Ivana Moggio

New application of fluorescent organotin compounds derived from Schiff bases: synthesis, X-ray structures, photophysical properties, cytotoxicity and fluorescent bioimaging

A series of eight new organotin compounds derived from Schiff bases has been prepared by a multicomponent reaction from 2-hydroxy-1-naphthaldehyde or 4-substituted-2-hydroxybenzalhedyde, benzhydrazine, and the corresponding diorganotin oxide (R2SnO, R = nBu or Ph). All of the compounds were fully characterized by NMR (1H, 13C, and 119Sn), IR, UV/vis, elemental analyses and fluorescence spectroscopy. The crystal structures for some organotin compounds were determined by single crystal X-ray diffraction analysis. All of the compounds display fluorescence at room temperature with quantum yields of about 2 × 10-4 to 0.56. The cytotoxic activity and cellular imaging studies were carried out with the newly synthesized compounds. To the best of our knowledge, this is the first report of organotin compounds with Schiff base ligands investigated for fluorescence bioimaging (FBI).

Layer-by-layer assembled films of a rigid poly(phenyl-ethynylene) and alternate poly(phenyl-ethynylene)/poly(aniline)

Abstract A new main chain segmented rigid rod-like polymer, poly[2,5-dodecyloxy-1,4-bis(ethylene glycol benzoate)ethynylene], hereafter called pPEG2 has been synthesized by a palladium catalyzed polycondensation. The interactions within the pPEG2 molecules are strong enough to give self-assembled multilayers (SAM), (pPEG2/pPEG2) m from diluted solutions. The films show emission in the green region at 512xa0nm. pPEG2 alternated with enzymatically synthesized poly(aniline) (PANi) as polycation provides supramolecular layered assemblies (pPEG2/PANi) n , which will be of great interest for the future realization of light emitting diodes (LEDs) or biological detectors. The thickness of the films can be controlled by the number of absorbed layers as stated by UV-Vis spectroscopy. The morphology of (pPEG2/pPEG2) m assemblies, analyzed by AFM, consists of columnar domains coexisting with fine and homogenously distributed needles, while for the alternated (pPEG2/PANi) n assemblies, the SAM are rather of granular type.

Interaction of substituted poly(phenyleneethynylene)s with ligand-stabilized CdS nanoparticles

The interfacial region between surface-modified semiconducting nanoparticles and polymers remains difficult to characterize experimentally in atomic resolution and contributes to the limited efficiency of hybrid photovoltaic cells and luminescent devices. Therefore, molecular dynamics simulation was employed to investigate the structure of cadmium sulfide nanoparticles capped with 3-mercaptopropyltrimethoxysilane (MPS) in contact with four substituted poly(phenyleneethynylene)s using a new force field for CdS and the polymer consistent force field. The results show that polymers with long alkyl side chains tend to wrap around the nanoparticles, and reduce backbone bending as well as polymer diffusion. The absence of alkyl side chains decreases the distance of conjugated backbones from the surface. Differences in the preferred location of functional groups of the polymers on the nanoparticle surface and of covalent versus non-covalent bonding were also monitored. Polymers containing terminal hydroxyl groups on alkyl side chains approach the surfactant corona and the core of the CdS-MPS nanoparticles. Close contact supports the formation of silyl ether cross-links although the interfacial structure upon bond formation remains similar to that of the non-covalently attached polymers. Ester groups bound to aromatic rings in the poly(phenyleneethynylene) backbone did not closely approach the nanoparticle surface. The results are the first step to understand nanoparticle–polymer interfaces at length scales of 10 nm and explore correlations with photovoltaic performance.

Amphiphilic phenylene-ethynylene polymers and oligomers for polarized electroluminescence

