Fig. 1. Plasmonic nanopore based on metal micro-nano structure. (a) Nanowell-nanopore structure^[13]; (b) nanoslit cavity^[16]; (c) bullseye structure^[25]

Fig. 2. Plasmonic nanopore based on nanogap. (a) Bowtie shaped structure^[36]; (b) inverted-bowtie shaped structure^[10,29]; (c) gap of nanourchin and gold nanohole^[52]

Fig. 3. Plasmonic nanopore based on glass nanopipette. (a) Gold nanoporous sphere^[53]; (b) metal nanostructures modified nanopores^[60]

Fig. 4. Fluorescence detection based on nanowell-nanopore structure^[13] (local field excited by the nanowell structure is used for fluorescence excitation. When the fluorescent dye-labeled samples flow through the nanowell, the fluorescence signals are excited and detected to obtain the information of testing samples)

Fig. 5. Typical label-free optical sensing scheme. (a) SERS detection based on nanogap of nanourchin and plasmonic nanohole^[51]; (b) plasmon resonance shift sensing based on bowtie shaped nanoantenna^[30]

Fig. 6. Signal detection strategies based on optical and electrical sensing combination. (a) Photoelectric synchronization detection based on inverted-bowtie shaped aperture^[29]; (b) combined optical and electrical combination sensing based on SIBA mechanism of double nanohole^[43]