Research and Labs
Single molecule and co-adsorption studies at the atomic scale
Group members: Barbara A. J. Lechner, Xiaofeng Feng
Investigating molecular adsorption and reactions on metal and graphene surfaces is important for the understanding of many aspects of surface chemistry and catalysis. We use the powerful scanning tunneling microscopy (STM) technique to study the adsorption behavior and interactions of molecules at the atomic scale. Recent work includes single molecule studies, such as the investigation of water, ammonia and carbon dioxide on a metal and graphene surface. In addition, we investigated the motion of graphene flakes on a graphene monolayer surface, which indicates the superlubric properties in graphitic materials. Now we are moving towards more complex systems, exploring the co-adsorption of different molecules and their interactions on the surface to shed light in the atomic-scale mechanism of surface reactions.
X. Feng, S. Maier, M. Salmeron
Water Splits Epitaxial Graphene and Intercalates.
J. Am. Chem. Soc., 2012. 134: p. 5662–5668. http://pubs.acs.org/doi/pdf/10.1021/ja3003809
S. Maier, I. Stass, J. I. Cerda, and M. Salmeron
Bonding of Ammonia and Its Dehydrogenated Fragments on Ru(0001)
J. Phys. Chem. C, 2012. 116: p. 25395-25400. http://dx.doi.org/10.1021/jp308835x
X. Feng, S. Kwon, J. Y. Park, and M. Salmeron
Superlubric Sliding of Graphene Nanoflakes on Graphene.
ACS Nano, 2013. 7: p. 1718-1724. http://dx.doi.org/10.1021/nn305722d
Investigation of Iron Oxide Surfaces using Scanning Tunneling Microscopy and Non-contact Atomic Force Microscopy
Group members: Sara Barja, Leonid Lichtenstein
Hematite (Fe2O3) is a promising substrate for solar water splitting cells. Herein, we focus on elucidating the correlation between the morphology and the electronic structure of the Fe2O3(0001) surface. For this purpose, we apply a combination of scanning tunneling microscopy (STM) and spectroscopy (STS) at low temperatures in ultra high vacuum . Additionally, a tuning fork sensor is in use making non-contact atomic force microscopy (nc-AFM) possible. This method allows us to acquire maps of local contact potential and to study local work function differences.
Group members: Alexander M Buyanin, Yingjie Zhang, Wei Bao
Organic monolayers are investigated using atomic force microscopy to understand the relationship between molecular structure and fundamental electronic and mechanical properties. Chemically reactive organic films are introduced to gaseous and liquid molecules and the films are monitored for changes occurring due to specific binding events. Intra- and Inter-molecular charge transport is studied in oligothiophene based films.
B.L.M. Hendriksen, F. Martin, Y. Qi, C. Mauldin, N. Vukmirovic, J. Ren, H. Wormeester, A.J. Katan, V. Altoe, S. Aloni, J.M.J. Fréchet, L.-W. Wang, and M. Salmeron
Electrical transport properties of oligothiophene-based molecular films studied by current sensing atomic force microscopy
Nano letters, 2011. 11(10): p. 4107-12. http://www.ncbi.nlm.nih.gov/pubmed/21848283
F. Martin, B. Hendriksen, A. Katan, I. Ratera, Y. Qi, B. Harteneck, J.A. Liddle, and M. Salmeron
Ultra-flat coplanar electrodes for controlled electrical contact of molecular films
Rev. Sci. Instr., 2011. 82(12): p. 123901-123901. http://link.aip.org/link/RSINAK/v82/i12/p123901/s1&Agg=doi
G. Koshkakaryan, P. Jiang, V. Altoe, D. Cao, L.M. Klivansky, Y. Zhang, S. Chung, A. Katan, F. Martin, M. Salmeron, B. Ma, S. Aloni, and Y. Liu
Multilayered nanofibers from stacks of single-molecular thick nanosheets of hexakis(alkoxy)triphenylenes
Chem. Commun., 2010. 46(45): p. 8579-81. http://www.ncbi.nlm.nih.gov/pubmed/20972497
Investigation of Heterogeneous Catalysis on Nanoparticles
Group members : Sophie Carenco, Chenghao Wu, Jizhe Zhang
Collaborators: Brandon Beberwyck (Alivisatos group)
We study the reactivity of metal nanoparticle catalysts of varying size, shape, and composition (synthesized in collaboration with Prof. Paul Alivisatos's group) under relevant conditions of pressure and temperature. We follow changes in the electronic, chemical, and physical structure of the particles as they are exposed to reactive gases using ambient pressure x-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) at the Advanced Light Source (ALS), the Berkeley Lab synchrotron. Typically these x-ray techniques require ultra high vacuum environments, but our group has developed unique tools for performing experiments near atmospheric pressures. Therefore, we can study the catalyst reactivity in situ, under realistic conditions. Finally, we study the adsorption of gases on model catalyst surfaces using scanning tunneling microscopy to complement our research on nanoparticles.
