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Antifouling materials are indispensable in the biomedical field, but their high hydrophilicity and surface free energy provoke contamination on surfaces under atmospheric conditions, thus limiting their applicability in medical devices. This study proposes a new zwitterionic structure, 4-vinylpyridine carboxybetaine (4VPCB), that results in lower surface free energy and increases biological inertness. In the design of 4VPCB, one to three carbon atoms are inserted between the positive charge and negative charge (carbon space length, CSL) of the pyridyl-containing side chain to adjust hydration with water molecules. The pyridine in the 4VPCB structure provides the hydrophobicity of the zwitterionic functional group, and thus it can have a lower free energy in the gas phase but maintain higher hydrophilicity in the liquid phase environment. Surface plasmon resonance and confocal microscopy were used to analyze the antiprotein adsorption and anti-blood cell adhesion properties of the P4VPCB brush surface. The results showed that the CSL in the P4VPCB structure affected the biological inertness of the surface. The protein adsorption on the surface of P4VPCB2 (CSL= 2) is lower than that on the surfaces of P4VPCB1 (CSL = 1) and P4VPCB3 (CSL = 3), and the optimal resistance to protein adsorption can be reduced to 7.5 ng cm−2. The surface of P4VPCB2 can also exhibit excellent blood-inert function in the adhesion test with various human blood cells, offering a potential possibility for the future design of a new generation of blood-inert medical materials.

n-Doping of P(BTP-DPP) with the organometallic dimer (RuCp*mes)2, processed through sequential casting, is reported. Maximum conductivities of 0.45 S cm–1 were achieved that are relatively high for n-type semiconducting polymers. Electron paramagnetic resonance spectroscopy, ultraviolet visible spectroscopy, and ultraviolet photoemission spectroscopy are consistent with the introduction of high carrier concentrations by sequential processing, leading to bipolaronic, or otherwise spin-paired carriers. P(BTP-DPP) has glassy ordering in thin films, observed using wide angle X-ray scattering, that allows efficient incorporation of the dopant as a function of processing condition. The changes in electrical conductivity as a function of the dopant concentration are proposed to occur by charge percolation through domains with a mixture of polaronic and bipolaronic carriers.

The design, synthesis, and characterization of solution-processable polymers for organic light emitting diode (OLED) applications are presented. Theoretical calculations were employed to identify a carbazole-pyrimidine based building block as an optimized host material for the emissive layer of an idealized OLED stack. Efficient, free radical homopolymerization and copolymerization with a novel methacrylate-based heteroleptic iridium(III) complex leads to a library of nonconjugated polymers with pendant semiconductors. Optoelectronic characterization reveals impressive photoluminescence quantum yield (PLQY) values exceeding 80% and single-layer OLEDs show optimal performance for copolymers containing 6 mol % of iridium comonomer dopant.

We demonstrate controlled growth of vertical organic crystal nanowires on single layer graphene. Using Scanning Electron Microscopy (SEM), high-resolution transmission electron microscopy (TEM), and Grazing Incidence X-ray Diffraction (GIXD), we probe the microstructure and morphology of dibenzotetrathienocoronene (DBTTC) nanowires epitaxially grown on graphene. The investigation is performed at both the ensemble and single nanowire level, and as a function of growth parameters, providing insight of and control over the formation mechanism. The size, density and height of the nanowires can be tuned via growth conditions, opening new avenues for tailoring three-dimensional (3-D) nanostructured architectures for organic electronics with improved functional performance.

Glassy organic semiconductors provide a convenient host for dispersing guest molecules, such as dopants or light-emitting chromophores. However, many glass-forming compounds will crystallize overtime leading to changes in performance and stability in devices. Methods to stabilize amorphous molecular solids are therefore desirable. We demonstrate that solution-processable glasses can be formed from a mixture of 8,8’-biindeno[2,1-b]thiophenylene (BTP) atropisomers. While the trans isomer of methylated BTP, (E)-MeBTP crystallizes in spin-cast films, the addition of (Z)-MeBTP slows the growth of the spherulites. X-ray scattering and optical microscopy indicate that films containing 40% (Z)-MeBTP do not crystallize, even with the addition of nucleation agents and aging for several months.

"Ball and socket" motif: The contorted dibenzotetrathienocoronene (6-DBTTC) forms a complex with the C(70) fullerene PC(70) BM embedded in an amorphous phase of PC(70) BM. The materials are processable into organic solar cells in solution. The power conversion efficiency is maximal when there is a 1:2 molar ratio of 6-DBTTC to PC(70) BM. Formation of the supramolecular complex directly affects charge separation in the active layer.

