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Patra A, Caligiuri V, Zappone B, Krahne R, De Luca A. In-Plane and Out-of-Plane Investigation of Resonant Tunneling Polaritons in Metal-Dielectric-Metal Cavities. Nano Lett 2023; 23:1489-1495. [PMID: 36745481 PMCID: PMC9951238 DOI: 10.1021/acs.nanolett.2c04864] [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] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/20/2023] [Indexed: 06/18/2023]
Abstract
Polaritons can be generated by tuning the optical transitions of a light emitter to the resonances of a photonic cavity. We show that a dye-doped cavity generates resonant tunneling polaritons with Epsilon-Near-Zero (ENZ) effective permittivity. We studied the polariton spectral dispersion in dye-doped metal-dielectric-metal (MDM) cavities as a function of the in-plane (k||) and out-of-plane (k⊥) components of the incident wavevector. The dependence on k|| was investigated through ellipsometry, revealing the ENZ modes. The k⊥ dependence was measured by varying the cavity thickness under normal incidence using a Surface Force Apparatus (SFA). Both methods revealed a large Rabi splitting well exceeding 100 meV. The SFA-based investigation highlighted the collective nature of strong coupling by producing a splitting proportional to the square root of the involved photons. This study demonstrates the possibility of generating ENZ polaritons and introduces the SFA as a powerful tool for the characterization of strong light-matter interactions.
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Affiliation(s)
- Aniket Patra
- Dipartimento
di Fisica, Università della Calabria, via P. Bucci 33b, 87036 Rende CS, Italy
- Optoelectronics
Research Line, Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy
| | - Vincenzo Caligiuri
- Dipartimento
di Fisica, Università della Calabria, via P. Bucci 33b, 87036 Rende CS, Italy
- Consiglio
Nazionale delle Ricerche−Istituto di Nanotecnologia (CNR-Nanotec), via P. Bucci 33c, 87036 Rende, Italy
| | - Bruno Zappone
- Consiglio
Nazionale delle Ricerche−Istituto di Nanotecnologia (CNR-Nanotec), via P. Bucci 33c, 87036 Rende, Italy
| | - Roman Krahne
- Optoelectronics
Research Line, Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy
| | - Antonio De Luca
- Dipartimento
di Fisica, Università della Calabria, via P. Bucci 33b, 87036 Rende CS, Italy
- Consiglio
Nazionale delle Ricerche−Istituto di Nanotecnologia (CNR-Nanotec), via P. Bucci 33c, 87036 Rende, Italy
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Zappone B, Caligiuri V, Patra A, Krahne R, De Luca A. Understanding and Controlling Mode Hybridization in Multicavity Optical Resonators Using Quantum Theory and the Surface Forces Apparatus. ACS Photonics 2021; 8:3517-3525. [PMID: 36090192 PMCID: PMC9446313 DOI: 10.1021/acsphotonics.1c01055] [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] [Indexed: 06/15/2023]
Abstract
Optical fields in metal-dielectric multilayers display typical features of quantum systems, such as energy level quantization and avoided crossing, underpinned by an isomorphism between the Helmholtz and Schrödinger wave equations. This article builds on the fundamental concepts and methods of quantum theory to facilitate the understanding and design of multicavity resonators. It also introduces the surface forces apparatus (SFA) as a powerful tool for rapid, continuous, and extensive characterization of mode dispersion and hybridization. Instead of fabricating many different resonators, two equal metal-dielectric-metal microcavities were created on glass lenses and displaced relative to each other in a transparent silicone oil using the SFA. The fluid thickness was controlled in real time with nanometer accuracy from more than 50 μm to less than 20 nm, reaching mechanical contact between the outer cavities in a few minutes. The fluid gap acted as a third microcavity providing optical coupling and producing a complex pattern of resonance splitting as a function of the variable thickness. An optical wave in this symmetric three-cavity resonator emulated a quantum particle with nonzero mass in a potential comprising three square wells. Interference between the wells produced a 3-fold splitting of degenerate energy levels due to hybridization. The experimental results could be explained using the standard methods and formalism of quantum mechanics, including symmetry operators and the variational method. Notably, the interaction between square wells produced bonding, antibonding, and nonbonding states that are analogous to hybridized molecular orbitals and are relevant to the design of "epsilon-near-zero" devices with vanishing dielectric permittivity.
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Affiliation(s)
- Bruno Zappone
- Consiglio
Nazionale delle Ricerche − Istituto di Nanotecnologia (CNR-Nanotec), via P. Bucci 33/C, 87036 Rende, CS, Italy
| | - Vincenzo Caligiuri
- Consiglio
Nazionale delle Ricerche − Istituto di Nanotecnologia (CNR-Nanotec), via P. Bucci 33/C, 87036 Rende, CS, Italy
- Università
della Calabria − Dipartimento di Fisica, via P. Bucci 31/C, 87036 Rende, CS, Italy
| | - Aniket Patra
- Università
della Calabria − Dipartimento di Fisica, via P. Bucci 31/C, 87036 Rende, CS, Italy
- Istituto
Italiano di Tecnologia (IIT) − Optoelectronics Research Line, via Morego 30, 16163 Genova, Italy
| | - Roman Krahne
- Istituto
Italiano di Tecnologia (IIT) − Optoelectronics Research Line, via Morego 30, 16163 Genova, Italy
| | - Antonio De Luca
- Consiglio
Nazionale delle Ricerche − Istituto di Nanotecnologia (CNR-Nanotec), via P. Bucci 33/C, 87036 Rende, CS, Italy
- Università
della Calabria − Dipartimento di Fisica, via P. Bucci 31/C, 87036 Rende, CS, Italy
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Affiliation(s)
- Guido Raos
- Department of Chemistry, Materials and Chemical Engineering “G. Natta”, Politecnico di Milano, Via L. Mancinelli 7, I-20131 Milano, Italy
| | - Bruno Zappone
- Consiglio Nazionale delle Ricerche - Istituto di Nanotecnologia (CNR-Nanotec), Via P. Bucci, 33/C, 87036 Rende (CS), Italy
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Zappone B, Bartolino R. Topological barriers to defect nucleation generate large mechanical forces in an ordered fluid. Proc Natl Acad Sci U S A 2021; 118:e2110503118. [PMID: 34706938 PMCID: PMC8612233 DOI: 10.1073/pnas.2110503118] [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] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2021] [Indexed: 11/18/2022] Open
Abstract
Common fluids cannot sustain static mechanical stresses at the macroscopic scale because they lack molecular order. Conversely, crystalline solids exhibit long-range order and mechanical strength at the macroscopic scale. Combining the properties of fluids and solids, liquid crystal films respond to mechanical confinement by both flowing and generating static forces. The elastic response, however, is very weak for film thicknesses exceeding 10 nm. In this study, the mechanical strength of a fluid film was enhanced by introducing topological defects in a cholesteric liquid crystal, producing unique viscoelastic and optomechanical properties. The cholesteric was confined under strong planar anchoring conditions between two curved surfaces with sphere-sphere contact geometry similar to that of large colloidal particles, creating concentric dislocation loops. During surface retraction, the loops shrank and periodically disappeared at the surface contact point, where the cholesteric helix underwent discontinuous twist transitions, producing weak oscillatory surface forces. On the other hand, new loop nucleation was frustrated by a topological barrier during fluid compression, creating a metastable state. This generated exceptionally large forces with a range exceeding 100 nm as well as extended blueshifts of the photonic bandgap. The metastable cholesteric helix eventually collapsed under a high compressive load, triggering a stick-slip-like cascade of defect nucleation and twist reconstruction events. These findings were explained using a simple theoretical model and suggest a general approach to enhance the mechanical strength of one-dimensional periodic materials, particularly cholesteric colloid mixtures.
