Plasmonic Photochemistry as a Tool to Prepare Metallic Nanopores with Controlled Diameter for Optimized Detection of Single Entities

摘要

Plasmonic solid-state nanopores with tunable hole diameters can be preparedvia a photocatalytic effect resulting from the enhanced electromagnetic (EM)field inside a metallic ring on top of a dielectric nanotube. Under white lightillumination, the plasmon-enhanced EM-field induces a site-selective metalnucleation and growth within the ring. This approach is used to prepare Auand bimetallic Au–Ag nano-rings and demonstrate the reduction of the initialinner diameter of the nanopore down to 4 nm. The tunability of the nanoporediameter can be used to enable optimized detection of single entities withdifferent sizes. As a proof-of-concept, single object detection of doublestranded DNA (dsDNA) and Au nanoparticles (AuNPs) with a diameter downto 15 nm is performed. Numerical simulations provide insights into theEM-field distribution and confinement, showing that a field intensityenhancement of up to 10~4 can be achieved inside the nanopores. Thislocalized EM-field can be used to perform enhanced optical measurementsand generate local heating, thereby modifying the properties of the nanopore.Such a flexible approach also represents a valuable tool to investigateplasmon-driven photochemical reactions, and it can represent an importantstep toward the realization of new plasmonic devices.