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Conjugated Polymers (conjugated + polymer)
Kinds of Conjugated Polymers Selected AbstractsConjugated Polymer Based on Polycyclic Aromatics for Bulk Heterojunction Organic Solar Cells: A Case Study of Quadrathienonaphthalene Polymers with 2% EfficiencyADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Shengqiang Xiao Abstract Polycyclic aromatics offer great flexibility in tuning the energy levels and bandgaps of resulting conjugated polymers. These features have been exploited in the recent examples of benzo[2,1- b:3,4- b']dithiophene (BDT)-based polymers for bulk heterojunction (BHJ) photovoltaics (ACS Appl. Mater. Interfaces2009, 1, 1613). Taking one step further, a simple oxidative photocyclization is used here to convert the BDT with two pendent thiophene units into an enlarged planar polycyclic aromatic ring,quadrathienonaphthalene (QTN). The reduced steric hindrance and more planar structure promotes the intermolecular interaction of QTN- based polymers, leading to increased hole mobility in related polymers. As-synthesized homopolymer (HMPQTN) and donor,acceptor polymer (PQTN - BT) maintain a low highest occupied molecular orbital (HOMO) energy level, ascribable to the polycyclic aromatic (QTN) moiety, which leads to a good open-circuit voltage in BHJ devices of these polymers blended with PCBM ([6,6]-phenyl-C61 -butyric acid methyl ester; HMPQTN: 0.76,V, PQTN - BT: 0.72,V). The donor,acceptor polymer (PQTN - BT) has a smaller optical bandgap (1.6,eV) than that of HMPQTN (2.0,eV), which explains its current (5.69,mA,cm,2) being slightly higher than that of HMPQTN (5.02,mA,cm,2). Overall efficiencies over 2% are achieved for BHJ devices fabricated from either polymer with PCBM as the acceptor. [source] DNA Detection: Intercalating Dye Harnessed Cationic Conjugated Polymer for Real-Time Naked-Eye Recognition of Double-Stranded DNA in Serum (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Mater. On page 1371, Liu Bin and Pu Kan-Yi demonstrate multicolor detection of double-stranded DNA in biological media using an intercalating-dye-harnessed cationic conjugated polymer. As demonstrated in the cover image, the intercalating-dye-harnessed polymer emits blue fluorescence both in the absence and presence of single-stranded DNA in serum-containing solution, while its fluorescence gradually turns from blue to dark yellow with increasing double-stranded DNA concentration. [source] Intercalating Dye Harnessed Cationic Conjugated Polymer for Real-Time Naked-Eye Recognition of Double-Stranded DNA in SerumADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Kan-Yi Pu Abstract Thiazole orange (TO), an intercalating dye, is integrated into cationic poly(fluorene- alt -phenylene) (PFP) to develop a macromolecular multicolor probe (PFPTO) for double-stranded DNA (dsDNA) detection. This polymer design not only takes advantage of the high affinity between TO and dsDNA to realize dsDNA recognition in biological media, but also brings into play the light-harvesting feature of conjugated polymers to amplify the signal output of TO in situ. PFPTO differentiates dsDNA from single-stranded DNA (ssDNA) more effectively upon excitation of the conjugated backbone relative to that upon direct excitation of TO as a result of efficient fluorescence resonance energy transfer from the polymer backbone to the intercalated TO. In the presence of dsDNA, energy transfer within PFPTO is more efficient as compared to that for free TO/PFP system, which leads to better dsDNA discriminability for PFPTO in contrast to that for TO/PFP. The distinguishable fluorescent color for PFPTO solutions in the presence of dsDNA allows naked-eye detection of dsDNA with the assistance of a hand-held UV lamp. The significant advantage of this macromolecular fluorescent probe is that naked-eye detection of label-free dsDNA can be performed in biological media in real-time. [source] A Conjugated Polymer for Near Infrared Optoelectronic Applications,ADVANCED MATERIALS, Issue 20 2007E. Perzon A new conjugated polymer, LBPP-1, with an unusually low band-gap (ca.,1.0,eV) is presented. Light absorption and photovoltaic response up to 1200,nm in composites with a fullerene is demonstrated. Solar cell performance is presented and the polymer's suitability for photodetection in the infrared region is discussed. [source] Revealing the Electron,Phonon Coupling in a Conjugated Polymer by Single-Molecule Spectroscopy,ADVANCED MATERIALS, Issue 15 2007R. Hildner Electron,phonon coupling in a ,-conjugated polymer is revealed by single-molecule spectroscopy in combination with statistical pattern recognition techniques. The technique allows to reveal the phonon-side band in the spectra of methyl-substituted ladder-type poly(para-phenylene) (see figure). For this polymer