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Two series of 2,5-di(butoxy)phenyleneethynylenes, one halogenated (nPEC4-X; n=2, 3, or 4) and the other boron-dipyrromethene (BODIPY) terminated (nPEC4-By; n=3, 4, or 5; By=BODIPY), were synthesized monodirectionally by the step-by-step approach and the molecular structure was corroborated by NMR spectroscopy (1 H, 13 C-DEPTQ-135, COSY, HSQC, HMBC, 11 B, 19 F) and MALDI-TOF mass spectrometry. The multiplicity and J-coupling constants of 1 H, 11 B, and 19 F/11 B NMR signals revealed, in the nPEC4-By series, that the phenyl in the meso position of BODIPY becomes electronically part of the conjugation of the phenyleneethynylene chain, whereas BODIPY is electronically isolated. The photophysical, electrochemical, and theoretical studies confirm this finding because the properties of nPEC4-By are comparable to those of the nPEC4-X oligomers and BODIPY, indicating negligible electron communication between BODIPY and the nPEC4 moieties. Nevertheless, energy transfer (ET) from nPEC4 to BODIPY was rationalized by spectroscopy and theoretical calculations. Its yield decreases with the nPEC4 conjugation length, according to the increase in distance between the two chromophores, resulting in dual emission for the longest oligomer in which ET is quenched.

A series of water soluble 8-alcoxypyrene-1,3,6-trisulfonic sodium salts bearing different alcoxy lateral chains and functional end groups was synthesized and the molecular structure was corroborated by nuclear magnetic resonance spectroscopy. The photophysical properties in water analyzed by UV-Vis and static and dynamic fluorescence revealed that all of the pigments emit in the blue region at a maximal wavelength of 436 nm and with fluorescence lifetimes in the range of ns. Among them, sodium 8-((10-carboxydecyl) oxy) pyrene-1,3,6-trisulfonate M1 exhibits a high fluorescence quantum yield (ϕ = 80%) and a good interaction with B. subtilis LPM1 rhizobacteria; this has been demonstrated through in vitro staining assays. Tomato plants (Solanum lycopersicon cv. Micro-Tom) increased the release of root exudates, mainly malic and fumaric acids, after 12 h of treatment with benzothiadiazole (BTH) as a foliar elicitor. However, the chemotaxis analysis demonstrated that malic acid is the most powerful chemoattractant of the rhizobacteria Bacillus subtilis LPM1: in agar plates, a major growth (60 mm) was found for a concentration of 100 mM, while in capillary tubes, the earliest response was at 30 min with 3.3 × 108 CFU mL−1. The confocal microscopic analysis carried out on the tomato roots of the pyrene stained B. subtilis LPM1 revealed that this bacterium mainly colonizes the epidermal zones, i.e. the junctions to primary roots, lateral roots and root hairs, meaning that these root hair sections are the highest colonisable sites involved in the biosynthesis of exudates. This fluorescent pyrene marker M1 represents a valuable tool to evaluate B. subtilis–plant interactions in an easy and quick test in both in vitro and in vivo tomato crops.

A couple of luminescent organotin compounds derivated from ligands-ONO were obtained by multicomponent microwave assisted synthesis in short time (15 min) and good yields: ((E)-8, 8-8-diphenylbenzo[d] naphtho [1,2-h][1,3,6,2] dioxazastannonine (1) and (E)11, 13- di-tert-butyl, 8- diphenylbenzo [d] naphtho [1,2-h][1,3,6,2] dioxazastannonine (2)). Both compounds were fully characterized by NMR (1H, 13C, and 119Sn; 2D-NMR, HETCOR and COSY), UV–Vis, IR, and high-resolution mass spectrometry. The X-ray structures of two complexes demonstrate that the tin atoms adopt a bipyramidal trigonal geometry. The 119Sn NMR chemical shifts of the tin atom in the complexes are also consistent with the presence of pentacoordinate tin centers. The photophysical properties in solution and solid state, DFT, and voltammetry the two complexes have been determined.

This article belongs to the Special Issue Laser Spectroscopy., In this work we report on the spectroscopic properties and the near-infrared to visible upconversion of Er3+ ions in aluminosilicate glasses manufactured by directionally solidification with the laser floating zone technique. Glasses were manufactured in a controlled oxidizing atmosphere to provide them with high optical transmission in the visible spectral range. Absorption and emission spectra, and lifetimes were assessed in both the visible and the near infrared spectral range. Green upconversion emissions of the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions at 525 nm and 550 nm attributed to a two-photon process were observed under excitation at 800 nm. Mechanisms responsible for the upconversion luminescence were discussed in terms of excited state absorption and energy transfer upconversion processes. Excitation spectra of the upconverted emission suggest that energy transfer upconversion processes are responsible for the green upconversion luminescence., This research was funded by the PIT2 program of the University of Murcia’s own research plan. Fundación Séneca grant No 20647/JLI/18 and European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie IF No 795630 are also acknowledged.

