Penton Eduardo

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Papers by Penton Eduardo

Immobilization of the enzyme β-lactamase by self-assembly on thin films of a poly(phenyleneethynylene) sequenced with flexible segments containing sulfur atoms

Materials Science and Engineering: C, 2007

A novel poly(phenyleneethynylene) sequenced in the main conjugated chain with flexible groups con... more A novel poly(phenyleneethynylene) sequenced in the main conjugated chain with flexible groups containing sulfur atoms has been synthesized by Heck-Sonogashira coupling reaction. Layer-by-layer films of the polymer have been prepared with a linear growth in thickness up to four layers as evidenced by UV-Vis spectroscopy and perfilometry. On the top of these multilayers, the enzyme β-lactamase was deposited by self-assembly. The enzymatic activity was measured by a modified spectrophotometric standard assay method for penicillin G, ampicillin and amoxicillin. A higher and faster activity was obtained for penicillin G and thus preliminary study of the biosensor response by fluorescence was carried out for this antibiotic revealing a decrease in the polymer fluorescence as function of the penicillin G concentration.

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Cálculo de las excitaciones electrónicas en polímeros conjugados con carbonilo A-B sustituido

Se reporta el modelado molecular de dos familias de oligómeros conjugados (polímeros de condensac... more Se reporta el modelado molecular de dos familias de oligómeros conjugados (polímeros de condensación aldólica con y sin sustituyentes etoxi) de entre dos y seis unidades repetitivas. Las geometrías se optimizaron mediante la "Aproximación Local de la Densidad de Spin" y el cálculo de los estados electrónicos excitados mediante los métodos "Negación Intermedia de la diferencia de Traslape de Zerner" y "Teoría Funcional de la Densidad dependiente del tiempo". Los resultados muestran el efecto de los sustituyentes y del grado de polimerización en los espectros U.V. Vis. así como una deslocalización no total en los oligómeros de condensación aldólica. Se corrobora el efecto electrón donador del grupo etoxi y el efecto aceptor del oxígeno carbonílico.

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Supramolecular Order of 2,5-Bis(dodecanoxy)phenyleneethynylene–Butadiyne Oligomers in the Solid State

by Penton Eduardo and Carlos Gallardo-Vega

Langmuir, 2015

The supramolecular order of a 2,5-bis(dodecanoxy)phenyleneethynylene-butadiyne series of rod-like... more The supramolecular order of a 2,5-bis(dodecanoxy)phenyleneethynylene-butadiyne series of rod-like oligomers with 2, 4, 6, and 8 phenyleneethynylene moieties was studied in the solid state by differential scanning calorimetry (DSC), temperature-dependent small- and wide-angle X-ray scattering (SWAXS), selected area electron diffraction (SAED), polarized optical microscopy (POM), high-resolution transmission microscopy (HRTEM), and scanning tunneling microscopy (STM). It was found that all of the oligomers self-assemble in blocks of molecules that resemble bricks that are randomly oriented. These oligomers are described as sanidic liquid crystals as a term to classify their mesomorphic behavior because of their brick or board-like structure. The strong π-π interaction that governs the package of conjugated backbones was evidenced by the reiterative distances of 0.36 ± 0.017 nm found by SWAXS and 0.32 ± 0.017 nm found by HRTEM. A STM study of a cast film of the tetramer deposited on highly oriented pyrolitic graphite (HOPG) allowed for the visualization and determination of the conjugated backbone length of 2.48 nm and a phenyl-phenyl distance of 0.34 nm, suggesting that the molecules are stacked in lamellae perpendicularly aligned to the substrate.

