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 gold-coated 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 (20-50 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.

A simulation study on the thermal and wetting behavior of alkane thiol SAM on gold (111) surface

“…The physicochemical properties of functionalized gold surface can be tailored by varying the chain length, terminal functional group and chemical composition of capping chains. The molecular assemblies of SAM of thiol on the coinage metal surfaces have potential applications in protective surface coatings, surface chemistry, molecular electronics, lubricants, nanolithography, sensors, bio-materials, medical implants and pharmacology due to their ordered arrangement, controllable properties, bio-compatibility, stability, selectivity and sensibility [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Alkane thiols form well-packed, stable and ordered SAM on the gold surface due to the spontaneous formation of strong gold sulfur bonds and the van der Waals interactions between the adjacent thiol chains [19,20].…”

Molecular Perturbation Effects in AFM-Based Tip-Enhanced Raman Spectroscopy: Contact versus Tapping Mode

“…The Cl-NBT SAM used in this study produces a strong TERS signal 27 however, it is also deformable 28 making it a good model system for the investigation of the probe-sample interaction. An AFM topography image of the Cl-NBT SAM is shown in Figure 2 a, which shows a smooth topography with RMS roughness of 0.6 nm.…”

Surface Potential Analysis of Nanoscale Biomaterials and Devices Using Kelvin Probe Force Microscopy

“…Furthermore, how the surface potential of individual molecules is substantially related to their electrostatic force and binding affinity is still unclear. KPFM has emerged as a remarkable tool for monitoring a variety of interactions between ligands and receptors, of biomolecules on nanomaterial surfaces by measuring their surface potential changes [87,90,91]. The following paragraphs review some examples in regard to investigations of single-molecular recognition and bimolecular interactions via KPFM techniques.…”