(-1) cm(-1)), until reaching the higher value (ε > 69,000 M(-1) cm(-1)) with the BFPhz donor unit. The good general photovoltaic performances obtained with the three dyes highlight the suitable properties of electron-transport of the BTBT as the π-bridge in organic chromophore for DSSC, making this very cheap and easy to synthesize molecule particularly attractive for efficient and low-cost photovoltaic devices.