Patil Sanjeev, Arumugam Sudha, Swaminathan Parasuraman
Electronic Materials and Thin Films Lab, Department of Metallurgical and Materials Engineering, IIT Madras, Chennai 600036, India.
Centre of Excellence in Ceramics Technologies for Futuristic Mobility, IIT Madras, Chennai 600036, India.
ACS Omega. 2024 Jun 22;9(26):28978-28988. doi: 10.1021/acsomega.4c04076. eCollection 2024 Jul 2.
Nitrogen dioxide (NO) is a major pollutant, causing acid rain, photochemical smog, and respiratory damage. The annual safe limit is 50 parts per billion (ppb), while concentrations exceeding 1 part per million (ppm) can result in respiratory ailments. Conventionally, n-type metal oxide semiconductors operating at elevated temperatures have been utilized for NO detection. Recently, p-type semiconductors with their hole accumulation layer, rapid recovery post-gas exposure, and good humidity tolerance are being investigated as potential NO sensors, once again working at elevated temperatures. In this work, a room-temperature (27 ± 2 °C) NO sensor is demonstrated by using a nanocomposite based on p-type bismuth ferrite (BFO) nanoparticles and silver nanowires (Ag NWs). This nanocomposite is capable of sensing a NO gas concentration of up to 0.2 ppm. The BFO nanoparticles are synthesized via a sol-gel route followed by sintering at 500 °C to form the crystalline phase. Nanocomposites are obtained by formulating a dispersion of the BFO nanoparticles and Ag NWs, followed by direct writing on both flexible and rigid substrates. The Ag NWs act as the conducting pathway, reducing the overall electrical resistance and thus enabling room-temperature operation. X-ray diffraction, scanning electron microscopy, and surface area studies provide phase information and surface morphology, and the porous nature of the film helps in room-temperature gas adsorption. The current-voltage and gas-sensing behavior are studied to obtain the optimized molar ratio (4:1 BFO/Ag NWs) for the sensor. The sensor deposited on poly(ethylene terephthalate) (PET) also works under a bent condition, indicating good flexibility. Rapid NO sensing was achieved in a BFO-Ag/PET device with response/recovery times of 7/8.5 s and 12/15 s in straight and bent geometries, respectively. Additionally, a good sensitivity of 30 to 60% was achieved for the BFO-Ag/PET device across 100 to 1000 ppb of NO. The development of a nanocomposite combining an active sensing element (BFO) and a charge-transport element (Ag NWs) opens up a multitude of other application areas.
二氧化氮（NO）是一种主要污染物，会导致酸雨、光化学烟雾和呼吸道损伤。其年度安全限值为十亿分之五十（ppb），而浓度超过百万分之一（ppm）会导致呼吸道疾病。传统上，在高温下工作的n型金属氧化物半导体已被用于NO检测。最近，具有空穴积累层、气体暴露后快速恢复以及良好耐湿性的p型半导体作为潜在的NO传感器正在被研究，同样是在高温下工作。在这项工作中，通过使用基于p型铁酸铋（BFO）纳米颗粒和银纳米线（Ag NWs）的纳米复合材料展示了一种室温（27±2°C）NO传感器。这种纳米复合材料能够检测高达0.2 ppm的NO气体浓度。BFO纳米颗粒通过溶胶 - 凝胶法合成，随后在500°C烧结以形成晶相。通过配制BFO纳米颗粒和Ag NWs的分散体，然后直接书写在柔性和刚性基板上获得纳米复合材料。Ag NWs充当导电通路，降低了整体电阻，从而实现室温操作。X射线衍射、扫描电子显微镜和表面积研究提供了相信息和表面形态，并且薄膜的多孔性质有助于室温气体吸附。研究电流 - 电压和气体传感行为以获得传感器的优化摩尔比（4:1 BFO/Ag NWs）。沉积在聚对苯二甲酸乙二酯（PET）上的传感器在弯曲条件下也能工作，表明具有良好的柔韧性。在BFO - Ag/PET器件中实现了快速NO传感，在直线和弯曲几何形状下的响应/恢复时间分别为7/8.5秒和12/15秒。此外，BFO - Ag/PET器件在100至1000 ppb的NO范围内实现了30%至60%的良好灵敏度。结合活性传感元件（BFO）和电荷传输元件（Ag NWs）的纳米复合材料的开发开辟了许多其他应用领域。
