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Ravuri S, Wrobel PS, Gorantla S, Bazioti C, Sunding MF, Lis K, Jedrzejewski R, Sartori S, Diplas S, Gunnæs AE, Bachmatiuk A. High yield and wide lateral size growth of α-Mo 2C: exploring the boundaries of CVD growth of bare MXene analogues. Nanotechnology 2024; 35:155601. [PMID: 38194713 DOI: 10.1088/1361-6528/ad1c97] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 01/09/2024] [Indexed: 01/11/2024]
Abstract
Synthesis of Mo2C bare MXenes, without surface terminations groups, via chemical vapor deposition (CVD) on metal foils is scientifically a very intriguing crystal growth process, and there are still challenges and limited fundamental understanding to overcome to obtain high yield and wide crystal size lateral growth. Achieving large area coverage via direct growth is scientifically vital to utilize the full potential of their unique properties in different applications. In this study, we sought to expand the boundaries of the current CVD growth approach for Mo2C MXenes and gain insights into the possibilities and limitations of large area growth, with a particular focus on controlling Mo concentration. We report a facile modification of their typical CVD growth protocol and show its influence on the Mo2C synthesis, with growth times spanning up to 3 h. Specifically, prior to initiating the CVD growth process, we introduced a holding step in temperature at 1095 °C. This proved to be beneficial in increasing the Mo concentration on the liquid Cu growth surface. We achieved an average Mo2C crystals coverage of approximately 50% of the growth substrate area, increased tendency of coalescence and merging of individual flakes, and lateral flake sizes up to 170μm wide. To gain deeper understanding into their CVD growth behavior, we conducted a systematic investigation of the effect of several factors, including (i) a holding step time on Mo diffusion rate through molten Cu, (ii) the Cu foil thickness over the Mo foil, and (iii) the CVD growth time. Phase, chemical and microstructural characterization by x-ray diffraction, x-ray photon spectroscopy, SEM and scanning/transmission electron microscopy revealed that the grown crystals are single phaseα-Mo2C. Furthermore, insights gained from this study sheds light on crucial factors and inherent limitations that are essential to consider and may help guide future research progress in CVD growth of bare MXenes.
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Affiliation(s)
- SyamSai Ravuri
- Łukasiewicz Research Network-PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
| | - Pawel S Wrobel
- Łukasiewicz Research Network-PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
- Centre of Polymer and Carbon Materials Polish Academy of Sciences, Marie Curie-Skłodowskiej 34, 41-819 Zabrze, Poland
| | - Sandeep Gorantla
- Łukasiewicz Research Network-PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
| | - Calliope Bazioti
- Department of Physics, Centre for Materials Science and Nanotechnology, University of Oslo, NO-0371 Oslo, Norway
| | - Martin F Sunding
- Materials Physics-Oslo, SINTEF Industry, PO Box 124, Blindern, Oslo NO-0314, Norway
| | - Krzysztof Lis
- Łukasiewicz Research Network-PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
| | - Roman Jedrzejewski
- Łukasiewicz Research Network-PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
| | - Sabrina Sartori
- Department of Technology Systems, University of Oslo, NO-2027 Kjeller, Norway
| | - Spyros Diplas
- Materials Physics-Oslo, SINTEF Industry, PO Box 124, Blindern, Oslo NO-0314, Norway
| | - Anette E Gunnæs
- Department of Physics, Centre for Materials Science and Nanotechnology, University of Oslo, NO-0371 Oslo, Norway
| | - Alicja Bachmatiuk
- Łukasiewicz Research Network-PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
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2
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Karasiński P, Zięba M, Gondek E, Nizioł J, Gorantla S, Rola K, Bachmatiuk A, Tyszkiewicz C. Sol-Gel Derived Silica-Titania Waveguide Films for Applications in Evanescent Wave Sensors-Comprehensive Study. Materials (Basel) 2022; 15:7641. [PMID: 36363233 PMCID: PMC9654017 DOI: 10.3390/ma15217641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 10/21/2022] [Accepted: 10/27/2022] [Indexed: 06/16/2023]
Abstract
Composite silica-titania waveguide films of refractive index ca. 1.8 are fabricated on glass substrates using a sol-gel method and dip-coating technique. Tetraethyl orthosilicate and tetraethyl orthotitanate with molar ratio 1:1 are precursors. Fabricated waveguides are annealed at 500 °C for 60 min. Their optical properties are studied using ellipsometry and UV-Vis spectrophotometry. Optical losses are determined using the streak method. The material structure and chemical composition, of the silica-titania films are analyzed using transmission electron microscopy (TEM) and electron dispersive spectroscopy (EDS), respectively. The surface morphology was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM) methods. The results presented in this work show that the waveguide films are amorphous, and their parameters are stable for over a 13 years. The optical losses depend on their thickness and light polarization. Their lowest values are less than 0.06 dB cm-1. The paper presents the results of theoretical analysis of scattering losses on nanocrystals and pores in the bulk and interfaces of the waveguide film. These results combined with experimental data clearly indicate that light scattering at the interface to a glass substrate is the main source of optical losses. Presented waveguide films are suitable for application in evanescent wave sensors.