a weak electron,phonon coupling strength is found at low temperatures. The distribution of the phonon frequencies provides strong evidence that the low-energy vibrational modes, which couple to the electronic transitions, stem from vibrations of the host matrix. [source] Efficient Hybrid Solar Cells from Zinc Oxide Nanoparticles and a Conjugated Polymer,ADVANCED MATERIALS, Issue 12 2004ZnO nanoparticles dispersed in a semiconducting polymer form the active layer of a solar cell (see Figure) that is able to convert up to 40,% of the incident photons at 500,nm into electrical current and has a power conversion efficiency of about 1.5,% in sunlight. Manufactured at low temperature using environmentally friendly materials, it represents a new step to ,green electricity'. [source] A Water-Soluble ,-Conjugated Polymer with up to 100 mg,·,mL,1 SolubilityMACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2007Huiping Wang Abstract A cationic water-soluble polyfluorene (P2) containing a high density of tetraalkylammonium side chains in polymer backbone was synthesized and characterized. The polymer shows excellent water solubility up to 100 mg,·,mL,1 as well as high photoluminescence (PL) quantum yield of 44% in water. The relatively high cationic density and appropriate side chain length of the polymer are the key factors to achieve such high water solubility. The reduction potential of P2 is decreased as compared with its neutral polymer, reflecting the enhanced electron injection abilities. The standard NPB/Alq3 device using such a polymer as the electron injection layer shows nearly three-fold enhancement in the electroluminescence (EL) efficiency. [source] Synthesis, Photophysics and Morphology of a Conjugated Polymer with Azobenzene Building Block in the BackboneCHINESE JOURNAL OF CHEMISTRY, Issue 7 2010Dezhi Shen Abstract A conjugate polymer poly[p -(phenyleneethylene)-alt-(phenyleneazophenyleneethylene)] (PPEPAPE) containing azobenzene building block in the polymer backbone was synthesized via Sonogashira cross-coupling of 4,4,-diiodoazobenzene and 1,4-diethynyl-2,5-didodecyloxybenzene. All the monomers and the resulting polymer were well characterized. The polymer had a relatively high molecular weight and showed very good solubility (,10 mg/mL) in common organic solvents. The photophysics of this polymer in solution and in film was investigated. The surface morphology of the films was studied by scanning electron microscope (SEM) and the relationship between the morphology and absorbance was discussed. This polymer has good film-forming property, broad absorbance and no emission, which might make it a good candidate for the photovoltaic material in the solar cell. [source] Conjugated Polymers: High-Resolution Scanning Near-Field Optical Lithography of Conjugated Polymers (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Mater. The fabrication of high-resolution nanostructures in both poly(p -phenylene vinylene), PPV, and a crosslinkable derivative of poly(9,9,-dioctylfluorene), F8, using scanning near-field optical lithography, is reported. The ability to draw complex, reproducible structures with 65000 pixels and lateral resolution below 60 nm (< ,/5) is demonstrated over areas up to 20 ,m × 20 ,m. Patterning on length-scales of this order is desirable for realizing applications both in organic nanoelectronics and nanophotonics. The technique is based on the site-selective insolubilization of a precursor polymer under exposure to the confined optical field present at the tip of an apertured near-field optical fiber probe. In the case of PPV, a leaving-group reaction is utilized to achieve insolubilization, whereas the polyfluorene is insolubilized using a photoacid initiator to create a crosslinked network in situ. For PPV, resolubilization of the features is observed at high exposure energies. This is not seen for the crosslinked F8 derivative, r-F8Ox, allowing us to pattern structures up to 200 nm in height. [source] High-Resolution Scanning Near-Field Optical Lithography of Conjugated PolymersADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Daniel Credgington The fabrication of high-resolution nanostructures in both poly(p -phenylene vinylene), PPV, and a crosslinkable derivative of poly(9,9,-dioctylfluorene), F8, using scanning near-field optical lithography, is reported. The ability to draw complex, reproducible structures with 65000 pixels and lateral resolution below 60 nm (< ,/5) is demonstrated over areas up to 20 ,m × 20 ,m. Patterning on length-scales of this order is desirable for realizing applications both in organic nanoelectronics and nanophotonics. The technique is based on the site-selective insolubilization of a precursor polymer under exposure to the confined optical field present at the tip of an apertured near-field optical