1,721,055 research outputs found
New approach for analyzing the vertical structure of polymer thin films based on surface-enhanced Raman scattering
No full textWe report on a new approach for measuring
the chemical composition of the 20 nanometers at the top or
bottom of a polymer film. This approach is based on a
variation of the surface enhanced Raman scattering effect with
laser illumination through a thin gold layer (∼4 nm). We show
that the introduction of the thin gold layer has little or no
effect on the morphology of the film that is spin coated on top
of it. We demonstrate that this technique has better than 20
nanometer vertical resolution by studying bilayers of polyfluorines with varying thicknesses and by showing the existence of top
and bottom wetting layers in a polymer blend of the same polymers. We also show that the top wetting layer is thinner than the
bottom one. The difference in thicknesses explains how a solar cell with an electron blocking layer at the cathode works
POLIMERI AD ALTE PRESTAZIONI PER L' OTTICA NON LINEARE DEL SECONDO ORDINE OTTENUTI PER "GRAFTING" DI COMPLESSI CROMOFORICI SU POLI-4-VINILPIRIDINA
No full textN,N′-Dihydroxybenzene-1,2:4,5-tetracarboximide dihydrate
No full textIn the title compound, C10H4N2O6·2H2O, the organic molecule has crystallographically imposed inversion symmetry. The atoms of the three fused rings of the molecule are coplanar within 0.0246 (8) Å, while the two hydroxy O atoms are displaced from the mean plane of the molecule by 0.127 (1) Å. In the crystal, infinite near-planar layers of close-packed molecules are formed by hydrogen bonding between water O—H donor groups and carbonyl O-atom acceptors, and by weak interactions between C—H donor groups and water O-atom acceptors. The layers are parallel to the {102} family of planes. The stacked planes are held together by hydrogen bonding between N—OH donor groups and water O-atom acceptors
Short π‐Stacking in N‐Rich Ionic Aromatic Compounds
No full textReaction of N-rich conjugated bis(3,4-diamino-1,2,4-triazole)s with dilute hydrochloric acid affords bis(3,4-diamino-1,2,4-triazol-2-ium)chlorides. These compounds form layered structures in which planar layers of molecules are parallelly stacked. The π-stacking distance of the layers is
relatively short, as compared with all-carbon-containing aromatic compounds, ranging between 3.00 and 3.22 Å at 173 K, and several contacts shorter than the sum of van der Waals radii are observed in the crystal structures. The features of the crystal structures are discussed in terms of the high nitrogen content of the compounds and of the H-bonding patterns. Periodic ab initio theoretical calculations of the crystal
structures have allowed decomposing the lattice energy into various contributions in order to put up the relevance of van der Waals interactions for the π-stacking. In particular, it is found that van der Waals interactions account for about 10% of the total lattice energy and about 50% of the stacking energy (interlayer energy)
Interfacial charge doping effect in C8-DNTT/PDIF-CN2 heterojunction field-effect transistors
No full textIn the last 15 years, DNTT-based compounds have emerged as a new generation of hole-transporting (p-type) organic semiconductors with superior charge transport properties. Even today, indeed, this class of derivatives is under intense scrutiny for the achievement of high-performance field-effect transistors to be applied in the development of advanced organic circuitry. Here, we analyze the growth of evaporated C8-DNTT films on HMDS-treated SiO2 surfaces, highlighting the dependence of the related morphological and electrical properties on the substrate temperature (Tsub) held during film condensation. In this way, we identified a Tsub range able to guarantee high mobility values (larger than 2.5 cm2 V−1 s−1) and morphological features being more compatible for the growth of additional layers on their top surfaces. This finding was the basic point to investigate the deposition of n-type PDIF-CN2 films on bottom C8-DNTT layers for the fabrication of heterojunction field-effect transistors. The electrical characterization of these devices, providing a shift of the threshold voltages and a minor sensitivity to the bias stress effect in comparison with the single-layer C8-DNTT counterparts, suggests the formation of a charge accumulation region at the organic/organic interface. This scenario was confirmed by additional electrical analyses performed on complementary double-layer structures
Prospettive per il controllo dei nematodi fitoparassiti
No full textAtti VII Congresso Nazionale Nematologi
Crosslinkable organic glasses with quadratic nonlinear optical activity
No full textIn this paper, the use of a pure benzimidazole based dimethacrylic push pull chromophore has been investigated for the preparation of thin films exhibiting quadratic nonlinear optical (NLO) properties. To stabilize these NLO properties, the chromophore orientation has been frozen in a noncentrosymmetric arrangement by cross-linking the material using thermal polymerization induced by suitable initiators. The films present a very stable quadratic optical activity up to T = 152 degrees C with SHG coefficient d(33) of 14 pm/V measured at 1.9 mu m
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