Now showing items 1-20 of 2403

    • Crystallization and Morphology of Triple Crystalline Polyethylene-b-poly(ethylene oxide)-b-poly(ε-caprolactone) PE-b-PEO-b-PCL Triblock Terpolymers

      Matxinandiarena, Eider; Múgica, Agurtzane; Zubitur, Manuela; Ladelta, Viko; Zapsas, Georgios; Cavallo, Dario; Hadjichristidis, Nikos; Müller, Alejandro J. (Polymers, MDPI AG, 2021-09-16) [Article]
      The morphology and crystallization behavior of two triblock terpolymers of polymethylene, equivalent to polyethylene (PE), poly (ethylene oxide) (PEO), and poly (ε-caprolactone) (PCL) are studied: PE227.1-b-PEO4615.1-b-PCL3210.4 (T1) and PE379.5-b-PEO348.8-b-PCL297.6 (T2) (superscripts give number average molecular weights in kg/mol and subscripts composition in wt %). The three blocks are potentially crystallizable, and the triple crystalline nature of the samples is investigated. Polyhomologation (C1 polymerization), ring-opening polymerization, and catalyst-switch strategies were combined to synthesize the triblock terpolymers. In addition, the corresponding PE-b-PEO diblock copolymers and PE homopolymers were also analyzed. The crystallization sequence of the blocks was determined via three independent but complementary techniques: differential scanning calorimetry (DSC), in situ SAXS/WAXS (small angle X-ray scattering/wide angle X-ray scattering), and polarized light optical microscopy (PLOM). The two terpolymers (T1 and T2) are weakly phase segregated in the melt according to SAXS. DSC and WAXS results demonstrate that in both triblock terpolymers the crystallization process starts with the PE block, continues with the PCL block, and ends with the PEO block. Hence triple crystalline materials are obtained. The crystallization of the PCL and the PEO block is coincident (i.e., it overlaps); however, WAXS and PLOM experiments can identify both transitions. In addition, PLOM shows a spherulitic morphology for the PE homopolymer and the T1 precursor diblock copolymer, while the other systems appear as non-spherulitic or microspherulitic at the last stage of the crystallization process. The complicated crystallization of tricrystalline triblock terpolymers can only be fully grasped when DSC, WAXS, and PLOM experiments are combined. This knowledge is fundamental to tailor the properties of these complex but fascinating materials.
    • Interfacial Model Deciphering High-Voltage Electrolytes for High Energy Density, High Safety, and Fast-Charging Lithium-Ion Batteries

      Zou, Yeguo; Cao, Zhen; Zhang, Junli; Wahyudi, Wandi; Wu, Yingqiang; Liu, Gang; Li, Qian; Cheng, Haoran; Zhang, Dongyu; Park, Geon-Tae; Cavallo, Luigi; Anthopoulos, Thomas D.; Wang, Limin; Sun, Yang-Kook; Ming, Jun (Advanced Materials, Wiley, 2021-09-12) [Article]
      High-voltage lithium-ion batteries (LIBs) enabled by high-voltage electrolytes can effectively boost energy density and power density, which are critical requirements to achieve long travel distances, fast-charging, and reliable safety performance for electric vehicles. However, operating these batteries beyond the typical conditions of LIBs (4.3 V vs Li/Li+) leads to severe electrolyte decomposition, while interfacial side reactions remain elusive. These critical issues have become a bottleneck for developing electrolytes for applications in extreme conditions. Herein, an additive-free electrolyte is presented that affords high stability at high voltage (4.5 V vs Li/Li+), lithium-dendrite-free features upon fast-charging operations (e.g., 162 mAh g−1 at 3 C), and superior long-term battery performance at low temperature. More importantly, a new solvation structure-related interfacial model is presented, incorporating molecular-scale interactions between the lithium-ion, anion, and solvents at the electrolyte–electrode interfaces to help interpret battery performance. This report is a pioneering study that explores the dynamic mutual-interaction interfacial behaviors on the lithium layered oxide cathode and graphite anode simultaneously in the battery. This interfacial model enables new insights into electrode performances that differ from the known solid electrolyte interphase approach to be revealed, and sets new guidelines for the design of versatile electrolytes for metal-ion batteries.
    • Thermo-Responsive Membranes from Blends of PVDF and PNIPAM-b-PVDF Block Copolymers with Linear and Star Architectures

