The development of stimuli-responsive membranes, often stated as smart membranes, has garnered increasing attention in recent years owing to their potential in various industrial separation processes and their ability to mimic natural biological systems. Materials suitable for such applications can dynamically adjust their physical and chemical properties, reacting to external stimuli such as temperature, pH, light, or magnetic/electric fields, thereby enabling precise control over membrane microstructure and the dynamic transport of molecules. This review offers an in-depth examination of the chemistry and responsive mechanisms of different stimuli-responsive materials, along with their integration into membrane matrices to optimize performance. Furthermore, it presents a comparative analysis of various types of stimuli-responses, illustrated with pertinent examples. Ultimately, this review highlights the outstanding challenges and future strategies for advancing smart membranes. With ongoing progress in chemistry and materials science, the development of a selective and efficient nanofiltration membrane platform is anticipated to yield significant benefits to advanced separation processes, offering more efficient and integrated technological solutions.

Silver has long been recognized for its potent antimicrobial properties, but achieving a slow and longer-term delivery of silver ions presents significant challenges. Previous efforts to control silver ion dosages have struggled to sustain release for extended periods in biomimetic environments, especially in the presence of complex proteins. This challenge is underscored by the absence of technology for sustaining antimicrobial activity, especially in the context of orthopedic implants where long-term efficacy, extending beyond 7 days, is essential. In this study, the tunable, slow, and longer-term release of silver ions from the two-dimensional (2D) nanocapillaries of graphene oxide (GO) laminates incorporated with silver ions (Ag-GO) for antimicrobial applications are successfully demonstrated. To closely mimic a physiologically relevant serum-based environment, a novel in vitro study model using 100% fetal bovine serum (FBS) is introduced as the test medium for microbiology, biocompatibility, and bioactivity studies. To emulate fluid circulation in a physiological environment, the in vitro studies are challenged with serum exchange protocols on different days. The findings show that the Ag-GO coating can sustainably release silver ions at a minimum dosage of 10 µg cm-2 day-1, providing an effective and sustained antimicrobial barrier for over ten days.

This paper shows how non-layered naturally occurring tourmaline silicates can be exfoliated into 2D structures for use in fabrics and 3D printed biomedical health monitoring devices.

Owing to the active production of metabolites during reproduction and growth, microbial cells have been incessantly explored for their potential in the fabrication and functionalization of inorganic materials. Yeast cells, which are nonpathogenic microbes, exhibit biotransformation reactions and the potential to modify functional groups when grown under fermentative conditions. Here, we attempted to delay graphite chunks into graphene flakes by incubating them with dry Sachharomyces cerevisae powder. The evident delamination/thinning of graphene layers was demonstrated using microscopic and spectroscopic analyses which confirmed the exfoliation of graphite to few-layer graphene (FLG). The gate-to-gate life cycle assessment (LCA) of the developed process established the sustainability and environmental hotspots for the approach. Our study demonstrates the facile, green, and sustainable exfoliation of graphite using off-the-shelf materials in laboratories or kitchens and can be scaled up to industry levels. Yeast cells were also explored for the exfoliation of another 2D material, MoS2, and showed the potential to flake off the bulk structure into few MoS2 sheets.

Molecular diffusion and surface dynamics within two covalent organic frameworks (COFs) have been investigated using nuclear magnetic resonance (NMR) pulsed-field gradient (PFG) and relaxation. The effect of chemical functionalities of the COFs on the effective self-diffusivity of the probe molecules within the pore space and the adsorbate/adsorbent interactions were investigated. In particular, diffusion and interaction of water, methanol, n-octane, and 1,3,5-triisopropylbenzene (1,3,5-TIPB) within COF-SIOC and COF-DHTA were assessed. The two types of COFs used in this study possessed a dual pore Kagome structure consisting of larger hexagonal and smaller triangular pores. The PFG NMR results show the presence of two distinct diffusion coefficients for small probe molecules, such as water, methanol, and n-octane. This behaviour is attributed to their relatively smaller kinetic diameters, allowing them to access both smaller and larger pores in the COFs. In contrast, the PFG diffusion plot for 1,3,5-TIPB showed a single component linear behaviour, which is attributed to diffusion through the larger hexagonal pores only, as a result of a much larger kinetic diameter of 1,3,5-TIPB compared to the other probe molecules, which prevents access to the smaller triangular pores. The presence of functional groups affects surface interactions between the probe molecules and the surface of the COFs. The NMR T-1/T-2 relaxation measurements reveal a higher strength of surface interaction for water molecules in COF-DHTA compared to COF-SIOC, which is attributed to the presence of hydrophilic -OH groups in COF-DHTA. Conversely, a higher strength of surface interactions was achieved for n-octane in COF-SIOC, due to the hydrophobic nature of this material. This work reports new insights into transport and dynamics of molecules confined in COFs, which can help design and optimisation of such pore structures in applications such as separation and catalysis.

