Color centers are the workhorses of spin-photon networking. These are points in a crystal lattice where an atom is missing or replaced, often paired with an impurity, creating a defect that can absorb and emit single photons while storing quantum information in its spin state. The nitrogen-vacancy center in diamond is the most famous example, but engineers have been exploring a growing zoo of alternatives in silicon carbide, hexagonal boron nitride, gallium nitride, and zinc oxide. Each material-defect pairing offers different optical wavelengths, spin coherence times, and fabrication routes, and until now the field has judged these candidates almost exclusively on quantum performance. The new work adds a dimension the field has been missing: what each pathway costs in energy, chemicals, human health risk, and money.

The researchers built a multi-attribute cradle-to-gate framework, meaning they tracked impacts from raw material extraction through to the finished chip, without extending into use or disposal phases. The framework integrates four assessment types in parallel: life cycle analysis to quantify energy demand and global warming potential, chemical hazard profiling to flag dangerous process inputs, human health toxicity evaluation to capture occupational and environmental risks, and technoeconomic analysis to estimate fabrication cost per chip. Applying this combined lens to twenty host crystal and defect-generation combinations, spanning ion implantation, electron-beam irradiation, laser writing, and heteroepitaxial growth, produced a map of tradeoffs that no single metric could have revealed.

The standout result concerns hexagonal boron nitride, an ultrathin van der Waals crystal that has surged in popularity for two-dimensional quantum photonics. When defects are written into h-BN using a focused laser, the study found the lowest overall sustainability burdens of any combination tested. Laser writing into h-BN demands little energy, produces a global warming potential below twenty kilograms of carbon dioxide equivalent per chip, and carries minimal chemical hazard and toxicity profiles alongside the lowest fabrication cost. For a field racing toward mass production of quantum repeaters and single-photon sources, a pathway that is simultaneously the cheapest and the cleanest is a rare and consequential finding.

Silicon carbide emerged as the pragmatic middle ground. The material already enjoys a mature semiconductor ecosystem thanks to its role in power electronics and electric vehicles, and its color centers retain strong quantum functionality, including telecom-relevant emission and long spin coherence. The analysis shows that SiC moderates the sustainability burdens that make other platforms expensive while preserving the performance characteristics that make quantum networking viable. That balance positions silicon carbide as a credible near-term workhorse for scalable quantum hardware, particularly for teams that cannot wait for two-dimensional materials to mature into wafer-scale manufacturing.

The wide-bandgap semiconductors gallium nitride and zinc oxide showed a more fragmented picture. Neither swept the rankings, but each offered selective process-level advantages that could matter for integrated photonics, where quantum emitters must be fabricated alongside waveguides, modulators, and detectors on a single chip. The study suggests these materials may find their niche not as universal winners but as components within hybrid photonic architectures, chosen for specific fabrication steps where their environmental or economic profile beats the alternatives. This kind of granular, process-by-process accounting is exactly what the multi-attribute framework was designed to expose.

Diamond, the founding platform of color-center physics, fared worst on sustainability. The reasons are rooted in thermodynamics: growing high-purity diamond requires energy-intensive synthesis, and once defects are created, the crystal demands complex post-treatment steps to stabilize them in their useful charge states. Those stabilization requirements add further energy, chemical, and cost burdens on top of an already demanding growth process. The finding does not spell the end for diamond quantum devices, whose nitrogen-vacancy and group-IV centers remain unmatched for certain applications, but it does quantify a price that the community has never before had to confront, and it raises pointed questions about where diamond-based hardware should and should not be deployed at scale.

Beyond ranking materials, the study identifies concrete greener interventions that could bend the curves. Because the framework resolves impacts at the level of individual process steps, it points to specific levers: reducing the energy intensity of crystal growth, substituting hazardous chemical inputs, streamlining defect stabilization, and choosing defect-writing methods that minimize both power draw and waste. The authors frame these interventions as the route to scalable and resource-conscious quantum communication hardware, arguing that sustainability should be designed in from the start rather than retrofitted after networks are built. As quantum technology moves from laboratory demonstrations toward industrial manufacturing, the cumulative footprint of millions of chips will depend on decisions being made now.

The significance of the work extends past quantum networking. Defect engineering is a cornerstone of modern materials science, underpinning everything from semiconductor doping to radiation-resistant ceramics, yet environmental assessments of these techniques have been scarce. By demonstrating that a rigorous cradle-to-gate comparison across four assessment dimensions is feasible for a frontier technology, the study offers a template other subfields can adopt. It also arrives at a moment of intensifying scrutiny of the tech sector’s energy appetite, from data centers to cryptocurrency mining to artificial intelligence training, and quantum hardware is likely to face the same questions as it scales.

There are, of course, limits to what a cradle-to-gate analysis can capture. The study evaluates fabrication, not the operational lifetime energy use of quantum devices, which may include cryogenic cooling, and it does not extend to end-of-life recycling. The authors also note that their results reflect current process maturity; as laser writing of h-BN or growth of SiC wafers improves, the rankings could shift. Still, the central message stands: the quantum future has a materials bill, and for the first time the field can read it. If quantum communication is to fulfill its promise as infrastructure for the next century, the crystals at its core will need to be chosen not only for the quality of their qubits but for the weight they place on the planet. This study shows that, in at least one case, the greenest choice and the cheapest choice are the same one.

Subject of Research: Comparative sustainability assessment of defect engineering pathways for color centers in quantum communication materials

Article Title: Sustainability cost of defect engineering in color centers for quantum communications

Article References: Shata, S., & Schoenung, J. M. (2026). Sustainability cost of defect engineering in color centers for quantum communications. Nature Communications. https://doi.org/10.1038/s41467-026-78261-x

Image Credits: AI Generated

DOI: 10.1038/s41467-026-78261-x

Keywords: quantum communication, color centers, defect engineering, hexagonal boron nitride, silicon carbide, diamond, life cycle assessment, sustainability, technoeconomic analysis, single-photon sources, materials science, green manufacturing

Thermoelectric materials have long been pursued as a route to sustainable energy because they can harvest waste heat directly and turn it into useful electrical power. The efficiency of such a material is captured by a dimensionless quantity called the figure of merit, ZT, which demands a delicate balance: low thermal conductivity, high electrical conductivity, and a high Seebeck coefficient, the voltage generated per unit of temperature difference. The catch is that these three properties are interdependent, so improving one often degrades another. Nanoscale engineering, particularly through quantum confinement effects, offers a way to weaken these correlations and push performance upward.