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Affiliation(s)
- Bruno Zappone
- Consiglio Nazionale delle Ricerche-Istituto di Nanotecnologia (CNR-Nanotec), 87036 Rende, Italy
| | - Roberto Bartolino
- Consiglio Nazionale delle Ricerche-Istituto di Nanotecnologia (CNR-Nanotec), 87036 Rende, Italy
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Bilotto P, Labate C, De Santo MP, Deepankumar K, Miserez A, Zappone B. Adhesive Properties of Adsorbed Layers of Two Recombinant Mussel Foot Proteins with Different Levels of DOPA and Tyrosine. Langmuir 2019; 35:15481-15490. [PMID: 31465231 DOI: 10.1021/acs.langmuir.9b01730] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Using a surface forces apparatus and an atomic force microscope, we characterized the adhesive properties of adsorbed layers of two recombinant variants of Perna viridis foot protein 5 (PVFP-5), the main surface-binding protein in the adhesive plaque of the Asian green mussel. In one variant, all tyrosine residues were modified into 3,4-dihydroxy-l-phenylalanine (DOPA) during expression using a residue-specific incorporation strategy. DOPA is a key molecular moiety underlying underwater mussel adhesion. In the other variant, all tyrosine residues were preserved. The layer was adsorbed on a mica substrate and pressed against an uncoated surface. While DOPA produced a stronger adhesion than tyrosine in contact with the nanoscopic Si3N4 probe of the atomic force microscope, the two variants produced comparable adhesion on the curved macroscopic mica surfaces of the surface forces apparatus. These findings show that the presence of DOPA is not a sufficient condition to generate strong underwater adhesion. Surface chemistry and contact geometry affect the strength and abundance of protein-surface bonds created during adsorption and surface contact. Importantly, the adsorbed protein layer has a random and dynamic polymer-network structure that should be optimized to transmit the tensile stress generated during surface separation to DOPA surface bonds rather than other weaker bonds.
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Affiliation(s)
- Pierluigi Bilotto
- Dipartimento di Fisica , Università della Calabria , Rende , Italy
- Institute of Applied Physics , Vienna University of Technology , Vienna , Austria
| | - Cristina Labate
- Dipartimento di Fisica , Università della Calabria , Rende , Italy
| | - Maria P De Santo
- Dipartimento di Fisica , Università della Calabria , Rende , Italy
- Consiglio Nazionale delle Ricerche - Istituto di Nanotecnologia (CNR - Nanotec) , c/o Università della Calabria , Ponte P. Bucci, 33/B , 87036 Rende ( CS ), Italy
| | - Kanagavel Deepankumar
- Biological and Biomimetic Material Laboratory and Center for Biomimetic Sensor Science, School of Materials Science and Engineering , Nanyang Technological University (NTU) , 50 Nanyang Avenue , Singapore 637553
| | - Ali Miserez
- Biological and Biomimetic Material Laboratory and Center for Biomimetic Sensor Science, School of Materials Science and Engineering , Nanyang Technological University (NTU) , 50 Nanyang Avenue , Singapore 637553
- School of Biological Sciences , Nanyang Technological University (NTU) , 60 Nanyang Drive , Singapore 637551
| | - Bruno Zappone
- Consiglio Nazionale delle Ricerche - Istituto di Nanotecnologia (CNR - Nanotec) , c/o Università della Calabria , Ponte P. Bucci, 33/B , 87036 Rende ( CS ), Italy
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Zheng W, Perez-Martinez CS, Petriashvili G, Perkin S, Zappone B. Direct measurements of structural forces and twist transitions in cholesteric liquid crystal films with a surface force apparatus. Soft Matter 2019; 15:4905-4914. [PMID: 31166360 DOI: 10.1039/c9sm00487d] [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] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Using a surface force apparatus, a cholesteric liquid crystal was confined between two crossed cylindrical surfaces that induced strong planar anchoring and normal alignment of the chiral helix. The film thickness and total twist angle of the chiral molecular structure were simultaneously measured using multiple-beam optical interference. As the film thickness was increased and the chiral structure deformed, the twist angle remained almost unchanged until discontinuous changes occurred at critical distances that were equally spaced by one cholesteric half-pitch length. Structural deformations generated oscillatory elastic forces with periodically spaced maxima corresponding to twist transitions. These findings were reproduced using an equilibrium model of cholesteric confinement and force generation. The analysis indicates that the strength of the azimuthal surface anchoring on mica is high, exceeding 0.2 mJ m-2.
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Affiliation(s)
- Weichao Zheng
- Università della Calabria, Dipartimento di Fisica, Rende (CS), Italy
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Zappone B, Zheng W, Perkin S. Multiple-beam optical interferometry of anisotropic soft materials nanoconfined with the surface force apparatus. Rev Sci Instrum 2018; 89:085112. [PMID: 30184649 DOI: 10.1063/1.5038951] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 07/21/2018] [Indexed: 06/08/2023]
Abstract
Soft anisotropic materials that change their macroscopic properties in response to external stimuli such as light, electric field, or pressure are central to several new directions of technology, including optics, micro-mechanics, and bioengineering. Responsiveness is fundamentally connected to the anisotropic ordering of the material's building blocks at the nanometer scale. Here we propose the surface force apparatus as a powerful tool for investigating optically anisotropic materials at the nanometer scale using multiple-beam optical interference, allowing for simultaneous determination of film thickness, alignment, and chiral rotation of the optical axis. We present a method based on 4 × 4 matrices for calculating the exact transmission and reflection coefficients for light incident normal to a planar optical multilayer comprising an arbitrary number of chiral anisotropic layers with the helical axis normal to the layer. The multilayer can also include uniform birefringent media, optical adsorbing (e.g., metals) and isotropic materials. We introduce a technique to analyze and interpret the complex multiple-beam interference patterns arising from such multilayers and demonstrate it for the case of a twisted nematic liquid crystal confined to nanoscale thickness with the surface force apparatus. The analysis opens the prospect of studying the effect of strong confinement on the structure and response of a wide class of anisotropic materials.