The preparation of a recyclable palladium complex supported on coated silica nanoparticles (SiNP) and its effectiveness as a catalyst in the Heck reaction is described. Functionalized silica-based NP were synthesized in three steps. First, commercial SiNP were subjected to a CS2 cold plasma. Thus, a thin coating film was formed, along with the creation of a thiol functional surface. Subsequently, a thiol-ene reaction with 2-vinylpyridine induced by AIBN produced (Py)-CH2-CH2S covalently bonded to the SiNP, which after PdCl2(CH3CN)2, ligand exchange afforded the corresponding palladium complex catalyst (Pd-SiNP). Functionalized Pd-SiNP were characterized by SEM, ICP, and XPS spectroscopy. The SiNP were straightforwardly converted to an effective palladium catalyst applicable in a number of Heck cross-coupling reactions with iodobenzene (IBz) and a variety of vinyls. Indeed, such heterogeneous catalyst probed to be recyclable (up to 9 times). Nevertheless, leaching of metal was evidenced by TEM, HRTEM, XRD, and XPS. Furthermore, due to the outstanding results, we extended the use of the new heterogeneous catalyst to achieve the synthesis of a soluble phenylenevinylene type (PPV) copolymer from 1,4-bis(dodecyloxy)-2,5-diiodobenzene and p-divinylbenzene (DVB).

A series of hydrogen, iodine and triazene terminated (dodecyl)benzoateethynylene oligomers and the homologue polymer were synthesized by a divergent–convergent step-by-step approach and characterized by NMR (1H, 13C, HSQC) and MALDI-TOF mass spectrometry. The photophysical properties in CH2Cl2 were analyzed by UV-vis and static and dynamic fluorescence revealing that all of the materials are semiconducting with good fluorescence quantum yields ϕ and lifetimes in the range of ns. The type of terminal group in the oligomers, H, I or triazene, has an important effect on both absorption and emission properties, with the maximum red shifts for I and triazene and with a larger bathochromic effect for the triazene oligomers. The structural distortion of the conjugated backbone increases with the benzoateethynylene moieties (BzE) in the hydrogen terminated oligomers (trimer, pentamer and heptamer) as found by theoretical simulations, which explains why the saturation of the effective conjugation is found for the heptamer (8 nm with respect to the polymer). The hydrogen terminated pentamer showed the highest quantum yield of the series with ϕ = 77%, is soluble in N-methylpyrrolidone and displays a strong CC vibration Raman signal. Its application in staining the Gram-positive Bacillus subtilis and Gram-negative Escherichia coli was investigated under in vitro conditions and was successfully demonstrated by fluorescence and microRaman spectroscopy and laser scanning confocal microscopy.

Hollow ZnO microspheres were successfully synthesized by a hydrothermal method and then functionalized with graphene oxide (GO) flakes, previously obtained through electrochemical oxidation. Their photocatalytic activity toward the photodegradation of salicylic acid under UV light irradiation was evaluated by UV-Vis spectroscopy. Unfunctionalized microspheres and ZnO functionalized with chemically oxidized graphene were also studied as comparative terms. The hybrid materials of ZnO with both electrochemical and chemical GO gave a similar photodegradation yield of ∼28% against 18% of the non-functionalized microspheres. The similar degradation yields and rate constants obtained with the two GO synthetic methods indicate that electrochemical oxidation of GO represents an eco-friendly option over traditional methods for photocatalytic degradation systems.

In this investigation strontium aluminate phosphors ( SrAl 2 O 4 :Eu,Dy ) were synthesized through two modified routes, sol-gel method (route of Pechini) and molten salts (activated by mechanosynthesis) . The slight modifications allow to use lower temperatures and shorter times of thermal treatments than those typically used. Moreover, the synthesis is performed under a simple air atmosphere. The intermediates identified during the synthesis by sol gel are: polyesters, probably coordinated to metallic ions, the cubic Pb[NO 3 ] 2 -type structure of Sr(NO 3 ) 2 , and the orthorhombic aragonite-type structure of SrCO 3 . The intermediates identified during the synthesis by molten salts are: highly crystalline NaNO 3 (obtained by the manual milling of reactants), the monoclinic bayerite-type structure of Al(OH) 3 and the orthorhombic aragonite-type structure of SrCO 3 . The results of the characterization of these intermediates provided worthy information to propose the experimental conditions of reaction. The XRD characterization of products, obtained by both methods, shows the monoclinic stuffed tridymite-type structure of SrAl 2 O 4 as predominant polycrystalline phase with a calculated mean particle size of ~26 nm. Transmission electron micrographs reveal particles with different morphology and broad distribution of sizes. HRTEM images discard the presence of amorphous phases and SAED patterns corroborate the presence of the crystalline phases previously identified by XRD. The persistent afterglow emission is centered close to the white light with a dominant wavelength of 550 nm and purity color of 0.45. The persistent emission lifetime is similar, at around 7 min, value that is sufficient for bio-imaging or security codes applications.