fiber probe. In the case of PPV, a leaving-group reaction is utilized to achieve insolubilization, whereas the polyfluorene is insolubilized using a photoacid initiator to create a crosslinked network in situ. For PPV, resolubilization of the features is observed at high exposure energies. This is not seen for the crosslinked F8 derivative, r-F8Ox, allowing us to pattern structures up to 200 nm in height. [source] Conjugated Polymers: Enhanced Charge Transportation in Semiconducting Polymer/Insulating Polymer Composites: The Role of an Interpenetrating Bulk Interface (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Mater. By taking advantage of two-phase interface engineering in three dimensions, X. Yang and co-workers demonstrate on page 1714 the substantially improved (instead of decreased) electrical properties of conjugated polymer/insulating polymer composites. This novel approach paves the way for preparing high-performance semiconducting polymer composites with reduced cost, improved mechanical properties, and environmental stability. [source] Intrinsic Surface Dipoles Control the Energy Levels of Conjugated PolymersADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Georg Heimel Abstract Conjugated polymers are an important class of materials for organic electronics applications. There, the relative alignment of the electronic energy levels at ubiquitous organic/(in)organic interfaces is known to crucially impact device performance. On the prototypical example of poly(3-hexylthiophene) and a fluorinated derivative, the energies of the ionization and affinity levels of , -conjugated polymers are revealed to critically depend on the orientation of the polymer backbones with respect to such interfaces. Based on extensive first-principles calculations, an intuitive electrostatic model is developed that quantitatively traces these observations back to intrinsic intramolecular surface dipoles arising from the , -electron system and intramolecular polar bonds. The results shed new light on the working principles of organic electronic devices and suggest novel strategies for materials design. [source] Conjugated Polymers Combined with a Molecular Beacon for Label-Free and Self-Signal-Amplifying DNA MicroarraysADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Kangwon Lee Abstract A conjugated polymer (CP) and molecular-beacon-based solid-state DNA sensing system is developed to achieve sensitive, label-free detection. A novel conjugated poly(oxadiazole) derivative exhibiting amine and thiol functional groups (POX-SH) is developed for unique chemical and photochemical stability and convenient solid-state on-chip DNA synthesis. POX-SH is soluble in most nonpolar organic solvents and exhibits intense blue fluorescence. POX-SH is covalently immobilized onto a maleimido-functionalized glass slide by means of its thiol group. Molecular beacons having a fluorescent dye or quencher molecule as the fluorescence resonance energy transfer (FRET) acceptor are synthesized on the immobilized POX-SH layer through direct on-chip oligonucleotide synthesis using the amine side chain of POX-SH. Selective hybridization of the molecular beacon probes with the target DNA sequence opens up the molecular beacon probes and affects the FRET between POX-SH and the dye or quencher, producing a sensitive and label-free fluorescence sensory signal. Various molecular design parameters, such as the size of the stem and loop of the molecular beacon, the choice of dye, and the number of quencher molecules are systematically controlled, and their effects on the sensitivity and selectivity are investigated. [source] Electron-Rich Alcohol-Soluble Neutral Conjugated Polymers as Highly Efficient Electron-Injecting Materials for Polymer Light-Emitting DiodesADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Fei Huang Abstract We report the design and synthesis of three alcohol-soluble neutral conjugated polymers, poly[9,9-bis(2-(2-(2-diethanolaminoethoxy) ethoxy)ethyl)fluorene] (PF-OH), poly[9,9-bis(2-(2-(2-diethanol-aminoethoxy)ethoxy)ethyl)fluorene- alt -4,4,-phenylether] (PFPE-OH) and poly[9,9-bis(2-(2-(2-diethanolaminoethoxy) ethoxy)ethyl)fluorene- alt -benzothiadizole] (PFBT-OH) with different conjugation length and electron affinity as highly efficient electron injecting and transporting materials for polymer light-emitting diodes (PLEDs). The unique solubility of these polymers in polar solvents renders them as good candidates for multilayer solution processed PLEDs. Both the fluorescent and phosphorescent PLEDs based on these polymers as electron injecting/transporting layer (ETL) were fabricated. It is interesting to find that electron-deficient polymer (PFBT-OH) shows very poor electron-injecting ability compared to polymers with electron-rich main chain (PF-OH and PFPE-OH). This