Mixing-induced anisotropic correlations in molecular crystalline systems

We investigate the structure of mixed thin films composed of pentacene (PEN) and diindenoperylene (DIP) using X-ray reflectivity and grazing incidence X-ray diffraction. For equimolar mixtures we observe vanishing in-plane order coexisting with an excellent out-of-plane order, a yet unreported disordering behavior in binary mixtures of organic semiconductors, which are crystalline in their pure form. One approach to rationalize our findings is to introduce an anisotropic interaction parameter in the framework of a mean field model. By comparing the structural properties with those of other mixed systems, we discuss the effects of sterical compatibility and chemical composition on the mixing behavior, which adds to the general understanding of interactions in molecular mixtures.Comment: 5 pages, 5 figures, accepted by Phys. Rev. Let

Real-time, label-free, intraoperative visualization of peripheral nerves and microvasculatures using multimodal optical imaging techniques

Accurate, real-time identification and display of critical anatomic structures, such as the nerve and vasculature structures, are critical for reducing complications and improving surgical outcomes. Human vision is frequently limited in clearly distinguishing and contrasting these structures. We present a novel imaging system, which enables noninvasive visualization of critical anatomic structures during surgical dissection. Peripheral nerves are visualized by a snapshot polarimetry that calculates the anisotropic optical properties. Vascular structures, both venous and arterial, are identified and monitored in real-time using a near-infrared laser-speckle-contrast imaging. We evaluate the system by performing in vivo animal studies with qualitative comparison by contrast-agent-aided fluorescence imaging

Near-forward Raman selection rules of the phonon-polariton created by alloying in (Zn,Be)Se

The Raman selection rules of the (ZnSe, BeSe) mixed phonon polariton created by alloying in the three mode (1ZnSe, 2BeSe) ZnBeSe system, whose dramatic S like dispersion covers the large frequency gap between the ZnSe and BeSe spectral ranges, is studied in its wave vector dependence by near forward scattering. Both the collapse regime away from the Brillouin zone centre and the reinforcement regime near the Brillouin zone centre are addressed, using appropriate laser lines and Be contents. We find that in both regimes the considered phonon polariton, in fact a transverse mode with mixed mechanical and electrical character, obeys the same nominal Raman selection rules as its purely mechanical variant commonly observed in the backscattering geometry. Besides, marked differences in the phonon polariton Raman lineshapes in the two regimes give a hint about how the phonon polariton electrical field E develops while descending the S like dispersion towards the Brillouin zone centre. In the reinforcement regime E is large, leading to intramode on top of intermode transfers of oscillator strength mediated by E between the two BeSe modes, that both exhibit a fine structure on account of the alloy disorder. In contrast, in the collapse regime E remains weak, as testified by the absence of intramode transfer. The discussion is supported by contour modeling of the multi phonon polariton Raman lineshapes in their wave vector dependence within the linear dielectric approach.Comment: 16 pages, 7 figure

Investigation of the thermoelectric response in conducting polymers doped by solid-state diffusion

The thermoelectric effect is a physical phenomenon which intricately relates the thermal energy of charge carriers to their charge transport. Understanding the mechanism of this interaction in different systems lies at the heart of inventing novel materials which can revolutionize thermoelectric power gener- ation technology. Despite a recent surge of interest in organic thermoelectric materials, the community has had difficulties in formulating the charge trans- port mechanism in the presence of a significant degree of disorder. Here, we analyze the thermoelectric properties of various conducting polymers doped by a solid-state diffusion of dopant molecules based on a transport model with a power-law energy-dependence of transport function. A fine control of the degree of doping via post-doping annealing provides an accurate empirical evidence of a strong energy dependence of the carrier mobility in the conducting polymers. A superior thermoelectric power factor of conducting polymers doped by solid-state diffusion to that of other doping methods can be attributed to a resulting higher intrinsic mobility and higher free carrier concentration.The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n 610115. Keehoon Kang thanks the for financial support from Samsung Scholarship Foundation and the National Creative Research Laboratory program (Grant No. 2012026372) through the National Research Foundation of Korea, funded by the Korean Ministry of Science and ICT. K.B. acknowledges funding by the German Research Foundation (BR 4869/1-1)

Pentacene-Gate Dielectric Interface Modification with Silicon Nanoparticles for OTFTs

AbstractWe report on the properties of pentacene layers and OTFTs (Organic Thin Film Transistors) deposited on semiconductor-gate insulator interfaces covered with silicon nanoparticles (SiNPs) monolayer prepared by the Langmuir-Blodgett method compared to a reference sample (without SiNPs) prepared in an otherwise identical way. To analyse the structural quality, micro-Raman spectroscopy was employed and the correspondence between thin and bulk phase of the integral intensities peaks ratio (α) at 1154 and 1158cm-1 (α = Int1154 /Int1158) was evaluated. The AFM analysis of the pentacene layers reveals that the different surface treatment of SiO2 gate insulator (hydrophobic or hydrophilic) before SiNPs monolayer deposition has a distinct influence on the formation of different pentacene grain size and morphology. We demonstrate the higher time stability of pentacene OTFT and increasing of saturation current (∼ 2.5 ×) behavior after storage time if the semiconductor-gate insulator interface is modified using a SiNP monolayer

A Novel Mitigation Mechanism for Photo-Induced Trapping in an Anthradithiophene Derivative Using Additives

© 2020 Wiley-VCH GmbH A novel trap mitigation mechanism using molecular additives, which relieves a characteristic early turn-on voltage in a high-mobility p-type acene-based small-molecule organic semiconductor, when processed from hydrous solvents, is reported. The early turn-on voltage is attributed to photo-induced trapping, and additive incorporation is found to be very effective in suppressing this effect. Remarkably, the molecular additive does not disturb the charge transport properties of the small-molecule semiconductor, but rather intercalates in the crystal structure. This novel technique allows for the solution-processing of small molecular semiconductors from hydrous solvents, greatly simplifying manufacturing processes for large-area electronics. Along with various electric and spectroscopic characterization techniques, simulations have given a deeper insight into the trap mitigation effect induced by the additive

Micellar Liquid Chromatographic Determination of Carbaryl and 1-Naphthol in Water, Soil, and Vegetables

A liquid chromatographic procedure has been developed for the determination of carbaryl, a phenyl-N-methylcarbamate, and its main metabolite 1-naphthol, using a C18 column (250 mm  ×  4.6 mm) with a micellar mobile phase and fluorescence detection at maximum excitation/emission wavelengths of 225/333 nm, respectively. In the optimization step, surfactants sodium dodecyl sulphate (SDS), Brij-35 and N-cetylpyridinium chloride monohydrate, and organic solvents propanol, butanol, and pentanol were considered. The selected mobile phase was 0.15 M SDS-6% (v/v)-pentanol-0.01 M NaH2PO4 buffered at pH 3. Validation studies, according to the ICH Tripartite Guideline, included linearity (r > 0.999), limit of detection (5 and 18 ng mL−1, for carbaryl and 1-naphthol, resp.), and limit of quantification (15 and 50 ng mL−1, for carbaryl and 1-naphthol, resp.), with intra- and interday precisions below 1%, and robustness parameters below 3%. The results show that the procedure was adequate for the routine analysis of these two compounds in water, soil, and vegetables samples