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Nanostructures made of two-dimensional (2D) materials have become in recent years the flagship of nanofluidic discoveries. By confining liquids down to a few molecular layers, anomalies in molecular transport and order have been revealed. Currently, only indirect and ensemble averaged techniques have been able to operate in such extreme confinements, as even the smallest molecular fluorophores are too bulky to penetrate state-of-the-art single-digit nanofluidic systems6. This strong limitation calls for the development of novel optical approaches allowing for the direct molecular imaging of liquids confined at the nanoscale. Here, we show that native defects present at the surface of hexagonal boron nitride (hBN) - a widely used 2D material - can be used as molecular probes in liquid, without compromising the atomic smoothness of their host material. We first demonstrate that native surface defects are readily activated through interactions with organic solvents and behave as quantum emitters. Correlated activation of neighboring defects reveal single-molecule dynamics at the interface, while defect emission spectra offer a direct readout of the dielectric properties of the liquid medium. We then harvest these effects in atomically smooth slit-shaped van der Waals channels, revealing molecular dynamics and order under nanometre-scale confinement. Liquid-activated native defects in pristine hBN bridge the gap between solid-state nanophotonics and nanofluidics and open up new avenues for nanoscale sensing and optofluidics.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Atomic scale, new properties, optical approaches

Date published: 2023-08-31

Publisher: Springer Science and Business Media LLC

Journal:

• Nature Materials (ISSN: 14764660) vol. 22 issue. 10 p. 1236-1242

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Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1038/s41563-023-01658-2

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Updated at: 2025-02-28 08:30:45 +0900

Published on MDR: 2025-02-28 08:30:45 +0900