Enhancement in the Detection Ability of Metal Oxide Sensors Using Defect‐Rich Polycrystalline Nanofiber Devices

Abstract

Over the past few decades, ambient air pollution (AAP) sources, including exhaust fumes, toxic air, and particulate materials (PMs), have increased due to power generation, vehicle emissions, and the gas industry. This has compromised environmental safety. In 2018, the World Health Organization (WHO) reported the effects of AAP and household air pollution (HAP) on human health. According to these reports, outdoor air pollution has not only gradually changed our living habits, but also increased the probability of death and diseases, including lung cancer, strokes, ischemic heart disease, and acute respiratory infections. Another report from the WHO in 2016 mentioned that AAP and HAP had caused the death of 543 000 children under the age of 5 years. [1,2] These reports indicate a direct link between AAP, HAP, and human health. HAP includes volatile organic compounds, PMs, CO, SO 2 , and NO. Cooking, heating, and burning solid or liquid fuels such as wood, coal, kerosene, and gasoline generate large amounts of pollutants, which strongly impact human health, especially that of young children and people who spend majority of their time indoors. According to the Occupational Safety and Health Administration (OSHA) regulations of the United States Department of Labor, the concentrations of CO and NO gas in a workplace should not exceed 35-50 ppm and 30-45 ppm, respectively. CO and NO, which are colorless, tasteless, and have nonirritant properties, [3-7] are toxic gases. If people are exposed to a CO and NO gas environment for a long time, these gases dissociate into their blood and combine with hemoglobin (Hb) to reduce the oxygen-carrying capacity of the blood. Hence, it is important to prevent or minimize HAP. To reduce AAP and HAP (CO, SO 2 ,and NO x), semiconductor materials (ZnO, TiO 2 , and SnO 2) could be converted into high porosity polycrystalline nanofibers (PNFs), which have many advantages, including a nanointerface between nanograins, [8,9] wide band gap (3.6 eV), and generation-recombination centers, owing to the defects and dangling bonds at the end of nanograin's surface. Recent studies on the development and application of PNFs suggest that they can be used in photonic devices, such as photon sensors [10-13] and solar cells, [14,15] as well as non-photonic devices, such as PM filters, [16,17] toxic gas sensors, [18-34] biological sensors, [35-39] RRAM devices, [40,41] and energy devices. [42-49] The indoor ambient temperature for the majority of households is ≈25-30 °C. According to Yang and co-workers [50] and Moon et al., [29] SnO 2 and TiO 2 The development of SnO 2 and TiO 2 polycrystalline nanofiber devices (PNFDs) has been widely researched as a method of protecting humans from household air pollution. PNFDs have three significant advantages. The nanofibers before the annealing process are polymer-rich materials, which can be used as particulate material (PM) filters. The multiporous nanofibers fabricated by the annealing process have numerous defects that can serve as generation-recombination c...

Defect-Rich SnO2 Nanofiber as an Oxygen-Defect-Driven Photoenergy Shield against UV Light Cell Damage

“…A defect-rich SnO 2 nanofiber device had been successfully manufactured to achieve a low-operating-temperature (50 °C) CO gas sensor and multiple-wavelength light (365−940 nm) sensing property. 23 Defect engineering is another crucial factor in expanding the range of applications for SnO 2 nanofiber material. For example, recent reports have indicated that continued improvements in defect engineering have extended the applicability of SnO 2based nanofiber materials to biosensors, 24 exhaled-breath biosensors, 25 and other biomedical applications.…”

“…However, only SnO 2 nanofibers present the best stability and photoelectric effects than the others. A defect-rich SnO 2 nanofiber device had been successfully manufactured to achieve a low-operating-temperature (50 °C) CO gas sensor and multiple-wavelength light (365–940 nm) sensing property …”