      Algarni, Fatimah; Musteata, Valentina-Elena; Falca, Gheorghe; Chisca, Stefan; Hadjichristidis, Nikos; Nunes, Suzana Pereira (Macromolecules, American Chemical Society (ACS), 2021-09-10) [Article]
      We report the synthesis of poly(n-isopropylacrylamide)-b-poly(vinylidene fluoride), (PNIPAM-b-PVDF), copolymers with linear and star structures, as well as the self-assembly and fabrication of thermo-responsive membranes from blends of these block copolymers and a linear PVDF homopolymer. The synthesis was achieved by reversible addition–fragmentation chain-transfer sequential copolymerization using mono- or multifunctional transfer agents. The self-assembly in bulk and selective solvents was investigated. The PVDF blocks are crystallizable and hydrophobic and the PNIPAM thermo-responsive in water. The morphology is dominated by the breakout crystallization of the PVDF block. Nanoporous membranes were fabricated by non-solvent-induced phase-separation method. The membranes revealed a macroscale zig–zag morphology, which is dependent on the block copolymer architecture. Due to the presence of PNIPAM, these membranes exhibited thermo-responsive behavior with water permeability and rejection alternately varying with the operating temperature, which is reversible in multiple heating–cooling cycles.
    • Illuminating the Intrinsic Effect of Water Co-feeding on Methane Dehydroaromatization: A Comprehensive Study

      Caglayan, Mustafa; Paioni, Alessandra Lucini; Dereli, Busra; Shterk, Genrikh; Hita, Idoia; Abou-Hamad, Edy; Pustovarenko, Alexey; Emwas, Abdul-Hamid M.; Dikhtiarenko, Alla; Castaño, Pedro; Cavallo, Luigi; Baldus, Marc; Chowdhury, Abhishek Dutta; Gascon, Jorge (ACS Catalysis, American Chemical Society (ACS), 2021-09-07) [Article]
      Among all catalytic natural gas valorization processes, methane dehydroaromatization (MDA) still has a great potential to be utilized at an industrial level. Although the use of Mo/H-ZSM-5 as an MDA catalyst was first reported almost three decades ago, the process is yet to be industrialized, because of its inherent challenges. In order to improve the overall catalytic performance and lifetime, the co-feeding of water constitutes a promising option, because of its abundance and nontoxicity. Although water’s (limited) positive influence on catalyst lifetime has earlier been exhibited, the exact course of action (like mechanism or the water effect on active sites) is yet to be established. To bridge this knowledge gap, in this work, we have performed an in-depth investigation to elucidate the effects of water co-feeding over a well-dispersed Mo/H-ZSM-5 catalyst by using an array of advanced characterization techniques (nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry–temperature-programmed oxidation/mass spectroscopy (TG-TPO/MS), scanning transmission electron microscopy (STEM), N2 physisorption, Raman spectroscopy, inductively coupled plasma–optical emission spectroscopy (ICP-OES)). Our results demonstrate that the addition of water results in the occurrence of steam reforming (of both coke and methane) in parallel to MDA. Moreover, the presence of water affects the reducibility of Mo sites, as corroborated with computational analysis to examine the state and locality of Mo sites under various water levels and transformation of the catalyst structure during deactivation. We anticipate that our comprehensive study of the structure–function relationship on Mo/H-ZSM-5 under humid MDA conditions will be beneficial for the development of future methane valorization technologies.
    • Linked Nickel Oxide/Perovskite Interface Passivation for High-Performance Textured Monolithic Tandem Solar Cells

