Spectroelectrochemistry of Explosive Aliphatic Nitro Compounds

Abstract

The spectroelectrochemical behavior of non-aromatic explosive compounds, namely two nitramines (RDX and HMX), a nitrate ester (PETN), and a plastic explosive composite (Semtex 1A) in acetonitrile is reported. The electrochemical behavior of these compounds using cyclic voltammetry is performed while monitoring the UV absorbance spectra of transient and product species in situ. In search of a low-cost solution-phase detection technique, we compare the spectroelectrochemistry of these compounds in the absence and presence of naturally dissolved oxygen (~2 mM in AcN), where the superoxide radical is co-electrogenerated during explosive analyte reduction. Free superoxide yields an intense UV signal in this medium (λmax = 250 nm) that the explosives attenuate to varying degrees. We deconvolute UV spectral data through time- and potential-resolved analyses coupled with electrochemical data. It is found that superoxide interacts with the explosives through unique, previously unreported ways, likely due to strongly polarized electrostatic potentials across the poly-nitro aliphatic molecules. Reaction mechanisms will be proposed and the findings expand the understanding of high-explosive solution chemistry and offer a route to novel signal transduction for (electro-)chemical sensors for energetic materials.Figure 1. Spectroelectrochemistry of the control solution, aerated 0.1 M TBAPF6 in acetonitrile. (a) CV (ν = 50 mV s-1) in time and potential domains with the superoxide absorbance at 250 nm plotted for qualitative visualization; (b) time-resolved, full-spectrum UV data recorded during the CV. Figure 1