Issue 2, 2023

High-specificity molecular sensing on an individual whispering-gallery-mode cavity: coupling-enhanced Raman scattering by photoinduced charge transfer and cavity effects

Abstract

Optical whispering-gallery-mode (WGM) cavities have gained considerable interest because of their unique properties of enhanced light–matter interactions. Conventional WGM sensing is based on the mechanisms of mode shift, mode broadening, or mode splitting, which requires a small mode volume and an ultrahigh Q-factor. Besides, WGM sensing suffers from a lack of specificity in identifying substances, and additional chemical functionalization or incorporation of plasmonic materials is required for achieving good specificity. Herein, we propose a new sensing method based on an individual WGM cavity to achieve ultrasensitive and high-specificity molecular sensing, which combines the features of enhanced light–matter interactions on the WGM cavity and the “fingerprint spectrum” of surface-enhanced Raman scattering (SERS). This method identifies the substance by monitoring the Raman signal enhanced by the WGM cavity rather than monitoring the variation of the WGM itself. Therefore, ultrasensitive and high-specificity molecular sensing can be accomplished even on a low-Q cavity. The working principles of the proposed sensing method were also systematically investigated in terms of photoinduced charge transfer, Purcell effect, and optical resonance coupling. This work provides a new WGM sensing approach as well as a strategy for the design of a high-performance SERS substrate by creating an optical resonance mode.

Graphical abstract: High-specificity molecular sensing on an individual whispering-gallery-mode cavity: coupling-enhanced Raman scattering by photoinduced charge transfer and cavity effects

Supplementary files

Article information

Article type
Communication
Submitted
29 sep. 2022
Accepted
22 nov. 2022
First published
22 nov. 2022

Nanoscale Horiz., 2023,8, 195-201

High-specificity molecular sensing on an individual whispering-gallery-mode cavity: coupling-enhanced Raman scattering by photoinduced charge transfer and cavity effects

X. Fan, R. Wang, M. Li, X. Tang, C. Xu, Q. Hao and T. Qiu, Nanoscale Horiz., 2023, 8, 195 DOI: 10.1039/D2NH00450J

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