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The power density of redox flow batteries (RFBs) utilized on iron‐containing electrolytes is improved by incorporating iron particle redox mediators into the electrodes. Nonpurified carbon nanotube (CNT) electrodes containing iron nanoparticles, formed during the synthesis of CNTs using the ferrocene−xylene process, are activated to create “hotspots” for faradaic energy storage that reduces losses associated with kinetical, ohmic, and mass transfer resistances. CNT electrodes are activated through cyclic voltammetry to initiate charge transfer interactions between redox electrolytes and iron nanoparticles in the electrode. RFBs with modified electrodes experience a 140% increase in power density and a 57% increase in energy density in coin‐cell configurations. Economic value and ready availability of iron paired with enhanced performance make iron RFBs a viable option for future RFB research. Herein, the highest peak power density yet reported for an iron‐based RFB at 180 mW cm−2 with iron‐modified electrodes under no electrolyte flow is demonstrated.

A thermally responsive copolymer is designed to modulate the properties of an electrolyte solution. The copolymer is prepared using pNIPAM, which governs the thermal properties, and acrylic acid, which provides the electrolyte ions. As the polymer undergoes a thermally activated phase transition, the local environment around the acid groups is reversibly switched, decreasing ion concentration and conductivity. The responsive electrolyte is used to control the activity of redox electrodes with temperature.

Organic electronic materials have been the focus of intense research for more than twenty years. In addition to their oft-cited potential advantages of low-cost, compatibility with plastic substrates, and ease of processing, much of their appeal lies in the promise of functionality and performance by design. Ideally, electronic materials for applications ranging from flexible circuits and displays to radio frequency identification (RFID) tags, light-emitting diodes (LEDs), and chemical sensors will be synthesized on demand from a toolbox of organic components. While the field has yet to realize such lofty goals, the development of a library of organic electronic materials and new experimental techniques have offered structure–property relationships that will serve as the foundation for the development of the a priori prediction of optoelectronic properties. The highest performance organic semiconductors have the common feature of a delocalized, aromatic, electronically active core. Fused acenes, thiophenes, and oligothiophenes are prototypical systems that are comprised of only this component, and have demonstrated benchmark performance. Because the molecular subunits are relatively non-polar, however, intermolecular interactions are rather weak. The electronic homogeneity of the units results in crystal structures bound loosely by van der Waals forces that are only weakly favored thermodynamically. Experimentally, this is observed in the form of polymorphism and crystal disorder, as has been observed for linear acenes, as well as a plethora of oligothiophenes, even for some cases of substitutions designed to impart order (see reference [6] within Azumi et al.). The result of this phenomenon is a solid-state order and organization that is both difficult to predict and control. One approach to predictably imparting order involves functionalizing an aromatic core with bulky pendant groups, which strongly direct supramolecular organization through steric repulsion. While this provides for a wide variety of crystal packing motifs and often improves performance through increased order, it often has the side effect of spacing molecules more disparately or at disadvantageous orientations, which may actually impair transport. In particular, while functionalization at the center of the electronically active core very uniquely specifies a packing motif based on the relative sizes of bulky groups and aromatic moieties, it often has the effect of limiting longitudinal alignment of the cores. Here, we study the family of a-substituted oligothiophene derivatives shown in Figure 1 (see Supporting information, SI, for synthesis details) in order to determine the effects of terminal substituent density on the packing of the electronically active core units. The molecules consist of an aromatic oligothiophene core, functionalized at the terminal positions with trimethylsilane (TMS) groups. In addition to imparting solubility, the substituent TMS groups yield layer-by-layer ordering of the aromatic cores. By isolating the functionalization to the terminal positions, the TMS groups are isolated to between the bc-planes that dominate charge transport. Furthermore, this motif allows us to study specifically the steric effects of the TMS groups on the in-plane packing of the aromatic core. Our previous thin-film structure studies showed that end substitution on the aromatic molecule with less bulky linear alkyl chains did not change the molecular packing motif. To examine the effect of the terminal TMS substitutions on the molecular packing, single crystals were grown using the Physical Vapor Transport technique and characterized by X-Ray diffraction (see SI for details). All of the compounds in Figure 1 formed thin, nearly two-dimensional platelet crystals, ideal for single crystal transistor device fabrication. The TMS-substituted compounds were especially stable, leaving behind no starting material, even if melted prior to crystal growth. The structures of the single crystals of quaterthiophene (4T) and TMS-substituted C O M M U N IC A TI O N www.advmat.de

