Label-Free Selective Detection of Nitrobenzene Explosives at Picomolar Sensitivity in Single-Molecule Junctions

Area of Science:

• Analytical Chemistry
• Nanoscience
• Materials Science

Background:

• Developing ultrasensitive detection methods for nitroaromatic explosives is crucial for counterterrorism, environmental monitoring, and public safety.
• Single-molecule detection offers a pathway to unprecedented sensitivity and specificity in chemical analysis.

Purpose of the Study:

• To demonstrate selective and label-free detection of nitroaromatic explosives (TNT, DNT, TNP) at the single-molecule level.
• To investigate the mechanism enabling ultrasensitive detection using a specific molecular linker.

Main Methods:

• Utilized scanning tunneling microscopy break junction (STM-BJ) technique for single-molecule electrical measurements.
• Employed 4,4'-bipyridine-3-amine (Py-NH2) as a molecular linker to form single-molecule junctions.
• Analyzed conductance peak areas for concentration-dependent responses to nitroaromatic analytes.

Main Results:

• Achieved ultrasensitive, label-free detection of TNT, DNT, and TNP with limits of detection as low as 0.95 × 10^-12 M (TNT).
• Demonstrated selective detection in the presence of interfering compounds and environmental soil samples.
• Attributed detection sensitivity to Meisenheimer complex formation, suppressing molecular junction formation.

Conclusions:

• Single-molecule electrical sensing platforms show significant potential for highly sensitive, on-site detection of trace explosives.
• This technique is suitable for portable security screening and environmental surveillance systems.
• The mechanism involving Meisenheimer complex formation provides a robust basis for selective explosive detection.