Control of particle trapping in a magnetoplasmonic nanopore

TL;DR

This paper proposes a magneto-plasmonic nanopore system that uses magnetic forces to trap nanoparticles, enhancing single-molecule detection capabilities by creating a highly confined electromagnetic field.

Contribution

It introduces a hybrid magneto-plasmonic nanopore design that enables efficient nanoparticle trapping with stronger forces and improved electromagnetic field confinement for biosensing.

Findings

Trapping force up to 28 pN for 10 nm magnetite nanoparticles.

Enhanced electromagnetic field intensity up to 230 times at near-infrared wavelengths.

Potential for improved biosensors and single-molecule analysis.

Abstract

Plasmonic nanopores are extensively investigated as single molecules detectors. The main limitations in plasmonic nanopore technology are the too fast translocation velocity of the molecule through the pore and the consequent very short analysis times, as well as the possible instabilities due to local heating. The most interesting approach to control the translocation of molecules and enable longer acquisition times is represented by the ability to efficiently trap and tune the motion of nanoparticles that can be used to tag molecules. Here, we theoretically investigate the performance of a magneto-plasmonic nanopore prepared with a thin layer of cobalt sandwiched between two gold layers. A nanopore is then coupled with a translocating magnetic nanoparticle. By setting the magnetic configuration of the cobalt layer around the pore by an external magnetic field, it is possible to generate a nanoscale magnetic tweezer to trap the nanoparticle at a specific point. Considering a 10 nm magnetite nanoparticle we calculate a trapping force up to 28 pN, an order of magnitude above the force that can be obtained with standard optical or plasmonic trapping approaches. Moreover, the magnetic force pulls the nanoparticle in close contact with the plasmonic nanopore's wall, thus enabling the formation of a nanocavity enclosing a deeply sub-wavelength confined electromagnetic field with an average field intensity enhancement up to 230 at near-infrared wavelengths. The presented hybrid magneto-plasmonic system points towards a strategy to improve nanopore-based biosensors for single-molecule detection and potentially for analysis of various biomolecules.