Nanostructures formed via the sonochemical method have been the subject of much scientific interest. The sonochemical method has produced a number of valuable systems, including luminescent nanoparticles, nanoscale catalysts, and reactive nanoparticles with protective coatings. Reactive metal nanoparticles have also become an attractive area of research for their applications to energetic materials, fuel additives, and propellants. In this work, the sonochemical method was employed to synthesize Al0 nanostructures coated with a carboxylic acid shell. The resulting nanostructures were studied in terms of their crystal morphology, chemical composition, and reactivity. The nanostructures and their agglomerates were identified as zero-valent face-centered cubic Al by XRD analysis. Analysis of the reactivity of these particles suggests protection by the carboxylic acid coating. The results of this study will be further discussed within the context of the sonochemical mechanism (sonochemical vs. thermal decomposition pathways) and the potential application these nanostructures have as novel energetic materials.