Now showing items 1-20 of 2635

    • Topochemical Synthesis of Ca3CrN3H Involving a Rotational Structural Transformation for Catalytic Ammonia Synthesis

      Cao, Yu; Kirsanova, Maria; Ochi, Masayuki; Almaksoud, Walid; Zhu, Tong; Rai, Rohit Kumar; Gao, Shenghan; Tsumori, Tatsuya; Kobayashi, Shintaro; Kawaguchi, Shogo; Abou-Hamad, Edy; Kuroki, Kazuhiko; Tassel, Cédric; Abakumov, Artem; Kobayashi, Yoji; Kageyama, Hiroshi (Angewandte Chemie (International ed. in English), Wiley, 2022-08-05) [Article]
      Topochemical reactions have led to great progress in the discovery of new metastable compounds with novel chemical and physical properties. With these reactions, the overall crystal structure of the host material is generally maintained. Here we report a topochemical synthesis of a hexagonal nitride hydride, h-Ca3CrN3H, by heating an orthorhombic nitride, o-Ca3CrN3, under hydrogen at 673 K, accompanied by a rotational structural transformation. The hydrogen intercalation modifies the Ca-N rock-salt-like atomic packing in o-Ca3CrN3 to a face-sharing octahedral chain in h-Ca3CrN3H, mimicking a 'hinged tessellation' movement. In addition, the h-Ca3CrN3H exhibited stable ammonia synthesis activity when used as a catalyst.
    • Immunoinformatics-Aided Design and In Vivo Validation of a Peptide-Based Multiepitope Vaccine Targeting Canine Circovirus

      Kaushik, Vikas; Jain, Pankaj; Akhtar, Nahid; Joshi, Amit; Gupta, Lovi Raj; Grewal, Ravneet Kaur; Oliva, Romina; Shaikh, Abdul Rajjak; Cavallo, Luigi; Chawla, Mohit (ACS Pharmacology & Translational Science, American Chemical Society (ACS), 2022-08-03) [Article]
      Canine circovirus (CanineCV) is a deadly pathogen affecting both domestic and wild carnivores including dogs. No vaccine against CanineCV is available commercially or under clinical trials. In the present study, we have designed a promising multiepitope vaccine (MEV) construct targeting multiple strains of CanineCV. A total of 545 MHCII binding CD4+T cell epitope peptides were predicted from the capsid and replicase protein from each strain of CanineCV. Five conserved epitope peptides among the three CanineCV strains were selected. The final vaccine was constructed using antigenic, nontoxic, and conserved multiple epitopes identified in silico. Further, molecular docking and molecular dynamics simulations predicted stable interactions between the predicted MEV and canine receptor TLR-5. To validate antigenicity and immunogenicity, one of the mapped epitope peptides was synthesized. In vivo analysis of the selected epitope clearly indicates CD4+T-cell-dependent generation of antibodies which further suggests that the designed MEV construct holds promise as a candidate for vaccine against CanineCV.
    • Bi12O17Cl2 with a Sextuple BiO Layer Composed of Rock-Salt and Fluorite Units and its Structural Conversion through Fluorination to Enhance Photocatalytic Activity

      Kato, Daichi; Tomita, Osamu; Nelson, Ryky; Kirsanova, Maria A.; Dronskowski, Richard; Suzuki, Hajime; Zhong, Chengchao; Tassel, Cédric; Ishida, Kohdai; Matsuzaki, Yosuke; Brown, Craig M.; Fujita, Koji; Fujii, Kotaro; Yashima, Masatomo; Kobayashi, Yoji; Saeki, Akinori; Oikawa, Itaru; Takamura, Hitoshi; Abe, Ryu; Kageyama, Hiroshi; Gorelik, Tatiana E.; Abakumov, Artem M. (Advanced Functional Materials, Wiley, 2022-08-02) [Article]
      Layered bismuth oxyhalides with bilayered (Bi2O2) fluorite (FL) slabs are promising visible-light photocatalysts because of their excellent stability and the ability to adjust band levels depending on the layers combined. It is interesting to manipulate the Bi2O2 slab itself, but only trilayered FL blocks (e.g., Bi3O4) are reported so far. Here, a structurally uncharacterized Bi12O17Cl2, which is extensively studied as a photocatalyst for a variety of reactions, has a sextuple Bi6O8.5 block separated by Cl is shown. Unlike double and triple layered cases, the inner region of the Bi6O8.5 block contains 1D rock-salt (RS) units in the FL matrix along the a-axis, causing in-plane corrugation. A topochemical reaction involving anion-exchange gives Bi12O17–0.5xFxCl2 (x ≤ 6) with alternate FL and RS slabs along the c-axis. The elimination of the structural corrugation increases higher photo-conductivity and improves photocatalytic activity against acetic acid decomposition under visible light irradiation. This study paves new opportunities of controlling the properties of layered bismuth oxyhalides by the thickness of Bi–O block, FL/RS configuration, and structural modulation.
    • Surface decorated Ni sites for superior photocatalytic hydrogen production

