Label-Free Microrefractometry of Interfacial Processes Using Fluorescent Smart Coverslips

TL;DR

This paper presents a label-free, real-time microrefractometry technique using fluorescent smart coverslips that detect local interfacial changes via emission shifts, applicable in nanobiophotonics and chemical sensing.

Contribution

Introduction of smart coverslips with fluorescent nanobeads enabling sensitive, label-free interfacial measurements through supercritical-angle fluorescence refractometry.

Findings

Real-time RI sensing with single back-focal-plane images.

Nanometric thin-film height measurements without multi-angle acquisition.

Broad applicability to nanobiophotonics and materials analysis.

Abstract

Molecular dipoles near interfaces emit highly directional radiation due to near-field interactions, making surface-bound fluorophores sensitive probes of local physicochemical changes. We introduce smart coverslips, stably coated with uniform, brightly fluorescent nanobead films, that exploit refractive-index-dependent emission shifts for sensitive micro-refractometry in small volumes. Supercritical-angle fluorescence refractometry uses single back-focal-plane images to allow us real-time RI sensing and nanometric thin-film height measurements without the need for multi-angle or multi-wavelength acquisition. Our fast, label-free, and non-invasive approach allows measurements of thin-film properties and monitoring of interfacial dynamics on a standard inverted microscope and is broadly applicable to nanobiophotonics, chemical sensing, and in-situ materials analysis.