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Affiliation(s)
- Bruno Zappone
- Consiglio Nazionale delle Ricerche, Istituto di Nanotecnologia (CNR-Nanotec), Rende, CS 87036, Italy
| | - Weichao Zheng
- Università della Calabria, Dipartimento di Fisica, Rende, CS 87036, Italy
| | - Susan Perkin
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, United Kingdom
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Zappone B, Patil NJ, Lombardo M, Lombardo G. Transient viscous response of the human cornea probed with the Surface Force Apparatus. PLoS One 2018; 13:e0197779. [PMID: 29799859 PMCID: PMC5969749 DOI: 10.1371/journal.pone.0197779] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 05/08/2018] [Indexed: 01/07/2023] Open
Abstract
Knowledge of the biomechanical properties of the human cornea is crucial for understanding the development of corneal diseases and impact of surgical treatments (e.g., corneal laser surgery, corneal cross-linking). Using a Surface Force Apparatus we investigated the transient viscous response of the anterior cornea from donor human eyes compressed between macroscopic crossed cylinders. Corneal biomechanics was analyzed using linear viscoelastic theory and interpreted in the framework of a biphasic model of soft hydrated porous tissues, including a significant contribution from the pressurization and viscous flow of fluid within the corneal tissue. Time-resolved measurements of tissue deformation and careful determination of the relaxation time provided an elastic modulus in the range between 0.17 and 1.43 MPa, and fluid permeability of the order of 10−13 m4/(N∙s). The permeability decreased as the deformation was increased above a strain level of about 10%, indicating that the interstitial space between fibrils of the corneal stromal matrix was reduced under the effect of strong compression. This effect may play a major role in determining the observed rate-dependent non-linear stress-strain response of the anterior cornea, which underlies the shape and optical properties of the tissue.
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Affiliation(s)
- Bruno Zappone
- Consiglio Nazionale delle Ricerche, Istituto di Nanotecnologia (CNR-Nanotec), Rende (CS), Italy
- * E-mail: (BZ); (GL)
| | | | | | - Giuseppe Lombardo
- Consiglio Nazionale delle Ricerche, Istituto per i Processi Chimico-Fisici (CNR-IPCF), Messina, Italy
- * E-mail: (BZ); (GL)
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10
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Yunda JP, Zappone B, Alj D, De Luca A, Infusino M. Optical vortices generated by edge dislocations in electro-convective instability arrays of nematic liquid crystals. Opt Lett 2018; 43:1947-1949. [PMID: 29714768 DOI: 10.1364/ol.43.001947] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 03/22/2018] [Indexed: 06/08/2023]
Abstract
We demonstrated by means of interferometry that optical vortices can be generated by diffraction of a laser beam from a birefringent nematic liquid crystal that spontaneously creates a periodic array of electro-convective domains and edge dislocations under an applied electric field. The diffracted beam of order m produced by an elementary dislocation comprises a number |m| of distinct optical vortices, each with unit topological charge. Birefringent liquid crystal arrays provide a fast, convenient, and promising way of generating and studying optical vortices. The used materials are inexpensive, fabrication processes are simple, and both input polarization and applied field can be used as external controls to switch the optical vortices on and off.
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Nemitz IR, Gryn I, Boudet N, Lemieux RP, Goldmann M, Zappone B, Petschek RG, Rosenblatt C, Lacaze E. Observations of a streak texture in the hybrid-aligned smectic-C phase. Soft Matter 2018; 14:460-469. [PMID: 29214250 DOI: 10.1039/c7sm02129a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [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
A novel structure was observed below the smectic-A-smectic-C phase transition in a very thin open cell having an air interface above and enforced planar anchoring at the substrate below. The structure appears as periodic dark and light streaks running perpendicular to the oily streaks, which are present in the smectic-A phase [D. Coursault et al., Soft Matter, 2016, 12, 678]. These new streaks, which we call "soapy streaks", form by extending from one oily streak to the next in discrete steps, eliminating optical evidence at visible wavelengths of the oily streaks. At lower temperatures the streaks can undulate and exhibit a sawtooth-like structure; such a structure is chiral in two dimensions. A possible scenario for the origin of these streaks is presented.
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Affiliation(s)
- I R Nemitz
- Dept. of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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12
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van Engers CD, Cousens NEA, Babenko V, Britton J, Zappone B, Grobert N, Perkin S. Direct Measurement of the Surface Energy of Graphene. Nano Lett 2017; 17:3815-3821. [PMID: 28481551 DOI: 10.1021/acs.nanolett.7b01181] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Graphene produced by chemical vapor deposition (CVD) is a promising candidate for implementing graphene in a range of technologies. In most device configurations, one side of the graphene is supported by a solid substrate, wheras the other side is in contact with a medium of interest, such as a liquid or other two-dimensional material within a van der Waals stack. In such devices, graphene interacts on both faces via noncovalent interactions and therefore surface energies are key parameters for device fabrication and operation. In this work, we directly measured adhesive forces and surface energies of CVD-grown graphene in dry nitrogen, water, and sodium cholate using a modified surface force balance. For this, we fabricated large (∼1 cm2) and clean graphene-coated surfaces with smooth topography at both macro- and nanoscales. By bringing two such surfaces into contact and measuring the force required to separate them, we measured the surface energy of single-layer graphene in dry nitrogen to be 115 ± 4 mJ/m2, which was similar to that of few-layer graphene (119 ± 3 mJ/m2). In water and sodium cholate, we measured interfacial energies of 83 ± 7 and 29 ± 6 mJ/m2, respectively. Our work provides the first direct measurement of graphene surface energy and is expected to have an impact both on the development of graphene-based devices and contribute to the fundamental understanding of surface interactions.
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Affiliation(s)
- Christian D van Engers
- Department of Chemistry, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom
- Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom
| | - Nico E A Cousens
- Department of Chemistry, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Vitaliy Babenko
- Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom
- Centre for Advanced Photonics and Electronics, Cambridge University , 9 JJ Thomson Avenue, Cambridge, CB3 0FA, United Kingdom
| | - Jude Britton
- Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom
| | - Bruno Zappone
- Consiglio Nazionale delle Ricerche, Istituto di Nanotecnologia (CNR-Nanotec), c/o Department of Physics, Università della Calabria , Rende (CS) 87036, Italy
| | - Nicole Grobert
- Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom
| | - Susan Perkin
- Department of Chemistry, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom
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Patil NJ, Rishikesan S, Nikogeorgos N, Guzzi R, Lee S, Zappone B. Complexation and synergistic boundary lubrication of porcine gastric mucin and branched poly(ethyleneimine) in neutral aqueous solution. Soft Matter 2017; 13:590-599. [PMID: 27976775 DOI: 10.1039/c6sm01801g] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Lubrication of soft polydimethylsiloxane (PDMS) elastomer interfaces was studied in aqueous mixtures of porcine gastric mucin (PGM) and branched polyethyleneimine (b-PEI) at neutral pH and various ionic strengths (0.1-1.0 M). While neither PGM nor b-PEI improved lubrication compared to polymer-free buffer solution, their mixtures produced a synergistic lubricating effect by reducing friction coefficients by nearly two orders of magnitude, especially at slow sliding speed in the boundary lubrication regime. An array of spectroscopic studies revealed that small cationic b-PEI molecules were able to strongly bind and penetrate into large anionic PGM molecules, producing an overall contraction of the randomly coiled PGM conformation. The interaction also affected the structure of the folded PGM protein terminals, decreased the surface potential and increased light absorbance in PGM:b-PEI mixtures. Adding an electrolyte (NaCl) weakened the aggregation between PGM and b-PEI, and degraded the lubrication synergy, indicating that electrostatic interactions drive PGM:b-PEI complexation.
