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  • Pt–Fe Nanoparticles Dispersed on Mesoporous Silica as Selective Catalysts for Dehydrogenation of Isobutane

    Rodriguez Gomez, Alberto; Ould-Chikh, Samy; Henao, Wilson; Agostini, Giovanni; Prieto, Gonzalo; Gascon, Jorge (ACS Applied Nano Materials, American Chemical Society (ACS), 2023-10-02) [Article]
    A series of catalysts composed of Pt–Fe nanoparticles supported on mesoporous silica SBA-15 (ca. 7 nm pore diameter) have been prepared by ultrasound-assisted coimpregnation of the metal precursors and evaluated in the nonoxidative dehydrogenation of isobutane. Prereduced catalytic systems were characterized by STEM-HAADF + EDS mapping and XAS to determine the chemical environment of the highly dispersed platinum active sites on the iron host matrix. While the monometallic platinum (nanoparticles) supported on SBA-15 material presented a rapid catalyst deactivation under reaction conditions, coordinatively unsaturated Pt–Fe (Pt ≪ Fe) sites located in the mesopores of SBA-15 showed a high steady-state activity (43% conversion) and selectivity (96% to isobutylene) in the dehydrogenation of isobutane at 550 °C for several hours. Temperature-programmed reduction profiles determined not only the substantially higher reducibility of FeOx species with doping amounts of platinum in the as-prepared (calcined) catalysts but also the detrimental structural changes undergone after consecutive reaction–regeneration cycles. Finally, reactivation under controlled conditions allows to minimize irreversible catalyst deactivation after successive cycles.
  • Face-directed assembly of tailored isoreticular MOFs using centring structure-directing agents

    Barsukova, Marina O.; Sapianik, Aleksandr A.; Guillerm, Vincent; Shkurenko, Aleksander; Shaikh, Aslam; Parvatkar, Prakash Tukaram; Bhatt, Prashant; Bonneau, Mickaele; Alhaji, Abdulhadi; Shekhah, Osama; Balestra, Salvador R. G.; Semino, Rocio; Maurin, Guillaume; Eddaoudi, Mohamed (Nature Synthesis, Springer Science and Business Media LLC, 2023-10-02) [Article]
    Building blocks with low connectivity and no embedded directionality are prone to polymorphism, as demonstrated by the diversity of 4-connected zeolitic nets (>250). As a result, their deployment for design in reticular and isoreticular chemistries remains a challenge. However, the ability to control geometrical peculiarities offers potential to deviate from the assembly of default structures. Here we report the face-directed assembly of >20 isoreticular zeolite-like metal–organic frameworks (ZMOFs) by using polytopic expanding and tightening centring structure-directing agents (cSDAs). The cSDAs are selected with the appropriate geometrical coding information to alter and control the orientation of adjacent supermolecular building blocks. The ZMOFs have an underlying sodalite (sod) topology that is remarkably suited for the rational assembly of multinary materials. In addition to a variety of metal cations (In, Fe, Co and Ni), a diverse range of cSDAs (di-, tri-, tetra-, hexa-, pyridyl or imidazole) are used and combined. Our approach enables isoreticular possibilities at both extremities of the porous materials spectrum: In-sod-ZMOF-102 exhibits small pore aperture suitable for efficient separation, while Fe-sod-ZMOF-320 with 48-Å-wide mesopores exhibits high hydrogen uptake, methane storage working capacity and a high gravimetric working capacity for oxygen.
  • Enhancing the Accuracy of Physics-Informed Neural Network Surrogates in Flash Calculations Using Sparse Grid Guidance

    Wu, Yuanqing; Sun, Shuyu (Elsevier BV, 2023-09-30) [Preprint]
    Flash calculations pose a significant performance bottleneck in compositional-flow simulations. While sparse grids have helped mitigate this bottleneck by shifting it to the offline stage, the accuracy of the surrogate model based on physics-informed neural networks (PINN) is still inferior to that of the sparse grid surrogate in many cases. To address this issue, we propose the sparse-grid guided PINN training algorithm. This approach involves rearranging the collocation points using sparse grids at each epoch to capture changes in the residual space. By doing so, the PINN surrogate achieves the required accuracy using the fewest collocation points possible, thereby avoiding potential performance bottlenecks. Moreover, the training time complexity of the sparse-grid guided PINN training is significantly lower compared to the normal training while maintaining the same level of accuracy. Consequently, the sparse-grid guided PINN training method enhances the accuracy of the PINN surrogate with minimal computational overhead.
  • A Tunable Micromachined Multithreshold Inertial Switch

