Shortest path based decision making using probabilistic inference

Despite the extensive use of boron-modified phenol–formaldehyde polymers as insulating materials in soft magnetic composites (SMCs), the structure and arrangement of the inorganic cross-linking units in these systems have not been fully elucidated. To clarify the structure, configuration, and distribution of the boron cross-links in these materials, phenol–formaldehyde resins modified by boric acid were synthesized and characterized using advanced multiple-quantum ¹¹B–¹¹B MAS NMR correlation techniques combined with the quantum chemical geometry optimizations and the subsequent ¹¹B NMR chemical shielding calculations. The analyses of the resulting spectra revealed a well-evolved (high-density) phenol–formaldehyde polymer network additionally strengthened by nitrogen and boron cross-links. The boron-based cross-links were attributed to monoester (ca. 10%) and diester (ca. 90%) complexes (six-membered spirocyclic borate anions) with strictly tetrahedral coordination (B^IV). During the thermal treatment, the monoester and diester borate complexes underwent additional transformation in which the spirocyclic borate anions were more tightly incorporated into the polymer matrix via additional <i>N</i>-type (amino) cross-links. A ¹¹B–¹¹B double-quantum correlation MAS NMR experiment revealed that the majority of the monoester and diester borate complexes (ca. 80%) were uniformly distributed within and effectively isolated by the polymer matrix, with an average ¹¹B···¹¹B interatomic distance greater than 6 Å. A non-negligible part of the spirocyclic borate anion complexes (ca. 20%), however, existed in pairs or small clusters in which the average ¹¹B···¹¹B interatomic distance was less than 5.5 Å. In addition, the formation of homodimers (diester–diester) was demonstrated to be preferred over the formation of heteroclusters (monoester–diester)

Catalytic Properties of 3D Graphene-Like Microporous Carbons Synthesized in a Zeolite Template

[EN] The inherent properties of a single atomic carbon layer in graphene offer opportunities for the creation of catalytically active centers tailored on a molecular level on a support with high thermal stability and very high specific surface area. We demonstrate that organization of the two-dimensional system of the carbon layer into three-dimensional (3D) graphene-like catalytic materials with the connectivity of a pore network providing good accessibility to the active centers allows the preparation of catalytic materials that exploit the properties of graphene. In this study, 3D graphene-like microporous carbons, denoted as)6 beta-carbon and Y-carbon, were synthesized by nanocasting of beta (*BEA) and faujasite (FAU) zeolite templates. Structural analyses show that the materials are characterized by 3D-assembled and highly stable single-atom graphene an open porous system resembling the regular channel system of the zeolites with a specific surface area comparable to the surface area of graphene. The materials effectively catalyze the hydrogenation of alkenes, alkynes, and cycloalkenes into the corresponding alkanes and cycloalkanes. The materials facilitate catalytic intramolecular rearrangements, including the selective isomerization of double bonds and branching of linear chains, as well as stereoselective isomerization of unsaturated hydrocarbons. layers that formThis work was supported by the Grant Agency of the Czech Republic under project No. 15-12113S. The authors acknowledge the assistance provided by the Research Infrastructures NanoEnviCz (Project No. LM2015073) and Pro-NanoEnviCz (Project No. CZ.02.1.01/0.0/0.0/16_013/0001821), supported by the Ministry of Education, Youth and Sports of the Czech Republic.Sazama, P.; Pastvova, J.; Rizescu, C.; Tirsoaga, A.; Parvulescu, VI.; García Gómez, H.; Kobera, L.... (2018). Catalytic Properties of 3D Graphene-Like Microporous Carbons Synthesized in a Zeolite Template. ACS Catalysis. 8(3):1779-1789. https://doi.org/10.1021/acscatal.7b04086S177917898

How Photogenerated I₂ Induces I-Rich Phase Formation in Lead Mixed Halide Perovskites

Bandgap tunability of lead mixed halide perovskites (LMHPs) is a crucial characteristic for versatile optoelectronic applications. Nevertheless, LMHPs show the formation of iodide-rich (I-rich) phase under illumination, which destabilizes the semiconductor bandgap and impedes their exploitation. Here, it is shown that how I2, photogenerated upon charge carrier trapping at iodine interstitials in LMHPs, can promote the formation of I-rich phase. I2 can react with bromide (Br−) in the perovskite to form a trihalide ion I2Br− (Iδ−-Iδ+-Brδ−), whose negatively charged iodide (Iδ−) can further exchange with another lattice Br− to form the I-rich phase. Importantly, it is observed that the effectiveness of the process is dependent on the overall stability of the crystalline perovskite structure. Therefore, the bandgap instability in LMHPs is governed by two factors, i.e., the density of native defects leading to I2 production and the Br− binding strength within the crystalline unit. Eventually, this study provides rules for the design of chemical composition in LMHPs to reach their full potential for optoelectronic devices.</p

Perovskite-molecule composite thin films for efficient and stable light-emitting diodes

Abstract: Although perovskite light-emitting diodes (PeLEDs) have recently experienced significant progress, there are only scattered reports of PeLEDs with both high efficiency and long operational stability, calling for additional strategies to address this challenge. Here, we develop perovskite-molecule composite thin films for efficient and stable PeLEDs. The perovskite-molecule composite thin films consist of in-situ formed high-quality perovskite nanocrystals embedded in the electron-transport molecular matrix, which controls nucleation process of perovskites, leading to PeLEDs with a peak external quantum efficiency of 17.3% and half-lifetime of approximately 100 h. In addition, we find that the device degradation mechanism at high driving voltages is different from that at low driving voltages. This work provides an effective strategy and deep understanding for achieving efficient and stable PeLEDs from both material and device perspectives