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Affiliation(s)
- Navinkumar J Patil
- Dipartimento di Fisica, Università della Calabria, Cubo 31/C, Rende, CS 87036, Italy
| | | | - Nikolaos Nikogeorgos
- Department of Mechanical Engineering, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark.
| | - Rita Guzzi
- Dipartimento di Fisica, Università della Calabria, Cubo 31/C, Rende, CS 87036, Italy
| | - Seunghwan Lee
- Department of Mechanical Engineering, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark.
| | - Bruno Zappone
- Consiglio Nazionale delle Ricerche - Istituto di Nanotecnologia (CNR-Nanotec), SS Cosenza - LICRYL, c/o Dipartimento di Fisica, Università della Calabria, Cubo 33/B, Rende, CS 87036, Italy.
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Nikogeorgos N, Patil NJ, Zappone B, Lee S. Interaction of porcine gastric mucin with various polycations and its influence on the boundary lubrication properties. POLYMER 2016. [DOI: 10.1016/j.polymer.2016.08.030] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Coursault D, Zappone B, Coati A, Boulaoued A, Pelliser L, Limagne D, Boudet N, Ibrahim BH, de Martino A, Alba M, Goldmann M, Garreau Y, Gallas B, Lacaze E. Self-organized arrays of dislocations in thin smectic liquid crystal films. Soft Matter 2016; 12:678-688. [PMID: 26565648 DOI: 10.1039/c5sm02241j] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Combining optical microscopy, synchrotron X-ray diffraction and ellipsometry, we studied the internal structure of linear defect domains (oily streaks) in films of a smectic liquid crystal 8CB with thicknesses in the range of 100-300 nm. These films are confined between air and a rubbed PVA polymer substrate which imposes hybrid anchoring conditions (normal and unidirectional planar, respectively). We show how the presence or absence of dislocations controls the structure of highly deformed thin smectic films. Each domain contains smectic layers curved in the shape of flattened hemicylinders to satisfy both anchoring conditions, together with grain boundaries whose size and shape are controlled by the presence of dislocation lines. A flat grain boundary normal to the interface connects neighboring hemicylinders, while a rotating grain boundary (RGB) is located near the axis of curvature of the cylinders. The RGB shape appears such that dislocation lines are concentrated at its summit close to the air interface. The smectic layers reach the polymer substrate via a transition region where the smectic layer orientation satisfies the planar anchoring conditions over the entire polymer substrate and whose thickness does not depend on that of the film. The strength of planar anchoring appears to be high, larger than 10(-2) mJ m(-2), compensating for the high energy cost of creating an additional 2D defect between a horizontal smectic layer and perpendicular ones of the transition region. This 2D defect may be melted, in order to avoid the creation of a transition region structure composed of a large number of dislocations. As a result, linear defect domains can be considered as arrays of oriented defects, straight dislocations of various Burger vectors, whose location is now known, and 2D nematic defects. The possibility of easy variation between the present structure with a moderate amount of dislocations and a structure with a large number of dislocations is also demonstrated.
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Affiliation(s)
- Delphine Coursault
- CNRS UMR 7588, Sorbonne Universités, UPMC Univ Paris 06, Institut des NanoSciences de Paris (INSP), 4 place Jussieu, 75005 Paris, France.
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Coursault D, Blach JF, Grand J, Coati A, Vlad A, Zappone B, Babonneau D, Lévi G, Félidj N, Donnio B, Gallani JL, Alba M, Garreau Y, Borensztein Y, Goldmann M, Lacaze E. Tailoring Anisotropic Interactions between Soft Nanospheres Using Dense Arrays of Smectic Liquid Crystal Edge Dislocations. ACS Nano 2015; 9:11678-11689. [PMID: 26521895 DOI: 10.1021/acsnano.5b02538] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We investigated composite films of gold nanoparticles (NPs)/liquid crystal (LC) defects as a model system to understand the key parameters, which allow for an accurate control of NP anisotropic self-assemblies using soft templates. We combined spectrophotometry, Raman spectroscopy, and grazing incidence small-angle X-ray scattering with calculations of dipole coupling models and soft sphere interactions. We demonstrate that dense arrays of elementary edge dislocations can strongly localize small NPs along the defect cores, resulting in formation of parallel chains of NPs. Furthermore, we show that within the dislocation cores the inter-NP distances can be tuned. This phenomenon appears to be driven by the competition between "soft (nano)sphere" attraction and LC-induced repulsion. We evidence two extreme regimes controlled by the solvent evaporation: (i) when the solvent evaporates abruptly, the spacing between neighboring NPs in the chains is dominated by van der Waals interactions between interdigitated capping ligands, leading to chains of close-packed NPs; (ii) when the solvent evaporates slowly, strong interdigitation between the is avoided, leading to a dominating LC-induced repulsion between NPs associated with the replacement of disordered cores by NPs. The templating of NPs by topological defects, beyond the technological inquiries, may enable creation, investigation, and manipulation of unique collective features for a wide range of nanomaterials.
