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Potisk T, Remškar M, Pirker L, Filipič G, Mihelič I, Ješelnik M, Čoko U, Ravnik M. Single-Layer and Double-Layer Filtration Materials Based on Polyvinylidene Fluoride-Co-hexafluoropropylene Nanofibers Coated on Melamine Microfibers. ACS Appl Nano Mater 2023; 6:15807-15819. [PMID: 37706065 PMCID: PMC10496027 DOI: 10.1021/acsanm.3c02592] [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] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 08/08/2023] [Indexed: 09/15/2023]
Abstract
In this work, we demonstrate selected optimization changes in the simple design of filtration masks to increase particle removal efficiency (PRE) and filter quality factor by combining experiments and numerical modeling. In particular, we focus on single-layer filters fabricated from uniform thickness fibers and double-layer filters consisting of a layer of highly permeable thick fibers as a support and a thin layer of filtering electrospun nanofibers. For single-layer filters, we demonstrate performance improvement in terms of the quality factor by optimizing the geometry of the composition. We show significantly better PRE performance for filters composed of micrometer-sized fibers covered by a thin layer of electrospun nanofibers. This work is motivated and carried out in collaboration with a targeted industrial development of selected melamine-based filter nano- and micromaterials.
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Affiliation(s)
- Tilen Potisk
- Laboratory
for Molecular Modeling, National Institute
of Chemistry, SI-1001 Ljubljana, Slovenia
- Faculty
of Mathematics and Physics, University of
Ljubljana, SI-1001 Ljubljana, Slovenia
| | - Maja Remškar
- Jožef
Stefan Institute, SI-1000 Ljubljana, Slovenia
| | - Luka Pirker
- Jožef
Stefan Institute, SI-1000 Ljubljana, Slovenia
- J. Heyrovsky
Institute of Physical Chemistry, Czech Academy
of Sciences, 182 23 Prague 8, Czech Republic
| | | | | | | | - Urban Čoko
- Laboratory
for Molecular Modeling, National Institute
of Chemistry, SI-1001 Ljubljana, Slovenia
- Faculty
of Mathematics and Physics, University of
Ljubljana, SI-1001 Ljubljana, Slovenia
| | - Miha Ravnik
- Faculty
of Mathematics and Physics, University of
Ljubljana, SI-1001 Ljubljana, Slovenia
- Jožef
Stefan Institute, SI-1000 Ljubljana, Slovenia
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2
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Filipič G, Pirker L, Krajnc AP, Ješelnik M, Remškar M. Enhanced Filtration Efficiency of Natural Materials with the Addition of Electrospun Poly(vinylidene fluoride-co-hexafluoropropylene) Fibres. Materials (Basel) 2023; 16:2314. [PMID: 36984195 PMCID: PMC10054789 DOI: 10.3390/ma16062314] [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: 01/16/2023] [Revised: 03/09/2023] [Accepted: 03/11/2023] [Indexed: 06/18/2023]
Abstract
Pollutants and infectious diseases can spread through air with airborne droplets and aerosols. A respiratory mask can decrease the amount of pollutants we inhale and it can protect us from airborne diseases. With the onset of the COVID-19 pandemic, masks became an everyday item used by a lot of people around the world. As most of them are for a single use, the amount of non-recyclable waste increased dramatically. The plastic from which the masks are made pollutes the environment with various chemicals and microplastic. Here, we investigated the time- and size-dependent filtration efficiency (FE) of aerosols in the range of 25.9 to 685.4 nm of five different natural materials whose FE was enhanced using electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF) fibres. A scanning electron microscope (SEM) was used to determine the morphology and structure of the natural materials as well as the thickness of the PVDF fibres, while the phase of the electrospun fibres was determined by Raman spectroscopy. A thin layer of the electrospun PVDF fibres with the same grammage was sandwiched between two sheets of natural materials, and their FE increased up to 80%. By varying the grammature of the electrospun polymer, we tuned the FE of cotton from 82.6 to 99.9%. Thus, through the optimization of the grammage of the electrospun polymer, the amount of plastic used in the process can be minimized, while achieving sufficiently high FE.