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Affiliation(s)
- Paweł Karasiński
- Department of Optoelectronics, Silesian University of Technology, ul. B. Krzywoustego 2, 44-100 Gliwice, Poland
| | - Magdalena Zięba
- Department of Optoelectronics, Silesian University of Technology, ul. B. Krzywoustego 2, 44-100 Gliwice, Poland
| | - Ewa Gondek
- Institute of Physics, Cracow University of Technology, ul. Podchorążych 1, 30-084 Kraków, Poland
| | - Jacek Nizioł
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland
| | - Sandeep Gorantla
- Łukasiewicz Research Network—PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
| | - Krzysztof Rola
- Łukasiewicz Research Network—PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
| | - Alicja Bachmatiuk
- Łukasiewicz Research Network—PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
| | - Cuma Tyszkiewicz
- Department of Optoelectronics, Silesian University of Technology, ul. B. Krzywoustego 2, 44-100 Gliwice, Poland
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3
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Ciechanowicz P, Gorantla S, Wełna M, Pieniążek A, Serafińczuk J, Kowalski B, Kudrawiec R, Hommel D. Role of Temperature in Arsenic-Induced Antisurfactant Growth of GaN Microrods. ACS Omega 2022; 7:24777-24784. [PMID: 35874245 PMCID: PMC9301637 DOI: 10.1021/acsomega.2c02777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Due to the antisurfactant properties of arsenic atoms, the self-induced dodecagonal GaN microrods can be grown by molecular beam epitaxy (MBE) in Ga-rich conditions. Since temperature is a key parameter in MBE growth, the role of temperature in the growth of GaN microrods is investigated. The optimal growth temperature window for the formation of GaN microrods is observed to be between 760 and 800 °C. Lowering the temperature to 720 °C did not change the growth mechanism, but the population of irregular and amorphous microrods increased. On the other hand, increasing the growth temperature up to 880 °C interrupts the growth of GaN microrods, due to the re-evaporation of the gallium from the surface. The incorporation of As in GaN microrods is negligible, which is confirmed by X-ray diffraction and transmission electron microscopy. Moreover, the photoluminescence and cathodoluminescence characteristics typical for GaN are observed for individual GaN microrods, which additionally confirms that arsenic is not incorporated inside microrods. When the growth temperature is increased, the emission related to the band gap decreases in favor of the defect-related emission. This is typical for bulk GaN and attributed to an increase in the point defect concentration for GaN microrods grown at lower temperatures.
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Affiliation(s)
- Paulina Ciechanowicz
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Wrocław 54-066, Poland
- Faculty
of Physics and Astronomy, University of
Wrocław, Wrocław 50-137, Poland
| | - Sandeep Gorantla
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Wrocław 54-066, Poland
| | - Monika Wełna
- Department
of Semiconductor Materials Engineering, Wrocław University of Science and Technology, Wrocław 50-370, Poland
| | - Agnieszka Pieniążek
- Department
of Semiconductor Materials Engineering, Wrocław University of Science and Technology, Wrocław 50-370, Poland
| | - Jarosław Serafińczuk
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Wrocław 54-066, Poland
- Department
of Nanometrology, Wroclaw University of
Science and Technology, Janiszewskiego 11/17, Wroclaw 50-372, Poland
| | - Bogdan Kowalski
- Institute
of Physics, Polish Academy of Sciences, Lotników 32/46, Warsaw 02-668, Poland
| | - Robert Kudrawiec
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Wrocław 54-066, Poland
- Department
of Semiconductor Materials Engineering, Wrocław University of Science and Technology, Wrocław 50-370, Poland
| | - Detlef Hommel
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Wrocław 54-066, Poland
- Institute
of Low Temperature and Structure Research, Polish Academy of Sciences, Wrocław 50-422, Poland
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4
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Zdanowicz E, Herman AP, Opołczyńska K, Gorantla S, Olszewski W, Serafińczuk J, Hommel D, Kudrawiec R. Toward h-BN/GaN Schottky Diodes: Spectroscopic Study on the Electronic Phenomena at the Interface. ACS Appl Mater Interfaces 2022; 14:6131-6137. [PMID: 35043636 PMCID: PMC8815035 DOI: 10.1021/acsami.1c20352] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 01/05/2022] [Indexed: 05/27/2023]
Abstract
Hexagonal boron nitride (h-BN), together with other members of the van der Waals crystal family, has been studied for over a decade, both in terms of fundamental and applied research. Up to now, the spectrum of h-BN-based devices has broadened significantly, and systems containing the h-BN/III-V junctions have gained substantial interest as building blocks in, inter alia, light emitters, photodetectors, or transistor structures. Therefore, the understanding of electronic phenomena at the h-BN/III-V interfaces becomes a question of high importance regarding device engineering. In this study, we present the investigation of electronic phenomena at the h-BN/GaN interface by means of contactless electroreflectance (CER) spectroscopy. This nondestructive method enables precise determination of the Fermi level position at the h-BN/GaN interface and the investigation of carrier transport across the interface. CER results showed that h-BN induces an enlargement of the surface barrier height at the GaN surface. Such an effect translates to Fermi level pinning deeper inside the GaN band gap. As an explanation, we propose a mechanism based on electron transfer from GaN surface states to the native acceptor states in h-BN. We reinforced our findings by thorough structural characterization and demonstration of the h-BN/GaN Schottky diode. The surface barriers obtained from CER (0.60 ± 0.09 eV for GaN and 0.91 ± 0.12 eV for h-BN/GaN) and electrical measurements are consistent within the experimental accuracy, proving that CER is an excellent tool for interfacial studies of 2D/III-V hybrids.