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Affiliation(s)
- Delphine Coursault
- CNRS UMR 7588, Institut des NanoSciences de Paris (INSP) , 4 place Jussieu, 75005 Paris, France
- The James Franck Institute, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States
| | - Jean-Francois Blach
- UMR 8181, Unité de Catalyse et de Chimie du Solide - UCCS, Université Artois , Faculté des Sciences Jean Perrin, SP18, F-62300 Lens, France
| | - Johan Grand
- Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS), CNRS: UMR7086 Université Paris VII - Paris Diderot, Paris, France
| | - Alessandro Coati
- Synchrotron SOLEIL - SixS Beamline L'Orme des Merisiers Saint Aubin, BP 48 91192 Gif sur Yvette Cedex, France
| | - Alina Vlad
- Synchrotron SOLEIL - SixS Beamline L'Orme des Merisiers Saint Aubin, BP 48 91192 Gif sur Yvette Cedex, France
| | - Bruno Zappone
- CNR-Nanotec, UOS LICRYL-Cosenza c/o Università della Calabria , Cubo 33/B, Rende, 87036, Italy
| | - David Babonneau
- Institut Pprime, Département Physique et Mécanique des Matériaux, UPR 3346 CNRS, Université de Poitiers , SP2MI, 11 Boulevard Marie et Pierre Curie, BP 30179, 86962 Futuroscope Chasseneuil Cedex, France
| | - Georges Lévi
- Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS), CNRS: UMR7086 Université Paris VII - Paris Diderot, Paris, France
| | - Nordin Félidj
- Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS), CNRS: UMR7086 Université Paris VII - Paris Diderot, Paris, France
| | - Bertrand Donnio
- Institut de Physique et de Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504, CNRS-Université de Strasbourg , BP 43, 23 Rue du Loess, F-67034 Strasbourg Cedex 2, France
- Complex Assemblies of Soft Matter Laboratory (COMPASS) , UMI 3254 (CNRS-RHODIA/SOLVAY-University of Pennsylvania), CRTB, 350 George Patterson Boulevard, Bristol, Pennsylvania 19007, United States
| | - Jean-Louis Gallani
- Institut de Physique et de Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504, CNRS-Université de Strasbourg , BP 43, 23 Rue du Loess, F-67034 Strasbourg Cedex 2, France
| | - Michel Alba
- Laboratoire Léon Brillouin UMR12 CNRS-CEA , CEA Saclay, 91191 Gif sur Yvette Cedex, France
| | - Yves Garreau
- Synchrotron SOLEIL - SixS Beamline L'Orme des Merisiers Saint Aubin, BP 48 91192 Gif sur Yvette Cedex, France
- Matériaux et phénomènes quantiques (MPQ), Université Paris Diderot - Paris 7 , Sorbonne-Paris-Cité, CNRS, UMR 7162, 10, rue A. Domon et L. Duquet, 75205 Paris Cedex 13, France
| | - Yves Borensztein
- CNRS UMR 7588, Institut des NanoSciences de Paris (INSP) , 4 place Jussieu, 75005 Paris, France
| | - Michel Goldmann
- CNRS UMR 7588, Institut des NanoSciences de Paris (INSP) , 4 place Jussieu, 75005 Paris, France
| | - Emmanuelle Lacaze
- CNRS UMR 7588, Institut des NanoSciences de Paris (INSP) , 4 place Jussieu, 75005 Paris, France
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Guzzi R, Rizzuti B, Labate C, Zappone B, De Santo MP. Ferric Ions Inhibit the Amyloid Fibrillation of β-Lactoglobulin at High Temperature. Biomacromolecules 2015; 16:1794-801. [PMID: 25989053 DOI: 10.1021/acs.biomac.5b00371] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The energetics of amyloid fibrillar aggregation of β-lactoglobulin (βLG) following incubation at high temperature and acid pH was studied by differential scanning calorimetry in the presence of Cu(2+) or Fe(3+) cations, and without any metal. Cu(2+) and metal-free protein solutions showed a distinct exothermic response that disappeared almost completely when the Fe(3+) molar concentration was ten times greater than the βLG concentration. Thioflavin T fluorescence studies in solution and atomic force microscopy analysis of the deposit left on flat mica substrates by heat-incubated βLG solutions correlated the absence of exothermic response of Fe(3+)-βLG solutions with a lack of fibril production. In contrast, abundant fibril deposits were observed for Cu(2+)-βLG solutions, with a rich polymorphism of multistrand fibrillar structures. Electron paramagnetic resonance revealed that Fe(3+) permanently binds to βLG in the aggregate state whereas Cu(2+) plays a catalytic role without binding to the protein. We propose that Fe(3+) inhibits fibril production after binding to a key region of the protein sequence, possibly interfering with the nucleation step of the fibrillation process and opening a nonfibrillar aggregation pathway. These findings suggest that transition metal ions can be utilized to effectively modulate protein self-assembly into a variety of structures with distinct morphologies at the nanoscale level.
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Affiliation(s)
- Rita Guzzi
- †Department of Physics, University of Calabria, Ponte P. Bucci 31C, 87036 Rende (CS), Italy.,‡CNISM Unit, University of Calabria, Ponte P. Bucci, Cubo 31C, 87036 Rende (CS), Italy
| | - Bruno Rizzuti
- §CNR-NANOTEC, LICRYL-UOS Cosenza and CEMIF.Cal, c/o Department of Physics, University of Calabria, 87036 Rende, Italy
| | - Cristina Labate
- †Department of Physics, University of Calabria, Ponte P. Bucci 31C, 87036 Rende (CS), Italy
| | - Bruno Zappone
- §CNR-NANOTEC, LICRYL-UOS Cosenza and CEMIF.Cal, c/o Department of Physics, University of Calabria, 87036 Rende, Italy
| | - Maria P De Santo
- †Department of Physics, University of Calabria, Ponte P. Bucci 31C, 87036 Rende (CS), Italy
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Zappone B, Patil NJ, Madsen JB, Pakkanen KI, Lee S. Molecular Structure and Equilibrium Forces of Bovine Submaxillary Mucin Adsorbed at a Solid-Liquid Interface. Langmuir 2015; 31:4524-4533. [PMID: 25806669 DOI: 10.1021/acs.langmuir.5b00548] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
By combining dynamic light scattering, circular dichroism spectroscopy, atomic force microscopy, and surface force apparatus, the conformation of bovine submaxillary mucin in dilute solution and nanomechanical properties of mucin layers adsorbed on mica have been investigated. The samples were prepared by additional chromatographic purification of commercially available products. The mucin molecule was found to have a z-average hydrodynamic diameter of ca. 35 nm in phosphate buffered solution, without any particular secondary or tertiary structure. The contour length of the mucin is larger than, yet of the same order of magnitude as the diameter, indicating that the molecule can be modeled as a relatively rigid polymeric chain due to the large persistence length of the central glycosylated domain. Mucin molecules adsorbed abundantly onto mica from saline buffer, generating polymer-like, long-ranged, repulsive, and nonhysteretic forces upon compression of the adsorbed layers. Detailed analysis of such forces suggests that adsorbed mucins had an elongated conformation favored by the stiffness of the central domain. Acidification of aqueous media was chosen as means to reduce mucin-mucin and mucin-substrate electrostatic interactions. The hydrodynamic diameter in solution did not significantly change when the pH was lowered, showing that the large persistence length of the mucin molecule is due to steric hindrance between sugar chains, rather than electrostatic interactions. Remarkably, the force generated by an adsorbed layer with a fixed surface coverage also remained unaltered upon acidification. This observation can be linked to the surface-protective, pH-resistant role of bovine submaxillary mucin in the variable environmental conditions of the oral cavity.
