AFM-Assisted Fabrication of Thiol SAM Pattern with Alternating Quantified Surface Potential

Abstract: Thiol self assembled monolayers (SAMs) are widely used in many nano- and bio-technology applications. We report a new approach to create and characterize a thiol SAMs micropattern with alternating charges on a flat goldcoated substrate using atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). We produced SAMs patterns made of alternating positively charged, negatively charged, and hydrophobic terminated thiols by an automated AFM assisted manipulation, or nanografting. We show that these thiol patterns possess only small topographical differences as revealed by AFM, and distinguished differences in surface potential (20 to 50 mV), revealed by KPFM. The pattern can be helpful in the development of biosensor technologies, specifically for selective binding of biomolecules based on charge and hydrophobicity, and serve as a model for creating surfaces with quantified alternating surface potential distribution.