Hexagonal boron nitride is a fascinating candidate for such engineering. Structurally it resembles graphene, with boron and nitrogen atoms arranged in a honeycomb lattice, but the two different atomic species give it fundamentally different behavior. Where graphene is a zero-band-gap semimetal, h-BN is a wide-band-gap semiconductor, and it combines exceptional chemical and thermal stability, high resistance to oxidation, and better biocompatibility and lower toxicity than carbon-based nanomaterials. Its nanomaterials are already used industrially as powders, ceramics, coatings, and chemical vapor deposition layers, yet its thermoelectric properties at the nanoscale remain far less explored than those of graphene.

Nanoscrolls themselves have an intriguing history. Scroll structures were first proposed by Bacon in 1960, confirmed decades later once imaging techniques caught up, and successfully synthesized in 2003 through a chemical route to carbon nanoscrolls. Unlike nanotubes, which form closed cylinders, nanoscrolls retain an open-ended morphology, sharing some properties with multi-walled nanotubes but differing in ways that matter for electron transport. Depending on which crystallographic direction is chosen as the rolling axis, zigzag, armchair, or chiral scrolls can be produced, and the geometry is described by a polar equation in which the radial distance grows with the rolling angle and the interlayer spacing.

The research team modeled five zigzag h-BN nanoscrolls, labeled (15,0) through (19,0), across a temperature range of 200 to 700 kelvin. They employed a nearest-neighbor tight-binding method to calculate the electronic band structure, adapting the framework originally developed for graphene. Because h-BN contains two distinct atoms, the onsite energies at nitrogen and boron sites differ, opening a band gap where graphene has none. The open geometry of the scroll required a further modification: instead of the strict periodic boundary condition that applies to nanotubes, the researchers introduced a phase shift into the circumferential boundary condition, treating these phase shifts as effective parameters adopted from prior graphene nanoscroll work rather than independently optimized values for h-BN.

The band structure calculations revealed something striking: all five scroll chiralities are wide-band-gap semiconductors with nearly identical gaps of roughly 4.74 electron volts, regardless of how tightly or loosely they are rolled. Changing the chirality does not significantly influence the band gap; it only alters the number and energy of the sub-bands that emerge from the rolled geometry. This curvature independence echoes earlier findings for boron nitride nanotubes, suggesting that for h-BN nanostructures, helicity in the atomic arrangement has a negligible effect on the fundamental gap.

Where chirality does matter is in the fine structure of electron transport. Using the Landauer-Büttiker formalism, the team calculated the transmission function, which counts the conducting channels available at each energy. At around 2.37 electron volts, transmission jumps from zero to two channels for chiralities where the index n is a multiple of three, but only from zero to one for the others. These differences cascade through the thermoelectric parameters. Electrical conductance, which depends on the overlap between the transmission function and the thermal broadening of the Fermi-Dirac distribution, rises first and fastest for the (19,0) scroll, whose transmission increases in larger, more uniform steps, while the (16,0) scroll, despite having the smallest band gap, lags because its second channel opens only at higher energies.

The Seebeck coefficient, by contrast, showed only negligible differences among chiralities at room temperature, reflecting the similar asymmetry of the transmission functions around the Fermi level. To compare the materials fairly, the team evaluated all parameters at reference Fermi energies where the power factor peaks, near 2.35 electron volts. Raising the temperature from 200 to 700 kelvin increased electrical conductance by a factor of roughly 2.1 to 2.6, as the broadening function expanded to admit higher-energy sub-bands into conduction, while the Seebeck coefficient declined slightly, by about 3 to 10 percent, for most chiralities. The (17,0) and (18,0) scrolls bucked this trend above 600 kelvin, where the growing asymmetry contribution to the Seebeck numerator slightly outweighed the rising conductance in the denominator.

The headline result concerns the electronic figure of merit. Although the (19,0) scroll delivers the highest power factor across the entire temperature range, it is the (15,0) scroll that achieves the highest ZT at lower temperatures, reaching 4.22 at 200 kelvin and 3.4 at 300 kelvin, before falling to 2.07 at 700 kelvin, the lowest value in the study. The (19,0) and (16,0) scrolls proved the most temperature-stable, with their figures of merit holding nearly constant at about 2.5 above 400 and 500 kelvin respectively. The overall decline of ZT with temperature stems from electron thermal conductance climbing 8.5 to 13.5 times faster than the power-generating term in the figure of merit, a consequence of the Wiedemann-Franz-like coupling between electrical and electronic thermal conductance.

The authors are careful to frame these numbers as ideal upper limits. The calculations describe defect-free scrolls under purely ballistic transport, with no accounting for electron-phonon scattering, structural disorder, or finite device length, all of which become increasingly important at elevated temperatures. The tight-binding model was also not calibrated against first-principles calculations for these specific geometries, so the trends, not the absolute values, carry the most weight. Even so, the study opens a genuinely new window: it is the first extensive look at how the rolling geometry of boron nitride nanoscrolls shapes thermoelectric behavior, and it suggests that choosing the right chirality could one day help engineers tune these biocompatible, thermally robust spirals into working components of waste-heat recovery devices.

Subject of Research: Chirality-dependent ballistic thermoelectric properties of zigzag hexagonal boron nitride nanoscrolls

Article Title: Comparative investigation of chirality-dependent thermoelectric performance in hexagonal boron nitride nanoscrolls under ballistic transport regime

Article References: Samadpour, E., Dideban, D., & Karamitaheri, H. (2026). Comparative investigation of chirality-dependent thermoelectric performance in hexagonal boron nitride nanoscrolls under ballistic transport regime. Results in Physics, Article 108768. https://doi.org/10.1016/j.rinp.2026.108768

Image Credits: AI Generated

DOI: 10.1016/j.rinp.2026.108768

Keywords: hexagonal boron nitride, nanoscrolls, thermoelectrics, chirality, ballistic transport, figure of merit, tight-binding model, Landauer-Büttiker formalism, Seebeck coefficient, band structure, waste heat recovery, nanomaterials

The study, published in the journal Advanced Composites and Hybrid Materials, describes a porous composite membrane made from hexagonal boron nitride (hBN) nanoplatelets embedded in polydimethylsiloxane (PDMS), the soft silicone elastomer that dominates skin-wearable design. The key innovation lies in how the pores are created. Instead of templating, washing, solvent extraction, or any post-fabrication treatment, the researchers mixed a volatile liquid, perfluorohexane (PFH), directly into the hBN/PDMS formulation. As the membrane was cast and cured, the PFH evaporated on its own, leaving behind a stable network of air voids. The porous architecture emerges during curing itself, which means the process can in principle run as a continuous, one-step casting operation without extra processing stages that add cost and complexity.

