Recent Submissions

  • Metal Halide Perovskites for Solar-to-Chemical Fuel Conversion

    Chen, Jie; Dong, Chunwei; Idriss, Hicham; Mohammed, Omar F.; Bakr, Osman (Advanced Energy Materials, Wiley, 2019-10-16) [Article]
    This review article presents and discusses the recent progress made in the stabilization, protection, improvement, and design of halide perovskite-based photocatalysts, photoelectrodes, and devices for solar-to-chemical fuel conversion. With the target of water splitting, hydrogen iodide splitting, and CO2 reduction reactions, the strategies established for halide perovskites used in photocatalytic particle-suspension systems, photoelectrode thin-film systems, and photovoltaic-(photo)electrocatalysis tandem systems are organized and introduced. Moreover, recent achievements in discovering new and stable halide perovskite materials, developing protective and functional shells and layers, designing proper reaction solution systems, and tandem device configurations are emphasized and discussed. Perspectives on the future design of halide perovskite materials and devices for solar-to-chemical fuel conversion are provided. This review may serve as a guide for researchers interested in utilizing halide perovskite materials for solar-to-chemical fuel conversion.
  • High-speed colour-converting photodetector with all-inorganic CsPbBr3 perovskite nanocrystals for ultraviolet light communication

    Kang, Chun Hong; Dursun, Ibrahim; Liu, Guangyu; Sinatra, Lutfan; Sun, Xiaobin; Kong, Meiwei; Pan, Jun; Maity, Partha; Ooi, Ee-Ning; Ng, Tien Khee; Mohammed, Omar F.; Bakr, Osman; Ooi, Boon S. (Light: Science & Applications, Springer Science and Business Media LLC, 2019-10-16) [Article]
    Optical wireless communication (OWC) using the ultra-broad spectrum of the visible-to-ultraviolet (UV) wavelength region remains a vital field of research for mitigating the saturated bandwidth of radio-frequency (RF) communication. However, the lack of an efficient UV photodetection methodology hinders the development of UV-based communication. The key technological impediment is related to the low UV-photon absorption in existing silicon photodetectors, which offer low-cost and mature platforms. To address this technology gap, we report a hybrid Si-based photodetection scheme by incorporating CsPbBr3 perovskite nanocrystals (NCs) with a high photoluminescence quantum yield (PLQY) and a fast photoluminescence (PL) decay time as a UV-to-visible colour-converting layer for high-speed solar-blind UV communication. The facile formation of drop-cast CsPbBr3 perovskite NCs leads to a high PLQY of up to ~73% and strong absorption in the UV region. With the addition of the NC layer, a nearly threefold improvement in the responsivity and an increase of ~25% in the external quantum efficiency (EQE) of the solar-blind region compared to a commercial silicon-based photodetector were observed. Moreover, time-resolved photoluminescence measurements demonstrated a decay time of 4.5 ns under a 372-nm UV excitation source, thus elucidating the potential of this layer as a fast colour-converting layer. A high data rate of up to 34 Mbps in solar-blind communication was achieved using the hybrid CsPbBr3–silicon photodetection scheme in conjunction with a 278-nm UVC light-emitting diode (LED). These findings demonstrate the feasibility of an integrated high-speed photoreceiver design of a composition-tuneable perovskite-based phosphor and a low-cost silicon-based photodetector for UV communication.
  • Blind prediction of homo- and hetero- protein complexes: The CASP13-CAPRI experiment.

