title: Quantitative Determination and Comparison of the Surface Binding of Phosphonic Acid, Carboxylic Acid, and Catechol Ligands on TiO2 Nanoparticles.
abstract: The adsorption, desorption, co-adsorption, and exchange behavior of phosphonic acid, carboxylic acid, and catechol derivatives on the surface of titanium oxide (anatase) nanoparticles are investigated. Thermogravimetric analysis provides a facile and fast-track quantitative determination of the wet-chemical monolayer adsorption constants and grafting densities of ten adsorbates, all under neutral pH conditions. This characterization protocol allows straightforward quantification of the relevant thermodynamic data of ligand adsorption and a comparison of ligand adsorption strengths. The reported procedure is proposed as a universal tool and it should be applicable to many other colloidal metal oxide materials. Moreover, the determined values for the adsorption constants and the monolayer grafting densities provide a toolbox for the assessment of the adsorbates' behavior in desorption, exchange, and co-adsorption equilibria. This versatile evaluation procedure will help to identify optimal monolayer-surface combinations and to evaluate critical parameters, such as monolayer robustness, ligand exchange rates, or targeted mixed assembly of functionalities.
authors.affiliation: Department of Chemistry and Pharmacy, Institute of Organic Chemistry, Henkestrasse 42, 91054, Erlangen, Germany.
authors.forename: Lukas
authors.initials: L
authors.lastname: Zeininger
authors.affiliation: Department of Materials Science, Organic Materials and Devices (OMD), Martensstrasse 7, 91058, Erlangen, Germany.
authors.forename: Luis
authors.initials: L
authors.lastname: Portilla
authors.affiliation: Department of Materials Science, Organic Materials and Devices (OMD), Martensstrasse 7, 91058, Erlangen, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Halik
authors.affiliation: Department of Chemistry and Pharmacy, Institute of Organic Chemistry, Henkestrasse 42, 91054, Erlangen, Germany. andreas.hirsch@fau.de.
authors.forename: Andreas
authors.identifier: http://orcid.org/0000-0003-1458-8872
authors.initials: A
authors.lastname: Hirsch
keywords: binding strength; metal oxides; monolayers; nanoparticles; surface analysis