Leaf it Out

Coating the sticky surface of a leaf with paint and stamping it onto paper may have been our first artwork, but it also allowed us to see the patterns on the surface in a different way. Taking a vastly more complex, but perhaps similar approach, here researchers place a flexible nanofilm – made using a structure called a covalent organic framework – onto an entire cowpea plant (Vigna unguiculata). They then carefully analyse the film 'imprint' of the plant’s surface using mass spectrometry imaging to highlight specific chemicals, finding patterns of both natural and pollutant molecules on the leaves. Similar approaches can be used to take delicate chemical imprints of fingerprint residues, or slices of brain tissue. The sensitivity to the technique to specific chemicals may improve the diagnosis of similar imprints (touch preparations) of human tissue biopsies.

Written by John Ankers

John Ankers

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A former researcher in systems biology, John is now an online biology tutor and professional coach supporting the wellbeing of scientists and NHS professionals. He's writing, too, of course.

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• Image from work by Yizhu Xu and Xinzhou Wu, and colleagues
• National Key Laboratory of Green Pesticide, Key Laboratory of Natural Pesticide and Chemical Biology of the Ministry of Education, South China Agricultural University, Guangzhou, China
• Image originally published with a Creative Commons Attribution 4.0 International (CC BY-NC 4.0)
• Published in Science Advances, February 2026