Reversible nanopore sealing and in situ iron oxide nanoparticle synthesis on thin silicon nitride membranes

TL;DR

This paper demonstrates in-situ synthesis and reversible sealing of iron oxide nanoparticles within silicon nitride nanopores, verified by multiple microscopy techniques, advancing nanopore-based biosensing and photonics applications.

Contribution

It introduces a method for in-situ iron oxide nanoparticle synthesis inside nanopores with reversible sealing, independent of fabrication technique.

Findings

Nanopores seal within milliseconds to seconds across various sizes.

Iron oxide particles are verified as magnetite and maghemite.

Sealing and recovery are consistent across fabrication methods.

Abstract

We report in-situ synthesis of iron oxide particles inside silicon nitride nanopores via a chemical reaction, monitored by current readout. Nanopores were formed by electroporation on glass chips (diameters from 1.7 to 11.3 nm), transmission electron microscopy (TEM) drilling (diameters from 6.5 to 64.6 nm), or hydrofluoric acid (HF) etching (diameters from 12.6 to 36.2 nm) in 5 to 20 nm thick membranes. Nanopores seal on timescales from ~1 ms to ~3.6 s, across a range of sizes and concentrations. We show single and ~5-pore arrays, as fabricated, after sealing, and after cleaning and pore recovery. These results are independent of fabrication method. Energy dispersive X-ray spectroscopy (EDS), aberration-corrected scanning TEM (AC-STEM), and powder X-ray diffraction (XRD) verify the synthesis of mixed magnetite and maghemite iron oxide. This work advances nanoparticle-nanopore chips for applications in biosensing, plasmonics and photonics when position and size control is required.