      Huang, Wenhuan; Bo, Tingting; Zuo, Shouwei; Wang, Yunzhi; Chen, Jiamin; Ould-Chikh, Samy; Li, Yang; Zhou, Wei; Zhang, Jing; Zhang, Huabin (SusMat, Wiley, 2022-07-30) [Article]
      Precise construction of isolated reactive centers on semiconductors with well-controlled configurations affords a great opportunity to investigate the reaction mechanisms in the photocatalytic process and realize the targeted conversion of solar energy to steer the charge kinetics for hydrogen evolution. In the current research, we decorated isolated Ni atoms on the surface of CdS nanowires for efficient photocatalytic hydrogen production. X-ray absorption fine structure investigations clearly demonstrate the atomical dispersion of Ni sites on the surface of CdS nanowires. Experimental investigations reveal that the isolated Ni atoms not only perform well as the real reactive centers but also greatly accelerate the electron transfer via direct Ni–S coordination. Theoretical simulation further documents that the hydrogen adsorption process has also been enhanced over the semi-coordinated Ni centers through electronic coupling at the atomic scale.
    • Aggregation-Induced Fluorescence Enhancement for Efficient X-ray Imaging Scintillators and High-Speed Optical Wireless Communication

      Wang, Jian-Xin; Wang, Yue; Nadinov, Issatay; Yin, Jun; Gutierrez Arzaluz, Luis; Alkhazragi, Omar; He, Tengyue; Ng, Tien Khee; Eddaoudi, Mohamed; Alshareef, Husam N.; Bakr, Osman; Ooi, Boon S.; Mohammed, Omar F. (ACS Materials Letters, American Chemical Society (ACS), 2022-07-29) [Article]
      Aggregation of some chromophores generates very strong fluorescence signals due to the tight molecular packing and highly restricted vibrational motions in the electronically excited states. Such an aggregation-induced emission enhancement enables great strides in biomedical imaging, security screening, sensing, and light communication applications. Here, we realized efficient utilization of a series of aggregation-induced emission luminogens (AIEgens) in X-ray imaging scintillators and optical wireless communication (OWC) technology. Ultrafast time-resolved laser spectroscopic experiments and high-level density functional theory (DFT) calculations clearly demonstrate that a significant increase in the rotational energy barrier in the aggregated state of AIEgens is observed, leading to highly restricted molecular vibrations and suppressed nonradiative processes. AIEgen-based scintillators exhibit a high X-ray imaging resolution of 16.3 lp mm–1, making them excellent candidates for X-ray radiography and security inspections. In addition, these AIEgens show a broad -3-dB modulation bandwidth of ∼110 MHz and high net data rates of ∼600 Mb/s, demonstrating their high potential for application in the field of high-speed OWC.
    • Highly Efficient Electrocatalytic Oxygen Evolution Over Atomically Dispersed Synergistic  Ni/Co Dual Sites