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Affiliation(s)
- Bruno Zappone
- †Consiglio Nazionale delle Ricerche - Istituto di Nanotecnologia (CNR-Nanotec) and LICRYL c/o Dipartimento di Fisica, Università della Calabria, cubo 33/B, Rende (CS) 87036 Italy
| | - Navinkumar J Patil
- §Dipartimento di Fisica, Università della Calabria, cubo 31/C, Rende (CS) 87036 Italy
| | - Jan B Madsen
- ‡Department of Mechanical Engineering, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark
| | - Kirsi I Pakkanen
- ‡Department of Mechanical Engineering, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark
| | - Seunghwan Lee
- ‡Department of Mechanical Engineering, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark
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Kristiansen K, Zeng H, Zappone B, Israelachvili JN. Simultaneous measurements of molecular forces and electro-optical properties of a confined 5CB liquid crystal film using a surface forces apparatus. Langmuir 2015; 31:3965-72. [PMID: 25774432 DOI: 10.1021/acs.langmuir.5b00144] [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: 05/22/2023]
Abstract
Using a surface forces apparatus (SFA), we studied the forces associated with the reorientation of molecules of a common nematic thermotropic liquid crystal, 4'-n-pentyl-4-cyanobiphenyl (5CB), confined between two conducting (silver) surfaces and its optical behavior under the influence of electric fields with varying magnitudes and field directions. A transient attractive force was observed due to partial reorientations of the liquid crystal molecules and the flow of free ions, in addition to a stronger constant capacitance attraction between the silver surfaces. At the same time, the optical properties of the liquid crystals were observed perpendicular to the silver surfaces. Observations of shifts and fluctuations of the extraordinary wave of the (multiple beam) interference fringes measure the refractive index of the director component parallel to the surface, which is sensitive to tilt motion (or reorientation) of the liquid crystal molecules that provided details of the anisotropic orientations of the molecules and domains. Any lateral differential refractive index change is easily observed by optical microscopy. The optical microscope imaging showed that the changes in the optical properties are due to convective flow at domain boundaries of the liquid crystal molecules (and possible free ions) between the two charged surfaces. At low electric fields, propagation of domain boundaries was observed, while at higher electric fields, hexagonal patterns of flowing molecules were observed. The interplay of the force measurements and optical observations reveal a complex dynamic behavior of liquid crystals subjected to varying electric fields in confined spaces.
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Affiliation(s)
| | - Hongbo Zeng
- §Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 2V4, Canada
| | - Bruno Zappone
- ∥Consiglio Nazionale delle Ricerche, Istituto di Nanotecnologia (CNR-Nanotech) Unità di Cosenza, LICRYL c/o Dipartimento di Fisica, Università della Calabria , Cubo 33/B, 87036 Rende (CS), Italy
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20
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Coursault D, Ibrahim BH, Pelliser L, Zappone B, de Martino A, Lacaze E, Gallas B. Modeling the optical properties of self-organized arrays of liquid crystal defects. Opt Express 2014; 22:23182-23191. [PMID: 25321787 DOI: 10.1364/oe.22.023182] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Local full Mueller matrix measurements in the Fourier plane of a microscope lens were used to determine the internal anisotropic ordering in periodic linear arrays of smectic liquid crystal defects, known as 'oily streaks'. We propose a single microstructure-dependent model taking into account the anisotropic dielectric function of the liquid crystal that reproduces the smectic layers orientation and organization in the oily streaks. The calculated Mueller matrix elements are compared to the measured data to reveal the anchoring mechanism of the smectic oily streaks on the substrate and evidence the presence of new type of defect arrangement. Beyond the scientific inquiry, the understanding and control of the internal structure of such arrays offer technological opportunities for developing liquid-crystal based sensors and self-assembled nanostructures.
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Das S, Banquy X, Zappone B, Greene GW, Jay GD, Israelachvili JN. Synergistic Interactions between Grafted Hyaluronic Acid and Lubricin Provide Enhanced Wear Protection and Lubrication. Biomacromolecules 2013; 14:1669-77. [DOI: 10.1021/bm400327a] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Saurabh Das
- Department of Chemical
Engineering, University of California, Santa Barbara, California 93106, United States
| | - Xavier Banquy
- Department of Chemical
Engineering, University of California, Santa Barbara, California 93106, United States
| | - Bruno Zappone
- Consiglio Nazionale
delle Ricerche, CNR-IPCF and Cemif.Cal, Università della Calabria, 31/C Rende (CS),
87036 Italy
| | - George W. Greene
- Institute
of Frontier
Materials, Deakin University, Burwood 3125, Australia
| | - Gregory D. Jay
- Department of Emergency
Medicine and Division of Engineering, Brown University, Providence, Rhode
Island, United States
| | - Jacob N. Israelachvili
- Department of Chemical
Engineering, University of California, Santa Barbara, California 93106, United States
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Ruths M, Zappone B. Direct nanomechanical measurement of an anchoring transition in a nematic liquid crystal subject to hybrid anchoring conditions. Langmuir 2012; 28:8371-8383. [PMID: 22621655 DOI: 10.1021/la204746d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [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 have used a surface forces apparatus to measure the normal force between two solid curved surfaces confining a film of nematic liquid crystal (5CB, 4'-n-pentyl-4-cyanobiphenyl) under hybrid planar-homeotropic anchoring conditions. Upon reduction of the surface separation D, we measured an increasingly repulsive force in the range D = 35-80 nm, reaching a plateau in the range D = 10-35 nm, followed by a short-range oscillatory force at D < 5 nm. The oscillation period was comparable to the cross-sectional diameter of the liquid crystal molecule and characteristic of a configuration with the molecules parallel to the surfaces. These results show that the director field underwent a confinement-induced transition from a splay-bend distorted configuration at large D, which produces elastic repulsive forces, to a uniform planar nondegenerate configuration with broken homeotropic anchoring, which does not produce additional elastic forces as D is decreased. These findings, supported by measurements of the birefringence of the confined film at different film thicknesses, provide the first direct observation of an anchoring transition on the nanometer scale.
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Affiliation(s)
- Marina Ruths
- Department of Chemistry, University of Massachusetts Lowell, Lowell, Massachusetts 01854, USA.
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Coursault D, Grand J, Zappone B, Ayeb H, Lévi G, Félidj N, Lacaze E. Linear self-assembly of nanoparticles within liquid crystal defect arrays. Adv Mater 2012; 24:1461-1465. [PMID: 22318807 DOI: 10.1002/adma.201103791] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Revised: 12/12/2011] [Indexed: 05/31/2023]
Abstract
In the presence of oriented smectic liquid crystal defects, hybrid systems of nanoparticles/liquid crystals form straight chains of nanoparticles of length longer than tens of micrometers and width equal to one single nanoparticle. The interparticle distance in a chain can be varied between a few micrometers and 1.5 nm, highlighting the control of optical absorption by light polarization monitored by gold nanoparticle concentration.
