Aug 19, 2008
Gold nanocones prove a point
Scientists based in Korea have transfered printed gold nanocones on to ITO-coated glass to create a field emission display with a turn-on field of just 3.3 V/µm. This value is comparable to devices based on Mo oxide nanotubes (3.5 V/µm) and Mo hollow pillars (4.5 V/µm), and is much lower than MgO nanotube (8.4 V/µm) or ZnO nanowire (6.0 V/µm) systems.
Although ideal for creating displays, the simple and low-cost approach should also benefit biological and medical applications.
"One of our goals is to use the printed nanostructures to fabricate biochips," Soon-min Seo of Kyungwon University's Gachon BioNano Research Institute told nanotechweb.org. "The gold patterns can be used as surface enhanced Raman scattering templates or as electrodes for detecting cells."
Step and repeat
To create their gold nanopatterns, the researchers deposit the metal on to a polyurethaneacrylate (PUA) mould. PUA is used because it is rigid enough to withstand the external pressure required for transfer printing.
To prevent cracks from occurring in the nanostructures, it is important that the mould is filled evenly. A deposition rate of 0.5 nm/s was found to be satisfactory by the team.
Once the gold layer has been applied, the filled mould is placed into a press containing the target substrate (in this case, ITO-coated glass covered with a self-assembled monolayer, which helps bond the gold to the substrate). The apparatus heats the mould to 120 °C and applies a pressure of 80 kg/cm2 for 10 mins.
After cooling, the mould is removed and can be reused, which allows Seo and his colleagues to print over a large area using a step and repeat approach.
The group, which also includes researchers from Seoul National University's School of Chemical and Biological Engineering, presented their work in Nanotechnology.
About the team
Tae-il Kim, Ju-Hyung Kim are graduate students in H H Lee’s research group in the School of Chemical and Biological engineering at Seoul National University. Soon-min Seo and Sang Jun Son are based at Kyungwon University's college of BioNano Technology.
About the author
James Tyrrell is editor of nanotechweb.org.