What makes the approach more than a convenience is the degree of control it offers. The team found that pore size could be tuned simply by changing the curing temperature, because temperature governs a kinetic race between two competing processes: the solidification of the PDMS matrix and the volatilization of the PFH porogen. When curing outpaces evaporation, the growing polymer locks in a particular pore morphology; when evaporation dominates, the voids evolve differently. By adjusting this balance, the researchers could dial in the porous structure without changing the chemistry of the formulation. Meanwhile, the overall porosity of the membrane rose from roughly 15 percent to about 31 percent as the PFH content in the mixture increased, giving a second, independent handle on the material’s internal architecture.

The central surprise of the work is thermal. Porosity normally kills thermal conductivity, since air-filled voids interrupt the paths along which heat travels. Yet the porous hBN/PDMS membrane achieved a thermal conductivity of 0.22 watts per meter-kelvin, essentially matching the dense form of the same composite. The explanation lies in how the hBN nanoplatelets arrange themselves during fabrication. Rather than being distributed randomly through the bulk, the platelets assemble along the walls of the pores, forming continuous heat-conduction pathways that thread through the material. Heat entering the membrane finds an interconnected skeleton of thermally conductive boron nitride to follow, even as the voids between those pathways remain open for water vapor transport. Breathability and heat dissipation, usually opposing goals, are satisfied simultaneously by the same microstructure.

To understand this behavior in more detail, the researchers turned to computational fluid dynamics simulations. The modeling showed that heat is transferred more effectively near the interface between the hBN and the PDMS matrix in the porous membrane than in comparable dense structures. That computational picture matched what the team observed experimentally: the porous membrane accumulated less heat during use. In a skin-interface application, lower heat accumulation translates directly into less thermal stress on the tissue beneath, which matters both for user comfort and for the accuracy of sensors that measure physiological signals through the skin.

Thermal performance alone would not make a material suitable for wear. The team therefore evaluated the membrane in contact with living skin. In vivo analysis showed that the porous membrane kept skin hydration at a stable level of approximately 103 to 107 percent over the testing period, indicating that the material does not trap moisture against the skin or dry it out. Hydration stability is a meaningful benchmark for wearables, because occlusive films that block vapor transport cause the skin to macerate over time, degrading both comfort and measurement quality. A membrane that holds hydration in a narrow, healthy band addresses one of the most common complaints about long-duration skin patches.

Mechanical compliance proved equally convincing. The porous membrane’s mechanical behavior was found to be close to that of bare skin, meaning the material deforms in a way that the body does not register as a stiff foreign object. This is where the choice of PDMS as the matrix pays off: the elastomer is soft, stretchable, and biocompatible, and introducing controlled porosity pushes its effective stiffness even lower. Combined with the hydration results, the mechanical data suggest that the membrane satisfies both the physiological and mechanical criteria for comfortable, extended skin contact, which the authors describe as the foundation for future skin-interface applications.

The significance of the work extends beyond a single material recipe. Hexagonal boron nitride is prized in electronics for its thermal conductivity, electrical insulation, and chemical stability, and pairing it with PDMS is a natural strategy for thermally managed wearables. What has been missing is a fabrication route that preserves those thermal benefits while adding breathability without extra processing. By using a volatile porogen that does its job and disappears during curing, the researchers have effectively turned the manufacturing step itself into the design tool. The pore structure, the porosity, and the platelet alignment all emerge from the interplay of curing kinetics and evaporation, parameters that are easy to adjust on a production line.

The study was a collaboration between the Research and Innovation Center of Amorepacific Corporation in Yongin and the School of Mechanical Engineering at Soongsil University in Seoul, combining industrial materials expertise with mechanical engineering analysis. The work was supported by South Korea’s National Research Foundation through its Bio and Medical Technology Development Program and the G-LAMP Program, as well as by the Ministry of Trade, Industry and Energy through an Industrial Technology Innovation Program grant. The involvement of a major cosmetics and personal care company hints at near-term applications in skin patches, cosmetic films, and health-monitoring wearables, where thermal comfort and moisture management directly affect product performance.

For the wearable industry, the message is that the long-standing trade-off between breathability and thermal management may be an artifact of how porous materials have been made, not a law of physics. If thermally conductive fillers can be guided to line the pore walls of a soft elastomer, air voids no longer have to be thermal dead ends. The one-step PFH porogen method offers a scalable route to that architecture, with tunable pores, no washing or extraction stages, and demonstrated comfort on living skin. As skin-interfaced sensors, electronic skins, and on-body therapeutic devices multiply, materials like this porous hBN/PDMS membrane could determine whether the next generation of wearables is something people actually forget they are wearing.

Subject of Research: One-step fabrication of porous hexagonal boron nitride/PDMS composite membranes for breathable, thermally dissipative skin-interface wearable applications

Article Title: One-step fabrication of a porous hBN/PDMS composite membrane for breathable and thermally dissipative skin-interface applications

Article References: Lee, J. Y., Lee, S. K., Nam, J., & Hong, J. (2026). One-step fabrication of a porous hBN/PDMS composite membrane for breathable and thermally dissipative skin-interface applications. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02120-y

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02120-y

Keywords: hexagonal boron nitride, PDMS, porous membrane, thermal management, breathability, wearable electronics, skin-interface materials, perfluorohexane porogen, thermal conductivity, skin hydration, mechanical compliance, computational fluid dynamics

Hyperbolic phonon polaritons, often abbreviated HPhPs, are among the most remarkable optical excitations known to materials science. They arise when infrared electromagnetic fields couple strongly to the natural lattice vibrations, or optical phonons, of certain crystals. The resulting hybrid waves behave in ways that ordinary light cannot: they can squeeze electromagnetic energy into volumes thousands of times smaller than the wavelength of the light itself, guiding it coherently along a material’s surface or through its bulk. This extreme confinement makes them attractive candidates for nanoscale light manipulation, high-sensitivity molecular spectroscopy, and the miniaturization of optical circuits to dimensions that rival modern microelectronics.