      Pei, Zhihao; Lu, Xue Feng; Zhang, Huabin; Li, Yunxiang; Luan, Deyan; Lou, Xiong-Wen (David) (Angewandte Chemie International Edition, Wiley, 2022-07-27) [Article]
      Single-atom catalysts (SACs) are being pursued as economical electrocatalysts. However, their low active-site loading, poor interactions, and unclear catalytic mechanism call for significant advances. Herein, atomically dispersed Ni/Co dual sites anchored on nitrogen-doped carbon (a-NiCo/NC) hollow prisms are rationally designed and synthesized. Benefiting from the atomically dispersed dual-metal sites and their synergistic interactions, the obtained a-NiCo/NC sample exhibits superior electrocatalytic activity and kinetics towards the oxygen evolution reaction. Moreover, density functional theory calculations indicate that the strong synergistic interactions from heteronuclear paired Ni/Co dual sites lead to the optimization of the electronic structure and the reduced reaction energy barrier. This work provides a promising strategy for the synthesis of high-efficiency atomically dispersed dual-site SACs in the field of electrochemical energy storage and conversion.
    • Fabrication of Nio Dopped Cuo Nanosheets Decorated with Resorcinol Farmaldehyde Resin for Enhanced Photocatalytic Application

      Ullah, Sana; Shah, Muslim; Raziq, Fazal; Ali, Sharafat; Rehman, Anis Ur; Zarshad, Nighat; wadood, Abdul; Ullah, Ihsan; Hayat, Khizar; Li, Guigen; Ali, Asad (Elsevier BV, 2022-07-27) [Preprint]
      The quest for z-scheme efficient photo catalytic system has been proved to be an impressive approach to enhance reactivity and selectivity for carbon dioxide conversion into value-added energy dense molecules to cope with the increasing clean energy demand in future. Herein, we developed a versatile strategy for the Z-scheme heterojunction synthesis of NiO doped CuO well defined hexagonal nanosheets decorated with RF (Resorcinol-Formaldehyde resin). The Photo-generated electrons migrate to NiO doped CuO from the π-π stacking in benzenoid-quinoid conjugated system of RF resin, where these electrons are accommodated by carbonyl group of quinoid acceptor unit, and the positive holes leave in semiconductor heterojunction for water oxidation. The nanosheets morphology of NiO doped CuO has enhanced surface area, active sites, improved charge separation and elevated CO2 reduction potential of the heterojunction. The small HOMO-LUMO gap of RF resin facilitate migration of electrons from the CB of RF to VB of CuO. The photocatalytic degradation of the 2,4-DCP was investigated which is 95% per hour. We claim the highest activity achievement in terms of CO2 reduction (230 μ mol g-1 h-1) which is 6 folds greater than the pure CuO (39.5 μ mol g-1 h-1) photocatalyst and pollutant degradation of the heterojunction till date.
    • High-Performance Copper-Doped Perovskite-Related Silver Halide X-ray Imaging Scintillator

      He, Tengyue; Zhou, Yang; Wang, Xiaojia; Yin, Jun; Gutierrez Arzaluz, Luis; Wang, Jian-Xin; Zhang, Yuhai; Bakr, Osman; Mohammed, Omar F. (ACS Energy Letters, American Chemical Society (ACS), 2022-07-26) [Article]
      Scintillators are critical for high-energy radiation detection across a wide array of potential applications, from medical radiography and safety inspections all the way to space exploration. However, constrained by their current shortcomings, including high-temperature and complex fabrication as well as inherent brittleness and fragility among thick films and bulk crystals, traditional scintillators are finding it difficult to meet the rising demand for cost-effective, ecofriendly, and flexible X-ray detection. Here, we describe the development of high-performance and flexible X-ray scintillators based on films of Cu-doped Cs2AgI3 that exhibit ultrahigh X-ray sensitivity. The materials exhibit a high scintillation light yield of up to 82 900 photons/MeV and a low detection limit of 77.8 nGy/s, which is approximately 70 times lower than the dosage for a standard medical examination. Moreover, richly detailed X-ray images of biological tissue and electronic components with a high spatial resolution of 16.2 lp/mm were obtained using flexible, large-area, solution-processed scintillation screens.
    • Pdzn/Zro2 + Sapo-34 Bifunctional Catalyst for Co2 Conversion: Further Insights by Spectroscopic Characterization

