Template-assisted formation of gradient concentric gold rings.

Gradient concentric rings of polymers, including (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly(methyl methacrylate) (PMMA), with unprecedented regularity were formed by repeated "stick-slip" motion of the contact line in a sphere-on-flat geometry. Subsequently, polymer rings served as templates to direct the formation of concentric Au rings. Three methods were described. The first two methods made use of either UV (i.e., on MEH-PPV) or thermal treatment (i.e., on PMMA) on Au-sputtered polymer rings, followed by ultrasonication. The last method, however, was much more simple and robust, involving selective removal of Au and polymer (i.e., PMMA) consecutively.