    Xu, Qiu; Alahmdi, Raed L.; Wang, Lvjun; Rocha, Rodrigo Tumolin; Younis, Mohammad I. (IEEE/ASME Transactions on Mechatronics, Institute of Electrical and Electronics Engineers (IEEE), 2023-09-29) [Article]
    In this article, we present a multithreshold microelectromechanical tunable inertial switch. The device aims to provide quantitative information on acceleration while retaining the attractive energy-saving features of binary threshold switches. The designed proof-of-concept device with three thresholds is composed of four serpentine springs, a suspended proof mass, and three stationary electrodes placed at various positions in the sensing direction. In addition, the tunability of the acceleration threshold is demonstrated based on the softening effect of the electrostatic force. The dynamic behavior of the switch is investigated analytically. Results are shown for the relationship between the bias voltage and tunable threshold. The fabricated switch prototypes are tested using a drop-table shock system. The test results demonstrate that the multithreshold switch can detect an acceleration range of 131–400 g. The simulated and analytical results are in good agreement with the experimental data. The demonstrated device concept is promising to categorize the shock impact for several applications, such as for head impact and brain injuries.
  • Design Criteria for Silicon Solar Cells with Fill Factors Approaching the Auger Limit

    Razzaq, Arsalan; Allen, Thomas; De Wolf, Stefaan (ACS Energy Letters, American Chemical Society (ACS), 2023-09-29) [Article]
    We establish, via a systematic simulation study, the minimum requirements for the electrical design parameters to accomplish fill factors above 86% in crystalline-silicon solar cells.
  • Developing a data-driven modeling framework for simulating a chemical accident in freshwater

    Kim, Soobin; Abbas, Ather; Pyo, Jong Choel; Kim, Hyein; Hong, Seok Min; Baek, Sang Soo; Cho, Kyung Hwa (Journal of Cleaner Production, Elsevier BV, 2023-09-29) [Article]
    Chemical accidents in freshwater pose threats to public health and aquatic ecosystems. Process-based models (PBMs) have been used to identify spatiotemporal chemical distributions in natural water. However, their computationally expensive simulations can hinder timely incident responses, which are crucial for minimizing negative impacts. Therefore, this study proposes a site-specific data-driven model (DDM) to supplement PBM-based chemical accident simulations. A convolutional neural network (CNN) was employed as the DDM because of its outstanding performance in capturing spatial patterns. Our model was developed to facilitate chemical accident simulations in the Namhan River, South Korea. The model datasets were generated using the PBM simulation outputs from toluene accident scenarios. Our DDM showed a Nash-Sutcliffe-efficiency of 0.94 and a root-mean-square-error of 0.023 μg/L for the validation set. Its computational time was approximately 64 times faster than that of PBMs. In addition, this study interpreted the DDM results using SHapley Additive exPlanations (SHAP). The SHAP findings highlighted the influential role of distance from the accident site in this study. Overall, this study demonstrated the applicability of our modeling approach in freshwater chemical accidents by providing rapid spatial distribution results complementing PBM simulations.
  • Chemiluminescence- and machine learning-based monitoring of premixed ammonia-methane-air flames

    Guiberti, Thibault; Shohdy, Nader N.; Cardona, Santiago; Zhu, Xuren; Selle, Laurent; Lapeyre, Corentin J. (Applications in Energy and Combustion Science, Elsevier BV, 2023-09-29) [Article]
    This work presents the development and validation of an algorithm capable of predicting the equivalence ratio and the ammonia fraction of premixed ammonia-methane-air flames using only measured OH*, NH*, CN*, and CH* chemiluminescence intensities as input. This machine learning algorithm relies on Gaussian process regression (GPR). It was trained and validated with data previously recorded in laminar flames, and it was then tested with new data recorded in more practical, turbulent swirl flames. The algorithm performs well for laminar and turbulent flames for wide ranges of equivalence ratio (0.80 ≤ ϕ ≤ 1.20) and ammonia fraction (0 ≤ XNH3 ≤ 0.60). For turbulent swirl flames, the prediction errors in the equivalence ratio and on the ammonia fraction are smaller than 0.05, except for a very small subset of operating conditions where the error is up to 0.10. Additional tests were performed by adding NO* and CO2* to the list of inputs, but this did not improve the predictions. The GPR algorithm was then benchmarked against linear and polynomial regressions and a more conventional way of inferring flame properties from chemiluminescence measurements, namely the ratio-based method. This method relies only on CN*/NO* and NH*/CH* ratios to predict the equivalence ratio and the ammonia fraction. Its prediction errors were often larger than 0.15, which is significantly worse than that of the GPR algorithm. Consequently, this work constitutes a solid basis for the future development of non-intrusive sensors to monitor practical ammonia-methane-air flames.
  • Design and Performance Assessment of an Experimental Rig to Conduct Material Nitridation Studies at Extreme Ammonia Conditions

