Infrared spectroscopic investigation of chemisorption on chemically synthesized aluminum nitride nanopowders with 2-pyrrolidinones

The chemical nature of a nanoparticle surface is of crucial importance in controlling the interparticle forces during powder processing. As a continuation of a FT-IR spectroscopy study on the surface chemical structure of the chemically synthesized aluminum nitride (AW) nanopowders, the adsorption of two representative cyclic amides, i.e., N-methyl-2-pyrroldinone (NMP) and 2-pyrrolidinone (NHP), have been investigated Upon adsorption of these cyclic amides, strong hydrogen bonding between the amide carbonyl oxygen and the surface hydroxyl groups was evident. The unusual thermal stability for the hydrogen bonding observed with NMP was explained as being due to the enhancement by secondary interactions between the NMP amide carbonyl group and the surface Lewis acidic sites, such as Al3+. With the adsorption of NHP at room temperature, besides the formation of strong hydrogen bonding, a striking 100 cm(-1) shift to higher wavenumbers was observed for both the carbonyl and amide C-N stretching bands. This has been interpreted as the formation of complex coordination between the amide nitrogen and the surface acidic sites. The amide N-coordinated complex plus the carbonyl O-coordinated hydrogen bonding promote a synergistic effect for strengthening the NHP adsorption on the AIN surface.