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Affiliation(s)
- Ewelina Zdanowicz
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Stabłowicka 147, Wrocław 54-066, Poland
- Department
of Semiconductor Materials Engineering, Wrocław University of Science and Technology, Wyspiańskiego 27, Wrocław 50-370, Poland
| | - Artur P. Herman
- Department
of Semiconductor Materials Engineering, Wrocław University of Science and Technology, Wyspiańskiego 27, Wrocław 50-370, Poland
| | - Katarzyna Opołczyńska
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Stabłowicka 147, Wrocław 54-066, Poland
- Institute
of Experimental Physics, University of Wrocław, pl. M. Borna 9, Wrocław 50-204, Poland
| | - Sandeep Gorantla
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Stabłowicka 147, Wrocław 54-066, Poland
| | - Wojciech Olszewski
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Stabłowicka 147, Wrocław 54-066, Poland
| | - Jarosław Serafińczuk
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Stabłowicka 147, Wrocław 54-066, Poland
- Department
of Nanometrology, Wrocław University
of Science and Technology, Janiszewskiego 11/17, Wrocław 50-372, Poland
| | - Detlef Hommel
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Stabłowicka 147, Wrocław 54-066, Poland
| | - Robert Kudrawiec
- Łukasiewicz
Research Network—PORT Polish Center for Technology Development, Stabłowicka 147, Wrocław 54-066, Poland
- Department
of Semiconductor Materials Engineering, Wrocław University of Science and Technology, Wyspiańskiego 27, Wrocław 50-370, Poland
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5
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Kilanski L, Jedrzejewski R, Sibera D, Kuryliszyn-Kudelska I, Gorantla S, Idczak R, Tran VH, Jedrzejewska A. Magnetic interactions in graphene decorated with iron oxide nanoparticles. Nanotechnology 2021; 32:305703. [PMID: 33789257 DOI: 10.1088/1361-6528/abf3ef] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 03/31/2021] [Indexed: 06/12/2023]
Abstract
We present the studies of structural and magnetic properties of graphene composites prepared with several quantities ofα-Fe2O3dopant of 5%, 25% and 50% made with either ethanol or acetone. Our studies showed the presence of a weak magnetic order up to room temperature and saturation magnetization close to 0.2 emu g-1in pure commercial graphene. With regard to magnetic properties of our graphene + iron oxide samples, the solvent used during the preparation of the composite had a significant influence on them. For graphene + Fe2O3samples made with acetone the magnetic properties of pure graphene played a major role in the overall magnetic susceptibility and magnetization. On the other hand, for graphene + iron oxide samples made with ethanol we observed the presence of superparamagnetic blocking atT < 110 K which was due to the additional appearance ofγ-Fe3O4nanoparticles. Changes in the synthesis solvent played a major role in the magnetic properties of our graphene + Fe2O3nanocomposite samples resulting in much higher saturation magnetization for the samples made with ethanol. Both the shape and the parameters characterizing magnetization hysteresis loops depend strongly on the amount of iron oxide and changes in the preparation method.
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Affiliation(s)
- L Kilanski
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland
| | - R Jedrzejewski
- Łukasiewicz Research Network-PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
| | - D Sibera
- Institute of Chemical and Environment Engineering, West Pomeranian University of Technology, Szczecin, Poland
- Faculty of Civil and Environmental Engineering, West Pomeranian University of Technology in Szczecin, al. Piastów 50a, 70-311 Szczecin, Poland
| | - I Kuryliszyn-Kudelska
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland
| | - S Gorantla
- Łukasiewicz Research Network-PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
| | - R Idczak
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, ul. Okólna 2, 50-422 Wrocław, Poland
- Institute of Experimental Physics, University of Wrocław, pl. M. Borna 9, 50-204 Wrocław, Poland
| | - V H Tran
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, ul. Okólna 2, 50-422 Wrocław, Poland
| | - A Jedrzejewska
- Łukasiewicz Research Network-PORT Polish Center for Technology Development, ul. Stabłowicka 147, 54-066 Wrocław, Poland
- Institute of Chemical and Environment Engineering, West Pomeranian University of Technology, Szczecin, Poland
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6
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Sun X, Zhao S, Bachmatiuk A, Rümmeli MH, Gorantla S, Zeng M, Fu L. 2D Intrinsic Ferromagnetic MnP Single Crystals. Small 2020; 16:e2001484. [PMID: 32529718 DOI: 10.1002/smll.202001484] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 04/24/2020] [Indexed: 06/11/2023]
Abstract
2D intrinsic ferromagnetic materials are highly anticipated in spintronic devices due to their coveted 2D limited magnetism. However, 2D non-layered intrinsic ferromagnets have received sporadic attention, which is largely attributed to the fact that their synthesis is still a great challenge. Significantly, manganese phosphide (MnP) is a promising non-layered intrinsic ferromagnet with excellent properties. Herein, high-quality 2D MnP single crystals formed over liquid metal tin (Sn) is demonstrated through a facile chemical vapor deposition technique. The introduction of liquid metal Sn provides a fertile ground for the growth of 2D MnP single crystals. Interestingly, 2D MnP single crystals maintain their intrinsic ferromagnetism and exhibit a Curie temperature above room temperature. The research enriches the diversity of 2D intrinsic ferromagnetic materials, opening up opportunities for further exploration of their unique properties and rich applications.
