Office: Seeley G. Mudd Bldg.
The primary goal of the Moore group research program is to gain a detailed understanding of catalytic reaction mechanisms involving various metallic and non-metallic nanoparticles (NPs). To achieve this, my lab is developing a new approach called “freeze-frame” spectroscopy, which involves the use of liquid helium nanodroplets to stabilize pre- and post-reactive complexes of free NPs with reactant molecules. These complexes are then probed using infrared spectroscopy, and structural assignment is achieved based on predictions from computational studies.
Click here for more information on the "freeze-frame" effect.
CO oxidation on gold NPs
Our initial experiments are focused on understanding the catalytic oxidation of CO on gold nanoparticles. Although gold in its bulk form has little or no catalytic activity, gold nanoparticles supported on metal oxide substrates have been shown to have quite high catalytic activity for CO oxidation (as well as propylene epoxidation and other reactions), and at lower temperatures than other catalysts.(1) Much work has been done on model systems to understand the mechanism responsible for this activity; however the nature of the active site is still somewhat controversial. Our contribution will be to obtain infrared spectra of CO and O2 bound in their pre-reactive geometries on size-selected anionic and cationic gold nanoparticles. We will thus be able to address open questions such as whether or not the O2 undergoes dissociative chemisorption before the reaction occurs. Also, these experiments will provide direct information about the reaction pathway, which will us to test predictions of existing and future computational studies on these systems.
Soft landing of Metcars
A parallel line of investigation will explore using helium nanodroplets to facilitate the recovery of novel gas-phase species via soft-landing on a laboratory target. Many gas phase reactions occur under kinetic control, rather than thermodynamic control, which allows for synthesis of clusters with structures and stoichiometries that are not easily reproduced in condensed phase syntheses. A notable example is the metallocarbohedrenes, or metcars, discovered by the Castleman group at Penn State.(2) Metcars are polyhedral clusters comprised of alternating metal atoms and C2 units, which have been predicted to have gas-phase catalytic activity, for example for hydrodesulfurization reactions(3), which are important for petroleum refining. Our approach will be to dope ionic metcars into liquid helium nanodroplets, which will then be guided to a laboratory target for recovery. The efficient energy dissipation afforded by the helium droplets will serve as an energy sink, to ensure that the collision with the target deposits as little energy as possible into the metcars. The target will then be probed using electron microscopy and surface photoelectron spectroscopy to verify that the metcars have been recovered intact.
(1) M. Haruta, CATTECH 6, 102 (2002).
(2) B. C. Guo, K. P. Kerns, A. W. Castleman, Science 255, 1411 (1992).
(3) P. Liu, J. M. Lightstone, M. J. Patterson, et al., J. Phys Chem. B 110, 7449 (2006).
Analytical and spectroscopy courses.
“IR-spectroscopic characterization of intermediates in a gas-phase ion-molecule reaction: the decarbonylation of acetophenone with Co+” R.C. Dunbar, D.T. Moore, J. Oomens; Int. J. Mass. Spec., in press.
“Infrared spectroscopy of hydrated sulfate dianions” J. Zhou, G. Santambrogio, M. Brümmer, D.T. Moore, L. Wöste, G. Meijer, D.M. Neumark, K.R. Asmis; J. Chem. Phys. 125,  111102.
“IR-spectroscopic characterization of acetophenone complexes with Fe+, Co+, and Ni+ using free-electron laser IRMPD” R.C. Dunbar, D.T. Moore, J. Oomens; J. Phys. Chem. A 110,  7243-7254.
“Vibrational spectroscopy of mass-selected [UO2(ligand)n]2+ complexes in the gas phase: Comparison with theory” G.S. Groenewold, A.K. Gianotto, K.C. Cossel, M.J. van Stipdonk, D.T. Moore, N. Polfer, J. Oomens, W.A. de Jong, L. Visscher; J. Am. Chem. Soc. 128,  4802-4813.
“Infrared Spectroscopy of Gas-Phase Cr+ Coordination Complexes: Determination of Binding Sites and Electronic States” D.T. Moore, J. Oomens, J.R. Eyler, G. von Helden, G. Meijer, R.C. Dunbar; J. Am. Chem. Soc. 127,  7243-7254.
“Structure of the acetylene-magnesium binary complex from infrared laser spectroscopy in helium nanodroplets” D.T. Moore, R.E. Miller; J. Phys. Chem. A 108,  9908-9915.
“Structures of HCN-Mgn (n=2-6) complexes from rotationally resolved vibrational spectroscopy and ab initio theory” P.L. Stiles, D.T. Moore, R.E. Miller; J. Chem. Phys. 121,  3130-3142.