The Titano-Porphyrin doped pillared graphene as a novel “turn-off” fluorescent sensor for CO gas: Theoretical study

The aim of this study is to investigate and improvement of the CO gas sensing capacity of pure and Titano-Porphyrin doped pillared graphene (Ti-PIPG) using DFT calculations at B3LYP/6-31G (d) level of theory. To this end, a pillared graphene (PG) containing two parallel graphene sheets with four vertical (6,0) single walled carbon nanotubes as holders was selected. First, the effects of stretching and screwing distortions were studied on the stability, band gap and CO sensing capability of undopped PG. The results showed that the normal and distorted forms of PG could only be as a CO storage capacitor. Next, the graphene sheet of pillared graphene structure was doped using Titano-Porphyrin moiety to enhance the CO gas sensing capacity. The geometrical structures, binding energies, electronic and optical properties, ΔN, FOT, DOS, distribution of the HOMO-LUMO, NBO basis analysis and TDDFT absorption spectra were scrutinized to predict the adsorption properties and mechanism of Ti-PIPG-CO system. Based on the calculated EadsBSSE and Eg, it is expected that the Ti-PIPG could be a promising candidate in gas sensor design for detection of CO. In optical point of view, the CO adsorption on Ti-PIPG quenched the fluorescence as due to a PET mechanism. Generally, this sensor is used to sense CO through changes in its both electrical and optical properties. The results showed that, doping could enhance the sensing capacity of pillared graphene in comparison to pure structure. [Display omitted] •Normal, screwed and stretched forms of pure pillared graphene have storage capacity of CO gas.•Doped Pillared graphene significantly enhanced adsorption and sensing of CO gas.•Ti-Porphyrin doped pillared graphene is an electric and “turn-off” fluorescent sensor for CO gas.•DFT and TDDFT studies were applied to analyze the CO gas sensing mechanism.