Resolving
Fine Structures of the Electric Double Layer
of Electrochemical Interfaces in Ionic Liquids with an AFM Tip Modification
Strategy
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Abstract
We report enhanced force detection
selectivity based on Coulombic
interactions through AFM tip modification for probing fine structures
of the electric double layer (EDL) in ionic liquids. When AFM tips
anchored with alkylthiol molecular layers having end groups with different
charge states (e.g., −CH<sub>3</sub>, −COO<sup>–</sup>, and −NH<sub>3</sub><sup>+</sup>) are employed, Coulombic
interactions between the tip and a specified layering structure are
intensified or diminished depending on the polarities of the tip and
the layering species. Systematic potential-dependent measurements
of force curves with careful inspection of layered features and thickness
analysis allows the fine structure of the EDL at the Au(111)–OMIPF<sub>6</sub> interface to be resolved at the subionic level. The enhanced
force detection selectivity provides a basis for thoroughly understanding
the EDL in ionic liquids