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  • Fast water transport and molecular sieving through ultrathin ordered conjugated-polymer-framework membranes

    Shen, Jie; Cai, Yichen; Zhang, Chenhui; Wei, Wan; Chen, Cailing; Liu, Lingmei; Yang, Kuiwei; Ma, Yinchang; Wang, Yingge; Tseng, Chien-Chih; Fu, Jui-Han; Dong, Xinglong; Li, Jiaqiang; Zhang, Xixiang; Li, Lain-Jong; Jiang, Jianwen; Pinnau, Ingo; Tung, Vincent; Han, Yu (Nature Materials, Springer Science and Business Media LLC, 2022-08-08) [Article]
    The development of membranes that block solutes while allowing rapid water transport is of great importance. The microstructure of the membrane needs to be rationally designed at the molecular level to achieve precise molecular sieving and high water flux simultaneously. We report the design and fabrication of ultrathin, ordered conjugated-polymer-framework (CPF) films with thicknesses down to 1 nm via chemical vapour deposition and their performance as separation membranes. Our CPF membranes inherently have regular rhombic sub-nanometre (10.3 × 3.7 Å) channels, unlike membranes made of carbon nanotubes or graphene, whose separation performance depends on the alignment or stacking of materials. The optimized membrane exhibited a high water/NaCl selectivity of ∼6,900 and water permeance of ∼112 mol m−2 h−1 bar−1, and salt rejection >99.5% in high-salinity mixed-ion separations driven by osmotic pressure. Molecular dynamics simulations revealed that water molecules quickly and collectively pass through the membrane by forming a continuous three-dimensional network within the hydrophobic channels. The advent of ordered CPF provides a route towards developing carbon-based membranes for precise molecular separation.
  • Low-voltage ultrafast nonvolatile memory via direct charge injection through a threshold resistive-switching layer

    Li, Yuan; Zhang, Zhi Cheng; Li, Jiaqiang; Chen, Xu-Dong; Kong, Ya; Wang, Fu-Dong; Zhang, Guo-Xin; Lu, Tong-Bu; Zhang, Jin (Nature communications, Springer Science and Business Media LLC, 2022-08-06) [Article]
    The explosion in demand for massive data processing and storage requires revolutionary memory technologies featuring ultrahigh speed, ultralong retention, ultrahigh capacity and ultralow energy consumption. Although a breakthrough in ultrafast floating-gate memory has been achieved very recently, it still suffers a high operation voltage (tens of volts) due to the Fowler-Nordheim tunnelling mechanism. It is still a great challenge to realize ultrafast nonvolatile storage with low operation voltage. Here we propose a floating-gate memory with a structure of MoS2/hBN/MoS2/graphdiyne oxide/WSe2, in which a threshold switching layer, graphdiyne oxide, instead of a dielectric blocking layer in conventional floating-gate memories, is used to connect the floating gate and control gate. The volatile threshold switching characteristic of graphdiyne oxide allows the direct charge injection from control gate to floating gate by applying a nanosecond voltage pulse (20 ns) with low magnitude (2 V), and restricts the injected charges in floating gate for a long-term retention (10 years) after the pulse. The high operation speed and low voltage endow the device with an ultralow energy consumption of 10 fJ. These results demonstrate a new strategy to develop next-generation high-speed low-energy nonvolatile memory.
  • Cellular automata imbedded memristor-based recirculated logic in-memory computing

