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Abstract
There is currently no reliable method for studying interfacial regions within dielectric nanocomposites. The aim of this work was to develop experimental protocols and signal analysis involving Electrostatic Force Microscopy (EFM). Model samples made of spherical nanoparticles deposited on a metallic substrate and covered by two shells were designed and fabricated to simulate the presence of an interphase between a particle and a matrix. EFM performed either with DC or AC gradients detection method proved good sensitivity to certain sample configurations. A quantification of the dielectric permittivity of the intermediate layer was possible, thanks to correlation with finite element numerical simulations. Interfacial states between stacked layers, which can be attributed to film deposition processes, were also evidenced.
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Affiliation(s)
- J. Castellon
- Université de Montpellier, Institut d’Electronique et Systèmes (IES) Montpellier, France
| | - D. El Khoury
- Université de Montpellier, Institut d’Electronique et Systèmes (IES) Montpellier, France
| | - R. Arinero
- Université de Montpellier, Institut d’Electronique et Systèmes (IES) Montpellier, France
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El Khoury D, Fedorenko V, Castellon J, Bechelany M, Laurentie JC, Balme S, Fréchette M, Ramonda M, Arinero R. Characterization of Dielectric Nanocomposites with Electrostatic Force Microscopy. Scanning 2017; 2017:4198519. [PMID: 29109811 PMCID: PMC5661829 DOI: 10.1155/2017/4198519] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 06/22/2017] [Accepted: 08/03/2017] [Indexed: 05/12/2023]
Abstract
Nanocomposites physical properties unexplainable by general mixture laws are usually supposed to be related to interphases, highly present at the nanoscale. The intrinsic dielectric constant of the interphase and its volume need to be considered in the prediction of the effective permittivity of nanodielectrics, for example. The electrostatic force microscope (EFM) constitutes a promising technique to probe interphases locally. This work reports theoretical finite-elements simulations and experimental measurements to interpret EFM signals in front of nanocomposites with the aim of detecting and characterizing interphases. According to simulations, we designed and synthesized appropriate samples to verify experimentally the ability of EFM to characterize a nanoshell covering nanoparticles, for different shell thicknesses. This type of samples constitutes a simplified electrostatic model of a nanodielectric. Experiments were conducted using either DC or AC-EFM polarization, with force gradient detection method. A comparison between our numerical model and experimental results was performed in order to validate our predictions for general EFM-interphase interactions.
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Affiliation(s)
- D. El Khoury
- Institut d'Electronique et des Systèmes, Université de Montpellier, 34095 Montpellier Cedex 5, France
| | - V. Fedorenko
- Institut Européen des Membranes, IEM UMR-5635, Université de Montpellier, ENSCM, CNRS, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
| | - J. Castellon
- Institut d'Electronique et des Systèmes, Université de Montpellier, 34095 Montpellier Cedex 5, France
| | - M. Bechelany
- Institut Européen des Membranes, IEM UMR-5635, Université de Montpellier, ENSCM, CNRS, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
| | - J.-C. Laurentie
- Institut d'Electronique et des Systèmes, Université de Montpellier, 34095 Montpellier Cedex 5, France
| | - S. Balme
- Institut Européen des Membranes, IEM UMR-5635, Université de Montpellier, ENSCM, CNRS, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
| | - M. Fréchette
- Hydro-Québec's Research Institute, Varennes, QC, Canada J3X 1S1
| | - M. Ramonda
- Centre de Technologie de Montpellier, Université de Montpellier, 34095 Montpellier Cedex 5, France
| | - R. Arinero
- Institut d'Electronique et des Systèmes, Université de Montpellier, 34095 Montpellier Cedex 5, France
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Lertsethtakarn P, Howitt MR, Castellon J, Amieva MR, Ottemann KM. Helicobacter pylori CheZ(HP) and ChePep form a novel chemotaxis-regulatory complex distinct from the core chemotaxis signaling proteins and the flagellar motor. Mol Microbiol 2015; 97:1063-78. [PMID: 26061894 DOI: 10.1111/mmi.13086] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/08/2015] [Indexed: 12/20/2022]
Abstract
Chemotaxis is important for Helicobacter pylori to colonize the stomach. Like other bacteria, H. pylori uses chemoreceptors and conserved chemotaxis proteins to phosphorylate the flagellar rotational response regulator, CheY, and modulate the flagellar rotational direction. Phosphorylated CheY is returned to its non-phosphorylated state by phosphatases such as CheZ. In previously studied cases, chemotaxis phosphatases localize to the cellular poles by interactions with either the CheA chemotaxis kinase or flagellar motor proteins. We report here that the H. pylori CheZ, CheZ(HP), localizes to the poles independently of the flagellar motor, CheA, and all typical chemotaxis proteins. Instead, CheZ(HP) localization depends on the chemotaxis regulatory protein ChePep, and reciprocally, ChePep requires CheZ(HP) for its polar localization. We furthermore show that these proteins interact directly. Functional domain mapping of CheZ(HP) determined the polar localization motif lies within the central domain of the protein and that the protein has regions outside of the active site that participate in chemotaxis. Our results suggest that CheZ(HP) and ChePep form a distinct complex. These results therefore suggest the intriguing idea that some phosphatases localize independently of the other chemotaxis and motility proteins, possibly to confer unique regulation on these proteins' activities.
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Affiliation(s)
- Paphavee Lertsethtakarn
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, CA, 95064, USA
| | - Michael R Howitt
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Juan Castellon
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, CA, 95064, USA
| | - Manuel R Amieva
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Karen M Ottemann
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, CA, 95064, USA
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Toureille A, Notingher P, Vella N, Malrieu S, Castellon J, Agnel S. The thermal step technique: an advanced method for studying the properties and testing the quality of polymers. POLYM INT 1998. [DOI: 10.1002/(sici)1097-0126(199806)46:2<81::aid-pi994>3.0.co;2-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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