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Affiliation(s)
- Gregor Filipič
- Jozef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia
| | - Luka Pirker
- Jozef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia
- Department of Electrochemical Materials, J. Heyrovsky Institute of Physical Chemistry, Dolejškova 3, 182 23 Prague, Czech Republic
| | - Anja Pogačnik Krajnc
- Jozef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia
- Faculty of Mathematics and Physics, University of Ljubljana, Jadranska Ulica 19, 1000 Ljubljana, Slovenia
| | - Marjan Ješelnik
- smartMelamine d.o.o., Tomšičeva Cesta 9, 1330 Kočevje, Slovenia
| | - Maja Remškar
- Jozef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia
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3
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Schock RTK, Neuwald J, Möckel W, Kronseder M, Pirker L, Remškar M, Hüttel AK. Non-Destructive Low-Temperature Contacts to MoS 2 Nanoribbon and Nanotube Quantum Dots. Adv Mater 2023; 35:e2209333. [PMID: 36624967 DOI: 10.1002/adma.202209333] [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: 10/10/2022] [Revised: 12/15/2022] [Indexed: 06/17/2023]
Abstract
Molybdenum disulfide nanoribbons and nanotubes are quasi-1D semiconductors with strong spin-orbit interaction, a nanomaterial highly promising for quantum electronic applications. Here, it is demonstrated that a bismuth semimetal layer between the contact metal and this nanomaterial strongly improves the properties of the contacts. Two-point resistances on the order of 100 kΩ are observed at room temperature. At cryogenic temperature, Coulomb blockade is visible. The resulting stability diagrams indicate a marked absence of trap states at the contacts and the corresponding disorder, compared to previous devices that use low-work-function metals as contacts. Single-level quantum transport is observed at temperatures below 100 mK.
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Affiliation(s)
- Robin T K Schock
- Institute for Experimental and Applied Physics, University of Regensburg, 93040, Regensburg, Germany
| | - Jonathan Neuwald
- Institute for Experimental and Applied Physics, University of Regensburg, 93040, Regensburg, Germany
| | - Wolfgang Möckel
- Institute for Experimental and Applied Physics, University of Regensburg, 93040, Regensburg, Germany
| | - Matthias Kronseder
- Institute for Experimental and Applied Physics, University of Regensburg, 93040, Regensburg, Germany
| | - Luka Pirker
- Solid State Physics Department, Jožef Stefan Institute, 1000, Ljubljana, Slovenia
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Czech Academy of Sciences, 182 23, Prague, Czech Republic
| | - Maja Remškar
- Solid State Physics Department, Jožef Stefan Institute, 1000, Ljubljana, Slovenia
| | - Andreas K Hüttel
- Institute for Experimental and Applied Physics, University of Regensburg, 93040, Regensburg, Germany
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4
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Višić B, Pirker L, Opačić M, Milosavljević A, Lazarević N, Majaron B, Remškar M. Influence of crystal structure and oxygen vacancies on optical properties of nanostructured multi-stoichiometric tungsten suboxides. Nanotechnology 2022; 33:275705. [PMID: 35358963 DOI: 10.1088/1361-6528/ac6316] [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: 03/08/2022] [Accepted: 03/31/2022] [Indexed: 06/14/2023]
Abstract
Four distinct tungsten suboxide (WO3-x) nanomaterials were synthesized via chemical vapour transport reaction and the role of their crystal structures on the optical properties was studied. These materials grow either as thin, quasi-2D crystals with the WnO3n-1formula (in shape of platelets or nanotiles), or as nanowires (W5O14, W18O49). For the quasi-2D materials, the appearance of defect states gives rise to two indirect absorption edges. One is assigned to the regular bandgap occurring between the valence and the conduction band, while the second is a defect-induced band. While the bandgap values of platelets and nanotiles are in the upper range of the reported values for the suboxides, the nanowires' bandgaps are lower due to the higher number of free charge carriers. Both types of nanowires sustain localized surface plasmon resonances, as evidenced from the extinction measurements, whereas the quasi-2D materials exhibit excitonic transitions. All four materials have photoluminescence emission peaks in the UV region. The interplay of the crystal structure, oxygen vacancies and shape can result in changes in optical behaviour, and the understanding of these effects could enable intentional tuning of selected properties.