      Ticali, Pierfrancesco; Morandi, Sara; Shterk, Genrikh; Ould-Chikh, Samy; Ramirez, Adrian; Gascon, Jorge; Chung, Sang-ho; Ruiz-Martinez, Javier; Bordiga, Silvia (Elsevier BV, 2022-07-26) [Preprint]
      The present work aims at further investigating a previously studied PdZn/ZrO2+SAPO-34 bifunctional catalyst for CO2 conversion. High activity and selectivity for propane was proved and the results obtained by NAP-XPS measurements and CO adsorption at liquid-nitrogen temperature (LNT) followed by FT-IR spectroscopy are shown. After reduction, we confirmed the formation of PdZn alloy. At LNT Pd carbonyl band shows a peculiar behavior linked to an intimate interaction between PdZn particles, ZnO and ZrO2.The combined system was characterized as fresh, used and regenerated. On the fresh PdZn/ZrO2+SAPO-34 the characteristic features of the two components do not appear perturbed by the mixing. As for the used system, the absence of Pd carbonyls and the decrease of CO on SAPO-34 Brønsted acid sites are correlated to organic species revealed by ssNMR. Regeneration in oxygen restores catalytic sites, although new Pd carbonyls appear due to Pd2+ ionic exchange into SAPO-34 framework.
    • Pdzn/Zro2 + Sapo-34 Bifunctional Catalyst for Co2 Conversion: Further Insights by Spectroscopic Characterization

      Ticali, Pierfrancesco; Morandi, Sara; Shterk, Genrikh; Ould-Chikh, Samy; Ramirez, Adrian; Gascon, Jorge; Chung, Sang-ho; Ruiz-Martinez, Javier; Bordiga, Silvia (Elsevier BV, 2022-07-26) [Preprint]
      The present work aims at further investigating a previously studied PdZn/ZrO2+SAPO-34 bifunctional catalyst for CO2 conversion. High activity and selectivity for propane was proved and the results obtained by NAP-XPS measurements and CO adsorption at liquid-nitrogen temperature (LNT) followed by FT-IR spectroscopy are shown. After reduction, we confirmed the formation of PdZn alloy. At LNT Pd carbonyl band shows a peculiar behavior linked to an intimate interaction between PdZn particles, ZnO and ZrO2.The combined system was characterized as fresh, used and regenerated. On the fresh PdZn/ZrO2+SAPO-34 the characteristic features of the two components do not appear perturbed by the mixing. As for the used system, the absence of Pd carbonyls and the decrease of CO on SAPO-34 Brønsted acid sites are correlated to organic species revealed by ssNMR. Regeneration in oxygen restores catalytic sites, although new Pd carbonyls appear due to Pd2+ ionic exchange into SAPO-34 framework.
    • Novel Tpms Contactors Designed with Imprinted Porosity: Numerical Evaluation of Momentum and Energy Transport

      Grande, Carlos; Asif, Mohammad (Elsevier BV, 2022-07-25) [Preprint]
      Structured packings in reactors and separation processes have an extensive trait for process intensification such as enhancement in mass and heat transport without having any substantial pressure drop and can now successfully be produced by using additive manufacturing methods such as 3D printing. Structured packings manufactured with Triply Periodical Minimum Surfaces (TPMS) have good mixing properties and enhanced thermal transport, but they do not have high surface areas.In this work, we report a new type of hybrid TPMS structures with high surface area while keeping good mixing properties. The new shapes are made by generating solids on the boundaries of a 2D tessellation of polygons over the TPMS surface. The new shapes have a higher surface area than a TPMS and at the same time, a higher porosity. We have evaluated the pressure drop and heat transfer properties of such structures for Reynolds numbers 1-200 in ten different solids. The results indicate that pressure drop is dominated by porosity. Heat transfer properties however depend also on available surface area and thus are improved in the porous structures.
    • Maximizing Active Fe Species in ZSM-5 Zeolite Using Organic-Template-Free Synthesis for Efficient Selective Methane Oxidation