We report the synthesis and structural characterization of a series of heterometallic rings templated via alkylammonium or imidazolium cations. The template and preference of each metal's coordination geometry can control the structure of heterometallic compounds, leading to octa-, nona-, deca-, dodeca-, and tetradeca-metallic rings. The compounds were characterized by single-crystal X-ray diffraction, elemental analysis, magnetometry, and EPR measurements. Magnetic measurements show that the exchange coupling between metal centres is antiferromagnetic. EPR spectroscopy shows that the spectra of {Cr7Zn} and {Cr9Zn} have S = 3/2 ground states, while the spectra of {Cr12Zn2} and {Cr8Zn} are consistent with S = 1 and 2 excited states. The EPR spectra of {(ImidH)-Cr6Zn2}, {(1-MeImH)-Cr8Zn2}, and {(1,2-diMeImH)-Cr8Zn2} include a combination of linkage isomers. The results on these related compounds allow us to examine the transferability of magnetic parameters between compounds.

As a natural polymer, cellulose is abundant, low-cost,robust,and biodegradable and can be chemically modified. This work exploresthe enhancement of mechanical, thermal, and flexoelectric propertiesof three-dimensional (3D)-printed carboxymethyl cellulose (CMC) dueto the addition of mechanically exfoliated hexagonal boron nitride(hBN). hBN was observed to act as a rheology modifier, and CMC reinforcedwith 2% hBN exhibited the maximum apparent viscosity of 12.24 Pa & BULL;sat a shear rate of 100 s(-1). The 0.5% hBN/CMC filmexhibited the highest mechanical and thermal stability. A flexoelectricenergy harvester was fabricated out of 3D-printed hBN/CMC compositesto test the effectiveness of strain-induced charge production. Byvarying the load resistance and applied pressure, we were able tomeasure the voltage and current flowing through the device. We foundthat a load resistance of 180 k & omega; connected across a 2% hBN/CMCdevice resulted in the highest power delivery of 5.5 nW. When mechanicalstrain is applied, a charge state fluctuation and spontaneous polarizationin the hBN/CMC matrix are seen. This phenomenon can be explained basedon the flexoelectric energy-harvesting mechanism, supported by densityfunctional theory (DFT) calculations.

Two-dimensional (2D) materials offer a prospect of membranes that combine negligible gas permeability with high proton conductivity and could outperform the existing proton exchange membranes used in various applications including fuel cells. Graphene oxide (GO), a well-known 2D material, facilitates rapid proton transport along its basal plane but proton conductivity across it remains unknown. It is also often presumed that individual GO monolayers contain a large density of nanoscale pinholes that lead to considerable gas leakage across the GO basal plane. Here we show that relatively large, micrometer-scale areas of monolayer GO are impermeable to gases, including helium, while exhibiting proton conductivity through the basal plane which is nearly two orders of magnitude higher than that of graphene. These findings provide insights into the key properties of GO and demonstrate that chemical functionalization of 2D crystals can be utilized to enhance their proton transparency without compromising gas impermeability.