    Liu, Yanming; Tian, He; Wu, Fan; Liu, Anhan; Li, Yihao; Sun, Hao; Lanza, Mario; Ren, Tian-Ling (Research Square Platform LLC, 2022-08-05) [Preprint]
    Cellular automata is an important tool to study the emergent properties of complex systems based on its well-known parallel, bio-inspired, computational characteristics. However, running cellular automata on conventional chips suffer from low parallelism, and high hardware cost. Establish dedicated hardware for cellular automata remains elusive. Here, we propose a recirculate logic operations scheme (RLOS) based on memristive hardware combined with 2D transistors to realize cellular automata evolution. The scheme utilizes the storage and calculation characteristics of memristive devices, which greatly reduces hardware complexity. The versatility of the RLOS scheme allows implementing multiple different cellular automata algorithms on the same circuitry. The entire rule (rule 1-254) of elementary cellular automata and more complicated 1D CA model majority classification algorithm have been verified to be applicable to this circuitry. Further, the edge detection algorithm based on 2D cellular automata has been authenticated through RLOS. The experimental and evaluation results reveal that the scheme reduces the hardware cost up to 79 times comparing to the Field Programmable Gate Array (FPGA) approach. To our best knowledge, RLOS has the lowest hardware cost (6 components/per cell) among state-of-art hardware implementations. This work can pave the road towards high-efficiency and low-cost cellular automata hardware realization, and also facilitates the exploration of memristive applications.
  • 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.
  • High Performance Micro Resonators-based Sensors using Multi-Mode Excitation

    Zhao, Wen; Khan, Fahimullah; Alcheikh, Nouha; Younis, Mohammad I. (IEEE Electron Device Letters, Institute of Electrical and Electronics Engineers (IEEE), 2022-08-04) [Article]
    We present a multi-mode excitation technique to significantly amplify the amplitude signal of micro-resonators-based sensors operating at their higher-order modes. We show that the multi-mode excitation can significantly reduce the noise effects, elevate the dynamic response level, and amplify the total amplitude response. We demonstrate the efficiency of the multi-mode excitation to enhance the performance of a gas sensor using electrothermally heated doubly-clamped buckled beams. The results indicate clear amplification for the response at the 2nd mode while detecting Helium compared to a single-source excitation. A 24-times amplitude magnification is achieved. The demonstrated approach provides a promising path to efficiently exploit the higher-order modes of resonant gas sensors leading to improved accuracy and resolution.
  • Single-step post-production treatment of lead acetate precursor-based perovskite using alkylamine salts for reduced grain-boundary related film defects

    Gebremichael, Zekarias Teklu; Alam, Shahidul; Stumpf, Steffi; Diegel, Marco; Schubert, Ulrich S.; Hoppe, Harald (Nano Select, Wiley, 2022-08-04) [Article]
    Powered by the worldwide efforts of research groups experienced in dye-sensitized, and thin-film solar cells, perovskite solar cells (PSCs) reached a power conversion efficiency of 25.7% within 10 years. However, the presence of defects and trap density within the active layer's grain boundaries commonly operates as non-radiative recombination centers. Hence, intensive efforts have been reported to passivate the inevitable bulk and interface defects of the active layer using additives or post-treatment processing to enhance the efficiency and stability of PSCs. Herein, a facile post-treatment strategy based on wet processing methylammonium lead triiodide, MAPbI3 (prepared from lead acetate and methylammonium iodide precursors) films with organic amine salts (FABr and FAI) is demonstrated. As a result, high-quality films of mixed perovskites (FAxMA1-xPbI3-xBrx and FAxMA1-xPbI3) were obtained. The surface treatment has efficiently passivate the defects in the host film, suppressing the non-radiative carrier recombination. Compared to the control device, the increased open-circuit voltage (from 0.5 V to 1 V) and fill factor (FF) values of the optimized device based on FAxMA1-xPbI3 showed a PCE of 16.13%. And our findings revealed that post-treatment is possible on wet perovskite film aged for a few minutes prior to its post-treatment, which saved the energy used for pre-annealing.
  • Origin of Interfacial Charges of Al2o3/Si and Al2o3/Gan Heterogeneous Heterostructures

