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Percutaneous coronary intervention (PCI) is still burdened by a substantial number of complications despite constant technological advances, including the advent of intracoronary imaging (ICI) techniques. ICI modalities have been instrumental for the understanding the mechanism of PCI failure. Thanks to the ability to detail the pre-intervention coronary anatomy and identify the features indicative of sub-optimal stent deployment, ICI techniques can be utilised to improve coronary interventions in different clinical scenarios. More recently large randomized clinical trials on ICI guidance confirmed the clinical effectiveness of this approach especially in complex high-risk interventions. [ABSTRACT FROM AUTHOR]

In the past 20 years, numerous percutaneous vascular closure devices have been tested and compared with manual compression and to surgical cut-down. The suture-mediated closure device Perclose ProGlide™ system (Abbott Vascular, CA, USA) emerged as a safe and effective alternative for many procedures requiring either small or large bore vascular accesses. In this review, we will discuss the characteristics of this vascular closure device and the main studies that proved its potential to reduce vascular complications, time to deambulation, time to discharge and patient discomfort. [ABSTRACT FROM AUTHOR]

Great progress in the development of new semiconducting polymers over the last two decades alongside improved understanding of electron transport mechanisms have resulted in a dramatic increase in the electron mobility of these materials making them promising candidates for electronic and thermoelectric applications. Heat transport phenomena, on the other hand—which govern thermal conductivity—have not received as much attention up to date. In spite of the simplicity of the principle behind the measurement of thermoelectric properties, the combined uncertainty in thermoelectric figure of merit zT could easily reach 50% with the largest uncertainty coming from thermal conductivity measurements. Such a high measurement uncertainty, often comparable to relative variations in zT encountered when optimizing within a given class of materials, prevents the study of structure-thermal property relationships. Here we present a protocol for the measurement of the thermal conductivity of thin films with reduced measurement uncertainty, which allowed us to investigate the effect of microstructural changes on the thermal conductivity of the conjugated polymer P(NDI2OD-T2). We show that the enhancement of the thermal conductivity upon annealing is much less pronounced than the corresponding increase in the electron mobility that has been reported under the same annealing conditions in the literature. This suggests that semicrystalline conjugated polymers in which thermal transport remains limited by the amorphous domain boundaries in between crystalline grains could be a suitable system for realizing the electron-crystal phonon glass concept and enable higher performance thermoelectric materials. [ABSTRACT FROM AUTHOR]

Using a thermoelectric measurement, we demonstrate the nucleation and detection of a single 360° homochiral Néel domain wall (DW), formed by an independently nucleated pair of 180° Néel DWs having the same helicity in a perpendicular magnetic anisotropy track. The DW formation is governed by strong interfacial Dzyaloshinskii-Moriya interaction (DMI) and detected at room temperature using the anomalous Nernst effect (ANE). A large DMI can be generated at an interface where the symmetry is broken between a material having a large spin-orbit coupling and a thin ferromagnetic layer. The ANE voltage, V ANE ∝ ∇ T × M , is sensitive to the magnitude of the out-of-plane magnetization M through a confined in-plane temperature gradient ∇T and allows for the direct thermoelectrical detection of the DW position with nanoscale accuracy along the track. Here, we present evidence that independently nucleated pairs of 180° Néel DWs in microwire devices can be brought together by an applied magnetic field to form a 360° homochiral Néel DW. Subsequently, we show that a strong magnetic field needs to be applied in order to annihilate the 360° DW due to the strong interfacial DMI in our Pt/Co(0.6nm)/AlOx multilayers. In addition to enabling a high magnetic storage and data transfer rate with low power consumption in novel computational and storage devices, such DWs facilitate a reduction in bit size down to a few nanometers with metastability. [ABSTRACT FROM AUTHOR]

Ambipolar organic field-effect transistors (OFETs) have both of hole and electron enhancements in charge transport. The characteristics of conjugated diketopyrrolopyrrole ambipolar OFETs depend on the metal-contact surface treatment for charge injection. To investigate the charge-injection characteristics of ambipolar transistors, these devices are processed via various types of self-assembled monolayer treatments and annealing. We conclude that treatment by the self-assembled monolayer 1-decanethiol gives the best enhancement of electron charge injection at both 100 and 300 °C annealing temperature. In addition, the contact resistance is calculated by using two methods: One is the gated four-point probe (gFPP) method that gives the voltage drop between channels, and the other is the simultaneous contact resistance extraction method, which extracts the contact resistance from the general transfer curve. We confirm that the gFPP method and the simultaneous extraction method give similar contact resistance, which means that we can extract contact resistance from the general transfer curve without any special contact pattern. Based on these characteristics of ambipolar p- and n-type transistors, we fabricate inverter devices with only one active layer. [ABSTRACT FROM AUTHOR]