From Langmuir-Blodgett Films to Electroluminescent Devices with an Amphiphilic Phenyl-Ethynylene Oligomer

MRS Proceedings, 1999

Novel Composites of Carbon Nanotubes with a Poly (Phenylene Ethynylene) by Non-Covalent Wrapping for Photovoltaic Devices

ABSTRACT Conjugated polymers exhibit optoelectronic properties comparable with those of inorganic... more ABSTRACT Conjugated polymers exhibit optoelectronic properties comparable with those of inorganic semiconductors and with some advantage over them. By their side, carbon nanotubes (CNTs) offer a great opportunity for exciton dissociation. For this reason, the combination of conjugated polymer and carbon nanotubes in composites has garnered interest in recent advances for solar cells technology. In this work we present an extensive study on nanocomposites based on a poly(phenylene ethynylene) sequenced with thioester moieties (pPET3OC12-sqS) with single (SWCNTs) and multiwall (MWCNTs) carbon nanotubes in order to develop novel hybrid materials for photovoltaic cells. 1HNMR analysis suggests a strong interaction type π stacking between the rigid conjugated backbone of the polymer and the backbone of the nanotubes in agreement with previous works. This interaction is also reflected in the resonant peaks of both, the tioester-ethyldisulfide and dodecanoxy side chains of pPET3OC12-sqS, and likely due to the fact that these spins need more relaxation time to show signals. The absorption and emission maximal wavelengths of the polymer are maintained when it is wrapped on the nanotubes even if the baseline of the composites UV-Vis spectra is very marked due to the scattering contribution from the nanotubes. The optical band gap decreases in the nanocomposite suggesting an enhancement of the electrical conductivity as confirmed by cyclic voltammetry and by electrical measurement in the films, where the electrical conductivity of the composites resulted one order of magnitude higher than that of pPET3OC12-sqS. A quenching of the polymer fluorescence is found, which is attributed to the efficient energy transfer between pPET3Oc12-sqS and CNTs, more than the disruption of conjugation by a conformational change as reported and in agreement with the fact that the absorption and emission maxims are unchanged. Based on these results, a molecular model was proposed. Studies of SEM and TEM microscopy indicate a good dispersion of the nanotubes in the polymer matrix as well as the absence of bundles of nanotubes in the composite which is consistent with a homogeneous adhesion of the PPS around the carbon nanostructures.

A New Polymeric Immobilizer for Enzymes Suitable for SPR Detection Scheme

Sensors and Microsystems - Proceedings of the 10th Italian Conference, 2008

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

Synthetic Metals, 2003

We report the optical and morphological properties of thin films of poly[1,6-di(N-carbazolyl)2,4-... more 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.

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

by Penton Eduardo and David Modarelli

Journal of Materials Chemistry A, 2014

ABSTRACT The interfacial region between surface-modified semiconducting nanoparticles and polymer... more ABSTRACT 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.

Resorcinarene-dendrimers with stilbene moieties for optoelectronics

Tetrahedron, 2008

Dendrimers with resorcinarene core and p-conjugated dendron branches with 16 and 32 stilbene grou... more Dendrimers with resorcinarene core and p-conjugated dendron branches with 16 and 32 stilbene groups have been synthesized and characterized by 1 H and 13 C NMR, FTIR, UV-vis, fluorescence spectroscopy, MALDI-TOF, electrospray or FAB þ mass spectrometry, and elemental analysis. Homogeneous thin films of resorcinarene-dendrimers deposited on quartz, glass or ITO substrates were prepared by spin-coating. All the materials showed absorption in the UV region in both chloroform solutions and thin films. The band gap energies (E g ) determined from both UV-vis spectroscopy and voltammetry were in the semiconducting range. A slight decrease in the E g values was observed when passing from the first generation of dendrimers to the second one, which can be attributed to an increase in the p-conjugated system. The fluorescence quantum yield of the molecules in solution was low and practically null in the solid state. Nevertheless, a very interesting behavior was observed in the reductive voltammetric cycle, where electrochromism from transparent to blue forms occurred in the film by n-doping process; property that makes these materials suitable for the development of electrochromic devices such as smart windows.

