Template-based layer-by-layer assembly


Robert E. Cohen, Department of Chemical Engineering, Massachusetts Institute of Technology, MA
Maintaining a focus on the assembly of weak polyelectrolytes has enabled the Rubner/Cohen L-b-L collaboration at MIT to generate novel ultrathin film coatings that can be used for in situ nanoparticle synthesis. Applications ranging from Rugate optical filters to antibacterial coatings have been explored. The range of synthetic schemes accessible with this nanoreactor synthesis approach has been limited in part by the nature of the binding groups that can be generated in the films without compromising the structural integrity of the PEM assemblies. For example, in previous work we have typically relied on the cation-binding capabilities of free carboxylic acid groups that are found in PAH/PAA multilayers assembled under suitable pH conditions. Recently we have addressed the possibility of generating free amines in certain PEM assemblies, thereby facilitating the binding of anionic precursors in our PEM nanoreactors. Of particular interest are negatively charged gold complexes, for example AuCl4-, that facilitate controlled in situ synthesis of gold nanoparticles. We are perfecting techniques that enable us to assemble our gold-loadable PEMs inside submicron features of various templates, thereby opening the way for exploring novel bio-molecule separation schemes, catalytic processes and the production of interesting mechanomutable heteronanostructures.