Surface Modification of Amorphous Carbon Thin Films with 4-Aminobenzoic Acid by Electrochemical Oxidation

Abstract

Amorphous carbon (a-C) thin films are attractive materials for a wide range of applications. On the other hand, further modification of its surface can impart new features while retaining bulk characteristics. Surface modification of glassy carbon and graphite by electrochemical methods have been widely studied. However, there are relatively few reports on the surface modification of a-C thin films by electrochemical methods. The purpose of this study is to establish a method for the surface modification of a-C thin films with 4-aminobenzoic acid (4-ABA) by electrochemical oxidation and the characterization of the resulting 4-ABA-modified a-C thin films. The surface modification was performed by cyclic voltammetry (CV) in 10 mmol dm⁻³ phosphate buffer containing 4-ABA, using the a-C thin film deposited via pulsed laser deposition as a working electrode. The resulting surfaces have been studied by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy scratching. The XPS N 1s spectrum of the modified a-C surface revealed a peak at a binding energy of 399.5 eV which showed the formation of a carbon-nitrogen bond between the amino cation radical and carbon atom of the a-C thin film surface. The thickness of the modified layer formed by a single-cycle CV in a 1.0 mmol dm⁻³ solution of 4-ABA exceeded the molecular length of 4-ABA, indicating the formation of a multilayer of 4-ABA on the a-C surface.