Fluorescent nanohybrids materials were fabricated from organosilane-functionalized halloysite nanotubes (HNTs), covalently bonded to new mixed-valence Cu(I,II) complex CuICuII(HOBt)2⋅CH3OH (HOBt = 1-hydroxybenzotriazole)]. Morphology, composition and optical properties of nanohybrids were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDXS), Fourier transform-infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and steady-state fluorescencec. The copper (I, II) complex was also characterized for the sake of comparison. Molecular immobilization and molecular geometry changes due to halloysite environment changed the photoluminescence behavior of the copper (I,II) complex, allowing HNTs-g-CuICuII(HOBt)2⋅CH3OH nanohybrids to display a tri-component light as observed by fluorescence microscopy, making them an interesting option for attaining white light.

Change of the permanent molecular electric dipole moment, Δμ, in a series of nominally centrosymmetric and noncentrosymmteric ferrocene-phenyleneethynylene oligomers was estimated by measuring the two-photon absorption cross-section spectra of the lower energy metal-to-ligand charge-transfer transitions using femtosecond nonlinear transmission method and was found to vary in the range up to 12 D, with the highest value corresponding to the most nonsymmetric system. Calculations of the Δμ performed by the TD-DFT method show quantitative agreement with the experimental values and reveal that facile rotation of the ferrocene moieties relative to the organic ligand breaks the ground-state inversion symmetry in the nominally symmetric structures.

Two new fluorescent organotin compounds bearing C3-symmetric Schiff base were synthesized by microwave irradiation via multicomponent reaction (3-MCR), in one pot in just 30 mins with excellent yields. Both tin complexes were fully characterized by NMR, IR, UV-vis, fluorescence spectroscopy, high-resolution mass spectrometry and by ciclyc voltametry. The δ 119Sn and 3J(1H,119Sn) of new organotin complexes 4 and 5 showed the high molecular symmetry and the trinuclearity through high resolution mass spectrometry. Both Sn-complexes are thermally stable up to 300°C. The small-wide angle X-ray scattering pattern in powder and the 2D monomolecular film by scanning tunneling microscopy (STM) of 5 showed a lamellar like assembly with dimension of 2.38 and 2.80 nm, respectively, meaning that molecules adopt a face-on arrangement, where molecules are flat-lying on the HOPG surface. Monolayer of 5 is mesoporous and rigid but covers large surface areas. The photophysical, electrochemical, and theoretical studies reveal that the three Sn-nuclei do not electronically interact. Since, both organotin complexes exhibit good quantum yield in solution (Φ 4: 52.4 % and 5: 51.7 %), with lifetimes in the range τ =∼3 ns, their emission properties are appealing for OLED applications.

Four organotin compounds bearing Schiff bases were prepared via a multicomponent microwave-assisted reaction among 2-hydroxy-1-naphthaldehyde, 2-aminophenol derivatives and the corresponding diorganotin oxide (R2SnO, R = nBu or Ph), with high yields and a low economic/environmental impact. All of the compounds were fully characterized by NMR (1H, 13C, and 119Sn) spectroscopy, high-resolution mass spectrometry, X-ray diffraction, cyclic voltammetry, UV/Vis spectroscopy, and fluorescence spectroscopy. All of the compounds absorb in the visible region around 480–490 nm, close to the maximum solar emission, with an optical band gap of around 2.3 eV and low fluorescence quantum yields. According to the electrochemical study, they present LUMO values close to that of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM-C60), a typical electron acceptor organic photovoltaic material. Based on this combined optical/electrochemical study and as it allows the preparation of homogeneous spun films, the n-butyltin complex with carboxylic acid was selected for the investigation of its possible photovoltaic properties in organic solar cells. Charge photogeneration was obtained only using this organotin compound as an electron acceptor material with poly(3-hexylthiophene, P3HT) (typical electron donor material) with an open circuit voltage of 300 mV, a short-circuit current density of 0.11 mA cm−2 and an efficiency of 5.2 × 10−3%. Despite the fact that the efficiency is much lower with respect to the reference device P3HT/PCBM-C60, this preliminary result suggests that, after chemical and device processing optimization, tin complexes with Schiff bases could be applied as electron acceptor materials in organic photovoltaic devices.

Unaligned and aligned poly(9-vinylcarbazole) (PVK)/NaEu(TTA)4 (TTA=2-thenoyltrifluoracetone) composite fibers were prepared by electrospinning, using tetrahydrofuran (THF) and 1,2-dichoroethane (DCE) as solvents. Scanning electron microscopy (SEM) measurements showed that aligned fibers were wider and thicker than unaligned fibers. Characterization by Fourier transform-infrared (FTIR) spectroscopy indicated that there were weak interactions between PVK and NaEu(TTA)4. Alignment of composite fibers promoted packing of the molecules of the Eu(III)-complex, increased the population of fully overlapping carbazoles (f-PVK) and decreased the asymmetric ratio (R) of the NaEu(TTA)4, leading to less efficient energy transfer and lower lifetimes, as determined using steady-state and dynamic fluorescence spectroscopy. Yet, shorter lifetimes as compared to NaEu(TTA)4 in powder form were found in unaligned and aligned electrospun fibers, ascribed mainly to introduction of defect states during electrospinning. Unaligned electrospun PVK fibers doped with loosen packed europium complexes preferably could be used as promising luminescence materials.