      Zhumagali, Shynggys; Isikgor, Furkan Halis; Maity, Partha; Yin, Jun; Ugur, Esma; de Bastiani, Michele; Subbiah, Anand Selvin; Mirabelli, Alessandro James; Azmi, Randi; Harrison, George T.; Troughton, Joel; Aydin, Erkan; Liu, Jiang; Allen, Thomas; Rehman, Atteq Ur; Baran, Derya; Mohammed, Omar F.; De Wolf, Stefaan (Advanced Energy Materials, Wiley, 2021-09-05) [Article]
      Sputtered nickel oxide (NiOx) is an attractive hole-transport layer for efficient, stable, and large-area p-i-n metal-halide perovskite solar cells (PSCs). However, surface traps and undesirable chemical reactions at the NiOx/perovskite interface are limiting the performance of NiOx-based PSCs. To address these issues simultaneously, an efficient NiOx/perovskite interface passivation strategy by using an organometallic dye molecule (N719) is reported. This molecule concurrently passivates NiOx and perovskite surface traps, and facilitates charge transport. Consequently, the power conversion efficiency (PCE) of single-junction p-i-n PSCs increases from 17.3% to 20.4% (the highest reported value for sputtered-NiOx based PSCs). Notably, the N719 molecule self-anchors and conformally covers NiOx films deposited on complex surfaces. This enables highly efficient textured monolithic p-i-n perovskite/silicon tandem solar cells, reaching PCEs up to 26.2% (23.5% without dye passivation) with a high processing yield. The N719 layer also forms a barrier that prevents undesirable chemical reactions at the NiOx/perovskite interface, significantly improving device stability. These findings provide critical insights for improved passivation of the NiOx/perovskite interface, and the fabrication of highly efficient, robust, and large-area perovskite-based optoelectronic devices.
    • Sustainable and Eco-Friendly Coral Restoration through 3D Printing and Fabrication

      Albalawi, Hamed I.; Khan, Zainab N.; Valle-Pérez, Alexander U.; Kahin, Kowther M.; Hountondji, Maria; Alwazani, Hibatallah; Schmidt-Roach, Sebastian; Bilalis, Panagiotis; Aranda, Manuel; Duarte, Carlos M.; Hauser, Charlotte (ACS Sustainable Chemistry & Engineering, American Chemical Society (ACS), 2021-09-02) [Article]
      Coral reef degradation is a rising problem, driven by marine heatwaves, the spread of coral diseases, and human impact by overfishing and pollution. Our capacity to restore coral reefs lags behind in terms of scale, effectiveness, and cost-efficiency. While common restoration efforts rely on the formation of carbonate skeletons on structural frames for supported coral growth, this technique is a rate-limiting step in the growth of scleractinian corals. Reverse engineering and additive manufacturing technologies offer an innovative shift in approach from the use of concrete blocks and metal frames to sophisticated efforts that use scanned geometries of harvested corals to fabricate artificial coral skeletons for installation in coral gardens and reefs. Herein, we present an eco-friendly and sustainable approach for coral fabrication by merging three-dimensional (3D) scanning, 3D printing, and molding techniques. Our method, 3D CoraPrint, exploits the 3D printing technology to fabricate artificial natural-based coral skeletons, expediting the growth rate of live coral fragments and quickening the reef transplantation process while minimizing nursery costs. It allows for flexibility, customization, and fast return time with an enhanced level of accuracy, thus establishing an environmentally friendly, scalable model for coral fabrication to boost restorative efforts around the globe.
    • Multifunctional Catalyst Combination for the Direct Conversion of CO2 to Propane

      Ramirez, Adrian; Ticali, Pierfrancesco; Salusso, Davide; Cordero-Lanzac, Tomas; Ould-Chikh, Samy; Ahoba-Sam, Christian; Bugaev, Aram L.; Borfecchia, Elisa; Morandi, Sara; Signorile, Matteo; Bordiga, Silvia; Gascon, Jorge; Olsbye, Unni (JACS Au, American Chemical Society (ACS), 2021-09-02) [Article]
      The production of carbon-rich hydrocarbons via CO2 valorization is essential for the transition to renewable, non-fossil-fuel-based energy sources. However, most of the recent works in the state of the art are devoted to the formation of olefins and aromatics, ignoring the rest of the hydrocarbon commodities that, like propane, are essential to our economy. Hence, in this work, we have developed a highly active and selective PdZn/ZrO2+SAPO-34 multifunctional catalyst for the direct conversion of CO2 to propane. Our multifunctional system displays a total selectivity to propane higher than 50% (with 20% CO, 6% C1, 13% C2, 10% C4, and 1% C5) and a CO2 conversion close to 40% at 350 °C, 50 bar, and 1500 mL g–1 h–1. We attribute these results to the synergy between the intimately mixed PdZn/ZrO2 and SAPO-34 components that shifts the overall reaction equilibrium, boosting CO2 conversion and minimizing CO selectivity. Comparison to a PdZn/ZrO2+ZSM-5 system showed that propane selectivity is further boosted by the topology of SAPO-34. The presence of Pd in the catalyst drives paraffin production via hydrogenation, with more than 99.9% of the products being saturated hydrocarbons, offering very important advantages for the purification of the products.
    • Methane decomposition to produce hydrogen and carbon nanomaterials over costless, iron-containing catalysts