Organic field-effect transistors (OFETs) are attractive for microelectronic applications such as sensor arrays or flexible displays, due to their adequate performance and relatively low production costs. Organic single-crystal transistors have emerged as benchmark devices for studying the intrinsic charge-transport properties in organic semiconductor materials. Conventional approaches for growing organic single crystals result in uncontrollable dimensions and the formation of extremely fragile crystals. In addition, the hand-selection and placement of individual crystals on a device structure represents a severe limitation for producing arrays of single-crystal transistors with high density and reasonable throughput. As a result, the application of organic single-crystal transistors has been restricted to fundamental charge transport studies, with their commercial application not yet realizable. We recently reported a materials-general method of fabricating large-area arrays of patterned organic single crystals. Microcontact-printed octadecyltriethoxysilane (OTS) film domains on smooth, inert substrates were found to act as preferential nucleation sites for single crystals for a broad range of organic semiconductor materials, such as pentacene, tetracene, rubrene and C60. In order to understand the underlying mechanism of preferential nucleation, the stamped OTS domains and the contact plane between the OTS domains and the organic crystals were inspected by atomic force microscopy (AFM) and optical microscopy. Our analysis suggests that crystals nucleate at the base of tall OTS pillars that form the significantly rough surface in the stamped domains. The selective nucleation inside the rough surface regions is discussed by means of a rate-equation model of the growth process.

Measuring the anisotropy of the field-effect mobility provides insight into the correlation between molecular packing and charge transport in organic semiconductor materials. Single-crystal field-effect transistors are ideal tools to study intrinsic charge transport because of their high crystalline order and chemical purity. The anisotropy of the field effect mobility in organic single crystals has previously been studied by lamination of macroscopically large single crystals onto device substrates. Here, a technique is presented that allows probing of the mobility anisotropy even though only small crystals are available. Crystals of a soluble oligothiophene derivative are grown in bromobenzene and drop-cast onto substrates containing arrays of bottom-contact gold electrodes. Mobility anisotropy curves are recorded by measuring numerous single crystal transistor devices. Surprisingly, two mobility maxima occur at azimuths corresponding to both axes of the rectangular cyclohexyl-substituted quaterthiophene (CH4T) in-plane unit cell, in contrast to the expected tensorial behavior of the field effect mobility.

Epitopes defined by monoclonal antibodies (mAb) specific for the Bordetella pertussis outer membrane protein P.69 (pertactin) were mapped using a series of amino- and carboxy-terminal deletion mutants expressed in Escherichia coli. mAb were found to bind predominantly to a region of pertactin spanning a (Pro-Gln-Pro)5 repeat motif and one mAb was found to bind to another region spanning a (Gly-Gly-Xaa-Xaa-Pro)5 repeat motif. To localize further the mAb-binding sites, a panel of synthetic peptides, a series of 94 overlapping hexameric peptides, and a P.69 30-amino acid fusion to a hepatitis B core protein (HBcAg-69), were synthesized. This combined approach has identified the binding site for the mAb BBO5: Pro-Gly-Pro-Gln-Pro-Pro; mAb BBO7, E4A8 and E4D7: Ala-Pro-Gln-Pro-Pro-Ala-Gly-Arg; and mAb BPE3: Thr-Leu-Trp-Tyr-Ala-Glu-Ser-Asn-Ala-Leu-Ser-Lys-Arg. We have used a non-lethal murine respiratory model of B. pertussis infection to investigate the ability of a peptide containing the epitope of the mAb BBO5 to elicit protective immunity. Immunization of mice with the HBcAg-69 protein prevented growth of B. pertussis in the lungs compared to mice receiving HBcAg alone, and protection correlated with high titers of anti-P.69 antibodies.

The inability for controlled large-scale assembly of single-walled carbon nanotubes (SWNTs) represents the biggest obstacle for application of this superior nanoelectronic material. Our aim here is to develop not only a reliable approach to deposit SWNTs uniformly over a large area from solution, but also leads to a SWNT network with tunable reproducible topological and electronic properties. By controlling nanotube network characteristics with substrate surface chemistry, we demonstrate reproducible transistors over large scales from solution, which is key for integration onto disposable and flexible plastic surfaces.