Investigation of pristine and B/N/Pt/Au/Pd doped single-walled carbon nanotube as phosgene gas sensor: A first-principles analysis

• A novel nano-sensor based on near valence (B and N) and transition metal (Pt/Au/Pd) doped CNT is investigated for detection of phosgene gas. • The sensing mechanism is guided by the Van der Waals interaction based physisorption phenomenon. • The pristine CNT offers relatively weak physisorption towards phosgene gas, whereas the transition metal doped CNTs offer relatively strong physisorption towards phosgene gas. • The Pd-doped CNT is observed to be a great sensing material for the phosgene gas owing to its relatively higher sensitivity, charge transfer, variation in I-V and less recovery time. The present work investigates a novel CNT based sensor for detection of highly toxic phosgene gas, which is widely used as a chemical agent. The investigation is performed via first-principle means in the vicinity of Density Functional Theory (DFT) and Non-Equilibrium Green’s Function (NEGF) formalisms. Though the pristine CNT is less reactive towards the phosgene gas, the near valence (B and N) and transition metal (Pt/Au/Pd) doped CNTs show very good reactivity, and the sensing mechanism is guided by Van der Waals interaction based physisorption phenomenon. The sensing mechanism is assessed with the help of various properties/parameters which include adsorption energies, electronic nature, density of states, charge transfer, electrical transport (I-V), recovery time and sensitivity. Unlike the pristine CNT, the doped CNTs exhibited significant sensing behaviour towards the phosgene, especially the transition metal dopants as witnessed from the I-V characteristics. Au-doped CNT offers tremendous reduction in the drive current on adsorption of phosgene gas, which can be used as an electronic fingerprint of detection. In particular, the Pd-doped CNT exhibits superior sensing behaviour in comparison to the other considered dopants, owing to its significant variation in the I-V, a Mulliken charge transfer of 0.24e, excellent sensitivity of 134.75 %, and very less recovery time of 8.9 ns. Thus, the transition metals (in particular Pd) doped CNTs could prove useful for the design of CNT based physical sensors to detect phosgene gas in various industries such as defence sector where phosgene is used as a chemical warfare agent, and in chemical sector where it is used as a precursor to synthesize several chemicals.