We report an eco-friendly, economical and green approach to synthesize few-layers of functionalised graphene from large graphite flakes and chunks without the aid of any external mechanical forces. Here, we demonstrate a fermentation process aided by friendly microbes like yeast to effortlessly exfoliate graphite to graphene with a high yield. The evident flaking and delamination of graphene layers, characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy, confirmed the successful exfoliation of graphite to few-layer graphene (~10 nm in thickness). The gate-to-gate life cycle assessment of the developed method identified the environmental hotspots of the process. The biofunctionalized graphene (as suggested by Fourier transform infrared (FTIR) spectroscopy) was explored for its application in NH4+ sensing, where it exhibited the limit of detection to be ~20 ppm. The detection mechanism was explained based on Raman and FTIR spectroscopy which revealed the functional state and lattice changes introduced in the graphene layers by NH4+ ions. Our study demonstrates a novel, cost-effective exfoliation of graphite using off-the-shelf materials in laboratories or kitchens and has the potential to be scaled up to industry levels. The yeast cells also exhibited their potential in flaking off the bulk MoS2 structure into few-layer MoS2 sheets.

Correction for 'Synthesis and characterization of heterometallic rings templated through alkylammonium or imidazolium cations' by Rajeh Alotaibi et al., Dalton Trans., 2023, 52, 7473-7481, https://doi.org/10.1039/D3DT00982C.

Spent mushroom compost (SMC) already broken down into smaller particles by fungal action is an ideal material for producing biogas. Two cycles of five solid-state anaerobic digesters (SS-ADs) with different mix-ratio of SMC and switchgrass (SG) were operated at feedstock-to-effluent ratio of 2 at a temperature 35 ± 2°C. The total solids concentration of the digester was kept at ∼17%. Initial biogas production observed during the start-up of the digester confirmed the presence of readily available extractives for digestion. In the first cycle, the highest methane yield was observed in SMC 0 (0% SMC + 100% SG) of 28.82 l/kg VS/d and the lowest yield was observed in SMC 4 (100% SMC + 0% SG) as 10.32 l/kg VS/d. The substrate containing 100% SG (SMC 0) recorded the highest cumulative biogas yield of 295.43 l/kg VS in 63 days. The digesters with higher SMC fraction showed lower methane production, low pH value and high volatile fatty acids content upon decomposition. The SS-ADs having SMC/SG of 50 : 50 showed more than 2 times methane production in comparison with SS-ADs having SMC as sole substrate. An estimation of volumetric productivity also established a linear relationship with the SMC/SG ratio.

Graphene oxide (GO) membranes are known to have a complex morphology that depends on the degree of oxidation of the graphene flake and the membrane preparation technique. In this study, using Grand Canonical Monte Carlo simulations, we investigate the mechanism of swelling of GO membranes exposed to different relative humidity (RH) values and show how this is intimately related to the graphene surface chemistry. We show that the structure of the GO membrane changes while the membrane adsorbs water from the environment and that graphene oxide flakes become charged as the membrane is loaded with water and swells. A detailed comparison between simulation and experimental adsorption data reveals that the flake surface charge drives the water adsorption mechanism at low RH when the membrane topology is still disordered and the internal pores are small and asymmetric. As the membrane is exposed to higher RH (80%), the flake acquires more surface charge as more oxide groups deprotonate, and the pores grow in size, yet maintain their disordered geometry. Only for very high relative humidity (98%) does the membrane undergo structural changes. At this level of humidity, the pores in the membrane become slit-like but the flake surface charge remains constant. Our results unveil a very complex mechanism of swelling and show that a single molecular model cannot fully capture the ever-changing chemistry and morphology of the membrane as it swells. Our computational procedure provides the first atomically resolved insight into the GO membrane structure of experimental samples.

We perform first principles investigation to calculate the electronic bandgap of monolayer CrI 3 and determine its electronic nature using SIESTA. The bandgap of CrI 3 as measured by GGA-PBE exchange correlational differed from earlier experimental and theoretical findings. In this paper, we demonstrate that the bandgap value of monolayer CrI 3 may be obtained by applying GGA-BLYP exchange correlational and modifying the Hubbard parameters - effective Coulomb parameter (U), effective exchange parameter (J), and Fermi cut off function (ω). CrI 3 exhibits a bandgap of 1 eV in the spin-up channel and shows a direct bandgap characteristics. In case of spin-down channel, it exhibits an indirect bandgap characteristics with a band gap value of ~ 2.5 eV.

