Recent Submissions

  • Ultrahigh-flux Nanoporous Graphene Membrane for Sustainable Seawater Desalination Using Low-grade Heat

    Lu, Dongwei; Zhou, Zongyao; Wang, Zhihong; Ho, Duc Tam; Sheng, Guan; Chen, Long; Zhao, Yumeng; Li, Xiang; Cao, Li; Schwingenschlögl, Udo; Ma, Jun; Lai, Zhiping (Advanced Materials, Wiley, 2022-01-06) [Article]
    Membrane distillation has attracted great attention in the development of sustainable desalination and zero-discharge processes because of its possibility to recover 100% water and the potential to integrate with low-grade heat such as solar energy. However, the conventional membrane structures and materials afford limited flux thus obstructing its practical application. Here we report ultrathin nanoporous graphene membranes by selectively forming thin graphene layers on the top edges of highly porous anodic alumina oxide support, which creates short and fast transport pathways for water vapor but not liquid. The process avoids the challenging pore-generation and substrate-transfer processes required to prepare regular graphene membranes. In the direct contact membrane distillation mode under a mild temperature pair of 65°C /25°C, the nanoporous graphene membranes show an average water flux of 421.7 Lm<sup>-2</sup> h<sup>-1</sup> with over 99.8% salt rejection, which is an order of magnitude higher than any reported polymeric membranes. The mechanism for high water flux is revealed by detailed characterizations and theoretical modeling. Outdoor field tests using Red Sea water heated under direct sunlight radiation show that the membranes have an average water flux of 86.3 Lm<sup>-2</sup> h<sup>-1</sup> from 8 am. to 8 pm., showing a great potential for real applications in seawater desalination. This article is protected by copyright. All rights reserved.
  • Investigations of crude-oil emulsions at the micro-to-nano scales

    Ravaux, Florent; Medina, Sandra Constanza; Behzad, Ali Reza; Zafar, Humaira; George, Abraham; Morin, Stephane; Ghaffour, NorEddine; Anjum, Dalaver H. (Fuel, Elsevier BV, 2021-12) [Article]
    The removal of the micro droplets of emulsified water from crude oil causes high cost and energy. In this paper we show that cryo electron microscopy (cryo-EM) imaging of micro and nano emulsions prepared from United Arab Emirate based crude oil provides critical information on their stability. Specifically, the cryoSEM imaging analysis applied to emulsion of murban-2019, and upper zakum-2019 crude-oils allowed determining naturally occurring surfactants in these crude-oils. Moreover, the applied method also turned out to be an efficient way to qualitatively investigate the effect of synthetic surfactant on the stability of the emulsions. The high resolution cryoTEM imaging analysis of emulsions from upper zakum-2019 sample enabled visualizing “bilayer” of naturally occurring surfactants, presumably the asphaltene. The cryoTEM analysis further allowed estimating the volume-fraction of emulsified water in the crude-oil at nanoscales and turned out to be about 1% for the upper zakum-2019 samples.
  • Mitochondrial “dysmorphology” in variant classification

    Shamseldin, Hanan E.; Alhashem, Amal; Tabarki, Brahim; Abdulwahab, Firdous; Hashem, Mais; Sougrat, Rachid; Alkuraya, Fowzan S. (Human Genetics, Springer Science and Business Media LLC, 2021-11-08) [Article]
    Mitochondrial disorders are challenging to diagnose. Exome sequencing has greatly enhanced the diagnostic precision of these disorders although interpreting variants of uncertain significance (VUS) remains a formidable obstacle. Whether specific mitochondrial morphological changes can aid in the classification of these variants is unknown. Here, we describe two families (four patients), each with a VUS in a gene known to affect the morphology of mitochondria through a specific role in the fission–fusion balance. In the first, the missense variant in MFF, encoding a fission factor, was associated with impaired fission giving rise to a characteristically over-tubular appearance of mitochondria. In the second, the missense variant in DNAJA3, which has no listed OMIM phenotype, was associated with fragmented appearance of mitochondria consistent with its published deficiency states. In both instances, the highly specific phenotypes allowed us to upgrade the classification of the variants. Our results suggest that, in select cases, mitochondrial “dysmorphology” can be helpful in interpreting variants to reach a molecular diagnosis.
  • Oligoethylene glycol sidechains increase charge generation in organic semiconductor nanoparticles for enhanced photocatalytic hydrogen evolution

