Manipulating the surface energy, and thereby the wetting properties of solids, has promise for various physical, chemical, biological and industrial processes. Typically, this is achieved by either ...chemical modification or by controlling the hierarchical structures of surfaces. Here we report a phenomenon whereby the wetting properties of vermiculite laminates are controlled by the hydrated cations on the surface and in the interlamellar space. We find that vermiculite laminates can be tuned from superhydrophilic to hydrophobic simply by exchanging the cations; hydrophilicity decreases with increasing cation hydration free energy, except for lithium. The lithium-exchanged vermiculite laminate is found to provide a superhydrophilic surface due to its anomalous hydrated structure at the vermiculite surface. Building on these findings, we demonstrate the potential application of superhydrophilic lithium exchanged vermiculite as a thin coating layer on microfiltration membranes to resist fouling, and thus, we address a major challenge for oil-water separation technology.
Intelligent transport of molecular species across different barriers is critical for various biological functions and is achieved through the unique properties of biological membranes1-4. Two ...essential features of intelligent transport are the ability to (1) adapt to different external and internal conditions and (2) memorize the previous state5. In biological systems, the most common form of such intelligence is expressed as hysteresis6. Despite numerous advances made over previous decades on smart membranes, it remains a challenge to create a synthetic membrane with stable hysteretic behaviour for molecular transport7-11. Here we demonstrate the memory effects and stimuli-regulated transport of molecules through an intelligent, phasechanging MoS2 membrane in response to external pH. We show that water and ion permeation through 1T' MoS2 membranes follows a pH-dependent hysteresis with a permeation rate that switches by a few orders of magnitude. We establish that this phenomenon is unique to the 1T' phase of MoS2, due to the presence of surface charge and exchangeable ions on the surface. We further demonstrate the potential application of this phenomenon in autonomous wound infection monitoring and pH-dependent nanofiltration. Our work deepens understanding of the mechanism of water transport at the nanoscale and opens an avenue for the development of intelligent membranes.
Intelligent transport of molecular species across different barriers is critical for various biological functions and is achieved through the unique properties of biological membranes
. Two essential ...features of intelligent transport are the ability to (1) adapt to different external and internal conditions and (2) memorize the previous state
. In biological systems, the most common form of such intelligence is expressed as hysteresis
. Despite numerous advances made over previous decades on smart membranes, it remains a challenge to create a synthetic membrane with stable hysteretic behaviour for molecular transport
. Here we demonstrate the memory effects and stimuli-regulated transport of molecules through an intelligent, phase-changing MoS
membrane in response to external pH. We show that water and ion permeation through 1T' MoS
membranes follows a pH-dependent hysteresis with a permeation rate that switches by a few orders of magnitude. We establish that this phenomenon is unique to the 1T' phase of MoS
, due to the presence of surface charge and exchangeable ions on the surface. We further demonstrate the potential application of this phenomenon in autonomous wound infection monitoring and pH-dependent nanofiltration. Our work deepens understanding of the mechanism of water transport at the nanoscale and opens an avenue for the development of intelligent membranes.
Nature 616, 719-723, 2023 Intelligent transport of molecular species across different barriers is
critical for various biological functions and is achieved through the unique
properties of biological ...membranes. An essential feature of intelligent
transport is the ability to adapt to different external and internal conditions
and also the ability to memorise the previous state. In biological systems, the
most common form of such intelligence is expressed as hysteresis. Despite
numerous advances made over previous decades on smart membranes, it is still a
challenge for a synthetic membrane to display stable hysteretic behaviour for
molecular transport. Here we show the memory effects and stimuli regulated
transport of molecules through an intelligent phase changing MoS$_2$ membrane
in response to external pH. We show that water and ion permeation through 1T'
MoS$_2$ membranes follows a pH dependent hysteresis with a permeation rate that
switches by a few orders of magnitude. We demonstrate that this phenomenon is
unique to the 1T' phase of MoS$_2$ due to the presence of surface charge and
exchangeable ions on the surface. We further demonstrate the potential
application of this phenomenon in autonomous wound infection monitoring and
pH-dependent nanofiltration. Our work significantly deepens understanding of
the mechanism of water transport at the nanoscale and opens an avenue for
developing neuromorphic applications, smart drug delivery systems,
point-of-care diagnostics, smart sensors, and intelligent filtration devices.