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Affiliation(s)
- Bojana Višić
- Department of Condensed Matter Physics, Jozef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia
- Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
| | - Luka Pirker
- Department of Condensed Matter Physics, Jozef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia
| | - Marko Opačić
- Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
| | - Ana Milosavljević
- Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
| | - Nenad Lazarević
- Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
| | - Boris Majaron
- Department of Complex Matter, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
- Faculty of Physics and Mathematics, University of Ljubljana, Jadranska 19, Slovenia
| | - Maja Remškar
- Department of Condensed Matter Physics, Jozef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia
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Affiliation(s)
- Luka Pirker
- Solid State Physics Jozef Stefan Institute Jamova cesta 39 1000 Ljubljana Slovenia
| | - Bojana Višić
- Solid State Physics Jozef Stefan Institute Jamova cesta 39 1000 Ljubljana Slovenia
- Institute of Physics Belgrade University of Belgrade Pregrevica 118 11080 Belgrade Serbia
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Pirker L, Višić B, Kovač J, Škapin SD, Remškar M. Synthesis and Characterization of Tungsten Suboxide W nO 3n-1 Nanotiles. Nanomaterials (Basel) 2021; 11:nano11081985. [PMID: 34443817 PMCID: PMC8398204 DOI: 10.3390/nano11081985] [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] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 07/30/2021] [Accepted: 07/30/2021] [Indexed: 11/16/2022]
Abstract
WnO3n-1 nanotiles, with multiple stoichiometries within one nanotile, were synthesized via the chemical vapour transport method. They grow along the [010] crystallographic axis, with the thickness ranging from a few tens to a few hundreds of nm, with the lateral size up to several µm. Distinct surface corrugations, up to a few 10 nm deep appear during growth. The {102}r crystallographic shear planes indicate the WnO3n-1 stoichiometries. Within a single nanotile, six stoichiometries were detected, namely W16O47 (WO2.938), W15O44 (WO2.933), W14O41 (WO2.928), W13O38 (WO2.923), W12O35 (WO2.917), and W11O32 (WO2.909), with the last three never being reported before. The existence of oxygen vacancies within the crystallographic shear planes resulted in the observed non-zero density of states at the Fermi energy.
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Affiliation(s)
- Luka Pirker
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia; (L.P.); (J.K.); (S.D.Š.); (M.R.)
| | - Bojana Višić
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia; (L.P.); (J.K.); (S.D.Š.); (M.R.)
- Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
- Correspondence:
| | - Janez Kovač
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia; (L.P.); (J.K.); (S.D.Š.); (M.R.)
| | - Srečo D. Škapin
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia; (L.P.); (J.K.); (S.D.Š.); (M.R.)
| | - Maja Remškar
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia; (L.P.); (J.K.); (S.D.Š.); (M.R.)
- Faculty for Mathematics and Physics, University of Ljubljana, Jadranska Ulica 19, 1000 Ljubljana, Slovenia
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Pohlen M, Pirker L, Dreu R. The Potential of Macroporous Silica-Nanocrystalline Cellulose Combination for Formulating Dry Emulsion Systems with Improved Flow Properties: A DoE Study. Pharmaceutics 2021; 13:pharmaceutics13081177. [PMID: 34452137 PMCID: PMC8399492 DOI: 10.3390/pharmaceutics13081177] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 07/28/2021] [Accepted: 07/28/2021] [Indexed: 12/02/2022] Open
Abstract
The objective of this study was to explore the possible use of a new combination of two excipients, i.e., nanocrystalline cellulose (NCC) and macroporous silica (MS), as matrix materials for the compounding of dry emulsion systems and the effects these two excipients have on the characteristics of dry emulsion powders produced by the spray drying process. A previously developed liquid O/W nanoemulsion, comprised of simvastatin, 1-oleoyl-rac-glycerol, Miglyol 812 and Tween 20, was employed. In order to comprehend the effects that these two matrix formers have on the spray drying process and on dry emulsion powder characteristics, alone and in combination, a DoE (Design of Experiment) approach was used. The physicochemical properties of dry emulsion samples were characterised by atomic force microscopy, scanning electron microscopy, mercury intrusion porosimetry, energy-dispersive X-ray spectroscopy and laser diffraction analysis. Additionally, total release and dissolution experiments were performed to assess drug release from multiple formulations. It was found that the macroporous silica matrix drastically improved flow properties of dry emulsion powders; however, it partially trapped the oil—drug mixture inside the pores and hindered complete release. NCC showed its potential to reduce oil entrapment in MS, but because of its rod-shaped particles deposited on the MS surface, powder flowability was deteriorated.