    Kosco, Jan; Gonzalez-Carrero, Soranyel; Howells, Calvyn Travis; Zhang, Weimin; Moser, Maximilian; Sheelamanthula, Rajendar; Zhao, Lingyun; Willner, Benjamin; Hidalgo, Tania C.; Faber, Hendrik; Purushothaman, Balaji; Sachs, Michael; Cha, Hyojung; Sougrat, Rachid; Anthopolous, Thomas D.; Inal, Sahika; Durrant, James R.; McCulloch, Iain (Advanced Materials, Wiley, 2021-10-29) [Article]
    Organic semiconductor nanoparticles (NPs) composed of an electron donor/acceptor (D/A) semiconductor blend have recently emerged as an efficient class of hydrogen evolution photocatalysts. We demonstrate that employing conjugated polymers functionalized with (oligo)ethylene glycol sidechains in NP photocatalysts can greatly enhance their H2 evolution efficiency compared to their non-glycolated analogues. The strategy is broadly applicable to a range of structurally diverse conjugated polymers. Transient spectroscopic studies show that glycolation facilitates charge generation even in the absence of a D/A heterojunction, and further suppresses both geminate and non-geminate charge recombination in D/A NPs. This results in a high yield of photogenerated charges with lifetimes long enough to efficiently drive ascorbic acid oxidation, which is correlated with greatly enhanced H2 evolution rates in the glycolated NPs. Glycolation increases the relative permittivity of the semiconductors and facilitates water uptake. Together, these effects may increase the high frequency relative permittivity inside the NPs sufficiently to cause the observed suppression of exciton and charge recombination responsible for the high photocatalytic activities of the glycolated NPs.
  • Thermal treatment of hydroxyl functionalized polytriazole and its effect on gas transport: From crosslinking to carbon molecular sieve

    Chisca, Stefan; Bettahalli Narasimha, Murthy Srivatsa; Musteata, Valentina-Elena; Vasylevskyi, Serhii; Hedhili, Mohamed N.; Abou-Hamad, Edy; Karunakaran, Madhavan; Genduso, Giuseppe; Nunes, Suzana Pereira (Journal of Membrane Science, Elsevier BV, 2021-10-22) [Article]
    We propose hydroxyl-functionalized polytriazole as a precursor for the preparation of highly crosslinked membranes and carbon molecular sieves (CMS) for gas separation. We studied the effect of the treatment temperature on the chemical structure and gas separation properties. A progressing crosslinking structure was formed when polytriazole films were treated in the range of 300–400 °C. Above 425 °C, CMSs with multi-layered nitrogen-graphene-like structures were obtained. The CO2 permeability increased by increasing the temperature, while the CO2/CH4 selectivity was maintained. Permeability increases up to 37-fold compared to the untreated polymer film were obtained, aligned with a CO2/CH4 selectivity of 75. The single-gas CO2 permeability vs. CO2/CH4 selectivity data obtained for films treated at 475 and 550 °C are among the highest reported in the literature. Moreover, the mixed gas performance of these membranes is far above previously reported CO2/CH4 data plotted as mixed-gas trade-off curves, demonstrating the potential of polytriazole materials for these applications.
  • Selectivity descriptors for the direct hydrogenation of CO2 to hydrocarbons during zeolite-mediated bifunctional catalysis

    Galilea, Adrian; Gong, Xuan; Caglayan, Mustafa; Nastase, Stefan-Adrian F.; Abou-Hamad, Edy; Gevers, Lieven; Cavallo, Luigi; Chowdhury, Abhishek Dutta; Gascon, Jorge (Nature Communications, Springer Science and Business Media LLC, 2021-10-08) [Article]
    AbstractCascade processes are gaining momentum in heterogeneous catalysis. The combination of several catalytic solids within one reactor has shown great promise for the one-step valorization of C1-feedstocks. The combination of metal-based catalysts and zeolites in the gas phase hydrogenation of CO2 leads to a large degree of product selectivity control, defined mainly by zeolites. However, a great deal of mechanistic understanding remains unclear: metal-based catalysts usually lead to complex product compositions that may result in unexpected zeolite reactivity. Here we present an in-depth multivariate analysis of the chemistry involved in eight different zeolite topologies when combined with a highly active Fe-based catalyst in the hydrogenation of CO2 to olefins, aromatics, and paraffins. Solid-state NMR spectroscopy and computational analysis demonstrate that the hybrid nature of the active zeolite catalyst and its preferred CO2-derived reaction intermediates (CO/ester/ketone/hydrocarbons, i.e., inorganic-organic supramolecular reactive centers), along with 10 MR-zeolite topology, act as descriptors governing the ultimate product selectivity.
  • CDKL5 kinase controls transcription-coupled responses to DNA damage

