Chemical force microscopy of aminomodified AFM tips and substrates

Alex Limansky

Mechnikov Institute of Microbiology and Immunology of Academy of Medical Sciences,
Pushkinskaya st. 14, Kharkov, 61057, Ukraine

Institute of Experimental and Clinical Veterinary Medicine,
83 Pushkinskaya st., Kharkov 61023, Ukraine

Force measurements of atomic force microscopy (AFM) were used to measure adhe-sion forces between modified and unmodified probes and substrates in aqueous so-lutions at different ionic strength(I) and pH. We examined adhesive forces bet-ween four pairs of surfaces: unmodified silicon nitride tip - freshly cleaved mica, aminomodified tip - mica, aminomodified mica - tip, aminomodified tip - aminomodified mica. AFM tips and mica have been modified with 3-aminopropyltri-ethoxy silane(AP) vapour and functionalized with aminogroups. Adhesion force va-lues have been decreased in direction from I =10 mM to I = 100 mM and from I = 100 mM to pH 11.2 as for pair tip - AP-mica as for pair AP-tip - mica. Stability of AP-mica surface was estimated by AFM imaging of linear phage lambda DNA and supercoiled plasmid DNA pUC8 immobilized at AP-mica.