ZnO@SiO2/rGO core/shell nanocomposite: A superior sensitive, selective and reproducible performance for 1-propanol gas sensor at room temperature

In this research, the Staudenmaier method adopted to synthesize the reduced graphene oxide to be used in the ZnO@SiO2/rGO nanocomposite preparation by sol-gel assisted hydrothermal method. SEM images showed the formation of graphene oxide layers with a thickness of about 41 +/- 1 nm as well as the formation of spherical ZnO@SiO2 nanoparticles with an average diameter of 32 +/- 1 nm on graphene plates. The formation of expected elements in the fabricated nanocomposite, confirmed by the EDS analysis. XRD patterns showed that rGO and ZnO were crystalline and SiO2 was non-crystalline. The FT-IR spectrum of the desired microstructure and the TEM image confirmed the core/shell structure. The application of this nanocomposite as a gas sensor was evaluated. According to the measurements done at the ambient conditions (RH 45%, 29 degrees C), the sensor sensitivity to 300 ppm of the ethanol, methanol and 1-propanol, were 131.7, 21.8 and 156.8 units, respectively. Although the logarithm of the sensitivity linearly depends on the concentration of the samples in the range of 150-450 ppm, but the maximum R2 of 0.9478 indicates the ability of this sensor to quantitatively measure 1propanol. The RSD percentage less than five for all samples indicates good reproducibility of the sensor response. Ten months investigation revealed that the appropriate time for repetitive responses of synthesized sensor is about 8 months. The response and recovery times were measured as improved sensor properties. The results showed that the synthesized sensor can be used as a quantitative and qualitative measurement of 1-propanol. Finally the sensing mechanism was discussed based on electronic transmissions.