    Laws, Nicole; Campuzano, Felipe; Dawood, Ziad; Roberts, William L. (American Society of Mechanical Engineers, 2023-09-28) [Conference Paper]
    This work presents the design and assessment of an experimental rig intended to carry out material sustainability studies in ammonia (NH3) environments. The designed facility aims at furthering the understanding of the nitridation potential of NH3 under extreme conditions, particularly at both high pressure and high temperature, when interacting with varying materials of interest. Several key factors were considered during the design process, including a system capable of operating at high pressures (up to 30 bar) and temperatures (up to 800 °C), the possibility of maintaining a continuous NH3 flow to increase the nitridation potential of the atmosphere, the flexibility of accommodating between 60 to 70 metal samples, and the design of a suitable system to operate continuously for hundreds of hours (up to 1000 hours in total). A facility achieving those features involved the development and optimization of three main subsystems such as a liquefied NH3 feeding system, a high-pressure/temperature rig, and an abatement system. Altogether these guarantee safe and continuous operation for long periods of time at the desired experimental conditions. Finally, several tests were conducted to assess the reproducibility and stability of the designed facility, including temperature and pressure profiles, and NH3 concentration gradients in the rig.
  • Dipeptide-Based Photoreactive Instant Glue for Environmental and Biomedical Applications.

    Bilalis, Panagiotis; Alrashoudi, Abdulelah Α; Susapto, Hepi Hari; Moretti, Manola; Alshehri, Salwa; Abdelrahman, Sherin; Elsakran, Amr; Hauser, Charlotte (ACS applied materials & interfaces, American Chemical Society (ACS), 2023-09-28) [Article]
    Nature-inspired smart materials offer numerous advantages over environmental friendliness and efficiency. Emulating the excellent adhesive properties of mussels foot proteins, where the lysine is in close proximity with the 3,4-dihydroxy-l-phenylalanine (DOPA), we report the synthesis of a novel photocurable peptide-based adhesive consisting exclusively of these two amino acids. Our adhesive is a highly concentrated aqueous solution of a monomer, a cross-linker, and a photoinitiator. Lap-shear adhesion measurements on plastic and glass surfaces and comparison with different types of commercial adhesives showed that the adhesive strength of our glue is comparable when applied in air and superior when used underwater. No toxicity of our adhesive was observed when the cytocompatibility on human dermal fibroblast cells was assessed. Preliminary experiments with various tissues and coral fragments showed that our adhesive could be applied to wound healing and coral reef restoration. Given the convenience of the facile synthesis, biocompatibility, ease of application underwater, and high adhesive strength, we expect that our adhesive may find application, but not limited, to the biomedical and environmental field.
  • Enhanced optoelectronic coupling for perovskite-silicon tandem solar cells