    Lensink, Marc F.; Brysbaert, Guillaume; Nadzirin, Nurul; Velankar, Sameer; Chaleil, Raphaël A G; Gerguri, Tereza; Bates, Paul A; Laine, Elodie; Carbone, Alessandra; Grudinin, Sergei; Kong, Ren; Liu, Ran-Ran; Xu, Xi-Ming; Shi, Hang; Chang, Shan; Eisenstein, Miriam; Karczynska, Agnieszka; Czaplewski, Cezary; Lubecka, Emilia; Lipska, Agnieszka; Krupa, Paweł; Mozolewska, Magdalena; Golon, Łukasz; Samsonov, Sergey; Liwo, Adam; Crivelli, Silvia; Pagès, Guillaume; Karasikov, Mikhail; Kadukova, Maria; Yan, Yumeng; Huang, Sheng-You; Rosell, Mireia; Rodríguez-Lumbreras, Luis Angel; Romero-Durana, Miguel; Díaz-Bueno, Lucía; Fernandez-Recio, Juan; Christoffer, Charles; Terashi, Genki; Shin, Woong-Hee; Aderinwale, Tunde; Raghavendra Maddhuri Venkata Subraman, Sai; Kihara, Daisuke; Kozakov, Dima; Vajda, Sandor; Porter, Kathyn; Padhorny, Dzmitry; Desta, Israel; Beglov, Dmitri; Ignatov, Mikhail; Kotelnikov, Sergey; Moal, Iain H; Ritchie, David W; Chauvot de Beauchêne, Isaure; Maigret, Bernard; Devignes, Marie-Dominique; Echartea, Maria Elisa Ruiz; Barradas Bautista, Didier; Cao, Zhen; Cavallo, Luigi; Oliva, Romina; Cao, Yue; Shen, Yang; Baek, Minkyung; Park, Taeyong; Woo, Hyeonuk; Seok, Chaok; Braitbard, Merav; Bitton, Lirane; Scheidman-Duhovny, Dina; DapkŪnas, Justas; Olechnovič, Kliment; Venclovas, Česlovas; Kundrotas, Petras J; Belkin, Saveliy; Chakravarty, Devlina; Badal, Varsha D; Vakser, Ilya A; Vreven, Thom; Vangaveti, Sweta; Borrman, Tyler; Weng, Zhiping; Guest, Johnathan D; Gowthaman, Ragul; Pierce, Brian G; Xu, Xianjin; Duan, Rui; Qiu, Liming; Hou, Jie; Ryan Merideth, Benjamin; Ma, Zhiwei; Cheng, Jianlin; Zou, Xiaoqin; Koukos, Panos I; Roel-Touris, Jorge; Ambrosetti, Francesco; Geng, Cunliang; Schaarschmidt, Jörg; Trellet, Mikael E; Melquiond, Adrien S J; Xue, Li; Jiménez-García, Brian; van Noort, Charlotte W; Honorato, Rodrigo V; Bonvin, Alexandre M.J.J.; Wodak, Shoshana J (Proteins, Wiley, 2019-10-16) [Article]
    We present the results for CAPRI Round 46, the 3rd joint CASP-CAPRI protein assembly prediction challenge. The Round comprised a total of 20 targets including 14 homo-oligomers and 6 hetero-complexes. Eight of the homo-oligomer targets and one hetero-dimer comprised proteins that could be readily modeled using templates from the Protein Data Bank, often available for the full assembly. The remaining 11 targets comprised 5 homo-dimers, 3 hetero-dimers and two higher-order assemblies. These were more difficult to model, as their prediction mainly involved 'ab-initio' docking of subunit models derived from distantly related templates. A total of ~30 CAPRI groups, including 9 automatic servers, submitted on average ~2000 models per target. About 17 groups participated in the CAPRI scoring rounds, offered for most targets, submitting ~170 models per target. The prediction performance, measured by the fraction of models of acceptable quality or higher submitted across all predictors groups, was very good to excellent for the 9 easy targets. Poorer performance was achieved by predictors for the 11 difficult targets, with medium and high quality models submitted for only 3 of these targets. A similar performance 'gap' was displayed by scorer groups, highlighting yet again the unmet challenge of modeling the conformational changes of the protein components that occur upon binding or that must be accounted for in template-based modeling. Our analysis also indicates that residues in binding interfaces were less well predicted in this set of targets than in previous Rounds, providing useful insights for directions of future improvements. This article is protected by copyright. All rights reserved.
  • The Comparison between Single Atom Catalysis and Surface Organometallic Catalysis

