Method finds picogram of explosive in complex mixtures

A team of researchers has found a method of using receptor-free nanomechanical infrared spectroscopy to increase recognition of chemical molecules in explosive mixtures.

Detecting trace amounts of explosives with mixed molecules is claimed to present a formidable challenge for sensors with chemical coatings. The nanomechanical infrared spectroscopy used by the University of Alberta research team is said to provide higher selectivity in molecular detection by measuring the photothermal effect of the absorbed molecules.

Dr Thomas Thundat, from the Department of Chemical and Materials Engineering said that the spectroscopy looks at the physical nature of the molecule.

‘Even if there are mixed molecules, we can detect specific molecules using this method,’ he said in a statement .

Post-doctoral fellow Seonghwan Kim explained that conventional sensors based on coatings generally cannot detect specific molecules in complex mixtures if the concentration of interfering molecules is five times greater than the target molecules.

The detection sensitivity and selectivity are said to be increased using the high-power infrared laser because the photothermal signal comes from the absorption of infrared photons and non-radiative decay processes.

Using this method, a few trillionths of a gram of explosive molecules can now be detected in a complex mixture even if there is a higher concentration of other interfering molecules. 

The research team’s current work looks at detecting biomolecules and hydrocarbons in the oil industry and nerve gas stimulants (DMMP), which can be found in household radiators, gasoline, and fabric softeners, for example.

The team also hopes to develop a hand-held device for chemical detection that could be utilized in areas such as security, health care and environmental protection. 

The research team included post-doctoral fellows Dongkyu Lee and Xuchen Liu, research associate Charles Van Neste, and visiting professor, Sangmin Jeon from South Korea’s Pohang University.

Their findings are published in Scientific Reports.