Two methacrylate monomers, carrying a p -terphenyl laterally substituted with one or two cyano groups, were synthesized and studied from the liquid crystal and optical points of view. The synthetic route involved several reactions, including the Suzuki reaction that allows the coupling of aryl groups. The chemical structure of these new monomers, as well as that of their corresponding precursors, was confirmed by 1 H and 13 C NMR spectroscopies. The mesomorphic behavior of both monomers and precursors was studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD) analyses. Molecules bearing one cyano group melt at lower temperature and display a mesomorphic behavior over larger temperature intervals as compared to those bearing two cyano groups. The four compounds (two monomers and two precursors) showed only non-ordered smectic phases. By X-ray diffraction it was determined that molecules stack in single layers within the smectic phase, except for one of the monomers that stacks in double layers. The electrochemical characterization revels that these molecules behaves as p type materials, and that their electronic nature (band gap) can be modulated by introducing CN groups. The molecules absorb and emit in the blue spectral range, a region of high energy light. The large Stokes' shifts indicate that the geometry of the molecules changes from aromatic in the electronic ground state to a more coplanar quinoid structure in the first excited state. The fluorescence quantum yield is high (70–80%) suggesting that these new monomers can be used as precursors for the synthesis of fluorescent liquid crystal polymers, which is a work in progress.

The fabrication, molecular structure, and spectroscopy of a stable cholesteric liquid crystal platinum acetylide glass obtained from trans‐Pt(PEt(3))(2)(C≡C−C(6)H(5)−C≡N)(C≡C−C(6)H(5)−COO−Cholesterol), are described and designated as PE1‐CN‐Chol. Polarized optical microscopy, differential scanning calorimetry, and wide‐angle X‐ray scattering experiments show room temperature glassy/crystalline texture with crystal formation upon heating to 165 °C. Further heating results in conversion to cholesteric phase. Cooling to room temperature leads to the formation of a cholesteric liquid crystal glass. Scanning tunneling microscopy of a PE1‐CN‐Chol monolayer reveals self‐assembly at the solid−liquid interface with an array of two molecules arranged in pairs, oriented head‐to‐head through the CN groups, giving rise to a lamella arrangement. The lamella structure obtained from molecular dynamics calculations shows a clear phase separation between the conjugated platinum acetylide and the hydrophobic cholesterol moiety with the lamellae separation distance being 4.0 nm. Ultrafast transient absorption and flash photolysis spectra of the glass show intersystem crossing to the triplet state occurring within 100 ps following excitation. The triplet decay time of the film compared to aerated and deoxygenated solutions is consistent with oxygen quenching at the film surface but not within the film. The high chromophore concentration, high glass thermal stability, and long triplet lifetime in air show that these materials have potential as nonlinear absorbing materials.

Made available in DSpace on 2018-11-26T17:06:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-11-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Mexican National Council for Science and Technology (CONACYT, Mexico) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) CONACYT 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 430 nm, the polydispersity index was below 0.2, and the zeta potential was around -13 mV. 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 4 days. 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. (C) 2016 Elsevier B.V. All rights reserved. State Univ Sao Paulo, Dept Environm Engn, UNESP, Sorocaba, SP, Brazil State Univ Campinas UNICAMP, Inst Biol, Dept Biochem, Campinas, SP, Brazil CIQA, Blvd Enrique Reyna 140, Saltillo 25294, Coahuila, Mexico State Univ Sao Paulo, Dept Environm Engn, UNESP, Sorocaba, SP, Brazil FAPESP: 2014/20273-4 FAPESP: 2014/20286-9 FAPESP: 2013-12322-2 FAPESP: 2015/15617-9 Mexican National Council for Science and Technology (CONACYT, Mexico): 229761/INFR-2014-02 CNPq: 174806 CONACYT: 270878

Nine novel 2-aryl-6-(aryleneethynylene)-1H-indoles were prepared by one pot Sonogashira cross-coupling in DMSO and fluoride promoted cyclization followed by N-alkylation. The photophysical properties of these compounds are described. Absorption and excitation spectra of these compounds were independent of the solvent polarity, while their emission spectra showed a pronounced dependence. Fluorescence quantum yields in solution were very high and decreased with solvent polarity; possible processes that account for excessive values of ϕ are discussed. Cyclic voltammetry studies indicate irreversible redox processes and DFT calculations suggest they occur in the indole segment.

In this work, luminescent composite fibers were prepared by electrospinning of polylactic acid (PLA) and polysulfone (PSU) solutions containing the europium complex Eu(tta)3(phen) (tta = 2-thenoyltrifluoracetonato; Phen = 1,10-phe3nantroline). The structural and optical properties were investigated using scanning electron microscopy, transmission electron microscopy, Fourier transform-infrared spectroscopy, and fluorescence spectroscopy. Cylindrical PLA and ribbon-like planar PSU fibers were obtained. The Eu complex was dispersed in the PLA and PSU fibers in the form of crystals of irregular shape with sizes in the range of 150–300 nm and led both type of fibers to emit a bright red fluorescence under UV-illumination. FTIR analysis showed that the Eu O bond is affected by the polymer matrices although there were no considerable interactions between them. Fluorescence spectra studies revealed that the coordination environment of the Eu3+ ion changed resulting in an increased calculated asymmetric ratio as compared with that of the Eu pure complex. These results suggest the potential of electrospinning to prepare luminescent polymers in which biodegradability could be a desired property.

