Design of humidity sensor based on poly(sodium 4-styrenesulfonate) modified SnO2 for visual monitoring of plant growth environments

Abstract

Organic-inorganic hybrid materials hold great application prospects in electronic devices such as humidity sensors due to their unique interfacial effects and synergistic interactions. However, relatively few studies have been conducted on the sensitization mechanism of organic–inorganic hybrid materials. Herein, we report a high performance humidity sensor based on an organic-inorganic hybrid material of poly(sodium 4-styrenesulfonate)-modified amino-functionalized SnO₂ (PSS-SnO₂). By employing the PSS surface modification strategy, the content of sulfonic groups (-SO₃H) and oxygen vacancies on the surface of SnO₂ was significantly increased, which effectively enhanced its humidity sensing performance. The results reveal that the PSS-SnO₂ sensor has a higher response (18421.6), lower humidity hysteresis (1.8% RH) and faster response/recovery (2.8/5.7 s) compared to the SnO₂ sensor. Experimental analysis and density functional theory (DFT) results show that the presence of oxygen vacancies and -SO₃H effectively promotes the dissociation of water molecules, resulting in more H⁺ conduction on the surface of SnO₂, which improves the sensitivity and response time of the sensor. Furthermore, the PSS-SnO₂ humidity sensor realizes visual monitoring of plant growth environments, which shows the potential in the field of smart agriculture.