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1. Molecular understanding of new-particle formation from <i>α</i>-pinene between −50 and +25 °C

   https://doi.org/10.5194/acp-20-9183-2020  

   Simon, Mario ; Dada, Lubna ; Heinritzi, Martin ; Scholz, Wiebke ; Stolzenburg, Dominik ; Fischer, Lukas ; Wagner, Andrea C. ; Kürten, Andreas ; Rörup, Birte ; He, Xu-Cheng ; et al ( January 2020 , Atmospheric Chemistry and Physics)

   null (Ed.)

   Abstract. Highly oxygenated organic molecules (HOMs) contributesubstantially to the formation and growth of atmospheric aerosol particles,which affect air quality, human health and Earth's climate. HOMs are formedby rapid, gas-phase autoxidation of volatile organic compounds (VOCs) suchas α-pinene, the most abundant monoterpene in the atmosphere. Due totheir abundance and low volatility, HOMs can play an important role innew-particle formation (NPF) and the early growth of atmospheric aerosols,even without any further assistance of other low-volatility compounds suchas sulfuric acid. Both the autoxidation reaction forming HOMs and theirNPF rates are expected to be strongly dependent ontemperature. However, experimental data on both effects are limited.Dedicated experiments were performed at the CLOUD (Cosmics Leaving OUtdoorDroplets) chamber at CERN to address this question. In this study, we showthat a decrease in temperature (from +25 to −50 ∘C) results ina reduced HOM yield and reduced oxidation state of the products, whereas theNPF rates (J1.7 nm) increase substantially.Measurements with two different chemical ionization mass spectrometers(using nitrate and protonated water as reagent ion, respectively) providethe molecular composition of the gaseous oxidation products, and atwo-dimensional volatility basis set (2D VBS) model provides their volatilitydistribution. The HOM yield decreases with temperature from 6.2 % at 25 ∘C to 0.7 % at −50 ∘C. However, there is a strongreduction of the saturation vapor pressure of each oxidation state as thetemperature is reduced. Overall, the reduction in volatility withtemperature leads to an increase in the nucleation rates by up to 3orders of magnitude at −50 ∘C compared with 25 ∘C. Inaddition, the enhancement of the nucleation rates by ions decreases withdecreasing temperature, since the neutral molecular clusters have increasedstability against evaporation. The resulting data quantify how the interplaybetween the temperature-dependent oxidation pathways and the associatedvapor pressures affect biogenic NPF at the molecularlevel. Our measurements, therefore, improve our understanding of purebiogenic NPF for a wide range of tropospherictemperatures and precursor concentrations. 

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2. Hybrid conjugated polymers with alternating dithienosilole or dithienogermole and tricoordinate boron units

   https://doi.org/10.1039/c7py01790a  

   Adachi, Yohei ; Ooyama, Yousuke ; Ren, Yi ; Yin, Xiaodong ; Jäkle, Frieder ; Ohshita, Joji ( January 2018 , Polymer Chemistry)

   Conjugated polymers composed of tricoordinate boron and π-conjugated units possess extended conjugation with relatively low-lying LUMOs arising from p B –π interactions. However, donor–acceptor (D–A) polymers that feature triorganoboranes alternating with highly electron-rich donors remain scarce. We present here a new class of hybrid D–A polymers that combine electron-rich dithienosiloles or dithienogermoles with highly robust tricoordinate borane acceptors. Polymers of modest to high molecular weight are readily prepared by Pd-catalyzed Stille coupling reaction of bis(halothienyl)boranes and distannyldithienosiloles or -germoles. The polymers are obtained as dark red solids that are stable in air and soluble in common organic solvents. Long wavelength UV-vis absorptions at ca. 500–550 nm indicate effective π-conjugation and pronounced D–A interactions along the backbone. The emission maxima occur at wavelengths longer than 600 nm in solution and experience further shifts to lower energy with increasing solvent polarity, indicative of strong intramolecular charge transfer (ICT) character of the excited state. The powerful acceptor character of the borane comonomer units in the polymer structures is also evident from cyclic voltammetry (CV) analyses that reveal relatively low-lying LUMO levels of the polymers, enhancing the D–A interaction. Density functional theory (DFT) calculations on model oligomers further support these experimental observations. 

