# Probing supramolecular structures in solution by resonant energy transfer in the X-ray range

## TL;DR

This paper introduces a new X-ray technique to study how ions cluster in water at the nanoscale.

## Contribution

The first FZRET spectroscopy experiment in a liquid microjet enables atomic-resolution analysis of supramolecular structures in solution.

## Key findings

- FZRET reveals inhomogeneous ion distribution in water.
- Nm-sized ionic clusters are observed at 4.1 M concentration.
- The technique provides atomic spatial resolution for supramolecular structures.

## Abstract

Supramolecular structures in solution are probed using Far-Zone Resonant Energy Transfer (FZRET) in an aqueous potassium acetate microjet. This advanced X-ray spectroscopic technique relies on the resonant energy transfer between donor atoms, i.e. core-ionised potassium ions, and acceptor atoms a few nm away. These experiments reveal an inhomogeneous distribution of ions in water, and are consistent with the presence of nm-sized ionic clusters at 4.1 M concentration.

The first Far-Zone Resonant Energy Transfer (FZRET) spectroscopy experiment in liquid microjet provides quantitative characterisation of supramolecular organisation in solution with atomic spatial resolution.