Potential active sites for catalysis revealed by in situ measurement of localized surface plasmon resonance in metal nanoparticles

P.A. Lin, J.M. Kohoutek, H. Lezec, R. Sharma
National Institute of Standards and Technology, US

Keywords: LSPR, nanoparticle, catalysis, EELS, FDTD

Summary:

Nanoparticles (NPs) have been widely used for nanosensing because their LSPR is highly sensitive the environment. We have employed electron energy loss spectroscopy (EELS) to collect localized surface plasmon resonance (LSPR) in Au NPs under gaseous condition (i.e. H2, CO) in environmental transmission electron microscope (ETEM). The great advantage of this technique is the nanometer spatial resolution, which is capable to identify the potential active reaction site on an individual NP surface. We have observed when H2 is introduced, a LSPR shift on the corner of a triangular Au NP, but no shift on the side of a triangular Au NP. Moreover, experimental results has been simulated by Finite Difference Time Domain (FDTD)method. Therefore, we can conclude that the H2 adsorption is localized only at the corner of the Au NP. As gas absorption is the first step for a catalytic reaction to proceed, it is safe to assume that such information can be obtained from the LSPR energy shifts. We have employed these techniques to interrogate the adsorption sites for other gasses, including CO, and a detailed discussion of our findings will be presented.