Work

Optical Control of Forster Resonance Energy Transfer in a Single Ionic-Liquid Microdroplet

Year: 2026

Type: article

Abstract: Controlling intermolecular distance in microscale environments is an effective strategy for regulating photophysical processes such as Förster resonance energy transfer (FRET). However, direct control of the local molecular concentration required for this purpose remains challenging due to limited approaches. Here, we demonstrate that laser-generated ionic-liquid (IL) microdroplets provide a platform for optically controlling molecular concentration. Optical tweezers induce local liquid-liquid phase separation in an aqueous solution of tributyl-n-octylphosphonium bromide, producing a single microdroplet. Fluorescence-energy donor and acceptor molecules are rapidly coextracted and concentrated within the droplet, and their close proximity induces FRET. Notably, fluorescence lifetime analysis reveals two donor populations, corresponding to FRET-inactive and FRET-active species, with the fraction of the latter increasing during droplet growth. These results demonstrate that FRET enhancement arises from IL-mediated nanoscale colocalization rather than homogeneous concentration effects.

Source: The Journal of Physical Chemistry Letters

DOI: 10.1021/acs.jpclett.6c01744

Authors: Keigo Sarashi, Kosuke Nakatsu, Yasuyuki Tsuboi, Ken-ichi Yuyama

Institution: Osaka Metropolitan University

Language: English

Topic: Spectroscopy and Quantum Chemical Studies

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,500

Funder: Japan Society for the Promotion of Science