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| - Determination of Energy Barriers for IntermolecularInteractions by Variable Temperature Dynamic ForceSpectroscopy
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| - Intermolecular interactions in chemistry and biology are governed by complex potential energy surfaces.Despite recent advances in nanoscale interaction force measurements, determination of the potentialenergy barriers remains difficult. We present a simple force microscopy technique that can extract tip−sample interaction potential depth and width from the pull-off force measurements. We show thatdetermination of the thermodynamic parameters for the interaction requires measuring the pull-off forceas a function of the loading rate and temperature. We apply this variable-temperature dynamic forcespectroscopy technique to determine thermodynamic parameters for the interactions between a siliconnitride tip and a mica surface and for the interactions of tip and surface terminated with carboxylic acidfunctionalities in ethanol. For both cases, we observed that pull-off force increases logarithmically as afunction of loading speed, with the rate of the increase determined by the width of the interaction potential.Analysis of the temperature dependence of the interaction forces provides estimates for the enthalpy andentropy of the interactions and reveals an important role of solvation effects in these systems.
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