title: Magnetically aligned iron oxide/gold nanoparticle-decorated carbon nanotube hybrid structure as a humidity sensor.
abstract: Functionalized carbon nanotubes (f-CNTs), particularly CNTs decorated with nanoparticles (NPs), are of great interest because of their synergic effects, such as surface-enhanced Raman scattering, plasmonic resonance energy transfer, magnetoplasmonic, magnetoelectric, and magnetooptical effects. In general, research has focused on a single type of NP, such as a metal or metal oxide, that has been modified on a CNT surface. In this study, however, a new strategy is introduced for the decoration of two different NP types on CNTs. In order to improve the functionality of modified CNTs, we successfully prepared binary NP-decorated CNTs, namely, iron oxide/gold (Au) NP-decorated CNTs (IA-CNTs), which were created through two simple reactions in deionized water, without high temperature, high pressure, or harsh reducing agents. The physicochemical properties of IA-CNTs were characterized by ultraviolet/visible spectroscopy, Fourier transform infrared spectroscopy, a superconducting quantum interference device, scanning electron microscopy, and transmission electron microscopy. In this study, IA-CNTs were utilized to detect humidity. Magnetic IA-CNTs were aligned on interdigitated platinum electrodes under external magnetic fields to create a humidity-sensing channel, and its electrical conductivity was monitored. As the humidity increased, the electrical resistance of the sensor also increased. In comparison with various gases, for example, H2, O2, CO, CO2, SO2, and dry air, the IA-CNT-based humidity sensor exhibited high-selectivity performances. IA-CNTs also responded to heavy water (D2O), and it was established that the humidity detection mechanism had D2O-sensing capabilities. Further, the humidity from human out-breathing was also successfully detected by this system. In conclusion, these unique IA-CNTs exhibited potential application as gas detection materials.
authors.affiliation: †Department of Mechanical and Manufacturing Engineering and ‡Department of Chemistry, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
authors.forename: Jaewook
authors.initials: J
authors.lastname: Lee
authors.affiliation: †Department of Mechanical and Manufacturing Engineering and ‡Department of Chemistry, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
authors.forename: Suresh
authors.initials: S
authors.lastname: Mulmi
authors.affiliation: †Department of Mechanical and Manufacturing Engineering and ‡Department of Chemistry, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
authors.forename: Venkataraman
authors.initials: V
authors.lastname: Thangadurai
authors.affiliation: †Department of Mechanical and Manufacturing Engineering and ‡Department of Chemistry, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
authors.forename: Simon S
authors.initials: SS
authors.lastname: Park
keywords: Au/Fe3O4 nanoparticle-decorated CNTs; aligned magnetoplasmonic CNT; binary nanoparticle-decorated CNTs; humidity detection; magnetic-field alignment; oxidizable iron oxide