A chemical sensing system developed by engineers at the University of Connecticut is believed to be the first of its kind capable of detecting vapors²（蒸汽） from buried landmines³ and other explosive devices with the naked eye rather than advanced scientific instrumentation. The research was first reported in the May 11, 2012 online edition of Advanced Functional⁴ Materials.

 

The key to the system is a fluorescent⁵（荧光的） nanofiberous film that can detect ultra-trace levels of explosive vapors and buried explosives when applied⁶ to an area where explosives are suspected. A chemical reaction marking the location of the explosive device occurs when the film is exposed to handheld ultraviolet light.

 

The system can detect nitroaromatics such as those found in TNT and 2,4-DNT (the military's primary explosive and the principle components⁷ in landmines) as well as the elements used in harder to detect plastic explosives such as HMX, RDX, Tetryl, and PETN. The ultra-sensitive system can detect elements at levels as low as 10 parts per billion (TNT), 74 parts per trillion (Tetryl), 5 ppt (RDX), 7 ppt (PETN) and 0.1 ppt (HMX) released from one billionth of a gram of explosive residue⁸.

 

If there is no explosive vapor¹ present, the recyclable film retains a bright fluorescent cyan blue color when exposed to ultraviolet light. If explosive molecules⁹ are present, the fluorescence is quenched¹⁰ and a dark circle identifying the threat forms on the film within minutes.

 

"Our initial results have been very promising," says UConn Dr. Ying Wang, who developed the system as a chemical engineering doctoral student working under the supervision¹¹ of UConn Associate Engineering Professor Yu Lei. "We are now in the process of arranging a large-scale field test in Sweden."

 

Rather than using sophisticated chemical modifications¹² or costly¹³ synthetic¹⁴ polymers in preparing the sensing material, UConn scientists prepared their ultra-thin film by simply electrospinning pyrene with polystyrene in the presence of an organic salt (tetrabutylammonium hexafluorophosphate or TBAH). This resulted in a highly porous¹⁵ nanofiberous membrane¹⁶ that absorbs explosive vapors at ultra-trace levels quickly and reliably. The film also has excellent sensitivity against common interferences such as ammonium nitrate and inorganic¹⁷ nitrates. Initial vapor detection took place within seconds with more than 90 percent fluorescent quenching¹⁸ efficiency within six minutes.

 

According to the United Nations, there are an estimated 110 million active landmines hidden underground in 64 countries around the world. It is estimated that as many as 25,000 people are maimed or killed by landmines each year across the globe. The mines not only threaten people's lives, they can paralyze communities by limiting the use of land for farming or roads for trade.

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