Gas sensors based on pearl-necklace-shaped In2O3 nanotubes with highly enhanced formaldehyde-sensing performance

Abstract

With the increasing demand for high-performance sensors, gas-sensing materials are recognized as one of the core components of gas sensors. Therefore, the development of gas-sensing materials with excellent gas-sensing properties is of great significance. To meet this requirement, we aim to synthesize high-performance 1D gas-sensing materials with new morphologies. In this work, pearl-necklace-shaped In2O3 nanotubes (PINTs) were successfully synthesized by a single-nozzle electrostatic spinning method followed by calcination. The nanostructure and formaldehyde gas-sensing properties of PINTs were compared with those of In2O3 nanotubes (INTs) and In2O3 nanofibres (INFs), and the morphologies and phases of PINTs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). The SEM images clearly show that PINTs have a unique tubular structure that looks like a string of pearls. The formaldehyde gas-sensing characteristics of the sensors based on INFs, INTs and PINTs were investigated. All gas sensitivity measurements were performed at an optimum operating temperature of 220 °C. The results revealed that the sensors based on PINTs showed the greatest response to formaldehyde gas (38.3/100 ppm) compared with the sensors based on INTs (18.5/100 ppm) and INFs (9.0/100 ppm). Sensors with PINTs were found to have shorter response and recovery times (6 s and 16 s) than those of INTs (8 s and 22 s) and INFs (8 s and 27 s). The enhanced gas-sensing properties may be attributed to the novel nanostructure of PINTs. Furthermore, the sensors based on PINTs have good linearity, stability, repeatability and selectivity. These properties make PINTs ideal gas-sensing materials for use in sensors for formaldehyde detection.