      Qian, Jing Xia; Liu, Da Bin; Basset, Jean-Marie; Zhou, Lu (Journal of Cleaner Production, Elsevier BV, 2021-09-01) [Article]
      In this work, a series of iron-containing materials (not laboratory-synthesized but from natural, industrial raw materials, by-products or wastes), such as iron concentrate powder, fine/coarse ash and steel slag from steel plants and volcanic mud powder, were investigated as catalysts for methane decomposition. These catalysts exhibited relatively good methane conversion under the following conditions: 2.0 g of catalyst, 50 mL/min CH4, 900 °C for 5 h, even without hydrogen pre-reduction. Fe2O3 species on these samples were found to be gradually reduced by methane to Fe3O4, FeO and then finally into Fe0 active species. When methane decomposed onto the Fe0 active sites, Fe3C species would form to deposit graphite around themselves to finally form carbon nanomaterials, showing possible application in the oxygen evolution reaction and in Li-ion batteries as anode electrodes. Furthermore, using the best catalyst, iron concentrate powder, the effect of temperature and gas hourly space velocity was studied, where 900 °C and 3 L/gcat·h were determined as the optimized reaction conditions to reach the highest carbon/hydrogen yield.
    • There is plenty of room at the top: generation of hot charge carriers and their applications in perovskite and other semiconductor-based optoelectronic devices.

      Ahmed, Irfan; Shi, Lei; Pasanen, Hannu; Vivo, Paola; Maity, Partha; Hatamvand, Mohammad; Zhan, Yiqiang (Light, science & applications, Springer Science and Business Media LLC, 2021-09-01) [Article]
      Hot charge carriers (HC) are photoexcited electrons and holes that exist in nonequilibrium high-energy states of photoactive materials. Prolonged cooling time and rapid extraction are the current challenges for the development of future innovative HC-based optoelectronic devices, such as HC solar cells (HCSCs), hot energy transistors (HETs), HC photocatalytic reactors, and lasing devices. Based on a thorough analysis of the basic mechanisms of HC generation, thermalization, and cooling dynamics, this review outlines the various possible strategies to delay the HC cooling as well as to speed up their extraction. Various materials with slow cooling behavior, including perovskites and other semiconductors, are thoroughly presented. In addition, the opportunities for the generation of plasmon-induced HC through surface plasmon resonance and their technological applications in hybrid nanostructures are discussed in detail. By judiciously designing the plasmonic nanostructures, the light coupling into the photoactive layer and its optical absorption can be greatly enhanced as well as the successful conversion of incident photons to HC with tunable energies can also be realized. Finally, the future outlook of HC in optoelectronics is highlighted which will provide great insight to the research community.
    • Prediction of protein assemblies, the next frontier: The CASP14-CAPRI experiment.