We review the Stille coupling synthesis of P(DPP2OD-T) (Poly[[2,5-di(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-3,6-diyl]-alt-[2,2':5',2"-terthiophene-5,5"-diyl]]) and show that high-quality, high molecular weight polymer chains are already obtained after as little as 15 min of reaction time. The results of UV-vis spectroscopy, grazing incidence wide-angle X-ray scattering (GIWAXS), and atomic force microscopy show that longer reaction times are unnecessary and do not produce any improvement in film quality. We achieve the best charge transport properties with polymer batches obtained from short reaction times and demonstrate that the catalyst washing step is responsible for the introduction of charge-trapping sites for both holes and electrons. These trap sites decrease the charge injection efficiency, strongly reducing the measured currents. The careful tuning of the synthesis allows us to reduce the reaction time by more than 100 times, achieving a more environmentally friendly, less costly process that leads to high and balanced hole and electron transport, the latter being the best reported for an isotropic, spin-coated DPP polymer. [ABSTRACT FROM AUTHOR]

We performed an in-depth study of high molecular weight poly[3,6-(dithiophene-2-yl)-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-thieno[3,2-b]thiophene] P(DPP2OD-TT) synthesized through the Stille coupling polycondensation in order to understand the correlation between molecular weight, processing conditions and charge transport. We observed a rapid increase in its aggregation in solution with increasing molecular weight which strongly limits the solubility and processability for weight average molecular weights beyond 200 kg mol−1. This results in severe limitation in the charge transport properties of the polymer. We further observe the presence of bulk electronic defects in all different polymer batches that severely limit the current flow and manifest themselves in organic field effect transistors as apparent charge density dependence of the mobility. These defects are passivated by exposure to an ambient atmosphere, as confirmed by an increase in current and mobility that is no more charge density dependent. This is further confirmed by the result of chemical doping using 2,2-(perfluoronaphthalene-2,6-diylidene)dimalononitrile, F6TCNNQ, which leads to the filling of the trap states and a higher charge density independent mobility of up to 1 cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]

Polymer semiconductors provide unique possibilities and flexibility in tailoring their optoelectronic properties to match specific application demands. The recent development of semicrystalline polymers with strongly improved charge transport properties forces a review of the current understanding of the charge transport mechanisms and how they relate to the polymer's chemical and structural properties. Here, the charge density dependence of field effect mobility in semicrystalline polymer semiconductors is studied. A simultaneous increase in mobility and its charge density dependence, directly correlated to the increase in average crystallite size of the polymer film, is observed. Further evidence from charge accumulation spectroscopy shows that charges accumulate in the crystalline regions of the polymer film and that the increase in crystallite size affects the average electronic orbitals delocalization. These results clearly point to an effect that is not caused by energetic disorder. It is instead shown that the inclusion of short range coulomb repulsion between charge carriers on nanoscale crystalline domains allows describing the observed mobility dependence in agreement with the structural and optical characterization. The conclusions that are extracted extend beyond pure transistor characterization and can provide new insights into charge carrier transport for regimes and timescales that are relevant to other optoelectronic devices. [ABSTRACT FROM AUTHOR]

A model for the extraction of the charge density dependent mobility and variable contact resistance in thin film transistors is proposed by performing a full derivation of the current-voltage characteristics both in the linear and saturation regime of operation. The calculated values are validated against the ones obtained from direct experimental methods. This approach allows unambiguous determination of gate voltage dependent contact and channel resistance from the analysis of a single device. It solves the inconsistencies in the commonly accepted mobility extraction methods and provides additional possibilities for the analysis of the injection and transport processes in semiconducting materials. [ABSTRACT FROM AUTHOR]

