Electric-Field-Induced Solid-Gas Interfacial Chemical Reaction in Carbon Nanotube Ensembles: Route toward Ultra-sensitive Gas Detectors.

The electric field at the sharp pointed tips of single wall carbon nanotube ensembles has been utilized to kinetically accelerate hitherto unobserved chemical reactions at the heterogeneous solid-gas interfaces. The principle of ″action-of-points″ drives specific chemical reactions between the defect sites of single wall carbon nanotubes (CNTs) and ppb levels of gaseous hydrogen sulfide. This is manifested as changes in the electrical conductivity of the conductive CNT-ensemble (cCNT) and visually tracked as enthalpic modulations at the site of the reaction through infrared thermometry. Importantly, the principle has been observed for a variety of analytes such as NH3, H2O, and H2S, leading to distinctly correlatable changes in reactivity and conductivity changes. Theoretical calculations based on the density functional theory in the presence and absence of applied electric field reveal that the applied electric field activates the H2S gas molecules by charge polarization, yielding favorable energetics. These results imply the possibility of carrying out site-specific chemical modifications for nanomaterials and also provide transformative opportunities for the development of miniaturized e-nose-based gas analyzers.