The functionality of common organic semiconductor materials is determined by their chemical structure and crystal modification. While the former can be fine-tuned via synthesis, a priori control over ...the crystal structure has remained elusive. We show that the surface tension is the main driver for the plate-like crystallization of a novel small organic molecule n-type semiconductor at the liquid–air interface. This interface provides an ideal environment for the growth of millimeter-sized semiconductor platelets that are only few nanometers thick and thus highly attractive for application in transistors. On the basis of the novel high-performance perylene diimide, we show in as-grown, only 3 nm thin crystals electron mobilities of above 4 cm2/(V s) and excellent bias stress stability. We suggest that the established systematics on solvent parameters can provide the basis of a general framework for a more deterministic crystallization of other small molecules.
We present an in situ nanobeam grazing-incidence X-ray diffraction (nanoGIXD) study of real-sized organic field effect transistors (OFET) under applied voltage. The nano-sized beam allows for ...spatially resolved monitoring of the structural behavior across the poly(3-hexylthiophene) (P3HT) polymer channel and the interfacial regions of the source and drain gold electrodes before and after the operation cycle. We observe major alterations of the gold contacts, in particular diffusion of Au atoms into the polymer channel and a local reorientation of the recrystallized Au nanocrystallites quantified by Hermans' orientation factors. Therefore, the initially sharp electrode-polymer interfaces are significantly modified as a result of device operation. Our findings demonstrate that nanoGIXD has a high potential to probe functionality and reliability of working organic devices.
Supramolecular structure of ultrathin films of hemicyanine dye bearing a crown ether group (CrHCR) was tuned by lateral pressure and investigated by means of compression isotherms, UV–vis and ...fluorescence spectroscopies, and X-ray reflectivity. Two different types of aggregation were revealed, depending on the absence or the presence of metal cations in the water subphase. While CrHCR forms at high surface pressures head-to-tail stacking aggregates on pure water, changing the subphase to a metal-cation-containing one leads to the appearance of well-defined excimers with head-to-head orientation. The structure of monolayers transferred onto solid supports by the Langmuir–Blodgett (LB) technique was examined by use of X-ray reflectivity measurements and molecular modeling. A model of cation-induced excimer formation in hemicyanine Langmuir monolayers is proposed. Finally, fluorescence emission properties of LB films of CrHCR can be managed by appropriate changes in the subphase composition, this last one determining the type of chromophore aggregation.
Here is presented raw and analysed data collected during study of the evolution, with uniaxial stretching, of the electrical and microcrystalline characteristics of polystyrene sulfonate doped ...poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) organic electrochemical transistors (OECTs). X-ray diffraction data from GIWAXS measurements of the PEDOT:PSS material, performed at the SOLEIL light source are presented in raw and partially analysed forms. Current-voltage data, collected concurrently with the GIWAXS data, are also presented, and the evolution of the transconductance of the OECT devices with stretching is shown. GIWAXS data are only examined along the qz specular reflection ridge, and scans along this ridge are extracted and presented. However, the off-specular data may also be of interest to readers and is therefore made available here in its entirety.
The control of structure formation in the active layers of organic solar cells allows for improvement in their processability and enhancement of the efficiency of the final devices. In the present ...work,
in situ
studies of film formation from binary toluene solutions of an electron donor, poly(3-hexylthiophene) (P3HT), and an electron acceptor such as 6,6-phenyl-C-61-butyric acid methyl ester (PCBM) or indene-C
60
bisadduct (ICBA) have been conducted. These experiments were carried out using GIWAXS with simultaneous electric current measurements. The comparative analysis of the intensity of the amorphous halo, and the 100 and 020 peaks of P3HT reveals the development of the semicrystalline morphology of the donor through a partly-ordered phase. The experiments show the impact of the chemical structure of the acceptor, as well as that of the donor : acceptor ratio on the kinetics of drying and crystallization. The optimal bulk heterojunction morphology was achieved for P3HT : ICBA 1 : 1, which exhibited the highest value of current. A more efficient phase separation in non-annealed P3HT:ICBA films as compared to P3HT:PCBM was accounted for by the differences in solubility of the components in toluene. The structure formation during solvent evaporation can be subdivided into three stages, including the ordering of the polymer in solution, phase separation during precipitation, and the perfectioning of P3HT crystals in the dry film.
The control of structure formation in the active layers of organic solar cells allows for improvement in their processability and efficiency of the final devices.