    Khanam, Taran; Muñoz, Ivan; Weiland, Florian; Carroll, Thomas; Morgan, Michael; Borsos, Barbara N.; Pantazi, Vasiliki; Slean, Meghan; Novak, Miroslav; Toth, Rachel; Appleton, Paul; Pankotai, Tibor; Zhou, Houjiang; Rouse, John (The EMBO Journal, EMBO, 2021-10-04) [Article]
    Mutations in the gene encoding the CDKL5 kinase are among the most common genetic causes of childhood epilepsy and can also give rise to the severe neurodevelopmental condition CDD (CDKL5 deficiency disorder). Despite its importance for human health, the phosphorylation targets and cellular roles of CDKL5 are poorly understood, especially in the cell nucleus. Here, we report that CDKL5 is recruited to sites of DNA damage in actively transcribed regions of the nucleus. A quantitative phosphoproteomic screen for nuclear CDKL5 substrates reveals a network of transcriptional regulators including Elongin A (ELOA), phosphorylated on a specific CDKL5 consensus motif. Recruitment of CDKL5 and ELOA to damaged DNA, and subsequent phosphorylation of ELOA, requires both active transcription and the synthesis of poly(ADP-ribose) (PAR), to which CDKL5 can bind. Critically, CDKL5 kinase activity is essential for the transcriptional silencing of genes induced by DNA double-strand breaks. Thus, CDKL5 is a DNA damage-sensing, PAR-controlled transcriptional modulator, a finding with implications for understanding the molecular basis of CDKL5-related diseases.
  • Illuminating the Intrinsic Effect of Water Co-feeding on Methane Dehydroaromatization: A Comprehensive Study

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

    Driguez, Patrick; Bougouffa, Salim; Carty, Karen; Putra, Alexander; Jabbari, Kamel; Reddy, Muppala P.; Soppe, Richard Willem Otto; Cheung, Ming Sin; Fukasawa, Yoshinori; Ermini, Luca (Genome biology, Springer Science and Business Media LLC, 2021-09-03) [Article]
    Currently, different sequencing platforms are used to generate plant genomes and no workflow has been properly developed to optimize time, cost, and assembly quality. We present LeafGo, a complete de novo plant genome workflow, that starts from tissue and produces genomes with modest laboratory and bioinformatic resources in approximately 7 days and using one long-read sequencing technology. LeafGo is optimized with ten different plant species, three of which are used to generate high-quality chromosome-level assemblies without any scaffolding technologies. Finally, we report the diploid genomes of Eucalyptus rudis and E. camaldulensis and the allotetraploid genome of Arachis hypogaea.
  • Molecular Engineering of Covalent Organic Framework Cathodes for Enhanced Zinc-Ion Batteries

    Wang, Wenxi; Kale, Vinayak Swamirao; Cao, Zhen; Lei, Yougjiu; Kandambeth, Sharath; Zou, Guodong; Zhu, Yunpei; Abou-Hamad, Edy; Shekhah, Osama; Cavallo, Luigi; Eddaoudi, Mohamed; Alshareef, Husam N. (Advanced Materials, Wiley, 2021-08-08) [Article]
    Covalent organic frameworks (COFs) are potentially promising electrode materials for electrochemical charge storage applications thanks to their pre-designable reticular chemistry with atomic precision, allowing precise control of pore size, redox-active functional moieties, and stable covalent frameworks. However, studies on the mechanistic and practical aspects of their zinc-ion storage behavior are still limited. In this study, a strategy to enhance the electrochemical performance of COF cathodes in zinc-ion batteries (ZIBs) by introducing the quinone group into 1,4,5,8,9,12-hexaazatriphenylene-based COFs is reported. Electrochemical characterization demonstrates that the introduction of the quinone groups in the COF significantly pushes up the Zn2+ storage capability against H+ and elevates the average (dis-)charge potential in aqueous ZIBs. Computational and experimental analysis further reveals the favorable redox-active sites that host Zn2+/H+ in COF electrodes and the root cause for the enhanced electrochemical performance. This work demonstrates that molecular engineering of the COF structure is an effective approach to achieve practical charge storage performance.
  • Bioengineering Progress in Lung Assist Devices

