A Breath of Fresh Tech — New “Electronic Nose” Sniffs Out Gases with Unprecedented Precision

27.06.2025

Gas sensor based on MINT-functionalised carbon nanotubes. Credit: Emilio M. Pérez.

Researchers at IMDEA Nanociencia design carbon nanotube sensors with extreme sensitivity and selectivity towards volatile organic compounds.
When assembled into an array, the sensing layers can discriminate a specific analyte, demonstrating its capability to operate as an electronic nose.
This proof-of-concept device can detect ammonia, nitric oxide, isopropanol, acetone and other chemical vapors in concentrations below 100 ppb.

Madrid, June 27^th, 2025. A team of researchers at IMDEA Nanociencia institute and Università Cattolica del Sacro Cuore has unveiled a new class of gas sensors based on MINT-functionalized carbon nanotubes, offering unprecedented precision in detecting and distinguishing volatile organic compounds. This "electronic nose" is made of a tailored array of chemiresistors to sense gases like ammonia, nitrogen dioxide or acetone vapours at room temperature, paving the way for low-power environmental monitors and wearable breath diagnostics.

Single-walled carbon nanotubes are ideal materials for sensing due to their high surface area, but their extreme sensitivity has long come with a downside: poor selectivity. To address this, researchers have "dressed" carbon nanotubes with ring molecules to improve their ability to discriminate between chemical compounds. These derivatives of carbon nanotubes, known as Mechanically Interlocked Carbon Nanotubes (MINTs), provide a way to introduce chemical functionalities onto carbon nanotubes without altering their intrinsic structure.

The MINT-based chemiresistors responded significantly better to target gases—including NH₃, EtOH, IPA, benzene, NO₂, acetone, and NaClO—than unmodified carbon nanotubes, even at low concentrations (10–200 ppm). Researchers proved their detection limit, being below tens of parts-per-billion (ppb).

Assembled into an array, these sensors behave like an artificial olfactory system, able to selectively identify specific analytes despite the presence of potential interferences. For instance, ammonia was successfully distinguished from a range of other vapors. One optimized sensor layer even showed up to 10× higher sensitivity and faster response times, simply by reducing the film thickness.

The research, published in the Journal of the American Chemical Society constitutes a proof-of-concept e-nose, that not only demonstrates the power of MINT-based sensors for complex gas detection but also highlights their customizability. With synthetic control over the structure of the interlocked molecules, researchers can finely tune the sensor’s properties, opening a new frontier in the design of smart, selective, and scalable electronic noses.

This work is a collaboration between researchers at IMDEA Nanociencia, led by Prof. Emilio M. Pérez, and Università del Sacro Cuore, led by Prof. Luigi Sangaletti. It is partially funded by the accreditation Excellence Severo Ochoa awarded to IMDEA Nanociencia (CEX2020-001039-S).

Keywords: carbon nanotubes, SWNTs, MINTs, VOCs, electronic nose, gas sensing, Raman, artificial olfaction, PCA, UMAP, machine learning, rotaxane, MINTs sniff out VOCs

Glossary:

Carbon nanotube: a hollow cylindrical molecule composed entirely of carbon atoms, with diameter of less than 2 nanometres. They can be single-walled (SWNTs) or multi-walled.
MINTs: derivatives of carbon nanotubes that are mechanically interlocked with other ring organic molecules.
Chemiresistor: a material that changes its electrical resistance in response to changes in the nearby chemical environment

Reference

Michele Galvani, Alejandro López-Moreno, Natalia Martín Sabanés, Sylwia Parzyszek, Michele Zanotti, Sonia Freddi, Emilio M. Pérez, and Luigi Sangaletti, Efficient Implementation of MINT-Based Chemiresistor Arrays for Artificial Olfaction. Journal of the American Chemical Society 2025. DOI: https://doi.org/10.1021/jacs.5c07781

Link to IMDEA Nanociencia Repository: https://hdl.handle.net/20.500.12614/4016

Contact:

Prof. Emilio Pérez
emilio.perez [at] imdea.org
https://nanociencia.imdea.org/chemistry-of-low-dimensional-materials/home
Bluesky: @emilioperezlab.bsky.social

IMDEA Nanociencia Dissemination and Communication Office
divulgacion.nanociencia [at]imdea.org

Source: IMDEA Nanociencia.

IMDEA Nanociencia Institute is a young interdisciplinary research Centre in Madrid (Spain) dedicated to the exploration of nanoscience and the development of applications of nanotechnology in connection with innovative industries.