This work reports the enhancement in sensitivity of a simple and low-cost capacitive moisture sensor using a thin film of zinc oxide (ZnO) nanoparticles on electrodes. The ZnO nanoparticles are systematically characterized using X-ray diffraction, atomic force microscopy, transmission electron microscopy, BET surface area analysis, Fourier transform infrared spectroscopy, and UV-visible and photoluminescence (PL) spectroscopy. The average crystallite size of the ZnO nanoparticles is ∼16 nm with a surface roughness of ∼3 nm. Blue emission in the PL spectrum confirms the presence of oxygen vacancy dipoles, which are responsible for enhancing the dielectric properties of the ZnO nanoparticles. The effect of the ZnO nanoparticles on the sensitivity of a moisture sensor cell has been studied using wheat grains with a moisture content from 7% to 25%. An enhancement in sensitivity of 36.4% at 1 MHz and 97.4% at 500 Hz has been observed. A detailed sensing mechanism is proposed and the enhancement in sensing has been explained based on the interaction of ZnO with water vapor and the dielectric behavior of the nanostructured ZnO. The present results establish ZnO as a sensing material for improving the utility of moisture sensors.

中文翻译：

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增强纳米结构 ZnO 涂层电容传感器的湿度传感特性

这项工作报告了在电极上使用氧化锌 (ZnO) 纳米粒子薄膜的简单且低成本的电容式湿度传感器的灵敏度增强。使用 X 射线衍射、原子力显微镜、透射电子显微镜、BET 表面积分析、傅里叶变换红外光谱以及紫外-可见光和光致发光 (PL) 光谱系统地表征了 ZnO 纳米颗粒。ZnO 纳米颗粒的平均微晶尺寸约为 16 nm，表面粗糙度约为 3 nm。PL 光谱中的蓝色发射证实了氧空位偶极子的存在，它们负责增强 ZnO 纳米粒子的介电性能。已经使用水分含量为 7% 至 25% 的小麦籽粒研究了 ZnO 纳米颗粒对水分传感器单元灵敏度的影响。已观察到灵敏度在 1 MHz 时提高了 36.4%，在 500 Hz 时提高了 97.4%。提出了详细的传感机制，并基于 ZnO 与水蒸气的相互作用和纳米结构 ZnO 的介电行为解释了传感的增强。目前的结果确立了 ZnO 作为提高湿度传感器效用的传感材料。