    Wang, Chuanju; AlQatari, Feras S.; Khandelwal, Vishal; Lin, Rongyu; Li, Xiaohang (Elsevier BV, 2022-08-04) [Preprint]
    Al2O3 is a broadly employed dielectric and significant interfacial charges occur at Al2O3/semiconductor interfaces. However, the charge origin is often unclear that severely impacts device engineering and design. Al2O3/Si and Al2O3/GaN are two of the most common heterogeneous heterostructures (H2s) for many crucial devices including GaN transistors and Si solar cells. While negative charges are extensively observed in Al2O3/Si, positive charges exist in Al2O3/GaN, both of which are not well understood. In this study, we performed in-depth interfacial studies of the Al2O3/Si and Al2O3/GaN H2s to clarify the origin of the interfacial charges. Stoichiometry deviations were found at the interfaces of the two H2s where Al surpasses O for Al2O3/GaN, whereas O dominates at the Al2O3/Si interface. Therefore, we propose that the different interfacial charges are caused by nonstoichiometry atomic ratios of Al2O3 at the interface. The study indicates the important role of the semiconductor surface on the device performance, provide a deep understanding on the origin of interfacial charges at the insulator-semiconductor interfaces.
  • 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.
  • Methane and n-hexane ignition in a newly developed diaphragmless shock tube

    Subburaj, Janardhanraj; Kashif, Touqeer Anwar; Farooq, Aamir (arXiv, 2022-08-03) [Preprint]
    Shock tubes have been routinely used to generate reliable chemical kinetic data for gas-phase chemistry. The conventional diaphragm-rupture mode for shock tube operation presents many challenges that may ultimately affect the quality of chemical kinetics data. Numerous diaphragmless concepts have been developed to overcome the drawbacks of using diaphragms. Most of these diaphragmless designs require significant alterations in the driver section of the shock tube and, in some cases, fail to match the performance of the diaphragm-mode of operation. In the present work, an existing diaphragm-type shock tube is retrofitted with a fast-acting valve, and the performance of the diaphragmless shock tube is evaluated for investigating the ignition of methane and n-hexane. The diaphragmless shock tube reported here presents many advantages, such as eliminating the use of diaphragms, avoiding substantial manual effort during experiments, automating the shock tube facility, having good control over driver conditions, and obtaining good repeatability for reliable gas-phase chemical kinetic studies. Ignition delay time measurements have been performed in the diaphragmless shock tube for three methane mixtures and two n-hexane mixtures at P5 = 10 - 20 bar and T5 = 738 - 1537 K. The results obtained for fuel-rich, fuel-lean, and oxygen-rich (undiluted) mixtures show very good agreement with previously reported experimental data and literature kinetic models (AramcoMech 3.0 [1] for methane and Zhang et al. mechanism [2] for n-hexane). The study presents an easy and simple method to upgrade conventional shock tubes to a diaphragmless mode of operation and opens new possibilities for reliable chemical kinetics investigations.
  • Ocean Warming Amplifies the Effects of Ocean Acidification on Skeletal Mineralogy and Microstructure in the Asterinid Starfish Aquilonastra yairi

    Khalil, Munawar; Doo, Steve S.; Stuhr, Marleen; Westphal, Hildegard (Journal of Marine Science and Engineering, MDPI AG, 2022-08-03) [Article]
    Ocean acidification and ocean warming compromise the capacity of calcifying marine organisms to generate and maintain their skeletons. While many marine calcifying organisms precipitate low-Mg calcite or aragonite, the skeleton of echinoderms consists of more soluble Mg-calcite. To assess the impact of exposure to elevated temperature and increased pCO2 on the skeleton of echinoderms, in particular the mineralogy and microstructure, the starfish Aquilonastra yairi (Echinodermata: Asteroidea) was exposed for 90 days to simulated ocean warming (27 °C and 32 °C) and ocean acidification (455 µatm, 1052 µatm, 2066 µatm) conditions. The results indicate that temperature is the major factor controlling the skeletal Mg (Mg/Ca ratio and Mgnorm ratio), but not for skeletal Sr (Sr/Ca ratio and Srnorm ratio) and skeletal Ca (Canorm ratio) in A. yairi. Nevertheless, inter-individual variability in skeletal Sr and Ca ratios increased with higher temperature. Elevated pCO2 did not induce any statistically significant element alterations of the skeleton in all treatments over the incubation time, but increased pCO2 concentrations might possess an indirect effect on skeletal mineral ratio alteration. The influence of increased pCO2 was more relevant than that of increased temperature on skeletal microstructures. pCO2 as a sole stressor caused alterations on stereom structure and degradation on the skeletal structure of A. yairi, whereas temperature did not; however, skeletons exposed to elevated pCO2 and high temperature show a strongly altered skeleton structure compared to ambient temperature. These results indicate that ocean warming might exacerbate the skeletal maintaining mechanisms of the starfish in a high pCO2 environment and could potentially modify the morphology and functions of the starfish skeleton.
  • 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.
  • High-Performance Spatial Data Compression for Scientific Applications