Here we report a green one-pot microwave-assisted synthesis of four push–pull organotin complexes derived from Schiff bases in good yields, which provides advancement over conventional method as it is simple, cost-effective and reproducible. All compounds were characterized by UV–Vis, TOF-HRMS, TGA-DTA, cyclic voltammetry, theoretical studies and compound 1 by X-ray single-crystal diffraction. Third-order nonlinear susceptibility χ(3) of complexes 1–4; ((E)-N′-(4-(diethylamino)-2-hydroxysalicylidine) nitrobenzohydrazidatediphenyl-tin (IV) (1), (E)-N′-(4-(diethylamino)-2-hydroxysalicylidine) nitrobenzohydrazidate di n-butyl-tin (IV) (2), ((E)-N′-(4-(methoxy)-2-hydroxysalicylidine) nitrobenzohydrazidate diphenyl-tin (IV) (3), (E)-N′-(4-(methoxy)-2-hydroxysalicylidine) nitrobenzohydrazidate di n-butyl-tin (IV) (4)) were measured via Maker-Fringes technique. In particular, compounds 1 and 2 display larger third-order nonlinearities than their methoxilated counterparts.

In this work, we report on the preparation of processable nanocomposites of multiwall carbon nanotubes (MWCNTs) and a conjugated copolymer, hereafter called pPET3OC12-sqS bearing a phenyleneethynylene trimer and a dithio disulfide moiety. This specific alternation of rigid and flexible units allows self-assembly of the conjugated backbone on the nanotubes wall through π- π interactions, without affecting the effective conjugation length of the polymer as found by 1HNMR, UV–Vis and fluorescence spectroscopy. The flexible sequences favour the stabilization of the composite by wrapping the MWCNTs wall as observed by electron transmission microscopy. As a result of this supramolecular arrangement, the absorption and emission maxima of the polymer are maintained but a quenching from 0.55 to 0.27 of the polymer fluorescence is found, which likely arises from efficient photoinduced electron transfer from the pPET3OC12-sqS to the MWCNTs. The incorporation of the nanotubes in the polymer matrix increases the electrical conductivity of the thin films in one order of magnitude and lowers the LUMO value, opening the possibility of a future application of the composite as electron acceptor material in organic photovoltaic devices.

We report on the scanning tunneling microscopy and small-wide angle X-ray scattering and diffraction of four linear and rigid π-conjugated p-phenyleneethynylene (PPE) oligomers. The four compounds possess two dodecanoxy side chains on the central PPE moiety, differ in conjugated length (3 and 5 phenyleneethynylene moieties) and are benzyl, Bz3PEBz, Bz5PEBz, or carboxylic acid, Ac3PEAc, Ac5PEAc, end-capped. We found that in the benzylbenzoate terminated oligomers, a staggered arrangement of molecules is obtained endorsed by the π-π interaction between the benzyls. In contrast, for the carboxylic acid terminated oligomers, a rather linear type arrangement is promoted by the hydrogen bond created between the carboxylic acid groups. In general, all of the molecules form a lamellar like pattern adopting face-on arrangements, where the conjugated backbones are flat-lying on the HOPG surface. The lamella length corresponds to the oligomer conjugation length, while within the lamellae, the calculated distances correspond to the spacing between conjugated backbones with an average value of 2.06 nm, consistent with that found by XRD, SAXS and DFT/def-SVP for the oligomers that self-assemble with the lateral alkyl chains interdigitated. The lack of more dodecanoxy side chains on the rest of the pheneyleneethynylene moieties gives rise to mesoporous type self-assembled monolayers on HOPG.

A small series of boron-dipyrromethene (BODIPY) dyes, characterized by the presence of multibranched fluorinated residues, were designed and synthesized. The dyes differ in both the position (para-perfluoroalkoxy-substituted phenyl ring or boron functionalization) and number of magnetically equivalent fluorine atoms (27 or 54 fluorine atoms per molecule). Photophysical and crystallographic characterization of the synthesized BODIPYs was carried out to evaluate the effect of the presence of highly fluorinated moieties on the optical and morphological properties of such compounds.

A phenylenedivinylidenebisquinoline oligomer was obtained by reacting quinaldine with 2,5-bis(octyloxy)terephtalaldehyde via the Knoevenagel reaction by mechanosynthesis. The product was characterized by 1H Homo-J-Resolved NMR, 13C NMR, FT-IR, Fluorescence, UV–Vis spectroscopy and by FAB+ mass spectrometry. X-ray diffraction studies indicate that the molecule is semicrystalline, while laser scanning confocal microscopy shows that the emission comes from the crystals. As a consequence, the morphology and accordingly the PL values in spun films can be changed by varying the spinning conditions. Intrinsic electroluminescent properties are reported using the ITO/M1AMec/Al single layer configuration.