phenomenon is quite different from that obtained from conventional electron-injecting materials. Moreover, when these polymers were used in the phosphorescent PLEDs, the performance of the devices is highly dependent on the processing conditions of these polymers. The devices with ETL processed from water/methanol mixed solvent showed much better device performance than the devices processed with methanol as solvent. It was found that the erosion of the phosphorescent emission layer could be greatly suppressed by using water/methanol mixed solvent for processing the polymer ETL. The electronic properties of the ETL could also be influenced by the processing conditions. This offers a new avenue to improve the performance of phosphorescent PLEDs through manipulating the processing conditions of these conjugated polymer ETLs. [source] Bimolecular Crystals of Fullerenes in Conjugated Polymers and the Implications of Molecular Mixing for Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009A. C. Mayer The performance of polymer:fullerene bulk heterojunction solar cells is heavily influenced by the interpenetrating nanostructure formed by the two semiconductors because the size of the phases, the nature of the interface, and molecular packing affect exciton dissociation, recombination, and charge transport. Here, X-ray diffraction is used to demonstrate the formation of stable, well-ordered bimolecular crystals of fullerene intercalated between the side-chains of the semiconducting polymer poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2- b]thiophene. It is shown that fullerene intercalation is general and is likely to occur in blends with both amorphous and semicrystalline polymers when there is enough free volume between the side-chains to accommodate the fullerene molecule. These findings offer explanations for why luminescence is completely quenched in crystals much larger than exciton diffusion lengths, how the hole mobility of poly(2-methoxy-5-(3,,7,-dimethyloxy)-p-phylene vinylene) increases by over 2 orders of magnitude when blended with fullerene derivatives, and why large-scale phase separation occurs in some polymer:fullerene blend ratios while thermodynamically stable mixing on the molecular scale occurs for others. Furthermore, it is shown that intercalation of fullerenes between side chains mostly determines the optimum polymer:fullerene blending ratios. These discoveries suggest a method of intentionally designing bimolecular crystals and tuning their properties to create novel materials for photovoltaic and other applications. [source] Energy-Modulated Heterostructures Made with Conjugated Polymers for Directional Energy Transfer and Carrier Confinement,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007R. Favarim Abstract In this paper we demonstrate that multilayer structures with modulated bandgaps can be used for efficient energy transfer and carrier confinement inside a nanostructured film of a light-emitting polymer. The films were produced with the layer-by-layer technique (LbL) with a poly(p -phenylene vinylene) (PPV) precursor and a long chain dodecylbenzenesulfonate ion (DBS). DBS is incorporated selectively into the precursor chain, and with a rapid, low temperature conversion process (100,°C) superstructures with variable HOMO,LUMO gap could be formed along the deposition direction by changing the DBS concentration. Structures with different stair-type energy modulations were produced, which are thermally stable and reproducible, as demonstrated by UV-VIS. absorption measurements. Energy differences of up to 0.5,eV between the lowest and highest conjugated layers inside the stair structure could be achieved, which was sufficient to guide the excitation over long distances to the lower bandgap layer. [source] Ground-State Interaction and Electrical Doping of Fluorinated C60 in Conjugated PolymersADVANCED MATERIALS, Issue 44 2009Olga Solomeshch C60F36 is reported to be an efficient dopant for conjugated polymers. Its fluorine atoms induce a large shift in the energy levels with respect to C60. Its role as a dopant is studied by examining the charge transfer formed with the commonly used polymer, P3HT. [source] Radical Polymers for Organic Electronic Devices: A Radical Departure from Conjugated Polymers?ADVANCED MATERIALS, Issue 22 2009Kenichi Oyaizu Abstract Radical polymers are aliphatic or nonconjugated polymers bearing organic robust radicals as pendant groups per repeating unit. A large population of the radical redox sites allows the efficient redox gradient-driven electron transport through the polymer layer by outer-sphere self-exchange reactions in electrolyte solutions. The radical polymers are emerging as a new class of electroactive materials useful for various kinds of wet-type energy storage, transport, and