The present invention provides a fiber optic probe sensor comprising noble metal nanostructures functionalized with nitro specific receptors for detection of nitro containing compounds and a method for its manufacture. In particular, the present invention relates to a method for vapor phase detection of nitro(-NO2) containingcompounds by said probe comprising noble metal nanostructures functionalized with nitro specific receptors, wherein the noble metal nanostructures exhibits Localized Surface Plasmon Resonance (LSPR).