Atomic force microscopy (AFM) imaging of isolated submicron dodecyltrichlorosilane coated silica spheres, immobilized at the liquid polystyrene- (PS-) air interface at the PS glass transition temperature, Tg , allows for determination of the contact angle θ versus particle radius R . At Tg , all θ versus R measurements are well described by the modified Young’s equation for a line tension τ=0.93 nN . The AFM measurements are also consistent with a minimum contact angle θmin and minimum radius Rmin , below which single isolated silica spheres cannot exist at the PS-air interface.
McBride, S. P.; Law, B. M. Influence of line tension on spherical colloidal particles at liquid-vapor interfaces. Phys. Rev. Lett. 2012, 109, 196101, DOI: 10.1103/PhysRevLett.109.196101