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Abstract
AbstractThe mean particle size of magnetite precipitated in aqueous solution can be adjusted and stabilized against ripening over a large nanometric range (1.5 to 12.5 nm) by controlling the pH and the ionic strength imposed by a non-complexing salt in the precipitation medium. The higher the pH and the ionic strength are, the smaller the particle size is. An explanation for this phenomenon is based on the lowering of the oxide-solution interracial tension due to the surface electrostatic charge increase. A critical pH value corresponding to the saturation of the interface is defined and calculated. When the precipitation is effected above this critical pH value, the spontaneous decrease in surface area by ripening is avoided and, for a given ionic strength, the particle size depends only on the acidity. This model correlates well with the experimental results. This provides the first experimental example of thermodynamic stabilization of oxide nanoparticles.
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Lemaire BJ, Davidson P, Panine P, Jolivet JP. Magnetic-field-induced nematic-columnar phase transition in aqueous suspensions of goethite (alpha-FeOOH) nanorods. Phys Rev Lett 2004; 93:267801. [PMID: 15698022 DOI: 10.1103/physrevlett.93.267801] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Indexed: 05/24/2023]
Abstract
Colloidal aqueous suspensions of goethite lath-shaped nanorods form nematic and isotropic phases. We show that they also display a 2D rectangular (c2mm) columnar phase at volume fractions phi larger than 15%. Interestingly, the nematic-columnar first-order transition can also be triggered by applying to the nematic phase a magnetic field of intensity decreasing with phi (1 T at 8.5%; 0.5 T at 12%). Single domains of the columnar phase were thus produced and their structure investigated by synchrotron x-ray scattering. This magnetic-field-induced transition is fully reversible and reproducible.
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Affiliation(s)
- B J Lemaire
- Laboratoire de Physique des Solides, UMR CNRS 8502, Bâtiment 510, Université Paris-Sud, 91405 Orsay, France
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Lemaire BJ, Davidson P, Petermann D, Panine P, Dozov I, Stoenescu D, Jolivet JP. Physical properties of aqueous suspensions of goethite (alpha-FeOOH) nanorods. Part II: In the nematic phase. Eur Phys J E Soft Matter 2004; 13:309-319. [PMID: 15103524 DOI: 10.1140/epje/i2003-10079-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
At volume fractions larger than 8.5%, aqueous suspensions of lath-like goethite (alpha-FeOOH) nanorods form a lyotropic nematic phase. In this article, we first discuss the nematic ordering within statistical-physics models of the isotropic/nematic phase transition. We then describe the influence of a magnetic field on the nematic phase. Because the nanorods bear permanent magnetic moments, the nematic suspensions have dipolar order and very low Frederiks thresholds. Moreover, the nematic phase aligns parallel to a small magnetic field but realigns perpendicular to a high field because of a competition between the permanent moments of the nanorods and their negative anisotropy of magnetic susceptibility. This magneto-optical study of the nematic phase is completely consistent with that of the isotropic phase of the same suspensions published in Part I (this issue, p. 291). Besides, we demonstrate the field-induced biaxiality of a nematic single domain aligned perpendicular to the field. We also describe here preliminary experiments where an a.c. electric field is applied to the nematic phase. Both field amplitude and frequency were found to control the alignment direction and homeotropic-to-planar alignment transitions were observed. From this data, simple models were used to estimate some physical constants of the nematic phase.
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Affiliation(s)
- B J Lemaire
- Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris-Sud, 91405, Orsay, France
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Lemaire BJ, Davidson P, Ferré J, Jamet JP, Petermann D, Panine P, Dozov I, Jolivet JP. Physical properties of aqueous suspensions of goethite (alpha-FeOOH) nanorods. Part I: In the isotropic phase. Eur Phys J E Soft Matter 2004; 13:291-308. [PMID: 15103523 DOI: 10.1140/epje/i2003-10078-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Depending on volume fraction, aqueous suspensions of goethite (alpha-FeOOH) nanorods form a liquid-crystalline nematic phase (above 8.5%) or an isotropic liquid phase (below 5.5%). In this article, we investigate by small-angle X-ray scattering, magneto-optics, and magnetometry the influence of a magnetic field on the isotropic phase. After a brief description of the synthesis and characterisation of the goethite nanorod suspensions, we show that the disordered phase becomes very anisotropic under a magnetic field that aligns the particles. Moreover, we observe that the nanorods align parallel to a small field (< 350 mT), but realign perpendicular to a large enough field (> 350 mT). This phenomenon is interpreted as due to the competition between the influence of the nanorod permanent magnetic moment and a negative anisotropy of magnetic susceptibility. Our interpretation is supported by the behaviour of the suspensions in an alternating magnetic field. Finally, we propose a model that explains all experimental observations in a consistent way.