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Affiliation(s)
- Xian Sun
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Shasha Zhao
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Alicja Bachmatiuk
- Leibniz Institute for Solid State and Materials Research Dresden, P.O. Box 270116, Dresden, D-01171, Germany
- Polish Center for Technology Development (PORT), Ul. Stabłowicka, Wrocław, 147 54-066, Poland
| | - Mark H Rümmeli
- Leibniz Institute for Solid State and Materials Research Dresden, P.O. Box 270116, Dresden, D-01171, Germany
- Polish Center for Technology Development (PORT), Ul. Stabłowicka, Wrocław, 147 54-066, Poland
- College of Energy Soochow Institute for Energy and Materials Innovations Soochow University Suzhou, Suzhou, 215006, China
- Key Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu Province, Soochow University, Suzhou, 215006, China
| | - Sandeep Gorantla
- Polish Center for Technology Development (PORT), Ul. Stabłowicka, Wrocław, 147 54-066, Poland
| | - Mengqi Zeng
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Lei Fu
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
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Gunnæs AE, Tofan R, Berland K, Gorantla S, Storaas T, Desissa TD, Schrade M, Persson C, Einarsrud MA, Wiik K, Norby T, Kanas N. Chemical stability of Ca 3Co 4−xO 9+δ/CaMnO 3−δ p–n junction for oxide-based thermoelectric generators. RSC Adv 2020; 10:5026-5031. [PMID: 35498303 PMCID: PMC9049286 DOI: 10.1039/c9ra07159h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 01/24/2020] [Indexed: 11/21/2022] Open
Abstract
The heat treatment beneficially affects the performance of an all-oxide thermoelectric generator through phase and element distribution within this p–n junction.
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Affiliation(s)
| | - Raluca Tofan
- Department of Physics
- University of Oslo
- SMN
- FERMiO
- NO-0349 Oslo
| | | | | | - Thomas Storaas
- Department of Physics
- University of Oslo
- SMN
- FERMiO
- NO-0349 Oslo
| | | | | | - Clas Persson
- Department of Physics
- University of Oslo
- SMN
- FERMiO
- NO-0349 Oslo
| | - Mari-Ann Einarsrud
- Department of Material Science and Engineering
- NTNU Norwegian University of Science and Technology
- 7491 Trondheim
- Norway
| | - Kjell Wiik
- Department of Material Science and Engineering
- NTNU Norwegian University of Science and Technology
- 7491 Trondheim
- Norway
| | - Truls Norby
- Department of Chemistry
- University of Oslo
- SMN
- FERMiO
- NO-0349 Oslo
| | - Nikola Kanas
- Department of Material Science and Engineering
- NTNU Norwegian University of Science and Technology
- 7491 Trondheim
- Norway
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8
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Bergum K, Riise HN, Gorantla S, Lindberg PF, Jensen IJT, Gunnæs AE, Galeckas A, Diplas S, Svensson BG, Monakhov E. Improving carrier transport in Cu 2O thin films by rapid thermal annealing. J Phys Condens Matter 2018; 30:075702. [PMID: 29363624 DOI: 10.1088/1361-648x/aaa5f4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Cuprous oxide (Cu2O) is a promising material for large scale photovoltaic applications. The efficiencies of thin film structures are, however, currently lower than those for structures based on Cu2O sheets, possibly due to their poorer transport properties. This study shows that post-deposition rapid thermal annealing (RTA) of Cu2O films is an effective approach for improving carrier transport in films prepared by reactive magnetron sputtering. The as-deposited Cu2O films were poly-crystalline, p-type, with weak near band edge (NBE) emission in photoluminescence spectra, a grain size of ~100 nm and a hole mobility of 2-18 cm2 V-1 s-1. Subsequent RTA (3 min) at a pressure of 50 Pa and temperatures of 600-1000 °C enhanced the NBE by 2-3 orders of magnitude, evidencing improved crystalline quality and reduction of non-radiative carrier recombination. Both grain size and hole mobility were increased considerably upon RTA, reaching values above 1 µm and up to 58 cm2 V-1 s-1, respectively, for films annealed at 900-1000 °C. These films also exhibited a resistivity of ~50-200 Ω cm, a hole concentration of ~1015 cm-3 at room temperature, and a transmittance above 80%.
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Affiliation(s)
- Kristin Bergum
- Department of Physics, Centre for Materials Science and Nanotechnology, University of Oslo, PO Box 1048 Blindern, N-0316 Oslo, Norway
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Bezkrovnyi O, Małecka MA, Lisiecki R, Ostroushko V, Thomas AG, Gorantla S, Kepinski L. The effect of Eu doping on the growth, structure and red-ox activity of ceria nanocubes. CrystEngComm 2018. [DOI: 10.1039/c8ce00155c] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ordering of oxygen vacancies (in high Eu-doped (x ≥ 0.1) ceria nanoparticles) facilitates the process of Ce4+ to Ce3+ reduction.
