CONTACT ANGLE DETERMINATION OF NANOPARTICLES: REAL EXPERIMENTS AND COMPUTER SIMULATIONS

Abstract

Monolayers of Stöber-silica nanoparticles (ca. 40 nm diameters) at the water–air interface have been studied in a Wilhelmy film balance. Scanning angle reflectometry and molecular dynamics computer simulation have been used to assess the contact angles of the particles. Our results indicate that the traditional film balance method of contact angle determination overestimates the real contact angles even in the lower range of particle hydrophobicities.

Keywords:

• Contact angle
• Nanoparticles
• Scanning angle reflectometry
• Film balance
• Computer simulation

Acknowledgments

This work was supported by the Hungarian Scientific Research Fund (OTKA T037643).

One of a collection of papers honoring A. W. Neumann, the recipient in February 2004 of The Adhesion Society Award for Excellence in Adhesion Science, Sponsored by 3M.

Notes

l: thickness of the layer; n _eff : effective refractive index of the layer; q: immersion; h: immersion depth of spheres; d _TEM: mean particle diameter (from TEM-measurements). Contact angles from SAR- (a), from film balance measurements (b), from computer simulations (c).