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Neville F, Moreno-Atanasio R. Influence of Shell Thickness on the Colloidal Stability of Magnetic Core-Shell Particle Suspensions. Front Chem 2018; 6:201. [PMID: 29922646 PMCID: PMC5996203 DOI: 10.3389/fchem.2018.00201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 05/15/2018] [Indexed: 01/01/2023] Open
Abstract
We present a Discrete Element study of the behavior of magnetic core-shell particles in which the properties of the core and the shell are explicitly defined. Particle cores were considered to be made of pure iron and thus possessed ferromagnetic properties, while particle shells were considered to be made of silica. Core sizes ranged between 0.5 and 4.0 μm with the actual particle size of the core-shell particles in the range between 0.6 and 21 μm. The magnetic cores were considered to have a magnetization of one tenth of the saturation magnetization of iron. This study aimed to understand how the thickness of the shell hinders the formation of particle chains. Chain formation was studied with different shell thicknesses and particle sizes in the presence and absence of an electrical double layer force in order to investigate the effect of surface charge density on the magnetic core-shell particle interactions. For core sizes of 0.5 and 4.0 μm the relative shell thicknesses needed to hinder the aggregation process were approximately 0.4 and 0.6 respectively, indicating that larger core sizes are detrimental to be used in applications in which no flocculation is needed. In addition, the presence of an electrical double layer, for values of surface charge density of less than 20 mC/m2, could stop the contact between particles without hindering their vertical alignment. Only when the shell thickness was considerably larger, was the electrical double layer able to contribute to the full disruption of the magnetic flocculation process.
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Affiliation(s)
- Frances Neville
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW, Australia
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Copie G, Biaye M, Diesinger H, Melin T, Krzeminski C, Cleri F. Deformation Localization in Molecular Layers Constrained between Self-Assembled Au Nanoparticles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:2677-2687. [PMID: 28221811 DOI: 10.1021/acs.langmuir.7b00237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The localized deformation of molecular monolayers constrained between the spherical surfaces of Au nanoparticles is studied by means of molecular dynamics simulations. Alkyl or polyethylene glycol long-chain molecules were homogeneously distributed over the curved Au surface, pushed against each other by repeated cycles of force relaxation and constant-volume equilibration at temperatures increasing from 50 to 300 K before being slowly quenched to near-zero temperature. Plots of minimum configurational energy can be obtained as a function of the nanoparticle distance, according to different directions of approach; therefore, such simulations describe a range of deformations, from perfectly uniaxial compression to a combination of compression and shear. Despite the relative rigidity of molecular backbones, the deformation is always found to be localized at the interface between the opposing molecular monolayers. We find that shorter ligands can be more densely packed on the surface but do no interdigitate upon compression; they respond to the applied force by bending and twisting, thus changing their conformation while remaining disjointed. On the contrary, longer ligands attain lower surface densities and can interprenetrate when the nanoparticles are compressed against each other; such molecules remain rather straight and benefit from the increased overlap to maximize the adhesion by dispersion forces. The apparent Young's and shear moduli of a dense nanostructure, composed of a triangular arrangement of identical MUDA-decorated Au nanoparticles, are found to be smaller than estimates indirectly deduced by atomic-force experiments but quite close to previous computer simulations of molecular monolayers on flat surfaces and of bulk nanoparticle assemblies.