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Affiliation(s)
- Oleksii Bezkrovnyi
- W. Trzebiatowski Institute of Low Temperature and Structure Research Polish Academy of Sciences
- Wroclaw
- Poland
| | - Małgorzata A. Małecka
- W. Trzebiatowski Institute of Low Temperature and Structure Research Polish Academy of Sciences
- Wroclaw
- Poland
| | - Radoslaw Lisiecki
- W. Trzebiatowski Institute of Low Temperature and Structure Research Polish Academy of Sciences
- Wroclaw
- Poland
| | | | - Andrew G. Thomas
- School of Materials and the Photon Science Institute
- The University of Manchester
- UK
| | | | - Leszek Kepinski
- W. Trzebiatowski Institute of Low Temperature and Structure Research Polish Academy of Sciences
- Wroclaw
- Poland
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10
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Jensen IJT, Gorantla S, Løvvik OM, Gan J, Nguyen PD, Monakhov E, Svensson BG, Gunnæs AE, Diplas S. Interface phenomena in magnetron sputtered Cu 2O/ZnO heterostructures. J Phys Condens Matter 2017; 29:435002. [PMID: 28829336 DOI: 10.1088/1361-648x/aa8799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The interface between ZnO and Cu2O has been predicted to be a good candidate for use in thin film solar cells. However, the high predicted conversion efficiency has yet to be fully realized experimentally. To explore the underlying causes of this we investigate the interface between ZnO and Cu2O in magnetron sputtered samples. Two different sample geometries were made: In the first set thin layers of ZnO were deposited on Cu2O (type A), while in the second set the order was reversed (type B). Using x-ray photoelectron spectroscopy (XPS), an intermediate CuO layer was identified regardless of the order in which the Cu2O and ZnO layers were deposited. The presence of a CuO layer was supported by transmission electron microscopy (TEM) results. Changes in the electron hole screening conditions were observed in CuO near the interface with ZnO, manifested as changes in the relative peak-to-satellite ratio and the degree of asymmetric broadness in the Cu 2p peak. The suppression of the Cu 2p satellite characteristic of CuO may cause the CuO presence to be overlooked and cause errors in determinations of valence band offsets (VBOs). For the type A samples, we compare four different approaches to XPS-based determination of VBO and find that the most reliable results are obtained when the thin CuO layer and the altered screening conditions at the interface were taken into account. The VBOs were found to range between 2.5 eV and 2.8 eV. For the B type samples a reduction of the Cu 2p-LMM Auger parameter was found as compared to bulk Cu2O, indicative of quantum confinement in the Cu2O overlayer.
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Affiliation(s)
- I J T Jensen
- SINTEF Materials and Chemistry, P/O box 124 Blindern, 0314 Oslo, Norway
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11
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Ta HQ, Perello DJ, Duong DL, Han GH, Gorantla S, Nguyen VL, Bachmatiuk A, Rotkin SV, Lee YH, Rümmeli MH. Stranski-Krastanov and Volmer-Weber CVD Growth Regimes To Control the Stacking Order in Bilayer Graphene. Nano Lett 2016; 16:6403-6410. [PMID: 27683947 DOI: 10.1021/acs.nanolett.6b02826] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Aside from unusual properties of monolayer graphene, bilayer has been shown to have even more interesting physics, in particular allowing bandgap opening with dual gating for proper interlayer symmetry. Such properties, promising for device applications, ignited significant interest in understanding and controlling the growth of bilayer graphene. Here we systematically investigate a broad set of flow rates and relative gas ratio of CH4 to H2 in atmospheric pressure chemical vapor deposition of multilayered graphene. Two very different growth windows are identified. For relatively high CH4 to H2 ratios, graphene growth is relatively rapid with an initial first full layer forming in seconds upon which new graphene flakes nucleate then grow on top of the first layer. The stacking of these flakes versus the initial graphene layer is mostly turbostratic. This growth mode can be likened to Stranski-Krastanov growth. With relatively low CH4 to H2 ratios, growth rates are reduced due to a lower carbon supply rate. In addition bi-, tri-, and few-layer flakes form directly over the Cu substrate as individual islands. Etching studies show that in this growth mode subsequent layers form beneath the first layer presumably through carbon radical intercalation. This growth mode is similar to that found with Volmer-Weber growth and was shown to produce highly oriented AB-stacked materials. These systematic studies provide new insight into bilayer graphene formation and define the synthetic range where gapped bilayer graphene can be reliably produced.
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Affiliation(s)
- Huy Q Ta
- College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University , Suzhou 215006, China
- Centre of Polymer and Carbon Materials, Polish Academy of Sciences , M. Curie-Sklodowskiej 34, Zabrze 41-819, Poland
- Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - David J Perello
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Dinh Loc Duong
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Gang Hee Han
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Sandeep Gorantla
- Department of Physics, University of Oslo , Blindern, P.O. Box 1048, 0316 Oslo, Norway
| | - Van Luan Nguyen
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Alicja Bachmatiuk
- Centre of Polymer and Carbon Materials, Polish Academy of Sciences , M. Curie-Sklodowskiej 34, Zabrze 41-819, Poland
- IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
| | - Slava V Rotkin
- Department of Physics and Center for Advanced Materials and Nanotechnology, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
- Department of Energy Science, Department of Physics, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Mark H Rümmeli
- College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University , Suzhou 215006, China
- Centre of Polymer and Carbon Materials, Polish Academy of Sciences , M. Curie-Sklodowskiej 34, Zabrze 41-819, Poland
- IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
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12
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Senanayake TH, Gorantla S, Makarov E, Lu Y, Warren G, Vinogradov SV. Nanogel-Conjugated Reverse Transcriptase Inhibitors and Their Combinations as Novel Antiviral Agents with Increased Efficacy against HIV-1 Infection. Mol Pharm 2015; 12:4226-36. [PMID: 26565115 DOI: 10.1021/acs.molpharmaceut.5b00424] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Nucleoside reverse transcriptase inhibitors (NRTIs) are an integral part of the current antiretroviral therapy (ART), which dramatically reduced the mortality from AIDS and turned the disease from lethal to chronic. The further steps in curing the HIV-1 infection must include more effective targeting of infected cells and virus sanctuaries inside the body and modification of drugs and treatment schedules to reduce common complications of the long-term treatment and increase patient compliancy. Here, we describe novel NRTI prodrugs synthesized from cholesteryl-ε-polylysine (CEPL) nanogels by conjugation with NRTI 5'-succinate derivatives (sNRTI). Biodegradability, small particle size, and high NRTI loading (30% by weight) of these conjugates; extended drug release, which would allow a weekly administration schedule; high therapeutic index (>1000) with a lower toxicity compared to NRTIs; and efficient accumulation in macrophages known as carriers for HIV-1 infection are among the most attractive properties of new nanodrugs. Nanogel conjugates of zidovudine (AZT), lamivudine (3TC), and abacavir (ABC) have been investigated individually and in formulations similar to clinical NRTI cocktails. Nanodrug formulations demonstrated 10-fold suppression of reverse transcriptase activity (EC90) in HIV-infected macrophages at 2-10, 2-4, and 1-2 μM drug levels, respectively, for single nanodrugs and dual and triple nanodrug cocktails. Nanogel conjugate of lamivudine was the most effective single nanodrug (EC90 2 μM). Nanodrugs showed a more favorable pharmacokinetics compared to free NRTIs. Infrequent iv injections of PEGylated CEPL-sAZT alone could efficiently suppress HIV-1 RT activity to background level in humanized mouse (hu-PBL) HIV model.
