Uncontactless detection of improvised explosives TATP realized by Au NCs tailored PPV flexible photoelectric Schottky sensor

Tunnel junction sensing of TATP explosive at the single-molecule level

Triacetone triperoxide (TATP) is a highly potent homemade explosive commonly used in terrorist attacks. Its detection poses a significant challenge due to its volatility, and the lack of portability of current sensing techniques. To address this issue, we propose a novel approach based on single-molecule TATP detection in the air using a device where tunneling current in N-terminated carbon-nanotubes nanogaps is measured. By employing the density functional theory combined with the non-equilibrium Green's function method, we show that current of tens of nanoamperes passes through TATP trapped in the nanogap, with a discrimination ratio of several orders of magnitude even against prevalent indoor volatile organic compounds (VOCs). This high tunneling current through TATP's highest occupied molecular orbital (HOMO) is facilitated by the strong electric field generated by N-C polar bonds at the electrode ends and by the hybridization between TATP and the electrodes, driven by oxygen atoms within the probed molecule. The application of the same principle is discussed for graphene nanogaps and break-junctions.

Effects of Neutral, Anionic and Cationic Polymer Brushes Grafted from Poly(para-phenylene vinylene) and Poly(para-phenylene ethynylene) on the Polymer’s Photoluminescent Properties

The conformation of a fluorescent polymer, in the solid state or in solution, plays a critical role in the polymer’s fluorescent properties. Thus, grafted side chains on a fluorescent polymer can directly influence its optical properties. In this study, the effect of grafted polymeric side chains on the photoluminescent properties of poly(para-phenylene vinylene) (PPV) and poly(para-phenylene ethynylene) (PPE) were investigated. Low- and high-molecular-weight grafts of neutral poly(n-butyl acrylate), cationic poly(trimethylaminoethyl methacrylate) and anionic poly(sulfopropyl acrylate) were grafted onto PPVs and PPEs, and the effect of the grafting on the graft copolymer’s absorption and emission wavelengths, the fluorescence intensity and the quantum yield were studied. The results indicate that in the case of the ionic grafts, contrary to the expectations, the polymers have a reduced quantum yield. This contrasts with the copolymers with uncharged side chains (PnBA), where a major increase in the quantum yield is seen for the self-quenching conjugated pristine polymers. These results reinforce that the molecular conformation of the polymer in a solid or solution plays a critical role in fluorescent polymers photoluminescent properties.