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Synthesis and photophysical and supramolecular study of π-conjugated (diethylene glycol methyl ether) benzoateethynylene oligomers and polymers

Polym. Chem., 2015

We report on the synthesis of a trimer, pentamer, heptamer and a polymer of the (benzoate)ethynyl... more We report on the synthesis of a trimer, pentamer, heptamer and a polymer of the (benzoate)ethynylene type bearing highly polar diethylene glycol methyl ethers as side chains. All of the materials were characterized by 1 H, DEPT-135, APT, 13 C NMR, UV-Vis, static and dynamic fluorescence spectroscopy. The X-ray scattering patterns of the pentamer and heptamer revealed a Smectic C lamellar order of molecules, while that of the polymer was of the Nematic type; however, any known texture reported in the literature was observed by POM. The general term to classify the mesomorphic behaviour of these materials is Sanidic liquid crystals (LCs), which is consistent with their molecular shape assembly resembling bricks or board-like structures. The distance within the lamellae of 2.1, 2.3 and 2.0 nm for the pentamer, heptamer and polymer, respectively, is almost twice the distance of a single molecule in its more extended conformation of 1.48 nm. Therefore, the model of organization is consistent with a supramolecular assembly in bilayers, as was found in other (alkyl)benzoateethynylenes, where the side chains are oriented in the opposite way, in a back-to-back "comb-like" style. The strong π-π interaction that governs these materials was evidenced by the repeated distance of 0.35 nm found by both X-ray scattering and HRTEM microscopy, which corresponds to the distance between conjugated chains. Photophysical properties are discussed as a function of the conjugation length and of the iodine or hydrogen terminal groups and are supported by theoretical calculations. † Electronic supplementary information (ESI) available: Scheme 1S, experimental procedures, theoretical calculations, 1 H, APT, 13 C NMR spectra, SAX diffraction patterns of 17 at different temperatures, photophysical properties in solution of oligomers. See

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Mechanosynthesis of a phenylenedivinylidenebisquinoline. Optical, morphological and electroluminescence properties

Journal of Molecular Structure, 2015

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Double Molecular Antenna Pyrene – Bridge - Fullerene C60

The Open Organic Chemistry Journal, 2010

Abstract: C60 pyrene anthrylvinylene triads were synthesized with good yields by an O-alkylation ... more

Optoelectronic properties of a perylene substituted (cholesteryl)benzoateethynylene co-polymer

by Penton Eduardo and Carlos Gallardo-Vega

Materials Chemistry and Physics, 2014

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Effect of elemental sulfur in the crosslinking reaction of poly(vinyl chloride) with tetramethyl thiuram disulfide

Journal of Vinyl and Additive Technology, 1995

... Thiuram Disulfide EDUARDO ARIAS-MARfN,* LUIS F. RAMOS DE VALLE, OLIVERIO RODFdGUEZ-FERNhDEZ, ... more

Optical and morphological characterisation of a silver nanoparticle/fluorescent poly(phenylenethynylene) composite for optical biosensors

Vacuum, 2010

Thiol silver nanoparticles prepared by the phase transfer method have been mixed with a fluoresce... more Thiol silver nanoparticles prepared by the phase transfer method have been mixed with a fluorescent poly(phenylenethynylene) sequenced with dithioester-diethylsulfide moieties in order to develop a nanocomposite for its possible application in optical biosensors for the detection and attack of fungi such as Paecilomyces variotii. Films have been prepared by dipping technique and characterized by AFM, XPS, UV-Visible and fluorescence spectroscopy. Optical Absorption properties of the nanocomposite are similar to those of the polymer with an absorption tail in the visible which supports the presence of silver nanoparticles. Despite the lack of fluorescence of the nanoparticles, the composite emits in the yellow green region and the intensity of the fluorescence of the nanocomposite film decreases after the immersion in the culture thus permitting the detection of the fungus by this technique. The fungus can be deposited on films of both the polymer and nanocomposite, nevertheless only in the latter case, an attack on mycelium is observed revealing the fungicidal effect of silver nanoparticles in the nanocomposite.

