Nov 21, 2012
Laser pulses and nanospheres create mesoporous membranes
Researchers from the French National Research Center (CNRS), the Italian National Research Institute for Metrology (INRIM) and the University of East Piemonte, Italy, are studying the use of laser pulses and self-assembled monolayers of silica nanospheres for fabricating mesoporous membranes. To examine the approach in more detail, the group has prepared different samples of silica particles ranging from 261 to 725 nm in diameter, but each with a narrow size distribution.
In the work, a statistical approach coupled with the use of tailor-made spheres allows the precision and reproducibility of the laser nanomachining to be related to the size dispersion of the nanospheres.
To produce the nanostructured membranes, the team first prepares monodisperse silica nanospheres and then assembles monolayers of the material on target substrates. Next using a nanosecond laser pulse, the group fabricates beautifully ordered mesoporous membranes thanks to the interaction of the light with the nanospheres. During this nanodrilling process, the ablated products eject the spheres by momentum transfer and simultaneously clean the substrate of any residual contaminant.
In the work, the researchers focused on the optical near-field aspects associated with preparing high-precision membranes. By statistical analysis, the scientists demonstrated that the concept of optical Mie resonances can lead to strong local field changes for sphere sizes in the range 550–725 nm. In this range, the data indicate that an extremely narrow size distribution of nanospheres (σ <<25 nm) is required to produce well defined and defect-free membranes in the full range of operative laser fluences.
Full details can be found in the journal Nanotechnology.
About the author
David Grojo is a permanent scientist at the French National Research Center (CNRS). His research in the Laser, Plasma and Photonic Processes Laboratory concentrates on the specificity of laser-matter interactions at extremely small length and time scales. Such work opens routes to the laser tailoring of nanomaterials.