Organophosphorus (OP) nerve agents such as sarin are highly toxic, making rapid detection important for public safety. Current detection methods, including chromatography-mass spectrometry and ion mobility spectrometry, are accurate but often require bulky equipment and laboratory analysis, limiting their applications for rapid on-site detection.

In a study published in Chemical Engineering Journal, a team led by Prof. ZHANG Hongwen from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences developed a molecular probe-based surface-enhanced Raman spectroscopy (SERS) sensor which can rapidly detect trace amounts of sarin and other OP nerve agents.

Researchers combined SERS technology with a molecular probe designed to selectively capture OP agents. The probe, pyridylamidoxime-mercapto (PAOM), contains an oxime group that reacts with the target molecules and a thiol group helps attach the probe to the gold surface of SERS chip. A pyridine ring within the probe molecule also enhances Raman signal, making small amounts of the target easier to be detected.

Researchers tested three versions of the probe and found that the para isomer, p-PAOM, showed the strongest interaction with OP agents and the lowest reaction energy barrier.

Tests with a portable Raman spectrometer showed that the sensor could detect sarin in liquid samples in less than 20 seconds, with a detection limit of 10 ppb. It showed good selectivity in the presence of common interfering substances. Besides, it remained effective at temperatures of up to 100 °C and across a pH range of three to 12.

This work provides a foundational framework for designing SERS chips specifically targeting OP nerve agents, paving the way for rapid on-site analysis, field-portable trace detection, and precise identification in real-world scenarios.