Mattan Hurevich and Shlomo Yitzchaik, The Hebrew University of Jerusalem, Israel, address a key challenge in chemical sensing: the enantioselective detection of weakly interacting volatile organic compounds (VOCs), a capability crucial for applications ranging from analytical environmental monitoring to pharmaceutical quality control. In a recent Chemistry – A European Journal paper, they and their colleagues report a chemiresistive carbon-nanotube sensor functionalized with chiral monosaccharide receptors, enabling highly selective, low-concentration detection of complex odorant mixtures.

 

What did you do?

We developed an enantioselective sensor for volatile organic compounds (VOCs) that displays chiral discrimination in the ppm concentration range and selectivity toward minimally functionalized terpenoids. The sensor features substituted monosaccharides as molecular olfactory receptor—multichiral, multivalent, and multi-functionalized molecules capable of binding even weakly interacting VOCs.

The sensing was achieved by fabricating a chemiresistive device using dielectrophoretic deposition of single-walled semi-conducting carbon nanotubes (SWCNTs) modified with aromatic-group-substituted monosaccharide receptors. The multichiral scaffold and the architecture of monosaccharide receptor substituents dictated the enantioselectivity, selectivity, and sensitivity of the sensor.

This two-component system offers high versatility and tunability because a wide range of monosaccharide scaffolds and substituent architectures can be used as receptor components.

 

Why are you interested in this?

We are part of a European consortium (EU Horizon 2020 SmellODI Pathfinder) that aims to link the chemical composition of body odor, the perception of smell, and the emotional and physiological states. Developing non-invasive gas analysis methods was crucial for the detection of underlying pathologies, mental and physical stress, and more.

Although some platforms for the detection of VOCs exist, eNose devices that enable chiral discrimination of VOCs remain scarce. Since most VOCs lack prominent functional groups and have highly similar structural features, state-of-the-art methods either display poor discrimination of different VOCs or require multiple complementary techniques and complex analyses.

We introduced a novel class of highly tunable biorecognition layers that have vast potential for the enantioselective detection of VOCs with minimal structural differences in complex gaseous mixtures.

 

What is new and cool about it?

We employed selectively substituted monosaccharides, which are common synthetic intermediates in glycan synthesis, to produce unique SWCNT-adsorbed VOC receptors. By building upon the monosaccharide scaffold, the inherent multichirality and multivalency are preserved, while the aromatic substituents introduce new unconventional apolar intermolecular interactions that are missing in native polysaccharides. This enabled us to maximize discrimination between VOC enantiomers and similar terpenoids with minimal structural differences.

The nice thing about the suggested architecture is that the same aromatic substituents anchor the receptor to the SWCNTs, in addition to mediating interaction with the VOCs. The multitude of possible combinations of monosaccharide scaffolds and substituents enables the fabrication of innumerable VOC sensors with different selectivity, enantioselectivity, and sensitivity.

 

Why did you not use polysaccharides?

Polysaccharides are major interaction mediators in biological systems. However, their solubility, compatibility with common sensing materials, structural complexity, and predominantly polar and H-bonding interactions hinder their use in gas sensing applications. We addressed this challenge by capitalizing on synthetic aromatically substituted monosaccharides.

We have only scratched the surface of the possible combinations of monosaccharide scaffolds, and substituent composition and arrangement. Future machine learning-directed design of molecular olfactory receptors may further expand the capabilities of this platform to produce unique de novo receptors.

 

What are your key findings?

We used two galactosides decorated with aromatic groups as a recognition layer and tested the sensor using three pairs of terpene enantiomers: limonene, carvone, and α-pinene, testing both the (+) and (–) forms of each compound. We showed that this novel gas sensor displays chiral discrimination as low as 1.5 ppm, an order of magnitude lower than comparable platforms reported to date.

Moreover, computational efforts and the strategic choice of analytes and receptors, done in collaboration with the Technical University of Dresden and Friedrich Schiller University Jena in Germany, enabled us to find a link between the structural features of the receptor and the selectivity of the gas sensor. We know that even the slightest changes in VOCs structure and gas composition have a substantial effect on the way we perceive smell, e.g., the two Limonene enantiomers are associated with either orange or lemon odors.

Fine-tuning of receptor features to accommodate the minute differences between similar VOCs can be envisioned. This serves as a stepping stone for the rational design of molecular olfactory receptors for future analyte-specific gas enantioselective sensors.

 

What specific applications do you imagine for such sensors?

We envision incorporating this novel class of gas sensors into eNose devices, with applications ranging from predicting the taste of whiskey to assessing the severity of a disease. To realize the full potential of this platform, predictive engineering of molecular olfactory receptors using quantum mechanical calculations could become a powerful tool for adapting the sensing system to new applications.

 

What part of your work was the most challenging?

First, transforming water-soluble saccharides into a gas-phase sensing platform was a conceptual and synthetic challenge. The designed receptor had to be both compatible with carbon-based nanomaterials and apolar gaseous VOCs, while preserving the key features of the parent compound.

Second, fine-tuning the gas flow setup for the reliable and reproducible analyte vapor exposure of the sensor was a major engineering challenge. The high sensitivity and enantioselectivity of the gas sensors at extremely low concentrations necessitated a robust control over vapor concentration.

 

Thank you very much for sharing these insights.

The paper they talked about:

• Monosaccharide-Derived Enantioselectivity in SWCNT Chemoresistive VOC Sensing,
  Ariel Shitrit, Yonatan Sukhran, Nina Tverdokhleb, Li Chen, Arezoo Dianat, Rafael Gutierrez, Sabine Körbel, Alexander Croy, Gianaurelio Cuniberti, Mattan Hurevich, Shlomo Yitzchaik,
  Chem. Eur. J. 2025.
  https://doi.org/10.1002/chem.202502553

 

Mattan Hurevich is an associate professor at the Institute of Chemistry and the Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Safra Campus, Givat Ram, Jerusalem, Israel.

Shlomo Yitzchaik is a professor at the Institute of Chemistry and the Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Safra Campus, Givat Ram, Jerusalem, Israel.

 

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