High Performance CuO Nanorectangles-Based Room Temperature Flexible NH₃Sensor

Abstract

Abstract-Here, we report the fabrication of a flexible room temperature ammonia gas sensor using surfactant-free hydrothermally synthesized copper oxide (CuO) nanorectangles. The structural analysis revealed that the CuO nanorectangles possessed monoclinic structure with an average length and breadth of 950 nm and 450 nm respectively. The specific surface area of CuO nanorectangles was determined to be 29 m 2 /g. The sensor was fabricated on a flexible polyethylene terephthalate substrate by screen printing technique. The room temperature ammonia sensing measurement exhibited significant response down to 5 ppm of ammonia with a quick response time of 90 s and recovered to baseline within 120 s. Maximum response of 0.99 was recorded for 100 ppm of ammonia. The rate constants for adsorption and desorption were estimated for 6.5 to 100 ppm of ammonia from the exponential conductance changes during response and recovery process. The sensor showed appreciable stability and reproducibility of the sensing performance over a period of 3 months. The fabricated flexible sensor demonstrated its ability to detect a wide range of ammonia concentrations at room temperature irrespective of the mechanical deformations applied. Thus, the fabricated sensor is promising and can be suitably employed for practical applications in environments where efficient gas sensing is vitally important.

Advances in designs and mechanisms of semiconducting metal oxide nanostructures for high-precision gas sensors operated at room temperature

“…Up to now, the major p-type SMONs used in RT gas sensing have been CuO, [223][224][225] S 224,225 and NO 2 , 226 as listed in Table 2. Apart from the sensing mechanism which is based on the reaction of target gases with the oxygen ions on the surface of SMONs, the formation of metal sulfides is another key reason for H 2 S sensing, especially for CuO nanostructures.…”

“…SMONs with a potentially higher carrier mobility and mechanical robustness are good candidates for the realization of stretchable and flexible sensors. 223 The mechanically flexible and wearable RT gas sensors based on SMONs have been an active research area recently as listed in Table 8. Compared with those on the rigid substrates, the wearable devices need substrates which are flexible, light weight, transparent, transportable, with a small volume, and low cost.…”

“…properties, and thermal and chemical stability, many plastic substrates have been used as flexible substrates for the RT gas sensors including polyethylene terephthalate (PET), 223,[402][403][404] polypropylene (PP), 405,406 polyimide (PI), 264,407,408 polyvinyl acetate (PVA) 105 and nylon. 409 For many of these flexible RT gas sensors, a sensitive layer such as ZnO nanorods is often used to deposit onto the device, for example, ZnO nanorods/nylon, 409 Ga-ZnO nanorods/PI, 264 Pd-ZnO nanorods/PI/PET.…”

“…The CuO nanostructures are also suitable for NH 3 sensing at RT. Sakthivel et al223 fabricated a flexible NH 3 sensor on a polyethylene terephthalate substrate using CuO nano-rectangles, which were synthesized using a surfactant-free hydrothermal method. The flexible RT sensor made of the CuO nano-rectangles is effective…”

Gas sensor array assisted with UV illumination for discriminating several analytes at room temperature

“…Metal-oxide gas sensors usually operate at elevated temperatures, which lead to high power consumption and lifetime degradation. Different techniques for solving the problem of high operating temperature have been reported in the previous studies such as doping with noble metals, surface decoration with various catalyst materials, ultraviolet (UV) light stimulation and so on [22][23][24][25]. Among them, UV light stimulation in photocatalytic metal oxides has attracted much interest to activate the chemical reactions at low operating temperatures in related sensors [22,23].…”