• Energy Research

We present the simple and controllable fabrication of ordered arrays of poly(3-hexylthiophene) (P3HT) solid nanowires and hollow nanotubes by infiltrating the molten polymer into AAO nanopores at temperatures promoting partial (260 C) and complete (280 C) wetting regimes, respectively. We show that such wetting regimes (and thus the formation of nanowires or nanotubes) are associated with a different internal structure in the P3HT melt. At 260 C, the P3HT organizes into a smectic mesophase. Thus, the translational motion of the P3HT molecule through the phase-separated structure would involve an enthalpic penalty, which prevents the molecular diffusion required for achieving the complete wetting regime. Consequently, the P3HT wets the nanopores in partial wetting regime, so that solid nanowires are formed. In contrast, the melt is structurally isotropic at 280 C, which promotes the complete wetting regime, yielding nanotubes. Such a smectic mesophase is also present in P3HT confined into 350 nm in diameter pores. Furthermore, we observe the formation of a new type of nanostructure consisting of twinned nanotubes (two pores formed from one original pore) as a consequence of the appearance of a longitudinal meniscus which divided the hollow interior of the initial nanotube into two independent compartments. Lastly, we use the capillary rise of the P3HT melt along the cylindrical nanopores as a >coarse> nanoscale viscosimetry experiment for the measurement of its viscosity value under confinement. The physical behavior observed for P3HT might be extrapolated to other semiconducting polymers with similar comblike molecular architectures with applications in optoelectronics, thermoelectrics, and photovoltaics (like other poly(alkylthiophenes), polycarbazoles, polyfluorenes, polyphenylenes, etc.). © 2013 American Chemical Society. ERC 2008 Starting Grant “NanoTEC” number 240497. Spanish Ministry Economy and Competitiveness (Project MAT2008-03232 and MAT2011-23455). Peer Reviewed

We present the simple and controllable fabrication of ordered arrays of poly(3-hexylthiophene) (P3HT) solid nanowires and hollow nanotubes by infiltrating the molten polymer into AAO nanopores at temperatures promoting partial (260 C) and complete (280 C) wetting regimes, respectively. We show that such wetting regimes (and thus the formation of nanowires or nanotubes) are associated with a different internal structure in the P3HT melt. At 260 C, the P3HT organizes into a smectic mesophase. Thus, the translational motion of the P3HT molecule through the phase-separated structure would involve an enthalpic penalty, which prevents the molecular diffusion required for achieving the complete wetting regime. Consequently, the P3HT wets the nanopores in partial wetting regime, so that solid nanowires are formed. In contrast, the melt is structurally isotropic at 280 C, which promotes the complete wetting regime, yielding nanotubes. Such a smectic mesophase is also present in P3HT confined into 350 nm in diameter pores. Furthermore, we observe the formation of a new type of nanostructure consisting of twinned nanotubes (two pores formed from one original pore) as a consequence of the appearance of a longitudinal meniscus which divided the hollow interior of the initial nanotube into two independent compartments. Lastly, we use the capillary rise of the P3HT melt along the cylindrical nanopores as a >coarse> nanoscale viscosimetry experiment for the measurement of its viscosity value under confinement. The physical behavior observed for P3HT might be extrapolated to other semiconducting polymers with similar comblike molecular architectures with applications in optoelectronics, thermoelectrics, and photovoltaics (like other poly(alkylthiophenes), polycarbazoles, polyfluorenes, polyphenylenes, etc.). © 2013 American Chemical Society. ERC 2008 Starting Grant “NanoTEC” number 240497. Spanish Ministry Economy and Competitiveness (Project MAT2008-03232 and MAT2011-23455). Peer Reviewed

Three-dimensional (3D) nanostructures combine properties of nanoscale materials with the advantages of being macro-sized pieces when the time comes to manipulate, measure their properties or make a device. However, the amount of compounds with the ability to self-organize in ordered 3D nanostructures is limited. Therefore, template-based fabrication strategies become the key approach towards 3D nanostructures. Here we report the simple fabrication of a template based on anodic aluminium oxide, having a well-defined, ordered, tunable, homogeneous 3D nanotubular network in the sub 100-nm range. The 3D templates are then employed to achieve 3D, ordered nanowire networks in Bi2Te3 and polystyrene. Finally, we demonstrate the photonic crystal behaviour of both the template and the polystyrene 3D nanostructure. Our approach may establish the foundations for future high-throughput, cheap, photonic materials and devices made of simple commodity plastics, metals and semiconductors.

