We demonstrate template-guided self-assembly of gold nanoparticles into ordered arrays of uniform clusters suitable for high-performance SERS on both flat (silicon or glass) chips and an optical fiber faucet. Cluster formation is driven by electrostatic self-assembly of anionic citrate-stabilized gold nanoparticles (~11.6 nm diameter) onto two-dimensionally ordered polyelectrolyte templates realized by self-assembly of polystyrene-block-poly(2-vinylpyridine). A systematic variation is demonstrated for the number of particles (N ≈ 5, 8, 13, or 18) per cluster as well as intercluster separations (S(c) ≈ 37-10 nm). Minimum interparticle separations of <5 nm, intercluster separations of ~10 nm, and nanoparticle densities on surfaces as high as ~7 × 10(11)/in.(2) are demonstrated. Geometric modeling is used to support experimental data toward estimation of interparticle and intercluster separations in cluster arrays. Optical modeling and simulations using the finite difference time domain method are used to establish the influence of cluster size, shape, and intercluster separations on the optical properties of the cluster arrays in relation to their SERS performance. Excellent SERS performance, as evidenced by a high enhancement factor, >10(8) on flat chips and >10(7) for remote sensing, using SERS-enabled optical fibers is demonstrated. The best performing cluster arrays in both cases are achievable without the use of any expensive equipment or clean room processing. The demonstrated approach paves the way to significantly low-cost and high-throughput production of sensor chips or 3D-configured surfaces for remote sensing applications.

Robust lithographic templates, with sub-50 nm feature and spatial resolutions, that exhibit high patterning integrity across a full-wafer are demonstrated using self-organized copolymer reverse micelles on 100 mm Si wafers. A variation of less than 5% in the feature size and periodicity of polymeric templates across the entire wafer is achieved simply by controlling the spincoating process. Lithographic pattern transfer using these templates yields Si nanopillar arrays spanning the entire wafer surface and exhibiting high uniformity inherited from the original templates. The variation in geometric characteristics of the pillar arrays across the full-wafer surface is validated to be less than 5% using refl ectance spectroscopy. The physical basis of the change in refl ectance with respect to sub-10 nm variations in geometric parameters of pillar arrays is shown by theoretical modelling and simulations. Successful fabrication of highly durable TiO 2 masks for nanolithography with sub-50 nm feature width and spatial resolutions is achieved through highly controlled vapour phase processing of reverse micelle templates. This allows lithographic pattern-transfer of organic templates with a feature thickness and separation of less than 10 nm, which is otherwise not possible through other approaches reported in literature.

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We demonstrate the nanofabrication of flexible plasmonic sensors comprising of gold nanocones achieved by nanoimprint lithography on polycarbonate (PC) sheets. Thermal imprinting was performed consistently over a large area (roughly the size of a 6 in. wafer) with a batch process; this can be extended to a continuous process using UV roll-toroll nanoimprinting. This provides a process to scale up the fabrication of continuous imprinted rolls of PC sheets at an optimal rate of 3−5 m/min. The geometry of the peaks and the valleys of the nanocones in the as-imprinted PC is defined by the nickel mold used during imprinting; however, the gaps between the nanocones are tailored by varying the thickness of the gold deposited onto the substrate. Two different thicknesses of gold were deposited to study the effect of geometry on plasmonic sensing. The resulting PC sheet with gold coating enables highly sensitive detection of analytes by Surface Enhanced Raman Spectroscopy (SERS) by virtue of plasmonic hotspots generated at the valleys, whose presence was confirmed by scattering scanning near-field optical microscopy. This is promising, particularly when the SERS substrate developed is highly reproducible, cost-effective, transparent, and flexible, finding application in nanoplasmonic sensing and on-field environmental monitoring, where rigid SERS substrates would not be appropriate.