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Hydrated cation–π interactions at liquid–solid interfaces between hydrated cations and aromatic ring structures of carbon-based materials are pivotal in many material, biological, and chemical processes, and water serves as a crucial mediator in these interactions. However, a full understanding of the hydrated cation–π interactions between hydrated alkaline earth cations and aromatic ring structures, such as graphene remains elusive. Here, we present a molecular picture of hydrated cation–π interactions for Mg2+ and Ca2+ by using the density functional theory methods. Theoretical results show that the graphene sheet can distort the hydration shell of the hydrated Ca2+ to interact with Ca2+ directly, which is water–cation–π interactions. In contrast, the hydration shell of the hydrated Mg2+ is quite stable and the graphene sheet interacts with Mg2+ indirectly, mediated by water molecules, which is the cation–water–π interactions. These results lead to the anomalous order of adsorption energies for these alkaline earth cations, with hydrated Mg2+–π < hydrated Ca2+–π when the number of water molecules is large (n ≥ 6), contrary to the order observed for cation–π interactions in the absence of water molecules (n = 0). The behavior of hydrated alkaline earth cations adsorbed on a graphene surface is mainly attributed to the competition between the cation–π interactions and hydration effects. These findings provide valuable details of the structures and the adsorption energy of hydrated alkaline earth cations adsorbed onto the graphene surface. [ABSTRACT FROM AUTHOR]

Cation⊗3π interactions play a special role in the behaviors of biological molecules and carbon-based materials in aqueous solutions, yet the effects of solvation on these interactions remain poorly understood. This study examines the sequential attachment of water molecules to cation⊗3π systems (cation = Li⁺, Na⁺, K⁺), revealing that solvation influences interaction strengths in opposing ways: solvation of the metal cation decreases the strengths of cation⊗3π interactions, while the solvation of the benzene molecule increases the strengths of cation⊗3π interactions, compared with the strengths of cation⊗3π interactions in the gas phase. The mechanism analyses revealed that in the presence of surrounding water molecules, the stability of cation⊗3π systems is generally enhanced by cation–π, π–π, water–π, and water–ion interactions, while water–water interactions typically have a destabilizing effect. In addition, the primary effect of water molecules at different adsorption sites is to modulate the Coulombic multipole–multipole interactions and the overlap between monomeric charge distributions, thereby influencing the changes in strengths of cation⊗3π interactions. Moreover, AIMD simulations further underscore the practical significance of cation⊗3π interactions. These findings provide valuable insights into the structures and the strengths of cation⊗3π interactions with the effect of solvation. [ABSTRACT FROM AUTHOR]

Black phosphorus (BP) and its two-dimensional derivative (2D-BP) have garnered significant attention as promising anode materials for electrochemical energy storage devices, including next-generation fast-charging batteries. However, the interactions between BP and light metal ions, as well as how these interactions influence BP's electronic properties, remain poorly understood. Here, we employed density functional theory (DFT) to investigate the effects of monovalent (Li+ and Na+) and divalent (Mg2+ and Ca2+) ions on the valence electronic structure of 2D-BP. Molecular orbital analysis revealed that the adsorption of divalent cations can significantly reduce the band gap, suggesting an enhancement in charge transfer rates. In contrast, the adsorption of monovalent cations had minimal impact on the band gap, suggesting the preservation of 2D-BP's intrinsic electrical properties. Energetic and charge analyses indicated that the extent of charge transfer primarily governs the ability of ions to modulate 2D-BP's electronic structure, especially under high-pressure conditions where ions are in close proximity to the 2D-BP surface. Moreover, charge polarization calculations revealed that, compared with monovalent cations, divalent cations induced greater polarization, disrupting the symmetry of the pristine 2D-BP and further influencing its electronic characteristics. These findings provide a molecular-level understanding of how ion interactions influence 2D-BP's electronic properties during ion-intercalation processes, where ions are in close proximity to the 2D-BP surface. Moreover, the calculated diffusion barrier results revealed the potential of 2D-BP as an effective anode material for lithium-ion, sodium-ion, and magnesium-ion batteries, though its performance may be limited for calcium-ion batteries. By extending our understanding of interactions between ions and 2D-BP, this work contributes to the design of efficient and reliable energy storage technologies, particularly for the next-generation fast-charging batteries. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS), a fundamental material in the fabrication of microfluidic devices, suffers from nonspecific adsorption of biological samples due to its hydrophobic nature. Herein, by employing a radiation-induced grafting strategy to introduce hydrophilic functional groups onto the PDMS surface, a significant improvement in hydrophilicity is achieved, leading to a notable reduction in the contact angle by up to ∼90° and improvement of antifouling performance against biological samples. Effects between monomer concentration, grafting efficiency, and mechanical integrity are balanced to optimize the grafting process, achieving promised hydrophilicity enhancement while the mechanical properties are not degraded. The content of carboxyl groups exposed on the surface of grafted PDMS was computationally analyzed using MD simulations, which revealed the key role of carboxyl groups in the wettability of the PDMS surface. Our study extensively showcases the effective grafting of acrylic acid onto PDMS, which is characterized by diverse grafting rates. Remarkably, the hydrophilic modification is stable over time compared to conventional plasma treatment, offering a more reliable and enduring strategy, and making it a valuable enhancement for PDMS chips with extensive applications. [ABSTRACT FROM AUTHOR]