Van der Waals (vdW) heterostructures continue to attract intense interest as a route of designing materials with novel properties that cannot be found in nature. Unfortunately, this approach is currently limited to only a few layers that can be stacked on top of each other. Here, we report a bulk vdW material consisting of superconducting 1H TaS2 monolayers interlayered with 1T TaS2 monolayers displaying charge density waves (CDW). This bulk vdW heterostructure is created by phase transition of 1T-TaS2 to 6R at 800 °C in an inert atmosphere. Its superconducting transition (Tc) is found at 2.6 K, exceeding the Tc of the bulk 2H phase. Using first-principles calculations, we argue that the coexistence of superconductivity and CDW within 6R-TaS2 stems from amalgamation of the properties of adjacent 1H and 1T monolayers, where the former dominates the superconducting state and the latter the CDW behavior.

The properties of water at interfaces have long been known to differ from those of bulk water in many distinctive ways. More recently, specific confinement effects different from mere interfacial effects have been discovered upon enclosing water in very narrow cylindrical pores and planar surfaces as offered by nanotubes and slit pores, respectively. Using experimental and theoretical THz spectroscopy, we elucidate nanoconfinement effects on the H-bond network of stratified water lamellae that are hosted within graphene-based two-dimensional pores. Characteristic confinement-induced changes of the THz response are traced back to the level of structural dynamics, notably distinct resonances due to intralayer and interlayer H-bonds at correspondingly low and high intermolecular stretching frequencies and impact of dangling (free) OH bonds at the water-graphene interface that enormously broaden the librational band in sufficiently narrow pores. The interplay of these molecular effects causes characteristic changes of the THz lineshape upon nanoconfining water.

The discovery of novel materials that are stable at ambient conditions with emergent functionalities is a pressing need of the 21st century to keep the pace of social and technological advancement in a sustainable manner. Nanotechnology and nanomaterials are one of this kind and the current era has already witnessed several groundbreaking discoveries of materials and disruptive technological advancements. Starting from 0D fullerene, the invention of 1D carbon nanotubes, and most recently 2D graphene, all are allotropes of carbon, have brought a lot of research opportunities to understand different physical and chemical phenomena at atomic and molecular scales and to convert such properties into useful applications. Among them, 2D materials find special attention due to unique properties such as ballistic carrier transport, immunity from substrate effects and commendable in plane mechanical robustness. However, the library of such materials is limited, and one can see that most of the technically viable materials that are already industrialized in a large scale belong to the class of non-van der Waals materials. The effect of confinement in one dimension on non-van der Waals materials remains unexplored owing to the difficulty in fabricating these materials to the ultra-thin limit with large lateral size or area. Recent advancement of cleaving non-van der Waals bulk materials to their ultra-thin counter parts through the state-of-the-art liquid phase exfoliation approach leads to renewed research interest among scientific community. The existence of cleaving/parting planes in certain directions of non-van der Waals materials, where the bonding strength is relatively weak compared to other crystallographic directions of the bulk crystal, facilitate smooth exfoliation when subjected to shear force through suitable methods. Herein, we attempt to discuss the rationale of such methods in the synthesis of non-van der Waals 2D materials that possess cleavage/parting planes with a special attention to natural ores, and to review the recent progress made in non-van der Waals two-dimensional materials with a special emphasis on emergent magnetism, catalysis, energy storage, and optoelectronics and related applications.

There has been no experimental evidence for ferromagnetic ordering in isotropic atomically thin two-dimensional crystals, until a bilayer Cr2Ge2Te6 and a three-atom thick monolayer CrI3 is shown to retain ferromagnetic ordering at finite temperatures. Here, we demonstrate successful isolation of a nonvan der Waals-type ultrathin nanosheet of FeS2 derived from naturally occurring pyrite mineral (FeS2) by means of liquid-phase exfoliation. Structural characterizations imply that (111)-oriented sheets are predominant and are supported theoretically by means of density functional theory surface energy calculations. Spin-polarized density theory calculations further predicted that (111)-oriented three-atom thick pyrite sheets have a stable ferromagnetic ground state different from their diamagnetic bulk counterparts. This theoretical finding is evaluated by experimentally employing low-temperature superconducting quantum interference device measurements, and an anomalous ferromagnetic kind of behavior is observed.