Plexcitonic nose based on an organic semiconductor

Abstract

A highly sensitive and accurate plexcitonic nose based on an organic semiconductor, J-aggregate cyanine dye [5,5′,6,6′-tetrachloro-1,10-diethyl-3, 30-di(4-sulfobutyl) benzimidazolo carbocyanine (TDBC)], is proposed. The signature of the plexciton is evidently studied by implanting a TDBC layer over plasmon active metals. The interaction between the strong dipole moment of the TDBC molecules residing at the metal-TDBC interface and the electric field generated by the plasmons is responsible for the transfer of energy between plasmon and exciton modes. We have demonstrated that the coupling between the plasmon and the Lorentzian oscillator (i.e., exciton-based system) gives rise to two plexciton modes, namely, upper plexciton (UP) and lower plexciton (LP). We have clearly shown the excitation of the UP (LP) for λ < 589 nm (λ > 589 nm). We observed that the UP exhibits strong dispersion, resulting in high sensitivity. Furthermore, depending upon the nature of the analyte, the change to the organic semiconductor like the TDBC film can be reversible or irreversible. Accordingly, the probe can be reused with a polar analyte like ammonia as such gas desorbs from the surface once removed from the environment. We believe that the plexcitonic nose can open a platform for analyzing food freshness by sensing propanol and acetic acid, identifying traces of explosives and nerve gas, and detecting hazardous chemicals in work environments.