Three-dimensional (3D) nanostructures combine properties of nanoscale materials with the advantages of being macro-sized pieces when the time comes to manipulate, measure their properties or make a device. However, the amount of compounds with the ability to self-organize in ordered 3D nanostructures is limited. Therefore, template-based fabrication strategies become the key approach towards 3D nanostructures. Here we report the simple fabrication of a template based on anodic aluminium oxide, having a well-defined, ordered, tunable, homogeneous 3D nanotubular network in the sub 100-nm range. The 3D templates are then employed to achieve 3D, ordered nanowire networks in Bi2Te3 and polystyrene. Finally, we demonstrate the photonic crystal behaviour of both the template and the polystyrene 3D nanostructure. Our approach may establish the foundations for future high-throughput, cheap, photonic materials and devices made of simple commodity plastics, metals and semiconductors.

Emergent bioelectronic technologies are underpinned by the organic electrochemical transistor (OECT), which employs an electrolyte medium to modulate the conductivity of its organic semiconductor channel. Here we utilize postpolymerization modification (PPM) on a conjugated polymer backbone to directly introduce glycolated or anionic side chains via fluoride displacement. The resulting polymers demonstrated increased volumetric capacitances, with subdued swelling, compared to their parent polymer in p-type enhancement mode OECTs. This increase in capacitance was attributed to their modified side chain configurations enabling cationic charge compensation for thin film electrochemical oxidation, as deduced from electrochemical quartz crystal microbalance measurements. An overall improvement in OECT performance was recorded for the hybrid glycol/ionic polymer compared to the parent, owing to its low swelling and bimodal crystalline orientation as imaged by grazing-incidence wide-angle X-ray scattering, enabling its high charge mobility at 1.02 cm2·V-1·s-1. Compromised device performance was recorded for the fully glycolated derivative compared to the parent, which was linked to its limited face-on stacking, which hindered OECT charge mobility at 0.26 cm2·V-1·s-1, despite its high capacitance. These results highlight the effectiveness of anionic side chain attachment by PPM as a means of increasing the volumetric capacitance of p-type conjugated polymers for OECTs, while retaining solid-state macromolecular properties that facilitate hole transport.

Emergent bioelectronic technologies are underpinned by the organic electrochemical transistor (OECT), which employs an electrolyte medium to modulate the conductivity of its organic semiconductor channel. Here we utilize postpolymerization modification (PPM) on a conjugated polymer backbone to directly introduce glycolated or anionic side chains via fluoride displacement. The resulting polymers demonstrated increased volumetric capacitances, with subdued swelling, compared to their parent polymer in p-type enhancement mode OECTs. This increase in capacitance was attributed to their modified side chain configurations enabling cationic charge compensation for thin film electrochemical oxidation, as deduced from electrochemical quartz crystal microbalance measurements. An overall improvement in OECT performance was recorded for the hybrid glycol/ionic polymer compared to the parent, owing to its low swelling and bimodal crystalline orientation as imaged by grazing-incidence wide-angle X-ray scattering, enabling its high charge mobility at 1.02 cm2·V-1·s-1. Compromised device performance was recorded for the fully glycolated derivative compared to the parent, which was linked to its limited face-on stacking, which hindered OECT charge mobility at 0.26 cm2·V-1·s-1, despite its high capacitance. These results highlight the effectiveness of anionic side chain attachment by PPM as a means of increasing the volumetric capacitance of p-type conjugated polymers for OECTs, while retaining solid-state macromolecular properties that facilitate hole transport.