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285 results on '"Oveisi, Emad"'

4. 3D Reconstruction of Curvilinear Structures with Stereo Matching DeepConvolutional Neural Networks

Author

Altingövde, Okan, Mishchuk, Anastasiia, Ganeeva, Gulnaz, Oveisi, Emad, Hebert, Cecile, and Fua, Pascal

Subjects
Electrical Engineering and Systems Science - Image and Video Processing, Computer Science - Computer Vision and Pattern Recognition
Abstract

Curvilinear structures frequently appear in microscopy imaging as the object of interest. Crystallographic defects, i.e., dislocations, are one of the curvilinear structures that have been repeatedly investigated under transmission electron microscopy (TEM) and their 3D structural information is of great importance for understanding the properties of materials. 3D information of dislocations is often obtained by tomography which is a cumbersome process since it is required to acquire many images with different tilt angles and similar imaging conditions. Although, alternative stereoscopy methods lower the number of required images to two, they still require human intervention and shape priors for accurate 3D estimation. We propose a fully automated pipeline for both detection and matching of curvilinear structures in stereo pairs by utilizing deep convolutional neural networks (CNNs) without making any prior assumption on 3D shapes. In this work, we mainly focus on 3D reconstruction of dislocations from stereo pairs of TEM images.

Published
2021

5. Atomic scale symmetry and polar nanoclusters in the paraelectric phase of ferroelectric materials

Author

Bencan, Andreja, Oveisi, Emad, Hashemizadeh, Sina, Veerapandiyan, Vignaswaran K., Hoshina, Takuya, Rojac, Tadej, Deluca, Marco, Drazic, Goran, and Damjanovic, Dragan

Subjects
Condensed Matter - Materials Science
Abstract

The nature of the "forbidden" local- and long-range polar order in nominally nonpolar paraelectric phases of ferroelectric materials has been an open question since the discovery of ferroelectricity in oxide perovskites (ABO3). A currently considered model suggests locally correlated displacements of B-site atoms along a subset of <111> cubic directions. Such offsite displacements have been confirmed experimentally, however, being essentially dynamic in nature they cannot account for the static nature of the symmetry-forbidden polarization implied by the macroscopic experiments. Here, in an atomically resolved study by aberration corrected scanning transmission electron microscopy (STEM) complemented by Raman spectroscopy, we reveal, directly visualize and quantitatively describe static, 2-4 nm large polar nanoclusters in the nominally nonpolar cubic phases of (Ba,Sr)TiO3 and BaTiO3. These results have implications on understanding of the atomic-scale structure of disordered materials, the origin of precursor states in ferroelectrics, and may help answering ambiguities on the dynamic-versus-static nature of nano-sized clusters., Comment: the main text and supplementary information

Published
2020
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7. Rapid, Selective Heavy Metal Removal from Water by a Metal–Organic Framework/Polydopamine Composite

Author

Sun, Daniel T, Peng, Li, Reeder, Washington S, Moosavi, Seyed Mohamad, Tiana, Davide, Britt, David K, Oveisi, Emad, and Queen, Wendy L

Subjects
Chemical Sciences, Chemical sciences
Abstract

Drinking water contamination with heavy metals, particularly lead, is a persistent problem worldwide with grave public health consequences. Existing purification methods often cannot address this problem quickly and economically. Here we report a cheap, water stable metal-organic framework/polymer composite, Fe-BTC/PDA, that exhibits rapid, selective removal of large quantities of heavy metals, such as Pb2+ and Hg2+, from real world water samples. In this work, Fe-BTC is treated with dopamine, which undergoes a spontaneous polymerization to polydopamine (PDA) within its pores via the Fe3+ open metal sites. The PDA, pinned on the internal MOF surface, gains extrinsic porosity, resulting in a composite that binds up to 1634 mg of Hg2+ and 394 mg of Pb2+ per gram of composite and removes more than 99.8% of these ions from a 1 ppm solution, yielding drinkable levels in seconds. Further, the composite properties are well-maintained in river and seawater samples spiked with only trace amounts of lead, illustrating unprecedented selectivity. Remarkably, no significant uptake of competing metal ions is observed even when interferents, such as Na+, are present at concentrations up to 14 000 times that of Pb2+. The material is further shown to be resistant to fouling when tested in high concentrations of common organic interferents, like humic acid, and is fully regenerable over many cycles.

