Site-Specific Recognition of Nanophase-Separated Surfaces of Amphiphilic Block Copolymers by Hydrophilic and Hydrophobic Gold Nanoparticles

摘要

Ordered two and three-dimensional arrays of uniformly distributed nanoparticles are attractive for applications in nanoelectronics,[1] nanooptics,[2] and plasmonics.[3] Bottom-up fabrication techniques such as self-assembly and Langmuir-Blodgett techniques have been extensively explored. More recently, highly ordered nanoarrays have been successfully fabricated by a template method that uses natural nanoarchitectures such as DNA,[4], [5] bacterial surface layer proteins,[6], [7] ferritin,[8] chaperonin,[9] viruses,[10], [11] and bacteriophages.[12] These methods provide attractive bottom-up fabrication schemes to produce regular nanoscale patterns; however, most natural templates require tedious handling and preparation. In this respect, artificial nanoarchitectures such as nanophase-separated block copolymers have distinctive advantages. In particular, diblock copolymer films that provide cylindrical nanodomains oriented perpendicular to the substrate are attractive because they produce templates and masks that are predicatable and controllable with nanoscale order. Recently, Iyoda and co-workers prepared amphiphilic diblock copolymers, PEOm-b-PMA(Az)n,[13] consisting of hydrophilic polyethylene oxide (PEO) and hydrophobic polymethacrylate with azobenzene-based liquid crystalline side-chains (PMA(Az)), which readily self-assemble into hexagonally packed PEO cylinders in a PMA(Az) matrix. At the surface, each PEO domain is in the form of a circular hollow surrounded by the PMA(Az) matrix. The periodic structure of PEO domains arranged with hexagonal symmetry is regularly tunable by changing the relative volume fractions of the copolymer components. However, to use such PEOm-b-PMA(Az)n films as nanotemplates for the construction of periodic nanoparticle arrays, it is necessary to elucidate fundamental features of site-specific recognition processes on these nanophase-separated surfaces. Herein, we report the self-assembly of gold nanoparticles on a nanophase-separated PEOm-b-PMA(Az)n film. The effects of the surface properties, concentration of gold nanoparticles, dipping time, and the composition of the dispersion medium on-site coverage and selectivity were investigated by a dip-coating method.