Calcite surfaces modified with carboxylic acids (C2 to C18): layer organization, wettability, and stability properties

09 May 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


A fundamental understanding of the interactions between mineral surfaces and amphiphilic surface modification agents is needed for better control over production and uses of mineral fillers. Here, we controlled the carboxylic acid layer formation conditions on calcite surfaces with high precision via vapour deposition. The properties of the resulting carboxylic acid layers were analyzed using surface sensitive techniques such as atomic force microscopy (AFM), contact angle measurements, angle resolved X-ray photoelectron spectroscopy (XPS) and vibrational sum-frequency spectroscopy. A low wettability was achieved with long hydrocarbon chain carboxylic acids, such as stearic acid. The stearic acid layer formed by vapour deposition is initially patchy, but with increasing vapour exposure time, the patches grow and condense into a homogeneous layer with a thickness close to that expected for a monolayer as evaluated by AFM and XPS. The build-up process of the layer occurs more rapidly at higher temperatures due to the higher vapour pressure. The stability of the deposited fatty acid layer in the presence of a water droplet increases with chain length and packing density in the adsorbed layer. Vibrational sum frequency spectroscopy data demonstrate that the stearic acid monolayers on calcite have their alkyl chains in an all-trans conformation and are anisotropically distributed on the plane of the surface, forming epitaxial monolayers. The vibrational spectra also show that the stearic acid molecules interact with the calcite surface through the carboxylic acid headgroup in both its protonated and deprotonated forms. The results presented provide new molecular insights into the properties of adsorbed carboxylic acid layers on calcite.


fatty acid
sum frequency spectroscopy
contact angle
molecular structure

Supplementary materials

Supporting Information
The document includes the vapour pressure and aqueous solubility of the carboxylic acids used in the study, complementary AFM deformation and morphology images of carboxylic acid modified calcite surfaces, detailed description of the procedure used to determine adsorption and layer thickness using XPS, and finally, additional VSFS spectra and corresponding fitting parameters.


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.