We report the preparation of in-plane density gradients of amino-terminated molecules and gold particles through derivatization of laterally varying thickness gradients of poly(acrylic acid) (PAA) or poly(acrylamide) (PAAm) films. PAA and PAAm gradients were formed by Zn(II)-catalyzed electropolymerization of acrylic acid (AA) or acrylamide (AAm) in the presence of an in-plane electrochemical potential gradient applied to Au or indium-tin-oxide (ITO) working electrodes. PAA thickness gradients were converted into density gradients of fluorocarbons or biocompatible groups by derivatizing with NH2CH2(CF2)(6)CF3 or an Arg-Gly-Asp (RGD)-containing peptide, respectively. X-ray photoelectron spectroscopy (XPS) and XPS imaging were used to characterize the modified PAA gradients. Transition regions as narrow as 104 mu m were achieved for fluorocarbon gradients. PAAm gradients were treated with gold particles to form a density gradient of gold particles. Surface plasmon resonance imaging and scanning electron microscopy (SEM) as well as UV-visible absorption measurements were used to characterize the gold particle density gradients. It is likely that the gold particles were attached both on the surface and inside the PAAm film.