conversion devices. Electric-field-driven charge transport by hopping between the densely populated radical sites is also a remarkable aspect of the radical polymers in the solid state, which leads to many dry-type devices such as organic memories, diodes, and switches. [source] Saturation, Relaxation, and Dissociation of Excited Triplet Excitons in Conjugated PolymersADVANCED MATERIALS, Issue 8 2009Xudong Yang Femtosecond pump-probe spectroscopy is used to measure the excited state absorption dynamics in triplet excitons generated by continuous wave excitation of a conjugated polymer. Saturation of the T1,Tn transition is observed, allowing a cross-section of 2.0,×,10,16,cm2 to be established. Relaxation to T1 occurs with a 300,fs timescale, but 20% of Tn states dissociate into charges. [source] Controlling Electrical Properties of Conjugated Polymers via a Solution-Based p-Type Doping,ADVANCED MATERIALS, Issue 17 2008Keng-Hoong Yim Tetrafluoro-tetracyano-quinodimethane (F4TCNQ) is used to p-dope conjugated polymers with a wide range of the HOMO levels via co-blending in a common organic solvent. Doping results in several orders of magnitude increase in the bulk conductivity and hole-current with reduced turn-on voltage. The effectiveness of doping increases as the HOMO level of the polymer becomes smaller. [source] Bilayer Approach to Laser-Induced Thermal Patterning of ,-Conjugated Polymers,ADVANCED MATERIALS, Issue 13 2008Terry J. Gordon Patterns of a fluorescent ,-conjugated polymer (,CP) are obtained by exposure of bilayer films of a NIR-absorbing dye spin cast onto a thermally labile ,CP. Feature sizes of 20 µm are obtained using laser scan speeds as high as 0.9 m s,1. [source] Cross-Linked Conjugated Polymers for Achieving Patterned Three-Color and Blue Polymer Light-Emitting Diodes with Multi-Layer StructuresMACROMOLECULAR RAPID COMMUNICATIONS, Issue 18 2009Xianyu Deng Abstract Reactions between the ethylene groups in the backbone of conjugated polymers under UV illumination and heat treatment result in the cross-linking of the main polymer chains. The cross-linking leads to two simultaneous results in the polymer: excellent solvent resistance and increased bandgap. Using this reaction, three-color polymer light-emitting diodes (PLEDs) with a multi-layer structure can be easily realized by a dry photo-pattern in an active-gas-free environment. Multi-layer blue devices with dramatically enhanced efficiency can also be achieved conveniently. [source] Triplet Excitation Scavenging in Films of Conjugated PolymersCHEMPHYSCHEM, Issue 7 2009Sarah Schols Abstract Nonvertical triplet energy transfer in solid conjugated polymer films is demonstrated for the first time using 1,3,5,7-cyclooctatetraene, a compound that can efficiently quench the phosphorescence of polyfluorene without affecting its fluorescence (see spectra). The results suggest that nonvertical triplet scavengers might be promising candidates for controlling the triplet concentration in fluorescent high-brightness organic devices. Phosphorescence and delayed fluorescence of polyfluorene polymer films doped with cyclooctatetraene (COT) and anthracene are studied by means of time-resolved photoluminescence (PL) measurements. The occurrence of an anomalous nonvertical triplet energy transfer in solid conjugated polymer films is demonstrated for the first time employing the "nonvertical" COT triplet acceptor, which appears to behave similarly to conventional vertical triplet acceptors, such as anthracene. Both dopant molecules are found to efficiently quench the host phosphorescence of the polymer without affecting the host fluorescence,this can be attributed to the large singlet,triplet (S1,T1) splitting of these molecules. This S1,T1 splitting is exceptionally large in COT due to its low-lying relaxed triplet state, which is capable of accepting host triplet excitations. In contrast to anthracene, the triplet lifetime of the COT molecules is reasonably short, thus making a fast deactivation of the triplet excitations possible. This suggests that nonvertical triplet scavengers might be promising candidates for quenching the host triplet excitations in future electrically pumped fluorescence organic lasers, which suffer from excessive triplet-state losses. [source] Intrinsic Surface Dipoles Control the Energy Levels of Conjugated PolymersADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Georg Heimel Abstract Conjugated polymers are an important class of materials for organic electronics applications. There, the relative alignment of the electronic energy levels at ubiquitous organic/(in)organic interfaces is known to crucially impact device performance. On the prototypical example of poly(3-hexylthiophene) and a fluorinated derivative, the energies of the ionization and affinity levels of , -conjugated