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Affiliation(s)
- B J Lemaire
- Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris-Sud, 91405, Orsay, France
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Lemaire BJ, Davidson P, Ferré J, Jamet JP, Panine P, Dozov I, Jolivet JP. Outstanding magnetic properties of nematic suspensions of goethite (alpha-FeOOH) nanorods. Phys Rev Lett 2002; 88:125507. [PMID: 11909477 DOI: 10.1103/physrevlett.88.125507] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2001] [Indexed: 05/23/2023]
Abstract
Aqueous suspensions of goethite (alpha-FeOOH) nanorods form a mineral lyotropic nematic phase that aligns in a very low magnetic field (20 mT for samples 20 microm thick). The particles orient along the field direction at intensities smaller than 350 mT, but they reorient perpendicular to the field beyond 350 mT. This outstanding behavior is also observed in the isotropic phase which has a very strong magnetic-field induced birefringence that could be interesting for applications. We interpret these magnetic effects as resulting from a competition between a nanorod remanent magnetic moment and a negative anisotropy of its magnetic susceptibility.
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Affiliation(s)
- B J Lemaire
- Laboratoire de Physique des Solides, UMR CNRS 8502, Bâtiment 510, Université Paris-Sud, 91405 Orsay, France
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Rannou P, Chassefiere E, Encrenaz T, Erard S, Genin JM, Ingrin J, Jambon A, Jolivet JP, Raulin F, Renault P, Rochette P, Person A, Siguier JM, Toublanc D. EXOCAM: Mars in a box to simulate soil-atmosphere interactions. Adv Space Res 2001; 27:189-193. [PMID: 11603400 DOI: 10.1016/s0273-1177(01)00046-1] [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] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We present the principle of the EXOCAM chamber, devoted to the study of physical-chemical interactions between the atmosphere and the surface and subsurface in Mars conditions. The purpose of this experiment is to reach a better knowledge of the physical and chemical processes that altered the atmosphere-soil coupled system. We describe the scientific goals of EXOCAM, the multiple fields that will benefit from this experiment and the instrumentation that is devoted to the analysis of the results. We also give a description of the chamber and its main devices.
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Affiliation(s)
- P Rannou
- Service d'Aeronomie/IPSL, Univ. Paris 6, 4, place Jussieu, 75252 Paris Cedex 05, France
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Vayssières L, Chanéac C, Tronc E, Jolivet JP. Size Tailoring of Magnetite Particles Formed by Aqueous Precipitation: An Example of Thermodynamic Stability of Nanometric Oxide Particles. J Colloid Interface Sci 1998; 205:205-212. [PMID: 9735184 DOI: 10.1006/jcis.1998.5614] [Citation(s) in RCA: 296] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The particle mean size of magnetite precipitated in aqueous solution can be adjusted and stabilized against ripening over a large range at the nanometric scale (1.5-12.5 nm). Such a tailoring of particles is obtained by controlling the pH and the ionic strength imposed by a noncomplexing salt in the precipitation medium. The higher the pH and the ionic strength are, the smaller the particle size is. Above a critical pH value, which depends on the ionic strength and the temperature, the secondary particle growth by Ostwald ripening does not take place anymore. The stabilization of nanoparticles seems to result from thermodynamics rather than kinetics. Copyright 1998 Academic Press.
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Affiliation(s)
- L Vayssières
- Chimie de la Matière Condensée, UMR-CNRS 7574, UniversitéPierre et Marie Curie, 4 Place Jussieu, Paris Cedex 05, 75 252, France
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Dormann JL, Ezzir A, Cherkaoui R, Nogues M, Lucari F, d'Orazio F, Godinho M, Tronc E, Jolivet JP, Fiorani D. Static and Dynamical Properties of γ-Fe2O3 Nanoparticles. ACTA ACUST UNITED AC 1997. [DOI: 10.1051/jp4:19971208] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Dormann JL, D'Orazio F, Lucari F, Tronc E, Prené P, Jolivet JP, Fiorani D, Cherkaoui R, Noguès M. Thermal variation of the relaxation time of the magnetic moment of gamma -Fe2O3 nanoparticles with interparticle interactions of various strengths. Phys Rev B Condens Matter 1996; 53:14291-14297. [PMID: 9983226 DOI: 10.1103/physrevb.53.14291] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Tronc E, Prene P, Jolivet JP, d'Orazio F, Lucari F, Fiorani D, Godinho M, Cherkaoui R, Nogues M, Dormann JL. Magnetic behaviour of γ-Fe2O3 nanoparticles by mössbauer spectroscopy and magnetic measurements. ACTA ACUST UNITED AC 1995. [DOI: 10.1007/bf02146310] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Prené P, Tronc E, Jolivet JP, Livage J, Cherkaoui R, Noguès M, Dormann JL. Mössbauer investigation of non-aggregated γ-Fe2O3 particles. ACTA ACUST UNITED AC 1994. [DOI: 10.1007/bf02072885] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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