Fast Proton Conduction in Denatured Bovine Serum Albumin-Coated Nafion Membranes

摘要

Bovine serum albumin (BSA) is a globular soluble protein, which has been extensively used in biochemical engineering. BSA materials possess abundant hydrophilic charged amino acids, H-bonded networks, and various secondary structures, which has great potential in facilitating proton transfer. Herein, BSA N117 (BSA Nafion 117) membranes are conveniently and eco-friendly prepared by utilizing the adsorption and denaturation of BSA on the Nafion 117 surface. The morphology and secondary structures of the BSA layer are studied with field-emission scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy. BSA N117 membranes show highly increased proton conductivity under various conditions, which could be attributed to the improved wettability, water uptake, and the denaturation of BSA. The in-plane proton conductivity of BSA N117-5 reaches 0.3 and 0.06 S cm(-1) under 80 degrees C-95% RH and 100 degrees C-40% RH, respectively. The denaturation of BSA leads to the unfolding of alpha-helix structures and the formation of beta-sheet structures. beta-Sheet structures are more beneficial to proton conduction since beta-sheet structures have stronger interactions with water molecules and protons could transport more directly in the parallel H-bonded network. Moreover, the denatured BSA modification layer could effectively help BSA-N117 membranes to possess higher selectivity and overcome the "trade-off" effect between proton conductivity and methanol resistance. The methanol permeability of BSA-N117 membranes is 1 order of magnitude lower than that of Nafion 117.