Nov 6, 2009
Nanostructures through chaos: nanoporous films made easy
Over the last decade, nanoporous materials have become ubiquitous in sensor technologies, drug delivery, semiconductor research, catalysis and photonics, to name just a few areas. Despite their widespread use, rapid fabrication of these materials with reliable control of their properties still remains a non-trivial task. To address this issue, researchers at the University of Missouri, Columbia, US, have developed a novel technique to rapidly fabricate novel nanostructures comprising nanoparticles with embedded nanopores. Stable films with surface areas as high as 1400 m2/g and ultra-low refractive indices (as low as 1.048) have been achieved by following this method.
The simple spin-on based approach makes use of the entropic gain of functionalized nanoparticles initially dispersed in a polymer system when instantly subjected to temperatures beyond the decomposition temperature of the polymer. The random Brownian motion of the nanoparticles due to the increased thermal energy results in a fraction of the nanoparticles crosslinking with each other thereby kinetically arresting the system. This eventually leads to the formation of highly porous nanostructures with tunable properties.
The team has shown that the optical and physical properties of the films can be finely tuned as a function of the curing/calcination temperature as well as the amount of polymer loading. The group demonstrates the viability of this approach by choosing an organosilicate nanoparticle-polypropylene glycol system.
As shown in the images above, the coatings feature nanoparticles and pores with sizes less than 10 nm, which give very smooth surfaces. These systems are highly dependant on the surface properties of the substrates thereby enabling a novel approach to pattern porous and non-porous regions simply by patterning the surface energy of the substrates. Because of their easy and rapid fabrication together with their unique properties, these coatings are expected to have a major impact in biosensing, photonics and separation technologies.
The researchers presented their results in the journal Nanotechnology.
About the author
Korampally Venumadhav, PhD, is a research assistant professor at the International Center for Nano/Micro Systems and Nanotechnology, University of Missouri, Columbia (MU). His research interests are in the areas of Chem-Bio sensors through integrating nanomaterials with micro electromechanical (MEMS) systems. Shubhra Gangopadhyay, La Pierre chair professor is the director of the Center for Nano/Micro Systems and Nanotechnology at MU. Her research interests are in the areas of nanomaterial processing using top-down and bottom approaches and their integration with microchip technology.