AFM STUDY OF THE EVOLUTION OF DOUBLE LAYER ON SiO2 SURFACE AND SELF-ASSEMBLY MONOLAYER INDUCED BY THE POLARIZATION WITH DC VOLTAGES

AFM was used to study the evolution of double layer on SiO2 surface and self-assembly monolayer induced by the polarization with DC voltages. Approach force curves were recorded when external DC voltages were applied between solution and SiO2 or aminopropyltriethoxysilane (APTES) modified SiO2 surfaces in electrolyte solution. The results showed that the reversing of tip–surface interaction forces between attraction and repulsion could take place only by adjusting DC voltages. It is very useful for biotechnology because the adsorption of biomolecules could be controllable by DC voltages. A model was proposed to explain the behavior of double layer under DC voltages.AFM, double layer, force curves, self-assembly monolayer