Application of scanning tunneling and atomic force microscopies to the characterization of microporous and mesoporous materials

In the last 20 years, the development of scanning probe microscopies (SPM), and particularly of scanning tunneling and atomic force microscopies (STM/AFM), has made it possible to visualize and study surfaces with unpreceded resolution; reaching the atomic level in many cases. Accordingly, a great number of scientific disciplines have benefited from the research opportunities afforded by these techniques. In the last decade, and despite some specific difficulties, the field of porous materials has also taken part in these advancements, incorporating STM and AFM as additional characterization tools that complement the information provided by other, well-established techniques. Here, the application of STM and AFM to the study of micro- and mesoporous materials is reviewed for the first time. The full range of materials relevant in this respect is covered, and includes inorganic solids (such as silica, alumina or zeolites), carbons (e.g., activated carbons and activated carbon fibers) and organic (especially polymeric membranes) and biological materials. Emphasis has been placed on (but not restricted to) highlighting the strengths and limitations of the two techniques in terms of pore resolution capability. Likewise, opportunities for improvements in this regard, and therefore in SPM performance on porous materials, are identified. (C) 2003 Elsevier Inc. All rights reserved.