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Density functional theory (DFT) calculation was used to study the potential applications of pure and metal-doped C 24 N 24 fullerene as highly sensitive and selective gas sensors. It is found that gases commonly existing in the air, including NO 2 , CO, NO, NH 3 , N 2 and CO 2 , are weakly adsorbed on pure C 24 N 24. The adsorption strength is increased when they are adsorbed on the metal-doped (Co-, Cr-, Cu-, K-, Li-, Fe-, Ni-, Pd-, Ti-, Mn-, Na-, Zn-, V-) C 24 N 24. The pure and metal-doped C 24 N 24 have a specific response to certain gas according to adsorption energy, charge transfer, band gap and the density of states analyses. Among various metal-doped C 24 N 24 , the adsorption energies of NO 2 on K- and Na-doped C 24 N 24 are apparently lager than those of other gas molecules, which fall between the suitable range of strong physical adsorption and weak chemical adsorption. Upon NO 2 adsorption, the band gap changes of K- and Na-doped C 24 N 24 which corelate with its conductivity reach −12.75% and −26.67%, respectively. In accordance with the band gap changes, the density of states changes and charge transfer for NO 2 adsorption on K- and Na-doped C 24 N 24 are most obvious. Sensor performance analysis further shows K- and Na-doped C 24 N 24 are highly selective in NO 2 detection. The recycle time of Na–C 24 N 24 under ambient condition is also in the suitable range (1.80 s). This study concludes the potential application of the Na-doped C 24 N 24 as high-performance NO 2 sensor. [ABSTRACT FROM AUTHOR]

In order to take insight into the gas sensing performance of single ultrathin WO 3 nanowire, we performed first principles calculation to investigate the gas adsorption properties and used non-equilibrium Green function (NEGF) to investigate the electron transport properties of WO 3 nanowires with gas adsorption. Our investigation indicated that the WO 3 nanowires with/without oxygen vacancies are both sensitive to H 2 S due to the large adsorption energies and distinct charge transfer. Besides, we found that the WO 3 nanowire with O a type oxygen vacancies is highly selective to SO 2. We supposed that the high chemical activity and the small molecular volume of H 2 S and SO 2 are the main reasons of the selectivity. Finally, the negative differential resistance (NDR) effect of single ultrathin WO 3 nanowire and the gate voltage were proposed to benefit the application of WO 3 nanowires gas sensors. We also supposed two ways to take advantage of the NDR effect of single ultrathin WO 3 nanowire in gas sensing applications. It should be noted that this is the first theoretical investigation of WO 3 nanowires gas sensors considering the electron transport properties. Our work highlighted the possibility to use the single ultrathin WO 3 nanowire as superior gas sensors for SO 2 and H 2 S. Image 1 • The single ultrathin WO 3 nanowire without oxygen vacancies was sensitive to H 2 S. • The single ultrathin WO 3 nanowire with oxygen vacancies was sensitive to SO 2. • High chemical activity and small molecular volume are main reasons of selectivity. • Negative differential resistance effect will benefit gas sensing application. [ABSTRACT FROM AUTHOR]