1,721,028 research outputs found
Poly(Pyridinium Phenylene)s: Water-Soluble N-Type Polymers
No full textPoly(pyridinium phenylene) conjugated polymers are synthesized by a cross-coupling and cyclization sequence. These polyelectrolytes are freely soluble in water and display high degrees of electroactivity. When reduced (n-doped) these materials display in situ conductivities as high as 160 S/cm. The high conductivity is attributed to the planar structure that is enforced by the cyclic structures of the polymer. The electron affinities are compared to PCBM, a C[subscript 60] based n-type material. We find that these polymers undergo excited state electron transfer reactions with other donor conjugated polymers and hence may find utility in photovoltaic devices.National Science Foundation (U.S.) (DMR-0706408)Toray Industries, Inc
Detection and Differentiation of Neutral Organic Compounds by [superscript 19]F NMR with a Tungsten Calix[4]arene Imido Complex
No full textFluorinated tungsten calix[4]arene imido complexes were synthesized and used as receptors to detect and differentiate neutral organic compounds. It was found that the binding of specific neutral organic molecules to the tungsten centers induces an upfield shift of the fluorine atom appended on the arylimido group, the extent of which is highly dependent on electronic and steric properties. We demonstrate that the specific bonding and size-selectivity of calix[4]arene tungsten–imido complex combined with [superscript 19]F NMR spectroscopy is a powerful new method for the analysis of complex mixtures.National Institute of General Medical Sciences (U.S.) (Grant GM095843)Shanghai Institute of Organic Chemistry (SIOC Postdoctoral Fellowship
Strain Release in Organic Photonic Nanoparticles for Protease Sensing
No full textProteases are overexpressed in most cancers and proteolytic activity has been shown to be a viable marker for cancer imaging in vivo. Herein, we describe the synthesis of luminescence-quenched shell cross-linked nanoparticles as photonic nanoprobes for protease sensing. Protease sensing scheme is based on a “turn-on” mechanism where the protease cleaves peptide cross-linkers of the fluorescence-quenched shell cross-linked NP (OFF state) leading to a highly emissive non-cross linked NP (ON state). The cross-linked particles can be strained by exposure to a good solvent and proteolysis allows for particle expansion (swelling) and a recovery of the luminescence.United States. Air Force Office of Scientific Research (FA9550-10-1-0395)Spain. Ministerio de Ciencia e Innovación (postdoctoral grant
Robust Cyclohexanone Selective Chemiresistors Based on Single-Walled Carbon Nanotubes
No full textFunctionalized single-walled carbon nanotube (SWCNT)-based chemiresistors are reported for a highly robust and sensitive gas sensor to selectively detect cyclohexanone, a target analyte for explosive detection. The trifunctional selector has three important properties: it noncovalently functionalizes SWCNTs with cofacial π–π interactions, it binds to cyclohexanone via hydrogen bond (mechanistic studies were investigated), and it improves the overall robustness of SWCNT-based chemiresistors (e.g., humidity and heat). Our sensors produced reversible and reproducible responses in less than 30 s to 10 ppm of cyclohexanone and displayed an average theoretical limit of detection (LOD) of 5 ppm.Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (W911NF-13-D-0001
Synthesis of a Water-Soluble 1,3-Bis(diphenylene)2-phenylallyl Radical
No full textThe design and synthesis of a water-soluble 1,3-bis(diphenylene)-2-phenylallyl (BDPA) radical via the conjugate addition of a derivatized fluorene nucelophile is described. The compound is designed for use in dynamic nuclear polarization NMR. Its 9 GHz EPR spectrum in glycerol/water is reported.National Science Foundation (U.S.)National Institute of Biomedical Imaging and Bioengineering (U.S.) (EB-002804
Conjugated Amplifying Polymers for Optical Sensing Applications
No full textThanks to their unique optical and electrochemical properties, conjugated polymers have attracted considerable attention over the last two decades and resulted in numerous technological innovations. In particular, their implementation in sensing schemes and devices was widely investigated and produced a multitude of sensory systems and transduction mechanisms. Conjugated polymers possess numerous attractive features that make them particularly suitable for a broad variety of sensing tasks. They display sensory signal amplification (compared to their small-molecule counterparts) and their structures can easily be tailored to adjust solubility, absorption/emission wavelengths, energy offsets for excited state electron transfer, and/or for use in solution or in the solid state. This versatility has made conjugated polymers a fluorescence sensory platform of choice in the recent years. In this review, we highlight a variety of conjugated polymer-based sensory mechanisms together with selected examples from the recent literature.Massachusetts Institute of Technology. Institute for Soldier Nanotechnologie
Synthesis and Optical Properties of Phenylene-Containing Oligoacenes
No full textSynthesis of a new class of fully unsaturated ladder structures, phenylene-containing oligoacenes (POAs), using 3,4-bis(methylene)cyclobutene as a building block for sequential Diels–Alder reactions is described. The geometric effects of strain and energetic cost of antiaromaticity can be observed via the optical and electrochemical properties of the reported compounds. The resulting shape-persistant ladder structures contain neighboring chromophores that are partially electronically isolated from one another while still undergoing a reduction in the band gap of the material.National Science Foundation (U.S.) (DMR-1005810)National Science Foundation (U.S.) (CHE-0946721)United States. Dept. of Energy. Center for Excitonics (Award DE-SC0001088
Chain-Growth Polymerization of 2-Chlorothiophenes Promoted by Lewis Acids
No full textLewis acids promote the polymerization of several 2-chloroalkylenedioxythiophenes, providing high-molecular-weight conjugated polymers. The proposed mechanism is a cationic chain-growth polymerization, as confirmed by end-capping reactions and a linear correlation of molecular weight with percent conversion. The “living” character of this process was used to prepare new block copolymers.United States. Air Force Office of Scientific Research (FA9550-10-1-0395
Bispyridinium-phenylene-based copolymers: low band gap n-type alternating copolymers
No full textBispyridinium-phenylene-based conjugated donor–acceptor copolymers were synthesized by a Stille cross-coupling and cyclization sequence. These polyelectrolytes are freely soluble in organic solvents and display broad optical absorption bands that extend into the near-infrared region. They show ambipolar redox properties with high electron affinities (LUMO levels) of 3.9–4.0 eV as well as high degrees of electroactivity. When reduced (n-doped) these materials display in situ conductivities as high as 180 S/cm. The high conductivity is attributed to the planar structure that is enforced by the cyclic structures of the polymer. The electron affinities are compared to PCBM, a C[subscript 60] based n-type material and hence may find utility in photovoltaic devices.National Science Foundation (U.S.) (DMR-0706408
Triptycene Diols: A Strategy for Synthesizing Planar pi Systems through Catalytic Conversion of a Poly(p-phenylene ethynylene) into a Poly(p-phenylene vinylene)
No full textAt level best: A strategic synthesis of a new class of poly(p-phenylene vinylene)-bearing annulated alkene units from a parent poly(p-phenylene ethynylene) is described (see scheme). The gold-mediated cycloisomerization reaction of alkynes with appended hydroxy-group reacting partners delivers products having a stark increase in chain rigidity and planarity, as evidenced by pronounced photophysical changes.Natural Sciences and Engineering Research Council of Canada (NSERC)National Institutes of Health (U.S.). Bioengineering Research Partnership (Grant R01 AG026240-01A1
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