Quartz Crystal Microbalance Detection of Aliphatic Alcohol Vapors via In Situ Polymerized Polypyrrole Film: Experimental Insights and Molecular Dynamics Simulations

The detection of alcohol vapors is important in applications such as breathalyzers and environmental monitoring, yet achieving in situ, sensitive, and selective analysis remains challenging. In this work, a homogeneous in situ‐grown polypyrrole (PPy) thin film is developed directly on the Au‐electrode via the chemical polymerization of pyrrole and evaluated as a sensing layer using the quartz crystal microbalance (QCM) technique for the detection of primary aliphatic alcohol vapors, including methanol, ethanol, 1‐propanol, and 2‐propanol. Structural characterization by scanning electron microscopy, X‐ray diffraction, and Fourier Transform Infrared spectroscopy confirmed the formation of a uniform PPy surface with an amorphous nature. Adsorption of alcohol vapors into the PPy film induced frequency shifts (∆ f ) in the QCM response significantly enhancing sensor sensitivity. The magnitude of ∆ f increased proportionally with alcohol vapor concentration, exhibiting a linear relationship. Diffusion coefficients were determined by examining the diffusion behavior of alcohol vapor in the PPy, and adsorption kinetics were analyzed. Furthermore, molecular dynamics simulations were employed to elucidate the interaction mechanisms between the alcohol and PPy, while enthalpies of mixing were estimated based on the cohesive energy density approach. The PPy‐coated QCM sensor demonstrated excellent reversibility and reproducibility throughout the testing process of volatile alcohols.