Abstract
We prepared a high-density array of “accordion-like” plasmonic silver nanorods over a large area (2.5 × 2.5 cm2) that exhibited multiple electromagnetic responses to visible and near-infrared (NIR) wavelengths. This array of “accordion-like” silver nanorods was fabricated by confining the lamellae-forming polystyrene-block-poly (methyl methacrylate) copolymer (PS-b-PMMA) inside the cylindrical pores of an aluminum oxide (AAO) template grafted with thin neutral brush layers. PS and PMMA lamellar nanodomains with sizes of 15 nm were alternatively stacked along the nanorod direction. After the AAO template was removed, a 5-nm-thick layer of silver was thermally deposited on only the PS nanodomains. Owing to the multiple resonances exhibited in the visible and NIR regimes, the array could be used for multi-analyte detection. Furthermore, this concept of fabricating sophisticated nanoscale architectures by utilizing block copolymer self-assembly and incorporating plasmonic metals into one nanodomain could be applied to realize large-scale metamaterials that function under visible and NIR wavelengths.
Highlights
Plasmonics has achieved many unique optical properties by exploiting the surface plasmon polaritons, or the collective oscillation of free charges strongly coupled to light, that exhibit subwavelength modes with extremely enhanced electric field intensities[1,2,3]
This paper demonstrates the fabrication of sophisticated nanostructures that are difficult to realize through the top–down process in a large optical device by taking advantage of block copolymer (BCP) self-assembly
While the vertical orientation of the lamellae-forming PS-b-PMMA was achieved on a flat surface with the neutral brush for a range of film thicknesses (H) (0.3–1.4 H/L0)[59], stacked lamellae are observed inside the an aluminum oxide (AAO) for D/L0 values between 0.91 and 2.31 (D is the diameter of the AAO pore)
Summary
Plasmonics has achieved many unique optical properties by exploiting the surface plasmon polaritons, or the collective oscillation of free charges strongly coupled to light, that exhibit subwavelength modes with extremely enhanced electric field intensities[1,2,3]. Taking advantage of such properties, two-dimensional ensembles of plasmonic nanostructures have been arranged for surface-enhanced Raman scattering substrates[4,5,6], metamaterials[7,8,9], and nonlinear optics[10,11]. Gansel et al.[34] achieved broadband circular dichroism in a gold helix photonic metamaterial fabricated through direct-write
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