Ligand-assisted deposition of ultra-small Au nanodots on Fe2O3/reduced graphene oxide for flexible gas sensors

2D nanomaterials for realization of flexible and wearable gas sensors: A review

Gas sensors are extensively employed for monitoring and detection of hazardous gases and vapors. Many of them are produced on rigid substrates, but flexible and wearable gas sensors are needed for intriguing usage including the internet of things (IoT) and medical devices. The materials with the greatest potential for the fabrication of flexible and wearable gas sensing devices are two-dimensional (2D) semiconducting nanomaterials, which consist of graphene and its substitutes, transition metal dichalcogenides, and MXenes. These types of materials have good mechanical flexibility, high charge carrier mobility, a large area of surface, an abundance of defects and dangling bonds, and, in certain instances adequate transparency and ease of synthesis. In this review, we have addressed the different 2D nonmaterial properties for gas sensing in the context of fabrication of flexible/wearable gas sensors. We have discussed the sensing performance of flexible/wearable gas sensors in various forms such as pristine, composite and noble metal decorated. We believe that content of this review paper is greatly useful for the researchers working in the research area of fabrication of flexible/wearable gas sensors.

The enhanced sensing properties of MOS-based resistive gas sensors by Au functionalization: a review

Gas sensors are essential for detecting toxic gases that can harm social life or industrial production. Traditional metal oxide semiconductor (MOS)-based sensors suffer from shortcomings such as high operating temperature and slow response time, which limits their detection capabilities. Thus, there is a need to improve their performance. One useful technique is noble metal functionalization, which can effectively enhance the response/recovery time, sensitivity and selectivity, sensing response, and optimum operating temperature of MOS gas sensors. Among the noble metals, Au NPs are considered a promising material for forming composite sensing materials to achieve better sensing performance. This paper aims to review and discuss the recent research on Au-decorated MOS-based sensors, including Au/n-type MOS-based sensors, Au/p-type MOS-based sensors, Au/MOS/carbon composite materials, and Au/MOS/perovskite composite materials. The sensing mechanism of Au-functionalized MOS-based materials will also be examined.

Realization of Oriented and Nanoporous Bismuth Chalcogenide Layers via Topochemical Heteroepitaxy for Flexible Gas Sensors

Most van der Waals two-dimensional (2D) materials without surface dangling bonds show limited surface activities except for their edge sites. Ultrathin Bi₂Se₃, a topological insulator that behaves metal-like under ambient conditions, has been overlooked on its surface activities. Herein, through a topochemical conversion process, ultrathin nanoporous Bi₂Se₃ layers were epitaxially deposited on BiOCl nanosheets with strong electronic coupling, leading to hybrid electronic states with further bandgap narrowing. Such oriented nanoporous Bi₂Se₃ layers possessed largely exposed active edge sites, along with improved surface roughness and film forming ability even on inkjet-printed flexible electrodes. Superior room-temperature NO₂ sensing performance was achieved compared to other 2D materials under bent conditions. Our work demonstrates that creating nanoscale features in 2D materials through topochemical heteroepitaxy is promising to achieve both favorable electronic properties and surface activity toward practical applications.