      Lensink, Marc F.; Brysbaert, Guillaume; Mauri, Théo; Nadzirin, Nurul; Velankar, Sameer; Chaleil, Raphaël A G; Clarence, Tereza; Bates, Paul A; Kong, Ren; Liu, Bin; Yang, Guangbo; Liu, Ming; Shi, Hang; Lu, Xufeng; Chang, Shan; Roy, Raj S; Quadir, Farhan; Liu, Jian; Cheng, Jianlin; Antoniak, Anna; Czaplewski, Cezary; GiełdoŃ, Artur; Kogut, Mateusz; Lipska, Agnieszka G; Liwo, Adam; Lubecka, Emilia A; Maszota-Zieleniak, Martyna; Sieradzan, Adam K; Ślusarz, Rafał; Wesołowski, Patryk A; ZiĘba, Karolina; Del Carpio Muñoz, Carlos A; Ichiishi, Eiichiro; Harmalkar, Ameya; Gray, Jeffrey J; Bonvin, Alexandre M.J.J.; Ambrosetti, Francesco; Honorato, Rodrigo Vargas; Jandova, Zuzana; Jiménez-García, Brian; Koukos, Panagiotis I; Van Keulen, Siri; van Noort, Charlotte W; Réau, Manon; Roel-Touris, Jorge; Kotelnikov, Sergei; Padhorny, Dzmitry; Porter, Kathryn A; Alekseenko, Andrey; Ignatov, Mikhail; Desta, Israel; Ashizawa, Ryota; Sun, Zhuyezi; Ghani, Usman; Hashemi, Nasser; Vajda, Sandor; Kozakov, Dima; Rosell, Mireia; Rodríguez-Lumbreras, Luis A; Fernandez-Recio, Juan; Karczynska, Agnieszka; Grudinin, Sergei; Yan, Yumeng; Li, Hao; Lin, Peicong; Huang, Sheng-You; Christoffer, Charles; Terashi, Genki; Verburgt, Jacob; Sarkar, Daipayan; Aderinwale, Tunde; Wang, Xiao; Kihara, Daisuke; Nakamura, Tsukasa; Hanazono, Yuya; Gowthaman, Ragul; Guest, Johnathan D; Yin, Rui; Taherzadeh, Ghazaleh; Pierce, Brian G; Barradas Bautista, Didier; Cao, Zhen; Cavallo, Luigi; Oliva, Romina; Sun, Yuanfei; Zhu, Shaowen; Shen, Yang; Park, Taeyong; Woo, Hyeonuk; Yang, Jinsol; Kwon, Sohee; Won, Jonghun; Seok, Chaok; Kiyota, Yasuomi; Kobayashi, Shinpei; Harada, Yoshiki; Takeda-Shitaka, Mayuko; Kundrotas, Petras J; Singh, Amar; Vakser, Ilya A; DapkŪnas, Justas; Olechnovič, Kliment; Venclovas, Česlovas; Duan, Rui; Qiu, Liming; Zhang, Shuang; Zou, Xiaoqin; Wodak, Shoshana J (Proteins, Wiley, 2021-08-28) [Article]
      We present the results for CAPRI Round 50, the 4th joint CASP-CAPRI protein assembly prediction challenge. The Round comprised a total of 12 targets, including 6 dimers, 3 trimers, and 3 higher-order oligomers. Four of these were easy targets, for which good structural templates were available either for the full assembly, or for the main interfaces (of the higher-order oligomers). Eight were difficult targets for which only distantly related templates were found for the individual subunits. Twenty-five CAPRI groups including 8 automatic servers submitted ~1250 models per target. Twenty groups including 6 servers participated in the CAPRI scoring challenge submitted ~190 models per target. The accuracy of the predicted models was evaluated using the classical CAPRI criteria. The prediction performance was measured by a weighted scoring scheme that takes into account the number of models of acceptable quality or higher submitted by each group as part of their 5 top-ranking models. Compared to the previous CASP-CAPRI challenge, top performing groups submitted such models for a larger fraction (70-75%) of the targets in this Round, but fewer of these models were of high accuracy. Scorer groups achieved stronger performance with more groups submitting correct models for 70-80% of the targets or achieving high accuracy predictions. Servers performed less well in general, except for the MDOCKPP and LZERD servers, who performed on par with human groups. In addition to these results, major advances in methodology are discussed, providing an informative overview of where the prediction of protein assemblies currently stands.
    • Structural insights in mammalian sialyltransferases and fucosyltransferases: We have come a long way, but it is still a long way down

      Grewal, Ravneet Kaur; Shaikh, Abdul Rajjak; Gorle, Suresh; Kaur, Manjeet; Videira, Paula Alexendra; Cavallo, Luigi; Chawla, Mohit (Molecules, MDPI AG, 2021-08-27) [Article]
      Mammalian cell surfaces are modified with complex arrays of glycans that play major roles in health and disease. Abnormal glycosylation is a hallmark of cancer; terminal sialic acid and fucose in particular have high levels in tumor cells, with positive implications for malignancy. Increased sialylation and fucosylation are due to the upregulation of a set of sialyltransferases (STs) and fucosyltransferases (FUTs), which are potential drug targets in cancer. In the past, several advances in glycostructural biology have been made with the determination of crystal structures of several important STs and FUTs in mammals. Additionally, how the independent evolution of STs and FUTs occurred with a limited set of global folds and the diverse modular ability of catalytic domains toward substrates has been elucidated. This review highlights advances in the understanding of the structural architecture, substrate binding interactions, and catalysis of STs and FUTs in mammals. While this general understanding is emerging, use of this information to design inhibitors of STs and FUTs will be helpful in providing further insights into their role in the manifestation of cancer and developing targeted therapeutics in cancer.
    • Quantum Dot Self-Assembly Enables Low-Threshold Lasing

