| AVS 66th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology Division | Friday Sessions |
| Session NS+AS-FrM |
| Session: | Electron-Beam Promoted Nanoscience |
| Presenter: | Canhui Wang, UMD/NIST |
| Authors: | C. Wang, UMD/NIST W.-C. Yang, UMD/NIST A. Bruma, UMD/NIST R. Sharma, National Institute of Sandards and Technology (NIST) |
| Correspondent: | Click to Email |
Excitation of localized surface plasmon (LSP) resonance on metal nanoparticles has been shown to overcome the reduced the energy barrier for photochemical reactions, even allowing certain reactions to occur at room temperature. (1-2) Understanding the reactions promoted by LSP resonance at the nanoscale is important for designing efficient photocatalytic systems for a wide range of energy and environmental applications. However, many important questions related to this type of reaction process remain unclear due to the complexity of the reaction kinetics, and lack of spatial resolution available with optical methods. Details such as the location of gas adsorption sites, how the energy is being absorbed and released, and how those details are correlated to the structure of the catalyst nanoparticles, remain elusive and are only hinted by theoretical calculations.
Here we use in-situ electron microscopy and combine an ensemble of data acquisition and processing techniques to characterize LSP-initiated chemical reactions at high spatial resolution using an aberration-corrected environmental scanning transmission electron microscope. Electron energy loss spectrum (EELS) imaging is used to acquire both elemental and LSP resonance maps from the same area that contains the plasmonic nanoparticles. The elemental maps allow us to locate the gas adsorption sites, the elemental distribution of the reactants and plasmonic nanostructures, as well as the spatial distribution of the solid reaction products, with nanometer resolution. The LSP-EELS maps provide insight into how the energy is channeled from the fast electron to the plasmonic nanostructure. Localized reactant consumption (mass loss) distribution is mapped in terms of thickness changes by subtracting the thickness map acquired after the reaction from the thickness map acquired before the reaction. This allows us to pinpoint the reaction hotspot near the nanoparticle surface. The LSP induced electric field distribution near the nanoparticle surface is simulated using the metallic nanoparticles boundary element method(MNBPEM) (3) and compared with the reactant mass loss map. These techniques allow us to explore and study previously unknown LSP initiated reactions with unprecedented details on the sub-particle level. (4) The results improved the understanding of the dynamics of LSP initiated reactions and give insights into nanoparticle engineering for optimizing reaction efficiency.
1. Mukherjee S, et al. (2012) Nano letters 13(1):240-247.
2. Thomann I, et al. (2011) Nano letters 11(8):3440-3446.
3. Waxenegger. J, et al. (2015) Comp. Phys. Commun. 193, 138.
4. Yang, W.C.D, et al. (2019) Nature Mater. 1.