Submicrometer structure of surface-chemical gradients prepared by a two-step immersion method

Lateral force microscopy and microdroplet density measurements have been used to examine the microstructure of surface-chemical gradients of thiols on gold, prepared by a two-step immersion method. A single-component coverage gradient, generated by gradual immersion of a gold surface into a solution of a single thiol, yielded islands of approximately 25 nm in diameter at the end that had only been briefly immersed, whereas an increasingly continuous film was formed along the gradient. After saturation with a second thiol with a different end group, the structure generated during the initial immersion step was found to persist.