Neutron reflectometry reveals the internal structure of organic compounds deposited on aluminum oxide

Melanie Mayes; Sindhu Jagadamma; Haile Ambaye; Loukas Petridis; Valeria Lauter

doi:10.1016/j.geoderma.2012.07.025

Neutron reflectometry reveals the internal structure of organic compounds deposited on aluminum oxide

Melanie Mayes, Sindhu Jagadamma, Haile Ambaye, Loukas Petridis, Valeria Lauter

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

18 Scopus citations

Abstract

Organic carbon (OC) stabilization in soils plays a significant role in the global C cycle, therefore understanding the structure and function of the OC-soil mineral interface is of high importance. To study the interface, films of simple OC compounds and natural organic matter (NOM) were deposited onto a soil mineral analogue (Al₂O₃) using spin coating and were exposed to humidity. The thickness, density and structure of the films were studied using a depth-sensitive, nano-scale technique of neutron reflectometry. A single homogenous layer was observed when NOM and glucose (GL) were adsorbed onto Al₂O₃. However, when stearic acid (SA) was added to either NOM or GL, separate layers attributed to SA and either NOM or GL were detected. The formation of distinct, immiscible layers is due to insolubility of SA with NOM and GL. In contrast, GL and NOM are both water-soluble, and therefore soluble with each other, forming a homogenous layer on the mineral surface. Our results suggest that the extent of complex layering formed on the OC-mineral interface may depend on the relative solubility of the compounds.

Original language	English
Pages (from-to)	182-188
Number of pages	7
Journal	Geoderma
Volume	192
Issue number	1
DOIs	https://doi.org/10.1016/j.geoderma.2012.07.025
State	Published - 2013

Funding

We thank Ilia Ivanov and Michael Kilbey at the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory (ORNL) for their help with sample preparation, and CNMS for access to facilities via a rapid access proposal. We acknowledge two anonymous reviewers whose suggestions significantly improved the manuscript. This project is funded by the ORNL Laboratory Research and Development Program (LDRD) . Research at the ORNL Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy . ORNL is managed by UT–Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. Department of Energy.

Keywords

Adsorption
Neutron reflectivity
Organic carbon
Organo-mineral interface
Reflectometry
Soil mineral

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10.1016/j.geoderma.2012.07.025

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abstract = "Organic carbon (OC) stabilization in soils plays a significant role in the global C cycle, therefore understanding the structure and function of the OC-soil mineral interface is of high importance. To study the interface, films of simple OC compounds and natural organic matter (NOM) were deposited onto a soil mineral analogue (Al2O3) using spin coating and were exposed to humidity. The thickness, density and structure of the films were studied using a depth-sensitive, nano-scale technique of neutron reflectometry. A single homogenous layer was observed when NOM and glucose (GL) were adsorbed onto Al2O3. However, when stearic acid (SA) was added to either NOM or GL, separate layers attributed to SA and either NOM or GL were detected. The formation of distinct, immiscible layers is due to insolubility of SA with NOM and GL. In contrast, GL and NOM are both water-soluble, and therefore soluble with each other, forming a homogenous layer on the mineral surface. Our results suggest that the extent of complex layering formed on the OC-mineral interface may depend on the relative solubility of the compounds.",

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AU - Lauter, Valeria

PY - 2013

Y1 - 2013

N2 - Organic carbon (OC) stabilization in soils plays a significant role in the global C cycle, therefore understanding the structure and function of the OC-soil mineral interface is of high importance. To study the interface, films of simple OC compounds and natural organic matter (NOM) were deposited onto a soil mineral analogue (Al2O3) using spin coating and were exposed to humidity. The thickness, density and structure of the films were studied using a depth-sensitive, nano-scale technique of neutron reflectometry. A single homogenous layer was observed when NOM and glucose (GL) were adsorbed onto Al2O3. However, when stearic acid (SA) was added to either NOM or GL, separate layers attributed to SA and either NOM or GL were detected. The formation of distinct, immiscible layers is due to insolubility of SA with NOM and GL. In contrast, GL and NOM are both water-soluble, and therefore soluble with each other, forming a homogenous layer on the mineral surface. Our results suggest that the extent of complex layering formed on the OC-mineral interface may depend on the relative solubility of the compounds.

AB - Organic carbon (OC) stabilization in soils plays a significant role in the global C cycle, therefore understanding the structure and function of the OC-soil mineral interface is of high importance. To study the interface, films of simple OC compounds and natural organic matter (NOM) were deposited onto a soil mineral analogue (Al2O3) using spin coating and were exposed to humidity. The thickness, density and structure of the films were studied using a depth-sensitive, nano-scale technique of neutron reflectometry. A single homogenous layer was observed when NOM and glucose (GL) were adsorbed onto Al2O3. However, when stearic acid (SA) was added to either NOM or GL, separate layers attributed to SA and either NOM or GL were detected. The formation of distinct, immiscible layers is due to insolubility of SA with NOM and GL. In contrast, GL and NOM are both water-soluble, and therefore soluble with each other, forming a homogenous layer on the mineral surface. Our results suggest that the extent of complex layering formed on the OC-mineral interface may depend on the relative solubility of the compounds.

KW - Adsorption

KW - Neutron reflectivity

KW - Organic carbon

KW - Organo-mineral interface

KW - Reflectometry

KW - Soil mineral

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Neutron reflectometry reveals the internal structure of organic compounds deposited on aluminum oxide

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