Characteristics of highly sensitive and selective nitric oxide gas sensors using defect-functionalized single-walled carbon nanotubes at room temperature

Abstract

One of the most important trends in modern medicine is the development of non-invasive methods that diagnose diseases by analyzing specific gases from human exhalation. Examination of such gases helps monitor various diseases. The ability of nanosensors to potentially detect conditions such as Rhinitis digestive diseases, liver transplant rejection, inflammation in the stomach, cystic fibrosis, encephalopathy, helicobacter pylon digestive cancer, respiratory diseases, and COVID-19, by examining nitric oxide (NO), has been discussed as well as studied increasingly in recent years. In this paper, we have proposed a low-cost detector that can measure NO gas from the exhaled air, which is applied to the ppb level at room temperature. A sensor that detects NO gas with high sensitivity by using single-walled carbon nanotubes (SWNTs) as nanomaterials, has been fabricated. The semiconductor-type gas sensors using SWNTs showed characteristics such as rapid detection, long-term reliability, reproducibility, and miniaturization at room temperature. To improve the selectivity for NO gas, SWNT network channels were formed between the Au electrodes, and SWNTs were functionalized with en-APTAS. A new rinse process was introduced to solve the problem of low sensitivity in SWNT-based NO sensors. With the introduction of the improved rinsing process, the recovery of the fabricated sensor increased from less than 20% to 90.34% when the device was rinsed ten times under optimized conditions. The improved rinsing process effectively straightened the rearrangement of the large amount of amine-functionalized SWNTs attached during the electrostatic self-assembled deposition. In addition, a 28.64% response for a 100 ppb concentration of NO gas was measured at room temperature. We also confirmed that the fabricated sensor does not react with carbon monoxide (CO) and volatile organic compounds (VOCs) gases owing to its high selectivity to NO gas.