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Imidazolium ionic side-group-containing fluorene-based conjugated polyelectrolytes (CPEs) with different π-conjugated structures, poly[(9,9-bis(8'-(3″-methyl-1″-imidazolium)octyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] dibromide (F8im-Br) and poly[(9,9-bis(8'-(3″-methyl-1″-imidazolium)octyl)-2,7-fluorene)-alt-(benzo(2,1,3)thiadiazol-4,8-diyl) dibromide (F8imBT-Br), are synthesized and utilized as an electron injection layer (EIL) in green-emitting F8BT polymer light-emitting diodes (PLEDs). Both CPE EIL devices significantly outperform Ca cathode devices; 17.9 cd A(-1) (at 3.8 V) and 16.6 lm W(-1) (at 3.0 V) for F8imBT-Br devices, 11.1 cd A(-1) (at 4.2 V) and 9.1 lm W(-1) (at 3.4 V) for F8im-Br devices, and 7.2 cd A(-1) (at 3.6 V) and 7.0 lm W(-1) (at 3.0 V) for Ca devices. Importantly, unlike the F8im-Br EIL devices, F8imBT-Br PLEDs exhibit much faster electroluminescence turn-on times (<10 μs) despite both EILs possessing the same tethered imidazolium and mobile bromide ions. The F8imBT-Br devices represent, to the best of our knowledge, the highest efficiency in thin (70 nm) single-layer F8BT PLEDs in conventional device architecture with the fastest EL response time using CPE EIL with mobile ions. Our results clearly indicate the importance of an additional factor of EIL materials, specifically the conjugated backbone structure, to determine the device efficiency and response times.

Water-soluble cationic alkynylplatinum(II) 2,6-bis(benzimidazol-2'-yl)pyridine (bzimpy) complexes have been demonstrated to undergo supramolecular assembly with anionic polyelectrolytes in aqueous buffer solution. Metal-metal-to-ligand charge transfer (MMLCT) absorptions and triplet MMLCT ((3) MMLCT) emissions have been found in UV/Vis absorption and emission spectra of the electrostatic assembly of the complexes with non-conjugated polyelectrolytes, driven by Pt⋅⋅⋅Pt and π-π interactions among the complex molecules. Interestingly, the two-component ensemble formed by [Pt(bzimpy-Et){CCC6 H4 (CH2 NMe3 -4)}]Cl2 (1) with para-linked conjugated polyelectrolyte (CPE), PPE-SO3 (-) , shows significantly different photophysical properties from that of the ensemble formed by 1 with meta-linked CPE, mPPE-Ala. The helical conformation of mPPE-Ala allows the formation of strong mPPE-Ala-1 aggregates with Pt⋅⋅⋅Pt, electrostatic, and π-π interactions, as revealed by the large Stern-Volmer constant at low concentrations of 1. Together with the reasonably large Förster radius, large HOMO-LUMO gap and high triplet state energy of mPPE-Ala to minimize both photo-induced charge transfer (PCT) and Dexter triplet energy back-transfer (TEBT) quenching of the emission of 1, efficient Förster resonance energy transfer (FRET) from mPPE-Ala to aggregated 1 molecules and strong (3) MMLCT emission have been found, while the less strong PPE-SO3 (-) -1 aggregates and probably more efficient PCT and Dexter TEBT quenching would account for the lack of (3) MMLCT emission in the PPE-SO3 (-) -1 ensemble., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An optical nanoruler system based on a conjugated polyelectrolyte-silver nanoprism pair is developed for label-free protein detection by taking advantage of the metal-enhanced fluorescence effect of silver nanostructures. Antibody-antigen interactions induce a change in the metal-fluorophore distance, followed by the response of a fluorescent signal of the conjugated polyelectrolyte. The system is used to detect target antigens sensitively and selectively., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two novel liquid-crystal-conjugated polyelectrolytes (LCCPEs) poly[9,9-bis[6-(4-cyanobiphenyloxy)-hexyl]-fluorene-alt-9,9-bis(6-(N,N-diethylamino)-hexyl)-fluorene] (PF6Ncbp) and poly[9,9-bis[6-(4-cyanobiphenyloxy)-hexyl]-fluorene-alt-9,9-bis(6-(N-methylimidazole)-hexyl]-fluorene] (PF6lmicbp) are obtained by covalent linkage of the cyanobiphenyl mesogen polar groups onto conjugated polyelectrolytes. After deposition a layer of LCCPEs on ZnO interlayer, the spontaneous orientation of liquid-crystal groups can induce a rearrangement of dipole moments at the interface, subsequently leading to the better energy-level alignment. Moreover, LCCPEs favors intimate interfacial contact between ZnO and the photon harvesting layer and induce active layer to form the nanofibers morphology for the enhancement of charge extraction, transportation and collection. The water/alcohol solubility of the LCCPEs also enables them to be environment-accepted solvent processability. On the basis of these advantages, the poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C60-butyric acid methyl ester (PC60BM)-based inverted polymer solar cells (PSCs) combined with ZnO/PF6Ncbp and ZnO/PF6lmicbp bilayers boost the power conversion efficiency (PCE) to 3.9% and 4.2%, respectively. Incorporation of the ZnO/PF6lmicbp into the devices based on a blend of a narrow band gap polymer thieno[3,4-b]thiophene/benzodithiophene (PTB7) with [6,6]-phenyl C70-butyric acid methyl ester (PC71BM) affords a notable efficiency of 7.6%.

