Reversed Anionic Hofmeister Effect in Metal–Phenolic-Based Film Formation

Abstract

Although metal−phenolic species have emerged as one of the versatile material-independent-coating materials, providing attractive tools for interface engineering, mechanistic understanding of their film formation and growth still remains largely unexplored. Especially, the anions have been overlooked despite their high concentration in the coating solution. Considering that the anions are critical in the reactivity of metal−organic complex and the formation and/or property of functional materials, we investigated the anionic effects on the characteristics of film formation, such as film thickness and properties, in the Fe 3+ −tannic acid coating. We found that the film characteristics were strongly dictated by the counteranions (e.g., SO 4 2− , Cl − , and Br − ) of the Fe 3+ ion. Specifically, the film thickness and properties (i.e., mechanical modulus, permeability, and stability) followed the reversed anionic Hofmeister series (Br − > Cl − > SO 4 2− ). Mechanistic studies suggested that more chaotropic anions, such as Br − , might induce a more widely extended structure of the Fe 3+ −TA complexes in the coating solution, leading to thicker, harder, but more porous films. The reversed anionic Hofmeister effect was further confirmed by the additive effects of various sodium salts (NaF, NaCl, NaBr, and NaClO 4 ).

Enzyme-Mediated Kinetic Control of Fe3+–Tannic Acid Complexation for Interface Engineering

“…The permeability of Fe 3+ -TA [GOx] shells was investigated with FITC-conjugated dextrans (molecular weight (MW): 4, 20, 250, or 2000 kDa) as probes after fabricating hollow Fe 3+ -TA [GOx] capsules with polystyrene microparticles as a sacrificial template (Figure c). The low-MW dextrans (MW: 4, 20, and 250 kDa) diffused freely into the inside of the shells but the diffusion of 2000 kDa dextran was stochastically delayed as previously described, , indicating the permission of metabolic exchanges.…”

“…The permeability of Fe 3+ -TA [GOx] shells was investigated with FITC-conjugated dextrans (molecular weight (MW): 4, 20, 250, or 2000 kDa) as probes after fabricating hollow Fe 3+ -TA [GOx] capsules with polystyrene microparticles as a sacrificial template (Figure 5c). The low-MW dextrans (MW: 4, 20, and 250 kDa) diffused freely into the inside of the shells but the diffusion of 2000 kDa dextran was stochastically delayed as previously described, 47,48 indicating the permission of metabolic exchanges. Sustained cell viability was one of the requirements of SCNE materials and processes, and, in our system, the possibility might be that H 2 O 2 (and reactive oxygen species derived from H 2 O 2 in the reaction medium) would cause cell death.…”

A Natural Virucidal and Microbicidal Spray Based on Polyphenol-Iron Sols

“…51 The current method was based on our own formulation of the MPS that has been demonstrated to be stable in water for a long period of time. [39][40][41][42]50 A second E. coli plate was sprayed with only water as a negative control along with another plate of bacteria without spraying. After 24 h of culture, the CFUs were measured.…”

Universal Surface Coating with a Non-Phenolic Molecule, Sulfonated Pyrene

“…For example, dopamine does not exhibit a versatile surface-coating property without a polymerization process. It can only adhere to solid substrates, after which the polymerized dopamine, polydopamine, is formed under various conditions. ,− This phenomenon was also observed in tannic acid-based coatings. ,− ,− Tannic acid does not show a versatile surface-coating property, but the surface coating can take place when it is converted into a larger molecule by cross-linking reactions with metal ions. − ,, There was another study reporting the surface-coating property of tannic acid. Messersmith and co-workers reported tannic acid as the sole coating precursor for the formation of material-independent coatings .…”

“…Tannic acid does not show a versatile surface-coating property, but the surface coating can take place when it is converted into a larger molecule by cross-linking reactions with metal ions. [43][44][45][46][47][48][49][50][51][52]89,90 There was another study reporting the surface-coating property of tannic acid. Messersmith and coworkers reported tannic acid as the sole coating precursor for the formation of material-independent coatings.…”