Membrane fouling during long-term usage severely restricts the practical application of membrane separation technology for oil-in-water emulsion treatment. Underwater superoleophobic/superhydrophilic membrane with superior self-cleaning and flux recovery performance is highly desirable, owing to its high anti-fouling ability in an oil-in-water emulsion. Herein, a polyglycidyl methacrylate-/iminodiacetic acid (IDA)/Fe(III) superhydrophilic layer was fabricated onto a polyvinylidene fluoride (PVDF) microfiltration membrane via radiation-induced graft polymerization, and subsequent adsorption of Fe(III) as the photo-Fenton activation site, labeled as Fe@PVDF, in which the loading capacity of Fe(III) was 18.31 wt%. The grafted layer acts as both, an underwater superoleophobic/superhydrophilic layer (OCA˃150o) for highly effective oil-in-water emulsion separation (99.4 %) and as a photo-Fenton activation layer for self-cleaning in 10 min under visible light irradiation with high flux (⁓2300 L m−2 h−1 bar−1). The mineralization of contaminants on the membrane surface was then systematically investigated using a series of experiments, X-ray absorption fine structure (XAFS) measurements, and density functional theory (DFT) calculations, demonstrating that the Fe/IDA site with an Fe(III) atom acts as the active site with an optimal energy gap for photo-Fenton self-cleaning activation and greatly accelerates the Fe (III) to Fe (II) cycle. Moreover, our work shows a pathway for photo-Fenton self-cleaning membranes combining excellent stability (15 cycles), and satisfactory oil-in-water emulsion separation with quick and reliable flux recovery performance, revealing their huge potential application in advanced sewage treatment. [Display omitted] • The Fe@PVDF was fabricated via RIGP in which the loading amount of Fe(III) was 18.31 wt%. • The grafted layer acts as an underwater superoleophobic/superhydrophilic layer and a photo-Fenton self-cleaning layer. • The high-loading Fe (III) membrane with maximum atom efficiency accelerates the photo-Fenton self-cleaning process in 10 min. • The Fe@PVDF shows satisfactory stability, oil/water emulsion separation, and fast and robust flux recovery performance. • The synergistic effect of active sites and activation mechanism were revealed via XAFS and DFT. [ABSTRACT FROM AUTHOR]

Lithium plays an increasingly important role in scientific and industrial processes, and it is extremely important to extract lithium from a high Mg2+/Li+ mass ratio brine or to recover lithium from the leachate of spent lithium-ion batteries. Conventional wisdom shows that Li+ with low valence states has a much weaker adsorption (and absorption energy) with graphene than multivalent ions such as Mg2+. Here, we show the selective adsorption of Li+ in thermally reduced graphene oxide (rGO) membranes over other metal ions such as Mg2+, Co2+, Mn2+, Ni2+, or Fe2+. Interestingly, the adsorption strength of Li+ reaches up to 5 times the adsorption strength of Mg2+, and the mass ratio of a mixed Mg2+/Li+ solution at a very high value of 500 : 1 can be effectively reduced to 0.7 : 1 within only six experimental treatment cycles, demonstrating the excellent applicability of the rGO membranes in the Mg2+/Li+ separation. A theoretical analysis indicates that this unexpected selectivity is attributed to the competition between cationâ€" Ď€ interaction and steric exclusion when hydrated cations enter the confined space of the rGO membranes. [ABSTRACT FROM AUTHOR]