    Syed, Ahad; Kerdi, Sarah; Qamar, Adnan (Bioengineering, MDPI AG, 2021-06-28) [Article]
    Artificial lung technology is advancing at a startling rate raising hopes that it would better serve the needs of those requiring respiratory support. Whether to assist the healing of an injured lung, support patients to lung transplantation, or to entirely replace native lung function, safe and effective artificial lungs are sought. After 200 years of bioengineering progress, artificial lungs are closer than ever before to meet this demand which has risen exponentially due to the COVID-19 crisis. In this review, the critical advances in the historical development of artificial lungs are detailed. The current state of affairs regarding extracorporeal membrane oxygenation, intravascular lung assists, pump-less extracorporeal lung assists, total artificial lungs, and microfluidic oxygenators are outlined.
  • Characterization of Silica-Supported Tungsten Bis- and Tris-hydrides by Advanced Solid-State NMR

    Wackerow, Wiebke; Thiam, Zeynabou; Abou-Hamad, Edy; Almaksoud, Walid; Hedhili, Mohamed N.; Basset, Jean-Marie (The Journal of Physical Chemistry C, American Chemical Society (ACS), 2021-06-03) [Article]
    Tungsten-hydrides supported on oxide supports are unique catalysts regarding the direct transformation of ethylene to propylene, alkane metathesis, and the low-temperature hydrogenolysis of waxes to lower molecular paraffins. The number of hydrides coordinated to the tungsten center and their structure on the siliceous support with very high surface silica (KCC-1) is unknown. KCC-1(700) silica of extremely high surface area allows for a high tungsten metal loading of 14 wt %. We show here the full characterization of supported tungsten bis- and tris-hydrides, which, after reaction with N2O gas, yield well-defined tungsten bis- and tris-hydroxide species on KCC-1(700). The obtained tungsten-hydroxide species are perfectly suitable for a detailed NMR study. The obtained tungsten hydroxo complexes are proven to be a tungsten bis-hydroxo and tungsten tris-hydroxo species. This analysis supports the conclusion that supported tungsten-hydride complexes coexist on the support as bis-hydride and tris-hydride species. They are, respectively, in close proximity to the silicon bis-hydride and the silicon mono-hydride. This proximity is explained by the mechanism of the formation of tungsten-hydride on the silica surface.
  • Emergence of Room Temperature Magnetotransport Anomaly in Epitaxial Pt/γ′-Fe4N/MgO Heterostructures toward Noncollinear Spintronics

    Shi, Xiaohui; Jiang, Jiawei; Wang, Yadong; Hou, Zhipeng; Zhang, Qiang; Mi, Wenbo; Zhang, Xixiang (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2021-05-27) [Article]
    Noncollinear spin textures have attracted much attention due to their novel physical behaviors in heavy/ferromagnetic metal (HM/FM) systems. The transport anomaly, appearing as contrast humps in Hall resistivity curves, is the mark of noncollinear spin textures. Here, the epitaxial Pt/γ'-Fe<sub>4</sub>N bilayers with noncollinear spin textures were obtained by facing target sputtering. Large micromagnetic Dzyaloshinskii-Moriya interaction coefficient <i>D</i> of 2.90 mJ/m<sup>2</sup> appears in Pt/γ'-Fe<sub>4</sub>N/MgO systems, which is larger than 2.05 mJ/m<sup>2</sup> of Pt/Co/MgO systems with skyrmionic states. Moreover, at 300 K, magnetic bubble-like domains appear in Pt/γ'-Fe<sub>4</sub>N bilayers that just possess a 3 nm thick ferromagnetic layer instead of [HM/FM]<i><sub>n</sub></i> or [HM<sub>1</sub>/FM/HM<sub>2</sub>]<i><sub>n</sub></i> multilayers. Additionally, a room-temperature transport anomaly appears in Pt/γ'-Fe<sub>4</sub>N/MgO systems. The contrast humps of Pt(3 nm)/γ'-Fe<sub>4</sub>N(<i>t</i><sub>Fe<sub>4</sub>N</sub> ≤ 4 nm)/MgO heterostructures are not sharp due to the nonuniform distributions of the magnetic bubble-like domains with various sizes and irregular shapes, as observed by the magnetic force microscopy. The discovery of epitaxial Pt/γ'-Fe<sub>4</sub>N bilayers with noncollinear spin states is more crucial than that of polycrystalline or amorphous HM/FM systems for reducing ohmic heating, which provides a candidate for noncollinear spintronic applications.
  • Microscopy techniques applied to submicron characterization of oilfield produced water