Two sets of conjugated polyelectrolytes with different molecular weights (Mn) in each set were synthesized. All polymers feature the same conjugated backbone with alternating (1,4-phenylene) and (2,5-thienylene ethynylene) repeating units, but different linkages between the backbone and side chains, namely, oxy-methylene (-O-CH2-) (P1-O-n, where n = 7, 9, and 14) and methylene (-CH2-) (P2-C-n, n = 7, 12, and 18). They all bear carboxylic acid moieties as side chains, which bind strongly to titanium dioxide (TiO2) nanoparticles. The two sets of polymers were used as light-harvesting materials in dye-sensitized solar cells. Despite the difference in molecular weight, polymers within each set have very similar light absorption properties. Interestingly, under the same working conditions, the overall cell efficiency of the P1-O-n series increases with a decreasing molecular weight while the efficiency of the P2-C-n series remains constant regardless of the molecular weight. Steady state photophysical measurements and dynamic light scattering investigation prove that P1-O-n polymers aggregate in solution while P2-C-n series are in the monomeric state. In P1-O-n series, a higher-molecular weight polymer results in a larger aggregate, which reduces the amount of polymers that are adsorbed onto TiO2 films and overall cell efficiency.

An easy and efficient approach to achieve a large-area cathode interlayer with controlled film composition, uniformity, and thickness under a nanometer scale is reported by using an electrostatic layer-by-layer (eLbL) self-assembly process. The eLbL films provide a new means for preparing efficient interlayers for polymer solar cells (PSCs) and also represent a potential candidate for use in high-performance large-area PSC modules in the future., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This research investigates the modification and dispersion and of pristine multiwalled carbon nanotubes (MWCNTs) through a simple solution mixing technique based on noncovalent interactions between poly(phenylene ethynylene)-based conjugated polyelectrolytes functionalized with cationic imidazolium solubilizing groups (PIM-2 and PIM-4) and MWCNTs. Spectroscopic studies demonstrated the ability of PIMs to strongly interact with and efficiently disperse MWCNTs in different solvents, mainly due to π interactions between the PIMs and the MWCNTs. Transmission electron microscopy and atomic force microscopy revealed the coating of the polyelectrolytes on the walls of the nanotubes. Scanning electron microscopy (SEM) studies confirm the homogeneous dispersion of PIM-modified MWCNTs in the poly(methyl methacrylate) (PMMA) matrix. The addition of 1 wt % PIM-modified MWCNTs to the matrix has led to a significant decrease in DC resistivity of the composite (13 orders of magnitude). The increase in electrical conductivity and the improvement in the thermal and mechanical properties of the membranes containing the PIM-modified MWCNTs is ascribed to the formation of MWCNT networks and cross-linking sites that provided channels for the electrons to move in throughout the matrix and reinforced the interface between MWCNTs and PMMA.

