Interpretation of adhesion force between self-assembled monolayers measured by chemical force microscopy

Frictional Responses of Octadecyltrichlorosilane (OTS) and 1H, 1H, 2H, 2H-Perfluorooctyltrichlorosilane (FOTS) Monolayers Self-assembled on Aluminium over Six Orders of Contact Length Scale

“…By assuming that the dispersion component of the hydrated SAM is the same as that of water and acid-base components of the free energy are equal, we use the measured value of work of adhesion (from AFM pull off force measurements using functionalized tips, where the substrate SAM and the tip have the same function) to estimate the surface energy of the hydration layer. Our estimate matches well with those reported by Warszynski [32]. Knowing this energy we estimate the work of adhesion for the total interaction where either the tip or the substrate or both are hydrated.…”

“…At 5% humidity where there is insufficient water to form a capillary junction Qian et al [29] in fact show that hydrophobic/hydrophobic interaction registers a slightly higher friction and a significantly higher adhesion than what is recorded for the hydrophilic/hydrophobic interaction. Assuming that there are fragments of an adsorbed water monolayer present at our 0% humidity contact we use the method suggested by Warszynski [32] to estimate the work of adhesion when either the tip or the SAM on substrate or both have hydration layers firmly attached to it. By assuming that the dispersion component of the hydrated SAM is the same as that of water and acid-base components of the free energy are equal, we use the measured value of work of adhesion (from AFM pull off force measurements using functionalized tips, where the substrate SAM and the tip have the same function) to estimate the surface energy of the hydration layer.…”

Force measurements with the atomic force microscope: Technique, interpretation and applications

“…The jump-to-contact and the adhesion has been measured with functionalized tips also for the following systems: -NH 2 , -CH 3 , and -COOH pairs in water [361,362], -OH and -CH 3 terminated samples and tips in different liquids (water, hexadecane, perfluorodecaline, dodecane, octanol) [363], -OH, -COOH, and -CH 3 terminated samples and tips in different liquids (water, hexadecane, perfluorodecaline, dodecane, ethanol) [364], -COOH terminated tips on -NH 2 , -CH 3 terminated samples and allylamine films [365], mixed films of HS(CH 2 ) 11 OH and HS(CH 2 ) 11 CH 3 with -C 10 COOH and -C 11 CH 3 tips [366], cholesterol monohydrate in water and ethylene glycol with -COOH and CH 3 tips [367], and also several proteins and NH 2 -, CH 3 -, OH-and COOH-terminated samples in water and PBS buffer [362,368,369].…”

Chemical force microscopy: probing chemical origin of interfacial forces and adhesion

“…For OH-OH pair in octanol, the CFS gives γ SL =0.16 mJ/m 2 and 0.60 mJ/m 2 , respectively, for the two minima [59].…”