ZnO/MoS2/rGO Nanocomposite Non-Contact Passive and Chip-Less LC Humidity Sensor

Abstract

In recent years, Radio frequency identification (RFID) technology has been widely used. RFID sensor technology has the advantages of real-time monitoring, accurate data and low cost, and it is applied to mainstream application fields such as asset management, cargo storage, transportation and logistics. A wireless humidity sensor based on zinc oxide (ZnO)/ molybdenum disulfide (MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> )/ reduced graphene oxide (rGO) is proposed. The structure of the sensor was optimized by HFSS software, and the designed humidity sensor was prepared by heat transfer printing technology. The morphology of ZnO/MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /rGO composite was observed by scanning electron microscopy. Nano-rod-like ZnO combined with nano-flower-like MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> structure has a large specific surface area and can better adsorb water molecules. This structure well reflects the excellent conductivity of rGO and the sensitivity of MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> modified ZnO. The humidity sensor has a resonant frequency of about 178.54 MHz at 10 %-95 % relative humidity (RH) and a sensitivity of 4034 Hz/%RH at high humidity (55 %-95 % RH). In the range of 10 % to 95 % RH, the response time and recovery time of the sensor are 7.4 s and 18.3 s, respectively. The experimental results show that the ZnO/MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /rGO composite for humidity sensor is reusable and the sensor is stable in the range of 10%-95% relative humidity. Finally, the sensing mechanism of the sensor under different transmission distances is analyzed. The results show that the sensor is suitable for rapid humidity detection in sealed and open environment.