AC Kelvin Probe Force Microscopy Enables Charge Mapping in Water

Thomas Hackl, Georg Schitter, Patrick Mesquida

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

Mapping charged chemical groups at the solid–liquid interface is important in many areas, ranging from colloidal systems to biomolecular interactions. However, classical methods to measure surface charges either lack spatial resolution or─like Kelvin-probe force microscopy (KPFM)─cannot be applied in aqueous solutions because a DC bias voltage is used. Here, we show that using AC Kelvin probe force microscopy (AC-KPFM), in which the DC bias is replaced with an AC voltage of sufficiently high frequency, the surface potential of spatially fixated, charged surface groups can be mapped in aqueous solution. We demonstrate this with micropatterned, functionalized alkanethiol layers which expose ionized amino- and carboxy-groups. These groups are representative of the charged groups of most biomolecules such as proteins. By adjusting the pH of the solution, the charge of the groups was reversibly altered, demonstrating the electrostatic nature of the measured signal. The influence of the electric double layer (EDL) on the measurement is discussed, and we, furthermore, show how charged, micropatterned layers can be used to spatially direct the deposition of nanoparticles of opposite charge.
Original languageEnglish
Pages (from-to)17982-17990
Number of pages9
JournalACS Nano
Volume16
Issue number11
Early online date10 Oct 2022
DOIs
Publication statusPublished - 22 Nov 2022

Keywords

  • General Physics and Astronomy
  • General Engineering
  • General Materials Science

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