      Zhou, Chun; Pina, Joao M.; Zhu, Tong; H. Parmar, Darshan; Chang, Hao; Yu, Jie; Yuan, Fanglong; Bappi, Golam; Hou, Yi; Zheng, Xiaopeng; Abed, Jehad; Chen, Hao; Zhang, Jian; Gao, Yuan; Chen, Bin; Wang, Ya-Kun; Chen, Haijie; Zhang, Tianju; Hoogland, Sjoerd; Saidaminov, Makhsud I.; Sun, Liaoxin; Bakr, Osman; Dong, Hongxing; Zhang, Long; Sargent, E. (Advanced Science, Wiley, 2021-08-27) [Article]
      Perovskite quantum dots (QDs) are of interest for solution-processed lasers; however, their short Auger lifetime has limited lasing operation principally to the femtosecond temporal regime the photoexcitation levels to achieve optical gain threshold are up to two orders of magnitude higher in the nanosecond regime than in the femtosecond. Here the authors report QD superlattices in which the gain medium facilitates excitonic delocalization to decrease Auger recombination and in which the macroscopic dimensions of the structures provide the optical feedback required for lasing. The authors develope a self-assembly strategy that relies on sodiumd-an assembly director that passivates the surface of the QDs and induces self-assembly to form ordered three-dimensional cubic structures. A density functional theory model that accounts for the attraction forces between QDs allows to explain self-assembly and superlattice formation. Compared to conventional organic-ligand-passivated QDs, sodium enables higher attractive forces, ultimately leading to the formation of micron-length scale structures and the optical faceting required for feedback. Simultaneously, the decreased inter-dot distance enabled by the new ligand enhances exciton delocalization among QDs, as demonstrated by the dynamically red-shifted photoluminescence. These structures function as the lasing cavity and the gain medium, enabling nanosecond-sustained lasing with a threshold of 25 µJ cm<sup>-2</sup> .
    • Unactivated Alkyl Chloride Reactivity in Excited-State Palladium Catalysis

      Muralirajan, Krishnamoorthy; Kancherla, Rajesh; Gimnkhan, Aidana; Rueping, Magnus (Organic Letters, American Chemical Society (ACS), 2021-08-25) [Article]
      Excited-state palladium catalysis is an efficient process for the alkylation of diverse organic compounds via the generation of alkyl radicals from alkyl bromides and iodides. However, the generation of alkyl radicals from more stable alkyl chlorides remains challenging. Herein, we demonstrate the excited-state palladium-catalyzed synthesis of oxindoles and isoquinolinediones via alkylation/annulation reaction by overcoming inherent limitations associated with unactivated C(sp<sup>3</sup>)-Cl bond activation at room temperature.
    • Tunable Selectivity for Electrochemical CO2 Reduction by Bimetallic Cu–Sn Catalysts: Elucidating the Roles of Cu and Sn

      Zhang, Maolin; Zhang, Zedong; Zhao, Zhenghang; Huang, Hao; Anjum, Dalaver H.; Wang, Dingsheng; He, Jr-Hau; Huang, Kuo-Wei (ACS Catalysis, American Chemical Society (ACS), 2021-08-20) [Article]
      Production of formate or CO from electrochemical CO2 reduction reactions (eCO2RRs) represents a promising way to utilize CO2 with future low-carbon electricity to produce value-added chemicals and fuels. Herein, a series of Cu–Sn composite catalysts were designed for eCO2RRs. The reduction products could be tuned selectively from formate to CO by varying the Cu/Sn composition. The catalyst Cu1Sn1 with a CuSn alloy core and a SnO shell structure doped with a small amount of Cu gives a maximum faradic efficiency (FE) of 95.4 for formate at −1.2 V. In contrast, the single-Sn-atom-doped Cu of Cu20Sn1 is selective to CO with a maximum FE of 95.3% at −1.0 V. The DFT results reveal that the existence of small amounts of Cu or Sn single atoms in these two catalysts is critical to reducing the reaction free energies of CO2 reduction, resulting in the selective formation of formate and CO, respectively.
    • Steric Hindrance Drives the Boron-Initiated Polymerization of Dienyltriphenylarsonium Ylides to Photoluminescent C5-polymers.

