2. 0.00 0.05 0.10 0.15 0.20 0.25 0.30 1.52.53.54.55.56.5 Cluster Diameter (nm) TOF (1/site s) Structure Sensitivity of CO Oxidation over Au/TiO 2 [Data for High Surface Are a Supported Catalysts from: Haruta, e t al., J. Catal. 115 (1989) 301; see also Haruta, Cat. Today, 36 (1997) 153.] 2CO + O 2 2CO 2

3. Nanoscience and Catalysis Introduction to issues Model catalyst preparation and characterization Correlation among structural, chemical and electronic properties of supported metal clusters Thermal stability of metal clusters Grand challenges D. Wayne Goodman Texas A&M University Department of Chemstry

4. Magnetic Moments Versus Metal Cluster Size Ni Co Fe From Gillas, Chatelain, and De Heer, Science (1994)

5. Ionization Potentials of Ni Clusters Versus Size Knickelbein, Yang, Riley, JCP (1990) ~4.0 nm ~1.2 nm 0.4 eV 0.25 eV

6. Gold Supported on Titania TEM Image of Gold Supported on Titania (from M. Date, ONRI)

7. 1.2 2.82.42.01.6 Au Particle Diameter (nm) Propylene Oxide Product Yield (%) 1 3 2 Propane H 2 /O 2 /Propylene/Ar = 1:1:1:7 P t = 1 atm T = 350 K CO 2 Selective Oxidation of Propylene Over Au/TiO 2 (Hayashi, Haruta, Shokubai, Catalysts and Catalysis, 1995)

8. Model Oxide-Supported Metal Catalysts Single Crystal Oxide Support + Metal Clusters Oxide Single Crystal e.g. MgO, TiO 2 Metal Clusters 1.0-50 nm 50 nm CD TiO 2 (110) + 0.25 Au 50 nm

9. Morphology of the TiO 2 (110) Surface 50 nm 6.0 nm Xu, Lai, Zajac, and Goodman, Phys. Rev. B (1997)

10. Au Cluster Growth on TiO 2 (110): Quasi 2-D & 3-D Au clusters [001] [110] 2-D (quasi 2-D) Au clusters can be observed at the initial stages (0.01 - 0.05 ML) of growth. 10 nm Xu, Lai, Zajac, and Goodman, Phys. Rev. B (1997)

11. STM: Au Clusters on TiO 2 (110) 30 nm

12. Au/TiO 2 (110) : Cluster Size/Density Vs. Coverage 50 nm Increasing Au coverage Lai, St. Clair, Valden and Goodman, Prog. Surf. Sci (1998)

13. Model Oxide-Supported Metal Catalysts Refractory Single Crystal Thin Oxide Film Support + Metal Clusters e.g. Mo, Re Ta, W Refractory Single Crystal Oxide Thin Film e.g. SiO 2, Al 2 O 3, MgO, TiO 2 1-10 nm Metal Clusters 1.0 - 50 nm Refractory Single Crystal Oxide Thin Film 50 nm 1.0 ML Al 2 O 3 / Re(0001) 400 nm Re(0001) 0.5 ML Ag Al 2 O 3 / Re(0001) 50 nm

14. 1.0 MLE Al 2 O 3 on Re(0001) 200 nm100 nm16 nm LEED 2.0 nm x 2.0 nm 3D surface image well-ordered, hexagonal, close-packed O 2 _ structure spacings between indentations: 2.6 _ 2.7 Å Luo, Guo and Goodman, Chem. Phys. Letts.(2000)

15. Model Oxide-supported Metal Catalysts Single Crystal Oxide SupportThin Film Oxide Support 50 nm TiO 2 (110) ++ 0.5 ML Au 0.5 ML Ag 1.0 ML Al 2 O 3 / Re(0001)

16. REACTION KINETICS CO/O 2, CO/NO, CO/H 2, C 2 H 6, C 2 H 2 on: Au, Pd, Ni/TiO 2, SiO 2, Al 2 O 3 Oxide-Supported Metal Clusters IRAS H 2 O, CO, NO, CO/O 2, CO/NO, CO/H 2 on: Au, Cu, Pd, Ni/MgO, TiO 2, SiO 2, Al 2 O 3 HREELS, ELS CH 3 OH, CO, NO, O 2 on Au, Cu, Ag, Pd, Ni/MgO, TiO 2, SiO 2, Al 2 O 3 TPD H 2 O, CO, NO, O 2 on: Au, Cu, Ag, Pd, Ni/MgO, TiO 2, SiO 2, Al 2 O 3 ISS Au, Cu, Ag, Pd, Ni/MgO, TiO 2, SiO 2, Al 2 O 3 XPS, UPS Au, Cu, Ag, Pd, Ni/MgO, TiO 2, SiO 2, Al 2 O 3 STM, STS Au, Cu, Ag, Pd, Ni/MgO, TiO 2, SiO 2, Al 2 O 3