polymers are revealed to critically depend on the orientation of the polymer backbones with respect to such interfaces. Based on extensive first-principles calculations, an intuitive electrostatic model is developed that quantitatively traces these observations back to intrinsic intramolecular surface dipoles arising from the , -electron system and intramolecular polar bonds. The results shed new light on the working principles of organic electronic devices and suggest novel strategies for materials design. [source] Coordination of nickel and copper dithiolate to 2,2,-bipyridine-based ,-conjugated polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2004Shin-ichiro Kato Abstract ,-Conjugated polymers (Poly1,Poly3) containing a 2,2,-bipyridine (bpy) unit were subjected to coordination to nickel and copper dithiolate for the purpose of manipulating the photophysical properties. The absorption maximum peak of Poly1 [maximum wavelength (,max) = 446 nm] redshifted by 36 nm upon the coordination of bpy to NiCl2, which produced Poly1,NiCl2. A further bathochromic shift was observed in the spectrum of Poly1,mntNi [mntNi = (maleonitrile dithiolate)nickel; ,max = 499 nm] bearing the dithiolate ligand, which stemmed from the extension of the conjugated system over the nickel dithiolate moiety through the bpy unit. An increase in the [Ni]/[bpy] ratio in Poly1,mntNi rendered the original maximum peak at 446 nm smaller and the lower energy charge-transfer peak at 499 nm larger; the isosbestic points remained at 380 and 475 nm. The green fluorescence (,max = 504 nm) emitted from Poly1 markedly diminished upon the coordination of nickel dithiolate because of the effective energy transfer. The absorption maximum peak of Poly1,mntNi in chloroform at 499 nm blueshifted to 471 nm when the volume ratio of the chloroform/N,N -dimethylformamide solvent reached 10:90. The coordination of nickel dithiolate to Poly2 and Poly3 also brought about redshifts of the absorption maximum peaks of as much as 55 and 61 nm, respectively. The absorption maximum peak of Poly1,(phenyldithiolate)nickel(pdtNi) (,max = 474 nm) redshifted by 28 nm in comparison with that of Poly1, whereas the magnitude of the shift of Poly1,bis(thiophenoxide)nickel(btpNi) bearing two thiophenoxide ligands was 20 nm. Poly1,mntCu with a tetrahedral copper center was also investigated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2631,2639, 2004 [source] Detection of volatile organic compounds using a polythiophene derivativePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2010V. C. Gonçalves Abstract Conjugated polymers have been subject of great interest in the recent literature from both fundamental point of view and applied science perspective. Among the several types of conjugated polymers used in recent investigations, polythiophene and its derivatives have attracted considerable attention over the past 20,years due to their high mobility and other remarkable solid-state properties. They have potential applications in many fields, such as microelectronic devices, catalysts, organic field-effect transistors, chemical sensors, and biosensors. They have been studied as gas and volatile organic compounds (VOCs) sensors using different principles or transduction techniques, such as optical absorption, conductivity, and capacitance measurements. In this work, we report on the fabrication of gas sensors based on a conducting polymer on an interdigitated gold electrode. We use as active layer of the sensor a polythiophene derivative: poly (3-hexylthiophene) (P3HT) and analyzed its conductivity as response for exposure to dynamic flow of saturated vapors of six VOCs [n -hexane, toluene, chloroform, dichloromethane, methanol, and tetrahydrofuran (THF)]. Different responses were obtained upon exposure to all VOCs, THF gave the higher response while methanol the lower response. The influence of moisture on the measurements was also evaluated. [source] Luminescence properties of poly- (phenylene vinylene) derivativesPOLYMER INTERNATIONAL, Issue 3 2008Cuong Ton-That Abstract BACKGROUND: Conjugated polymers, especially those of the poly(phenylene vinylene) (PPV) family, are promising candidates as emission material in light-emitting devices. The aim of this work was to investigate the dependence of the luminescence properties of PPV-based derivatives on their polymer structure, especially side groups. RESULTS: Three PPV derivatives, BEHPPV, MEHPPV and MEHSPPV, were synthesised and characterised by photoluminescence (PL) and cathodoluminescence (CL) spectroscopies in the temperature range 10,300 K. PL and CL spectra of the polymers exhibit similar luminescence peaks, which undergo a blue shift with increasing temperature. The shift in wavelength is accompanied by variations in the relative intensities of emission