Exploration of the toxic target gas molecules for layered and tubular g-C3N4: Density functional theory

• The optical property are altered by new chemical bonds between toxic molecules and substrates. • The L-g-C 3 N 4 (T-g-C 3 N 4 ) could respond to the extra red (green) light. • The L-g-C 3 N 4 (T-g-C 3 N 4 ) will be utilized as an opto-sensing material to identify the CO (NO 2 ). Graphitic carbon nitride (g-C 3 N 4 ) is regarded as a favorable candidate of gas opto-sensing materials due to its active nitrogen atoms and unique photoelectric performances. To investigate the gas opto-sensing performances of layered g-C 3 N 4 (L-g-C 3 N 4 ) and armchair tubular g-C 3 N 4 (T-g-C 3 N 4 ), the toxic target gas molecules of CO and NO 2 are confirmed from some common toxic gas molecules on account of the calculated adsorption behaviors, electronic and optical performances with the aid of density functional theory. Results indicate that the CO (or NO 2 ) molecule has evident effects on the electronic and optical performances of L-g-C 3 N 4 (or T-g-C 3 N 4 ) substrate due to the new C-N (or O-N) chemical bonding between CO (or NO 2 ) gas molecule and L-g-C 3 N 4 (or T-g-C 3 N 4 ). On account of the characteristic photo-response, the L-g-C 3 N 4 (or T-g-C 3 N 4 ) will respond to the extra red (or green) light when the air included the CO (or NO 2 ) gas and be utilized as a as opto-sensing material to identify the CO (or NO 2 ) gas. The strategy will be applied to devise more gas opto-sensing materials for specific gas molecules.