    Medina, Sandra Constanza; Anjum, Dalaver H.; Behzad, Ali Reza; Vilagines, Regis D.; Tabatabai, S. Assiyeh Alizadeh; Leiknes, TorOve (Journal of Petroleum Science and Engineering, Elsevier BV, 2021-05-26) [Article]
    Produced water (PW) and formation water are complex mixtures of hydrocarbons and water produced at oil and gas upstream facilities. Submicron oil droplets represent a multitude of issues affecting the performance of downstream advanced water treatment processes, such as micro and ultra-filtration processes. Conventional de-oiling technologies do not efficiently remove submicron oil droplets in PW. An accurate characterization of submicron oil droplets and contaminants is required to improve PW treatment technology. In this study, a methodology for visualization and quantification of submicron oil droplets size distribution (DSD), using optical and electron microscopy techniques, was developed. Various microscopy techniques were evaluated, including epifluorescence microscopy (EpiFM), confocal laser scanning microscopy (CLSM), cryogenic scanning and transmission electron microscopy (cryo-SEM and cryo-TEM, respectively). Synthetic PW was used to improve and standardize the sample preparation and characterization methodology. The improved methodology was then tested with two PW samples from different oilfields in the Middle East region. Two methods were developed for the determination of DSD in oilfield PW samples. The first method is suitable for highly polydisperse PW samples with oil droplets larger than 250 nm. This method is based on using low-temperature agarose to immobilize the samples, avoiding coalescence, and allowing clear visualization of the oil droplets at high magnification in EpiFM. The second method is suitable for concentrated PW samples and oil droplets as small as 20 nm in size. This method is based on cryo-TEM with plunge freezing and without the use of agarose for sample immobilization. The agarose-immobilization technique was also applied for sample preparation in cryo-SEM. Cryo-SEM fixation by high-pressure freezing (HPF) preserved the morphology of oil droplets in synthetic oil-concentrated samples and allowed its visualization in a wide range of sizes from 50 nm up to 20 μm.
  • Highly Active Heterogeneous Catalyst for Ethylene Dimerization Prepared by Selectively Doping Ni on the Surface of a Zeolitic Imidazolate Framework

    Chen, Cailing; Alalouni, Mohammed R.; Dong, Xinglong; Cao, Zhen; Cheng, Qingpeng; Zheng, Lirong; Meng, Lingkun; Guan, Chao; Liu, L. M.; Abou-Hamad, Edy; Wang, Jianjian; Shi, Zhan; Huang, Kuo-Wei; Cavallo, Luigi; Han, Yu (Journal of the American Chemical Society, American Chemical Society (ACS), 2021-04-28) [Article]
    The production of 1-butene by ethylene dimerization is an important chemical industrial process currently implemented using homogeneous catalysts. Here, we describe a highly active heterogeneous catalyst (Ni-ZIF-8) for ethylene dimerization, which consists of isolating Ni-active sites selectively located on the crystal surface of a zeolitic imidazolate framework. Ni-ZIF-8 can be easily prepared by a simple one-pot synthesis method in which site-specific anchoring of Ni is achieved spontaneously because of the incompatibility between the d<sup>8</sup> electronic configuration of Ni<sup>2+</sup> and the three-dimensional framework of ZIF-8. The full exposure and square-planar coordination of the Ni sites accounts for the high catalytic activity of Ni-ZIF-8. It exhibits an average ethylene turnover frequency greater than 1 000 000 h<sup>-1</sup> (1-butene selectivity >85%) at 35 °C and 50 bar, far exceeding the activities of previously reported heterogeneous catalysts and many homogeneous catalysts under similar conditions. Moreover, compared to molecular Ni complexes used as homogeneous catalysts for ethylene dimerization, Ni-ZIF-8 has significantly higher stability and shows constant activity during 4 h of continuous reaction. Isotopic labeling experiments indicate that ethylene dimerization over Ni-ZIF-8 follows the Cossee-Arlman mechanism, and detailed characterizations combined with density functional theory calculations rationalize this observed high activity.
  • Giant clam inspired high-speed photo-conversion for ultraviolet optical wireless communication