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Buonomenna M, Golemme G, Tone C, De Santo M, Ciuchi F, Perrotta E, Zappone B, Galiano F, Figoli A. Ordering phenomena in nanostructured poly(styrene-b-butadiene-b-styrene) (SBS) membranes for selective ethanol transport. J Memb Sci 2011. [DOI: 10.1016/j.memsci.2011.09.035] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Carbone G, Zappone B, Barberi R, Bartolino R, Musevic I. Direct nanomechanical measurement of layer thickness and compressibility of smectic liquid crystals. Phys Rev E Stat Nonlin Soft Matter Phys 2011; 83:051707. [PMID: 21728556 DOI: 10.1103/physreve.83.051707] [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] [Received: 08/28/2010] [Revised: 04/12/2011] [Indexed: 05/31/2023]
Abstract
Using an atomic force microscope (AFM) we confined a smectic-A liquid crystal (LC) between a flat glass plate and a 10-μm glass sphere attached to the free end of the AFM cantilever. Both surfaces were treated with a surfactant that induces normal alignment of the LC molecules. We measured the force F acting on the cantilever while varying the plate-sphere distance D with subnanometer precision. For D < 50 nm, the force was periodically oscillating and decayed as D was increased. Analyzing the force in the framework of a simple model of elastic deformation of the smectic layers, we have evaluated the undeformed layer thickness a(0) and compressibility modulus B. Compared to other techniques used to determine a(0) and B, AFM measurements are faster and require a much smaller amount (microliters) of LC. Moreover, they are based on purely mechanical deformations of the LC structure and do not require any static or radiative electromagnetic field.
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Rizzuti B, Zappone B, De Santo MP, Guzzi R. Native beta-lactoglobulin self-assembles into a hexagonal columnar phase on a solid surface. Langmuir 2010; 26:1090-1095. [PMID: 19877696 DOI: 10.1021/la902464f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Using electron scanning microscopy, we have studied the protein deposit left on silicon and mica substrates by dried droplets of aqueous solutions of bovine beta-lactoglobulin at low concentration and pH = 2-7. We have observed different self-assembled structures: homogeneous layers, hexagonal platelets and flower-shaped patterns laying flat on the surface, and rods formed by columns. Homogeneous layers covered the largest area of the droplet deposit. The other structures were found in small isolated regions, where the protein solution dried in the form of microdroplets. The presence of hexagonal platelets, flower-shaped patterns and columnar rods shows that beta-lactoglobulin self-assembles at the surface in a hexagonal columnar phase, which has never been observed in solution. A comparison with proteins showing similar aggregates suggests that beta-lactoglobulin structures grow from hexagonal germs composed of discotic nanometric building blocks, possibly possessing an octameric structure. We propose that discotic building blocks of beta-lactoglobulin may be produced by the anisotropic interaction with the solid surface.
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Affiliation(s)
- Bruno Rizzuti
- Licryl CNR-INFM and Cemif.Cal, University of Calabria, Ponte P. Bucci, Cubo 31C, 87036 Rende (CS), Italy
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Alves VM, Nakamatsu S, Oliveira EA, Zappone B, Richetti P. Anisotropic reversible aggregation of latex nanoparticles suspended in a lyotropic nematic liquid crystal: effect of gradients of biaxial order. Langmuir 2009; 25:11849-11856. [PMID: 19702247 DOI: 10.1021/la901520r] [Citation(s) in RCA: 2] [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] [Indexed: 05/28/2023]
Abstract
We studied the anisotropic aggregation of spherical latex particles dispersed in a lyotropic liquid crystal presenting three nematic phases: calamitic, biaxial, and discotic. We observed that in the nematic calamitic phase aggregates of latex particles are formed, which become larger and anisotropic in the vicinity of the transition to the discotic phase, due to a coalescence process. Such aggregates are weakly anisotropic and up to 50 microm long and tend to align parallel to the director field. At the transition to the discotic phase, the aggregates dissociated and re-formed when the system was brought back to the calamitic phase. This shows that the aggregation is due to attractive and repulsive forces generated by the particular structure of the nematic phase. The surface-induced positional order was investigated by surface force apparatus experiments with the lyotropic system confined between mica surfaces, revealing the existence of a presmectic wetting layer around the surfaces and oscillating forces of increasing amplitude as the confinement thickness was decreased. We discuss the possible mechanisms responsible for the reversible aggregation of latex particles, and we propose that capillary condensation of the NC phase, induced by the confinement between the particles, could reduce or remove the gradient of order parameter, driving the transition of aggregates from solidlike to liquidlike and gaslike.
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Affiliation(s)
- V M Alves
- Instituto de Física, Universidade de São Paulo, 05508-090 São Paulo, Brazil
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Zappone B, Lacaze E. Surface-frustrated periodic textures of smectic- a liquid crystals on crystalline surfaces. Phys Rev E Stat Nonlin Soft Matter Phys 2008; 78:061704. [PMID: 19256855 DOI: 10.1103/physreve.78.061704] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Indexed: 05/27/2023]
Abstract
Using polarizing optical microscopy we studied thin films and droplets of smectic- A 4-cyano- 4;{'} -n-octylbiphenyl (8CB) liquid crystal deposited in air on crystalline surfaces of muscovite mica that induce monostable planar anchoring. The competition with the homeotropic anchoring at the 8CB-air interface leads to the formation of one-dimensional (1D) patterns composed of straight, parallel defect domains that are organized in periodic arrays over areas as large as several mm;{2} . We have developed a simple model which identifies the arrays with self-assembled "oily streaks," comprising straight disclination lines and curvature walls. The model reproduces the observed monotonic increase of the period p with the film thickness h in the range p=1-4 microm and h=0.8-17 microm. For higher values of h we observed a sharp transition to a 2D lattice of fragmented focal conic domains. Despite the apparent generality of our model for hybrid planar-homeotropic anchoring conditions, periodic arrays of straight oily streaks have been observed so far only for 8CB on crystalline surfaces such as mica or MoS2 . Our model indicates that this specificity is due to a particularly strong anchoring of the liquid crystal on such surfaces.
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Affiliation(s)
- Bruno Zappone
- LICRYL, CNR-INFM Regional Laboratory, and Centro di Eccellenza per i Materiali Innovati Funzionali della Calabria, Università della Calabria, cubo 33b, Rende (CS), 87036 Italy.
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Greene GW, Zappone B, Zhao B, Söderman O, Topgaard D, Rata G, Israelachvili JN. Changes in pore morphology and fluid transport in compressed articular cartilage and the implications for joint lubrication. Biomaterials 2008; 29:4455-62. [PMID: 18755507 DOI: 10.1016/j.biomaterials.2008.07.046] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Accepted: 07/26/2008] [Indexed: 10/21/2022]
Abstract
Cartilage sections were cut from the middle zone of pig knee articular cartilage and attached to substrates in two different kinds of newly designed 'pressure cells', one for fluorescence the other for NMR measurements. The fluorescence cell was filled with buffer solution containing fluorescently marked 70 kDa dextran which was allowed to diffuse into the cartilage pores. A second glass surface was then pressed down onto the thin cartilage sample under different loads (pressures), and the resulting compression (strain) and change in pore volume were measured as a function of time, simultaneously with measurements of the lateral diffusion and flow pattern of the dextran molecules using Fluorescence Recovery After Photobleaching (FRAP). Complementary experiments were made on the normal diffusion coefficients of pure electrolyte solutions (no dextran) in thicker cartilage sections with pulse-gradient NMR using a new pressure cell suitable for such measurements. Taken together our results show that the highly anisotropic structure of cartilage has a strong effect on the way fluid diffuses laterally and normally at different stages of compression. Our results also show how geometric constraints on a cartilage network and trapped high MW polymer such as HA during normal compressions are likely to affect both the normal and the lateral mobilities of polyelectrolytes and water.