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Affiliation(s)
- Mitja Pohlen
- Faculty of Pharmacy, University of Ljubljana, Aškerčeva Cesta 7, SI-1000 Ljubljana, Slovenia;
| | - Luka Pirker
- Jožef Stefan Institute, Jamova Cesta 39, SI-1000 Ljubljana, Slovenia;
| | - Rok Dreu
- Faculty of Pharmacy, University of Ljubljana, Aškerčeva Cesta 7, SI-1000 Ljubljana, Slovenia;
- Correspondence: ; Tel.: +386-1-47-69-622; Fax: +386-1-47-69-512
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8
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Pogačnik Krajnc A, Pirker L, Gradišar Centa U, Gradišek A, Mekjavic IB, Godnič M, Čebašek M, Bregant T, Remškar M. Size- and Time-Dependent Particle Removal Efficiency of Face Masks and Improvised Respiratory Protection Equipment Used during the COVID-19 Pandemic. Sensors (Basel) 2021; 21:1567. [PMID: 33668141 PMCID: PMC7956512 DOI: 10.3390/s21051567] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 02/16/2021] [Accepted: 02/20/2021] [Indexed: 12/21/2022]
Abstract
Size- and time-dependent particle removal efficiency (PRE) of different protective respiratory masks were determined using a standard aerosol powder with the size of particles in the range of an uncoated SARS-CoV-2 virus and small respiratory droplets. Number concentration of particles was measured by a scanning mobility particle sizer. Respiratory protective half-masks, surgical masks, and cotton washable masks were tested. The results show high filtration efficiency of FFP2, FFP3, and certified surgical masks for all sizes of tested particles, while protection efficiency of washable masks depends on their constituent fabrics. Measurements showed decreasing PRE of all masks over time due to transmission of nanoparticles through the mask-face interface. On the other hand, the PRE of the fabric is governed by deposition of the aerosols, consequently increasing the PRE.
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Affiliation(s)
- Anja Pogačnik Krajnc
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia; (A.P.K.); (U.G.C.); (A.G.); (I.B.M.); (M.R.)
| | - Luka Pirker
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia; (A.P.K.); (U.G.C.); (A.G.); (I.B.M.); (M.R.)
| | - Urška Gradišar Centa
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia; (A.P.K.); (U.G.C.); (A.G.); (I.B.M.); (M.R.)
| | - Anton Gradišek
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia; (A.P.K.); (U.G.C.); (A.G.); (I.B.M.); (M.R.)
| | - Igor B. Mekjavic
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia; (A.P.K.); (U.G.C.); (A.G.); (I.B.M.); (M.R.)
| | - Matej Godnič
- Novo Mesto General Hospital, Šmihelska Cesta 1, 8000 Novo Mesto, Slovenia;
| | - Metod Čebašek
- HYLA d.o.o., Brnčičeva Ulica 47, 1231 Ljubljana, Slovenia;
| | | | - Maja Remškar
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia; (A.P.K.); (U.G.C.); (A.G.); (I.B.M.); (M.R.)
- Faculty of Mathematics and Physics, University of Ljubljana, Jadranska Cesta 19, 1000 Ljubljana, Slovenia
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Pirker L, Krajnc AP, Malec J, Radulović V, Gradišek A, Jelen A, Remškar M, Mekjavić IB, Kovač J, Mozetič M, Snoj L. Sterilization of polypropylene membranes of facepiece respirators by ionizing radiation. J Memb Sci 2021; 619:118756. [PMID: 33024349 PMCID: PMC7528844 DOI: 10.1016/j.memsci.2020.118756] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 08/28/2020] [Accepted: 08/31/2020] [Indexed: 11/24/2022]
Abstract
Ionizing radiation has been identified as an option for sterilization of disposable filtering facepiece respirators in situations where the production of the respirators cannot keep up with demand. Gamma radiation and high energy electrons penetrate deeply into the material and can be used to sterilize large batches of masks within a short time period. In relation to reports that sterilization by ionizing radiation reduces filtration efficiency of polypropylene membrane filters on account of static charge loss, we have demonstrated that both gamma and electron beam irradiation can be used for sterilization, provided that the respirators are recharged afterwards.
