Surface charge manipulation for improved humidity sensing of TEMPO-oxidized cellulose nanofibrils

作者：Jiaying Zhu, Penghui Zhu, Yeling Zhu, Yuhang Ye, Xia Sun, Yifan Zhang, Orlando J. Rojas, Peyman Servati, Feng Jiang · 发表于：Carbohydrate Polymers · 年份：2024 · DOI：10.1016/j.carbpol.2024.122059 · 被引用次数：37 · 研究领域：Advanced Sensor and Energy Harvesting Materials、Gas Sensing Nanomaterials and Sensors、ZnO doping and properties

Cellulose-based humidity sensors have attracted great research interest due to their hydrophilicity, biodegradability, and low-cost. However, they still suffer from relatively low humidity sensitivity. Due to the presence of negatively charged carboxylate groups, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (CNF) exhibits enhanced hydrophilicity and ion conductivity, which is considered a promising candidate for humidity sensing. In this work, we developed a facile strategy to improve the humidity sensitivity of CNF films by regulating their surface charge. With the increase in surface charge density, both water uptake and charge carrier densities of the CNF films can be improved, enabling a humidity sensitivity of up to 44.5 % (%RH)−1, higher than that of most polymer-based humidity sensors reported in the literature. Meanwhile, the sensor also showed good linearity (R2 = 0.998) over the 15–75 % RH at 1 kHz. With these features, the CNF film was further demonstrated for applications in noncontact sensing, such as human respiration, moisture on fingertips, and water leakage, indicating the great potential of CNF film in humidity monitoring.