    Aydin, Erkan; Ugur, Esma; Yıldırım, Bumin Kağan; Allen, Thomas; Dally, Pia; Razzaq, Arsalan; Cao, Fangfang; Xu, Lujia; Vishal, Badri; Yazmaciyan, Aren; Said, Ahmed; Zhumagali, Shynggys; Azmi, Randi; Babics, Maxime; Fell, Andreas; Xiao, Chuanxiao; De Wolf, Stefaan (Nature, Springer Science and Business Media LLC, 2023-09-28) [Article]
    Monolithic perovskite/silicon tandem solar cells are of great appeal as they promise high power conversion efficiencies (PCEs) at affordable cost. In state-of-the-art tandems, the perovskite top cell is electrically coupled to a silicon heterojunction bottom cell via a self-assembled monolayer (SAM), anchored on a transparent conductive oxide (TCO), which enables efficient charge transfer between the subcells.1-3 Yet, reproducible high-performance tandem solar cells require energetically homogenous SAM coverage, which remains challenging, especially on textured silicon bottom cells. Here, we resolve this issue by employing ultrathin (5 nm) amorphous indium zinc oxide (IZO) as the interconnecting TCO, exploiting its high surface-potential homogeneity resulting from the absence of crystal grains, and higher density of SAM anchoring sites when compared to commonly employed crystalline TCOs. Combined with optical enhancements via equally thin IZO rear electrodes and improved front contact stacks, an independently certified PCE of 32.5% was obtained, which ranks amongst the highest for perovskite/silicon tandems. Our ultrathin transparent contact approach reduces indium consumption by approximately 80%, which is of importance towards sustainable PV manufacturing.
  • High potential for biomass-degrading CAZymes revealed by pine forest soil metagenomics

    Kumari, Sonam; Leon Magdaleno, Jorge S.; Grewal, Ravneet Kaur; Narsing Rao, Manik Prabhu; Rajjak Shaikh, Abdul; Cavallo, Luigi; Chawla, Mohit; Kumar, Manoj (Journal of Biomolecular Structure and Dynamics, Informa UK Limited, 2023-09-28) [Article]
    The undisturbed environment in Netarhat, with its high levels of accumulated lignocellulosic biomass, presents an opportunity to identify microbes for biomass digestion. This study focuses on the bioprospecting of native soil microbes from the Netarhat forest in Jharkhand, India, with the potential for lignocellulosic substrate digestion. These biocatalysts could help overcome the bottleneck of biomass saccharification and reduce the overall cost of biofuel production, replacing harmful fossil fuels. The study used metagenomic analysis of pine forest soil via whole genome shotgun sequencing, revealing that most of the reads matched with the bacterial species, very low percentage of reads (0.1%) belongs to fungal species, with 13% of unclassified reads. Actinobacteria were found to be predominant among the bacterial species. MetaErg annotation identified 11,830 protein family genes and 2 metabolic marker genes in the soil samples. Based on the Carbohydrate Active EnZyme (CAZy) database, 3,996 carbohydrate enzyme families were identified, with family Glycosyl hydrolase (GH) dominating with 1,704 genes. Most observed GH families in the study were GH0, 3, 5, 6. 9, 12. 13, 15, 16, 39, 43, 57, and 97. Modelling analysis of a representative GH 43 gene suggested a strong affinity for cellulose than xylan. This study highlights the lignocellulosic digestion potential of the native microfauna of the lesser-known pine forest of Netarhat.
  • An Experimental Study of the Stability and Nearfield Structure of Oxyfuel Jet Flames at Elevated Pressures

    Bukar, Muhammad; Basnet, Suman; Wu, Bin; Magnotti, Gaetano (American Society of Mechanical Engineers, 2023-09-28) [Conference Paper]
    This study presents experimental results of the stability limit and the nearfield structure of oxy-methane jet flames at pressures ranging from 2–5 bar. The oxidizer used in this campaign consists of 40% O2 and 60% CO2. Two sets of cases were studied: one where pressure increase was achieved by keeping the fuel Reynolds number constant and the other where the velocity was kept constant while increasing pressure. Stability limits (lift-off velocity) are reported for various coflow velocities at different operating pressures. Natural flame luminosity imaging with a DSLR camera and combined CH* chemiluminescence using an ICCD (PIMAX 4) are used to characterize the nearfield structure of the flame. The CH* results were then processed to extract the attachment location, defined in terms of attachment height and radius. The study mainly investigates the effect of pressure on the flame attachment height and radius. The DSLR images complement the study with qualitative information on the flame appearance and sooting propensity. Results show that at constant Reynolds number, the attachment height decreases with pressure for all cases considered while the attachment radius increased with pressure increase. At constant velocity, however, both the attachment height and radius were observed to decrease with increased pressure.
  • Wafer-Scale Memristor Array Based on Aligned Grain Boundaries of 2D Molybdenum Ditelluride for Application to Artificial Synapses

