Exploring long-range proton conduction, the conduction mechanism and inner hydration state of protein biopolymers

Abstract

Post formation modification of protein-based materials can attenuate the proton conduction efficiency resulting from change in conduction mechanism, charge carrier mobility, carrier concentrations and inner hydration layer.

Enhanced Proton Conductivity across Protein Biopolymers Mediated by Doped Carbon Nanoparticles

“…[ 36 ] Previously, we have shown how the protonic transport across the BSA mat can be hindered by targeting (i.e., chemically blocking) the protein's functional groups and specifically carboxylates and amines. [ 38 ] The enhanced protonic conductivity across the C‐Dots‐BSA mats can be a result of two different contributions. 1) More C‐Dots within the BSA mat that will increase the concentration of functional groups that are able to donate/accept a proton, meaning an increase in the protonic charge carrier density.…”

“…Interestingly, the KIE observed for the mats containing the C‐Dots is higher compared to the native BSA mat with a KIE value of around 1.7. [ 38 ] The magnitude of the KIE can be attributed to the effective vibrational modes involved in the proton transport and it is known to have a large effect on the chemical nature of the proton donor and acceptor. [ 46 ] Hence, the similar KIE between all different C‐Dot‐BSA mat implies the significant role of the C‐Dots in the proton transport mechanism (further discussion below).…”

“…[25][26][27][28] Recently, a new class of proton conductive polymers has emerged using macromolecular biological building blocks as the starting materials for the formation of a biopolymer, and specifically polysaccharides and proteins. [29][30][31][32][33][34][35][36][37][38] The efficient protonic conduction across such biopolymers is due to the natural occurrence of protonable groups (oxoacids and amines) in their chemical structure as well as their high water content. The use of biological macromolecular is advantageous due to their environmental impact and sustainable nature.…”

“…[41] The protonic conductivity across the BSA mat is due to both the high water content within the mat as well as to functional groups of the protein. [37,38] We have performed both ac-bias impedance measurements and dc-bias current-voltage measurements (Figure 3a and Figure S7, Supporting Information, respectively). The main advantage of impedance measurements is the ability to decouple between bulk resistivity, manifested at high ac frequencies (≥1 kHz), to contact resistance effects, manifested at low frequencies, whereas dc measurements are highly influenced by contact resistance.…”

Protein‐Engineered Functional Materials for Bioelectronics

“…Mondal et al. [ 146 ] studied a BSA‐nanomat as the proton conductor that demonstrated a high proton conductivity of about 10 −4 S cm −1 . Recent years, the studies on all‐solid‐state, protein‐based ion‐conductors for transferring Li + have made breakthrough progress, which paves new avenues for application of proteins in the area of solid‐state alkali‐ion batteries (e.g., Li‐ion batteries).…”