    Samantaray, Manoja; D’Elia, Valerio; Pump, Eva; Falivene, Laura; Harb, Moussab; Ould-Chikh, Samy; Cavallo, Luigi; Basset, Jean-Marie (Chemical Reviews, American Chemical Society (ACS), 2019-10-15) [Article]
    Single atom catalysis (SAC) is a recent discipline of heterogeneous catalysis for which a single atom on a surface is able to carry out various catalytic reactions. A kind of revolution in heterogeneous catalysis by metals for which it was assumed that specific sites or defects of a nanoparticle were necessary to activate substrates in catalytic reactions. In another extreme of the spectrum, surface organometallic chemistry (SOMC), and, by extension, surface organometallic catalysis (SOMCat), have demonstrated that single atoms on a surface, but this time with specific ligands, could lead to a more predictive approach in heterogeneous catalysis. The predictive character of SOMCat was just the result of intuitive mechanisms derived from the elementary steps of molecular chemistry. This review article will compare the aspects of single atom catalysis and surface organometallic catalysis by considering several specific catalytic reactions, some of which exist for both fields, whereas others might see mutual overlap in the future. After a definition of both domains, a detailed approach of the methods, mostly modeling and spectroscopy, will be followed by a detailed analysis of catalytic reactions: hydrogenation, dehydrogenation, hydrogenolysis, oxidative dehydrogenation, alkane and cycloalkane metathesis, methane activation, metathetic oxidation, CO2 activation to cyclic carbonates, imine metathesis, and selective catalytic reduction (SCR) reactions. A prospective resulting from present knowledge is showing the emergence of a new discipline from the overlap between the two areas.
  • Assessing the Range of Validity of Current Tube Models through Analysis of a Comprehensive Set of Star–Linear 1,4-Polybutadiene Polymer Blends

    Hall, Ryan; Desai, Priyanka S.; Kang, Beom-Goo; Huang, Qifan; Lee, Sanghoon; Chang, Taihyun; Venerus, David C.; Mays, Jimmy; Ntetsikas, Konstantinos; Polymeropoulos, George; Hadjichristidis, Nikolaos; Larson, Ronald G. (Macromolecules, American Chemical Society (ACS), 2019-10-10) [Article]
    We blend newly synthesized nearly monodisperse four-arm star 1,4-polybutadienes with various well-entangled linear polymers, confirming the conclusions in Desai et al. [ Macromolecules201649 (13)49644977] that advanced tube models, namely, the hierarchical 3.0 and branch-on-branch models [Wang, Z.; J. Rheol.201054 (2)223260], fail to predict the linear rheological data when the pure linear polymers have shorter relaxation times, but within 3–4 orders of magnitude of the star polymer. However, when the linear polymer has a longer relaxation time than the star, our new work, surprisingly, finds that non-monotonic dependence of terminal relaxation behavior on composition is both observed experimentally and captured by the models. Combined with previous data from the literature, we present results from over 50 1,4-polybutadiene star–linear blends, suitable for thorough testing of rheological models of entangled polymers.
  • New Insight on the Role of Electrolyte Additives in Rechargeable Lithium Ion Batteries

    Ming, Jun; Cao, Zhen; Wu, Yingqiang; Wahyudi, Wandi; Wang, Wenxi; Guo, Xianrong; Cavallo, Luigi; Hwang, Jang-Yeon; Shamim, Atif; Li, Lain-Jong; Sun, Yang-Kook; Alshareef, Husam N. (ACS Energy Letters, American Chemical Society (ACS), 2019-10-08) [Article]
    Solid electrolyte interphase (SEI)-forming agents such as vinylene carbonate, sulfone, and cyclic sulfate are commonly believed to be film-forming additives in lithium-ion batteries that help to enhance graphite anode stability. However, we find that the film-forming effect and the resultant SEI may not be the only reasons for the enhanced graphite stability. This is because the as-formed SEI cannot inhibit Li+–solvent co-intercalation once the additive is removed from the electrolyte. Instead, we show that the Li+ solvation structure, which is modified by these additives, plays a critical role in achieving reversible Li+ (de)intercalation within graphite. This discovery is confirmed in both carbonate and ether-based electrolytes. We show that the problem of graphite exfoliation caused by Li+–solvent co-intercalation can be mitigated by adding ethene sulfate to tune the Li+ coordination structure. This work brings new insight into the role of additives in electrolytes, expanding the prevailing thinking over the past 2 decades. In addition, this finding can guide the design of more versatile electrolytes for advanced rechargeable metal-ion batteries.
  • Ultralong cycle stability of aqueous zinc-ion batteries with zinc vanadium oxide cathodes

