We show that plasmonic solid-state nanopores with tunable hole diameter can be prepared via a photocatalytic effect resulting from the enhanced electromagnetic field inside a metallic ring on top of a dielectric nanotube. Under white light illumination, the plasmon-enhanced electromagnetic field induces a site selective metal nucleation and growth within the ring. We use this approach to prepare Au and bimetallic Au-Ag nano-rings and demonstrate the reduction of the initial inner diameter of the nanopore down to 4 nm. The tunability of the nanopore diameter can be used to enable optimized detection of single entities with different size. As proof-of-concept, we demonstrate the versatility of the platform to perform single object detection of dsDNA, and Au nanoparticles with a diameter down to 15 nm. Numerical simulations provide insights into the electromagnetic field distribution, showing that a field intensity enhancement of up to 104 can be achieved inside the nanopores. The field confinement inside the nanopores can be used to perform enhanced optical measurements, and to generate local heating, thereby modifying the properties of the nanopore. Such a flexible approach represents a valuable tool to investigate plasmon-driven photochemical reactions, and it can represent an important step forward towards the realization of new plasmonic devices.

Solid-state nanopores are a key platform for single-molecule detection and analysis that allow engineering of their properties by controlling size, shape, and chemical functionalization. However, approaches relying on polymers have limits for what concerns hardness, robustness, durability, and refractive index. Nanopores made of oxides with high dielectric constant would overcome such limits and have the potential to extend the suitability of solid-state nanopores toward optoelectronic technologies. Here, we present a versatile method to fabricate three-dimensional nanopores made of different dielectric oxides with convex, straight, and concave shapes and demonstrate their functionality in a series of technologies and applications such as ionic nanochannels, ionic current rectification, memristors, and DNA sensing. Our experimental data are supported by numerical simulations that showcase the effect of different shapes and oxide materials. This approach toward robust and tunable solid-state nanopores can be extended to other 3D shapes and a variety of dielectrics.