Career in Polymers XI, Book of Abstracts

The book of abstracts contains the summaries of all the contributions to the Career in Polymers XI., workshop organized by the Institute of Macromolecular Chemistry AS CR, in Prague, 28-29 June, 2019. This meeting was organized under the auspices of UNESCO/IUPAC course in Polymer Science, and supported by Strategy AV21

Career in Polymers X, Book of Abstracts

The book of abstracts contains the summaries of all the contributions to the Career in Polymers X. workshop organized by the Institute of Macromolecular Chemistry AS CR, in Prague, 22-23 June, 2018. This meeting was organized under the auspices of UNESCO/IUPAC course in Polymer Science, and supported by Strategy AV21 and Draslovka a.s

Structural stability of aluminosilicate inorganic polymers: Influence of the preparation procedure

The stability of amorphous aluminosilicate inorganic polymer (AIP) systems with regard to the structural role of water molecules incorporated in inorganic matrix is discussed. Innovative approach to preparation of amorphous AIP systems with identical chemical composition but differing in structural and mechanical behavior is introduced. It is shown that even small changes in the manufacture dramatically affect mechanical properties and the overall structural stability of AIP systems. If the required quantity of water is admixed to the reaction mixture during the initial step of AIPs synthesis the resulting amorphous aluminosilicate matrix undergoes extensive crystallization (zeolitization). On the other hand, if the amount of water is added to the reaction mixture during the last step of the preparation procedure, the inorganic matrix exhibits long-term stability without any structural defects. To find the structural reasons of the observed behavior a combination of traditional solid state NMR (1H and 29Si MAS NMR, 29Si CP/MAS NMR, 29Si inverse-T1-filtered NMR), XRPD and TGA measurements were used. The applied experiments revealed that the structural stability of AIPs can be attributed to the tight binding of water molecules into the inorganic matrix. The structural stability of the prepared amorphous AIP systems thus seems to be affected by the extent of hydration i.e. the strength of binding water into the inorganic framework

The atomic-level structure of bandgap engineered double perovskite alloys Cs2AgIn1-xFexCl6

Although lead-free halide double perovskites are considered as promising alternatives to lead halide perovskites for optoelectronic applications, state-of-the-art double perovskites are limited by their large bandgap. The doping/alloying strategy, key to bandgap engineering in traditional semiconductors, has also been employed to tune the bandgap of halide double perovskites. However, this strategy has yet to generate new double perovskites with suitable bandgaps for practical applications, partially due to the lack of fundamental understanding of how the doping/alloying affects the atomic-level structure. Here, we take the benchmark double perovskite Cs2AgInCl6 as an example to reveal the atomic-level structure of double perovskite alloys (DPAs) Cs2AgIn1-xFexCl6 (x = 0-1) by employing solid-state nuclear magnetic resonance (ssNMR). The presence of paramagnetic alloying ions (e.g. Fe3+ in this case) in double perovskites makes it possible to investigate the nuclear relaxation times, providing a straightforward approach to understand the distribution of paramagnetic alloying ions. Our results indicate that paramagnetic Fe3+ replaces diamagnetic In3+ in the Cs2AgInCl6 lattice with the formation of [FeCl6](3-)center dot[AgCl6](5-) domains, which show different sizes and distribution modes in different alloying ratios. This work provides new insights into the atomic-level structure of bandgap engineered DPAs, which is of critical significance in developing efficient optoelectronic/spintronic devices.Funding Agencies|Knut and Alice Wallenberg FoundationKnut &amp; Alice Wallenberg Foundation; Swedish Energy AgencySwedish Energy Agency [2018-004357]; VR Starting Grant [2019-05279]; Carl Tryggers Stiftelse; Olle Engkvist Byggmastare Stiftelse; STINT grant [CH2018-7655]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [61704078]; Grant Agency of the Czech RepublicGrant Agency of the Czech Republic [GA19-05259S]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; China Scholarship Council (CSC)China Scholarship Council</p

Waste Brick Dust as Potential Sorbent of Lead and Cesium from Contaminated Water

Adsorption properties of waste brick dust (WBD) were studied by the removing of PbII and CsI from an aqueous system. For adsorption experiments, 0.1 M and 0.5 M aqueous solutions of Cs+ and Pb2+ and two WBD (Libochovice&#8212;LB, and Tyn nad Vltavou&#8212;TN) in the fraction below 125 &#181;m were used. The structural and surface properties of WBD were characterized by X-ray diffraction (XRD) in combination with solid-state nuclear magnetic resonance (NMR), supplemented by scanning electron microscopy (SEM), specific surface area (SBET), total pore volume and zero point of charge (pHZPC). LB was a more amorphous material showing a better adsorption condition than that of TN. The adsorption process indicated better results for Pb2+, due to the inner-sphere surface complexation in all Pb2+ systems, supported by the formation of insoluble Pb(OH)2 precipitation on the sorbent surface. A weak adsorption of Cs+ on WBD corresponded to the non-Langmuir adsorption run followed by the outer-sphere surface complexation. The leachability of Pb2+ from saturated WBDs varied from 0.001% to 0.3%, while in the case of Cs+, 4% to 12% of the initial amount was leached. Both LB and TN met the standards for PbII adsorption, yet completely failed for any CsI removal from water systems