    Subedi, Ram Chandra; Rossbach, Susann; Kang, Chun Hong; Alkhazragi, Omar; Sun, Xiaobin; Holguin Lerma, Jorge Alberto; Mitra, Somak; Roqan, Iman S.; Behzad, Ali Reza; Sougrat, Rachid; Ng, Tien Khee; Bradley, Donal; Duarte, Carlos M.; Ooi, Boon S. (Optical Materials Express, The Optical Society, 2021-04-22) [Article]
    Organisms have evolved the ability to manipulate light for vision, as a means to capture its energy, to protect themselves from damage, especially against ultraviolet (UV) and other high flux radiation, and for display purposes. The makeup of the structural elements used for this manipulation often discloses novel pathways for man-made photonic devices. Iridocytes in the mantle of giant clams in the Tridacninae subfamily manipulate light in many ways, e.g., as reflectors, scattering centers, and diffusers. There is, however, a void in understanding the absorption and photoluminescence (PL) emission dynamics of these cells. In turn, a profound understanding of iridocytes’ photophysics can offer the prospect for a new generation of advanced optoelectronic materials and devices. Here, the structural and optical properties of the iridocytes embedded in the mantle tissue of the Tridacna maxima are investigated and their use as a high-speed color convertor for UV photodetection, well-suited to application in UV optical wireless communication, is demonstrated.
  • Citrullination of Proteins as a Specific Response Mechanism in Plants.

    Marondedze, Claudius; Elia, Giuliano; Thomas, Ludivine; Wong, Aloysius; Gehring, Christoph A (Frontiers in plant science, Frontiers Media SA, 2021-04-08) [Article]
    Arginine deimination, also referred to as citrullination of proteins by L-arginine deiminases, is a post-translational modification affecting histone modifications, epigenetic transcriptional regulation, and proteolysis in animals but has not been reported in higher plants. Here we report, firstly, that Arabidopsis thaliana proteome contains proteins with a specific citrullination signature and that many of the citrullinated proteins have nucleotide-binding regulatory functions. Secondly, we show that changes in the citrullinome occur in response to cold stress, and thirdly, we identify an A. thaliana protein with peptidyl arginine deiminase activity that was shown to be calcium-dependent for many peptide substrates. Taken together, these findings establish this post-translational modification as a hitherto neglected component of cellular reprogramming during stress responses.
  • Synthesis and Characterization of Iron-Doped TiO2 Nanoparticles Using Ferrocene from Flame Spray Pyrolysis

    Ismail, Mohamed; Hedhili, Mohamed N.; Anjum, Dalaver H.; Singaravelu, Venkatesh; Chung, Suk Ho (Catalysts, MDPI AG, 2021-03-29) [Article]
    Iron-doped titanium dioxide nanoparticles, with Fe/Ti atomic ratios from 0% to 10%, were synthesized by flame spray pyrolysis (FSP), employing a single-step method. Ferrocene, being nontoxic and readily soluble in liquid hydrocarbons, was used as the iron source, while titanium tetraisopropoxide (TTIP) was used as the precursor for TiO2. The general particle characterization and phase description were examined using ICP-OES, XRD, BET, and Raman spectroscopy, whereas the XPS technique was used to study the surface chemistry of the synthesized particles. For particle morphology, HRTEM with EELS and EDS analyses were used. Optical and magnetic properties were examined using UV–vis and SQUID, respectively. Iron doping to TiO2 nanoparticles promoted rutile phase formation, which was minor in the pure TiO2 particles. Iron-doped nanoparticles exhibited a uniform iron distribution within the particles. XPS and UV–vis results revealed that Fe2+ was dominant for lower iron content and Fe3+ was common for higher iron content and the iron-containing particles had a contracted band gap of ~1 eV lower than pure TiO2 particles with higher visible light absorption. SQUID results showed that doping TiO2 with Fe changed the material to be paramagnetic. The generated nanoparticles showed a catalytic effect for dye-degradation under visible light.
  • Engineering Band-Type Alignment in CsPbBr 3 Perovskite-Based Artificial Multiple Quantum Wells