Abstract We investigate the electroluminescence of polymer and oligomer derivatives of p (phenyl-ethynylene) bearing amphiphilic side chains. The polymer and the heptamer show liquid crystalline properties, which are characterized by X-ray diffraction. A periodic structure is observed, which corresponds to a lamellar system with a layer spacing of about 3.8xa0nm. Two other diffuse bands correspond to a liquid-like order of the side chains and a weak interaction of the π–π interactions between phenyl rings. We have investigated the absorption and the photoluminescence (PL) properties of the polymer and the heptamer films prepared by the Langmuir–Blodgett (LB) and by spin-coating techniques. The polymer film shows an absorption peak at 408xa0nm with a shoulder at 436xa0nm; while the heptamer shows a small blue shift of the main peak at 382xa0nm and the shoulder at 415xa0nm. Based on the liquid crystalline properties, the two materials can be oriented by rubbing, giving rise to a good dichroic absorption spectrum. The ordering parameter at the peak absorption is better for the polymer than for the heptamer, OP=0.58 and 0.45, respectively. The PL of the two materials are observed at 539 and 516xa0nm, respectively. The PL yields, measured by the integration sphere method, gives a result of 0.23 and 0.20 emitted photon per absorbed photon respectively. A good dichroic photoemisson is also observed on the oriented rubbed films prepared by spin-coating. We demonstrate that the oligomer can be used in a blue-green light emission device by using the LB multilayer or by spin-coating techniques. We investigate the polarized electroluminescence in devices with the configuration ITO/film/LiF–Al. The oligomer (or the polymer) films are oriented by rubbing. A polarized emission parallel or perpendicular to the sliding direction is observed. The measured dichroism reaches a value of 8 at 531xa0nm for the heptamer.

Theoretical calculations of the geometries and of the lowest optical transitions of singly and doubly charged oligodiacetylenes

Abstract We have performed theoretical calculations on the singly and doubly charged species of the lowest unsubstituted oligodiacetylenes, with the scope of achieving information on the charged photoexcitations of polydiacetylenes. On the basis of the AM1-optimized geometries of the radical ions and of the dications we have computed their low-energy vertical transitions, using the INDO-SCI method in order to take into account the electron correlation. Extrapolated polymer results are compared with the photoinduced absorption spectra.

Optical and electronic properties of thin PDAs films with very narrow excitonic bandwidth

Soluble polycarbazolyldiacetylene systems (PCDAs) having long alkyl chains on the carbazolyl substituents have been recently prepared. In these systems, PCDAs chains in the solid state are assembled in hexagonal columnar structures. Thin films of these PCDAs show a very high value for the third order susceptibility. In order to study the effect of the substituents in the electronic properties of PCDAs we have inserted -CO(CH 2 ) n CH 3 groups on the carbazolyl rings, thus decreasing the electron-donor effect of carbazole. Non-birefringent thin films of excellent optical quality are obtained whose optical and electronic properties are here reported.

Development of stained polymeric nanocapsules loaded with model drugs: Use of a fluorescent poly(phenyleneethynylene)

A phenyleneethynylene polymer (here denoted pPy3E-sqS) was synthesized and characterized by UV-vis spectroscopy, fluorescence spectroscopy, and TEM, and was used for the staining of polymeric nanocapsules. The nanocapsules presented good temporal stability, without changes in shape or fluorescence, and were suitable for use in drug release systems. The mean particle size was around 430nm, the polydispersity index was below 0.2, and the zeta potential was around -13mV. The release kinetics is one of the most important factors to consider in drug delivery systems, and here it was observed that nanocapsules containing the fluorescent polymer still maintained the ability to modulate the release of the fungicides tebuconazole and carbendazim (used as model drugs) after 4days. Preliminary results indicated that staining with the fluorescent pPy3E-sqS polymer could be used as a valuable tool to track the behavior of polymeric systems in the environment. However, further studies will be needed to clarify the environmental behavior and possible toxicity.

Optical and morphological properties of self assembled thin films of poly[1,6-di(N-carbazolyl)2,4-hexadiyne]

We report the optical and morphological properties of thin films of poly[1,6-di(N-carbazolyl)2,4-hexadiyne] (polyDCHD) obtained for the first time by self assembly of the monomer followed by UV polymerization. Due to the insolubility of the polymer, successive transfers are possible thus allowing the preparation of multilayers. The UV-Vis characterization and AFM studies indicate a good optical quality for these samples, which could represent alternative materials, easier to prepare with respect to single crystals or epitaxial films, for non-linear optical or photonic applications of polyDCHD.

Orientation of thin films of conjugated systems by different techniques

Abstract Oriented thin films of good optical quality are necessary for applications of conjugated systems in non linear optical devices. In this paper, we focus on the preparation and spectroscopic characterization of thin films of two different polymers, a polydiacetylene, poly[9-(N-carbazolyl)-2,4-hexadyine-1-ol-1, ethylurethane] (pCNEU) and a polyphenylene–ethynylene, the (11-undecanol) benzoate containing polymer (pPEn). pCNEU gives the best orientation by epitaxial growth on polytetrafluoroethylene (PTFE) layers aligned on glass. On the contrary pPEn is best oriented on glass substrates by rubbing technique.