Scientists have designed a new type of gas sensor that can tell apart “mirror image” versions of the same smell molecule, even at very low concentrations. By coating carbon nanotubes with custom-built sugar-based receptors, the sensor can spot tiny structural differences in common volatile compounds like terpenes. This approach could help power future “electronic noses” for non-invasive medical diagnostics, environmental monitoring, and quality control in food, beverages, and fragrances.

Researchers have created a new gas sensor that can tell apart mirror-image versions of the same molecule in the air. This ability could help improve future medical tests, environmental monitoring, and quality checks in perfume and food production.

The new system adds special sugar-based coatings to tiny sensors, so they can tell apart air molecules that are almost identical. Developed by Ariel Shitrit and Yonatan Sukhran, under the supervision of Prof. Shlomo Yitzchaik and Prof. Mattan Hurevich from Hebrew University, it helps identify different types of air components that usually look the same at the molecular level.

The researchers attached specially designed sugar molecules to the tiny carbon nanotube sensors. These custom sugars create a very precise chemical “architecture” around the sensor, so it can even pick up and interact with very weakly binding scent molecules, such as certain plant-derived chemicals.
This design both holds the sensing molecules in place on the nanotubes and helps them “talk” to the chemicals in the air. In the study, the upgraded sensors clearly told apart different mirror-image forms of the scent molecules limonene and carvone, but did not react to very similar forms of another molecule called α-pinene.

The sensors were able to detect the (–)-limonene version of the molecule at extremely low levels—down to 1.5 parts per million. That’s about ten times more sensitive than many similar sensing methods reported so far.

Using electrical measurements together with advanced computer simulations, run in collaboration with the Technical University of Dresden and Friedrich Schiller University Jena in Germany, the team showed how the system tells mirror-image molecules apart. The two versions of each molecule stick and interact slightly differently with the sugar-coated nanotube surface. These tiny differences affect how electrons move into the nanotubes, which shows up as a clear change in the sensor’s electrical signal.

By looking at how different receptor designs worked in the sensors, the researchers could see which design features led to better selectivity. These insights into “structure versus performance” could help scientists design better artificial smell receptors in the future.

The work is part of a European consortium, SMELLODI, that investigates links between body odor, smell perception, and emotional and physiological states. For this goal, non-invasive analysis of VOC mixtures, including chiral components, is important.

Because this sugar-based receptor system is easy to customize, it could be used to build sensor arrays where each tiny sensor is tuned to detect a different group of airborne chemicals. In the future, these sensor arrays could be built into “electronic noses” for things like breath tests to help diagnose disease, tracking how an illness changes over time, or checking flavor and aroma in food and drinks.

Turning sugar molecules that normally dissolve in water into a useful material for sensing gases was a big chemical and engineering challenge. The team solved it by creating a two-part system: adjustable sugar-based receptors attached to carbon nanomaterials. This setup can be fine-tuned by changing the basic sugar “frame” and the chemical groups attached to it.

Looking ahead, the researchers say that computer-based design tools — including advanced physics calculations and machine learning — could help create new types of receptors and allow the sensors to detect an even wider range of airborne molecules and their mirror-image forms.