We show the experimental achievement of dry GO membranes with interlayer spacings in the range from 7.09 Å to 8.72 Å, tuned and fixed by salts. We found that the interlayer spacings were dominated by the anions or the groups with negative charges in between the GO membranes. Density functional theory (DFT) calculations reveal that the highly efficient tuning of the interlayer spacing in dry GO membranes is due to ion‐π interactions on the graphene sheets, together with the steric effects of anions in between the GO sheets. The findings are helpful for extending their potential applications including chemical sensors, nanomaterial devices preparation, chemical catalysis and synthesis, and gas separation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synergy of hydroxyl and amidoxime promotes the adsorption of uranium. • The effect of anions on uranium adsorption has been evaluated in detail. • The mechanism of fluoride inhibiting uranium adsorption is revealed. • NWF- g -PGMA-AO is suitable for removing trace uranium from nuclear effluents. The extraction of uranium from nuclear effluents is both conducive to the recycling of nuclear fuel and reduces environmental pollution. Adsorbents are widely regarded as the most promising materials for trace uranium extraction; however, the adsorption of trace uranium from high-salinity environments is a challenge for adsorbents used to recover uranium from nuclear effluents. In this study, four different irradiation-functionalized adsorbents were fabricated and evaluated to screen suitable adsorbents for the removal of trace uranium from nuclear effluents. We found that the adsorbent with synergistic adsorption groups (NWF- g -PGMA-AO) exhibited the most distinctive trace uranium removal efficiency and robust stability in acidic, alkaline, and high-salinity environments. It was the synergistic involvement of hydroxyls in the coordination of amidoximes with uranium that enhanced the binding energy of uranium to NWF- g -PGMA-AO, thus improving its performance. In addition, the residual uranium concentration decreased to the maximum allowable emission concentration of 50 ppb over a wide pH range, with a minimum concentration of 9.35 ppb. Interestingly, nitrate, sulfate, phosphate, and chloride anions in the effluents did not decrease the uranium removal efficiency, whereas fluoride considerably reduced the efficiency, and the removal ratio was negatively correlated with fluoride concentration. This is attributed to the formation of [UO 2 F n ]2−n (n = 1, 2, 3, 4) species, which exhibit a decreasing affinity for adsorbents with increasing fluorine atoms as revealed by density functional theory calculations. This work makes a stride in designing superior adsorbents with synergistic adsorption groups for extracting trace uranium from nuclear effluents. [ABSTRACT FROM AUTHOR]

[Display omitted] • Large-size and high-density Fe sites photo-Fenton catalysts were fabricated for H 2 O 2 activation. • The chelated Fe(III) provides a well-defined reaction microenvironment with maximum atom efficiency. • The high loading Fe (III) catalyst can remove various model organic pollutants effectively. • U- g -PAO/Fe shows excellent catalytic activity in a wide range of pH, even in the process of multiple cycles. • XAFS and DFT revealed the coordination relationship of active sites and activation mechanism. The maximum exposure of active sites is the key to obtaining high reaction activity for supported metal catalysts. Single-atom metal sites and ultra-small metal clusters have received great attention because of their superior catalytic activities compared to their aggregated counterparts. However, developing high-density metal clusters with high activity and adequate stability remains a major challenge in practical applications. Herein, we demonstrate that highly dispersed and active Fe sites for heterogeneous Photo-Fenton systems can be chelated into graft chains on ultrahigh molecular weight polyethylene (UHMWPE) fibers via radiation-induced graft polymerization (RIGP) and subsequent modification, labeled as U- g -PAO/Fe. The amidoxime chelated Fe(III) catalyst, in which the loading amount of chelated Fe(III) is 24.04 wt%, exhibits remarkably efficient removal of ofloxacin within 35 min by activating H 2 O 2 under visible light irradiation. The catalytic activities and stability of U- g -PAO/Fe were evaluated by the removal of various model organic pollutants and multiple recycles of degradation, demonstrating superior catalytic activities over a wide pH range (2–10) for the activation of H 2 O 2 than a typical Fenton catalyst. Furthermore, the graft macromolecular chains of chelated Fe(III) provide a well-defined reaction microenvironment with maximum atom efficiency. X-ray absorption fine structure (XAFS) and density functional theory calculations (DFT) revealed that the unique active sites [Amidoxime-Fe(OH)(H 2 O) 3 ]2+ of U- g -PAO/Fe considerably activated H 2 O 2 decomposition under artificial sunlight irradiation. Our study presents a novel idea for the design and synthesis of highly dispersed and reactive Fe-based Photo-Fenton catalysts for practical applications in environmental remediation. [ABSTRACT FROM AUTHOR]