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Affiliation(s)
- George W Greene
- Materials Department, University of California at Santa Barbara, CA 93106, USA
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Zappone B, Greene GW, Oroudjev E, Jay GD, Israelachvili JN. Molecular aspects of boundary lubrication by human lubricin: effect of disulfide bonds and enzymatic digestion. Langmuir 2008; 24:1495-1508. [PMID: 18067335 DOI: 10.1021/la702383n] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Lubricin (LUB) is a glycoprotein of the synovial cavity of human articular joints, where it serves as an antiadhesive, boundary lubricant, and regulating factor for the cartilage surface. It has been proposed that these properties are related to the presence of a long, extended, heavily glycosylated and highly hydrated mucinous domain in the central part of the LUB molecule. In this work, we show that LUB has a contour length of 220 +/- 30 nm and a persistence length of < or =10 nm. LUB molecules aggregate in oligomers where the protein extremities are linked by disulfide bonds. We have studied the effect of proteolytic digestion by chymotrypsin and removal of the disulfide bonds, both of which mainly affect the N- and C- terminals of the protein, on the adsorption, normal forces, friction (lubrication) forces, and wear of LUB layers adsorbed on smooth, negatively charged mica surfaces, where the protein naturally forms lubricating polymer brush-like layers. After in situ digestion, the surface coverage was drastically reduced, the normal forces were altered, and both the coefficient of friction and the wear were dramatically increased (the COF increased to mu = 1.1-1.9), indicating that the mucinous domain was removed from the surface. Removal of disulfide bonds did not change the surface coverage or the overall features of the normal forces; however, we find an increase in the friction coefficient from mu = 0.02-0.04 to mu = 0.13-1.17 in the pressure regime below 6 atm, which we attribute to a higher affinity of the protein terminals for the surface. The necessary condition for LUB to be a good lubricant is that the protein be adsorbed to the surface via its terminals, leaving the central mucin domain free to form a low-friction, surface-protecting layer. Our results suggest that this "end-anchoring" has to be strong enough to impart the layer a sufficient resistance to shear, but without excessively restricting the conformational freedom of the adsorbed proteins.
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Affiliation(s)
- Bruno Zappone
- Centro di Eccellenza LiCryL, University of Calabria, Rende (CS), Italy
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Zappone B, Ruths M, Greene GW, Jay GD, Israelachvili JN. Adsorption, lubrication, and wear of lubricin on model surfaces: polymer brush-like behavior of a glycoprotein. Biophys J 2006; 92:1693-708. [PMID: 17142292 PMCID: PMC1796837 DOI: 10.1529/biophysj.106.088799] [Citation(s) in RCA: 194] [Impact Index Per Article: 10.8] [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: 11/18/2022] Open
Abstract
Using a surface force apparatus, we have measured the normal and friction forces between layers of the human glycoprotein lubricin, the major boundary lubricant in articular joints, adsorbed from buffered saline solution on various hydrophilic and hydrophobic surfaces: i), negatively charged mica, ii), positively charged poly-lysine and aminothiol, and iii), hydrophobic alkanethiol monolayers. On all these surfaces lubricin forms dense adsorbed layers of thickness 60-100 nm. The normal force between two surfaces is always repulsive and resembles the steric entropic force measured between layers of end-grafted polymer brushes. This is the microscopic mechanism behind the antiadhesive properties showed by lubricin in clinical tests. For pressures up to approximately 6 atm, lubricin lubricates hydrophilic surfaces, in particular negatively charged mica (friction coefficient mu = 0.02-0.04), much better than hydrophobic surfaces (mu > 0.3). At higher pressures, the friction coefficient is higher (mu > 0.2) for all surfaces considered and the lubricin layers rearrange under shear. However, the glycoprotein still protects the underlying substrate from damage up to much higher pressures. These results support recent suggestions that boundary lubrication and wear protection in articular joints are due to the presence of a biological polyelectrolyte on the cartilage surfaces.
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Affiliation(s)
- Bruno Zappone
- Materials Department and Materials Research Laboratory, University of California Santa Barbara, Santa Barbara, California, USA
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Rodríguez-Hernández J, Babin J, Zappone B, Lecommandoux S. Preparation of Shell Cross-Linked Nano-Objects from Hybrid-Peptide Block Copolymers. Biomacromolecules 2005; 6:2213-20. [PMID: 16004465 DOI: 10.1021/bm0501499] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Supramolecular structures formed by self-assembly of diblock copolymers in solution are stable over restricted environmental conditions: concentration, temperature, pH, or ion strength among others. To enlarge their domain of application, it appears necessary to develop stabilization strategies. We report here different strategies to stabilize the shell of micelles formed by self-assembly of amphiphilic polydiene-b-polypeptide diblock copolymers. For this purpose, covalent bonds can be formed between either amine or carboxylic acid groups distributed along the soluble peptide block and a cross-linking agent that contains respectively aldehyde or amine functions. Shell stabilization affords systems with unique properties that combine three main advantages: shape persistence, control of the porosity, and stimuli-responsive behavior. The covalent capture of such macromolecular objects has been studied by light scattering, AFM, and conductimetry measurements.
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Affiliation(s)
- Juan Rodríguez-Hernández
- Laboratoire de Chimie des Polymères Organiques (LCPO-UMR5629), ENSCPB-University Bordeaux 1, 16, Av. Pey Berland, 33607 Pessac Cedex, France
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Zappone B, Richetti P, Barberi R, Bartolino R, Nguyen HT. Forces in nematic liquid crystals constrained to the nanometer scale under hybrid anchoring conditions. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 71:041703. [PMID: 15903687 DOI: 10.1103/physreve.71.041703] [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: 08/07/2004] [Indexed: 05/02/2023]
Abstract
Using a surface forces apparatus we have studied two thermotropic nematic liquid crystals (5CB and ME10.5) subjected to hybrid (homeotropic/planar) anchoring conditions. A film of nematic material is constrained between two curved smooth surfaces separated by less than 2500 A . The intersurface force is nonmonotonic with the separation, being repulsive for thicknesses larger than approximately 100 A and strongly adhesive at a shorter scale. While the repulsion can be qualitatively explained by an elastic model of director deformation, including anchoring deviation at the boundaries, the attraction cannot be explained either by elasticity or by dispersive forces. The expected confinement-induced anchoring transition has not been observed for a thickness as small as 200 A .
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Affiliation(s)
- B Zappone
- Liquid Crystals Laboratory (Cemif. Cal.-Università della Calabria), Ponte P. Bucci, cubo 33b, 87036 Arcavacata di Rende (CS), Italy.
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