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Affiliation(s)
- G Copie
- Institut d'Electronique, Microélectronique et Nanotechnologie (IEMN), CNRS UMR 8520, Université de Lille 1 Sciences et Technologies , Avenue Poincaré, 59652 Villeneuve d'Ascq, France
| | - M Biaye
- Institut d'Electronique, Microélectronique et Nanotechnologie (IEMN), CNRS UMR 8520, Université de Lille 1 Sciences et Technologies , Avenue Poincaré, 59652 Villeneuve d'Ascq, France
| | - H Diesinger
- Institut d'Electronique, Microélectronique et Nanotechnologie (IEMN), CNRS UMR 8520, Université de Lille 1 Sciences et Technologies , Avenue Poincaré, 59652 Villeneuve d'Ascq, France
| | - T Melin
- Institut d'Electronique, Microélectronique et Nanotechnologie (IEMN), CNRS UMR 8520, Université de Lille 1 Sciences et Technologies , Avenue Poincaré, 59652 Villeneuve d'Ascq, France
| | - C Krzeminski
- Institut d'Electronique, Microélectronique et Nanotechnologie (IEMN), CNRS UMR 8520, Université de Lille 1 Sciences et Technologies , Avenue Poincaré, 59652 Villeneuve d'Ascq, France
| | - F Cleri
- Institut d'Electronique, Microélectronique et Nanotechnologie (IEMN), CNRS UMR 8520, Université de Lille 1 Sciences et Technologies , Avenue Poincaré, 59652 Villeneuve d'Ascq, France
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Leite FL, Bueno CC, Da Róz AL, Ziemath EC, Oliveira ON. Theoretical models for surface forces and adhesion and their measurement using atomic force microscopy. Int J Mol Sci 2012. [PMID: 23202925 PMCID: PMC3497299 DOI: 10.3390/ijms131012773] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The increasing importance of studies on soft matter and their impact on new technologies, including those associated with nanotechnology, has brought intermolecular and surface forces to the forefront of physics and materials science, for these are the prevailing forces in micro and nanosystems. With experimental methods such as the atomic force spectroscopy (AFS), it is now possible to measure these forces accurately, in addition to providing information on local material properties such as elasticity, hardness and adhesion. This review provides the theoretical and experimental background of afs, adhesion forces, intermolecular interactions and surface forces in air, vacuum and in solution.
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Affiliation(s)
- Fabio L. Leite
- Nanoneurobiophysics Research Group, Department of Physics, Chemistry and Mathematics, Federal University of São Carlos (UFSCar), P.O. Box 3031, CEP 18052-780, Sorocaba, São Paulo, Brazil; E-Mails: (C.C.B.); (A.L.D.R.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +55-015-3229-6014; Fax: +55-015-3229-5902
| | - Carolina C. Bueno
- Nanoneurobiophysics Research Group, Department of Physics, Chemistry and Mathematics, Federal University of São Carlos (UFSCar), P.O. Box 3031, CEP 18052-780, Sorocaba, São Paulo, Brazil; E-Mails: (C.C.B.); (A.L.D.R.)
| | - Alessandra L. Da Róz
- Nanoneurobiophysics Research Group, Department of Physics, Chemistry and Mathematics, Federal University of São Carlos (UFSCar), P.O. Box 3031, CEP 18052-780, Sorocaba, São Paulo, Brazil; E-Mails: (C.C.B.); (A.L.D.R.)
| | - Ervino C. Ziemath
- Institute of Geosciences and Exact Sciences, São Paulo State University (UNESP), P.O. Box 178, CEP 13550-970, Rio Claro, São Paulo, Brazil; E-Mail:
| | - Osvaldo N. Oliveira
- Institute of Physics of São Carlos, University of São Paulo (USP), P.O. Box 369, CEP 13560-970, São Carlos, São Paulo, Brazil; E-Mail:
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Conti DS, Grashik J, Yang L, Wu L, da Rocha SRP. Solvation in hydrofluoroalkanes: how can ethanol help? J Pharm Pharmacol 2011; 64:1236-44. [DOI: 10.1111/j.2042-7158.2011.01398.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Abstract
Objectives
The goal of this work was to evaluate the ability of ethanol mixed with hydrofluoroalkanes (HFAs) to improve solvation of moieties of relevance to pressurized metered-dose inhalers (pMDIs).
Methods
Chemical force microscopy was used to measure the adhesion force (Fad) between alkyl-based, ether-based and ester-based moieties (C8/C8, COC/COC and COOC/COOC interactions) in 2H,3H-perfluoropentane (HPFP)/ethanol mixtures. HPFP is a liquid that mimics propellant HFAs. The Fad results are thus a measure of solvation in HFAs. Johnson–Kendall–Roberts (JKR) theory was used to model the results.
Key findings
The Fad normalized by the tip radius of curvature (Fad/R) decreased upon the addition of ethanol, suggesting its ability to enhance the solvent environment. At 15% (v/v) ethanol, the Fad/R was reduced 34% for the alkyl, 63% for the ether, and down 67% for the ester tails. Thus, the solvation could be ranked as: ester > ether > alkyl. JKR theory was a reasonable model for the Fad/R.
Conclusions
Ethanol, within the concentration range of interest in commercial pMDIs, provided limited enhancement in solvation of alkyl moieties. On the other hand, the cosolvent significantly enhanced solvation of ether-based and ester-based moieties, thus suggesting its potential for formulations containing amphiphiles with such groups.
