Fig. 1. The development of optical sensing methods for improvised explosive：From colorimetry，fluorescence to dual mode；From solution，trace residue to single microparticle

Fig. 2. Optical sensing improvised explosives with diverse affinities^{［28，32，33］}

Fig. 3. Schematic illustration of different mechanisms for optical sensing improvised explosives of nitrite and perchlorate^{［32，34］}

Fig. 4. Mechanisms and performances of optical sensing improvised explosives with colorimetric/fluorescent dual mode^{［34，35］}

Fig. 5. Optical sensing improvised explosive solution with paper and hydrogel based sensors^{［30，32］}

Fig. 6. Optical sensing trace residues of improvised explosives^{［30，33］}

Fig. 7. Optical sensing improvised explosive miroparticles^{［28，32，34，40］}