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Affiliation(s)
- T H Senanayake
- Department of Pharmaceutical Sciences, College of Pharmacy, and ‡Department of Pharmacology and Experimental Neuroscience, College of Medicine, University of Nebraska Medical Center , Omaha, Nebraska 68198, United States
| | - S Gorantla
- Department of Pharmaceutical Sciences, College of Pharmacy, and ‡Department of Pharmacology and Experimental Neuroscience, College of Medicine, University of Nebraska Medical Center , Omaha, Nebraska 68198, United States
| | - E Makarov
- Department of Pharmaceutical Sciences, College of Pharmacy, and ‡Department of Pharmacology and Experimental Neuroscience, College of Medicine, University of Nebraska Medical Center , Omaha, Nebraska 68198, United States
| | - Y Lu
- Department of Pharmaceutical Sciences, College of Pharmacy, and ‡Department of Pharmacology and Experimental Neuroscience, College of Medicine, University of Nebraska Medical Center , Omaha, Nebraska 68198, United States
| | - G Warren
- Department of Pharmaceutical Sciences, College of Pharmacy, and ‡Department of Pharmacology and Experimental Neuroscience, College of Medicine, University of Nebraska Medical Center , Omaha, Nebraska 68198, United States
| | - S V Vinogradov
- Department of Pharmaceutical Sciences, College of Pharmacy, and ‡Department of Pharmacology and Experimental Neuroscience, College of Medicine, University of Nebraska Medical Center , Omaha, Nebraska 68198, United States
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13
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Grimm D, Wilson RB, Teshome B, Gorantla S, Rümmeli MH, Bublat T, Zallo E, Li G, Cahill DG, Schmidt OG. Thermal conductivity of mechanically joined semiconducting/metal nanomembrane superlattices. Nano Lett 2014; 14:2387-2393. [PMID: 24738656 DOI: 10.1021/nl404827j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The decrease of thermal conductivity is crucial for the development of efficient thermal energy converters. Systems composed of a periodic set of very thin layers show among the smallest thermal conductivities reported to-date. Here, we fabricate in an unconventional but straightforward way hybrid superlattices consisting of a large number of nanomembranes mechanically stacked on top of each other. The superlattices can consist of an arbitrary composition of n- or p-type doped single-crystalline semiconductors and a polycrystalline metal layer. These hybrid multilayered systems are fabricated by taking advantage of the self-rolling technique. First, differentially strained nanomembranes are rolled into three-dimensional microtubes with multiple windings. By applying vertical pressure, the tubes are then compressed and converted into a planar hybrid superlattice. The thermal measurements show a substantial reduction of the cross-sectional heat transport through the nanomembrane superlattice compared to a single nanomembrane layer. Time-domain thermoreflectance measurements yield thermal conductivity values below 2 W m(-1) K(-1). Compared to bulk values, this represents a reduction of 2 orders of magnitude by the incorporation of the mechanically joined interfaces. The scanning thermal atomic force microscopy measurements support the observation of reduced thermal transport on top of the superlattices. In addition, small defects with a spatial resolution of ∼100 nm can be resolved in the thermal maps. The low thermal conductivity reveals the potential of this approach to fabricate miniaturized on-chip solutions for energy harvesters in, e.g., microautonomous systems.
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Affiliation(s)
- Daniel Grimm
- Material Systems for Nanoelectronics, Technische Universität Chemnitz , 09111 Chemnitz, Germany
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14
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Gorantla S, Bachmatiuk A, Hwang J, Alsalman HA, Kwak JY, Seyller T, Eckert J, Spencer MG, Rümmeli MH. A universal transfer route for graphene. Nanoscale 2014; 6:889-896. [PMID: 24270801 DOI: 10.1039/c3nr04739c] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Often synthetic graphene requires transfer onto an arbitrary substrate prior to use because the substrate it was originally synthesized on is inappropriate for either electrical measurement or characterization. While a variety of routes have been developed they are substrate dependant and often involve the use of harsh treatments. Here we present a facile and cheap route that can be applied to graphene over any substrate. This universal transfer route is based on a wet chemical reaction producing gaseous species which can intercalate between the substrate and the graphene and thus gently delaminate the two.
