Mechanism of Pb Adsorption to Fatty Acid Langmuir Monolayers Studied by X-ray Absorption Fine Structure Spectroscopy

Maxim I. Boyanov; Jan Kmetko; Tomohiro Shibata; Alokmay Datta; Pulak Dutta; Bruce A. Bunker

doi:10.1021/jp0341772

Mechanism of Pb Adsorption to Fatty Acid Langmuir Monolayers Studied by X-ray Absorption Fine Structure Spectroscopy

Maxim I. Boyanov^*, Jan Kmetko, Tomohiro Shibata, Alokmay Datta, Pulak Dutta, Bruce A. Bunker

^*Corresponding author for this work

Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

31 Scopus citations

Abstract

The local atomic environment of lead (Pb) adsorbed to a CH ₃(CH₂)₁₉COOH Langmuir monolayer was investigated in situ using grazing-incidence X-ray absorption fine structure (GI-XAFS) spectroscopy at the Pb L_III edge. Measurements were performed at pH 6.5 of the 10_-5 M PbCl₂ solution subphase, a condition under which grazing incidence diffraction (GID) revealed a large-area commensurate superstructure underneath the close-packed organic monolayer. The XAFS results indicate covalent binding of the Pb cations to the carboxyl headgroups, and the observed Pb-Pb coordination suggests that the metal is adsorbed as a hydrolysis polymer, rather than as individual Pb ²⁺ ions. The data are consistent with a bidentate chelating mechanism and a one Pb atom to one carboxyl headgroup binding stoichiomelry. We discuss how this adsorption model can explain the peculiarities observed with Pb in previous metal-Langmuir monolayer studies. A systematic study of lead perchlorate and lead acetate aqueous solutions is presented and used in the analysis. XAFS multiple scattering effects from alignment of the Pb-C-C atoms in the lead acetate solutions are reported.

Original language	English (US)
Pages (from-to)	9780-9788
Number of pages	9
Journal	Journal of Physical Chemistry B
Volume	107
Issue number	36
DOIs	https://doi.org/10.1021/jp0341772
State	Published - Sep 11 2003

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Surfaces, Coatings and Films
Materials Chemistry

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title = "Mechanism of Pb Adsorption to Fatty Acid Langmuir Monolayers Studied by X-ray Absorption Fine Structure Spectroscopy",

abstract = "The local atomic environment of lead (Pb) adsorbed to a CH 3(CH2)19COOH Langmuir monolayer was investigated in situ using grazing-incidence X-ray absorption fine structure (GI-XAFS) spectroscopy at the Pb LIII edge. Measurements were performed at pH 6.5 of the 10-5 M PbCl2 solution subphase, a condition under which grazing incidence diffraction (GID) revealed a large-area commensurate superstructure underneath the close-packed organic monolayer. The XAFS results indicate covalent binding of the Pb cations to the carboxyl headgroups, and the observed Pb-Pb coordination suggests that the metal is adsorbed as a hydrolysis polymer, rather than as individual Pb 2+ ions. The data are consistent with a bidentate chelating mechanism and a one Pb atom to one carboxyl headgroup binding stoichiomelry. We discuss how this adsorption model can explain the peculiarities observed with Pb in previous metal-Langmuir monolayer studies. A systematic study of lead perchlorate and lead acetate aqueous solutions is presented and used in the analysis. XAFS multiple scattering effects from alignment of the Pb-C-C atoms in the lead acetate solutions are reported.",

author = "Boyanov, {Maxim I.} and Jan Kmetko and Tomohiro Shibata and Alokmay Datta and Pulak Dutta and Bunker, {Bruce A.}",

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T1 - Mechanism of Pb Adsorption to Fatty Acid Langmuir Monolayers Studied by X-ray Absorption Fine Structure Spectroscopy

AU - Boyanov, Maxim I.

AU - Kmetko, Jan

AU - Shibata, Tomohiro

AU - Datta, Alokmay

AU - Dutta, Pulak

AU - Bunker, Bruce A.

PY - 2003/9/11

Y1 - 2003/9/11

N2 - The local atomic environment of lead (Pb) adsorbed to a CH 3(CH2)19COOH Langmuir monolayer was investigated in situ using grazing-incidence X-ray absorption fine structure (GI-XAFS) spectroscopy at the Pb LIII edge. Measurements were performed at pH 6.5 of the 10-5 M PbCl2 solution subphase, a condition under which grazing incidence diffraction (GID) revealed a large-area commensurate superstructure underneath the close-packed organic monolayer. The XAFS results indicate covalent binding of the Pb cations to the carboxyl headgroups, and the observed Pb-Pb coordination suggests that the metal is adsorbed as a hydrolysis polymer, rather than as individual Pb 2+ ions. The data are consistent with a bidentate chelating mechanism and a one Pb atom to one carboxyl headgroup binding stoichiomelry. We discuss how this adsorption model can explain the peculiarities observed with Pb in previous metal-Langmuir monolayer studies. A systematic study of lead perchlorate and lead acetate aqueous solutions is presented and used in the analysis. XAFS multiple scattering effects from alignment of the Pb-C-C atoms in the lead acetate solutions are reported.

AB - The local atomic environment of lead (Pb) adsorbed to a CH 3(CH2)19COOH Langmuir monolayer was investigated in situ using grazing-incidence X-ray absorption fine structure (GI-XAFS) spectroscopy at the Pb LIII edge. Measurements were performed at pH 6.5 of the 10-5 M PbCl2 solution subphase, a condition under which grazing incidence diffraction (GID) revealed a large-area commensurate superstructure underneath the close-packed organic monolayer. The XAFS results indicate covalent binding of the Pb cations to the carboxyl headgroups, and the observed Pb-Pb coordination suggests that the metal is adsorbed as a hydrolysis polymer, rather than as individual Pb 2+ ions. The data are consistent with a bidentate chelating mechanism and a one Pb atom to one carboxyl headgroup binding stoichiomelry. We discuss how this adsorption model can explain the peculiarities observed with Pb in previous metal-Langmuir monolayer studies. A systematic study of lead perchlorate and lead acetate aqueous solutions is presented and used in the analysis. XAFS multiple scattering effects from alignment of the Pb-C-C atoms in the lead acetate solutions are reported.

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Mechanism of Pb Adsorption to Fatty Acid Langmuir Monolayers Studied by X-ray Absorption Fine Structure Spectroscopy

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