We detail a general method for the synthesis of dibenzotetrathienocoronenes and elucidate their solid state structures in crystals and co-crystals. The contorted dibenzotetrathienocoronene (c-DBTTC) is a tetrathiophene-fused version of the previously studied contorted hexabenzocoronenes (c-HBC). The synthesis detailed here is simple and provides easy access to this important class of materials. We have found that these materials display molecular flexibility and tunable supramolecular self-assembly properties in the solid state by shifting molecular conformations between two different conformations. Depending on the conditions under which a c-DBTTC-containing material crystallizes, the c-DBTTC adopts either the “up-down” or the “butterfly” conformation. When grown from the vapor phase, crystals of the unsubstituted c-DBTTC show the molecule only in the up-down conformation, and it packs into dense crystals containing columnar arrays with close intracolumnar packing. The packing is controlled by the inherent molecular corrugation of the three-dimensional core and sulfur–sulfur interactions. When grown as co-crystals with electron acceptors from solution, the butyl-substituted c-DBTTC either adopts the butterfly conformation when the electron acceptor is small enough to be completely enveloped (TCNQ) or the up-down conformation when the electron acceptor is relatively large (C60). When grown from organic solvent crystals of the butyl-substituted c-DBTTC contain molecules of the solvent as the only guest, and we observe both conformations of the c-DBTTC. Controlling the supramolecular structure is the key to developing these materials for electronic applications.

Single-molecule measurements of biomolecules can provide information about the molecular interactions and kinetics that are hidden in ensemble measurements. However, there is a requirement for techniques with improved sensitivity and time resolution for use in exploring biomolecular systems with fast dynamics. Here, we report the detection of DNA hybridization at the single-molecule level using a carbon nanotube field-effect transistor. By covalently attaching a single-stranded probe DNA sequence to a point defect in a carbon nanotube, we are able to measure two-level fluctuations in the conductance of the nanotube in the presence of a complementary DNA target. The kinetics of the system are studied as a function of temperature, allowing the measurement of rate constants, melting curves and activation energies for different sequences and target concentrations. The kinetics demonstrate non-Arrhenius behaviour, in agreement with DNA hybridization experiments using fluorescence correlation spectroscopy. This technique is label-free and could be used to probe single-molecule dynamics at microsecond timescales.

This article describes the synthesis of a new type of bowl-shaped polycyclic aromatic hydrocarbon. These bowls are formed by joining the proximal carbons of contorted hexabenzocoronenes. These methods begin to tap a wealth of structural diversity available from these core structures. The bowl-shaped hydrocarbons more easily accept electrons than their contorted hexabenzocoronene precursors and associate strongly with C70.

Fluorinated, contorted hexabenzocoronenes (HBCs) have been synthesized in a facile manner via Suzuki-Miyaura coupling of fluorinated phenyl boronic acids followed by photocyclization and Scholl cyclization. In addition to the molecular conformation observed in previous HBC derivatives, close-contact fluorine-fluorine intramolecular interactions result in a metastable conformation not previously observed. Heating the metastable HBCs above 100 °C irreversibly converts them to the stable conformation, suggesting that the metastable conformation arises from a kinetically arrested state during cyclization.

An experimental correlation was established between pore size derived from N2 adsorption, DN2 , and capillary condensation/evaporation pressure, (P/P0)t,Kr, obtained from Kr adsorption/desorption isotherms on powdery siliceous MCM-41, MCM-48 and SBA-15 samples, and was analyzed by the DBdB theory. The correlation was then used to estimate the pore size distribution from the Kr adsorption isotherm of mesoporous silica layers on Si(1 0 0) wafer prepared using P123 and Brij � 56 surfactants. It was found by TEM analysis that the pore shape in the thin films was distorted from circular to ellipsoidal, leading to different pore sizes estimated from the adsorption and desorption branches of the Kr isotherm. � 2005 Elsevier Inc. All rights reserved.