    Yang, Jihoon; Yoon, Aram; Lee, Donghyun; Song, Seunguk; Jung, IL John; Lim, Dong-Hyeok; Jeong, Hongsik; Lee, Zonghoon; Lanza, Mario; Kwon, Soon-Yong (Advanced Functional Materials, Wiley, 2023-09-27) [Article]
    2D materials have attracted attention in the field of neuromorphic computing applications, demonstrating the potential for their use in low-power synaptic devices at the atomic scale. However, synthetic 2D materials contain randomly distributed intrinsic defects and exhibit a stochasitc forming process, which results in variability of switching voltages, times, and stat resistances, as well as poor synaptic plasticity. Here, this work reports the wafer-scale synthesis of highly polycrystalline semiconducting 2H-phase molybdenum ditelluride (2H-MoTe2) and its use for fabricating crossbar arrays of memristors. The 2H-MoTe2 films contain small grains (≈30 nm) separated by vertically aligned grain boundaries (GBs). These aligned GBs provide confined diffusion paths for metal ions filtration (from the electrodes), resulting in reliable resistive switching (RS) due to conductive filament confinement. As a result, the polycrystalline 2H-MoTe2 memristors shows improvement in the RS uniformity and stable multilevel resistance states, small cycle-to-cycle variation (<8.3%), high yield (>83.7%), and long retention times (>104 s). Finally, 2H-MoTe2 memristors show linear analog synaptic plasticity under more than 2500 repeatable pulses and a simulation-based learning accuracy of 96.05% for image classification, which is the first analog synapse behavior reported for 2D MoTe2 based memristors.
  • Effect of oxygen enrichment on methane ignition

    Kashif, Touqeer Anwar; AlAbbad, Mohammed A.; Figueroa Labastida, Miguel; Chatakonda, Obulesu; Kloosterman, Jeffrey; Middaugh, Joshua; Sarathy, Mani; Farooq, Aamir (Combustion and Flame, Elsevier BV, 2023-09-27) [Article]
    Oxygen-enriched combustion has attracted interest in the energy sector due to its increased thermal efficiency and low carbon capture cost compared to ‘air’ combustion. Experimental data on the ignition of oxygen-enriched mixtures are limited in literature. In this work, ignition delay times (IDTs) of various methane/oxygen mixtures diluted in argon/nitrogen were measured using a low- and a high-pressure shock tube over a temperature range of 1200 – 1700 K, three pressures of 1, 10, and 20 bar and an equivalence ratio range of 0.21 - 4. The oxygen mole fraction in the mixtures was varied from 19% (‘air’) to 90.5%, and dilution levels from 71% to zero. The reported IDTs were extracted from pressure and OH* emission profiles. To the best of our knowledge, this is the first comprehensive IDT study on the effect of oxygen enrichment on methane ignition. High-speed imaging experiments were performed to determine the possible presence of non-ideal ignition in these unconventional mixtures. The Bifurcation Damköhler number was found to be a good indicator of non-ideal ignition observed in some imaging experiments. Measured IDTs were compared with the predictions of AramcoMech 3.0 model as well as with GRIMech 3.0 and NUIGMech 1.1 for few cases. In general, AramcoMech 3.0 overestimated IDTs for the investigated methane mixtures. Brute force sensitivity analyses were conducted with AramcoMech 3.0 to identify reactions with a strong influence on IDT prediction for the investigated mixtures. Minor modifications were made to AramcoMech 3.0 resulting in improved predictions of ignition behavior in oxygen-enriched methane mixtures.
  • In situ preparation and determination of CeO2 high-index surface atomic structures

    Zou, Chen; Li, Guanxing; Zhang, Kai; Han, Zhong Kang; Jiang, Ying; Yuan, Wentao; Yang, Hangsheng; Zhang, Ze; Wang, Yong (Materials Today Nano, Elsevier BV, 2023-09-27) [Article]
    Understanding the properties regarding the high-index surfaces of the oxide nanocrystals is of great importance, but it remains challenging to obtain atomic-level information due to the lack of efficient preparation methods for high-index surfaces. Herein, we presented a work to in situ prepare and determine the intrinsic atomic structures of nanocrystalline CeO2 high-index surfaces via in situ spherical aberration (Cs)-corrected scanning transmission electron microscopy (STEM). By utilizing a reshaping process driven by the Wulff reconstruction, high-index surfaces of CeO2 nanocrystals including {210} {311}, and {533} were successfully prepared. Combined STEM with the density functional theory calculations, these high-index surface structures were determined with atomic precision, and interestingly {533} exhibited a unique atomic pit feature with low-coordinated Ce atoms exposure and unique electrical properties. This work has revealed new information about CeO2 high-index surfaces through experiments, enhancing our understanding of these surfaces, and also providing a new route for preparing high-index surfaces.
  • Energy-efficient electrochemical recovery of gold enabled by a thiourea-based electrolyte system

