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Kelvin-probe force microscopy of the pH-dependent charge of functional groups

Research output: Contribution to journalArticle

Original languageEnglish
Article number233702
Number of pages4
JournalAPPLIED PHYSICS LETTERS
Volume108
Issue number23
Early online date8 Jun 2016
DOIs
Accepted/In press21 May 2016
E-pub ahead of print8 Jun 2016

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Abstract

Kelvin-probe Force Microscopy (KFM) is an established method to map surface potentials or surface charges at high, spatial resolution. However, KFM does not work in water, which restricts its applicability considerably, especially when considering common, functional chemical groups in biophysics such as amine or carboxy groups, whose charge depends on pH. Here, we demonstrate that the KFM signal of such groups taken in air after exposure to water correlates qualitatively with their expected charge in water for a wide range of pH values. The correlation was tested with microcontact-printed thiols exposing amine and carboxy groups. Furthermore, it was shown that collagen fibrils, as an example of a biological material, exhibit a particular, pH-sensitive surface charge pattern, which could be caused by the particular arrangement of ionizable residues on the collagen fibril surface.

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