The preparation and characterization of highly dispersed metal nanoparticles in mesoporous silica SBA-15 are reported. The functionalization with organosilane to generate a monolayer of charged groups on the pore surface facilitates uniform distribution of ion-exchanged metal precursors in the channels of SBA-15, which, upon reduction, results in highly dispersed metal nanoparticles supported in SBA-15. Under mild reduction conditions, the surface functionality remains and so allows further metal incorporation cycles to achieve higher metal loading. After reduction in hydrogen flow, disk-shaped Pt nanoparticles in Pt/SBA-15 and spherical Au nanoparticles in Au/SBA-15 have been characterized in the channels of SBA-15 by PXRD, XAS, and TEM. Secondary Pt incorporation in Au/SBA-15 produces coexisting small Pt nanoparticles with large Au nanoparticles in the host channels. This preparation method is capable of template synthesis of various metal nanostructures with controlled morphology and composition inside...

The controlled radical polymerization of a variety of acrylate monomers is reported using an Ir-catalyzed visible light mediated process leading to well-defined homo-, random, and block copolymers. The polymerizations could be efficiently activated and deactivated using light while maintaining a linear increase in molecular weight with conversion and first order kinetics. The robust nature of the fac-[Ir(ppy)3] catalyst allows carboxylic acids to be directly introduced at the chain ends through functional initiators or along the backbone of random copolymers (controlled process up to 50 mol % acrylic acid incorporation). In contrast to traditional ATRP procedures, low polydispersity block copolymers, poly(acrylate)-b-(acrylate), poly(methacrylate)-b-(acrylate), and poly(acrylate)-b-(methacrylate), could be prepared with no monomer sequence requirements. These results illustrate the increasing generality and utility of light mediated Ir-catalyzed polymerization as a platform for polymer synthesis. © 2014 American Chemical Society.

Here we report a novel twisted monomer based on a distorted CC double bond for low bandgap conjugated copolymers. This new building block provides several unique characteristics when compared to classical planar systems such as high solubility, electron accepting ability, and isomeric tunability. The resulting copolymers exhibit broad absorption spanning both visible and near-infrared regions leading to promising solar cell performance.

Point-functionalized carbon nanotube field-effect transistors can serve as highly sensitive detectors for biomolecules. With a probe molecule covalently bound to a defect in the nanotube sidewall, two-level random telegraph noise (RTN) in the conductance of the device is observed as a result of a charged target biomolecule binding and unbinding at the defect site. Charge in proximity to the defect modulates the potential (and transmission) of the conductance-limiting barrier created by the defect. In this Letter, we study how these single-molecule electronic sensors are affected by ionic screening. Both charge in proximity to the defect site and buffer concentration are found to affect RTN amplitude in a manner that follows from simple Debye length considerations. RTN amplitude is also dependent on the potential of the electrolyte gate as applied to the reference electrode; at high enough repulsive potentials, the target DNA is completely repelled and RTN is suppressed.

We have demonstrated that carbon-nanotube field-effect transistors act as highly sensitive single-molecule detectors when point functionalized. The hybridization kinetics of two complementary strands of DNA are associated with two-level fluctuations in the conductance of the nanotube to which the DNA is bound. We have studied the temperature dependence of the nanotube conductance and shown that the transport mechanism is consistent with Frenkel Poole emission, in which negatively charged DNA modulates a tunnel barrier at the point functionalized defect site. These transistors represent an important potential sensing platform for label-free single-molecule diagnostics.

An organic semiconductor device is formed by the self-assembly on a transparent electrode surface. The donor (see picture; dibenzotetrathienocoronene, yellow layer) deposits as supramolecular cables, and the acceptor (C60, orange) subsequently infiltrates this network. This network provides a donor–acceptor interface that is interwoven at the nanoscale. When incorporated into a solar cell, the active layer provides large increases in power conversion efficiencies.

We test the feasibility of using nanostructured electrodes in organic bulk heterojunction solar cells to improve their photovoltaic performance by enhancing their charge collection efficiency and thereby increasing the optimal active blend layer thickness. As a model system, small concentrations of single wall carbon nanotubes are added to blends of poly(3-hexylthiophene): [6,6]-phenyl-C61-butyric acid methyl ester in order to create networks of efficient hole conduction pathways in the device active layer without affecting the light absorption. The nanotube addition leads to a 22% increase in the optimal blend layer thickness from 90 nm to 110 nm, enhancing the short circuit current density and photovoltaic device efficiency by as much as ∼10%. The associated incident-photon-to-current conversion efficiency for the given thickness also increases by ∼10% uniformly across the device optical absorption spectrum, corroborating the enhanced charge carrier collection by nanostructured electrodes.