The influence of annealing temperature on the structural and electrical properties of conjugated poly(dodecyl-quaterthiophene) (PQT-12) polymer films is exploited. The temperature induced changes of ...structural parameters are monitored by in situ grazing incident X-ray diffraction (GIXD) and the conductivity. They are complemented by studies of the dielectric properties using variable angle spectroscopic ellipsometry (VASE). An increase of the scattered intensity, the size of the crystalline domains, and the current response is observed for a first thermal cycle with stepwise heating up to 90 °C, which revealed two polymorphs with different degrees of interdigitation in PQT-12. Irreversible changes are observed for the second cycle with a higher thermal budget up to 140 °C and are connected with a transition from the highly ordered to powder-like disordered phase for the main PQT-12 form whereas the second polymorph with stronger interdigitation completely vanished. In agreement with these observations high-temperature VASE studies demonstrated a blue shift of the transitions with a reduction in the conjugation length caused by an increase in the twist and torsion of the backbone. Combined GIXD, VASE, and electrical characterizations show that PQT-12 exhibits a complex interplay between two polymorphs with a strong influence on the charge carrier transport depending on the thermal budget employed.
Mathematical models of different degrees of complexity, describing the motion of a snow avalanche along a path with given center line and spatially varying width, are formulated and compared. The ...most complete model integrates the balance equations for mass and momentum over the cross-section and achieves closure through an entrainment function based on shock theory and a modified Voellmy bed friction law where the Coulombic contribution to the bed shear stress is limited by the shear strength of the snow cover. A simplified model results from integrating these balance equations over the (time-dependent) length of the flow and postulating weak similarity of the evolving avalanche shape. On path segments of constant inclination, it can be solved for the flow depth and speed of the front in closed form in terms of the imaginary error function. Finally, the very simplest model assumes constant flow height and length. On an inclined plane, the evolution of flow depth and velocity predicted by the simplified model are close to those from the full model without entrainment and with corresponding parameters, but the simplest model with constant flow depth predicts much higher velocity values. If the friction coefficient is varied in the full model with entrainment, there can be non-monotonous behavior due to the non-linear interplay between entrainment and the limitation on the Coulomb friction.
The effect of the drug Stimforte on infection by the Hepatitis C virus (HCV) has been studied. Stimforte partially inhibits HCV infection at a dose of 100 μg/mouse and almost completely at a dose of ...300 μg/mouse within 24 h after administration of the drug. The mice sera resulting after 24 h in the presence of 100 and 300 µg/mouse of Stimforte effectively inhibit the production of HCV. Doses of 150, 200, and 250 µg/mouse are not effective. Stimulation of interferon-β (IFN-β) production is only observed at doses of 100 and 300 µg/mouse, which explains well the neutralizing capacity of the sera. The amount of IFN-γ also correlates well with the antiviral activity and neutralizing activity of mice sera. The drug practically does not stimulate production of IFN-λ. Thus, the neutralizing activity of sera and the antiviral activity are largely determined by the 1st and 2nd IFN groups.
This study was performed to study the dynamics of polymorphonuclear leukocyte (PMNL) accumulation in human cerebral infarction and its association with neurological outcome and brain lesion.
A total ...of 88 patients diagnosed as having hemispheric ischemic stroke were examined. PMNL accumulation was studied using technetium-99m hexamethylpropyleneamine oxime (99mTc HMPAO)-labeled leukocyte brain single-photon emission computed tomography (SPECT). Volume of brain infarction was evaluated by CT scan. The Mathew Scale was used for neurological assessment. Dynamics of PMNL accumulation was studied at 3 to 6, 6 to 12, and 12 to 24 hours and 6 to 9, 28 to 30, and 90 days after stroke onset. In parallel, at admission, at 6 to 9 days, and at 28 to 30 days neurological outcome and infarction volume were evaluated.
Generally, PMNL accumulation progressively increased during 6 to 24 hours after stroke, remained at a high level up to 6 to 9 days and then declined. With the use of cluster analysis, all patients were subdivided into three groups: patients with severe PMNL accumulation that dramatically increased within 12 hours after stroke onset and persisted even at 28 to 30 days (group A); those with moderate PMNL accumulation that significantly decreased at 30 days (group B); and those with mild PMNL accumulation that decreased at 6 to 9 days (group C). Baseline neurological deficit and brain tissue damage at admission appear to be at a similar level for all groups of patients. In dynamics, however, in patients with severe PMNL accumulation, neurological outcome was worse and infarction volume larger than in patients with less marked PMNL accumulation.
The present clinical study confirms that PMNLs intensively accumulate in the regions of cerebral infarction. The present study revealed that this accumulation correlated with the severity of the brain tissue damage and poor neurological outcome.
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