    Kriemann, Ronald; Ltaief, Hatem; Luong, Minh Bau; Hernandez Perez, Francisco; Im, Hong G.; Keyes, David E. (Springer International Publishing, 2022-08-01) [Book Chapter]
    We implement an efficient data compression algorithm that reduces the memory footprint of spatial datasets generated during scientific simulations. Storing regularly these datasets is typically needed for checkpoint/restart or for post-processing purposes. Our lossy compression approach, codenamed HLRcompress (, combines a hierarchical low-rank approximation technique with binary compression. This novel hybrid method is agnostic to the particular domain of application. We study the impact of HLRcompress on accuracy using synthetic datasets to demonstrate the software capabilities, including robustness and versatility. We assess different algebraic compression methods and report performance results on various parallel architectures. We then integrate it into a workflow of a direct numerical simulation solver for turbulent combustion on distributed-memory systems. We compress the generated snapshots during time integration using accuracy thresholds for each individual chemical species, without degrading the practical accuracy of the overall pressure and temperature. We eventually compare against state-of-the-art compression software. Our implementation achieves on average greater than 100-fold compression of the original size of the datasets.
  • The Kalaotoa Fault: A Newly Identified Fault that Generated the Mw 7.3 Flores Sea Earthquake

    Supendi, Pepen; Rawlinson, Nicholas; Prayitno, Bambang Setiyo; Widiyantoro, Sri; Simanjuntak, Andrean; Palgunadi, Kadek Hendrawan; Kurniawan, Andri; Marliyani, Gayatri Indah; Nugraha, Andri Dian; Daryono, Daryono; Anugrah, Suci Dewi; Fatchurochman, Iman; Gunawan, Mohammad Taufik; Sadly, Muhammad; Adi, Suko Prayitno; Karnawati, Dwikorita; Arimuko, Abraham (The Seismic Record, Seismological Society of America (SSA), 2022-08-01) [Article]
    We reveal the existence of a previously unknown fault that generated the Mw 7.3 Flores Sea earthquake, which occurred on 14 December 2021, approximately 100 km to the north of Flores Island, in one of the most complex tectonic settings in Indonesia. We use a double-difference method to relocate the hypocenters of the mainshock and aftershocks, determine focal mechanisms using waveform inversion, and then analyze stress changes to estimate the fault type and stress transfer. Our relocated hypocenters show that this earthquake sequence ruptured on at least three segments: the source mechanism of the mainshock exhibits dextral strike-slip motion (strike N72°W and dip 78° NE) on a west–east-trending fault that we call the Kalaotoa fault, whereas rupture of the other two segments located to the west and east of the mainshock (striking west-northwest and southeast, respectively) may have been triggered by this earthquake. The Coulomb stress change imparted by the rupture of these segments on nearby faults is investigated, with a focus on regions that experience a stress increase with few associated aftershocks. Of particular interest are stress increases on the central back-arc thrust just north of Flores and the north–south-striking Selayar fault in the northwest of our study region, both of which may be at increased risk of failure as a result of this unusual earthquake sequence.
  • Optical and interfacial characteristics of a heterojunction between (2¯01)-oriented single-domain β-(In0.072Ga0.928)2O3 and α-Al2O3 crystals