Published
2018

13. Proton-transfer-induced 3D/2D hybrid perovskites suppress ion migration and reduce luminance overshoot

Author

Kim, Hobeom, Kim, Joo Sung, Heo, Jung-Min, Pei, Mingyuan, Park, In-Hyeok, Liu, Zhun, Yun, Hyung Joong, Park, Min-Ho, Jeong, Su-Hun, Kim, Young-Hoon, Park, Jin-Woo, Oveisi, Emad, Nagane, Satyawan, Sadhanala, Aditya, Zhang, Lijun, Kweon, Jin Jung, Lee, Sung Keun, Yang, Hoichang, Jang, Hyun Myung, Friend, Richard H., Loh, Kian Ping, Nazeeruddin, Mohammad Khaja, Park, Nam-Gyu, and Lee, Tae-Woo

Published
2020
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16. Metal-organic framework-based oxygen carriers with antioxidant activity resulting from the incorporation of gold nanozymes

Author

Liu, Xiaoli, Domingues, Nency Patricio, Oveisi, Emad, Coll-Satue, Clara, Jansman, Michelle Maria Theresia, Smit, Berend, Hosta-Rigau, Leticia, Liu, Xiaoli, Domingues, Nency Patricio, Oveisi, Emad, Coll-Satue, Clara, Jansman, Michelle Maria Theresia, Smit, Berend, and Hosta-Rigau, Leticia

Abstract

Blood transfusions are a life-saving procedure since they can preserve the body's oxygen levels in patients suffering from acute trauma, undergoing surgery, receiving chemotherapy or affected by severe blood disorders. Due to the central role of hemoglobin (Hb) in oxygen transport, so-called Hb-based oxygen carriers (HBOCs) are currently being developed for situations where donor blood is not available. In this context, an important challenge that needs to be addressed is the oxidation of Hb into methemoglobin (metHb), which is unable to bind and release oxygen. While several research groups have considered the incorporation of antioxidant enzymes to create HBOCs with minimal metHb conversion, the use of biological enzymes has important limitations related to their high cost, potential immunogenicity or low stability in vivo. Thus, nanomaterials with enzyme-like properties (i.e., nanozymes (NZs)) have emerged as a promising alternative. Amongst the different NZs, gold (Au)-based metallic nanoparticles are widely used for biomedical applications due to their biocompatibility and multi-enzyme mimicking abilities. Thus, in this work, we incorporate Au-based NZs into a type of HBOC previously reported by our group (i.e., Hb-loaded metal-organic framework (MOF)-based nanocarriers (NCs)) and investigate their antioxidant properties. Specifically, we prepare MOF-NCs loaded with Au-based NZs and demonstrate their ability to catalytically deplete over multiple rounds of two prominent reactive oxygen species (ROS) that exacerbate Hb's autoxidation (i.e., hydrogen peroxide and the superoxide radical). Importantly, following loading with Hb, we show how these ROS-scavenging properties translate into a decrease in metHb content. All in all, these results highlight the potential of NZs to create novel HBOCs with antioxidant protection which may find applications as a blood substitute in the future.

Published
2023

19. 3D vs. turbostratic: controlling metal-organic framework dimensionality via N-heterocyclic carbene chemistry

Author

Kochetygov, Ilia, Justin, Anita, Asgari, Mehrdad, Yang, Shuliang, Karve, Vikram, Schertenleib, Till, Stoian, Dragos, Oveisi, Emad, Mensi, Mounir, Queen, Wendy L, Kochetygov, Ilia [0000-0001-8013-5885], Justin, Anita [0000-0003-4496-1594], Asgari, Mehrdad [0000-0002-5427-1610], Schertenleib, Till [0000-0003-4989-5821], Oveisi, Emad [0000-0001-7483-7880], Queen, Wendy L [0000-0002-8375-2341], and Apollo - University of Cambridge Repository

