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December 22, 2003
Volume 81, Number 51
CENEAR 81 51 pp. 39-50

ISSN 0009-2347


PHYSICAL & SURFACE CHEMISTRY

STU BORMAN, C&EN WASHINGTON

This was also a busy year for those who like to "get physical" and to focus on the surface of things.

BEND OVER BACKWARD Langer's group created this controllably switchable self-assembled monolayer surface. © SCIENCE 2003

The speed of aqueous proton transfer from acid to base was measured and a detailed mechanism proposed by Ehud Pines of Ben-Gurion University of the Negev, Israel; Erik T. J. Nibbering of Max Born Institute for Nonlinear Optics & Short Pulse Spectroscopy, Berlin, Germany; and coworkers [Science, 301, 349 (2003)]. They found an extra stage of the mechanism that had never been observed previously.

Also awash with significance were findings by Anne Willem Omta of the FOM Institute for Atomic & Molecular Physics, Amsterdam, the Netherlands, and coworkers that ion solvation affects water's hydrogen-bonding network only in the single layer of water molecules surrounding the ion [Science, 301, 347 (2003)]. This contradicts existing views that ions cause nonlocalized water-structure effects throughout an entire solution.

A truly momentous development was the determination of the largest transient dipole moment ever measured--150 debyes (D), in a carotene-porphyrin-fullerene artificial photosynthetic system--by Sergei N. Smirnov of New Mexico State University; Devens Gust, Ana L. Moore, and Thomas A. Moore of Arizona State University; and coworkers [J. Phys. Chem. A, 107, 7567 (2003)]. The previous record was 100–120 D. The study is of fundamental interest and could have implications for ultrafast switching.

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MOLECULAR RULERS Walker and Steel developed surfactants (green oval linked to red circle) capable of profiling polarity changes across water-oil interfaces (surrounding molecules). COURTESY OF R. A. WALKER

In surface science this year, a switchable surface created by MIT's Robert S. Langer and coworkers was hailed as "amazing" by one observer. The self-assembled alkanethiolate monolayer can be made to stand or collapse by applying an electrical potential to reversibly switch its conformational state [Science, 299, 371 (2003)]. Such surfaces might be useful for microfluidics, drug delivery, electro-optics, or offset printing.

Little has been known about the atomic-scale dynamics of defects on transition-metal oxide crystal surfaces. But using time-lapse scanning tunneling microscopy, Flemming Besenbacher of the University of Aarhus, in Denmark, and coworkers showed this year that oxygen vacancies diffuse across a surface along specific crystal directions; these findings could aid the ability to control the number and distribution of oxygen vacancies on such surfaces [Science, 299, 377 (2003)].

A method to profile polarity changes across water-oil interfaces was developed by Robert A. Walker and William H. Steel of the University of Maryland, College Park [Nature, 424, 296 (2003)]. It's based on "molecular rulers": surfactants that each contain a hydrophobic probe, a spacer, and an anionic head group. The technique has implications for phase-transfer catalysis, drug bioavailability, and other interfacial phenomena.

Chemistry Highlights 2003
Introduction
Organics & Carbs
Medchem
Bioscience
Structure
Bioengineering
Sensors & Analysis
Inorganic Chemistry
Environment
Materials
Supramolecular Chemistry
Nanotech & Molecular Electronics
Polymer Chemistry
Physical & Surface Chemistry


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Copyright © 2003 American Chemical Society



 
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