A. Tuxen, S. Carenco, M. Chintapalli, C.-H. Chuang, C. Escudero, E. Pach, P. Jiang, F. Borondics, B. Beberwyck, A. P. Alivisatos, G. Thornton, W.-F. Pong, J. Guo, R. Perez, F. Besenbacher, and M. Salmeron
Size-dependent dissociation of carbon monoxide on cobalt nanoparticles.
J. Am. Chem. Soc., 2013. 135: p. 2273-2278. http://dx.doi.org/10.1021/ja3105889
S. Carenco, A. Tuxen, M. Chintapalli, E. Pach, C. Escudero, T. D. Ewers, P. Jiang, F. Borondics, G. Thornton, A. P. Alivisatos, H. Bluhm, J. Guo, and M. Salmeron
De-alloying of Cobalt from CuCo Nanoparticles under Syngas Exposure.
J. Phys. Chem. C, 2013. 117: p. 6259. http://dx.doi.org/10.1021/jp4000297
C. Escudero, P. Jiang, E. Pach, F. Borondics, M. W. West, A. Tuxen, M. Chintapalli, S. Carenco, J. Guo, and M. Salmeron
A reaction cell with sample laser heating for in situ soft X-ray absorption spectroscopy studies under environmental conditions.
Journal of Synchrotron Radiation, 2013. 20: p. 504. http://dx.doi.org/10.1107/S0909049513002434
In situ studies of Electrode Interfaces
Group members: Chenghao Wu
This project aims to investigate the molecules / ions at the electrolyte / electrode interfaces by means of in-situ x-ray spectroscopy techniques (XAS, XES, RIXS etc.) at the Advance Light Source, LBNL. Such liquid / solid interfaces are extremely important in most of the electrochemical reactions, but the chemical nature of the interfacial region as well as how the interfacial molecules / ions respond to the electrical fields is not well understood. We have been developing new characterization techniques based on regular XAS instrument with modulated x-ray source and static / flow liquid cell systems, with which we will be able to study such electrolyte / electrode interfaces under real electrochemical reaction conditions. Such in-situ characterization techniques can be utilized to investigate many useful electrochemical reactions, e.g., electrocatalysis, photoelectrochemistry (including water splitting and CO2 reduction), intercalation process in lithium ion batteries, etc.
Imaging Charge Transport of Organic-Inorganic Nanocomposite Materials
In collaboration with Alivisatos and Xu groups, we are investigating the charge transport properties of a hybrid material consisted of inorganic nanoparticles and organic molecules. We are using Electrostatic Force Microscopy, Kelvin Probe Force Microscopy, and Conductive AFM to investigate both device-level physics such as contact resistance and charge percolation pathways of organic-inorganic thin film transistors, and molecular-level physics such as electronic coupling and Coulomb blockade effects of single nanoparticle-organic molecule systems.
Nanoscale Optical Imaging Spectroscopy
Project in collaboration with Jim Schuck Group - see also: http://foundry.lbl.gov/schuckgroup/page1/page2/page13/page13.html
Group members: Wei Bao
This project aims at developing a new general imaging technique base on Scanning Probe Microscopy (SPM), in order to bring the optical spectroscopy's spatial resolution down to nanometer scale. This technique will be used to discover the unravel correlation between local chemical morphology and local photocurrent generation efficiency in the state-of-art Organic Solar Cells (OSC). A combination of electrical imaging techniques and optical spectroscopy techniques with unprecedented high spatial resolution will provide new insights on this topic.
Group members: Zhongwei Zhu
We use high-pressure scanning tunneling microscopy to investigate the metal catalyst surface reconstruction at high gas pressures. Stepped metal surfaces are used as models to mimic the real catalysts that expose a high concentration of unsaturated sites. Ambient-pressure X-ray photoelectron spectroscopy is employed to identify the chemical states relevant to the restructuring processes.
Tao, F.; Dag, S.; Wang, L. W.; Liu, Z.; Butcher, D. R.; Bluhm, H.; Salmeron, M.; Somorjai, G. A. Science 2010, 327, 850-853
Zhu, Z.; Tao, F.; Zheng, F.; Chang, R.; Li, Y.; Heinke, L.; Liu, Z.; Salmeron, M.; Somorjai, G. A. Nano Lett. 2012, 12, 1491-1497
Zhu, Z.; Butcher, D. R.; Mao, B.; Liu, Z.; Salmeron, M.; Somorjai, G. A. J. Phys. Chem. C 2013, 117, 2799-2804.
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