Research on Moisture-Responsive Color-Changing Sensor Based on NiI2 and Paper

Humidity detection plays a crucial role in fields of agriculture, industrial production and daily life. However, current humidity sensors suffer from issues like complex detection methods and limited response modes. To address these problems, this work proposed a paper-based humidity sensor with photo reactive characteristics by spraying $\mathbf{NiI}_{\mathbf{2}}$ solvent onto a paper substrate. The color-changing principle of the sensor is based on the material transformation of $\mathbf{NiI}_{\mathbf{2}}$ under high humidity conditions, which enables color-change and photo reactivity capacity of the sensor. The experimental results show that the sensor exhibits optimal color-changing effects when the $\mathbf{NiI}_{\mathbf{2}}$ content is 0.02 $\mathbf{mmol}/\mathbf{cm}^{\mathbf{2}}$. Furthermore, the use of dimethylacetamide as a solvent improves the color-changing performance effectively. This research demonstrates the broad application prospects of $\mathbf{NiI}_{\mathbf{2}}$ -based moisture-responsive color-changing sensors in the field of humidity detection.