    Wang, Lulu; Huang, Kuo-Wei; Chen, Jitao; Zheng, Junrong (Science Advances, American Association for the Advancement of Science (AAAS), 2019-10-04) [Article]
    Rechargeable aqueous zinc-ion batteries are promising candidates for large-scale energy storage but are plagued by the lack of cathode materials with both excellent rate capability and adequate cycle life span. We overcome this barrier by designing a novel hierarchically porous structure of Zn-vanadium oxide material. This Zn0.3V2O5·1.5H2O cathode delivers a high specific capacity of 426 mA·h g−1 at 0.2 A g−1 and exhibits an unprecedented superlong-term cyclic stability with a capacity retention of 96% over 20,000 cycles at 10 A g−1. Its electrochemical mechanism is elucidated. The lattice contraction induced by zinc intercalation and the expansion caused by hydronium intercalation cancel each other and allow the lattice to remain constant during charge/discharge, favoring cyclic stability. The hierarchically porous structure provides abundant contact with electrolyte, shortens ion diffusion path, and provides cushion for relieving strain generated during electrochemical processes, facilitating both fast kinetics and long-term stability.
  • Barcoding Amino Acids for Mutation Screening in Amyloid Beta Peptides

    Hoang, Phuong Mai; Khashab, Niveen M. (Small Methods, Wiley, 2019-10-04) [Article]
    Amino acid (AA) substitutions are directly correlated with specific pathologies such as Alzheimer's disease, making their rapid screening and detection critical to treatment and scientific study. A proof-of-concept implementation of the label-free and noninvasive Raman spectroscopy technique for the detection of AA substitutions in primary peptide fragments is demonstrated. By encoding the Raman “fingerprint” of individual AAs into binary formats called optical identification tags (OITs), a library of identifiers is created, which can then be used for detecting mutations. When the recorded Raman signal is enhanced by using surface-enhanced Raman scattering substrate, the mutation screening strategy can detect a single point missense mutation in an 11-AA peptide fragment of amyloid beta Aβ(25–35) and a frameshift mutation in a 42-AA fragment Aβ(1–42) down to picomolar concentrations. The combination of high sensitivity and simple operation makes the use of OITs a promising approach for high-throughput automated screening.
  • Enhanced catalyst performance through compartmentalization exemplified by colloidal L-proline modified microgel catalysts

    Kleinschmidt, Denise; Fernandes, Marta Sofia; Mork, Matthias; Meyer, Anna Astrid; Krischel, Julian; Anakhov, Mikhail V.; Gumerov, Rustam A.; Potemkin, Igor I.; Rueping, Magnus; Pich, Andrij (Journal of Colloid and Interface Science, Elsevier BV, 2019-10-04) [Article]
    Exploring and controlling chemical reactions in compartments opens new platforms for designing bioinspired catalysts and energy-autonomous systems. Aqueous polymer networks or hydrogels serve as a perfect model for biological tissues, allowing systematic investigations of chemical transformations in compartments. Herein, we report the synthesis of a versatile, colloidal microgel catalyst containing covalently bound L-proline as an organocatalyst. The key finding of our work is that the catalytic activity can be tuned by adjusting the distribution of the organocatalyst in the microgel network as well as the properties of the solvent. We demonstrate that L-proline groups integrated into microgels enable the reaction of 4-nitrobenzaldehyde and cyclohexanone in a heterogeneous reaction mixture in which free L-proline is not active. By controlling the localization of the L-proline groups within the microgel network (core or corona), the rate of the aldol reaction in homogenous and heterogeneous reaction mixtures can be modulated. Furthermore, microgels with covalently attached catalysts can be recycled and reused in sequential catalytic runs without deterioration of the catalyst performance in terms of activity and selectivity. The internal structure of the microgel in heterogeneous reaction mixtures was studied by computer simulations.
  • MAPbI3 Single Crystals Free from Hole-Trapping Centers for Enhanced Photodetectivity