      Cheng, Qingpeng; Li, Guanna; Yao, Xueli; Zheng, Lirong; Wang, Junhu; Emwas, Abdul-Hamid M.; Castaño, Pedro; Ruiz-Martinez, Javier; Han, Yu (Research Square Platform LLC, 2022-07-22) [Preprint]
      The selective oxidation of CH4 in the aqueous phase to produce valuable chemicals has attracted considerable research attention due to its mild reaction conditions and simple process. As the most widely studied catalyst for this reaction, Fe-containing ZSM-5 zeolite (Fe-ZSM-5) demonstrates high intrinsic activity and selectivity; however, Fe-ZSM-5 prepared using conventional methods has a limited number of active Fe sites, resulting in low CH4 conversion per unit mass of the catalyst. To address this issue, this study reports a facile organic-template-free synthesis strategy that enables the incorporation of more Fe into the zeolite framework with a higher dispersion degree compared to conventional synthesis methods. Because framework Fe incorporated in this way is more readily to transform into isolated extra-framework Fe species under thermal treatment, the overall effect is that Fe-ZSM-5 prepared using this method (Fe-HZ5-TF) has three times as many catalytically active sites as conventional Fe-ZSM-5. When used for the selective oxidation of CH4 (30.5 bar) with 0.5 M H2O2 at 75°C, Fe-HZ5-TF produced a record high C1 oxygenate yield of 106.3 mmol gcat−1 h− 1 (a HCOOH selectivity of 91.3%), surpassing other catalysts reported to date. Spectroscopic characterization and density functional theory calculations revealed that the active sites in Fe-HZ5-TF are mononuclear Fe species in the form of [(H2O)3Fe(IV) = O]2+ bound to Al pairs in the zeolite framework. This differs from conventional Fe-ZSM-5, where binuclear Fe acts as the active site. Analysis of the catalyst and product evolution during the reaction suggests a radical-driven pathway to explain CH4 activation at the mononuclear Fe site and subsequent conversion to C1 oxygenates.
    • Direct Band Gap in Multilayer Transition Metal Dichalcogenide Nanoscrolls with Enhanced Photoluminescence

      Lin, Ci; Cai, Liang; Fu, Jui-Han; Sattar, Shahid; Wang, Qingxiao; Wan, Yi; Tseng, Chien-Chih; Yang, Chih-Wen; Aljarb, Areej; Jiang, Ke; Huang, Kuo-Wei; Li, Lain-Jong; Canali, Carlo Maria; Shi, Yumeng; Tung, Vincent (ACS Materials Letters, American Chemical Society (ACS), 2022-07-20) [Article]
      A direct band gap that solely exists in monolayer semiconducting transition metal dichalcogenides (TMDs) endows strong photoluminescence (PL) features, whereas multilayer TMD structures exhibit quenched PL due to the direct-to-indirect band gap transition. We demonstrate multilayer TMD (such as MoS2 and WS2) nanoscrolls with a preserved direct band gap fabricated by an effective and facile method of solvent-driven self-assembly. The resultant multilayer nanoscrolls, exhibiting up to 11 times higher PL intensity than the remanent monolayer, are carefully characterized using PL spectroscopy. Significantly enlarged interlayer distances and modulated interlayer coupling in the fabricated nanostructures are unveiled by cross-sectional scanning transmission electron microscopy, atomic force microscopy, and Raman spectroscopy. The preservation of direct band gap features is further evidenced by density functional theory calculations using the simplified bilayer model with an experimentally obtained 15 Å interlayer distance. The modulation of the PL intensity as an indicator of the band gap crossover in the TMD nanoscrolls is demonstrated by removing the acetone molecules trapped inside the interlayer space. The general applicability of the method presents an opportunity for large-scale fabrication of a plethora of multilayer TMD nanoscrolls with direct band gaps.
    • Shockwave impact on the stability of anatase titania nanoparticles

