Sensitive and renewable quartz crystal microbalance humidity sensor based on nitrocellulose nanocrystals

Abstract

High-sensitivity and inexpensive humidity sensors with rapid response are crucial for humidity detection. In this study, a quartz crystal microbalance (QCM) sensor based on nitro-modified cellulose nanocrystals (NCNCs) films were developed for rapid and sensitive detection of humidity. The NCNCs films with good hydrophilicity along with fast water adsorption and dehydration were used as the humidity sensitive material. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction were used to examine the chemical and crystalline properties of NCNCs. The morphology, roughness, and thickness of NCNCs deposited on the QCM silver electrode were characterized by atomic force microscopy and field emission scanning electron microscopy. The results confirmed that the humidity sensor with NCNCs loading of 2.67 μg (QCM-4) exhibited high sensitivity (25.6 Hz/% RH) and extremely small response/recovery times (18 s / 10 s). In addition, the sensor showed excellent reliability and logarithmic linearity in 11−84 % relative humidity (RH). The adsorption of water on the surfaces of NCNCs and the sensing mechanism was examined by density functional theory (DFT) simulation. From the perspective of a sustainable and renewable material, low-cost NCNCs with high humidity sensitivity seem to be the ideal material for developing high-performance sensors with multiple potential applications.