A series of fulleropyrrolidines-conjugated bridge-ferrocene or triazene oligomers were selectively synthesized by the Sonogashira reaction by applying the step-by-step approach. The bridge is constituted by 1, 2 and 3 benzoateethynylene units (BzE) and bears triazene (Et2N3) or ferrocene as terminal groups affording the C60-2PEN3 and C60-3PEN3 dyads and C60-1PEFe, C60-2PEFe and C60-3PEFe triads. DQF-COSY, HETCOR, 1H and 13C NMR and the MALDI-TOF characterization clearly confirmed the expected molecular structure. The absorption spectra of the fulleropyrrolidine oligomers do not match the sum of the individual spectra: N-methylfulleropyrrolidine (NMF) and BzEs, suggesting electronic interaction between the two moieties in the ground state. The fluorescence of the BzE is strongly quenched after functionalization with NMF, which could be indicative of energy or electron transfer from the triazene or ferrocene as electron donor to the fulleropyrrolidine electron acceptor through the π-bridge. The latter process was confirmed by cyclic voltammetry. The strength of the electron-accepting group gets to increase anodically the oxidation potential, or decrease cathodically the reduction potential in the order C60-pyrrolidine > benzoate. The character of the HOMO in the series is defined by the electron-donating ferrocene or triazene moiety, whereas the character of the LUMO is mainly determined by the electron-accepting group and is further supported by theoretical calculations. Photovoltaic devices presented low efficiencies, due to the absorption range of the oligomers being out of the maximum solar irradiance and the inhomogeneous organization in the films.

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).

A perylene cholesteryl-benzoateethynylene co-polymer was synthesized by Sonogashira reaction and characterized by NMR, UV–Vis, static and dynamic fluorescence spectroscopy and cyclic voltammetry. The optical and electrochemical properties in solution are consistent with photoinduced energy transfer from the electron donor conjugated backbone to the electron acceptor perylene substituent. Photovoltaic properties are indeed found, even if the performance of the solar cells is quite low due to the formation of aggregates. The incorporation of (6,6)-phenyl C61–butyric acid methyl ester (PCBM), however, increases by an order of magnitude the efficiency of the prototype (from 10−4 to 10−3%) due to both better phase mixing and improved electrical continuity as supported by Atomic Force Microscopy (AFM) and Electrical Force Microscopy (EFM) studies.

The multicomponent reaction of the 2-hydroxynaphthaldehyde with 2-aminophenol derivatives and their in situ complexation with diphenyltin oxide in acetonitrile provided, in high yield, the products: (((E)-12-nitro-8,8-diphenylbenzo[d]naphtho[1,2-h][1,3,6,2]dioxazastannonine and (E)-11-nitro-8,8-diphenylbenzo[d]naphtho[1,2-h][1,3,6,2]dioxazastannonine), where tin atom is pentacoordinated. The synthesis of their ligands ((E)-1-(((2-hydroxy-5-nitrophenyl)imino)methyl)naphthalen-2-ol and (E)-1-(((2-hydroxy-4-nitrophenyl)imino)methyl)naphthalen-2-ol) is also reported. The chemical structure of all the compounds has been established by nuclear magnetic resonance (1H, 13C, and 119Sn), infrared spectroscopy, and high resolution mass spectrometry. The 12-nitroanalogue was characterized by single-crystal X-ray structural analysis. The structure indicates that the backbone is essentially planar and the metal center resides in trigonal bipyramid geometry. The photophysical properties of the imines and those of the tin complexes were determined in solution exhibiting quantum yields around 4% with lifetimes in the range 10−10−10−11 s. In a preliminary study, a diode was fabricated by a spun film of the 12-nitroanalogue, the device showed intrinsic electroluminescence properties with a threshold voltage at 13 V, a high current density (500 mA/cm2) but a low luminance (0.03 cd/m2).

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.

A series of substituted 2-hydroxysalicylidine benzohydrazides were converted into their phenyl-boron complexes in good yields upon reaction with phenylboronic acid. All new compounds were characterized by NMR, UV, IR, spectroscopy and mass spectrometry. The X-ray structures of two complexes demonstrate that the boron atoms adopt a tetrahedral geometry. The 11B NMR chemical shifts of the boron atom in the complexes are also consistent with the presence of tetracoordinate boron centres. The photophysical properties of the free benzohydrazide ligands and their boron complexes have been determined and display quantum yields below 1% with lifetimes in the range 10−10–10−11 s.