      Slama de Freitas, Ana Luiza; Subburaj, Janardhanraj; Navarro, Juan Carlos; Khan, Hassnain Abbas; Kashif, Touqeer Anwar; Hakimov, Khaiyom; Ruiz-Martinez, Javier; Farooq, Aamir (Materials Today Communications, Elsevier BV, 2022-07-20) [Article]
      The stability of anatase titania nanoparticles was investigated under exposure to repeated loading of shockwaves produced in a diaphragm-driven high-pressure shock tube. The titania samples were exposed to 20 shocks with pressure, temperature, and steady exposure time in the range of 20.5 – 26 bar, 1399 – 2101 K, and 1.74 – 1.83 ms, respectively. The crystal structure and surface morphology were analyzed before and after the shockwave treatment using various characterization techniques. After repeated shock exposure, there was reduction in crystallite size by ~ 40%, modification in the surface charge, and an increase in the hydroxyl groups in titania. The onset of phase transformation from anatase to rutile was observed after 20 shocks. This work gives insights into the structural changes induced by shockwaves in anatase nanoparticles which can help improve their performance as a catalytic support in heterogeneous catalysis.
    • Decreasing the Coking and Deactivation of a Reforming Ni-Ce/Al2o3 Catalyst with Intraparticle Sic in Hydrogen Production Routes

      Tavares, F.; Mohamed, Hend Omar; Kulkarni, Shekhar Rajabhau; Morlanes, Natalia Sanchez; Castaño, Pedro (Elsevier BV, 2022-07-19) [Preprint]
      Steam reforming processes are under pressure to fuel the hydrogen economy, cutting its significant carbon footprint and transitioning to renewable feedstock while improving catalyst performance and lifetime. A seemingly inert material, such as silicon carbide (SiC, also known as carborundum), introduced in catalytic particles significantly influences catalytic performance, particularly during deactivation. We synthesized different catalysts with similar amounts of active materials (20 wt% of Ni and 2 wt% of Ce) and varied the proportion (0 to 78 wt%) and particle size (38 to 112 µm) of SiC within the alumina support. We used various techniques to characterize the catalysts and test them in reforming heptane, which was employed as the model molecule. The maximum enhancement with SiC occurs using 20 wt% of SiC with a size of 38 µm. Further, the enhancement with SiC is due to the control of the Ni particle size, leading to a 26% improvement in the apparent reaction rate (per exposed Ni) and a 117% decline in the deactivation rate compared to the SiC-free counterpart.
    • Switching Electrolyte Interfacial Model to Engineer Solid Electrolyte Interface for Fast Charging and Wide-Temperature Lithium-Ion Batteries

      Liu, Gang; Cao, Zhen; Wang, Peng; Ma, Zheng; Zou, Yeguo; Sun, Qujiang; Cheng, Haoran; Cavallo, Luigi; Li, Shiyou; Li, Qian; Ming, Jun (Advanced Science, Wiley, 2022-07-17) [Article]
      Engineering the solid electrolyte interphase (SEI) that forms on the electrode is crucial for achieving high performance in metal-ion batteries. However, the mechanism of SEI formation resulting from electrolyte decomposition is not fully understood at the molecular scale. Herein, a new strategy of switching electrolyte to tune SEI properties is presented, by which a unique and thinner SEI can be pre-formed on the graphite electrode first in an ether-based electrolyte, and then the as-designed graphite electrode can demonstrate extremely high-rate capabilities in a carbonate-based electrolyte, enabling the design of fast-charging and wide-temperature lithium-ion batteries (e.g., graphite | LiNi0.6Co0.2Mn0.2O2 (NCM622)). A molecular interfacial model involving the conformations and electrochemical stabilities of the Li+-solvent-anion complex is presented to elucidate the differences in SEI formation between ether-based and carbonate-based electrolytes, then interpreting the reason for the obtained higher rate performances. This innovative concept combines the advantages of different electrolytes into one battery system. It is believed that the switching strategy and understanding of the SEI formation mechanism opens a new avenue to design SEI, which is universal for pursuing more versatile battery systems with greater stability.
    • Brønsted acid catalyzed enantioselective addition of hydrazones to 3-indolylmethanols

      Mader, Steffen; Maji, Modhu Sudan; Atodiresei, Iuliana; Rueping, Magnus (Organic Chemistry Frontiers, Royal Society of Chemistry (RSC), 2022-07-15) [Article]
      The organocatalytic asymmetric addition of hydrazones to indole derivatives in the presence of chiral Brønsted acids is reported. A large variety of substrates are tolerated and the products are obtained in good yields and with excellent enantioselectivities. This metal-free reaction provides a convenient route to enantiopure β-substituted tryptophan derivatives in a concise fashion.
    • Selective palladium recovery by a highly porous polyisothiocyanurate