Hexagonal boron nitride, or hBN, a layered van der Waals crystal famous for its role as a protective encapsulant in two-dimensional electronics, is a particularly powerful host for these waves. Within specific infrared frequency bands, hBN behaves as a hyperbolic medium, meaning that its dielectric response is positive along one crystal axis and negative along another. In this regime, the polariton wavefronts take on hyperbolic shapes, and the waves can propagate with wavelengths dramatically shorter than free-space light, carrying electromagnetic energy along the crystal with remarkable confinement. But harnessing such waves in practical devices requires more than passive propagation; engineers need the ability to switch, steer, and reshape them on demand, and to do so at speeds fast enough to matter for information processing.

That is precisely where the experimental challenge has always lain. Hyperbolic phonon polaritons are strongly dispersive, which means their wavelength changes substantially depending on the frequency of the light that excites them. Femtosecond laser pulses, the only tools capable of resolving dynamics on the relevant timescales, are inherently broadband: a single pulse contains a wide spread of frequencies. When such a pulse strikes a sample, it excites polaritons of many different wavelengths simultaneously. In a real-space image, the interference fringes produced by all these waves overlap and average together, washing out the very propagation patterns scientists want to see. The obvious remedy, narrowing the spectrum of the pulse before it reaches the sample, comes at a cruel price: by the fundamental rules of Fourier optics, a narrower spectrum demands a longer pulse, which destroys the femtosecond time resolution that motivated the experiment in the first place.

A research team led by Kazuki Kamada of the Institute for Molecular Science (IMS) and Osaka Metropolitan University, together with Jun Nishida, Assistant Professor at IMS, and Takashi Kumagai, Associate Professor at IMS, has now found an elegant way around this trade-off. Their solution was to leave the excitation pulse untouched and instead perform the frequency selection after the fact, during detection. By inserting a diffraction grating into the detection path of an ultrafast infrared near-field optical microscope, the team spectrally separated the broadband infrared light scattered from the sharp metallic tip of an atomic force microscope before it reached the detector. Because each frequency component could then be imaged independently, the overlapping interference patterns were cleanly disentangled without ever lengthening the excitation pulse.

The resulting instrument is a genuine tour de force of measurement engineering. It combines nanoscale spatial resolution, inherited from the near-field interaction between the microscope tip and the sample, with a temporal resolution of approximately 150 femtoseconds and a spectral resolution of roughly 10 inverse centimeters. In practical terms, the technique allows researchers to select a single narrow slice of the infrared spectrum, watch the polariton associated with that frequency propagate across the sample in a snapshot lasting only a few hundred atomic vibrations of time, and then repeat the measurement at successive pump-probe delays to assemble a full movie of the wave’s evolution. No previous near-field imaging scheme had brought all three of these capabilities together for strongly dispersive polaritons.

With the new microscope in hand, the team turned it on van der Waals heterostructures composed of tungsten disulfide (WS2) and hexagonal boron nitride. The experimental geometry was a classic pump-probe arrangement: a pulse of visible light generated photoexcited charge carriers, mobile electrons and holes, within the WS2 layer, while a time-delayed infrared near-field pulse probed how those carriers affected the hyperbolic phonon polaritons propagating in the adjacent hBN. Because the two atomically thin materials lie in intimate contact across the van der Waals interface, any change in the optical properties of one should, in principle, be felt by the waves traveling in the other. The question was whether the effect would be fast enough and strong enough to see directly.

The answer was a clear yes, and the details proved richer than a simple on-off switching picture. In heterostructures containing a thin WS2 layer, the researchers observed a transient modulation dominated by a change in the electric-field amplitude of the polaritons, as if the photoexcited carriers were momentarily absorbing or damping the wave. More strikingly, in structures containing a relatively thick WS2 layer, the team resolved a change in the polariton’s wavelength itself. This is a qualitatively different and more powerful form of control: it demonstrates that optical excitation can modify not merely how strongly the wave is present but how it propagates, effectively rewriting the dispersion relation of the polariton on the fly. Electromagnetic simulations confirmed that both observations could be explained by a transient, carrier-induced change in the dielectric response of WS2, which then modifies the HPhPs propagating in the neighboring hBN through the shared interface.

The physical mechanism is worth appreciating in detail. When visible light excites electron-hole pairs in WS2, the free carriers alter the material’s dielectric function, particularly at infrared frequencies relevant to the hBN polaritons. Since the hyperbolic phonon polariton is a hybrid mode whose electromagnetic field extends across both layers of the heterostructure, this sudden change in the WS2 dielectric environment is imprinted directly onto the wave. The carriers then relax and recombine on their own timescale, and the polariton returns to its unperturbed state. The entire cycle, from optical switching to recovery, unfolds within a few hundred femtoseconds, which is exactly the regime the new imaging technique was designed to capture. In effect, the researchers have demonstrated an all-optical gate for nanoscale light, in which one beam of light controls another through the mediation of photoexcited carriers and a van der Waals interface.

The implications extend well beyond this particular material system. The study, published online in Nano Letters on July 27, 2026, establishes a general platform for observing and controlling nanoscale light propagation on femtosecond timescales, and the same imaging strategy should apply to other strongly dispersive polaritons, including surface plasmon polaritons in metals and phonon polaritons in other hyperbolic crystals. As the authors note, the results open new opportunities for ultrafast nanophotonics, a field in which devices might one day modulate, route, and process signals encoded in confined light fields at speeds approaching the fundamental limits set by the optical oscillations themselves. The work was supported by JSPS KAKENHI, the JST FOREST and CREST programs, the MEXT World Premier International Research Center Initiative, and several other Japanese research foundations, and it involved collaborators from the National Institute for Materials Science, the Fritz Haber Institute in Berlin, and Osaka Metropolitan University. For now, the immediate contribution is conceptual and methodological: a way to see, frame by femtosecond frame, how light confined to the nanoscale can be commanded to change its shape, its speed, and its very wavelength, all at the whim of a flash of visible light.

Subject of Research: Ultrafast nano-imaging and optical control of hyperbolic phonon polaritons in van der Waals heterostructures

Article Title: Capturing fleeting changes in “nanoscale light”—femtosecond nano-imaging reveals ultrafast optical control of phonon polariton

Article References: Capturing fleeting changes in “nanoscale light”—femtosecond nano-imaging reveals ultrafast optical control of phonon polariton. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: phonon polaritons, hexagonal boron nitride, tungsten disulfide, femtosecond imaging, near-field microscopy, nanophotonics, van der Waals heterostructures, ultrafast optics, pump-probe spectroscopy, dielectric response, Nano Letters, light-matter coupling

The physics behind the problem is unforgiving. Overhead conductors, typically aluminum conductor steel-reinforced (ACSR) cables, are limited by the balance between internal resistive Joule heating and passive heat dissipation to the environment. This balance defines the cable’s ampacity, the maximum current it can carry without exceeding its maximum allowable operating temperature, which is usually around 75 degrees Celsius for ACSR conductors. In hot urban climates where air temperatures can surpass 50 degrees Celsius, the thermal gradient between conductor and atmosphere collapses, degrading both convective and radiative cooling precisely when air-conditioning demand peaks. The consequences cascade: every 10-degree increase in conductor temperature raises the electrical resistance of aluminum and its associated Joule losses by roughly 4 percent, while heat accelerates mechanical sag, reduces ground clearance, and promotes annealing that weakens the metal. Recent outage data from China show that heatwaves increase outage frequency by nearly 4 percent and outage duration by about 8 percent, with heatwave-induced outages estimated to cost approximately 3.4 billion US dollars in the analyzed scenario.