The synthesis of a 2,5-bis(dodecanoxy)phenyleneethynylene-butadiyne series with 2, 4, 6 and 8 phenyl rings is reported. Sonogashira coupling reaction, rather than the Glaser/Eglinton/Hay reactions classically used for butadiyne formation was applied. The molecular structures of all compounds were confirmed by 1H, DEPT-135, APT 13C, MALDI-TOF, FTIR and FT-Raman analyses. The linear and nonlinear optical properties were studied in solution by UV/Vis, static and time-resolved fluorescence, and by two-photon absorption (2PA) spectroscopy. With the exception of the dimer, for which intersystem crossing is very favoured due to the low energy gap between the singlet and triplet states as theoretically predicted, the other oligomers present high fluorescence quantum yields (0.77–0.82) and large cross-sections (up to 5000 GM for the octamer) that could be applied in multiphoton microscopy or nonlinear optics.

Escherichia coli is one the most common bacteria responsible of uropathogenic diseases, which motives the search for rapid and easy methods of detection. By taking advantage of the specific interactions between mannose and type 1 fimbriae, in this work two fluorescent phenyleneethynylene (PE) trimers bearing one or two 4-aminophenyl-?-D-mannopyranoside termini groups were synthesized for the detection of E. coli. Three bacterial strains: ORN 178 (fimbriae I expression), ORN 208 (mutant serotype with no fimbriae expression) and one obtained from a local hospital (SS3) were used. Laser Scanning Confocal Microscopy (LSCM) and Surface Plasmon Resonance (SPR) were applied for the interaction studies following two different approaches: (1) mixing the oligomer solutions with the bacterial suspension, which permitted the observation of stained bacteria and by (2) biosensing as thin films, where bacteria adhered on the surface-functionalized substrate. LSCM allows one to easily visualize that two mannose groups are necessary to have a specific interaction with the fimbriae 1. The sensitivity of SPR assays to E. coli was 104 colony forming unit (CFU)/mL at 50 µL/min flow rate. The combination of PE units with two mannose groups results in a novel molecule that can be used as a specific fluorescent marker as well as a transducer for the detection of E. coli.

Ultrafine fluorescent fibers were prepared by electrospinning of a phenyleneethynylene oligomer mixed in DMF with a poly(styrene-co-maleimide) (PSM). The microscopic characterization by SEM reveals that the fibers are smooth and entangled one to the others forming a non-woven mat with an average diameter of 490 nm. By TEM, a core-sheath type structure is observed which derives from phase segregation between the PSM interacting with the oligomer and the excess of PSM that acts as matrix, as supported by XRD and DSC analysis. The membranes are fluorescent emitting at 420 nm, in the blue region, a high energy light, opening the possibility of their application in optoelectronic devices such as fluorescent sensors. Preliminary assays have been performed for the detection of sodium ions.

Oligo(phenylimines) hereafter named PI6, PI8 and PI9 were synthesized by condensation reaction between the terephtalaldehyde and diamines of different length size (diaminohexane, diaminooctane and diaminononane) via mechanochemistry. The reactions were carried out without solvent or catalyst and completed after only 90 minutes. The products were characterized by 1H-NMR, UV-Vis, FT-IR spectroscopy, GPC, DSC and Small angle X-ray diffraction. Thin films were prepared by spin coating from concentrated solutions on glass and quartz substrates and mechanically rubbed with a polyacrylonitrile tissue. The oriented films were studied by both Laser Scanning Confocal Microscopy (LSCM) and UV-Vis spectroscopy. With this last technique, the higher optical dichroism was observed for PI6. The oriented films of this oligo(phenylimine) were thus used as patterns to induce molecular orientation of a fluorescent phenyleneethynylene polymer in order to obtain polarized light emission.

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. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

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.

Two series of 2,5-di(alkoxy)phenyleneethynylene oligomers were synthesized by Sonogashira–Heck coupling reaction. The chemical structure was corroborated by 1H, 13C, APT, DEPT-135 NMR, Raman, FTIR and MALDI-TOF mass spectrometry. The chemical structure of the molecules has been varied in order to study the effect on the physicochemical and optoelectronic properties of the different chain lengths of the lateral substituents (dodecanoxy and butoxy), of different terminal groups (H, Br and I), of different chain length (3, 5 and 7 repeat units in the main conjugated backbone). The thermal properties were analyzed by DSC, TGA and by temperature-dependent X-ray diffraction. The diffraction studies of the oligomers revealed a crystalline behavior for the butoxy series, while for the dodecanoxy series the X-ray patterns are consistent with a supramolecular organization formed of randomly distributed crystalline domains that exhibit a periodic structure at small angles, indicating the presence of a lamellar order. The optical properties can be modulated within a series by increasing the length of the conjugated oligomer chain. On the contrary, neither the length of the alkoxy substituents nor the terminal groups have effect on the shape of the absorption and emission spectra.

We report on the preparation and spectroscopic characterization of a novel nanocomposite consisting of silver nanoparticles and a fluorescent polymer obtained by in situ ps laser ablation of a silver target. While the polymer is able to detect the fungus Paecilomyces variotii by fluorescence quenching, the composite with silver nanoparticles permits an interaction with both cell walls of spores and mycelia without any appreciable reduction of the overall fluorescence quantum yield.

