p–p Heterojunction of Nickel Oxide-Decorated Cobalt Oxide Nanorods for Enhanced Sensitivity and Selectivity toward Volatile Organic Compounds

Abstract

The utilization of p-p isotype heterojunctions is an effective strategy to enhance the gas sensing properties of metal-oxide semiconductors, but most previous studies focused on p-n heterojunctions owing to their simple mechanism of formation of depletion layers. However, a proper choice of isotype semiconductors with appropriate energy bands can also contribute to the enhancement of the gas sensing performance. Herein, we report nickel oxide (NiO)-decorated cobalt oxide (CoO) nanorods (NRs) fabricated using the multiple-step glancing angle deposition method. The effective decoration of NiO on the entire surface of CoO NRs enabled the formation of numerous p-p heterojunctions, and they exhibited a 16.78 times higher gas response to 50 ppm of CH at 350 °C compared to that of bare CoO NRs with the calculated detection limit of approximately 13.91 ppb. Apart from the p-p heterojunctions, increased active sites owing to the changes in the orientation of the exposed lattice surface and the catalytic effects of NiO also contributed to the enhanced gas sensing properties. The advantages of p-p heterojunctions for gas sensing applications demonstrated in this work will provide a new perspective of heterostructured metal-oxide nanostructures for sensitive and selective gas sensing.

Nanoscale heterojunctions of rGO-MoS2 composites for nitrogen dioxide sensing at room temperature

“…Such modulation of accumulation region on NO 2 exposure leads to greater change in resistance thus contributing to enhanced sensitivity. Similar homojunction between two types of materials leading to enhanced resistance change has been reported previously [54]. The p-type nature of the MoS 2 is further confirmed from the gas sensing behaviour of MoS 2 synthesized hydrothermally and work function and valence band maxima (VBM) position evaluation by UPS technique.…”

Chemoresistive materials for electronic nose: Progress, perspectives, and challenges

“…It is highly desirable that the electronic sensor system monitors the chemical composition of the gases emitted from a combustion facility in real time to minimize air contamination and maintain the concentration of dangerous gas species within the limits specified by regulations. MOS gas sensors are considered to be one of the most common materials for determining and measuring the concentration of gases in a combustion atmosphere . These MOS gas sensor devices offer an extensive variety of advantages over conventional analytical devices, such as low cost, short response time, easy fabrication process, and compact size .…”

“…MOS gas sensors are considered to be one of the most common materials for determining and measuring the concentration of gases in a combustion atmosphere. 51,[60][61][62] These MOS gas sensor devices offer an extensive variety of advantages over conventional analytical devices, such as low cost, short response time, easy fabrication process, and compact size. [63][64][65] Despite these qualities, sufficient selectivity in MOS gas sensors has not been demonstrated.…”

Enhanced Photocatalytic Degradation of 2-Butanone Using Hybrid Nanostructures of Gallium Oxide and Reduced Graphene Oxide Under Ultraviolet-C Irradiation

“…Volatile organic compounds (VOCs) with high vapor pressures at room temperature are everywhere because they are emitted from a wide range of consumer products, building materials and adhesives. Many VOCs are toxic and adversely affect the human body in both indoor and outdoor environments [1][2][3]. As human beings spend more time at home and in the work place, the control of VOCs in indoor environments is a critical concern [4].…”