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Affiliation(s)
- Denise S Conti
- Department of Chemical Engineering and Materials Science, College of Engineering, Wayne State University, Detroit, MI, USA
| | - Jordan Grashik
- Department of Chemical Engineering and Materials Science, College of Engineering, Wayne State University, Detroit, MI, USA
| | - Lin Yang
- Department of Chemical Engineering and Materials Science, College of Engineering, Wayne State University, Detroit, MI, USA
| | - Libo Wu
- Department of Chemical Engineering and Materials Science, College of Engineering, Wayne State University, Detroit, MI, USA
| | - Sandro R P da Rocha
- Department of Chemical Engineering and Materials Science, College of Engineering, Wayne State University, Detroit, MI, USA
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Lim KP, Tan LP. Interaction force measurements for the design of tissue adhesives. Acta Biomater 2009; 5:84-92. [PMID: 18793880 DOI: 10.1016/j.actbio.2008.08.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 08/05/2008] [Accepted: 08/07/2008] [Indexed: 11/15/2022]
Abstract
Synthesis of tissue adhesives had been carried out in various laboratories in the past decades but the development is currently stalled. One of the key reasons, it is believed, is that researchers have not fully understood and resolved the role of the functional groups that are responsible for good adhesion to biological tissues. Further progress in synthesis is significantly hindered without this fundamental understanding. With this aim in mind, atomic force microscopy (AFM) has been exploited in this work to study the interactions between functional groups that are common to biological tissues. In this work, the AFM tip and substrates were functionalized and used to measure the non-specific interaction among these common functional groups. The ultimate aim of the study is to calculate the interaction force between a single pair of functional groups. A novel calculation method based on the AFM data and probe geometry is presented. The results provide insights into the strength of the bond between different functional groups and the could serve as a guide in selecting the appropriate functional groups in tissue adhesive synthesis. This method could be further applied to studies involving interfaces of biomedical devices where intermolecular interactions are of concern.
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Affiliation(s)
- K P Lim
- School of Materials Science and Engineering, Nanyang Technological University, Blk N4.1, Nanyang Avenue, Singapore 639798, Singapore
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Miao F, Ohlberg D, Stewart DR, Williams RS, Lau CN. Quantum conductance oscillations in metal/molecule/metal switches at room temperature. PHYSICAL REVIEW LETTERS 2008; 101:016802. [PMID: 18764137 DOI: 10.1103/physrevlett.101.016802] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Indexed: 05/26/2023]
Abstract
We apply pressure-modulated conductance microscopy to metal/molecule/metal switches. Apart from pressure-induced conductance peaks that indicate nanoscale conducting pathways, we also observe dips and oscillations for devices with conductance between 1 and 2 conductance quantum. The conductance oscillations arise from interfering electron waves along one or two quantum conductance channels between two partially transmitting electrode surfaces at room temperature, underscoring these devices' potential as coherent, atomic-scale switches.
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Affiliation(s)
- Feng Miao
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
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Greene ME, Kinser CR, Kramer DE, Pingree LSC, Hersam MC. Application of scanning probe microscopy to the characterization and fabrication of hybrid nanomaterials. Microsc Res Tech 2004; 64:415-34. [PMID: 15549695 DOI: 10.1002/jemt.20100] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Scanning probe microscopy (SPM) is a widely used experimental technique for characterizing and fabricating nanostructures on surfaces. In particular, due to its ability to spatially map variations in materials properties with nanometer spatial resolution, SPM is particularly well suited to probe the subcomponents and interfaces of hybrid nanomaterials, i.e., materials that are made up of distinct nanometer scale components with distinguishable properties. In addition, the interaction of the SPM tip with materials can be intentionally tuned such that local surface modification is achieved. In this manner, hybrid nanostructures can also be fabricated on solid substrates using SPM. This report reviews recent developments in the characterization and fabrication of hybrid nanomaterials with SPM. Specific attention is given to nanomaterials that consist of both organic and inorganic components including individual biomolecules mounted on inorganic substrates. SPM techniques that are particularly well suited for characterizing the mechanical and electrical properties of such hybrid systems in atmospheric pressure environments are highlighted, and specific illustrative examples are provided. This review concludes with a brief discussion of the remaining challenges and promising future prospects for this field.
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Affiliation(s)
- Mark E Greene
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, USA
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