Silver nanoparticles have been functionalized in situ with the electrically conducting polymer, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) via colloidal synthesis. The formation of the functionalized silver nanoparticles, hereafter designated Ag(PEDOT:PSS), was confirmed by the appearance of the characteristic plasmon absorption peak at 420 nm in the UV-Vis spectrum of the aqueous suspension and by TEM analysis, where spherical particles with a mean size of around 8 nm (metallic core) were observed. Homogeneous thin films with granular topography, as observed by AFM, were prepared by self assembly. Electrical studies of the films showed an increase in electrical conductivity of three orders of magnitude with respect to the polymer film presumably due to the presence of the silver core. The conductive polymer/silver composite films also exhibit interesting electrochromic switching between blue and brown. These properties suggest the possibility of a variety of applications of Ag(PEDOT:PSS) films such as in electro optics devices, smart windows, amperometric sensors and capacitors.

Bromobenzenethiol passivated gold nanoparticles were mixed with a poly(phenylene ethynylene) bearing thioester flexible sequences in order to obtain a fluorescent composite for optical biosensors. The particles and the composite were characterized by 1H, 13C NMR, UV-Vis and fluorescence spectroscopy, TEM and STEM. The particles are homogeneously dispersed in the polymer matrix as observed by electron microscopy. The NMR spectra suggest that the gold particles and the poly(phenylene ethynylene) are probably interacting through the sulfur atoms of the –C(O)S- and –CH2-S-CH2- moieties of the flexible sequences of the polymer as well as through  interactions between the aromatic ring of 4-bromobenzenthiol and the conjugated backbone of pPET3OC12-sqS. The quantum yield of the composite both in solution and in solid state films is slightly lower than that of pPET3OC12-sqS because of the quenching effect of gold. Nonetheless, a change of the fluorescence intensity of the composite films can be detected as a consequence of the contact with microorganisms. Preliminary microbiological assays indicate an antimicrobial effect of the composite film with the E. coli bacteria.

Dendrimers with resorcinarene core and π-conjugated dendron branches with 16 and 32 stilbene groups have been synthesized and characterized by 1H and 13C NMR, FTIR, UV–vis, fluorescence spectroscopy, MALDI-TOF, electrospray or FAB+ 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 (Eg) determined from both UV–vis spectroscopy and voltammetry were in the semiconducting range. A slight decrease in the Eg values was observed when passing from the first generation of dendrimers to the second one, which can be attributed to an increase in the π-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.

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.

The influence of the buckminsterfullerene C60 on photocurrent generation and hole transport properties in polymer films of poly(styrene) (PS) doped with N,N′-bis-(3-tolyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (TPD), has been determined and analyzed by using the time-of-flight technique (TOF). Measurements were realized on indium–tin oxide/polymer composites/indium–tin oxide samples. The dependence of the charge mobility as a function of the electric field and temperature was investigated and analyzed by using the Gaussian disorder model. An enhancement of photocurrent and hole mobility was observed with increasing the C60 concentration from 0 to 2 wt.%.

In this paper, we report the crossed aldol condensation between the acetone and the 2,5-bis(octyloxy)-terephthalaldehyde (OTP) to obtain new photoluminescent oligomers as potential candidates for the construction of organic luminescent diodes (OLED’s). The reaction is carried out in ethanol as solvent, but when THF is added to the reaction medium as co-solvent, a higher molecular weight can be obtained. The analysis of the structure of the product obtained when THF is added was elucidated by 1H NMR, infrared, ultraviolet-visible (UV-Vis) and fluorescence spectroscopy and the results indicate that the number of repetitive units corresponds with that of a tetramer with an excellent solubility in common organic solvents and intense fluorescence in the green region. Moreover it can be processed by self-assembly in homogeneous thin films with controlled thickness. These results are promising in view of the possible application of this oligomer in electroluminescent diodes.

A family of rigid rod like 2,5-dodecanoxy-phenylene-ethynylene oligomers having 3, 5, 7, and 9 repeating units was selectively synthesized by a bi-directional iterative divergent-convergent 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)-2,5-bis(dodecanoxy)-4-(ethynyl)benzene, generating oligomers with terminal triazene groups, followed by a further nucleophilic substitution with iodine.

Two urethane carbazolyldiacetylenes, 6-(N-Carbazolyl)hexa-2,4-diyn-1-ol-1acetate buthyl urethane and 9-(N-carbazolyl)nona-5,7-diyn-1-ol-acetate buthyl urethane (hereafter named CHBU and CNBU, respectively), which present methylene spacers with different length between the urethane and diacetylene moieties, have been synthesized in order to obtain a conjugated polymer for non linear optics. The UV polymerization is studied by UV-Vis spectroscopy in polymeric films prepared by mechanical alignment of the monomer powder on hot substrates followed by UV polymerization. PolyCHBU films containing residual monomer exhibit thermochromic properties from blue to red form while no spectroscopic changes are observed for the polyCNBU films upon temperature. For polyCHBU, both blue and red films present also optical dichroism as observed by polarized UV-Vis spectroscopy, polarized microscopy and AFM.

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.

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 1H, DEPT-135, APT, 13C 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.