Sorption of gold by naked and thiol-capped magnetite nanoparticles: An XPS approach

O. F. Odio, L. Lartundo-Rojas, P. Santiago-Jacinto, R. Martínez, E. Reguera

Research output: Contribution to journalArticle

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Abstract

Iron oxide nanoparticles are promising materials for many technological and environmental applications due to their versatile functionalization and magnetic properties that allow a facile remote control, separation and analyte recovery. In this contribution, the results of gold(III) sorption by naked and DMSA-capped (DMSA = m-2,3,dimercapto succinic acid) magnetite nanoparticles are discussed. Magnetite nanoparticles of 8 nm diameter were first synthesized by thermal decomposition of iron(III) oleate followed by a ligand exchange reaction to substitute oleic acid (OA) molecules by DMSA. Such systems of coated magnetite nanoparticles were characterized with Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurements. FT-IR spectroscopy suggests that in Fe 3 O 4 @DMSA the organic coating is not homogeneous and it interacts with surface iron cations either through the carboxylate groups (by forming bridging bidentate complexes) or through disulfide bonds after oxidation of thiol groups. The magnetic measurements show that the nanoparticles are in the superparamagnetic range at room temperature despite the presence of dipolar interactions. The gold(III) adsorption isotherms for both bare Fe 3 O 4 and Fe 3 O 4 @DMSA nanoparticles were fitted with the Langmuir and Freundlich models. The better fit for the second model suggests the heterogeneous nature of the surface and the multilayer nature of gold adsorption. XPS spectra reveal that the adsorption of Au(III) ions comprises mostly its reduction to Au 0 by disulfide groups, although there is a fraction of these gold ions that is reduced directly onto the bare surface of the iron oxide leading to Fe(II) oxidation. According to the recorded optical absorption spectra, gold clusters of metallic character are also formed at the nanoparticle surface, a fraction of them forming subnanometer aggregates. The magnetic recovery of gold by this nanosystem could be extendable to other heavy metals. © 2014 American Chemical Society.
Original languageAmerican English
Pages (from-to)2776-2791
Number of pages2496
JournalJournal of Physical Chemistry C
DOIs
StatePublished - 6 Feb 2014

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Magnetite Nanoparticles
Magnetite nanoparticles
Succimer
Sulfhydryl Compounds
thiols
Gold
magnetite
sorption
Sorption
X ray photoelectron spectroscopy
gold
nanoparticles
Nanoparticles
Magnetic variables measurement
Oleic Acid
Iron oxides
Disulfides
disulfides
iron oxides
Iron

Cite this

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title = "Sorption of gold by naked and thiol-capped magnetite nanoparticles: An XPS approach",
abstract = "Iron oxide nanoparticles are promising materials for many technological and environmental applications due to their versatile functionalization and magnetic properties that allow a facile remote control, separation and analyte recovery. In this contribution, the results of gold(III) sorption by naked and DMSA-capped (DMSA = m-2,3,dimercapto succinic acid) magnetite nanoparticles are discussed. Magnetite nanoparticles of 8 nm diameter were first synthesized by thermal decomposition of iron(III) oleate followed by a ligand exchange reaction to substitute oleic acid (OA) molecules by DMSA. Such systems of coated magnetite nanoparticles were characterized with Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurements. FT-IR spectroscopy suggests that in Fe 3 O 4 @DMSA the organic coating is not homogeneous and it interacts with surface iron cations either through the carboxylate groups (by forming bridging bidentate complexes) or through disulfide bonds after oxidation of thiol groups. The magnetic measurements show that the nanoparticles are in the superparamagnetic range at room temperature despite the presence of dipolar interactions. The gold(III) adsorption isotherms for both bare Fe 3 O 4 and Fe 3 O 4 @DMSA nanoparticles were fitted with the Langmuir and Freundlich models. The better fit for the second model suggests the heterogeneous nature of the surface and the multilayer nature of gold adsorption. XPS spectra reveal that the adsorption of Au(III) ions comprises mostly its reduction to Au 0 by disulfide groups, although there is a fraction of these gold ions that is reduced directly onto the bare surface of the iron oxide leading to Fe(II) oxidation. According to the recorded optical absorption spectra, gold clusters of metallic character are also formed at the nanoparticle surface, a fraction of them forming subnanometer aggregates. The magnetic recovery of gold by this nanosystem could be extendable to other heavy metals. {\circledC} 2014 American Chemical Society.",
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Sorption of gold by naked and thiol-capped magnetite nanoparticles: An XPS approach. / Odio, O. F.; Lartundo-Rojas, L.; Santiago-Jacinto, P.; Martínez, R.; Reguera, E.