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Orientation of thin films of conjugated systems by different techniques

Synthetic Metals, 2001

Oriented thin ®lms of good optical quality are necessary for applications of conjugated systems i... more Oriented thin ®lms 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 ®lms of two different polymers, a polydiacetylene, poly[9-(Ncarbazolyl)-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 polytetra¯uoroethylene (PTFE) layers aligned on glass. On the contrary pPEn is best oriented on glass substrates by rubbing technique. #

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Dodecanoxy-phenylethynylene oligomers for light emitting diodes

Synthetic Metals, 2004

A family of rigid rod-like phenylethynylene oligomers and the homologue polymer were characterize... more A family of rigid rod-like phenylethynylene oligomers and the homologue polymer were characterized by X-ray diffraction, DSC, UV-Vis and fluorescence spectroscopy. The pentamer as well as the heptamer exhibit liquid crystal properties characterized by a strong birefringence as observed by polarized microscopy, by DSC and by the X-ray diffraction pattern, where a lamellar ordered phase with layer spacing of 2.6 nm was determined by Bragg's equation. The optical absorption and emission spectra in CHCl 3 showed that the conjugation increases with the oligomer length and the limit value is reached for the polymer, although a close saturation of theconjugation is almost obtained for the heptamer. In a preliminary study, diodes were fabricated by spin coating thin films of pentamer and polymer on ITO electrodes and by subsequent vacuum deposition of aluminum cathodes. The (ITO/film/Al) devices showed intrinsic electroluminescent properties with low threshold voltage around 4 V and yielding close to 10 −6 . These results are interesting in view of a further study of the optoelectronic properties of the whole family of oligomers.

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Amphiphilic phenylene-ethynylene polymers and oligomers for polarized electroluminescence

Synthetic Metals, 2002

We investigate the electroluminescence of polymer and oligomer derivatives of p(phenyl-ethynylene... more 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 3.8 nm. Two other diffuse bands correspond to a liquid-like order of the side chains and a weak interaction of the p±p interactions between phenyl rings. We have investigated the absorption and the photoluminescence (PL) properties of the polymer and the heptamer ®lms prepared by the Langmuir±Blodgett (LB) and by spin-coating techniques. The polymer ®lm shows an absorption peak at 408 nm with a shoulder at 436 nm; while the heptamer shows a small blue shift of the main peak at 382 nm and the shoulder at 415 nm. 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 516 nm, 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 ®lms 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 con®guration ITO/®lm/LiF± Al. The oligomer (or the polymer) ®lms 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 531 nm for the heptamer. #

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Bi-Directional Synthesis of a Series of 2,5-Dodecanoxy-phenyleneethynylene Oligomers

Synlett, 2005

A family of rigid rod like 2,5-dodecanoxy-phenyleneethynylene oligomers having 3, 5, 7, and 9 rep... more A family of rigid rod like 2,5-dodecanoxy-phenyleneethynylene oligomers having 3, 5, 7, and 9 repeating units was selectively synthesized by a bi-directional iterative divergentconvergent approach. Starting from a central 1,4-bis(dodecanoxy)-2,5-diiodobenzene monomer, only two repetitive reactions were involved with each cycle of oligomerization: a Pd/Cu cross-coupling with the bifunctional monomer 1-(3,3-diethyltriazene)-2,5bis(dodecanoxy)-4-(ethynyl)benzene, generating oligomers with terminal triazene groups, followed by a further nucleophilic substitution with iodine.

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Photoluminescence of epoxy/clay nanocomposites

Polymer Engineering & Science, 2011

Polymer nanocomposites of an epoxy resin with natural montmorillonite (MMT), organically modified... more Polymer nanocomposites of an epoxy resin with natural montmorillonite (MMT), organically modified montmorillonite(OMMT), and halloysite nanotubes(HNTs) were prepared by the solvent casting method. Photoluminescence (PL) measurements showed that the epoxy nanocomposites with OMMT and HNTs give rise to a red-shift of the emission band associated to bisphenol groups and to well resolved emission spectra, attributable to coplanar packing of the polymer chains in the excited states. A significant PL quenching in all the nanocomposites was observed, which depended on type and clay concentration. Atomic force microscopy (AFM) images showed a greater penetration of the epoxy resin only into the OMMT and HNT agglomerates. A relationship between the PL behavior and both the extent of confinement of polymer chains in clays agglomerates and the changes in the formation of trapping sites produced from hydroxyl groups could be revealed by AFM images and Fourier transform infrared spectroscopy (FTIR) studies.

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