There is a considerable amount of work that shows the biomagnetism of organic components without ferromagnetic components at the molecular level, but it is of great challenge to cover the giant gap of biomagnetism between their experimental and theoretical results. Here we show that the diamagnetism of aromatic peptides is greatly enhanced for about 11 times by self-assembling, reaching two orders of magnitude higher than the mass susceptibility of pure water. The self-assembly of aromatic rings in the peptide molecules plays the key role in such a strong diamagnetism. [ABSTRACT FROM AUTHOR]

The recovery of gold from water is an important research area. Recent reports have highlighted the ultrahigh capacity and selective extraction of gold from electronic waste using reduced graphene oxide (rGO). Here, we made a further attempt with the thermal rGO membranes and found that the thermal rGO membranes also had a similarly high adsorption efficiency (1.79 g gold per gram of rGO membranes at 1000 ppm). Furthermore, we paid special attention to the detailed selectivity between Au3+ and other ions by rGO membranes. The maximum adsorption capacity for Au3+ ions was about 16 times that of Cu2+ ions and 10 times that of Fe3+ ions in a mixture solution with equal proportions of Au3+/Cu2+ and Au3+/Fe3+. In a mixed-ion solution containing Au3+:Cu2+:Na+:Fe3+:Mg2+ of printed circuit board (PCB), the mass of Au3+:Cu2+:Na+:Fe3+:Mg2+ in rGO membranes is four orders of magnitude higher than the initial mass ratio. A theoretical analysis indicates that this selectivity may be attributed to the difference in the adsorption energy between the metal ions and the rGO membrane. The results are conducive to the usage of rGO membranes as adsorbents for Au capture from secondary metal resources in the industrial sector. [ABSTRACT FROM AUTHOR]

Under ambient conditions, the only known valence state of calcium ions is +2, and the corresponding crystals with calcium ions are insulating and nonferromagnetic. Here, using cryo-electron microscopy, we report direct observation of two-dimensional (2D) CaCl crystals on reduced graphene oxide (rGO) membranes, in which the calcium ions are only monovalent (i.e. +1). Remarkably, metallic rather than insulating properties are displayed by those CaCl crystals. More interestingly, room-temperature ferromagnetism, graphene–CaCl heterojunction, coexistence of piezoelectricity-like property and metallicity, as well as the distinct hydrogen storage and release capability of the CaCl crystals in rGO membranes are experimentally demonstrated. We note that such CaCl crystals are obtained by simply incubating rGO membranes in salt solutions below the saturated concentration, under ambient conditions. Theoretical studies suggest that the formation of those abnormal crystals is attributed to the strong cation-π interactions of the Ca cations with the aromatic rings in the graphene surfaces. The findings highlight the realistic potential applications of such abnormal CaCl material with unusual electronic properties in designing novel transistors and magnetic devices, hydrogen storage, catalyzers, high-performance conducting electrodes and sensors, with a size down to atomic scale. [ABSTRACT FROM AUTHOR]

The effect of cationic concentration on controlling the interlayer spacings of graphene oxide (GO) membranes is systemically studied. It was found that a higher concentration leads to narrower interlayer spacings, and thus, ions in salt solutions were effectively rejected. This provides a new avenue for ion separation using graphene-based membranes. [ABSTRACT FROM AUTHOR]