Subjects
3402 Inorganic Chemistry, 34 Chemical Sciences, graphite, green, co2 adsorption, iridium(iii) complexes, activation, hydrogenation, electronic-properties, mofs, efficient
Abstract

Using azolium-based ligands for the construction of metal-organic frameworks (MOFs) is a viable strategy to immobilize catalytically active N-heterocyclic carbenes (NHC) or NHC-derived species inside MOF pores. Thus, in the present work, a novel copper MOF referred to as Cu-Sp5-BF4, is constructed using an imidazolinium ligand, H(2)Sp5-BF4, 1,3-bis(4-carboxyphenyl)-4,5-dihydro-1H-imidazole-3-ium tetrafluoroborate. The resulting framework, which offers large pore apertures, enables the post-synthetic modification of the C-2 carbon on the ligand backbone with methoxide units. A combination of X-ray diffraction (XRD), solid-state nuclear magnetic resonance (ssNMR) and electron microscopy (EM), are used to show that the post-synthetic methoxide modification alters the dimensionality of the material, forming a turbostratic phase, an event that further improves the accessibility of the NHC sites promoting a second modification step that is carried out via grafting iridium to the NHC. A combination of X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) methods are used to shed light on the iridium speciation, and the catalytic activity of the Ir-NHC containing MOF is demonstrated using a model reaction, stilbene hydrogenation.

Published
2022

23. Metallosupramolecular polymers as precursors for platinum nanocomposites

Author

Cappelletti, Claudio, Olaechea, Luis Miguel, Ianiro, Alessandro, Prado-Martínez, Cristina, Oveisi, Emad, Weder, Christoph, Schrettl, Stephen, and Schrettl Stephen

Subjects
nanoparticle composites, ni, Polymers and Plastics, generation, Organic Chemistry, reduction, Bioengineering, films, Biochemistry
Abstract

Nanocomposites comprised of a polymer matrix and metallic nanoparticles (NPs) can merge the structural features of the matrix material with the functional characteristics of the NPs. While such materials are promising for a wide range of applications, their preparation typical requires multi-step processes that can be difficult to control. Alternatively, materials with NPs can be directly accessed in a controlled manner by exploiting zero-valent metallosupramolecular polymer (MSP) precursors. We here report how the nature of the polymer and its molecular weight affect the nano­composite formation and structure. Poly(tetrahydrofuran)-based macromonomers with suitable ligands are used to prepare MSPs based on bis(h2-alkyne)­platinum(0) complexes. Heating these materials causes disassembly of the complexes and, upon the release of Pt0-atoms, Pt-NPs form in the matrix polymer. The Pt content in the MSP influences the NP formation and thereby the characteristics of the nanocomposites. It is also possible to trigger the complex dissociation and NP formation by exposure to UV light. This allows photolithographic processing and thus the preparation of nanocomposites that contain Pt-NPs in a spatially controlled manner.

Published
2022
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27. 3D Reconstruction of Curvilinear Structures with Stereo Matching DeepConvolutional Neural Networks

Author

Alting��vde, Okan, Mishchuk, Anastasiia, Ganeeva, Gulnaz, Oveisi, Emad, Hebert, Cecile, and Fua, Pascal

Subjects
FOS: Computer and information sciences, Computer Vision and Pattern Recognition (cs.CV), Image and Video Processing (eess.IV), FOS: Electrical engineering, electronic engineering, information engineering, Computer Science - Computer Vision and Pattern Recognition, Electrical Engineering and Systems Science - Image and Video Processing
Abstract

Curvilinear structures frequently appear in microscopy imaging as the object of interest. Crystallographic defects, i.e., dislocations, are one of the curvilinear structures that have been repeatedly investigated under transmission electron microscopy (TEM) and their 3D structural information is of great importance for understanding the properties of materials. 3D information of dislocations is often obtained by tomography which is a cumbersome process since it is required to acquire many images with different tilt angles and similar imaging conditions. Although, alternative stereoscopy methods lower the number of required images to two, they still require human intervention and shape priors for accurate 3D estimation. We propose a fully automated pipeline for both detection and matching of curvilinear structures in stereo pairs by utilizing deep convolutional neural networks (CNNs) without making any prior assumption on 3D shapes. In this work, we mainly focus on 3D reconstruction of dislocations from stereo pairs of TEM images.