      Nguyen, Thien Si; Yavuz, Cafer Tayyar (Chem, Elsevier BV, 2022-07-14) [Article]
      Precious metals, particularly palladium (Pd), are in short supply, and their effective recovery from waste depends on metal-specific adsorbents that provide energy-efficient and environmentally friendly solutions. In this issue of Chem, Coskun and co-workers introduce a new porous organic polymer with exceptional porosity and stability and record-high capacity and selectivity toward Pd.
    • Dual Experimental and Computational Approach to Elucidate the Effect of Ga on Cu/Ceo2–Zro2 Catalyst for Co2 Hydrogenation

      Attada, Yerrayya; Velisoju, Vijay Kumar; Mohamed, Hend Omar; Ramirez, Adrian; Castaño, Pedro (Elsevier BV, 2022-07-14) [Preprint]
      Intermetallic Cu–Ga catalysts are potential candidates for activating the selective and stable hydrogenation of carbon dioxide to methanol and dimethyl ether. This work explores the structure–function relationship in specific Cu–Ga/CeO 2 –ZrO 2 catalysts with different Ga loadings. Combining experiments with density functional theory calculations, we find the most well-balanced intermetallic Cu–Ga interphase (structure) and promote specific mechanistic pathways of the reaction (function). The experiments yielded the highest selectivity of the desired products when the Cu and Ga amounts were equal. The experimental work and density functional theory calculations demonstrated that methanol is formed through the carboxyl pathway on the Cu catalyst, while Ga promotes the formate pathway. Consequently, the productivities of both methanol and dimethyl ether are enhanced. The experimental results match well with the theoretical calculations. Comparing our results with other Ga-promoting systems, we also prove that Cu achieves better balance than Ni and Co.
    • Lecithin Capping Ligands Enable Ultrastable Perovskite-Phase CsPbI3 Quantum Dots for Rec. 2020 Bright-Red Light-Emitting Diodes

      Mir, Wasim Jeelani; Alamoudi, Ahmed; Yin, Jun; Yorov, Khursand E.; Maity, Partha; Naphade, Rounak; Shao, Bingyao; Wang, Jiayi; Lintangpradipto, Muhammad Naufal; Nematulloev, Saidkhodzha; Emwas, Abdul-Hamid M.; Genovese, Alessandro; Mohammed, Omar F.; Bakr, Osman (Journal of the American Chemical Society, American Chemical Society (ACS), 2022-07-14) [Article]
      Bright-red light-emitting diodes (LEDs) with a narrow emission line width that emit between 620 and 635 nm are needed to meet the latest industry color standard for wide color gamut displays, Rec. 2020. CsPbI3 perovskite quantum dots (QDs) are one of the few known materials that are ideally suited to meet these criteria. Unfortunately, CsPbI3 perovskite QDs are prone to transform into a non-red-emitting phase and are subject to further degradation mechanisms when their luminescence wavelength is tuned to match that of the Rec. 2020 standard. Here, we show that zwitterionic lecithin ligands can stabilize the perovskite phase of CsPbI3 QDs for long periods in air for at least 6 months compared to a few days for control samples. LEDs fabricated with our ultrastable lecithin-capped CsPbI3 QDs exhibit an external quantum efficiency (EQE) of 7.1% for electroluminescence centered at 634 nm─a record for all-inorganic perovskite nanocrystals in Rec. 2020 red. Our devices achieve a maximum luminance of 1391 cd/m2 at 7.5 V, and their operational half-life is 33 min (T50) at 200 cd/m2─a 10-fold enhancement compared to control samples. Density functional theory results suggest that the surface strain in CsPbI3 QDs capped with the conventional ligands, oleic acid and oleylamine, contributes to the instability of the perovskite structural phase. On the other hand, lecithin binding induces virtually no surface strain and shows a stronger binding tendency for the CsPbI3 surface. Our study highlights the tremendous potential of zwitterionic ligands in stabilizing the perovskite phase and particle size of CsPbI3 QDs for various optoelectronic applications.