Influence of Layer’s Annealing Temperature on Sensing Properties of Spin-Coated SBS Layer Exposed to Alcohol Vapor

Abstract

QCM-based alcohol vapor sensors have been widely researched, and various materials have been deposited onto the sensor surface to serve as a functional layer. However, non-conductive polymers such as SBS as a functional layer for alcohol sensors are still minimally reported. In this study, the SBS was deposited on 1 side of the QCM using the spin coating technique. After deposition, the layer was annealed for 1 h. The annealing temperatures are 100, 150 and 200 °C. The concentrations of exposed alcohol vapor were 5, 10, 15, 20, 25, 50, 75 and 100 ppm. This study demonstrated that the SBS layer has the potential to be a functional layer of alcohol sensors. SBS 200 °C is an optimum functional layer for alcohol vapor sensors due to its high ∆f and sensitivity. Meanwhile, SBS 100 °C has poor ∆f and sensitivity. This is due to the morphology of 200 °C SBS, which consists of more valleys that perform as interaction sites for SBS and alcohol molecules. However, one of the limitations of SBS as a functional sensor layer for alcohol sensors is its low selectivity, which is a characteristic of rubbery polymers. HIGHLIGHTS The SBS layer annealed at higher temperatures has more valleys than the SBS layer annealed at low temperatures. The valleys in the morphology of the SBS layer act as interaction sites for alcohol molecules, where each site interacts with an alcohol molecule. It is based on the sensor response and proved by fitting the Langmuir model. The SBS layer annealed at 200 ᵒC has a high ∆f, sensitivity, and longer response time. The selectivity of SBS was relatively low, a characteristic of rubbery polymers. The interaction between SBS and methanol is physisorption. GRAPHICAL ABSTRACT