pH-responsive octylamine coupling modification of carboxylated aluminium oxide surfaces

The formation of a pH-sensitive coupling layer, through both physisorption and chemisorption, provides a responsive surface that can be assembled and disassembled in relation to external stimuli. Contact angle measurements, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and Fourier transform IR-attenuated reflectance spectroscopy (FTIR-ATR) have been used to characterize a series of bi-functionalized self-assembled monolayers (SAMs) grown on aluminium oxide wafers/nanoparticles and investigate the reaction nature of pH-responsive coupling layer (octylamine) with the SAMs. Contact angle, XPS, and AFM analyses indicate that the surface of native aluminium oxide was covered considerably as the contact angle of the surfaces decreased, carbon atomic % and roughness of the surfaces increased.