Hierarchical Assembly of α-FeO Nanorods on Multiwall Carbon Nanotubes as a High-Performance Sensing Material for Gas Sensors.

This paper presents a facile hydrolysis reaction and annealing for preparing a novel hierarchical nanoheterostructure via assembly of α-FeO nanorods onto multiwall carbon nanotubes (MWCNTs) backbones. The as-synthesized nanocomposites were characterized using XRD (X-ray diffraction), FESEM (Field emission scanning electron microscopy), TEM (Transmission electron microscopy), XPS (X-ray photoelectron spectroscopy) and BET (Surface Area and Porosity System). The observations showed uniform α-FeO nanorods approximately 100-200 nm in length and 50-100 nm in diameter that were hierarchically assembled onto the surface of the MWCNTs. The formation of the heterostructure was investigated by observing the evolution of the microstructure of the products at different reaction times. The X-ray photoelectron spectra (XPS) showed that the ability of the absorbing oxygen was enhanced by the formation of the heterostructure composites. Moreover, as a proof-of-concept presentation, the novel CNTs@α-FeO hierarchical heterostructure acted as a gas sensitive material. Significantly, the composites exhibited excellent sensing properties for acetone with high sensitivity, exceptional selectivity and good reproducibility. The response of the CNTs@α-FeO sensor to 100 ppm acetones at 225 °C was nearly 35, which was superior to the single α-FeO nanorods with a response of 16, and the detection limit of the sensor was 500 ppb. The enhanced properties were mainly attributed to the unique structure and p-n heterojunction between the CNTs and the α-FeO nanorods.