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Black phosphorus (BP), a promising two-dimensional material, faces significant challenges for its applications due to its instability in air and water. Herein, molecular dynamics simulations reveal that a self-assembled ferrocene (FeCp 2 ) molecular layer can form on BP surfaces and remain stable in aqueous environments, predicting its effectiveness for passivation. This theoretical finding is corroborated by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, and optical microscopy observations. In addition, atomic force microscopy analysis confirms that ferrocene-passivated BP flakes with thicknesses of <10 nm exhibit minimal degradation over 25 days. Density functional theory calculations further show that ferrocene stabilizes BP and modulates its band gap, improving its electronic applicability. Notably, we find that the passivation of BP by metallocenes is universal because other metallocenes (VCp 2 , MnCp 2 , and NiCp 2 ) exhibit similar adsorption behaviors. These findings underscore the potential of metallocenes as versatile protective layers for BP and other materials that are not stable in air.

The high performance of two-dimensional (2D) channel membranes is generally achieved by preparing ultrathin or forming short channels with less tortuous transport through self-assembly of small flakes, demonstrating potential for highly efficient water desalination and purification, gas and ion separation, and organic solvent waste treatment. Here, we report the construction of vertical channels in graphene oxide (GO) membrane based on a substrate template with asymmetric pores. The membranes achieved water permeance of 2647 L m -2 h -1 bar -1 while still maintaining an ultrahigh rejection rate of 99.9% for heavy metal ions, which is superior to the state-of-the-art 2D membranes reported. Furthermore, the membranes exhibited excellent stability during long-term filtration experiments for at least 48 h, as well as resistance to ultrasonic treatment for over 100 minutes. The vertical channels possess very short pathway for almost direct water transport and a highly effective channel area, meanwhile the asymmetric porous template enhances the packing of the inserted GO nanosheets to avoid the swelling effect of membrane. Our work provides a simple way to fabricate vertical channels of 2D nanofiltration membranes with high water purification performance., Competing Interests: Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

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 (Mg 2+ and Ca 2+ ) 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.

Cation&otimes;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&otimes;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&otimes;3π interactions, while the solvation of the benzene molecule increases the strengths of cation&otimes;3π interactions, compared with the strengths of cation&otimes;3π interactions in the gas phase. The mechanism analyses revealed that in the presence of surrounding water molecules, the stability of cation&otimes;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&otimes;3π interactions. Moreover, AIMD simulations further underscore the practical significance of cation&otimes;3π interactions. These findings provide valuable insights into the structures and the strengths of cation&otimes;3π interactions with the effect of solvation.

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., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Effective neuroprotective agents are required to prevent neurological damage caused by reactive oxygen species (ROS) generated by cerebral ischemia-reperfusion injury (CIRI) following an acute ischemic stroke. Herein, it is aimed to develop the neuroprotective agents of cerium oxide loaded with platinum clusters engineered modifications (Pt n -CeO 2 ). The density functional theory calculations show that Pt n -CeO 2 could effectively scavenge ROS, including hydroxyl radicals (·OH) and superoxide anions (·O 2 - ). In addition, Pt n -CeO 2 exhibits the superoxide dismutase- and catalase-like enzyme activities, which is capable of scavenging hydrogen peroxide (H 2 O 2 ). The in vitro studies show that Pt n -CeO 2 could adjust the restoration of the mitochondrial metabolism to ROS homeostasis, rebalance cytokines, and feature high biocompatibility. The studies in mice CIRI demonstrate that Pt n -CeO 2 could also restore cytokine levels, reduce cysteine aspartate-specific protease (cleaved Caspase 3) levels, and induce the polarization of microglia to M2-type macrophages, thus inhibiting the inflammatory responses. As a result, Pt n -CeO 2 inhibits the reperfusion-induced neuronal apoptosis, relieves the infarct volume, reduces the neurological severity score, and improves cognitive function. Overall, these findings suggest that the prominent neuroprotective effect of the engineered Pt n -CeO 2 has a significant neuroprotective effect and provides a potential therapeutic alternative for CIRI., (© 2024 Wiley‐VCH GmbH.)

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 Au 3+ and other ions by rGO membranes. The maximum adsorption capacity for Au 3+ ions was about 16 times that of Cu 2+ ions and 10 times that of Fe 3+ ions in a mixture solution with equal proportions of Au 3+ /Cu 2+ and Au 3+ /Fe 3+ . In a mixed-ion solution containing Au 3+ :Cu 2+ :Na + :Fe 3+ :Mg 2+ of printed circuit board (PCB), the mass of Au 3+ :Cu 2+ :Na + :Fe 3+ :Mg 2+ 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.

One of the major challenges that hinder the practical application of water electrolysis lies in the design of advanced electrocatalysts toward the anodic oxygen evolution reaction (OER). In this work, a pure Co-based precatalyst of CoOOH/brownmillerite derived from the surface activation of brownmillerite by a surface acid etching method exhibits high activity and stable electrical properties toward the OER. Different from oxyhydroxide derived from in situ surface reconstruction during the electrochemical process, the growth of highly crystalline CoOOH from the brownmillerite surface enables rational control over the surface/bulk structure as well as the concentration of active sites, and this structure can be well maintained and serve as highly active sites. The catalyst shows a low overpotential of 320 mV to obtain 10 mA cm -2 and high stability in an alkaline electrolyte for the OER, which is comparable to the majority of Co-based electrocatalysts. Moreover, the appropriate interfacial interaction of the composite catalysts greatly contributes to the hydroxide insertion to improve water oxidation ability. This work proposes an effective strategy to develop high-performance metal oxide-based materials for the OER.

Cation-π interactions are essential for many chemical, biological, and material processes, and these processes usually involve an aqueous salt solution. However, there is still a lack of a full understanding of the hydrated cation-π interactions between the hydrated cations and the aromatic ring structures on the molecular level. Here, we report a molecular picture of hydrated cation-π interactions, by using the calculations of density functional theory (DFT). Specifically, the graphene sheet can distort the hydration shell of the hydrated K+ to interact with K+ directly, which is hereafter called water-cation-π interactions. In contrast, the hydration shell of the hydrated Li+ is quite stable and the graphene sheet interacts with Li+ indirectly, mediated by water molecules, which we hereafter call the cation-water-π interactions. The behavior of hydrated 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 cations adsorbed onto the graphene surface.

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., (© The Author(s) 2020. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd.)

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., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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.

Recently, we have demonstrated that highly efficient ion rejection by graphene oxide membranes can be facilely achieved using hydrated cations to control the interlayer spacing in GO membranes. By using density functional theory calculations, we have shown that different hydrated cations can also precisely control the interlayer spacings between graphene sheets, which are smaller than graphene oxide sheets; this indicates ion sieving. The interlayer distances are 9.35, 8.96 and 8.82 Å for hydrated Li+, Na+ and K+, respectively. Since the radii of the hydrated Na+ and Li+ ions are larger than that of hydrated K+, graphene membranes controlled by the hydrated K+ ion can exclude K+ and the other two cations with larger hydrated volumes. Further analysis of charge transfer and orbit analysis showed that this type of control by the hydrated cations is attributed to the strong hydrated cation-π interactions; moreover, when soaked in a salt solution, graphene membranes adsorb hydrated Na+ and Li+ and form intercalation compounds. However, it is hard to find K-doped intercalation compounds in the inner part of graphene.