    Yang, Chen; El Demellawi, Jehad K.; Yin, Jun; Velusamy, Dhinesh; Emwas, Abdul-Hamid M.; El-Zohry, Ahmed M.; Gereige, Issam; AlSaggaf, Ahmed; Bakr, Osman; Alshareef, Husam N.; Mohammed, Omar F. (ACS Energy Letters, American Chemical Society (ACS), 2019-10-01) [Article]
    Perovskite single crystals (PSCs) are considered the next breakthrough in optoelectronics research due to their free-grain boundary and much lower density of trap states compared to those of their polycrystalline counterparts. However, the inevitable formation of triiodide-based intrinsic defects during high-temperature crystal growth is one of the major challenges impeding the further development of optoelectronic devices based on PSCs. Here, we not only identified the existence of these triiodide ions as hole-trapping centers and their tremendous negative impact on the performance of PSCs, but more importantly, we used a reduction treatment to prevent their formation during crystal growth. The removal of such defect centers resulted in much higher charge carrier mobility and longer carrier lifetime than the untreated counterparts, leading to enhanced photodetection properties. The I3–-free MAPbI3 single crystal (MSC) devices consistently generated a more than 100 times higher photocurrent than that generated by I3–-rich devices under the same light intensity.
  • 17% Efficient Organic Solar Cells Based on Liquid Exfoliated WS2 as a Replacement for PEDOT:PSS

    Lin, Yuanbao; Adilbekova, Begimai; Firdaus, Yuliar; Yengel, Emre; Faber, Hendrik; Sajjad, Muhammad; Zheng, Xiaopeng; Yarali, Emre; Seitkhan, Akmaral; Bakr, Osman; El Labban, Abdulrahman; Schwingenschlögl, Udo; Tung, Vincent; McCulloch, Iain; Laquai, Frédéric; Anthopoulos, Thomas D. (Advanced Materials, Wiley, 2019-10-01) [Article]
    The application of liquid-exfoliated 2D transition metal disulfides (TMDs) as the hole transport layers (HTLs) in nonfullerene-based organic solar cells is reported. It is shown that solution processing of few-layer WS2 or MoS2 suspensions directly onto transparent indium tin oxide (ITO) electrodes changes their work function without the need for any further treatment. HTLs comprising WS2 are found to exhibit higher uniformity on ITO than those of MoS2 and consistently yield solar cells with superior power conversion efficiency (PCE), improved fill factor (FF), enhanced short-circuit current (JSC), and lower series resistance than devices based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and MoS2. Cells based on the ternary bulk-heterojunction PBDB-T-2F:Y6:PC71BM with WS2 as the HTL exhibit the highest PCE of 17%, with an FF of 78%, open-circuit voltage of 0.84 V, and a JSC of 26 mA cm−2. Analysis of the cells' optical and carrier recombination characteristics indicates that the enhanced performance is most likely attributed to a combination of favorable photonic structure and reduced bimolecular recombination losses in WS2-based cells. The achieved PCE is the highest reported to date for organic solar cells comprised of 2D charge transport interlayers and highlights the potential of TMDs as inexpensive HTLs for high-efficiency organic photovoltaics.
  • Iodine-transfer polymerization and CuAAC “click” chemistry: A versatile approach toward poly(vinylidene fluoride)-based amphiphilic triblock terpolymers