      Wang, Xin; Hadjichristidis, Nikos (Angewandte Chemie (International ed. in English), Wiley, 2021-08-13) [Article]
      A series of alkyl-subsituted dienyltriphenylarsonium ylides were synthesized and used as monomers in borane-initiated polymerization to obtain practically C5-polymers (main-chain grows by five carbon atoms at a time). The impact of triethylborane (Et 3 B), tributylborane (Bu 3 B), tri- sec -butylborane ( s- Bu 3 B), and triphenylborane (Ph 3 B) initiators on C5 polymerization was studied. Based on NMR and SEC results, we have shown that all synthesized polymers have C5 units with a unique unsaturated backbone where two conjugated double bonds are separated by one methylene. The synthesized C5-polymers possess predictable molecular weights and narrow molecular weight distributions ( M n,NMR = 2.8 -11.9 kg mol -1 , Ð = 1.04-1.24). It has been found that increasing the steric hindrance of both the monomer and the initiator can facilitate the formation of more C5 repeating units, thus driving the polymerization to almost pure C5-polymer (up to 95.8%). The polymerization mechanism was studied by 11 B NMR and confirmed by DFT calculations. The synthesized C5-polymers are amorphous with tunable glass-transition temperatures by adjusting the substituents of monomers, ranging from +30.1 °C to -38.4 °C. Furthermore, they possess blue photoluminescence that changes to yellow illuminating the polymers for 5 days with UV radiation of 365 nm (IIE, isomerization induced emission).
    • Is Hydroxide Just Hydroxide? Unidentical CO2 Hydration Conditions during Hydrogen Evolution and Carbon Dioxide Reduction in Zero-Gap Gas Diffusion Electrode Reactors

      Haspel, Henrik; Gascon, Jorge (ACS Applied Energy Materials, American Chemical Society (ACS), 2021-08-12) [Article]
      The implementation of gas diffusion electrodes is a prerequisite to achieving industrially relevant reaction rates in gas-phase electrochemical CO2 reduction (CO2RR). In the state-of-the-art anion exchange membrane flow electrolyzers, however, there is a substantial loss of reactants due to a nonelectrochemical CO2 consumption at the cathode and the transport of its products to the anode. Our detailed analysis of CO2 crossover in a zero-gap CO2-to-CO flow electrolyzer showed a change in the chemical nature of the transported ionic species through the membrane. With the increasing reaction rate, a continuous shift from HCO3– to CO32– conduction was found to be similar to pure carbonate conduction in the high current density region (>100 mA cm–2). As competing hydrogen evolution takes over the cathodic reaction in a CO2-rich environment, hydroxide conduction becomes more pronounced. This reveals an alteration in the chemical CO2 consumption, the so-called CO2 hydration (CO2 + OH– ↔ HCO3– + OH– ↔ CO32–), implying an unidentical environment for the hydroxide ions generated in CO2RR and hydrogen evolution reaction under a CO2 atmosphere. Our work draws attention to the incomplete description of CO2 hydration at the confined cathode/membrane interface in membrane electrode assembly-type zero-gap CO2 electrolyzers.
    • Organocatalytic Synthesis of Polysulfonamides with Well-Defined Linear and Brush Architectures from a Designed/Synthesized Bis(N-sulfonyl aziridine)

      Zhu, Linlin; Huang, Huishan; Wang, Ying; Zhang, Zhen; Hadjichristidis, Nikos (Macromolecules, American Chemical Society (ACS), 2021-08-11) [Article]
      We report a new synthetic methodology for polysulfonamides with well-defined linear and brush architectures by organocatalytic polymerizations. A new monomer, bis(2,3-disubstituted N-sulfonyl aziridine), has been rationally designed/synthesized and used in step-growth polymerization with various bisnucleophiles (dicarboxylic acids, diphenols, and dithiols). The branches or cross-linkages derived from the ring-opening polymerization of N-sulfonyl aziridines are suppressed using this specific bis(aziridine) monomer, resulting in a well-controlled linear polysulfonamide architecture. The synthesized polysulfonamides emit blue fluorescence in solution and exhibit excellent thermal properties with decomposition temperature at 5% weight loss (Td,5%) up to 360.0 °C and glass-transition temperature (Tg) ranging from 62.5 to 199.2 °C. Furthermore, a fast one-pot cascade approach has been developed toward polysulfonamide brush copolymers with a well-controlled grafted chain length.
    • Manipulating crystallization dynamics through chelating molecules for bright perovskite emitters