Array-based sensing offers several advantages for detecting a series of analytes with common structures or properties. In this study, four anionic conjugated polyelectrolytes (CPEs) with a common poly(p-pheynylene ethynylene) (PPE) backbone and varying pendant ionic side chains were designed. The conjugation length, repeat unit pattern, and ionic side chain composition were the main factors affecting the fluorescence patterns of CPE polymers in response to the addition of different metal ions. Eight metal ions, including Pb(2+), Hg(2+), Fe(3+), Cr(3+), Cu(2+), Mn(2+), Ni(2+), and Co(2+), categorized as water contaminants by the Environmental Protection Agency, were selected as analytes in this study. Fluorescence intensity response patterns of the four-PPE sensor array toward each of the metal ions were recorded, analyzed, and transformed into canonical scores using linear discrimination analysis (LDA), which permitted clear differentiation between metal ions using both two-dimensional and three-dimensional graphs. In particular, the array could readily differentiate between eight toxic metal ions in separate aqueous solutions at 100 nM. Our four-PPE sensor array also provides a practical application to quantify Pb(2+) and Hg(2+) concentrations in blind samples within a specific concentration range.

Rational materials design and interface engineering are both essential to realize a high performance for tandem cells. Two identical bulk heterojunctions are connected in series using novel interconnection layers combining pH-neutral conjugated polyelectrolytes and a thin film of ZnO nanoparticles by a solution process. The best performing tandem cells achieve a power conversion efficiency of 11.3%, with 25% enhancement in efficiency compared with single cells, which arises primarily from the increased light absorption., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An organic electrochemical transistor operates in accumulation mode with high transconductance. The channel comprises a thiophene-based conjugated polyelectrolyte, which is p-type doped by anions injected from a liquid electrolyte upon the application of a gate voltage. The use of ethylene glycol as a co-solvent dramatically improves the transconductance and the temporal response of the transistors., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two narrow-bandgap conjugated polyelectrolytes (CPEs) of identical backbone structure but different pendant charges are used to disperse single-walled carbon nanotubes (SWNTs) in MeOH. Films of the resulting CPE:SWNT composites have electrical conductivity dependent on the SWNT loading, which can be increased with acid vapor treatment. The anionic CPE gives higher electrical conductivity for the composite immediately after deposition, whereas a more-significant increase is observed for the cationic counterpart after acid treatment., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nanomaterials that combine diagnostic and therapeutic functions within a single nanoplatform are highly desirable for molecular medicine. Herein we report a novel theranostic platform based on a conjugated-polyelectrolyte (CPE) polyprodrug that contains functionality for image, chemo- and photodynamic therapy (PDT), and on-demand drug release upon irradiation with a single light source. Specifically, the PEGylated CPE serves as a photosensitizer and a carrier, and is covalently conjugated to doxorubicin through a linker that can be cleaved by reactive oxygen species (ROS). Under appropriate light irradiation, the CPE can generate ROS, not only for PDT, but also for on-demand drug release and chemotherapy. This nanoplatform will offer on-demand PDT and chemotherapy with drug release triggered by one light switch, which has great potential in cancer treatment., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

