pubs.acs.org/Langmuir © 2009 American Chemical Society
Capping and Passivation of Aluminum Nanoparticles Using Alkyl-Substituted Epoxides Stephen W. Chung,† Elena A. Guliants,‡ Christopher E. Bunker,*,§ Douglas W. Hammerstroem,† Yong Deng,† Mark A. Burgers,† Paul A. Jelliss,*,† and Steven W. Buckner*,† † Saint Louis University, Department of Chemistry, 3501 Laclede Avenue, St. Louis, Missouri 63103, Department of Electrical and Computer Engineering, University of Dayton Research Institute, Dayton, Ohio 45469, and §Air Force Research Laboratory, Propulsion Directorate, Wright-Patterson Air Force Base, Ohio 45433 ‡
Received May 21, 2009. Revised Manuscript Received June 26, 2009 We report here on the synthesis and passivation of small (20-30 nm) aluminum nanoparticles using alkyl-substituted epoxides as capping agents. FTIR and 13C NMR spectroscopy indicate that the epoxides polymerize to form a polyether cap on the surfaces of the aluminum nanoparticles. Nanoparticles capped with epoxyhexane and epoxydodecane are stable in air, but particles capped with epoxyisobutane are pyrophoric. TEM images show spherical Al particles. Powder X-ray diffraction shows the presence of crystalline Al. Titrimetric analysis of the core-shell nanostructures in air reveals that 96% of the total aluminum present is active (unoxidized) aluminum.
Introduction Aluminum nanostructures are valuable for many energyrelated applications. These applications stem from aluminum’s low atomic number, low density, high abundance, low cost, and three-electron reduction and high redox potential. Micrometersized aluminum particles have long been used in thermite reactions, as propellants for rockets, in magnetohydrodynamic generators, and in other applications. Aluminum’s advantage over comparable organic solids as propellants is its high energy density. In addition to the long history of aluminum as a solid propellant, it has also recently been discussed as an additive to liquid fuels. Phelan and co-workers recently demonstrated that nanoscale aluminum increases the ignition probability of diesel fuels.1 Furthermore, nanoaluminum and nanoalanates are being considered as hydrogen storage materials.2 Although there are many applications for nanoscale aluminum materials, there are challenges with producing air-stable nanoscale aluminum structures with small diameters (
