Swelling behavior of pyrene-labelled polystyrene LB thin film exposed to various volatile organic vapors
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In this work thin films of pyrene-labelled polystyrene (PS) prepared Langmuir-Blodgett (LB) film technique are characterized by UV-visible spectroscopy, Atomic Force Microscopy (AFM) and Surface Plasmon Resonance (SPR). The sensing behaviors of the films were investigated with respect to volatile organic compounds (VOCs) at room temperature. The sensing responses of the films against VOCs (chloroform, benzene, toluene and ethanol) were measured by SPR method. In addition, the effects of film morphology and gas sensing properties were discussed. It was found that the PS films exhibited good response, reversibility, stability and faster response and recovery characteristic to VOCs. The changes in reflectivity implied the swelling behavior of PS thin film during adsorption and can be explained by the capture of organic vapor molecules. Fick's law for early-time diffusion was adopted to quantify real time SPR data for the swelling processes. It was observed that diffusion coefficients (D) for swelling obeyed the t(1/2) law and could be correlated with the VOCs used. The response of PS films to the choosed VOCs has been investigated in conditions of physical properties of the solvents, and the films were obtain to be largely sensitive to chloroform vapor compared to other studied vapors.