Standoff discrimination and trace detection of explosive molecules using femtosecond filament induced breakdown spectroscopy combined with silver nanoparticles

The potential of femtosecond filament induced breakdown spectroscopy technique (fs FIBS) towards the detection of explosive/energetic molecules (EMs) at a standoff (ST) distance of ∼6.5 m is demonstrated. A set of six energetic nitroimidazoles were investigated and discriminated with the fs FIBS technique in tandem with principal component analysis (PCA). The fs ST-FIBS spectra of these EMs were dominated with CN emissions with weak C2 emission and devoid of other atomic peaks (H, N, and O). In addition, an enhancement in LIBS/ST FIBS signal of EMs is achieved in the presence of Ag nanoparticles (NPs) using the nanoparticle enhanced LIBS (NELIBS) technique. Furthermore, the potential of fs filaments for detecting explosive traces is also demonstrated by detecting the residue of an explosive molecule CL-20 on a brass target using the fs NEFIBS technique.