17. Elevated-Pressure Cell Gate Valve LEED AES Ion Gun Sample Manipulator Sample Preparation Chamber XPS Apparatus STM

18. 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.02.04.06.08.010.0 Cluster Diameter (nm) TOF (1/site s) 0.5 1 1.5 2 2.5 3 3.5 TOF (1/site s) * : The Au/TiO 2 catalysts were prepared by a deposition-precipitation method, and the averaged cluster sizes were measured by TEM at 300 K. M. Haruta, et al., Catal. Lett. 44, 83 (1997). * : The Au/TiO 2 catalysts were prepared by vapor-depositing Au atoms onto a planar TiO 2 film supported on Mo(100). A 1:5 CO:O 2 mixture at a total pressure of 40 Torr and 350 K was used for reaction. Au/TiO 2 (110) Model Catalyst * Au/TiO 2 * 2CO + O 2 2CO 2 CO:O 2 = 1:5 P T = 40 Torr 350 K 300 K Unique Catalytic Activity of Nanosized Gold Particles Valden, Pak, Lai and Goodman, Catal. Lett. (1998)

19. 0 15 30 45 60 0.02.04.06.08.010.0 Cluster Diameter (nm) Population (%) Effect of Cluster Size and Morphology on Reactivity of Au/TiO 2 (110) M. Valden, X. Lai, D.W. Goodman Science 1998 30 nm 10 nm CO + ½ O 2  CO 2 CO:O 2 = 1:5 P T = 40 Torr

20. bulk metal large clusters small clusters Scanning Tunneling Spectroscopy (STS) of Supported Metal Clusters: Finite Size Effects

21. CO Oxidation Activity vs. Electronic Structure CO Catalytic Activity (CO 2 molecules per site per sec) Cluster Diameter (nm) 0.8 2.0 1.6 1.2 0.0 0.3 0.6 0.9 1.2 1.5 0108642 2CO + O 2 2CO 2 CO:O 2 = 1:5 P T = 40 Torr T = 350 K Cluster Band Gap (Volts) as Measured by STS Au/Ti(110)-(1x1) M. Valden, X. Lai, D.W. Goodman Science 1998

22. 1.52.02.53.04.03.54.5 Particle Diameter (nm) Clausius-Clapeyron Redhead Appoximation CO Heat of Adsorption (kcal/mol) 10 20 18 16 14 12 Isosteric Heats of CO Adsorption Vs. Au Cluster Size BULK GOLD Meier, Bukhtiyarov, and Goodman, J. Phys. Chem, (2002)

23. E(eV) DOS (states/eV) Au/TiO 2 (110) Au(001) FLAPW Calculations for Au and Au/TiO 2 (110) Yang, Wu, Goodman, PRB (2000)

24. FLAPW calculated charge density difference obtained by substracting the superposition of the charge densities of a Au monolayer and TiO 2 (110) from that of Au/TiO 2 (110) Yang, Wu, Goodman, PRB (2000) Theory: FLAPW Calculations of Au/TiO 2 (110) Predicts an initial state core level shift for Au on TiO 2 to a lower binding energy of ~1.2 eV, consistent with the experimental value of 1.0 eV Au Ti

25. Au/SiO 2 Core Level Shifts Au/TiO 2 0.5 1.0 1.5 -.5 2.0 Final StateInitial StateTotal Contributions BE 1.6 1.8 -0.2 1.8 0.8 (eV) XPS Core Level Shifts: Au/TiO 2 (110) ~3.0 nm St.Clair and Goodman, Topics in Catal (2000)

26. Au Cluster Height vs. STM Tip Bias

27. +1 0 Au +0.03 eV -0.11 eV Charge on Au Clusters vs. CO Binding Energy P. Bagus, unpublished data

28. TPD: Au from SiO 2 as a Function of Coverage Au Coverage Heat of sublimation Decreasing Cluster Size Luo, Kim, and Goodman, J. Mol. Catal (2001) Decreasing Cluster Size