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Affiliation(s)
- Sandeep Gorantla
- IFW Dresden, Institute for Complex Materials, PO Box 270116, 01171 Dresden, Germany
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15
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Hwang J, Kim M, Campbell D, Alsalman HA, Kwak JY, Shivaraman S, Woll AR, Singh AK, Hennig RG, Gorantla S, Rümmeli MH, Spencer MG. van der Waals epitaxial growth of graphene on sapphire by chemical vapor deposition without a metal catalyst. ACS Nano 2013; 7:385-395. [PMID: 23244231 DOI: 10.1021/nn305486x] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
van der Waals epitaxial growth of graphene on c-plane (0001) sapphire by CVD without a metal catalyst is presented. The effects of CH(4) partial pressure, growth temperature, and H(2)/CH(4) ratio were investigated and growth conditions optimized. The formation of monolayer graphene was shown by Raman spectroscopy, optical transmission, grazing incidence X-ray diffraction (GIXRD), and low voltage transmission electron microscopy (LVTEM). Electrical analysis revealed that a room temperature Hall mobility above 2000 cm(2)/V·s was achieved, and the mobility and carrier type were correlated to growth conditions. Both GIXRD and LVTEM studies confirm a dominant crystal orientation (principally graphene [10-10] || sapphire [11-20]) for about 80-90% of the material concomitant with epitaxial growth. The initial phase of the nucleation and the lateral growth from the nucleation seeds were observed using atomic force microscopy. The initial nuclei density was ~24 μm(-2), and a lateral growth rate of ~82 nm/min was determined. Density functional theory calculations reveal that the binding between graphene and sapphire is dominated by weak dispersion interactions and indicate that the epitaxial relation as observed by GIXRD is due to preferential binding of small molecules on sapphire during early stages of graphene formation.
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Affiliation(s)
- Jeonghyun Hwang
- School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA.
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16
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Grimm D, Bof Bufon CC, Deneke C, Atkinson P, Thurmer DJ, Schäffel F, Gorantla S, Bachmatiuk A, Schmidt OG. Rolled-up nanomembranes as compact 3D architectures for field effect transistors and fluidic sensing applications. Nano Lett 2013; 13:213-218. [PMID: 23245385 DOI: 10.1021/nl303887b] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We fabricate inorganic thin film transistors with bending radii of less than 5 μm maintaining their high electronic performance with on-off ratios of more than 10(5) and subthreshold swings of 160 mV/dec. The fabrication technology relies on the roll-up of highly strained semiconducting nanomembranes, which compacts planar transistors into three-dimensional tubular architectures opening intriguing potential for microfluidic applications. Our technique probes the ultimate limit for the bending radius of high performance thin film transistors.
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Affiliation(s)
- Daniel Grimm
- Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany.
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17
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Börrnert F, Fu L, Gorantla S, Knupfer M, Büchner B, Rümmeli MH. Programmable sub-nanometer sculpting of graphene with electron beams. ACS Nano 2012; 6:10327-10334. [PMID: 23110721 DOI: 10.1021/nn304256a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Electron beams in transmission electron microscopes are very attractive to engineer and pattern graphene toward all-carbon device fabrication. The use of condensed beams typically used for sequential raster imaging is particularly exciting since they potentially provide high degrees of precision. However, technical difficulties, such as the formation of electron beam induced deposits on sample surfaces, have hindered the development of this technique. We demonstrate how one can successfully use a condensed electron beam, either with or without C(s) correction, to structure graphene with sub-nanometer precision in a programmable manner. We further demonstrate the potential of the developed technique by combining it with an established route to engineer graphene nanoribbons to single-atom carbon chains.
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18
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Bonab AA, Fricchione JG, Gorantla S, Vitalo AG, Auster ME, Levine SJ, Scichilone JM, Hegde M, Foote W, Fricchione GL, Denninger JW, Yarmush DM, Fischman AJ, Yarmush ML, Levine JB. Isolation rearing significantly perturbs brain metabolism in the thalamus and hippocampus. Neuroscience 2012; 223:457-64. [PMID: 22835621 DOI: 10.1016/j.neuroscience.2012.07.032] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 07/16/2012] [Accepted: 07/17/2012] [Indexed: 01/04/2023]
Abstract
Psychosocial neglect during childhood severely impairs both behavioral and physical health. The isolation rearing model in rodents has been employed by our group and others to study this clinical problem at a basic level. We previously showed that immediate early gene (IEG) expression in the hippocampus and medial prefrontal cortex (mPFC) is decreased in isolation-reared (IR) compared to group-reared (GR) rats. In the current study, we sought to evaluate: (1) whether these changes in IEG expression would be detected by the measurement of brain glucose metabolism using positron emission tomography (PET) with fluorodeoxyglucose (FDG) and (2) whether PET FDG could illuminate other brain regions with different glucose metabolism in IR compared to GR rats. We found that there were significant differences in FDG uptake in the hippocampus that were consistent with our findings for IEG expression (decreased mean FDG uptake in IR rats). In contrast, in the mPFC, the FDG uptake between IR and GR rats did not differ. Finally, we found decreased mean FDG uptake in the thalamus of the IR rats, a region we had not previously examined. The results suggest that PET FDG has the potential to be utilized as a biomarker of molecular changes in the hippocampus. Further, the differences found in thalamic brain FDG uptake suggest that further investigation of this region at the molecular and cellular levels may provide an important insight into the neurobiological basis of the adverse clinical outcomes found in children exposed to psychosocial deprivation.
