Ultra-Low Intensity Light-Driven Ionic Conductivity through a Plasmonic Nanopore

Solid-state nanopore devices with plasmonic nanoantennas are powerful tools that allow for working with individual particles and molecules in solution as well as providing light-induced control of ionic current flow through them. However, the ionic current flow manipulation by light still requires high power densities and, thus, results in the optical heating of the nanopore. Here, we solve this problem by using a 5 nm nanopore in the gap of a plasmonic bow-tie nanoantenna on a SiN x membrane irradiated by a broadband spectrum of incident light. In this regime, photons are not only strongly localized around the nanopore but also efficiently excite and trap charge carriers on defect states in the band gap of the material of the nanopore walls. As a result, ionic current flow modulation is achieved with several orders of magnitude lower power densities (around 0.035 W/cm2) from a white-light lamp than in previous works employing spectrally narrow laser sources (100–105 W/cm2). The lamp irradiation causes a 21% increase in conductivity for a nanopore without a nanoantenna and a 35% increase in conductivity for a nanoantenna-decorated nanopore at the same power of irradiation. The revealed low-intensity approach for ionic current control is preferable for the study of biological objects.