    Son, Jieun; Han, Jong In; Hong, Yeongran; Yavuz, Cafer T. (Journal of Environmental Chemical Engineering, Elsevier BV, 2023-09-26) [Article]
    The application of non-cyanide baths in electroplating for gold recovery has drawn significant attention due to their clear benefits on the environment and human health. Among these alternatives, thiourea has emerged as a promising non-cyanide bath, and yet high energy and reagent consumption has impeded its widespread adoption. Herein, an energy-efficient gold recovery process via electroplating was developed to reduce bath depletion. The redox potentials of gold deposition using thiourea electrolyte were examined through linear sweep voltammetry, and the consumed energy during the electrochemical plating of gold was quantified. The gold deposition was achieved in the two-electrode system enabling a 97% recovery under 0.3 V of the cell voltage. The proposed system exhibited a significant reduction in energy consumption to 0.129 kWh∙kg−1, implying that the oxidation of free thiourea on the anode mainly contributed to the decrease in the applied voltage and energy. Furthermore, the suppression of the bath consumption was evaluated compared with electroless plating, another reliable deposition process, throughout monitoring gold desorption and deposition efficiencies during the cyclic use of thiourea. The retardation of the sorbent consumption was observed in the electroplating during the consecutive cycles, which inferred that the reduction of its oxidized form, formamidine disulfide, led to the regeneration of the agent on the cathode. Thus, the suggested electroplating process with a gold-thiourea bath shows great potential as a workable means of gold recovery from an economic standpoint with its low energy and sorbent consumption to realize the commercialization of urban mining in the electronic industry.
  • An energy-stable and conservative numerical method for multicomponent Maxwell–Stefan model with rock compressibility

    Kou, Jisheng; Wang, Xiuhua; Chen, Huangxin; Sun, Shuyu (Physics of Fluids, AIP Publishing, 2023-09-26) [Article]
    Numerical simulation of gas flow in porous media is becoming increasingly attractive due to its importance in shale and natural gas production and carbon dioxide sequestration. In this paper, taking molar densities as the primary unknowns rather than the pressure and molar fractions, we propose an alternative formulation of multicomponent Maxwell–Stefan (MS) model with rock compressibility. Benefiting from the definitions of gas and solid free energies, this MS formulation has a distinct feature that it follows an energy dissipation law, and namely, it is consistent with the second law of thermodynamics. Additionally, the formulation obeys the famous Onsager's reciprocal principle. An efficient energy-stable numerical scheme is constructed using the stabilized energy factorization approach for the Helmholtz free energy density and certain carefully designed formulations involving explicit and implicit mixed treatments for the coupling between molar densities, pressure, and porosity. We rigorously prove that the scheme inherits the energy dissipation law at the discrete level. The fully discrete scheme has the ability to ensure the mass conservation law for each component as well as preserve the Onsager's reciprocal principle. Numerical tests are conducted to verify our theories, and in particular, to demonstrate the good performance of the proposed scheme in energy stability and mass conservation as expected from our theories.
  • ZnFe2O4 Nanoparticles for Gas-Sensing Applications: Monitoring of Structural Parameters while Exposing the Ferrite in Gas Atmospheres