    Patil, Yogesh Raghunath; Zapsas, Georgios; Gnanou, Yves; Hadjichristidis, Nikolaos (Journal of Polymer Science Part A: Polymer Chemistry, Wiley, 2019-10-01) [Article]
    This study presents the synthesis and properties of linear PVDF-based amphiphilic triblock terpolymers with PS and PEO, [PVDF-b-PS-b-PEO], by adopting a procedure that involves: (a) iodine-transfer polymerization (ITP) of VDF with 1-iodoperfluorohexane (C6F13I) serving as chain-transfer agent (CTA) to afford C6F13-PVDF-I, (b) ITP of styrene with the C6F13-PVDF-I macromolecular-CTA to obtain C6F13-PVDF-b-PS-I diblock copolymer, (c) end-group exchange from iodo- to azido-group by nucleophilic substitution reaction with NaN3, and (d) copper-catalyzed azide-alkyne cycloaddition (CuAAC) with alkyne-terminated PEO to achieve C6F13-PVDF-b-PS-b-PEO triblock terpolymers. The 1H and 19F NMR spectroscopy confirmed the presence of all blocks, while gel permeation chromatography traces showed the living nature of ITP technique. The self-assembly of these terpolymers was investigated in films (atomic force microscopy and DSC), as well as in aqueous and organic solvents (DLS). The analysis of crystalline phases based on the FTIR spectroscopy indicated the conversion of PVDF α-phase into α + β-phases and β + γ-phases upon the incorporation of PS and PEO blocks, respectively. The synthesized amphiphilic copolymers were evaluated (fluorescence spectroscopy) as carriers of small hydrophobic molecules in water. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019
  • A new tricrystalline triblock terpolymer by combining polyhomologation and ring-opening polymerization. synthesis and thermal properties

    Ladelta, Viko; Zapsas, Georgios; Gnanou, Yves; Hadjichristidis, Nikolaos (Journal of Polymer Science Part A: Polymer Chemistry, Wiley, 2019-10-01) [Article]
    New tricrystalline triblock terpolymers, polyethylene-block-poly(ε-caprolactone)-block-poly(L-lactide) (PE-b-PCL-b-PLLA), were synthesized by ROP of ε-caprolactone (CL) and L-lactide (LLA) from linear ω-hydroxyl polyethylene (PE-OH) macroinitiators. The linear PE-OH macroinitiators were prepared by C1 polymerization of methylsulfoxonium methylide (polyhomologation). Tin(II) 2-ethylhexanoate was used as the catalyst for the sequential ROP of CL and LLA in one-pot polymerization at 85 °C in toluene (PE-OH macroinitiators are soluble in toluene at 80 °C). 1H NMR spectra confirmed the formation of PE-b-PCL-b-PLLA triblock terpolymers through the appearance of the characteristic proton peaks of each block. GPC traces showed the increase in the number average molecular weight from PE-OH macroinitiator to PE-b-PCL, and PE-b-PCL-b-PLLA corroborating the successful synthesis. The existence of three crystalline blocks was proved by DSC and XRD spectroscopy. © 2019 The Authors. Journal of Polymer Science Part A: Polymer Chemistry published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019
  • Use of the Phen-NaDPO:Sn(SCN) 2 Blend as Electron Transport Layer Results to Consistent Efficiency Improvements in Organic and Hybrid Perovskite Solar Cells

    Seitkhan, Akmaral; Neophytou, Marios; Kirkus, Mindaugas; Abou-Hamad, Edy; Hedhili, Mohamed N.; Yengel, Emre; Firdaus, Yuliar; Faber, Hendrik; Lin, Yuanbao; Tsetseris, Leonidas; McCulloch, Iain; Anthopoulos, Thomas D. (Advanced Functional Materials, Wiley, 2019-09-27) [Article]
    A simple approach that enables a consistent enhancement of the electron extracting properties of the widely used small-molecule Phen-NaDPO and its application in organic solar cells (OSCs) is reported. It is shown that addition of minute amounts of the inorganic molecule Sn(SCN)2 into Phen-NaDPO improves both the electron transport and its film-forming properties. Use of Phen-NaDPO:Sn(SCN)2 blend as the electron transport layer (ETL) in binary PM6:IT-4F OSCs leads to a remarkable increase in the cells' power conversion efficiency (PCE) from 12.6% (Phen-NaDPO) to 13.5% (Phen-NaDPO:Sn(SCN)2). Combining the hybrid ETL with the best-in-class organic ternary PM6:Y6:PC70BM systems results to a similarly remarkable PCE increase from 14.2% (Phen-NaDPO) to 15.6% (Phen-NaDPO:Sn(SCN)2). The consistent PCE enhancement is attributed to reduced trap-assisted carrier recombination at the bulk-heterojunction/ETL interface due to the presence of new energy states formed upon chemical interaction of Phen-NaDPO with Sn(SCN)2. The versatility of this hybrid ETL is further demonstrated with its application in perovskite solar cells for which an increase in the PCE from 16.6% to 18.2% is also demonstrated.
  • Facile synthesis of poly(trimethylene carbonate) by alkali metal carboxylate-catalyzed ring-opening polymerization

