Effect of temperature and trace water on surface forces studied by liquid AFM

Abstract

Solvation forces in confined liquids have been studied using the Atomic Force Microscope (AFM), principally the effect of temperature, tip shape and trace amounts of water in the liquid. <br><br>The effect of temperature on solvation forces have been studied in the liquids OMCTS, n-hexadecane, and n-dodecanol. Discrete solvation layers can be observed for all three liquids at all the temperatures measured (298K to 348K). However, with increasing temperature there is a significant decrease in the magnitude of the measured solvation forces and a reduction in the number of solvation oscillations which can be observed. The normalized solvation force data, F/Rtip, has also been found to differ between AFM tips of different radius of curvature (Rtip = 15nm to 100nm) with a clear trend of decreasing F/Rtip with increasing Rtip. <br><br>The effect of trace water, with the exception of the OMCTS-HOPG system where the data is inconclusive and no comment can be made, has been found to cause a decrease in the magnitude of the maximum force (Fmax) for each layer, a decrease in the number of observable jumps, and a decrease in the exponential decay length in the liquids n-hexadecane and n-dodecanol.<br>