    Alfaraj, Nasir; Li, Kuang-Hui; Braic, Laurentiu; Hedhili, Mohamed N.; Guo, Zaibing; Ng, Tien Khee; Ooi, Boon S. (Optical Materials Express, Optica Publishing Group, 2022-08-01) [Article]
    In this article, we determine the band alignment at the thermodynamically stable heterointerface between a (2¯01)-oriented single-domain β-(In0.072Ga0.928)2O3 crystal and bulk c-plane sapphire, namely, (0001)-oriented α-Al2O3. The β-(In0.072Ga0.928)2O3 layer was deposited on the bulk sapphire crystal using pulsed laser deposition. The β-(In0.072Ga0.928)2O3 and α-Al2O3 valence and conduction band offsets (VBO and CBO, respectively) were found to be 0 ± 0.1 and 4.87 ± 0.1 eV, respectively. Accordingly, we identified a type-I α-Al2O3/β-(In0.072Ga0.928)2O3 heterojunction. X-ray diffraction measurements confirmed (2¯01)-oriented single-domain β-(In0.072Ga0.928)2O3 high-quality films with in-plane rotations of every 120∘, whereas Rutherford backscattering spectrometry was employed to verify the bulk composition. We employed high-resolution X-ray photoelectron spectroscopy to measure the core level binding energies of Al 2p and Ga 2p3/2 with respect to the valence band maxima of the β-(In0.072Ga0.928)2O3 and α-Al2O3 layers, respectively. Then, we measured the energy separation between the Al 2p and Ga 2p3/2 core levels at the interface of the heterojunction. β-(InGa)2O3 is a wide-bandgap semiconductor, while α-Al2O3 is a well-known dielectric. Together, they can be employed to fabricate reliable and efficient power electronic devices. We also combined high-resolution transmission electron microscopy, X-ray diffraction, and fast Fourier transform algorithms to characterize the dislocations at the interface.
  • Techno-economic performance optimization of hydrothermal doublet systems: Application to the Al Wajh basin, Western Saudi Arabia

    Ezekiel, Justin; Ebigbo, Anozie; Arifianto, Indra; Daniilidis, Alexandros; Finkbeiner, Thomas; Mai, Paul Martin (Geothermics, Elsevier BV, 2022-07-30) [Article]
    The Kingdom of Saudi Arabia (KSA) has vast geothermal energy resources. When developed, these markedly strengthen the country's goals of achieving a carbon-neutral economy. To demonstrate the feasibility and techno-economic performance of small-scale, hydrothermal well doublet systems for direct use in KSA, we perform reservoir and wellbore flow and heat-transport simulations as well as an economic analysis. The maximum permissible flowrate is constrained to avoid thermoelastic fracturing in the near-wellbore region. Reservoir conditions of a sedimentary basin along the Red Sea coast (near Al Wajh) provide an ideal study case to which we add economic parameters considered representative for KSA. We derive a Levelized Cost of Heat (LCOH) ranging from 49 to 128 $/MWh for 50-mD hydrothermal doublet systems with an optimal well spacing of 600 m and a flowrate ranging from 110 kg/s to 50 kg/s. LCOH is strongly influenced by decreasing reservoir transmissivity. Also, a minimum injection temperature is required to avoid thermoelastic fracturing. Our economic analysis further highlights that capacity factor and well-drilling cost have the greatest impact on LCOH. Thus, this study provides a guide and workflow to conduct techno-economic investigations for decision-making, risk mitigation, optimizing geothermal-energy-extraction and economic-performance conditions of hydrothermal doublet systems.
  • Unblocking Ion-occluded Pore Channels in Poly(triazine imide) Framework for Proton Conduction

