Atomic-Resolution Microscopy in Water

Abstract

The scanning tunneling microscope is revolutionizing the study of surfaces. In ultra-high vacuum it is capable not only of imaging individual atoms but also of determining energy states on an atom-by-atom basis. It is now possible to operate this instrument in water. Aqueous optical microscopy is confined to a lateral resolution limit of about 2000 angstroms, and aqueous x-ray microscopy has yielded a lateral resolution of 75 angstroms. With a scanning tunneling microscope, an image of a graphite surface immersed in deionized water was obtained with features less than 3 angstroms apart clearly resolved. Further, an image measured in saline solution demonstrated that the instrument can be operated under conditions useful for many biological samples.

Multidimensional electrochemical imaging in materials science

“…If the UME is positioned close to the polymer-solution interface (in this case metallopolymers of the type Os(2,2′ -bipyridyl) 2 (poly-4-vinylpyridine) 5 Cl]Cl) and used to generate a redox species in solution (here [Ru(CN) 6 ] 3− ) which diffuses to the polymer film where electron transfer occurs (Eq. 1), the i-t transient in this step provides information about the kinetics of the electrontransfer (ET) process between the solution species and the polymer-bound moiety and about the concentration of redoxactive species in the polymer film.…”

“…STM is, in this respect, used for direct imaging of the density of states at surfaces with atomic resolution and to follow the dynamic of surface processes [3,4]. It was only a few years after this that STM could be performed on liquids and in electrochemical cells under potentiostatic or galvanostatic control [4][5][6] (Fig. 1a) and found applications in catalysis research [7], for electrodeposition studies of metals and conductive polymers [8], for investigation of morphology changes resulting from electrochemical treatment [9], and for corrosion studies [9,10].…”

Insulated gold scanning tunneling microscopy probes for recognition tunneling in an aqueous environment

“…1 The key to doing this was to insulate the probe almost completely, leaving only a small amount of metal exposed at its apex. Probes have been etched from Pt or a Pt/Ir alloy and insulated with wax, paint or glass.…”

Design of a scanning tunneling microscope for electrochemical applications

“…For example, the design of Sonnenfeld et al 15 uses only a drop of liquid, and is, therefore, difficult to operate with high vapor pressure solvents (e.g., CH 3 CN or alcohols) or with auxiliary electrodes, as would be required for most electrochemical investigations. Another microscope designed by Sonnenfeld et al 5 is better suited for electrochemical work, but exposes potentially active materials (e.g., steel) to the electrochemical environment. Itaya et al 7 have also constructed a tunneling microscope that has produced atomic resolution images in liquids, but their microscope does not allow for reproducible or automated control over large distance excursions in the z direction.…”