      Zou, Yatao; Teng, Pengpeng; Xu, Weidong; Zheng, Guanhaojie; Lin, Weihua; Yin, Jun; Kobera, Libor; Abbrent, Sabina; Li, Xiangchun; Steele, Julian A.; Solano, Eduardo; Roeffaers, Maarten B. J.; Li, Jun; Cai, Lei; Kuang, Chaoyang; Scheblykin, Ivan G.; Brus, Jiri; Zheng, Kaibo; Yang, Ying; Mohammed, Omar F.; Bakr, Osman; Pullerits, Tönu; Bai, Sai; Sun, Baoquan; Gao, Feng (Nature Communications, Springer Science and Business Media LLC, 2021-08-10) [Article]
      AbstractMolecular additives are widely utilized to minimize non-radiative recombination in metal halide perovskite emitters due to their passivation effects from chemical bonds with ionic defects. However, a general and puzzling observation that can hardly be rationalized by passivation alone is that most of the molecular additives enabling high-efficiency perovskite light-emitting diodes (PeLEDs) are chelating (multidentate) molecules, while their respective monodentate counterparts receive limited attention. Here, we reveal the largely ignored yet critical role of the chelate effect on governing crystallization dynamics of perovskite emitters and mitigating trap-mediated non-radiative losses. Specifically, we discover that the chelate effect enhances lead-additive coordination affinity, enabling the formation of thermodynamically stable intermediate phases and inhibiting halide coordination-driven perovskite nucleation. The retarded perovskite nucleation and crystal growth are key to high crystal quality and thus efficient electroluminescence. Our work elucidates the full effects of molecular additives on PeLEDs by uncovering the chelate effect as an important feature within perovskite crystallization. As such, we open new prospects for the rationalized screening of highly effective molecular additives.
    • Electrochemical synthesis of continuous metal–organic framework membranes for separation of hydrocarbons

      Zhou, Sheng; Shekhah, Osama; Jia, Jiangtao; Czaban-Jozwiak, Justyna; Bhatt, Prashant; Galilea, Adrian; Gascon, Jorge; Eddaoudi, Mohamed (Nature Energy, Springer Science and Business Media LLC, 2021-08-09) [Article]
      Membrane-based approaches can offer energy-efficient and cost-effective methods for various separation processes. Practical membranes must have high permselectivity at industrially relevant high pressures and under aggressive conditions, and be manufacturable in a scalable and robust fashion. We report a versatile electrochemical directed-assembly strategy to fabricate polycrystalline metal–organic framework membranes for separation of hydrocarbons. We fabricate a series of face-centred cubic metal–organic framework membranes based on 12-connected rare-earth or zirconium hexanuclear clusters with distinct ligands. In particular, the resultant fumarate-based membranes containing contracted triangular apertures as sole entrances to the pore system enable molecular-sieving separation of propylene/propane and butane/isobutane mixtures. Prominently, increasing the feed pressure to the industrially practical value of 7 atm promoted a desired enhancement in both the total flux and separation selectivity. Process design analysis demonstrates that, for propylene/propane separation, the deployment of such face-centred cubic Zr-fumarate-based metal–organic framework membranes in a hybrid membrane–distillation system offers the potential to decrease the energy input by nearly 90% relative to a conventional single distillation process.
    • Spontaneous Production of Ultrastable Reactive Oxygen Species on Titanium Oxide Surfaces Modified with Organic Ligands

      Ritacco, Ida; Imparato, Claudio; Falivene, Laura; Cavallo, Luigi; Magistrato, Alessandra; Caporaso, Lucia; Farnesi Camellone, Matteo; Aronne, Antonio (Advanced Materials Interfaces, Wiley, 2021-08-08) [Article]
      The spontaneous formation and long-term surface stabilization of superoxide radicals are observed on specific TiO2 hybrid materials in which titanium is coordinated to an organic ligand. Here the rationale for this uncommon phenomenon is investigated by a synergistic theoretical and experimental approach involving density functional theory (DFT) calculations and spectroscopic techniques. Stoichiometric and reduced anatase (101) surfaces modified with acetylacetone, dibenzoylmethane, and catechol are comparatively examined. These results reveal that the interaction between organic ligands and adsorbed O2 molecules improves when O vacancies are present on the external layer of the surface, promoting O2 reduction. The electronic features of the ligand play a pivotal role for both an effective electronic interaction with the surface and the stabilization of the generated reactive oxygen species. These results agree with experimental data showing that sol–gel-derived Ti-diketonate hybrid oxides spontaneously produce very persistent superoxide radicals under ambient conditions, thus holding a high intrinsic oxidative activity.