Ultra Electron Density Sensitivity for Surface Plasmons

TL;DR

This paper demonstrates that surface plasmons are highly sensitive to electron density changes, enabling detection of single ions at extremely low concentrations through a novel imaging method.

Contribution

It introduces a new approach to enhance electron density sensitivity in surface plasmon resonance, allowing detection of single ions at attomolar concentrations.

Findings

Surface plasmons involve only a tiny fraction of surface electrons.

Electron density can be reduced to about 10 μm^-2, achieving high sensitivity.

The developed imaging method detects single anions at 1 aM concentration.

Abstract

We investigate surface plasmons from a solid-state standpoint and highlight their ultra electron density sensitivity. When a surface plasmon is excited on a planar gold film by an evanescent wave from 625 nm incident light, only a minute fraction of the surface electron density, approximately one thousandth, participates in the process. By introducing a noise-depressed surface potential modulation, we reduce the electron density to the order of 10 um-2, enabling electron sensitivity on the order of 0.1 e. As a practical application, we develop a surface plasmon resonance imaging method capable of detecting single anions in solution at a concentration of 1 aM.