Copper nanoparticles in AOT "revisited"-direct micelles versus reverse micelles

For the first time, direct micelles of the surfactant Aerosol-OT (AOT) have been used to synthesize copper nanoparticles. The synthesized nanoparticles are spherical and highly crystalline with diameter 5-10 nm. They show the prominent surface plasmon resonance typical of copper nanoparticles. AOT plays a dual role-initially it provides a site for initiation of reduction and subsequently it acts as a stabilizer for controlled nucleation. For comparison, copper nanoparticles were also synthesized in the well known AOT reverse micelles. Small sized nanoparticles (diameter < 4 nm) were formed. Unlike previous works on copper nanoparticle synthesis in reverse micelles using substituted AOT i.e Cu(AOT)(2), in this work unsubstituted Na-AOT was used. This minimizes the adverse effects on stability and shape which arise due to surfactant functionalization. Finally, the most important finding of the present work is that AOT direct micelles are better substrates than reverse micelles for synthesis of stable, spherical and crystalline copper nanoparticles with distinct surface plasmon resonance spectra. (C) 2016 Elsevier B.V. All rights reserved.