Existing mitigation strategies fall short. Dynamic line rating systems squeeze more capacity from existing thermal margins but do nothing to lower conductor temperature itself. High-temperature low-sag conductors tolerate hotter operation but demand extensive and costly retrofitting of transmission infrastructure. Meanwhile, conventional surfaces are optically and thermally suboptimal: aged bare aluminum reflects sunlight only modestly and emits infrared radiation poorly, while common polymeric insulators such as cross-linked polyethylene absorb substantial solar radiation and conduct heat at a sluggish 0.3 watts per meter-kelvin, effectively trapping internally generated heat. The KAUST team recognized that the ideal cable surface must do three things at once: reflect sunlight, radiate heat efficiently in the mid-infrared, and conduct Joule heat from the core to the surface.

That third requirement is what sets this work apart from a decade of radiative cooling research. Most radiative cooling coatings, developed for buildings and textiles, deliberately have low thermal conductivity to block heat from entering. For a cable, which generates its own heat, that strategy is exactly backwards. The researchers inverted another classical concept as well: the critical insulation radius. In pipeline engineering, adding insulation to a cylinder initially increases heat loss by enlarging the surface area, until a critical thickness is reached beyond which insulation suppresses heat transfer. For overhead cables, the team repurposed this counterintuitive principle to maximize heat rejection. Their thermal resistance network model showed that for a coating with conductivity near 1 watt per meter-kelvin on a 10-millimeter-radius cable, total thermal resistance reaches a minimum at a critical thickness of 2.8 millimeters, about 3 percent lower than that of the uncoated conductor. Beyond that thickness, the added conduction path dominates and cooling efficiency declines, so optimal thickness must be tuned to cable radius, wind conditions, and existing insulation.

The material itself is elegantly engineered. Hexagonal boron nitride was chosen because it uniquely combines strong optical scattering, high dielectric contrast, and an intrinsic thermal conductivity exceeding 400 watts per meter-kelvin. A Lorenz-Mie scattering model revealed that solar backscattering is maximized for h-BN particle diameters of 300 to 500 nanometers, coinciding with the peak energy of the solar spectrum, and Monte Carlo ray tracing confirmed the prediction. Reflectance rises with particle loading up to about 10 percent by volume and saturates near 0.91 for coating thicknesses between 0.2 and 2 millimeters. In the final composite, loaded at 40 percent h-BN, the thermal conductivity of the PDMS film jumped from 0.18 to 1.28 watts per meter-kelvin, with cross-sectional electron microscopy revealing a percolated network of platelets that creates efficient phonon transport pathways. Optically, the coating achieves a solar reflectance of 0.92, extending into the ultraviolet for photostability, and a mid-infrared emissivity of 0.95, driven by the vibrational modes of the polymer matrix. Angular-resolved measurements confirmed that reflectance barely depends on incidence angle, essential for a cylindrical cable illuminated by a moving sun.

Durability testing addressed the harsh realities of outdoor service. The pristine coating’s tensile strength of 2.5 megapascals falls short of the 21 megapascals of cross-linked polyethylene, but sandwiching a thin, porous 0.13-millimeter Nylon layer into the film raised tensile strength to roughly 45 megapascals, more than double that of XLPE, while preserving a conductivity of about 1.2 watts per meter-kelvin because the polymer infiltrates the Nylon’s pores. The surface is hydrophobic, with a contact angle of 115.3 degrees, so dust washes off and the coating regains its original white appearance. After 1000 cycles of standardized sandpaper abrasion simulating windblown sand, its optical properties were essentially unchanged. Following 240 hours of accelerated ultraviolet aging, reflectance and emissivity held steady, aided by roughly 95 percent UV reflectance at 340 nanometers. The coating also resisted salt spray and, critically for wildfire-prone regions, did not ignite or deform under direct flame exposure.

Field validation came from outdoor experiments in Thuwal, Saudi Arabia, conducted at KAUST. Over three days of continuous exposure in July 2025, with peak midday solar irradiance near 1100 watts per square meter, the HTCRC-coated cable consistently remained the coolest of three suspended cables, about 5 degrees cooler than bare ACSR and 15 degrees cooler than a commercial insulated cable. To capture the effect of internal heat generation, the team built simulated cables containing resistive wires that mimic Joule heating. Over a seven-day measurement in August 2025, with ambient temperatures reaching 45 degrees Celsius, both the insulated and bare cables exceeded the 75-degree safety threshold, peaking near 80 and 90 degrees respectively, while the coated cable cycled between 50 and 70 degrees, staying about 5 degrees below the limit even at midday. At night, the coated and insulated cables tracked each other closely because both emit infrared strongly, whereas bare aluminum, with an emissivity of only about 0.1, stayed hotter.

Cooler cables also sag less. Using the catenary equation, the standard analytical tool for suspended transmission lines, the team projected sag growth over 10 and 20 years of service and found the coated cable exhibited markedly smaller increases, indicating enhanced long-term dimensional stability and reduced risks of mechanical failure, short circuits, and outages. The thermal margin translates directly into capacity. Applying the CIGRE Technical Brochure 601 heat balance model to an ACSR 450 AlFe 8 conductor, the coated cable achieved a calculated ampacity of 830 amperes, far exceeding the 630 amperes of a black insulated cable and the 710 amperes of a bare silver cable. Under dynamic diurnal conditions with a 40-degree peak ambient temperature and 1000 watts per square meter of irradiance, the coated cable delivered up to 165 amperes more than the insulated cable at solar noon, when conventional conductors hit their thermal bottleneck.

