Monomeric gold (Au) and silver (Ag) nanoparticle (NP) arrays are self‐assembled uniformly into anodized aluminium oxide (AAO) nanopores with a high homogeneity of greater than 95%, using ultrasonication. The monomeric metal NP array exhibits asymmetric plasmonic absorption due to Fano‐like resonance as interpreted by finite‐difference time‐domain (FDTD) simulation for the numbers up to 127 AuNPs. To examine gap distance‐dependent collective‐plasmonic resonance, the different dimensions of S, M, and L arrays of the AuNP diameters/the gap distances of ≈36 nm/≈66 nm, ≈45 nm/≈56 nm, and ≈77 nm/≈12 nm, respectively, are prepared. Metal NP arrays with an invariable nanogap of ≈50 nm can provide consistent surface‐enhanced Raman scattering (SERS) intensities for Rhodamine 6G (Rh6G) with a relative standard deviation (RSD) of 3.8–5.4%. Monomeric arrays can provide an effective platform for 2D hot‐electron excitation, as evidenced by the SERS peak‐changes of 4‐nitrobenzenethiol (4‐NBT) adsorbed on AgNP arrays with a power density of ≈0.25 mW µm‐2 at 514 and 633 nm. For practical purposes, the bacteria captured by 4‐mercaptophenylboronic acid are found to be easily destroyed under visible laser excitation at 514 nm with a power density of ≈14 mW µm‐2 for 60 min using Ag due to efficient plasmonic‐electron transfer.

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Controlled self-assembly of different numbers of gold nanoparticles (AuNPs) in the highly ordered cylindrical anodic aluminum oxide nanopores was achieved by a facile ultrasonication method. The surface plasmon resonance bands became red-shifted by increasing the number of nanoparticles (N), in the top view, from monomer M1 (N = 1) to multimers of M2 (N = 3 ± 1), M3 (N = 5 ± 1), and M4 (N = 7 ± 1). The numerical calculations of the M2 model showed the best match of 2 nm nanogap among 28 nm diameter AuNPs in 53 nm diameter nanopores. When the number of AuNPs inside the nanopores increased, more hotspots were generated, which induced the plasmon-driven photocatalysis on AuNP clusters at the incident visible light of 633 nm. The enhanced photocatalytic reaction of 4-nitrobenzenethiol was observed after sequentially increasing the number of AuNPs, which began at M3 and was maximum for M4. The M3 configuration could be a magical number of AuNP clusters for the nanogap-induced photocatalysis under 633 nm irradiation (∼0.2 mW) for 12 min. Our methods should be helpful in adjusting photocatalysis by varying the numbers of nanoparticles inside the tunable nanopores.

Nanoporous anodic aluminum oxide internalized with gold nanoparticles was utilized as an integrated platform miniaturized for consecutively performing on-chip PCR and downstream detection of the amplified product of a 183 bp eaeA gene fragment from Escherichia coli O157:H7 using surface-enhanced Raman scattering (SERS).