Abstract

It has been suggested that attractive forces at hydrophobic surfaces arise from the cavitation of nanobubbles in the interfacial water region eventually leading to film instability and rupture. These phenomena may be the basis for bubble attachment at a hydrophobic surface and the flotation of hydrophobic particles. Now, for the first time the accommodation of gas by interfacial water at a hydrophobic silicon surface has been demonstrated by in-situ FTIR/IRS measurements for the butane/silicon system Such gas accommodation does nor occur at a hydrophilic silicon surface. The origin and long-range nature of hydrophobic interactions are discussed based on these spectroscopic measurements which support the presence of gas nanobubbles/cavities at hydrophobic surfaces. Cavitation of these nanobubbles may explain the very strong long-range attractive forces which have been measured between macroscopic hydrophobic surfaces in some systems.