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Affiliation(s)
- Luka Pirker
- Jožef Stefan Institute, Jamova Cesta 39, 1000, Ljubljana, Slovenia
| | | | - Jan Malec
- Jožef Stefan Institute, Jamova Cesta 39, 1000, Ljubljana, Slovenia
| | | | - Anton Gradišek
- Jožef Stefan Institute, Jamova Cesta 39, 1000, Ljubljana, Slovenia
| | - Andreja Jelen
- Jožef Stefan Institute, Jamova Cesta 39, 1000, Ljubljana, Slovenia
| | - Maja Remškar
- Jožef Stefan Institute, Jamova Cesta 39, 1000, Ljubljana, Slovenia
| | - Igor B Mekjavić
- Jožef Stefan Institute, Jamova Cesta 39, 1000, Ljubljana, Slovenia
| | - Janez Kovač
- Jožef Stefan Institute, Jamova Cesta 39, 1000, Ljubljana, Slovenia
| | - Miran Mozetič
- Jožef Stefan Institute, Jamova Cesta 39, 1000, Ljubljana, Slovenia
| | - Luka Snoj
- Jožef Stefan Institute, Jamova Cesta 39, 1000, Ljubljana, Slovenia
- University of Ljubljana, Faculty of Mathematics and Physics, Jadranska Ulica 19, 1000, Ljubljana, Slovenia
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Pirker L, Višić B, Škapin SD, DraŽić G, Kovač J, Remškar M. Multi-stoichiometric quasi-two-dimensional W nO 3n-1 tungsten oxides. Nanoscale 2020; 12:15102-15114. [PMID: 32644095 DOI: 10.1039/d0nr02014a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Quasi-two-dimensional tungsten oxide structures, which nucleate by epitaxial growth on W19O55 nanowires (NW) and grow as thin platelets, were identified. Both the nanowires and the platelets accommodate oxygen deficiency by the formation of crystallographic shear planes. Stoichiometric phases, W18O53 (WO2.944), W17O50 (WO2.941), W16O47 (WO2.938), W15O44 (WO2.933), W14O41 (WO2.929), W10O29 (WO2.9), and W9O26 (WO2.889), syntactically grow inside a single platelet. These layered crystals show a new kind of polycrystallinity, where crystallographic shear planes accommodate oxygen deficiency and at the same time stabilize this multi-stoichiometric structure.
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Affiliation(s)
- Luka Pirker
- JoŽef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.
| | - Bojana Višić
- JoŽef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia. and Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
| | - Srečo D Škapin
- JoŽef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia. and JoŽef Stefan International Postgraduate School, Jamova cesta 39, 1000 Ljubljana, Slovenia
| | - Goran DraŽić
- JoŽef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia. and JoŽef Stefan International Postgraduate School, Jamova cesta 39, 1000 Ljubljana, Slovenia and National Institute of Chemistry, Hajdrihova 19, 1001 Ljubljana, Slovenia
| | - Janez Kovač
- JoŽef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.
| | - Maja Remškar
- JoŽef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.
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11
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Zheng F, Pozzi G, Migunov V, Pirker L, Remškar M, Beleggia M, Dunin-Borkowski RE. Quantitative measurement of charge accumulation along a quasi-one-dimensional W 5O 14 nanowire during electron field emission. Nanoscale 2020; 12:10559-10564. [PMID: 32162633 DOI: 10.1039/d0nr00739k] [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: 06/10/2023]
Abstract
We use an electron holographic method to determine the charge distribution along a quasi-one-dimensional W5O14 nanowire during in situ field emission in a transmission electron microscope. The results show that the continuous charge distribution along the nanowire is not linear, but that there is an additional accumulation of charge at its apex. An analytical expression for this additional contribution to the charge distribution is proposed and its effect on the field enhancement factor and emission current is discussed.
