Scanning Probe Microscopies in Electrochemical Investigations of Model Catalysts and Biological Molecules-University of Science and Technology of China

Scanning Probe Microscopies in Electrochemical Investigations of Model Catalysts and Biological Molecules

Date：2016-11-10

Speaker:	Prof. Ulrich Stimming School of Chemistry, Newcastle University
Time:	2016-11-21　10:00
Place:	ROOM 9004, Hefei National Laboratory Building
Detail:	Abstract: 　　Electrochemical scanning tunnelling microscopy (EC-STM) is a powerful tool which gives the opportunity to investigate surfaces and its adsorbates with unprecedented resolution under in-situ electrochemical conditions. During EC-STM experiment, the tunnelling current between the tip and the substrate is measured. Due to its working principle, EC-STM can’t image insulator. However, the more recent scanning electrochemical potential microscopy (SECPM) which measures the potential at zero current can image adsorbates with poor conductivity, and is specifically suitable for biological moleules. 　　Two major areas will be discussed: One, where metal particles are deposited on typically Au(111) and carbon surfaces and the reactivity of such particles, e.g. Pd and Pt particles, were investigated regarding the hydrogen reaction. This includes creating single nanoparticles with the tip of an EC-STM whereas the tip was used subsequently as a local sensor to determine the reactivity of the single particles [1-3]. Specific reactivity can change by orders of magnitude depending on the density of particles, their size and the kind of substrate. 　　The second area looks at biological structures, specifically redox enzyme molecules adsorbed on pre-oxidised highly oriented pyrolytic graphite (HOPG) surfaces. Here both EC-STM and SECPM are being employed and their respective capabilities are shown. Electron-transfer properties of enzyme molecules can be investigated using EC-STM [4-5]. Imaging enzyme molecules, SECPM shows a higher resolution and a better contrast than EC-STM, possibly because no current flows though the enzymes during the SECPM measurement compared to EC-STM, which can avoid damage to protein structure [6]. Besides, SECPM can also provide charge distribution information of enzyme molecules [6]. 　　Both research areas demonstrate the exciting capabilities of EC-STM and SECPM under in-situ and also physiological conditions. References [1] H. Wolfschmidt, D. Weingarth, and U. Stimming, ChemPhysChem, 11, (2010) 1533. [2] J. Meier, J. Schiotz, P. Liu, J. K. Nørskov, and U. Stimming, Chem. Phys. Lett., 390, (2004) 440. [3] M. Eikerling, J. Meier, and U. Stimming, Z. Phys. Chem. (Int. Ed.), 217, (2003) 395. [4] M. Wang, S. Bugarski, and U. Stimming, J. Phys. Chem. C, 112 (2008) 5165. [5] M. Wang, S. Bugarski, and U. Stimming, Small, 4 (2008) 1110.. [6] C. Baier and U. Stimming, Angewandte Chem.Int.Ed. 48 (2009) 5542.
Organizer:	Hefei National Laboratory for Physical Sciences at the Microscale