peaks. Both BEHPPV and MEHPPV display emission characteristics of the PPV backbone, but the peak of MEHPPV shifts to a longer wavelength in comparison with the corresponding peak of BEHPPV at the same temperature. The luminescence spectra of MEHSPPV, which has a sulfanyl incorporated in the side chain, are considerably different from those of the two other derivatives. CONCLUSIONS: The results demonstrate that the luminescence properties depend strongly on the chain conformations of the conjugated backbone, which are affected by polymer side chains. Copyright © 2007 Society of Chemical Industry [source] Conjugated polymers with tethered electron-accepting moieties as ambipolar materials for photovoltaicsPOLYMER INTERNATIONAL, Issue 8 2007Antonio Cravino Abstract Conjugated polymers are of increasing interest as semiconductors for soft (opto)electronic devices, including photovoltaic elements. A promising conversion of solar energy into electrical energy is possible with blends of soluble electron donor-type conjugated polymers and fullerenes as electron-acceptor, transporting component. This approach, called bulk-heterojunction, suggested the preparation of intrinsic ambipolar materials to control simultaneously the electronic and morphological properties. On these bases, the covalent grafting of acceptor moieties onto conjugated backbones seemed attractive for the preparation of intrinsically ambipolar polymeric materials (,double-cable' polymers) as an alternative to donor,acceptor composites. The design, characterisation and application of this novel class of polymers are reviewed taking into account the current understanding of organic photovoltaics. Copyright © 2007 Society of Chemical Industry [source] Cationic Polyelectrolyte Amplified Bead Array for DNA Detection with Zeptomole Sensitivity and Single Nucleotide Polymorphism SelectivityADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Chun Wang Abstract A highly sensitive strand specific DNA assay, which consists of a peptide nucleic acid (PNA) probe, a cationic conjugated polymer (PFVP), and self-assembled polystyrene beads in microwell arrays on silicon chip, is reported. PFVP, as an efficient signal amplifier and signal reporter, has been specially designed and synthesized to be compatible with commercial confocal microscopes for sensing on solid substrates. The assay operates on the net increase in negative charge at the PNA surface that occurs upon single-stranded DNA hybridization, which subsequently allows complex formation with the positively charged PFVP to favor energy transfer between the polymer and Cy5-labeled target. With maximized surface contact provided by bead arrays and signal amplification provided by PFVP, this assay allows detection of ,300 copies of Cy5-labeled DNA using a commercial confocal microscope. In addition, the same strategy is also extended for label-free DNA detection with a detection sensitivity of 150 attomole. Excellent discrimination against single nucleotide polymorphism (SNP) is also demonstrated for both Cy5-labeled and label-free target detection. This study indicates that cationic conjugated polymers have great potential to be incorporated into the widely used microarray technology for simplified process with improved detection sensitivity. [source] Conjugated Polymers Combined with a Molecular Beacon for Label-Free and Self-Signal-Amplifying DNA MicroarraysADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Kangwon Lee Abstract A conjugated polymer (CP) and molecular-beacon-based solid-state DNA sensing system is developed to achieve sensitive, label-free detection. A novel conjugated poly(oxadiazole) derivative exhibiting amine and thiol functional groups (POX-SH) is developed for unique chemical and photochemical stability and convenient solid-state on-chip DNA synthesis. POX-SH is soluble in most nonpolar organic solvents and exhibits intense blue fluorescence. POX-SH is covalently immobilized onto a maleimido-functionalized glass slide by means of its thiol group. Molecular beacons having a fluorescent dye or quencher molecule as the fluorescence resonance energy transfer (FRET) acceptor are synthesized on the immobilized POX-SH layer through direct on-chip oligonucleotide synthesis using the amine side chain of POX-SH. Selective hybridization of the molecular beacon probes with the target DNA sequence opens up the molecular beacon probes and affects the FRET between POX-SH and the dye or quencher, producing a sensitive and label-free fluorescence sensory signal. Various molecular design parameters, such as the size of the stem and loop of the molecular beacon, the choice of dye, and the number of quencher molecules are systematically controlled, and their effects on the sensitivity and selectivity are investigated. [source] | ||||||||||||||||||||||||||||