    Abdulhamid, Zeyad M.; Dabbawala, Aasif A.; Delclos, Thomas; Straubinger, Rainer; Rueping, Magnus; Polychronopoulou, Kyriaki; Anjum, Dalaver H. (Research Square Platform LLC, 2023-09-26) [Preprint]
    ZnFe2O4 materials are promising for several applications, including catalysis, sensors, and supercapacitors. This paper presents a hydrothermal-based facile method for synthesizing ZnFe2O4, whose size can be controlled with the concentration of sodium acetate used as a fuel. The characterization of the morphology, structure, composition, and electronic properties of the synthesized samples is also presented in this paper. The crystal structure of the synthesized samples was determined using an X-ray Diffractometer (XRD). The results revealed fluctuations in the size, lattice parameter, and strain in the nanoparticles with increasing the concentration of sodium acetate fuel. Field-Emission Scanning Electron Microscopy (FESEM) was used to determine the morphology and elemental composition of synthesized materials, and it revealed that the particles in synthesized samples possessed approximately spherical morphology whose size decreased significantly with the increasing amount of sodium acetate. Transmission Electron Microscopy (TEM) was utilized to determine the structure, morphology, and elemental distributions in particles at the nanoscale, and it confirmed the findings of XRD and FESEM analyses. The high-resolution TEM (HRTEM) imaging analysis of the nanoparticles in samples revealed that the particles predominantly possessed (001) type facets. X-ray photoelectron spectroscopy (XPS) and core-loss electron energy loss spectroscopy (EELS) showed an increasing fraction of Fe2+ with the decreasing size of the particles in samples. The Brunauer, Emmett, and Tellers (BET) analysis of samples revealed a higher surface area as the particle size decreases. In addition, the determined surface area and pore size values are compared with the literature, and it was found that the synthesized materials are promising for gas-sensing and supercapacitor applications. The ab initio calculations of the Density of States (DOS) and Band structure of (001) surface terminating ZnFe2O4 particles were carried out using Quantum Espresso software to determine the bandgap of the synthesized samples. They were compared to the experimentally determined bandgap values for the corresponding samples. Finally, in-situ TEM measurement was carried out on one sample and revealed that the d-spacing of ZnFe2O4 NPs showed a noticeable fluctuation reaching more than 5% upon exposure to CO2 and Ar gases. It is concluded from the presented study that the reduction in the size of the nanoparticles provides more active sites due to a higher concentration of oxygen vacancies and tunes the bandgap.
  • A Novel Organic Phosphonate Additive Induced Stable and Efficient Perovskite Solar Cells with Efficiency over 24% Enabled by Synergetic Crystallization Promotion and Defect Passivation.

    Cheng, Caidong; Yao, Yiguo; Li, Lei; Zhao, Qiangqiang; Zhang, Chenyang; Zhong, Xiuzun; Zhang, Qi; Gao, Yajun; Wang, Kai (Nano letters, 2023-09-25) [Article]
    Defect passivation is crucial to enhancing the performance of perovskite solar cells (PSCs). In this study, we successfully synthesized a novel organic compound named DPPO, which consists of a double phosphonate group. Subsequently, we incorporated DPPO into a perovskite solution. The presence of a P═O group interacting with undercoordinated Pb2+ yielded a perovskite film of superior crystallinity, greater crystal orientation, and smoother surface. Additionally, the addition of DPPO can passivate defect states and enhance upper layer energy level alignment, which will improve carrier extraction and prevent nonradiative recombination. Consequently, an impressive champion efficiency of 24.24% was achieved with a minimized hysteresis. Furthermore, the DPPO-modified PSCs exhibit enhanced durability when exposed to ambient conditions, maintaining 95% of the initial efficiency for 1920 h at an average relative humidity (RH) of 30%.
  • Fluorine-Boosted Kinetic and Selective Molecular Sieving of C6 Derivatives.

    Moosa, Basem; Alimi, Lukman Olawale; Lin, Weibin; Fakim, Aliyah; Bhatt, Prashant; Eddaoudi, Mohamed; Khashab, Niveen M. (Angewandte Chemie (International ed. in English), 2023-09-25) [Article]
    Porous molecular sorbents have excellent selectivity towards hydrocarbon separation with energy saving techniques. However, to realize commercialization, molecular sieving processes should be faster and more efficient compared to extended frameworks. In this work, we show that utilizing fluorine to improve the hydrophobic profile of leaning pillararenes affords a substantial kinetic selective adsorption of benzene over cyclohexane (20:1 for benzene). The crystal structure shows a porous macrocycle that acts as a perfect match for benzene in both the intrinsic and extrinsic cavities with strong interactions in the solid state. The fluorinated leaning pillararene surpasses all reported organic molecular sieves and is comparable to the extended metal organic frameworks that were previously employed for this separation such as UIO-66. Most importantly, this sieving system outperformed the well-known zeolitic imidazolate frameworks under low pressure, which opens the door to new generations of molecular sieves that can compete with extended frameworks for more sustainable hydrocarbon separation.

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