A good surface-enhanced Raman spectroscopy (SERS) substrate requires precise control of the enhancement factor in large area which may be achieved with large-scale hot spot engineering. Here, we present a facile method for synthesizing 2-D hexagonally patterned gold nanoparticle arrays on centimeter-sized substrates of mesoporous silica thin films with vertical nanochannels by chemical reduction. Scanning electron microscopy images showed densely packed gold nanoparticles directly anchored on the openings of vertical mesopores (∼5 nm) leading to 2 nm nanogaps between the gold nanoparticles. The gold nanoparticle arrays showed red-shifted localized surface plasmon resonance spectra due to strong couplings between close-packed gold. The dense on-substrate 2 nm plasmonic nanogaps lead to highly enhanced local electric field and excellent macroscopic uniformity in SERS.
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