Scaled to real climates, the numbers become strategically significant. A year-long simulation for Riyadh, where summer temperatures frequently exceed 45 degrees Celsius, showed an average daytime ampacity increase of about 10 percent, peaking at 18.3 percent in July. Across 13 representative hot-climate cities worldwide, the projected annual daytime ampacity gain ranges from 6 to 10 percent. Because the coating’s density of about 1.2 grams per cubic centimeter sits within the range of commercial cable insulation materials, retrofitting adds no meaningful weight or tensile load, and the design remains compatible with IEC 60502 insulation standards. The broader implication is a way to break the vicious feedback loop in which rising temperatures degrade transmission capacity exactly when cooling-driven demand peaks. By passively unlocking latent capacity in existing infrastructure, this photonic coating offers cities a scalable, low-cost path to climate resilience at a moment when electrification and the energy appetite of artificial intelligence are pushing grids toward their thermal limits.

Subject of Research: High-thermal-conductivity radiative cooling coatings for overhead power transmission cables

Article Title: Photonic thermal management of overhead cables via high-thermal-conductivity radiative cooling

Article References: Xu, K., Cao, P.-F., El-Demellawi, J. K., Qasem, H., & Gan, Q. (2026). Photonic thermal management of overhead cables via high-thermal-conductivity radiative cooling. Light: Science & Applications, 15(1), Article 385. https://doi.org/10.1038/s41377-026-02485-1

Image Credits: AI Generated

DOI: 10.1038/s41377-026-02485-1

Keywords: radiative cooling, power cables, hexagonal boron nitride, PDMS, ampacity, thermal management, photonic coatings, grid resilience, heatwaves, solar reflectance, mid-infrared emissivity, CIGRE 601

The device itself is deceptively simple in architecture. It consists of a vertical stack of silver, hexagonal boron nitride, and indium tin oxide, all deposited on a flexible polyethylene terephthalate substrate. Hexagonal boron nitride, often nicknamed white graphene, is a layered insulating crystal whose atomically flat sheets can be stacked like a deck of cards. In a conventional memristor, electrical pulses program the resistance state, and mechanical deformation is usually treated as a nuisance, a source of noise or failure to be engineered away. The Shiv Nadar team inverted that logic. In their device, bending is the programming signal. When the flexible substrate flexes, the hBN flakes within the stack slide laterally relative to one another, and that sliding perturbs the stacking arrangement and the inter-flake tunneling distance that governs how easily electrons can hop across the layered insulator.

The elegance of the mechanism lies in what does not happen. Because the programming arises from interlayer sliding rather than from stretching the crystal lattice itself, the hBN sheets are never strained at the atomic level. The covalent bonds within each flake remain intact, which means the process is non-destructive and, crucially, reversible. Straighten the device and the flakes can slide back, restoring the previous tunneling gap and the previous conductance state. This stands in sharp contrast to many flexible memristor designs, where repeated mechanical cycling gradually degrades the active material through crack formation, atomic displacement, or electromigration. Here, deformation is not damage; it is information. The researchers describe this as a mechanoelectronic design principle, one in which the physical interaction between device and environment becomes the write mechanism for synaptic plasticity.

What makes the comparison to the neuromuscular junction more than a metaphor is the way the device responds to bending. Biological mechanosensitive neurons transduce deformation into graded changes in synaptic strength, with both the amplitude and the dynamics of the response modulated by the magnitude and history of the mechanical stimulus. The hBN memristor reproduces this co-modulation quantitatively. Different bending conditions produce different families of conductance states, and the temporal evolution of those states mirrors the amplitude and dynamics seen in their biological counterparts. In other words, the device does not simply switch between on and off; it exhibits the continuous, history-dependent plasticity that neuroscientists associate with real synapses, where the same stimulus can produce different outcomes depending on what came before.

To demonstrate that these mechanically programmed states are more than a laboratory curiosity, the team put the device to work as an artificial synapse in a computational brain. The conductance values measured under varying bending conditions were used as analog synaptic weights in a fully connected neural network, the workhorse architecture of modern machine learning. The network was trained on MNIST, the classic benchmark of handwritten digit recognition that has served for decades as a proving ground for neuromorphic hardware. Across all bending conditions tested, the network achieved classification accuracy exceeding 91 percent. That figure matters because it shows that the mechanically induced conductance states are not random or noisy; they are stable, distinguishable, and useful as computational elements. A synapse that changes when you bend it, yet still supports high-accuracy inference, is a synapse that could live inside a prosthetic hand or a soft robot.

The implications for flexible and wearable neuromorphics are considerable. Current approaches to tactile sensing in soft electronics typically separate the sensing element from the computing element: a pressure sensor converts touch into an electrical signal, which is then routed to a processor that decides what it means. That separation costs power, latency, and wiring complexity, all of which are precious commodities in a wearable device. A memristor that programs itself through touch collapses that boundary. The sensing and the memory update are the same physical event, happening at the same place at the same time. For applications such as electronic skin, adaptive prosthetics, or soft robotic grippers that must learn from contact, this kind of co-located mechanosensation and plasticity could dramatically simplify the hardware stack.

The choice of materials is also strategically significant. Hexagonal boron nitride is chemically robust, thermally stable, and widely studied as a protective encapsulant and tunneling barrier in two-dimensional electronics. Its layered structure, with weak van der Waals forces between sheets and strong covalent bonds within them, is precisely what enables the sliding mechanism at the heart of the device. The silver and indium tin oxide electrodes provide the vertical conduction path, and the PET substrate supplies the flexibility that makes the whole concept possible. Because the active mechanism does not rely on electrochemical filament formation or oxygen vacancy migration, the usual culprits behind memristor variability and endurance limits, the device sidesteps several long-standing reliability problems in the field.

There are, of course, hurdles between a promising laboratory demonstration and a deployable technology. The reported work establishes the principle and the benchmark performance, but scaling from individual devices to the dense crossbar arrays needed for practical neuromorphic systems will require careful control of device-to-device uniformity, particularly for a mechanism that depends on the precise stacking of exfoliated or grown two-dimensional flakes. Integration with conventional readout circuitry, long-term cycling stability under millions of bending events, and compatibility with large-area manufacturing are all questions that the field will now press forward. The authors acknowledge support from the Science and Engineering Research Board and the Department of Science and Technology in India, reflecting the growing investment in flexible neuromorphic platforms worldwide.

Still, the conceptual shift is hard to overstate. For half a century, computing has treated memory and processing as separate functions and mechanical deformation as an enemy of reliability. This work suggests a future in which the shape of a device is part of its computational state, in which a bend is a bit, and in which soft machines learn the way our muscles do, through the very act of moving. The neuromuscular junction has been quietly optimizing that trick for hundreds of millions of years. With a few atomic layers of boron nitride and a flexible plastic backing, engineers have finally started to take notes.