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Affiliation(s)
- Fengshan Zheng
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany.
| | - Giulio Pozzi
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany. and Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
| | - Vadim Migunov
- Central Facility for Electron Microscopy (GFE), RWTH Aachen University, Ahornstrasse 55, 52074 Aachen, Germany
| | - Luka Pirker
- Jozef Stefan Institute, Solid-State Physics Department, Jamova 39, SLO-1000 Ljubljana, Slovenia
| | - Maja Remškar
- Jozef Stefan Institute, Solid-State Physics Department, Jamova 39, SLO-1000 Ljubljana, Slovenia
| | - Marco Beleggia
- DTU Nanolab, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Rafal E Dunin-Borkowski
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany.
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12
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Pohlen M, Pirker L, Luštrik M, Dreu R. A redispersible dry emulsion system with simvastatin prepared via fluid bed layering as a means of dissolution enhancement of a lipophilic drug. Int J Pharm 2018; 549:325-334. [DOI: 10.1016/j.ijpharm.2018.07.064] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/10/2018] [Accepted: 07/27/2018] [Indexed: 12/16/2022]
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Rodríguez Ripoll M, Tomala A, Gabler C, DraŽić G, Pirker L, Remškar M. In situ tribochemical sulfurization of molybdenum oxide nanotubes. Nanoscale 2018; 10:3281-3290. [PMID: 29384160 DOI: 10.1039/c7nr05830f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [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
MoS2 nanoparticles are typically obtained by high temperature sulfurization of organic and inorganic precursors under a S rich atmosphere and have excellent friction reduction properties. We present a novel approach for making the sulfurization unnecessary for MoO3 nanotubes during the synthesis process for friction and wear reduction applications while simultaneously achieving a superb tribological performance. To this end, we report the first in situ sulfurization of MoO3 nanotubes during sliding contact in the presence of sulfur-containing lubricant additives. The sulfurization leads to the tribo-chemical formation of a MoS2-rich low-friction tribofilm as verified using Raman spectroscopy and can be achieved both during sliding contact and under extreme pressure conditions. Under sliding contact conditions, MoO3 nanotubes in synergy with sulfurized olefin polysulfide and pre-formed zinc dialkyl dithiophosphate tribofilms achieve an excellent friction performance. Under these conditions, the tribochemical sulfurization of MoO3 nanotubes leads to a similar coefficient of friction to the one obtained using a model nanolubricant containing MoS2 nanotubes. Under extreme pressure conditions, the in situ sulfurization of MoO3 nanotubes using sulfurized olefin polysulfide results in a superb load carrying capacity capable of outperforming MoS2 nanotubes. The reason is that while MoO3 nanotubes are able to continuously sulfurize during sliding contact conditions, MoS2 nanotubes progressively degrade by oxidation thus losing lubricity.
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Affiliation(s)
| | - Agnieszka Tomala
- AC2T research GmbH, Wiener Neustadt, Austria. and Institute for Sustainable Technologies, Radom, Poland
| | | | - Goran DraŽić
- National Institute of Chemistry, Ljubljana, Slovenia and Institute JoŽef Stefan, Ljubljana, Slovenia
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Mur J, Pirker L, Osterman N, Petkovšek R. Silicon crystallinity control during laser direct microstructuring with bursts of picosecond pulses. Opt Express 2017; 25:26356-26364. [PMID: 29041292 DOI: 10.1364/oe.25.026356] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 10/11/2017] [Indexed: 06/07/2023]
Abstract
Laser ablation and modification using bursts of picosecond pulses and a tightly focused laser beam are used to manufacture structures in the bulk silicon. We demonstrate precise control of the surface crystallinity as well as the structure depth and topography of the processed areas, achieving homogeneous surface properties. The control is achieved with a combination of a well-defined pulse energy, systematic pulse positioning on the material, and the number of pulses in a burst. A custom designed fiber laser source is used to generate bursts of 1, 5, 10, and 20 pulses at a pulse repetition rate of 40 MHz and burst repetition rate of 83.3 kHz allowing for a fast and stable processing of silicon. We show a controlled transition through different laser-matter interaction regimes, from no observable changes of the silicon at low pulse energies, through amorphization below the ablation threshold energy, to the ablation with either complete, partial or nonexistent amorphization. Single micrometer-sized areas of desired shape and crystallinity were defined on the silicon surface with submicron precision, offering a promising tool for applications in the field of optics.
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