MXenes provide exceptional signal-to-noise ratios in gas sensing

Gas sensors have long served critical roles in industrial applications, including monitoring air quality and engine emissions. Analyzing volatile organic compounds in breath to screen for disease markers is a developing application that is being advanced by highly sensitive “homemade” gas sensors, often based on semiconducting oxides, nanomaterials, and two-dimensional materials. That field may advance even more quickly now thanks to a study showing that a titanium carbide MXene compound can be fashioned into a gas sensor that provides part-per-billion-level sensitivity and record-setting signal-to-noise ratios (ACS Nano 2018, DOI: 10.1021/acsnano.7b07460). Various 2-D materials, including black phosphorus and molybdenum disulfide, rank among the top-performing gas-sensing media. That motivated a team led by Hee-Tae Jung of Korea Advanced Institute of Science & Technology and Yury Gogotsi of Drexel University to see how MXenes, a family of 2-D metal carbides and nitrides, stack up in that application. Head-to-head comparisons in tests with acetone, ethanol, ammonia, propanal, and other gases relevant to breath analysis show that the MXene compound evaluated, Ti₃C₂, provides signal-to-noise ratios roughly 100 times as high as those of the other 2-D materials. The team attributes the excellent performance to the MXene’s porosity, metal-like conductivity, and abundant surface groups that adsorb analytes.