We report for the first-time the development of capacitive type humidity sensors employing naphthalene diimide derivatives (NDI) as sensing layer. Three different naphthalene diimide derivatives bearing imide side chains of different hydrophilicity were designed, synthesised and characterised. X-ray diffraction and thermogravimetric analyses gave useful information about structural and thermal behaviour of the newly developed materials, indicating their crystallinity and stability. Atomic force microscopy analysis revealed a variety of morphologies in thin films as a result of the structural properties of the NDIs. Devices bearing NDI layers were fabricated on ceramic substrates with gold interdigitated electrodes spaced 200 µm apart. Humidity sensing performance, as a change in capacitance, was studied upon exposure to a wide range of relative humidity levels (0–95%) at ambient temperature. Importantly, an increase in the capacitance of the sensors was recorded with an increase in relative humidity. The developed sensors exhibited high sensitivity, good long-term stability, excellent reproducibility, and low hysteresis. The sensor performance was also tested against different operating frequencies (250 Hz–2 kHz) to improve linearity, illustrating directions for optimised performance. These results confirm that sensors based on NDIs possess better sensing performance to other types of reported capacitive humidity sensors.

我们首次报告了使用萘二酰亚胺衍生物（NDI）作为传感层的电容式湿度传感器的开发。设计，合成和表征了三种带有不同亲水性酰亚胺侧链的萘二酰亚胺衍生物。X射线衍射和热重分析提供了有关新开发材料的结构和热行为的有用信息，表明了它们的结晶度和稳定性。原子力显微镜分析显示，由于NDI的结构特性，薄膜中的形貌多种多样。带有NDI层的设备是在陶瓷基板上制造的，其中的金指状电极间隔200μm。湿度感测性能，随着电容的变化，在环境温度下暴露于各种相对湿度水平（0–95％）时进行了研究。重要的是，随着相对湿度的增加，记录了传感器电容的增加。开发的传感器具有高灵敏度，良好的长期稳定性，出色的重现性和低滞后性。还针对不同的工作频率（250 Hz–2 kHz）测试了传感器性能，以改善线性度，从而说明了优化性能的方向。这些结果证实，基于NDI的传感器比其他类型的电容式湿度传感器具有更好的感测性能。长期稳定性好，可重复性极佳，滞后性低。还针对不同的工作频率（250 Hz–2 kHz）测试了传感器性能，以改善线性度，从而说明了优化性能的方向。这些结果证实，基于NDI的传感器具有比其他类型的已报告电容式湿度传感器更好的感测性能。良好的长期稳定性，出色的可重复性和低滞后性。还针对不同的工作频率（250 Hz–2 kHz）测试了传感器性能，以改善线性度，从而说明了优化性能的方向。这些结果证实，基于NDI的传感器具有比其他类型的已报告电容式湿度传感器更好的感测性能。