An enrichment method to detect low concentration formaldehyde

A semiconductor gas sensor of tin oxide doped with hydroxyl (OH) functionalized multi-wall carbon nanotubes (MWCNTs) was fabricated for detecting indoor formaldehyde concentration. The response of the MWCNTs-doped SnO 2 sensor was much higher than that of an undoped SnO 2 sensor. In order to detect low concentration formaldehyde, a novel enrichment method utilizing active carbon was applied. The response of the sensor was obviously increased by the application of the enrichment method. The lowest concentration of formaldehyde gas detected by a 5 wt% MWCNTs-doped SnO 2 sensor was 0.03 ppm.