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3. Artificial intelligence-enhanced quantum chemical method with broad applicability

   https://doi.org/10.1038/s41467-021-27340-2  

   Zheng, Peikun ; Zubatyuk, Roman ; Wu, Wei ; Isayev, Olexandr ; Dral, Pavlo O. ( December 2021 , Nature Communications)

   Abstract High-level quantum mechanical (QM) calculations are indispensable for accurate explanation of natural phenomena on the atomistic level. Their staggering computational cost, however, poses great limitations, which luckily can be lifted to a great extent by exploiting advances in artificial intelligence (AI). Here we introduce the general-purpose, highly transferable artificial intelligence–quantum mechanical method 1 (AIQM1). It approaches the accuracy of the gold-standard coupled cluster QM method with high computational speed of the approximate low-level semiempirical QM methods for the neutral, closed-shell species in the ground state. AIQM1 can provide accurate ground-state energies for diverse organic compounds as well as geometries for even challenging systems such as large conjugated compounds (fullerene C 60 ) close to experiment. This opens an opportunity to investigate chemical compounds with previously unattainable speed and accuracy as we demonstrate by determining geometries of polyyne molecules—the task difficult for both experiment and theory. Noteworthy, our method’s accuracy is also good for ions and excited-state properties, although the neural network part of AIQM1 was never fitted to these properties. 

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4. Vapor‐Phase‐Gating‐Induced Ultrasensitive Ion Detection in Graphene and Single‐Walled Carbon Nanotube Networks

   https://doi.org/10.1002/adma.201606883  

   Hao, Ji ; Li, Bo ; Jung, Hyun Young ; Liu, Fangze ; Hong, Sanghyun ; Jung, Yung Joon ; Kar, Swastik ( April 2017 , Advanced Materials)

   Designing ultrasensitive detectors often requires complex architectures, high‐voltage operations, and sophisticated low‐noise measurements. In this work, it is shown that simple low‐bias two‐terminal DC‐conductance values of graphene and single‐walled carbon nanotubes are extremely sensitive to ionized gas molecules. Incident ions form an electrode‐free, dielectric‐ or electrolyte‐free, bias‐free vapor‐phase top‐gate that can efficiently modulate carrier densities up to ≈0.6 × 10¹³cm⁻². Surprisingly, the resulting current changes are several orders of magnitude larger than that expected from conventional electrostatic gating, suggesting the possible role of a current‐gain inducing mechanism similar to those seen in photodetectors. These miniature detectors demonstrate charge–current amplification factor values exceeding 10⁸A C⁻¹in vacuum with undiminished responses in open air, and clearly distinguish between positive and negative ions sources. At extremely low rates of ion incidence, detector currents show stepwise changes with time, and calculations suggest that these stepwise changes can result from arrival of individual ions. These sensitive ion detectors are used to demonstrate a proof‐of‐concept low‐cost, amplifier‐free, light‐emitting‐diode‐based low‐power ion‐indicator.

    

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5. Dynamic self-stabilization in the electronic and nanomechanical properties of an organic polymer semiconductor

   https://doi.org/10.1038/s41467-022-30801-x  

   Dobryden, Illia ; Korolkov, Vladimir V. ; Lemaur, Vincent ; Waldrip, Matthew ; Un, Hio-Ieng ; Simatos, Dimitrios ; Spalek, Leszek J. ; Jurchescu, Oana D. ; Olivier, Yoann ; Claesson, Per M. ; et al ( June 2022 , Nature Communications)

   The field of organic electronics has profited from the discovery of new conjugated semiconducting polymers that have molecular backbones which exhibit resilience to conformational fluctuations, accompanied by charge carrier mobilities that routinely cross the 1 cm²/Vs benchmark. One such polymer is indacenodithiophene-co-benzothiadiazole. Previously understood to be lacking in microstructural order, we show here direct evidence of nanosized domains of high order in its thin films. We also demonstrate that its device-based high-performance electrical and thermoelectric properties are not intrinsic but undergo rapid stabilization following a burst of ambient air exposure. The polymer’s nanomechanical properties equilibrate on longer timescales owing to an orthogonal mechanism; the gradual sweating-out of residual low molecular weight solvent molecules from its surface. We snapshot the quasistatic temporal evolution of the electrical, thermoelectric and nanomechanical properties of this prototypical organic semiconductor and investigate the subtleties which play on competing timescales. Our study documents the untold and often overlooked story of a polymer device’s dynamic evolution toward stability.

    

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