Molecules and Atoms on Metals Surfaces
The following images show molecules and atoms on the surface of the (111) crystal face of silver, commonly denoted as Ag(111).
All of these images were taken using a unique Scanning Tunneling Microscope designed
and built in the Hamers Research Group at the University of Wisconsin-Madison. This particular microscope is unique in that it is capable of imaging molecules at temperatures as low as 110 kelvin.
The research being carried out using this microscope are aimed at achieving
a fundamental understanding of catalysis at the surfaces of metals.
STM image of cyclopentene molecules on
Ag(111) surface. It has long been thought that inhomogeneities such as defects and/or steps on metal surfaces act as sites for preferential chemical
reactivity.
This images shows a silver surface which has been exposed to cyclopentene. The cyclopentene molecules clearly adsorb almost exclusively along specific lines. These lines coincide with the locations of steps on the underlying silver surface. In this image, each round ball is a single cyclopentene molecules
(Copyright R.J. Hamers and X. Chen).
Enlarged View
STM Images of three different molecules on the Ag(111) surface
This set of three images shows how the scanning tunneling microscope (STM) is
able to distinguish among different molecules that have different shapes. The
three molecules showsn here are thiophene, 2,5-dimethylthiophene, and 2,2'-bithiophene. These three molecules are similar chemically, but have different shapes. The STM images show that (as above), all three molecules strongly prefer to be bonded at steps on the silver surface. However, high-resolution images such as those shown here are able to resolve the internal structure and shope of the molecules as well. This provides a means to distinguish among different molecules and to learn about the architecture within the molecules themselves.
(Copyright X. Chen, E.R. Frank,and R.J. Hamers)