We investigated the correlation between the polymer backbone structural regularity and the charge transport properties of poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenediimide-2,6-diyl]-a.r-5,5'-(2,2'-bithio-phene)} [P(NDI2OD-T2)], a widely studied semiconducting polymer exhibiting high electron mobility and an unconventional micromorphology. To understand the influence of the chemical structure and crystal packing of conventional regioregular P(NDI2OD-T2) [RR-P(NDI2OD-T2)] on the charge transport, the corresponding regioirregular polymer RI- P(NDI2OD-T2) was synthesized. By combining optical, X-ray, and transmission electron microscopy data, we quantitatively characterized the aggregation, crystallization, and backbone orientation of all of the polymer films, which were then correlated to the electron mobilities in electron-only diodes. By carefully selecting the preparation conditions, we were able to obtain RR-P(NDI2OD-T2) films with similar crystalline structure along the three crystallographic axes but with different orientations of the polymer chains with respect to the substrate surface. RI-P(NDI2OD-T2), though exhibiting a rather similar LUMO structure and energy compared with the regioregular counterpart, displayed a very different packing structure characterized by the formation of ordered stacks along the lamellar direction without detectible π-stacking. Vertical electron mobilities were extracted from the space-charge-limited currents in unipolar devices. We demonstrate the anisotropy of the charge transport along the different crystallographic directions and how the mobility depends on π-stacking but is insensitive to the degree or coherence of lamellar stacking. The comparison between the regioregular and regioirregular polymers also shows how the use of large planar functional groups leads to improved charge transport, with mobilities that are less affected by chemical and structural disorder with respect to classic semicrystalline polymers such as poly(3-hexylthiophene). [ABSTRACT FROM AUTHOR]

We present an optical spectroscopy study on the role of oxygen and water in electron trapping and storage/bias-stress degradation of n-type polymer field-effect transistors based on one of the most widely studied electron transporting conjugated polymers, poly{[N,N9-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bisthiophene)} (P(NDI2OD-T2)). We combine results obtained from charge accumulation spectroscopy, which allow optical quantification of the concentration of mobile and trapped charges in the polymer film, with electrical characterization of P(NDI2OD-T2) organic field-effect transistors to study the mechanism for storage and bias-stress degradation upon exposure to dry air/oxygen and humid nitrogen/water environments, thus separating the effect of the two molecules and determining the nature of their interaction with the polymer. We find that the stability upon oxygen exposure is limited by an interaction between the neutral polymer and molecular oxygen leading to a reduction in electron mobility in the bulk of the semiconductor. We use density functional theory quantum chemical calculations to ascribe the drop in mobility to the formation of a shallow, localized, oxygen-induced trap level, 0.34 eV below the delocalized lowest unoccupied molecular orbital of P(NDI2OD-T2). In contrast, the stability of the polymer anion against water is limited by two competing reactions, one involving the electrochemical oxidation of the polymer anion by water without degradation of the polymer and the other involving a radical anion-catalyzed chemical reaction of the polymer with water, in which the electron can be recycled and lead to further degradation reactions, such that a significant portion of the film is degraded after prolonged bias stressing. Using Raman spectroscopy, we have been able to ascribe this to a chemical interaction of water with the naphthalene diimide unit of the polymer. The degradation mechanisms identified here should be considered to explain electron trapping in other rylene diimides and possibly in other classes of conjugated polymers as well. [ABSTRACT FROM AUTHOR]

Polymer transistors are being intensively developed for next-generation flexible electronics. Blends comprising a small amount of semiconducting polymer mixed into an insulating polymer matrix have simultaneously shown superior performance and environmental stability in organic field-effect transistors compared with the neat semiconductor. Here we show that such blends actually perform very poorly in the undoped state, and that mobility and on/off ratio are improved dramatically upon moderate doping. Structural investigations show that these blend layers feature nanometre-scale semiconductor domains and a vertical composition gradient. This particular morphology enables a quasi three-dimensional spatial distribution of semiconductor pathways within the insulating matrix, in which charge accumulation and depletion via a gate bias is substantially different from neat semiconductor, and where high on-current and low off-current are simultaneously realized in the stable doped state. Adding only 5?wt% of a semiconducting polymer to a polystyrene matrix, we realized an environmentally stable inverter with gain up to 60. [ABSTRACT FROM AUTHOR]

There is evidence that the photo-generated singlet exciton in polycrystalline pentacene films undergoes rapid and efficient fission to tbrm two triplet excitons. However, the role of exciton fission in pentacene has been controversial, with previous studies putting forward alternate relaxation pathways for the singlet exciton, such as excimer or charge formation, or internal conversion to a doubly excited exciton. We report temperature- and angular-dependent ultrafast transient optical absorption measurements in a wide spectral and temporal window. Angular-dependent transient spectra identify a common origin to photo-induced absorptions at 530 and 860 nm, which we associate with triplet excitons. These constitute the dominant relaxation channel for singlet excitons. Other features, particularly near 620 nm, previously assigned to excimers or electronic charges, are shown to be caused by thermal modulation from the optical pump. [ABSTRACT FROM AUTHOR]