Published
2021

29. A new post-synthetic polymerization strategy makes metal–organic frameworks more stable† †Electronic supplementary information (ESI) available: Detailed information for the synthesis and characterizations of all the materials. See DOI: 10.1039/c9sc00135b

Author

Yang, Shuliang, Peng, Li, Sun, Daniel T., Asgari, Mehrdad, Oveisi, Emad, Trukhina, Olga, Bulut, Safak, Jamali, Abbas, and Queen, Wendy L.

Subjects
Chemistry
Abstract

This work develops a new post-synthetic polymerization strategy to make various metal–organic frameworks more stable., Metal–organic frameworks are of interest in a number of host–guest applications. However, their weak coordination bonding often leads to instability in aqueous environments, particularly at extreme pH, and hence, is a challenging topic in the field. In this work, a two-step, post-synthetic polymerization method is used to create a series of highly hydrophobic, stable MOF composites. The MOFs are first coated with thin layers of polydopamine from free-base dopamine under a mild oxygen atmosphere, which then undergoes a Michael addition to covalently graft hydrophobic molecules to the external MOF surface. This easy, mild post-synthetic modification is shown to significantly improve the stability of a number of structurally diverse MOFs including HKUST-1 (Cu), ZIF-67 (Co), ZIF-8 (Zn), UiO-66 (Zr), Cu-TDPAT (Cu), Mg-MOF-74 (Mg) and MIL-100 (Fe) in wet, caustic (acidic and basic) environments as determined by powder X-ray diffraction and surface area measurements.

Published
2019

32. Single-layer graphene membranes by crack-free transfer for gas mixture separation

Author

Massachusetts Institute of Technology. Department of Chemical Engineering, Huang, Shiqi, Dakhchoune, Mostapha, Luo, Wen, Oveisi, Emad, He, Guangwei, Rezaei, Mojtaba, Zhao, Jing, Alexander, Duncan TL, Züttel, Andreas, Strano, Michael S, Agrawal, Kumar Varoon, Massachusetts Institute of Technology. Department of Chemical Engineering, Huang, Shiqi, Dakhchoune, Mostapha, Luo, Wen, Oveisi, Emad, He, Guangwei, Rezaei, Mojtaba, Zhao, Jing, Alexander, Duncan TL, Züttel, Andreas, Strano, Michael S, and Agrawal, Kumar Varoon

Abstract

© 2018 The Author(s). The single-layer graphene film, when incorporated with molecular-sized pores, is predicted to be the ultimate membrane. However, the major bottlenecks have been the crack-free transfer of large-area graphene on a porous support, and the incorporation of molecular-sized nanopores. Herein, we report a nanoporous-carbon-assisted transfer technique, yielding a relatively large area (1 mm2), crack-free, suspended graphene film. Gas-sieving (H2/CH4 selectivity up to 25) is observed from the intrinsic defects generated during the chemical-vapor deposition of graphene. Despite the ultralow porosity of 0.025%, an attractive H2 permeance (up to 4.1 × 10-7 mol m-2 s-1 Pa-1) is observed. Finally, we report ozone functionalization-based etching and pore-modification chemistry to etch hydrogen-selective pores, and to shrink the pore-size, improving H2 permeance (up to 300%) and H2/CH4 selectivity (up to 150%). Overall, the scalable transfer, etching, and functionalization methods developed herein are expected to bring nanoporous graphene membranes a step closer to reality.