    Lee, Kwangjae; Merdad, Noor A.; Maity, Partha; El Demellawi, Jehad K.; Lui, Zhixiong; Sinatra, Lutfan; Zhumekenov, Ayan A.; Hedhili, Mohamed N.; Min, Jung-Wook; Min, Jung-Hong; Gutierrez Arzaluz, Luis; Anjum, Dalaver H.; Wei, Nini; Ooi, Boon S.; Alshareef, Husam N.; Mohammed, Omar F.; Bakr, Osman (Advanced Materials, Wiley, 2021-03-24) [Article]
    Semiconductor heterostructures of multiple quantum wells (MQWs) have major applications in optoelectronics. However, for halide perovskites—the leading class of emerging semiconductors—building a variety of bandgap alignments (i.e., band-types) in MQWs is not yet realized owing to the limitations of the current set of used barrier materials. Here, artificial perovskite-based MQWs using 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole), tris-(8-hydroxyquinoline)aluminum, and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline as quantum barrier materials are introduced. The structures of three different five-stacked perovskite-based MQWs each exhibiting a different band offset with CsPbBr3 in the conduction and valence bands, resulting in a variety of MQW band alignments, i.e., type-I or type-II structures, are shown. Transient absorption spectroscopy reveals the disparity in charge carrier dynamics between type-I and type-II MQWs. Photodiodes of each type of perovskite artificial MQWs show entirely different carrier behaviors and photoresponse characteristics. Compared with bulk perovskite devices, type-II MQW photodiodes demonstrate a more than tenfold increase in the rectification ratio. The findings open new opportunities for producing halide-perovskite-based quantum devices by bandgap engineering using simple quantum barrier considerations.
  • Highly efficient transverse-electric-dominant ultraviolet-C emitters employing GaN multiple quantum disks in AlN nanowire matrix

    Subedi, Ram Chandra; Min, Jung Wook; Mitra, Somak; Li, Kuang Hui; Ajia, Idris A.; Stegenburgs, Edgars; Anjum, Dalaver H.; Conroy, Michele; Moore, Kalani; Bangert, Ursel; Roqan, Iman S.; Ng, Tien Khee; Ooi, Boon S. (SPIE, 2021-03-05) [Conference Paper]
    Heavy reliance on extensively studied AlGaN based light emitting diodes (LEDs) to replace environmentally hazardous mercury based ultraviolet (UV) lamps is inevitable. However, external quantum efficiency (EQE) for AlGaN based deep UV emitters remains poor. Dislocation induced nonradiative recombination centers and poor electron-hole wavefunction overlap due to the large polarization field induced quantum confined stark effect (QCSE) in "Al"rich AlGaN are some of the key factors responsible for poor EQE. In addition, the transverse electric polarized light is extremely suppressed in "Al"-rich AlGaN quantum wells (QWs) because of the undesired crossing over among the light hole (LH), heavy hole (HH) and crystal-field split-off (SH) states. Here, optical and structural integrities of dislocation-free ultrathin GaN quantum disk (QDisk) (∼ 1.2 nm) embedded in AlN barrier (∼ 3 nm) grown employing plasma-assisted molecular beam epitaxy (PAMBE) are investigated considering it as a novel nanostructure to realize highly efficient TE polarized deep UV emitters. The structural and chemical integrities of thus grown QDisks are investigated by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). We, particularly, emphasize the polarization dependent photoluminescence (PL) study of the GaN Disks to accomplish almost purely TE polarized UV (∼ 260 nm) light. In addition, we observed significantly high internal quantum efficiency (IQE) of ∼ 80 %, which is attributed to the enhanced overlap of the electron-hole wavefunction in extremely quantum confined ultrathin GaN QDisks, thereby presenting GaN QDisks embedded in AlN nanowires as a practical pathway towards the efficient deep UV emitters.

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