A simple and versatile method to evaluate the interactions between four different phthalocyanine dyes and carbon nanotube surfaces using silica spheres coated with ultrathin-layers of single-walled carbon nanotubes (SWNTs) is described. The well-isolated SWNTs immobilized on the silica spheres acted as effective adsorption sites for the dye molecules, and the interactions between them were evaluated by measuring the absorbance change in the supernatant solutions after simple mixing.