Photograph by Kim Lee Schmidt

Chemical sensors at places like airports are pretty good at detecting TNT and some other explosives, but they’re lousy at detecting some others that are even more powerful. That may soon change thanks to research happening in Gottwald Center for the Sciences this fall. The research is so promising it attracted the nationally prestigious Barry Goldwater Scholarship for the UR senior working on it.

Arjun Jaini, ’18, and chemistry professors Mike Leopold and Carol Parish are examining the possibility of using a chemical process called halogen bonding for sensing highly combustible compounds such as RDX, PDTN, and HMX, which require sophisticated techniques to detect. Jaini pictures a portable, hand-held, battery-powered sensor that would be simple to use and widely available to security personnel everywhere from battlefields to the transportation infrastructure.

Halogen bonding is a recently discovered phenomenon where atoms connected to a halogen pull the electron density away, creating a region of positive density called a sigma hole. This positively charged sigma hole attracts nearby electron-rich atoms much the same way that hydrogen bonding attracts the hydrogens to nearby oxygen in water.

In the spring, Jaini worked out calculations in Parish’s laboratory that showed it should be possible to use halogen bonding to detect the vapors of explosive compounds. Over the summer and fall, he’s doing experimental tests in Leopold’s laboratory to confirm the computational proof-of-principle and determine the conditions under which a sensor prototype would sense explosives.

“What was cool about the first calculations was that I showed that, with halogen bonding, [these compounds] were all on an equal playing field for being detected,” he said. “They were all very close in terms of whether this detection system could work. That’s really what started this whole pursuit of actually building the sensor.”