A new approach for detection of explosives based on ion mobility spectrometry and laser desorption/ionization on porous silicon

We demonstrate a new way for detection ultralow concentration of explosives in this study. It combines an ion mobility spectrometry (IMS) and a promising method of laser desorption/ionization on silicon (DIOS). The DIOS is widely used in mass spectrometry due to the possibility of small molecule detection and high sensitivity. It is known that IMS based on laser ion source is a power method for the fast detection of ultralow concentration of organic molecules. However requirement of using high energy pulse ultraviolet laser increases weight and size of the device. The use of DIOS in an ion source of IMS could decrease energy pulse requirements and allows one to construct both compact and high sensitive device for analyzing gas and liquid probes. On the other hand mechanisms of DIOS in gas media is poorly studied, especially in case of nitroaromatic compounds. The investigation of the desorption/ionization on porous silicon (pSi) surface of nitroaromatic compounds has been carried out for 2,4,6-trinitrotoluene (TNT) using IMS and mass spectrometry (MS). It has been demonstrated that TNT ion formation in a gas medium is a complicated process and includes both an electron emission from the pSi surface with subsequent ion-molecular reactions in a gas phase and a proton transfer between pSi surface and TNT molecule.