29. Figure 7 CO Oxidation Over Au/TiO 2 as a Function of Reaction Time Valden, Lai & Goodman, Science (1998) 2CO + O 2 2CO 2 CO:O 2 = 1:5 P T = 40 Torr T = 350 K Au/TiO 2 (110) Reaction Rate, CO 2 molecules per site per second Reaction Time (minutes)

30. Morphological Changes of Au/TiO 2 (110) Fresh 0.25 ML Au/TiO 2 (110) After 120 min exposure to 10 Torr CO-O 2 (2:1) 50 nm Before RxAfter Rx 50 nm Lai and Goodman, J. Mol. Catalysis (2000)

31. Microscope: RHK VT - UHV300 Variable Temperature: 100 - 600 K Pressure Range: 10 -10 - 10 3 Torr eB IP load lock TMP MS S Metal Dosers e-Beam AES Sample Storage SP 10 -10 Torr STM Gas UHV-Elevated Pressure STM Apparatus 10 -10 - 10 3 Torr 10 -10 Torr

32. UHV5.4 Torr CO:O 2 Surface regrowth around Au clusters Cluster size reduction Adhesion of cluster to tip Cluster size increase Surface roughening STM of Au Clusters on TiO 2 at 400K Kolmakov and Goodman, Catal. Letts (2000)

33. STM Tip as a Mask for Metal Deposition Kolmakov and Goodman, Physical Review B, submitted

34. Large Scale STM Image of Tip Silhouette for Au Deposition RT Au DepositionSame area after 950K anneal 250 nm Kolmakov and Goodman, Physical Review B, submitted

35. Au/TiO 2 (110) Before and After Annealing to 950K As depositedAfter a 950K x 30 min. anneal 100 nm Kolmakov and Goodman, Physical Review B, submitted

36. sample tip   d shadow Au Evaporation onto Ag/TiO 2 at RT Ag Au + Ag

37. Comparative Stability of Ag and Au-Ag Clusters to 2 x 10 4 Pa Air Ag particles Au and Au-Ag mixed clusters TiO 2 (110) Kolmakov and Goodman, Physical Review B, submitted

38. IRAS: CO/Cu-Pd/Al 2 O 3 ISS: Cu-Pd/Mo(110) Pd Cu IRAS: Site Differentiation of Mixed-Metal Catalysts Rainer, Xu, Holmblad, and Goodman, J. Vac. Sci. Technol. A (1997)

39. Catalytic reactivity and selectivity are markedly different for clusters < ~3.0 nm. Nanoclusters are generally unstable to reaction conditions, i.e., understanding and maintaining stability are the keys to technological break- throughs. Core-level shifts, valence band structure, sublimation energies, and adsorbate binding energies are unique for clusters < ~3.0 nm. Conclusions

40. What do we need to know about supported nanoclusters? Properties as a function of metal-to-nonmetal transition for a range of transition metals  physical structure (bond lengths, angles, etc.)  electronic properties (valence band, core levels, etc.)  optical properties (plasmon, HOMO-LUMO gap, etc.)  melting temp., sublimation temp., etc.  adsorbate bonding energies, vibrational freq., etc.  catalytic properties for several probe reactions Methods for the preparation of mono-dispersed clusters with selected sizes Precise relationship between physical and chemical properties  theory ------- experiment Detailed sintering kinetics and role of support in altering catalytic activity Quantitative thermochemical information about metal wetting, nucleation, and particle sintering

41. Coworkers Current: Dr. Ashok Santra Byoun Koun Min Dr. Young Dok Kim Jeff Stultz Emrah Ozensoy Dr. Christian Hess Cheol-Woo Yi Dr. Changmin Kim Dr. Paul Bagus Tushar Choudhary Fan Yang Tao Wei Dheeraj Kumar Dr. Sivadinarayana Chinta Past: Dr. Andrei Kolmakov Dr. Charles Chusuei Dr. Micha Valden Dr. Xiaofeng Lai Dr. Doug Meier Dr. Todd St. Clair Dr. Gerry Zajac Dr. Jens Guenster Dr. Qinlin Guo Dr. Valeri Bukhtiyarov Dr. Kent Davis Kai Luo

42. Support Department of Energy, the Office of Basic Energy Sciences, Division of Chemical Sciences The Robert A. Welch Foundation Dow Chemical Company