Probing charge screening dynamics and electrochemical processes at the solid–liquid interface with electrochemical force microscopy

Abstract

The presence of mobile ions complicates the implementation of voltage-modulated scanning probe microscopy techniques such as Kelvin probe force microscopy (KPFM). Overcoming this technical hurdle, however, provides a unique opportunity to probe ion dynamics and electrochemical processes in liquid environments and the possibility to unravel the underlying mechanisms behind important processes at the solid-liquid interface, including adsorption, electron transfer and electrocatalysis. Here we describe the development and implementation of electrochemical force microscopy (EcFM) to probe local bias-and time-resolved ion dynamics and electrochemical processes at the solid-liquid interface. Using EcFM, we demonstrate contact potential difference measurements, consistent with the principles of open-loop KPFM operation. We also demonstrate that EcFM can be used to investigate charge screening mechanisms and electrochemical reactions in the probe-sample junction. We further establish EcFM as a force-based imaging mode, allowing visualization of the spatial variability of sample-dependent local electrochemical properties.

Ferroelectric or non-ferroelectric: Why so many materials exhibit “ferroelectricity” on the nanoscale

“…209,379,[404][405][406] Further broad opportunities are opened by implementation of these techniques in liquid environments. 329,[407][408][409][410] While in this case electromechanical responses of material will compete with that of polarizable liquids 411,412 , these studies will provide insight into electromchanical couplings in biological systems and open the window into electro mechanics of molecular systems, the crucial development that will allow not only "to think" but also "to act" on the nanoscale. A voltage V (which can have both DC and AC components) is applied to the tip which is in contact with the sample.…”

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

“…9 The DCcomponent of the bias voltage is then readjusted by a controller so that it matches the local surface potential. Because of this DC-voltage, conventional KFM measurements can only be performed in a non-conductive, non-polar medium (air, vacuum, non-conductive liquids), 10 which is not the "natural" environment of, for example, biomolecules.…”

Band excitation Kelvin probe force microscopy utilizing photothermal excitation

“…29 Furthermore, it is likely that this approach can be extended to liquid environments in the form of electrochemical force microscopy, while avoiding AC induced electrochemistry in liquid present in the existing approach. 19 …”

“…KPFM has been particularly useful for characterizing materials and devices ranging from metals, 1 semiconductors, 8,9 and ferroelectrics, 10,11 to self-assembled monolayers, 12 polymers, 13 and biomolecules. 14,15 The continued success of KPFM necessitates both the advancement of the technique in terms of accuracy and resolution 16,17 across all imaging environments, 18,19 as well as improved capabilities to distinguish and correlate different electronic parameters (i.e., dielectric properties, [20][21][22][23] dissipation 24,25 ) beyond that currently attainable with conventional KPFM.…”