In: Journal of Physical Chemistry C, 06.02.2014, p. 2776-2791.

Research output: Contribution to journalArticle

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T1 - Sorption of gold by naked and thiol-capped magnetite nanoparticles: An XPS approach

AU - Odio, O. F.

AU - Lartundo-Rojas, L.

AU - Santiago-Jacinto, P.

AU - Martínez, R.

AU - Reguera, E.

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N2 - Iron oxide nanoparticles are promising materials for many technological and environmental applications due to their versatile functionalization and magnetic properties that allow a facile remote control, separation and analyte recovery. In this contribution, the results of gold(III) sorption by naked and DMSA-capped (DMSA = m-2,3,dimercapto succinic acid) magnetite nanoparticles are discussed. Magnetite nanoparticles of 8 nm diameter were first synthesized by thermal decomposition of iron(III) oleate followed by a ligand exchange reaction to substitute oleic acid (OA) molecules by DMSA. Such systems of coated magnetite nanoparticles were characterized with Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurements. FT-IR spectroscopy suggests that in Fe 3 O 4 @DMSA the organic coating is not homogeneous and it interacts with surface iron cations either through the carboxylate groups (by forming bridging bidentate complexes) or through disulfide bonds after oxidation of thiol groups. The magnetic measurements show that the nanoparticles are in the superparamagnetic range at room temperature despite the presence of dipolar interactions. The gold(III) adsorption isotherms for both bare Fe 3 O 4 and Fe 3 O 4 @DMSA nanoparticles were fitted with the Langmuir and Freundlich models. The better fit for the second model suggests the heterogeneous nature of the surface and the multilayer nature of gold adsorption. XPS spectra reveal that the adsorption of Au(III) ions comprises mostly its reduction to Au 0 by disulfide groups, although there is a fraction of these gold ions that is reduced directly onto the bare surface of the iron oxide leading to Fe(II) oxidation. According to the recorded optical absorption spectra, gold clusters of metallic character are also formed at the nanoparticle surface, a fraction of them forming subnanometer aggregates. The magnetic recovery of gold by this nanosystem could be extendable to other heavy metals. © 2014 American Chemical Society.

AB - Iron oxide nanoparticles are promising materials for many technological and environmental applications due to their versatile functionalization and magnetic properties that allow a facile remote control, separation and analyte recovery. In this contribution, the results of gold(III) sorption by naked and DMSA-capped (DMSA = m-2,3,dimercapto succinic acid) magnetite nanoparticles are discussed. Magnetite nanoparticles of 8 nm diameter were first synthesized by thermal decomposition of iron(III) oleate followed by a ligand exchange reaction to substitute oleic acid (OA) molecules by DMSA. Such systems of coated magnetite nanoparticles were characterized with Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurements. FT-IR spectroscopy suggests that in Fe 3 O 4 @DMSA the organic coating is not homogeneous and it interacts with surface iron cations either through the carboxylate groups (by forming bridging bidentate complexes) or through disulfide bonds after oxidation of thiol groups. The magnetic measurements show that the nanoparticles are in the superparamagnetic range at room temperature despite the presence of dipolar interactions. The gold(III) adsorption isotherms for both bare Fe 3 O 4 and Fe 3 O 4 @DMSA nanoparticles were fitted with the Langmuir and Freundlich models. The better fit for the second model suggests the heterogeneous nature of the surface and the multilayer nature of gold adsorption. XPS spectra reveal that the adsorption of Au(III) ions comprises mostly its reduction to Au 0 by disulfide groups, although there is a fraction of these gold ions that is reduced directly onto the bare surface of the iron oxide leading to Fe(II) oxidation. According to the recorded optical absorption spectra, gold clusters of metallic character are also formed at the nanoparticle surface, a fraction of them forming subnanometer aggregates. The magnetic recovery of gold by this nanosystem could be extendable to other heavy metals. © 2014 American Chemical Society.

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