Trace detection of explosives has been an ongoing challenge for decades and has become one of several critical problems in defense science; public safety; and global counter-terrorism. As a result, there is a growing interest in employing a wide variety of approaches to detect trace explosive residues. Spectroscopy-based techniques play an irreplaceable role for the detection of energetic substances due to the advantages of rapid, automatic, and non-contact. The present work provides a comprehensive review of the advances made over the past few years in the fields of the applications of terahertz (THz) spectroscopy; laser-induced breakdown spectroscopy (LIBS), Raman spectroscopy; and ion mobility spectrometry (IMS) for trace explosives detection. Furthermore, the advantages and limitations of various spectroscopy-based detection techniques are summarized. Finally, the future development for the detection of explosives is discussed.

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High−energy density supercapacitors have attracted extensive attention due to their electrode structure design. A synergistic effect related to core–shell structure can improve the energy storage capacity and power density of electrode materials. The Ni−foam (NF) substrate coupled with polypyrrole (PPy) conductive coating can serve as an internal/external bicontinuous conductive network. In this work, the distinctive PPy@FeNi2S4@NF and PPy@NiCo2S4@NF materials were prepared by a simple two−step hydrothermal synthesis with a subsequent in situ polymerization method. PPy@FeNi2S4@NF and PPy@NiCo2S4@NF could deliver ultrahigh specific capacitances of 3870.3 and 5771.4 F·g−1 at 1 A·g−1 and marvelous cycling capability performances of 81.39% and 93.02% after 5000 cycles. The asymmetric supercapacitors composed of the prepared materials provided a high−energy density of over 47.2 Wh·kg−1 at 699.9 W·kg−1 power density and 67.11 Wh·kg−1 at 800 W·kg−1 power density. Therefore, the self−assembled core–shell structure can effectively improve the electrochemical performance and will have an effective service in advanced energy−storage devices.

There are dependences of reactivity of nano reactivity multilayer films on scale, and the chemical pre-reactions at interface of reactivity multilayer films (RFMs) are avoided. The reactivity of Al/Ni, Al/Ti nano RFMs were analyzed by XRD and DSC. Analyzed results shown that the released heat of nRFMs depend on thickness of reactant layers, the thinner layer, the less released heat and the released heat is less than its theoretical heat. A pre-reaction region exists possibly at the interface of boundary layers by XRD analysis. A simple equation is derived to calculate the thickness of pre-reaction by the experimental data of RFMs reaction heat. The calculated results shown the thickness of pre-reaction layer depends on increasing of scale progressively.

Detailed knowledge of dissociation behavior and dissociation products is necessary to understand the stability, sensitivity, and the reactive mechanism of explosives under laser initiation. A time-of-flight mass spectrometer was utilized to detect the transient products of 1,1-diamino-2,2-dinitroethylene (FOX-7) produced under 532 nm pulse laser ablation, the possible attribution of intermediate ion fragments were confirmed. The laser fluence threshold for detectable fragments is about 3.6 J/cm2. The peak intensities of main ions (CN, CNO/C2H4N, NO2, C2N2O, HCN, C2NH2, etc.) increase with the increasing of laser fluence, and reach the maximum at 11.5 J/cm2. Moreover, time-depend changes of ion intensity indicate that the type and degree of reactions are different in different periods. According to the molecular structure of FOX-7 and the intermediate ions, the laser-induced dissociation mechanisms were proposed to illustrate the cause of the fragments which might throw some light on the laser initiation of FOX-7.