CHARACTERIZATION AND SURFACE-CHARGE MEASUREMENT OF SELF-ASSEMBLED CDSNANOPARTICLE FILMS

The self-assembly of CdS semiconductor nanocrystals (Q-CdS) as well-de fined monolayer and multilayer films on glass, indium tin oxide, and g old surfaces was carried out. These were characterized by ultraviolet- visible spectroscopy, ellipsometry, and scanning tunneling microscopy, The adsorption of the polymeric anion hexametaphosphate (HMP) on the Q-CdS particle surface produced a negative surface charge. The diffuse double-layer interaction forces between a silica probe and the Q-CdS/ HMP particle film-covered gold substrate immersed in aqueous solutions were measured using an atomic force microscope. The surface charge an d electrostatic potential of Q-CdS particles were obtained by theoreti cal fits of the force data to solutions of the complete nonlinear Pois son-Boltzmann equation with a knowledge of the silica probe surface po tential.