Surface confined self-assembled fullerene nanoclusters: a microscopic study

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. IRRAS 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 Is shake-up satellite peak due to characteristic pi-pi* transition of the C-60 backbone confirmed the -NH2 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. (c) 2004 Elsevier B.V. All rights reserved.