Subject of Research: Mechanosensitive hexagonal boron nitride memristors for flexible neuromorphic computing

Article Title: Neuromuscular Junction Inspired Mechanosensitive hBN-based Memristors for Flexible Neuromorphics

Article References: Parida, T., Swain, S. K., Sengupta, D., & Kanjilal, A. (2026). Neuromuscular Junction Inspired Mechanosensitive hBN-based Memristors for Flexible Neuromorphics. npj Flexible Electronics. https://doi.org/10.1038/s41528-026-00647-0

Image Credits: AI Generated

DOI: 10.1038/s41528-026-00647-0

Keywords: memristor, hexagonal boron nitride, neuromorphic computing, flexible electronics, neuromuscular junction, synaptic plasticity, mechanosensitive, interlayer sliding, MNIST, wearable devices, two-dimensional materials, artificial synapse

The principle behind the sensor is elegantly simple, even if the engineering behind it is not. Hexagonal boron nitride, a layered crystal often described as a wide-band-gap insulator, hosts point defects that emit light when excited by a laser. These emitters behave much like the nitrogen-vacancy centers in diamond that have become workhorses of quantum sensing, but they live in a material that is only a few atoms thick. When an ion in the surrounding liquid approaches or binds near one of these defects, the local electrostatic environment changes, and the energy levels of the defect shift accordingly. That shift appears as a change in the wavelength of the emitted fluorescence, which the researchers can read out with a spectrally resolved optical imaging system.

To prove the concept, the team used lithium ions in organic electrolytes as their model system, a choice motivated by the central role that lithium-ion dynamics play in rechargeable batteries. When lithium ions were added to the electrolyte surrounding an h-BN flake, individual defects responded with spectral shifts exceeding 10 nanometers, a remarkably large change for a single-ion event. The magnitude of the shift matters enormously for practical sensing: a signal of 10 nanometers is far above the noise floor of a well-calibrated optical system, which means individual ion arrivals can be distinguished unambiguously rather than inferred statistically from ensemble averages.

The researchers then discovered that they could amplify the effect dramatically. By applying an external electric field across the liquid cell, they increased the observed spectral shifts to more than 40 nanometers. This enhancement arises because the field perturbs the local ion distribution near the defect, effectively modulating the electrostatic landscape that the emitter experiences. With such large shifts, the platform becomes capable of real-time monitoring of local ion perturbations, meaning the researchers could follow ions as they arrived, departed, or reorganized around individual defects on the h-BN surface. The temporal resolution of the measurement reaches the millisecond scale, fast enough to capture many of the dynamic processes relevant to electrochemistry.

Perhaps the most striking capability demonstrated in the study is chemical discrimination. Individual defects did not merely register the presence of ions; they distinguished between different ion species. Sodium, magnesium, and aluminum ions each produced characteristic spectral signatures, allowing the researchers to identify which ion was interacting with a given defect. This selectivity emerges from differences in charge, ionic radius, and hydration chemistry among the species, each of which leaves a distinct fingerprint on the defect’s emission spectrum. In experiments spanning lithium, sodium, potassium, and cesium ions in aqueous solutions, the distributions of spectral peak positions differed measurably between ion types, suggesting a general route to ion-specific sensing without the ion-selective membranes that conventional electrochemical sensors require.

The sensitivity of the platform is equally noteworthy. The researchers report detection at concentrations down to the 10 micromolar range, which corresponds to roughly ten billion ions per liter. While that sounds like an enormous number, it represents a dilute regime in which individual binding and unbinding events at the defect surface can be resolved rather than swamped by the ambient population. Combined with the millisecond temporal resolution, this sensitivity places the technique in a regime where it can probe the stochastic, single-molecule dynamics that govern interfacial chemistry, rather than the smooth averages that bulk techniques report.

The experimental apparatus itself reflects careful engineering. The team built microfluidic cells, some equipped with electrodes for electrical testing, that hold the h-BN flakes in contact with electrolytes while an optical system images the fluorescent emission. Wavelength calibration was performed using a calcium fluoride prism and regression models that correlate pixel positions with wavelengths across the field of view, achieving a resolution of roughly 1 to 4 nanometers depending on the spectral region. Drift correction using calibration nanoparticles kept positional uncertainty below one pixel over thousand-frame recordings. Statistical analysis of emitter counts followed Poisson distributions, confirming that the observed signals arose from well-defined, individually addressable defects rather than collective artifacts.

The implications for battery research are immediate. Understanding how lithium ions move, accumulate, and react at electrode-electrolyte interfaces is one of the central unsolved problems in energy storage, and it dictates phenomena from charging speed to degradation and dendrite formation. Existing tools, from cryogenic electron microscopy to synchrotron X-ray methods and Raman spectroscopy, either require freezing the sample, average over large areas, or lack the sensitivity to see single ions. A sensor that sits directly in the liquid environment and reports on individual ion arrivals at a specific surface site offers a fundamentally new vantage point. The same logic extends to environmental chemistry, where detecting trace metal ions in water is a persistent analytical challenge, and to the broader study of interfacial electrochemistry, catalysis, and ion transport through nanoscale channels.

The work also builds on a rapidly maturing body of research into quantum emitters in two-dimensional materials. Since single-photon emission from h-BN was first reported in monolayers, researchers have catalogued defect types, developed plasma-based creation methods, and demonstrated room-temperature spin defects usable as qubits. Recent studies have already used h-BN sensors to detect paramagnetic spins in liquids and to observe water-mediated proton transport at surface defects. The new result extends this quantum-sensing toolkit from spins and protons to the full range of dissolved ions, leveraging the extreme surface sensitivity that only an atomically thin host can provide. Because the defects sit at or near the surface, ions in the adjacent liquid interact with them directly, without the screening and distance penalties that plague buried sensors in bulk crystals.

There are, of course, questions that future work must address. The precise atomic structure of the optically active defects remains an active area of investigation, and theoretical computations performed by the team, in collaboration with the SUNCAT Center for Interface Science and Catalysis at SLAC, point toward defect-mediated interactions that will need further first-principles characterization. Long-term stability of the emitters in aggressive electrochemical environments, calibration across different solvent systems, and the development of arrays of addressable defects for spatially resolved ion mapping are all natural next steps. But the core demonstration stands: a fluorescent defect in a two-dimensional crystal can register the arrival of a single ion in a liquid, tell you what kind of ion it is, and do so in milliseconds. For a field that has spent half a century averaging away the very events that matter most, that is a transformative capability, and one that is likely to spread quickly from battery labs to wherever single ions write the story of chemistry at interfaces.

