Angewandte Chemie International Edition
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Cover Picture (Angew. Chem. Int. Ed. Engl. 4/1990)
The cover picture is a schematic drawing of a coated oscillator crystal of a quartz microbalance that is in contact with a liquid. This highly sensitive “weighing technique” is based on the principle that the frequency of an oscillator crystal changes as a quantitative function of mass. With this technique it is possible to follow in situ—and with microscopic resolution–surface processes occurring at a solid/liquid phase boundary. For example, the experimental curve reproduced in the right half of the picture depicts the change in frequency that accompanies electrochemical oxidation/reduction of a gold electrode. Simultaneous recording of changes in current flow permits conclusions to be drawn with respect to the smoothness of the electrode surface. Other recent applications for the quartz microbalance developed within the past decade are described in the review by R. Schumacher on pp. 329 ff.—The cover picture was created by Illustration & Design, Mannheim (FRG).