Atomic force microscopy images of MgO(100) and TiO2(110) under water and aqueous aromatic molecule solutions

In situ atomic force microscopy (AFM) observations at atomic level of the surface structures of MgO(100) and TiO2(110) under water and aqueous aromatic molecule solutions are reported. Under deionized water the MgO(100) surface showed slow dissolution initiated by pitting, whereas the TiO2(110) surface did not show any surface dissolution. At atomic level, MgO(100) gave AFM images of very low contrast, indicating very small force variations on its surface under aqueous environment. TiO2(110) showed images with rows whose intervals correspond to those of Ti4+ rows. Addition of an aqueous ammonium benzoate solution onto MgO(100) surface produced structures attributable to adsorbed molecule overlayers, similar to the ones observed on zeolite surfaces. The TiO2(110) surface under aqueous aromatic solutions gave images similar to those obtained under deionized water, indicating no or very slow adsorption of these molecules on the surface. (C) 1997 Elsevier Science B.V.