Detection of Nanoparticles with a Frequency Locked Whispering Gallery Mode Microresonator

TL;DR

This paper demonstrates the detection of extremely small gold nanorods using a stabilized whispering gallery mode microresonator, achieving high signal-to-noise ratios and verifying single-particle detection with potential biomedical applications.

Contribution

It introduces a novel method for detecting nanorods smaller than previously possible using WGM sensing, with real-time, reliable measurements verified by electron microscopy.

Findings

Detected 39 nm x 10 nm gold nanorods with high SNR

Achieved real-time detection of single nanorods

Potential to detect proteins as small as 2 nm radius

Abstract

We detect 39 nm x 10 nm gold nanorods using a microtoroid stabilized via the Pound-Drever-Hall method. Real-time detection is achieved with signal-to-noise ratios up to 12.2. These nanoparticles are a factor of three smaller in volume than any other nanoparticle detected using WGM sensing to date. We show through repeated experiments that the measurements are reliable, and verify the presence of single nanorods on the microtoroid surface using electron microscopy. At our current noise level, the plasmonic enhancement of these nanorods could enable detection of proteins with radii as small as a = 2 nm.