Van der Waals (vdW) heterostructures continue to attract intense interest as a route of designing materials with novel properties that cannot be found in naturally occurring materials. 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 material consisting of superconducting monolayers interlayered with monolayers displaying charge density waves (CDW). This bulk vdW heterostructure is created by phase transition of 1T-TaS2 to 6R at 800 {\deg}C in an inert atmosphere. Electron microscopy analysis directly shows the presence of alternating 1T and 1H monolayers within the resulting bulk 6R phase. Its superconducting transition (Tc) is found at 2.6 K, exceeding the Tc of the bulk 2H phase of TaS2. The superconducting temperature can be further increased to 3.6 K by exfoliating 6R-TaS2 and then restacking its layers. 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 surface free energy is one of the most fundamental properties of solids, hence, manipulating the surface energy and thereby the wetting properties of solids, has tremendous potential for various ...physical, chemical, biological as well as industrial processes. Typically, this is achieved by either chemical modification or by controlling the hierarchical structures of surfaces. Here we report a phenomenon whereby the wetting properties of vermiculite laminates are controlled by the hydrated cations on the surface and in the interlamellar space. We find that by exploiting this mechanism, vermiculite laminates can be tuned from superhydrophillic to hydrophobic simply by exchanging the cations; hydrophilicity decreases with increasing cation hydration free energy, except for lithium. Lithium, which has a higher hydration free energy than potassium, is found to provide a superhydrophilic surface due to its anomalous hydrated structure at the vermiculite surface. Building on these findings, we demonstrate the potential application of superhydrophilic lithium exchanged vermiculite as a thin coating layer on microfiltration membranes to resist fouling, and thus, we address a major challenge for oil-water separation technology.
Intelligent transport of molecular species across different barriers is critical for various biological functions and is achieved through the unique properties of biological membranes. An essential ...feature of intelligent transport is the ability to adapt to different external and internal conditions and also the ability to memorise the previous state. In biological systems, the most common form of such intelligence is expressed as hysteresis. Despite numerous advances made over previous decades on smart membranes, it is still a challenge for a synthetic membrane to display stable hysteretic behaviour for molecular transport. Here we show the memory effects and stimuli regulated transport of molecules through an intelligent phase changing MoS\(_2\) membrane in response to external pH. We show that water and ion permeation through 1T' MoS\(_2\) membranes follows a pH dependent hysteresis with a permeation rate that switches by a few orders of magnitude. We demonstrate that this phenomenon is unique to the 1T' phase of MoS\(_2\) due to the presence of surface charge and exchangeable ions on the surface. We further demonstrate the potential application of this phenomenon in autonomous wound infection monitoring and pH-dependent nanofiltration. Our work significantly deepens understanding of the mechanism of water transport at the nanoscale and opens an avenue for developing neuromorphic applications, smart drug delivery systems, point-of-care diagnostics, smart sensors, and intelligent filtration devices.
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 (T c) is found at 2.6 K, exceeding the T c 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.
Transition metal oxysulfides (TMOS) exhibit promising catalytic properties for hydrogen evolution reactions (HER). However, the development of facile and controllable routes for obtaining ...nanostructured TMOS under ambient conditions still remains a significant challenge. Here we report a simple and controllable route to synthesize nanoparticles of tungsten oxysulfides (WO x S y ) that exhibit enhanced electrocatalytic activity toward HER with outstanding stability. The sulfur-rich tungsten oxysulfides with engineered anionic species can offer multiple functionalities, including abundant active sites and improved conductivity that synergistically contribute to enhanced electrocatalytic activity for HER. The optimized WO x S y electrocatalyst shows low overpotential of 103 mV at a current density of 10 mA cm–2, along with a Tafel slope of 54 mV decade–1 and 5.89 × 10–2 mA cm–2 exchange current density. Density functional theory (DFT) based calculations further establish the improved catalytic activity of tungsten oxysulfide (WO x S y ), compared to the pristine 1T-WS2, based on the free energy calculations. The present work demonstrates a highly promising approach toward the development of cost-effective, efficient, and durable electrocatalysts to replace precious metals for electrocatalytic hydrogen generation.
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