44506-G5
High-Pressure Scanning Tunneling Microscopy for In-Situ Studies of Catalysts
Accomplishments: In the two years of this grant being in place we have published a total of 3 papers. In one article (Scanning) we were able to address many of the challenges of imaging in a high pressure environment. This paper showed that STM images collected at high pressure may induce various artifacts not normally observed at low pressure. In addition, the tip on the microscope may also contribute to the catalytic process.
We have also been working on methodology to pattern catalysts on the nanoscale which could be used in the scanning tunneling microscope. We elected to used dip-pen nanolithography which has the resolution, and capability, to pattern catalytic metals on sub-100 nm length scales. Although we have not been able to pattern functional arrays of metal nanoparticles, we did discover some rich chemistry and physics to extend the dip-pen nanolithography capability. We continue to try and pattern metals on the nanoscale which can be observed in the STM.
Challenges: One of the primary challenges that we have had to address is the harsh environment within the high pressure scanning tunneling microscope. The coarse approach mechanism was adversely affected by the high pressure/temperature environment and needed to be replaced. Unfortunately, the company that produced the coarse approach mechanism (Burleigh) has recently dissolved and no longer produces the Inchworm coarse approach. The last 12 months have been focused on a new coarse approach which is simple and less costly than the Burleigh. Our new design is based on inertial drivers and we expect the STM to be operational in January 2009. A picture can be supplied on the current STM which is working in air.
Students: The main student attached to this project is Genxin Zhang. He joined my group in the summer of 2006 after notification of this award. He is expected to graduate in 2010 and is well on track publishing a paper in his first year. Omkar Nafday worked part time on this project. His main focus was on energetic materials. However, his skills fit in well for the patterning of metals using dip-pen nanolithography and was able to publish 2 papers related to the project. He joined the group in 2004 and graduated with his PhD in the Summer of 2008.
Future: This project has been extremely challenging in the past 12 months. The cost of constructing the equipment through contract machining far exceeded the budget. Therefore, the student has been required to do this work himself. In addition, Nafday has graduated and the student to replace him has not been able to obtain a visa. Therefore, we have requested a no-cost extension.