Published
2021

34. Large-scale synthesis of crystalline g-C3N4 nanosheets and high-temperature H2 sieving from assembled films

Author

Villalobos, L, Vahdat, M, Dakhchoune, M, Nadizadeh, Z, Mensi, M, Oveisi, E, Campi, D, Marzari, N, Agrawal, K, Villalobos, Luis Francisco, Vahdat, Mohammad Tohidi, Dakhchoune, Mostapha, Nadizadeh, Zahra, Mensi, Mounir, Oveisi, Emad, Campi, Davide, Marzari, Nicola, Agrawal, Kumar Varoon, Villalobos, L, Vahdat, M, Dakhchoune, M, Nadizadeh, Z, Mensi, M, Oveisi, E, Campi, D, Marzari, N, Agrawal, K, Villalobos, Luis Francisco, Vahdat, Mohammad Tohidi, Dakhchoune, Mostapha, Nadizadeh, Zahra, Mensi, Mounir, Oveisi, Emad, Campi, Davide, Marzari, Nicola, and Agrawal, Kumar Varoon

Abstract

oly(triazine imide) (PTI), a crystalline g-C3N4, hosting two-dimensional nanoporous structure with an electron density gap of 0.34 nm, is highly promising for high-temperature hydrogen sieving because of its high chemical and thermal robustness. Currently, layered PTI is synthesized in potentially unsafe vacuum ampules in milligram quantities. Here, we demonstrate a scalable and safe ambient pressure synthesis route leading to several grams of layered PTI platelets in a single batch with 70% yield with respect to the precursor. Solvent exfoliation under anhydrous conditions led to single-layer PTI nanosheets evidenced by the observation of triangular g-C3N4 nanopores. Gas permeation studies confirm that PTI nanopores can sieve He and H2 from larger molecules. Last, high-temperature H2 sieving from PTI nanosheet-based membranes, prepared by the scalable filter coating technique, is demonstrated with H2 permeance reaching 1500 gas permeation units, with H2/CO2, H2/N2, and H2/CH4 selectivities reaching 10, 50, and 60, respectively, at 250°C.

Published
2020

46. Synthesis of Cu/CeO2-x Nanocrystalline Heterodimers with Interfacial Active Sites To Promote CO2 Electroreduction

Author

Varandili, Seyedeh Behnaz, Huang, Jianfeng, Oveisi, Emad, Gregorio, Gian Luca De, Mensi, Mounir, Strach, Michal, Vavra, Jan, Gadiyar, Chethana, Bhowmik, Arghya, Buonsanti, Raffaella, Varandili, Seyedeh Behnaz, Huang, Jianfeng, Oveisi, Emad, Gregorio, Gian Luca De, Mensi, Mounir, Strach, Michal, Vavra, Jan, Gadiyar, Chethana, Bhowmik, Arghya, and Buonsanti, Raffaella

Abstract

Synergistic effects at metal/metal oxide interfaces often give rise to highly active and selective catalytic motifs. So far, such interactions have been rarely explored to enhance the selectivity in the electrochemical CO2 reduction reaction (CO2RR). Herein, Cu/CeO2-x heterodimers (HDs) are synthesized and presented as one of the prime examples where such effects promote CO2RR. A colloidal seeded-growth synthesis is developed to connect the two highly mismatched domains (Cu and CeO2-x) through an interface. The Cu/CeO2-x HDs exhibit state-of-the-art selectivity toward CO2RR (up to ∼80%) against the competitive hydrogen evolution reaction (HER) and high faradaic efficiency for methane (up to ∼54%) at −1.2 VRHE, which is ∼5 times higher than that obtained when the Cu and CeO2-x nanocrystals are physically mixed. Operando X-ray absorption spectroscopy along with other ex-situ spectroscopies evidences the partial reduction of Ce4+ to Ce3+ in the HDs during CO2RR. A Density Functional Theory (DFT) study of the active site motif in reducing condition reveals synergistic effects in the electronic structure at the interface. The proposed lowest free energy pathway utilizes an O-vacancy site with intermediates binding to both Cu and Ce atoms, a configuration which allows one to break the CHO*/CO* scaling relation. The suppression of HER is attributed to the spontaneous formation of CO* at this interfacial motif and subsequent blockage of the Cu-sites.

Published
2019

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