| AVS 55th International Symposium & Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS2+NC-ThM |
| Session: | Catalysis on Nanoclusters |
| Presenter: | D. Menzel, Fritz-Haber-Institut der Max-Planck-Gesellschaft and Technical University Muenchen, Germany |
| Authors: | D. Mulugeta, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany K.H. Kim, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany K. Watanabe, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany D. Menzel, Fritz-Haber-Institut der Max-Planck-Gesellschaft and Technical University Muenchen, Germany H.-J. Freund, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany |
| Correspondent: | Click to Email |
The unique electronic and optical properties of metal nanoparticles (MNPs) are caused by their small size compared to typical interaction lengths with photons and electrons, the confinement of excitations in them, and their specific excitations, in particular the Mie plasmon which causes strong field enhancement.1 Modifications of photochemical reactions occurring on them are expected. We have investigated the photochemical reactions in (NO)2 layers on AgNPs deposited on alumina films, using ns laser pulses off and on the plasmon resonance, and for varied NP size. Photoexcitation of (NO)2 leads to photodesorption of NO as well as photochemical conversion to N2O and to chemisorbed NO. Results include total removal and conversion efficiencies, desorbed species and their cross sections, and mean translational energies of photodesorbed NO. Excitation in the plasmon resonance strongly enhances yields and cross sections, compared to off-resonance excitation and to Ag(111) surfaces. The similar (nonthermal) translational energies of desorbed NO in all cases indicate a common mechanism believed to proceed via temporarily trapped hot electrons forming transient negative ions (TNI) which leads to desorption and reaction. Recent results obtained for variable sizes of the AgNP (2 - 10 nm) have shown that characteristics of both thermal and photochemical reactions depend on size. To explain these results, the influences of the size dependences of a number of excitation and decay processes, based on knowledge of the photophysics of the AgNPs, will be discussed. Time permitting, the changes introduced by the use of fs laser pulses will also be presented. These examples show some important consequences of the small dimensions of NMPs, size-dependent confinement effects, and influences of plasmon excitations.
1K. Watanabe, D. Menzel, N. Nilius, and H.-J. Freund, Chem. Rev. 106 (2006) 4301.