    Chi, Heng-Yu; Chen, Cailing; Zhao, Kangning; Villalobos, Luis Francisco; Schouwink, Pascal Alexander; Piveteau, Laura; Marshall, Kenneth Paul; Liu, Qi; Han, Yu; Agrawal, Kumar Varoon (Angewandte Chemie (International ed. in English), 2022-07-30) [Article]
    Poly(triazine imide) or PTI is an ordered graphitic carbon nitride hosting Å-scale pores attractive for selective molecular transport. AA'-stacked PTI layers are synthesized by ionothermal route during which ions occupy the framework and occlude the pores. Synthesis of ion-free PTI hosting AB-stacked layers has been reported, however, pores in this configuration are blocked by the neighboring layer. The unavailability of open pore limits application of PTI in molecular transport. Herein, we demonstrate acid treatment for ion depletion which maintains AA' stacking and results in open pore structure. We provide first direct evidence of ion-depleted open pores by imaging with the atomic resolution using integrated differential phase-contrast scanning transmission electron microscopy. Depending on the extent of ion-exchange, AA' stacking with open channels and AB stacking with closed channels are obtained and imaged for the first time. The accessibility of open channels is demonstrated by enhanced proton transport through ion depleted PTI.
  • 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.
  • Electrical manipulation of magnetization in magnetic heterostructures with perpendicular anisotropy

    Chen, Aitian; Zheng, Dongxing; Fang, Bin; Wen, Yan; Li, Yan; Zhang, Xixiang (Journal of Magnetism and Magnetic Materials, Elsevier BV, 2022-07-28) [Article]
    Magnetic materials with perpendicular magnetic anisotropy are significant for spintronics due to their potential to develop high-density magnetic memory with high thermal stability. Many methods have developed to manipulate perpendicular magnetization by electric current or electric field rather than magnetic field for realizing energy-efficient spintronics. In this review, we primarily focus on recent progress on electrical manipulation of perpendicular magnetization through spin-orbit torque and strain-mediated magnetoelectric coupling. We aim to summarize field-free switching of perpendicular magnetization and exchange bias induced by spin-orbit torque in the metallic magnetic heterostructures, spin-orbit torque switching of magnetization in the perovskite oxides, and magnetoelectric control of perpendicular magnetization mediated by piezostrain in multiferroic heterostructures. Finally, our perspectives on electrical manipulation of perpendicular magnetization by spin-orbit torque and magnetoelectric coupling are given to realize practical energy-efficient spintronic devices.
  • Xeno-pumice from Harrat Rahat: Understanding magma-crust interaction

    Garcia, Evelyn R. Garcia Paredes (2022-07-28) [Thesis]
    Advisor: Van der Zwan, Froukje M.
    Committee members: Jonsson, Sigurjon; Troll, Valentin R; van Buchem, Frans
    “Xeno-pumice” describes a pumice-like material, high in silica content and vesiculation, found as a xenolith in a more mafic rock. A xeno-pumice is an indicator of magma-crust interaction; however, the origin, nature, and processes behind this xenolith are still debated. Xeno-pumice has been described in a few places worldwide, including the Canary Islands in Spain, Indonesia, Iceland, the USA, Chile and Mexico. This thesis, for the first time, presents and analyzes the mineralogy, textural features, whole-rock geochemistry (major and trace element), and oxygen isotopes of xeno-pumice samples found in Harrat Rahat, Saudi Arabia. Harrat Rahat is a volcanic field whose last eruption was in 1256A.D. and reached the outskirts of Madinah, one of the main cities in Saudi Arabia. Harrat Rahat is characterized by a wide range of volcanic products: from basalts to trachyte. Previous studies suggested that this chemical variation has its source in the mantle and minor crustal contamination; however, the xeno-pumice samples found indicate magma-crust interaction. Thus, in this thesis, the crust-melt interaction hypothesis is addressed as a process that could modify the composition of the melt and thus the resulting volcanic products and eruptive style of the volcanic field. Indeed, the chemistry and oxygen isotope values of the studied volcanic rocks show a variation in composition, which is suggested to be the consequence of crust-melt interaction. The petrology, chemistry and oxygen isotope values suggest that the melt interacted with either the metamorphosed plutonic portion of the upper Arabian crust or with (meta-) sediments below Harrat Rahat. Finally, this thesis proved that magma-crust interaction occurred at Harrat Rahat, which has important implications for interpreting eruption mechanisms and mantle sources.

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