Fast sensing ammonia at room temperature with proline ionic liquid incorporated cellulose acetate membranes

Abstract

Gas sensors based on polymeric membrane using cellulose acetate and amino acid ionic liquids (AAIL) were prepared using the phase inversion method. Initially, AAIL was prepared by the neutralisation method of amino acids L-Proline and L-Phenylalanine with the IL EMIM OH (base) to form ProIL and PheIL. The prepared membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, atomic force microscopy. Asymmetric nature and finger-like macrovoids was confirmed using SEM and AFM. The synthesized cellulose acetate membrane incorporated with IL and AAILs was tested for the gas sensing by quantifying the change in resistance, in the absence and presence of the test gas inside a chamber. CA membranes with CA-ProIL displayed the best ammonia sensing with lowest value of 1 ppm detection and response and recovery times of 60 s and 78 s respectively. The results suggest that the CA membranes have great potential for gas sensing application and by incorporating IL, AAILs into the matrix it is further increased by a significant amount. Further, NMR analysis suggests the possible mechanism of adduct formation of ammonia with ProIL. • Amino acid ionic liquids-L-Proline (ProIL), L-Phenylalanine (PheIL) were prepared. • Cellulose acetate (CA) polymer membranes were incorporated with ProIL and PheIL. • CA membranes with AAILs showed good porosity and macrovoid type structure. • CA membranes with ProIL displayed the best ammonia sensing at room temperature. • NMR analysis suggests the possible adduct formation of ammonia with ProIL.