Surface confined self-assembled fullerene nanoclusters: a microscopic study

Abstract

The structure of the C 60-fullerene terminated aminothiol self-assembled monolayers (SAM) generated by tethering the fullerene molecules to the surface of 11-amino-1-undecane thiol (11-AUT) SAM on gold surface was investigated by dynamic contact angle measurements, Fourier transform infrared reflection–absorption spectroscopy (FTIR-RAS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). A two-step procedure was followed consisting of the chemisorption of the amine-terminated organosulfur compound on oriented gold, followed by its reaction at the solid liquid interface with C 60 fullerenes. Covalent binding of fullerenes to these attachment layers was accessed by the above experimental techniques. IR-RAS showed several major features in the C 60 skeleton ring vibration region along with all the characteristic features of the amino thiol. With increase in carbon to sulfur ratio, appearance of C 1s shake-up satellite peak due to characteristic π–π * transition of the C 60 backbone confirmed the NH 2 binding at the 6,6 double bond of the C 60 cage. Atomic force microscopy showed smooth, homogeneous areas of the monomolecular films, covered by regular small microcrystalline grains on the fullerene-terminated monolayer surface. Possible explanations for these experimental findings are discussed.