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Affiliation(s)
- A A Bonab
- Department of Nuclear Medicine, Massachusetts General Hospital, United States
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19
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Dimitrakopoulou M, Gorantla S, Thomas J, Gemming T, Cuniberti G, Büchner B, Rümmeli MH. Understanding the growth of amorphous SiO2 nanofibers and crystalline binary nanoparticles produced by laser ablation. Nanotechnology 2012; 23:035601. [PMID: 22173480 DOI: 10.1088/0957-4484/23/3/035601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The pulsed-laser evaporation synthesis of silica nanofibers and crystalline binary nanoparticles is investigated in detail. By careful adjustment of the synthesis parameters one can tailor the product to form high yield nanofibers or binary nanoparticles. Some control on their diameters is also possible through the synthesis parameters. Oxidation of the nanofibers occurs upon exposure to air after the reaction.
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Affiliation(s)
- Maria Dimitrakopoulou
- Leibniz Institute for Solid State and Materials Research (IFW), Helmholtzstraße 20, D-01069 Dresden, Germany.
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20
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Gorantla S, Börrnert F, Bachmatiuk A, Dimitrakopoulou M, Schönfelder R, Schäffel F, Thomas J, Gemming T, Borowiak-Palen E, Warner JH, Yakobson BI, Eckert J, Büchner B, Rümmeli MH. In situ observations of fullerene fusion and ejection in carbon nanotubes. Nanoscale 2010; 2:2077-2079. [PMID: 20714658 DOI: 10.1039/c0nr00426j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We present in situ experimental observations of fullerenes seamlessly fusing to single-walled carbon nanotubes. The morphing-entry of a fullerene to the interior of a nanotube is also captured. The confined (1D) motion of the newly-encapsulated fullerene within its host attests to the actual change from the exterior to interior.
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21
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Kalbáč M, Kavan L, Gorantla S, Gemming T, Dunsch L. Sexithiophene Encapsulated in a Single-Walled Carbon Nanotube: An In Situ Raman Spectroelectrochemical Study of a Peapod Structure. Chemistry 2010; 16:11753-9. [DOI: 10.1002/chem.201001417] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Indexed: 11/11/2022]
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22
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Pauly S, Gorantla S, Wang G, Kühn U, Eckert J. Transformation-mediated ductility in CuZr-based bulk metallic glasses. Nat Mater 2010; 9:473-477. [PMID: 20473286 DOI: 10.1038/nmat2767] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2009] [Accepted: 04/09/2010] [Indexed: 05/29/2023]
Abstract
Bulk metallic glasses (BMGs) generally fail in a brittle manner under uniaxial, quasistatic loading at room temperature. The lack of plastic strain is a consequence of shear softening, a phenomenon that originates from shear-induced dilation that causes plastic strain to be highly localized in shear bands. So far, significant tensile ductility has been reported only for microscopic samples of around 100 nm (ref. 4) as well as for high strain rates, and so far no mechanisms are known, which could lead to work hardening and ductility in quasistatic tension in macroscopic BMG samples. In the present work we developed CuZr-based BMGs, which polymorphically precipitate nanocrystals during tensile deformation and subsequently these nanocrystals undergo twinning. The formation of such structural heterogeneities hampers shear band generation and results in macroscopically detectable plastic strain and work hardening. The precipitation of nanocrystals and their subsequent twinning can be understood in terms of a deformation-induced softening of the instantaneous shear modulus. This unique deformation mechanism is believed to be not just limited to CuZr-based BMGs but also to promote ductility in other BMGs.
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Bai J, Gorantla S, Banda N, Cagnon L, Rossi J, Akkina R. Characterization of anti-CCR5 ribozyme-transduced CD34+ hematopoietic progenitor cells in vitro and in a SCID-hu mouse model in vivo. Mol Ther 2000; 1:244-54. [PMID: 10933940 DOI: 10.1006/mthe.2000.0038] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cellular entry of HIV is mediated by the specific interaction of viral envelope glycoproteins with the cell-surface marker CD4 and a chemokine receptor (CCR5 or CXCR4). Individuals with a 32-base-pair (bp) deletion in the CCR5 coding region, which results in a truncated peptide, show resistance to HIV-1 infection. This suggests that the downregulation of CCR5 expression on target cells may prevent HIV infection. Therefore, ribozymes that inhibit the CCR5 expression offer a novel approach for anti-HIV gene therapy. To assess the effect of an anti-CCR5 ribozyme (R5Rbz) on macrophage differentiation, CD34+ hematopoietic progenitor cells were transduced with a retroviral vector carrying RSRbz and allowed to differentiate in the presence of appropriate cytokines. R5Rbz-transduced CD34+ cells differentiated normally into mature macrophages that carried CD14 and CD4 surface markers, expressed the anti-CCR5 ribozyme, and showed significant resistance to viral infection upon challenge with the HIV-1 BaL strain. Using an in vivo thymopoiesis model, the effect of RSRbz on stem cell differentiation into thymocytes was evaluated by reconstituting SCID-hu mice thymic grafts with ribozyme-transduced CD34+ cells. FACS analysis of cell biopsies at 4 and 6 weeks postengraftment for HLA, CD4, and CD8 markers showed comparable levels of reconstitution and similar percentages of subpopulations of thymocytes between grafts receiving R5Rbz-transduced and control CD34+ cells. RT-PCR assays demonstrated the expression of the anti-CCR5 ribozyme in CD4+, CD8+, and CD4+/CD8+ thymocyte subsets derived from RSRbz-transduced CD34+ cells. These results indicate that anti-CCR5 ribozyme can be introduced into hematopoietic stem cells without adverse effects on their subsequent lineage-specific differentiation and maturation. The expression of anti-CCR5 ribozymes in HIV-1 target cells offers a novel gene therapy strategy to control HIV infection.
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Affiliation(s)
- J Bai
- Department of Pathology, Colorado State University, Fort Collins 80523, USA
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