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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]

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]

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 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. 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. Here, the authors report the construction of vertical channels in graphene oxide membranes based on a substrate template with asymmetric pores demonstrating high flux and metal ion rejection. [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]

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]

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. [ABSTRACT FROM AUTHOR]

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.

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.