Cation–π Interactions in Graphene‐Containing Systems for Water Treatment and Beyond

Abstract

was also recognized. [2] In addition to these forces, one intriguing noncovalent interaction: cation-π interaction, has emerged as an intermolecular force of great significance in chemistry, biology, and materials science. [3] The cation-π interactions basically refers to the interplay between cations and the π electron cloud of an aromatic system. It plays a great role in biological systems for molecular recognition, protein-protein interactions, and the maintenance of macromolecular structures. It also occurs in protein-ligand interactions and protein-DNA complexes. In structural biology, the positively charged amino acids interact with aromatic amino acids, which contribute to the formation of complex protein structures. The amide NHs are in close contact with the aromatic ring of another amino acid in the protein crystal structures. [4] The cation-π interactions are of great importance to protein stability. There is at least one intermolecular cation-π interaction in half of proteins and one third of homodimers, [5] making significant contributions to the tertiary and quaternary protein structures caused by protein folding. In addition, metallic cations, such as Na + , K + , Cu 2+ , Fe 2+ , Ca 2+ , exist in many enzymes. Their interactions with the π systems in protein structures cannot be ignored. In molecular neurobiology, many studies have proved that receptors bind the neurotransmitters through cation-π interactions. [6] The cation-π interaction is electrostatic in nature because the major contributions arise from the electrostatic attractions between cations and the quadrupole moment of the aromatics. [7] As a result, the strength of cation-π interactions can be the strongest among the noncovalent interactions, several times greater than others. It can also be regulated to be weak, depending on the type of cations and the nature of the π system. The adjustability of cation-π interaction offers a potential strategy to modify the neighboring environment where it is involved.Graphene, a 2D carbon network, with carbon atoms jointed together in a hexagonal honeycomb matrix, can be taken as a novel aromatic macromolecule from certain points of view. The unique structure endows it with excellent physicochemical, electronic, optical, thermal, and mechanical properties, leading to its potential applications in broad fields. [8] The interplay between cations and the delocalized polarizable π electrons of graphene, would alter the intrinsic characteristics of graphene-based structures and impart influences on the performance of graphene-based devices.Cation-π interactions are common in nature, especially in organisms. Their profound influences in chemistry, physics, and biology have been continuously investigated since they were discovered in 1981. However, the importance of cation-π interactions in materials science, regarding carbonaceous nanomaterials, has just been realized. The interplay between cations and delocalized polarizable π electrons of graphene would bring about significant changes to the intrinsic...

Ultrahigh Water Permeance of Reduced Graphene Oxide Membrane for Radioactive Liquid Waste Treatment

“…The UV-vis absorption spectra (see Figure S2c) showed that the characteristic peaks at ≈230 nm were attributed to π-π* from the aromatic rings. The results are consistent with the previous reports [27,[36][37][38].…”

Two‐Dimensional Polydopamine Positive Electrodes for High‐Capacity Alkali Metal‐Ion Storage

“…When GO is reduced to rGO during the hydrothermal process, rGO tends to interact with adjacent rGOs through hydrophobic and π-π interactions which trigger the aggregation of the rGO sheets. [20] Interestingly, the polydopamine coating on the rGO sheets prevents such aggregation of the rGO sheets probably due to the various hydrophilic oxygen and nitrogen functional groups of polydopamine. Furthermore, energy-dispersive X-ray (EDX) mapping about carbon, oxygen, and nitrogen for TDPD confirmed a homogeneous coating of polydopamine on the GO sheets ( Figure S4).…”

Transcriptome analysis reveals that multiple metabolic pathways operate in Zea mays roots subjected to graphene

“…10). When the roots of maize seedlings grown in soil are exposed to gaphene, the N and K contents of soil would be elevated because of the cation-π interactions in graphene, which lead to the accumulation of cations on the graphene surface [65]. Thus, the transporters in the root (such as Nitrate transporter, nrt2.2; potassium transporter 5, HAK20) may recognize the corresponding signals and trigger the expression increase of transporter genes, and the change of phytohormones, including auxin, cytokinin and gibberellin, and so on.…”