Sub-10 nm Gold Nanoarrays for Tethering Single Molecules

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Sub-10 nm Gold Nanoarrays for Tethering Single Molecules Vanessa Z-H. Chan, Sarah L. Codd, Mark J. van der Helm, Joachim P. Spatz, Carlheinz Röcker1, G. Ulrich Nienhaus1, Stefano Levi2, Frank C.J.M. van Veggel2, David N. Reinhoudt2 and Martin Möller Department of Organic and Macromolecular Chemistry, 1Department of Biophysics, AlbertEinstein Allee 11,University of Ulm, OC3, Ulm D-89069, Germany 2 Laboratory of Supramolecular Chemistry and Technology and MESA Research Institute, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands ABSTRACT Nanometer sized gold patterns were produced with controlled spacings using the combination of a top-down (e-beam lithography) and a bottom-up (macromolecular chemistry) technique. Sub-10 nm nanoparticle arrays on silicon consisting of gold nanoparticles separated by micrometer spacings were fabricated with this approach. Using electron beam lithography, templates comprising of 150 nm to 1 µm sized trenches, holes and aperiodic patterns were made in an electron-beam resist. Block copolymer micelles were then patterned into this template by spincoating. The micelles acted as positioners for a nanometer sized gold precursor that is sequestered within its core. Subsequent removal of the resist layer left an array of Au loaded organic micelles ordered according to the pattern of the template. Exposure of this substrate to a hydrogen plasma removed the organic block copolymer and resulted in an array of sub-10 nm gold nanoparticles/nanoclusters with micron separations. The gold was then used as an anchor point for the tethering of functional molecules in order to localize fluorescent molecules. INTRODUCTION The fabrication of nanostructures has become integral in many areas of research including nanoelectronics1, molecular biology2 and optics.3 In order to create sub-10 nm sized structures, top-down approaches must utilize e-beam lithography since photolithography is restricted by the wavelength of the light employed.4 However, the fabrication of sub-10 nm structures with e-beam lithography is arduous because the minimum feature size is limited to the sensitivity of the resist and e-beam proximity effects, which are difficult to control.5 Smaller dimensions are possible with bottom-up approaches based on molecular self-organization or molecular manipulation. (e.g. the manipulation of molecules and atoms using a scanning tunneling microscope). However, due to the serial nature of this technique, high throughput is not possible.6,7 Here we report a method where a top-down approach is combined with a bottom up approach8 to fabricate substrates consisting of sub-10 nanometer size gold particles with micron separations. Although e-beam lithography is employed here, photolithography can also be used to produce the templates since the typical sizes of the features required is attainable by UV lithography. The gold nanoparticles can subsequently be used to tether functional molecules resulting in a chemically patterned surface. Depending on the size of the gold nanoparticle, whose