    Takojima, Kaoru; Saito, Tatsuya; Vevert, Cedric; Ladelta, Viko; Bilalis, Panagiotis; Watanabe, Jun; Hatanaka, Shintaro; Konno, Takashi; Yamamoto, Takuya; Tajima, Kenji; Hadjichristidis, Nikolaos; Isono, Takuya; Satoh, Toshifumi (Polymer Journal, Springer Science and Business Media LLC, 2019-09-24) [Article]
    Alkali metal carboxylates, including sodium acetate, sodium benzoate, and sodium sorbate, which are all readily available and widely used as food additives, were found to promote the ring-opening polymerization (ROP) of trimethylene carbonate (TMC) to produce poly(trimethylene carbonate) (PTMC). The sodium acetate-catalyzed ROP of TMC proceeded in the presence of an alcohol initiator under solvent-free conditions at 70 °C, even at very low catalyst loadings of 0.01–0.0001 mol%. The controlled nature of this ROP system enabled the synthesis of PTMCs with predicted molecular weights ranging from 2400 to 11 700 g mol−1 and narrow dispersities (~1.23). Importantly, ROP is initiated by an alcohol initiator, allowing PTMC production with desired functional groups, such as azido, alkyne, and methacrylate groups, at the α-chain end. Furthermore, the poly(L-lactic acid)-b-PTMC-b-poly(L-lactic acid) triblock copolymer, a biodegradable thermoplastic elastomer, was successfully synthesized in one pot via the sodium acetate-catalyzed ring-opening block copolymerization of TMC and L-lactide with a 1,3-propanediol initiator.
  • Outstanding Challenges of Zero-Dimensional Perovskite Materials

    Mohammed, Omar F. (The Journal of Physical Chemistry Letters, American Chemical Society (ACS), 2019-09-19) [Article]
  • Halogen Vacancies Enable Ligand-Assisted Self-Assembly of Perovskite Quantum Dots into Nanowires.

    Pan, Jun; Li, Xiyan; Gong, Xiwen; Yin, Jun; Zhou, Dianli; Sinatra, Lutfan; Huang, Renwu; Liu, Jiakai; Chen, Jie; Dursun, Ibrahim; El-Zohry, Ahmed M.; Saidaminov, Makhsud I.; Sun, Hong-Tao; Mohammed, Omar F.; Ye, Changhui; Sargent, E.; Bakr, Osman (Angewandte Chemie (International ed. in English), Wiley, 2019-09-19) [Article]
    Interest has been growing in defects of halide perovskites in view of their intimate connection with key material optoelectronic properties. In perovskite quantum dots (PQDs), the influence of defects is even more apparent than in their bulk counterparts. By combining experiment and theory, we report herein a halide-vacancy-driven, ligand-directed self-assembly process of CsPbBr3 PQDs. With the assistance of oleic acid and didodecyldimethylammonium sulfide, surface-Br-vacancy-rich CsPbBr3 PQDs self-assemble into nanowires (NWs) that are 20-60 nm in width and several millimeters in length. The NWs exhibit a sharp photoluminescence profile (≈18 nm full-width at-half-maximum) that peaks at 525 nm. Our findings provide insight into the defect-correlated dynamics of PQDs and defect-assisted fabrication of perovskite materials and devices.
  • Generating Triple Crystalline Superstructures in Melt Miscible PEO-b-PCL-b-PLLA Triblock Terpolymers by Controlling Thermal History and Sequential Crystallization