PCPDTBTSO3 K, an anionic, narrow-band-gap conjugated polyelectrolyte, was found to be doped after dialysis. The proposed doping mechanism involves protonation of the polymer backbone, followed by electron transfer from a neutral chain, to generate radical cations, which are stabilized by the pendant sulfonate anions. Formation of polarons is supported by spectroscopy and electrical-conductivity measurements., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This study concentrates on the potential application of conjugated polyelectrolytes (CPEs) to cell imaging and DNA delivery. Four different types of polyfluorene copolymers, namely, PAHFP-Br, PAEFP-Br, PAHFbT-Br, and PSBFP-Na, which have the same π-conjugated backbone but different side chains, were synthesized. For cytotoxicity testing, L-929 fibroblastic cells were treated with increasing concentrations (0-50 µM) of each CPE and then cell viability was determined by WST-8 assay. Cellular uptake of CPEs into cultured L-929 cells was observed by fluorescence microscopy. To examine DNA delivery by CPEs, the cells were incubated for 1 H with PAHFP-Br/fluorescein (Fl)-labeled single-stranded DNA (ssDNA-Fl) complex and then visualized by fluorescence microscopy. Cytotoxicity of CPEs was increased in a dose-dependent manner but at lower than 10 µM, PAHFP-Br, PAEFP-Br, and PSBFP-Na did not show any cytotoxic effects on the cells. When added to cell cultures at 1 µM, PAHFP-Br/ssDNA-Fl complex was delivered and then dissociated into PAHFP-Br and ssDNA-Fl within the cells. This result implies that PAHFP-Br can enable cell imaging and DNA delivery into fibroblastic cells. Therefore, it is suggested that PAHFP-Br with various advantages such as low cytotoxicity and high fluorescence efficiency can be extensively used as a potential agent for cell imaging and gene delivery., (© 2013 International Union of Biochemistry and Molecular Biology, Inc.)

A hybrid complex composed of an anionic conjugated polyelectrolyte (PFB-SO3Na) and a cationic phosphorescent Ir(III) oligomer is formed through electrostatic interaction by simple physical mixing in aqueous media. Due to their opposite charges and their effective spectral overlap, fluorescence resonance energy transfer occurs from the blue-emissive PFB-SO3Na to the red-emissive phosphorescent Ir(III) complex, which allows ratiometric and colorimetric Hg(2+) sensing in aqueous solution with good selectivity, sensitivity, as well as visible detection. Time-resolved photoluminescence is applied for Hg(2+) detection, which can effectively eliminate the background interference and improve the sensing sensitivity and signal-to-noise ratio in complicated media., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Understanding the cellular entry pathways of synthetic biomaterials is highly important to improve overall labeling and delivery efficiency. Herein, cellular entry mechanisms of conjugated polymer nanoparticles (CPNs) are presented. CPNs are intrinsic fluorescent materials used for various biological applications. While CPNs cause no toxicity, decreased CPN uptake is observed from cancer cells pretreated with genistein, which is an inhibitor of caveolae-mediated endocytosis (CvME). CvME is further confirmed by high co-localization with caveolin-1 proteins found in the caveolae and caveosomes. Excellent photophysical properties, non-toxicity, and non-destructive delivery pathways support that CPNs are promising multifunctional carriers minimizing degradation of contents during delivery., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Herein is reported the synthesis of gadolinium ion (Gd(III))-chelated hyperbranched conjugated polyelectrolyte (HCPE-Gd) and its application in fluorescence and magnetic resonance (MR) dual imaging in live animals. The synthesized HCPE-Gd forms nanospheres with an average diameter of ∼42 nm measured by laser light scattering and a quantum yield of 10% in aqueous solution. The absorption spectrum of HCPE-Gd has two maxima at 318 and 417 nm, and its photoluminescence maximum centers at 591 nm. Confocal laser scanning microscopy studies indicate that the HCPE-Gd is internalized in MCF-7 cancer cell cytoplasm with good photostability and low cytotoxicity. Further fluorescence and MR imaging studies on hepatoma H22 tumor-bearing mouse model reveal that HCPE-Gd can serve as an efficient optical/MR dual-modal imaging nanoprobe for in vivo cancer diagnosis., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)