Effect of Thiol on Formaldehyde Sensors Based on CNTs

Effect of thiol to the sensing characteristics of gas sensors based on carbon nanotubes(CNTs) were studied. Sensors were divided into three groups: pure CNTs coated on Au electrode; thiol-CNTs coated on Au electrode; pure CNTs coated on Au electrodes modified with alkanethiol self-assembled monolayers(SAMs). When exposed to formaldehyde of different concentration at room temperature, obvious differences in gas sensing responses were observed in three groups, which may caused by the following mechanisms. The alkyl chain of SAMs were indicated to improve the CNTs´ adhesion to Au electrode surface and build an enhancing electron transfer system; by contrast two ends of thiol-CNTs may strongly attach to the electrode surface forming a bow-type structure, which would decrease reactive functional groups and effective sensing area of the sensor.