Site-Specific Placement of Au Nanoparticles on Chemical Nanopatterns Prepared by Molecular Transfer Printing Using Block-Copolymer Films

Authors

  • M. Serdar Onses,

    1. Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA
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  • Christopher J. Thode,

    1. Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA
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  • Chi-Chun Liu,

    1. Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA
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  • Shengxiang Ji,

    1. Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA
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  • Peter L. Cook,

    1. Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706, USA
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  • Franz J. Himpsel,

    1. Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706, USA
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  • Paul F. Nealey

    Corresponding author
    1. Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA
    • Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA.
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Abstract

Inexpensive, large area patterning of ex-situ synthesized metallic nanoparticles (NPs) at the nanoscale may enable many technologies including plasmonics, nanowire growth, and catalysis. Here, site-specific localization of Au NPs onto nanoscale chemical patterns of polymer brushes is investigated. In this approach, patterns of hydroxyl-terminated poly(styrene) brushes are transferred from poly(styrene-block-methyl methacrylate) (PS-b-PMMA) block copolymer films onto a replica substrate via molecular transfer printing, and the remaining areas are filled with hydroxyl-terminated poly(2-vinyl pyridine) (P2VP-OH) brushes. Citrate-stabilized Au NPs (13 nm) selectively bind to P2VP-OH functionalized regions and the quality of the resulting assemblies depends on high chemical contrast in the patterned brushes. Minimization of the interpenetration of P2VP-OH chains into PS brushes during processing is the key for achieving high chemical contrast. Large area hexagonal arrays of single Au NPs with a placement accuracy of 3.4 nm were obtained on patterns (∼20 nm spots, ∼40 nm pitch) derived from self-assembled cylinder-forming PS-b-PMMA films. Linear arrays of Au NPs were generated on patterns (40 nm lines, 80nm pitch) derived from lamellae-forming PS-b-PMMA that had been directed to assemble on lithographically defined masters.

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