In their search for molecules with certain characteristics, chemists have produced millions of new, increasingly complex synthetic materials by altering molecules' chemical structures.
Taking cues from nature, Northwestern University researchers have recently tested a new method for achieving the molecular properties they seek: by changing the geometry of the surface to which molecules are bound.
"For years chemists have been making molecules to solve problems each one more synthetically complicated than the last but we still haven't come close to achieving what nature can do with much simpler chemistry,'" said Bartosz A. Grzybowski, Kenneth Burgess Professor of Chemical and Biological Engineering and Chemistry at Northwestern's McCormick School of Engineering and Applied Science. "Nature's most complex component of life, the protein, is made from only 21 simple amino acids. This research explores the idea that it's not the molecule you have that's important, it is how it interacts with its environment."
Using this idea, the researchers developed a technique in which a single type of molecule is placed on nanoparticles with two different regions of curvature. Although the molecules are atomically identical, they demonstrate unique chemical properties depending on what region of curvature they are bound to.
A paper describing the research, "Geometric Curvature Controls the Chemical Patchiness and Self-Assembly of Nanoparticles," was published August 18 in Nature Nanotechnology.
The researchers began by affixing molecules of a carboxylic acid at various points on several gold nanoparticles, some as small as five nanometers in diameter. Each nanoparticle possessed a different geometry. On nanoparticles exhibiting a greater curvature, the molecules were naturally spaced father apart; on nanoparticles with more gradual curvature, they were closer together.
The differences in curvature influences the dis
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