No abstract

MXenes, two-dimensional (2D) transition metal carbides and nitrides, have been arousing interest lately in the field of gas sensing thanks to their remarkable features such as graphene-like morphology, metal-comparable conductivity, large surface-to-volume ratio, mechanical flexibility, and great hydrophilic surface functionalities. With tunable etching and synthesis methods, the morphology of the MXenes, the interlayer structures, and functional group ratios on their surfaces were effectively harnessed, enhancing the efficiency of MXene-based gas-sensing devices. MXenes also efficiently form nanohybrids with other nanomaterials, as a practical approach to revamp the sensing performance of the MXene sensors. This Mini-Review summarizes the recent experimental and theoretical reports on the gas-sensing applications of MXenes and their hybrids. It also discusses the challenges and provides probable solutions that can accentuate the future perspective of MXenes in gas sensors.

In the present work, we report highly sensitive and selective nanosensors constructed with metal-decorated graphenelike BC 6 N employing nonequilibrium Green's function (NEGF) formalism combined by density functional theory (DFT) toward multiple inorganic and sulfur-containing gas molecules (NO, NO 2 , NH 3 , CO, CO 2 , H 2 S, and SO 2 ) as disease biomarkers from human breath. Monolayer sheets of pristine BC 6 N and Pd-decorated BC 6 N were evaluated for their gas adsorption properties, electronic property changes, sensitivity, and selectivity toward disease biomarkers. The pristine BC 6 N nanosheets exhibited sharp drops in the bandgap when interacted with gases such as NO 2 while barely affected by other gases. However, the nanosecond recovery time and low adsorption energies limit the gas sensing applications of the pristine BC 6 N sheet. On the other hand, the Pddecorated BC 6 N-based sensor underwent a semiconductor to metal transition upon the adsorption of NO x gas molecules. The conductance change of the sensor's material in terms of I−V characteristics revealed that the Pd-decorated BC 6 N sensor is highly sensitive (98.6−134%) and selective (12.3−74.4 times) toward NO x gas molecules with a recovery time of 270 s under UV radiation at 498 K while weakly interacting with interfering gases in exhaled breath such as CO 2 and H 2 O. The gas adsorption behavior suggests that metal-decorated BC 6 N sensors are excellent candidates for analyzing pulmonary disease and cardiovascular biomarkers, among other ailments of the stomach, kidney, and intestine.

As SARS-CoV-2 is spreading rapidly around the globe, adopting proper actions for confronting and protecting against this virus is an essential and unmet task. Reactive oxygen species (ROS) promoting molecules such as peroxides are detrimental to many viruses, including coronaviruses. In this paper, metal decorated single-wall carbon nanotubes (SWCNTs) were evaluated for hydrogen peroxide (H2O2) adsorption for potential use for designing viral inactivation surfaces. We employed first-principles methods based on the density functional theory (DFT) to investigate the capture of an individual H2O2 molecule on pristine and metal (Pt, Pd, Ni, Cu, Rh, or Ru) decorated SWCNTs. Although the single H2O2 molecule is weakly physisorbed on pristine SWCNT, a significant improvement on its adsorption energy was found by utilizing metal functionalized SWCNT as the adsorbent. It was revealed that Rh-SWCNT and Ru-SWCNT systems demonstrate outstanding performance for H2O2 adsorption. Furthermore, we discovered through calculations that Pt- and Cu-decorated SWNCT-H2O2 systems show high potential for filters for virus removal and inactivation with a very long shelf-life (2.2 × 1012 and 1.9 × 108 years, respectively). The strong adsorption of metal decorated SWCNTs and the long shelf-life of these nanomaterials suggest they are exceptional candidates for designing personal protection equipment against viruses.

Inspired by prior advancements and the growing utilization of two-dimensional (2D) based gas sensors, this work presents the potential of black phosphorene for sensing volatile organic compounds (VOCs) gas molecules....