Biomimetic Selective Ion Transport through Graphene Oxide Membranes Functionalized with Ion Recognizing Peptides

Membranes that differentiate ions are being actively developed to meet the needs in separation, sensing, biomedical, and water treatment technologies. Biomimetic approaches that combine bioinspired functional molecules with solid state supports offer great potential for imitating the functions and principles of biological ion channels. Here we report the design and fabrication of biomimetic graphene oxide (GO) based membranes functionalized with a peptide motif that has the capabilities for selective recognition and transport. The peptide, which has ion binding affinity to Co²⁺ ions, was adopted to enable the ion selective filtration capability and was then anchored on a GO surface. The resulting GO-based membranes show remarkable ion selectivity toward the specific ion of interest, for the transport across the membranes as in the biological ion channels. Ion recognition capability of this peptide motif successfully translates into ion specificity for selective transport. This study provides a new avenue for developing artificial ion channels via a synergistic combination of biomimetic recognition chemistry, with a novel nanoplatform such as GO

Oxygen Concentration Control of Dopamine-Induced High Uniformity Surface Coating Chemistry

Material surface engineering has attracted great interest in important applications, including electronics, biomedicine, and membranes. More recently, dopamine has been widely exploited in solution-based chemistry to direct facile surface modification. However, unsolved questions remain about the chemical identity of the final products, their deposition kinetics and their binding mechanism. In particular, the dopamine oxidation reaction kinetics is a key to improving surface modification efficiency. Here, we demonstrate that high O₂ concentrations in the dopamine solution lead to highly homogeneous, thin layer deposition on any material surfaces via accelerated reaction kinetics, elucidated by Le Chatelier’s principle toward dopamine oxidation steps in a Michael-addition reaction. As a result, highly uniform, ultra-smooth modified surfaces are achieved in much shorter deposition times. This finding provides new insights into the effect of reaction kinetics and molecular geometry on the uniformity of modifications for surface engineering techniques

Self-Tunable, Exfoliated Oxygen-Rich Flower-like MoS₂ Nanosheets for Arsenic Removal: Investigations on Substitution, Stability, and Sustainability (3S) for Maxi-Sorption

In this study, we synthesized La-incorporated O-rich defective MoS2 nanosheets by a simple, inexpensive, in situ hydrothermal reaction to self-exfoliate the bulky MoS2 layers themselves so that they can readily trap hard base anions, arsenic (arsenite and arsenate), from water. Attempting to modify MoS2 surfaces by incorporating O allows for more active sites, which is confirmed by powder XRD patterns where the exfoliated layers have a d-spacing of 0.63 nm, while the spacing for the bulky layers is 0.60 nm. The substitution of La at different equivalent ratios on the interlayer/surface improves the adsorption properties of arsenite and arsenate in simple solutions, as shown by the Langmuir adsorption density values of 0.7760 and 1.4363 mmol g–1, respectively. When the O-rich MoS2 layers were loaded with La, the adsorption densities improved, with La1.0 equiv showing the best values among the materials studied. The presence of O and S was more responsible for the removal of arsenite ions, and La and O, together with a small amount of N, were able to remove arsenate ions from water according to the well-known Pearson’s Lewis acid−base principle. The stability of the materials was characterized after the experiments, and it was found that there was no leaching of the materials by ICP-OES and the stability was maintained after 6 regeneration cycles. With the exception of phosphate, which behaves chemically similar to arsenic, the adsorption densities were not significantly affected by the mono- and divalent anions, indicating the selectivity of the prepared materials. The synthesis cost of MoOxS2–x was 2 times lower than that of bulky MoS2, and its adsorption properties were 10 times higher than those of the latter. The results suggest that La-substituted O-rich MoS2 is a potential candidate for the removal of soft and hard base metals from water