    Palacios, Jordana K.; Liu, Guoming; Wang, Dujin; Hadjichristidis, Nikolaos; Müller, Alejandro J. (Macromolecular Chemistry and Physics, Wiley, 2019-09-11) [Article]
    The morphology, crystallization behavior, and properties of multi-crystalline polymer systems based on triple crystalline biodegradable PEO-b-PCL-b-PLLA triblock terpolymers are reviewed. The triblock terpolymers, with increasing poly(l-lactide) (PLLA) content, exhibit a triple crystalline nature. Upon cooling from melt, the PLLA block crystallizes first and templates the spherulitic morphology of the terpolymer. Then, the poly(ε-caprolactone) (PCL) block crystalizes and, finally, the poly(ethylene oxide) (PEO) block. These triblock terpolymers are melt miscible according to small angle X-ray scattering (SAXS) results. Thus, the crystallization of PCL and PEO blocks takes place within the interlamellar zones of the PLLA spherulites that are formed previously. Therefore, the lamellae of PLLA, PCL, and PEO exist side-by-side within a unique spherulite, constituting a novel triple crystalline superstructure. The theoretical analysis of SAXS curves implies that only one lamella of either PCL or PEO can occupy the interlamellar space in between two contiguous lamellae of PLLA. Several complex competitive effects such as plasticizing, nucleation, anti-plasticizing, and confinement take place during the isothermal crystallization of each block in the terpolymers. New results on how successive self-nucleation and annealing thermal treatment can be used as an additional suitable technique to properly separate the three crystalline phases in these triple crystalline triblock terpolymers are also included.
  • Ligand Effects in Pd-Catalyzed Intermolecular Alkyne Hydroarylations

    Voccia, Maria; Falivene, Laura; Cavallo, Luigi; Tubaro, Cristina; Biffis, Andrea; Caporaso, Lucia (Organometallics, American Chemical Society (ACS), 2019-09-11) [Article]
    The use of palladium(II) catalysts for the synthesis of aryl alkenes by addition of aromatic C–H bonds to alkynes has received a great interest in the literature. The mechanistic features of the reaction have been largely discussed, but no systematic study has been reported so far, particularly for what concerns the role of ligands. In this work, we performed a detailed theoretical study in order to fill this gap. To this extent, three different systems have been considered, with the aim to emphasize how the steric and electronic metal environment affects the catalytic activity and, most notably, steers the reaction selectivity toward the two main products of single and double alkyne insertion into the aromatic C–H bond. Moreover, given the crucial role of the acid media, two acids have been considered, namely, trifluoroacetic acid and tetrafluoroboric acid, to understand the effect of the acid strength and coordinative power on the competition between the different pathways.
  • Gas sensitivity amplification of interdigitated chemocapacitors through etching

    Oikonomou, P.; Botsialas, A.; Papanikolaou, N.; Kazas, I.; Ntetsikas, Konstantinos; Polymeropoulos, Georgios; Hadjichristidis, Nikolaos; Sanopoulou, M.; Raptis, I. (IEEE Sensors Journal, Institute of Electrical and Electronics Engineers (IEEE), 2019-09-02) [Article]
    In polymer coated planar Inter Digitated Electrodes (IDEs), the gas sensing sensitivity is much lower than the sensitivity of parallel plate capacitors. Here, we introduce a simple patterning step for the modification of the geometry of the dielectric substrate of the planar IDEs, and increase of the contribution of the sensitive layer to the output signal. The proposed methodology is investigated through simulation and verified by experimental data. Polymer coated IDEs with different dimensions of spatial wavelength were studied experimentally upon exposure to analytes of varying polarity. The sensing performance of the fabricated structures compare very well with theoretically estimated values obtained through finite element simulations. The maximum performance gain is also calculated by simulation demonstrating the potential of the technology.

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