QUALITATIVE ADSORPTION MEASUREMENTS WITH AN ATOMIC-FORCE MICROSCOPE

A simple method for the qualitative measurement of adsorption of solut ion species onto silicon nitride atomic force microscope cantilevers i s presented. In this method, the change in resonant frequency of the c antilever, resulting from the added mass of the adsorbate, is measured as a function of time during the adsorption process. Results from the adsorption of copper(II) species and CTAB from aqueous solutions are presented. Cu(II) was seen to attain maximum coverage in a matter of m inutes, while the adsorption of CTAB was beyond the resolution of the technique. Force measurements taken between the cantilever tip and a g lass substrate during the adsorption process provide evidence that the change in cantilever frequency is a result of the adsorbate mass and is not just the result of any small viscosity differences.