Subject of Research: Single-ion detection in liquids using fluorescent defects in hexagonal boron nitride

Article Title: Single-ion sensing in liquid using fluorescent hexagonal boron nitride defects

Article References: Wu, Y., Xu, K., Sarker, H. P., Taniguchi, T., Watanabe, K., Abild-Pedersen, F., Majumdar, A., Cui, Y., Tzeng, Y.-K., & Chu, S. (2026). Single-ion sensing in liquid using fluorescent hexagonal boron nitride defects. Nature Sensors. https://doi.org/10.1038/s44460-026-00150-z

Image Credits: AI Generated

DOI: 10.1038/s44460-026-00150-z

Keywords: hexagonal boron nitride, quantum defects, single-ion sensing, fluorescence spectroscopy, lithium ions, two-dimensional materials, battery interfaces, electrochemistry, quantum sensing, spectral shifts, microfluidics, ion discrimination

The review, led by Taghreed M. Adnan of Al-Karkh University of Science in Baghdad together with colleagues from institutions in Iraq and Pakistan, systematically evaluates seven classes of two-dimensional adsorbents: graphene and its derivatives, MXenes, two-dimensional metal-organic frameworks, covalent organic frameworks, layered double hydroxides, phosphorene, and hexagonal boron nitride. Rather than relying on incineration or energy-intensive destruction technologies, which remain costly and difficult to deploy at municipal scale, the adsorption approach captures PFAS molecules directly from water, concentrating them onto a solid material that can then be managed or regenerated. The central question the authors address is which of these ultrathin materials performs best, and why.

The answer, according to the accumulated literature, is graphene. Graphene and its oxidized cousin, graphene oxide, consistently rank among the top performers for PFAS capture, and the reasons are rooted in fundamental materials science. A single gram of graphene can present thousands of square meters of surface area, providing an enormous number of binding sites. More importantly, the surface chemistry of graphene oxide can be precisely tuned: researchers can graft amine groups, fluorine moieties, polyethyleneimine, or alkyl amines onto the nanosheets to create electrostatic and hydrophobic attractions tailored to the long, water-repelling fluorinated tails of PFAS molecules. Molecular dynamics simulations have confirmed that functionalization dramatically strengthens the interaction between the nanosheet and perfluorooctanoic acid and perfluorooctanesulfonate, the two most studied legacy compounds.

Experimental studies bear this out. Amino-functionalized graphene oxide aerogels have shown high removal efficiency for PFOA across varying pH conditions and water matrices, while fluorinated graphene oxide combined with polyethyleneimine has been assembled into three-dimensional porous platforms capable of capturing PFAS alongside pharmaceutical toxins and waterborne pathogens. Recent work has even pushed the concept to remarkable extremes: graphene oxide engineered with an ultrathin adlayer of roughly one nanometer achieved near-instantaneous removal of multiple PFAS species, suggesting that carefully designed interlayer galleries can act as molecular traps. Electrosorption approaches, in which an alternating electric field drives PFAS onto and off of graphite or graphene-based electrodes, add a further dimension of control, enabling reversible capture and release that could simplify adsorbent regeneration and reduce operational costs.

Close behind graphene, the review identifies MXenes as the second-best-performing family, despite a comparatively limited number of published studies. MXenes are two-dimensional transition metal carbides and nitrides, typically produced by etching aluminum from layered ceramic precursors such as titanium aluminum carbide. The resulting sheets, exemplified by Ti3C2Tx, carry a rich complement of surface terminations including hydroxyl, oxygen, and fluorine groups, which give the material both structural and electrochemical stability and a versatile charge landscape for binding anionic PFAS. Studies comparing MXenes against commercial anion-exchange and PFAS-specific resins found the nanosheets competitive even for zwitterionic PFAS, a subclass that many conventional adsorbents struggle to capture. MXene-based electrodes have also demonstrated effective electrosorption of PFOA, and delaminated titanium carbide MXenes have shown that surface chemistry, not merely surface area, governs the adsorption mechanism and overall removal efficiency.

The engineered porosity of two-dimensional metal-organic frameworks and covalent organic frameworks gives these materials a distinct advantage of a different kind. MOFs are crystalline lattices of metal nodes connected by organic linkers, while COFs are purely organic frameworks stitched together by strong covalent bonds; both can be designed with precisely sized pores and functionalized internal surfaces. Mesoporous MOFs have been shown to sorb perfluorooctanesulfonate efficiently from aqueous solutions, and zirconium-based MOFs, particularly those decorated with free hydroxyl groups, have achieved enhanced PFOA uptake, with crystal topology and interior surface functionality playing decisive roles. On the COF side, amine-functionalized frameworks have successfully removed GenX and other perfluorinated alkyl substances from water, while cationic COFs exploit electrostatic attraction to cooperative effect, in one case simultaneously serving as fluorescent sensors that signal PFOA capture in real time.

Layered double hydroxides operate on a simpler but elegant electrostatic principle. These positively charged metal hydroxide layers, built from combinations such as magnesium-aluminum or zinc-aluminum, present an inherently favorable surface for the negatively charged heads of PFAS molecules. Studies of Mg-Al and Zn-Al LDHs, including hydrotalcite, have demonstrated strong adsorption of PFOA and the industrial substitute F-53B, with mechanisms encompassing surface adsorption, interlayer anion exchange, and in some cases subsequent thermal decomposition of the captured precipitates. Organic functionalization of the LDH interlayers further boosts performance, and research into adsorbent aging and thermal regeneration is clarifying how these materials can be cycled repeatedly in real treatment trains. Hexagonal boron nitride, meanwhile, brings a graphene-like layered architecture together with exceptional chemical and thermal stability; porous h-BN has even been used to adsorb PFOS and PFDA from water and then destroy the captured molecules through simultaneous thermal decomposition, regenerating the adsorbent in the same step.

The most enigmatic entry in the review is phosphorene, the two-dimensional form of black phosphorus. Although far less studied than the other materials, phosphorene possesses a highly reactive surface owing to its elevated electron density, and density functional theory calculations have shown that strain engineering can substantially modulate PFOS adsorption on both pristine and defected phosphorene sheets. This tunability hints at significant untapped potential, though the material’s sensitivity to oxidation in water remains a practical hurdle that future work must address. Taken together, the comparative analysis makes clear that no single material is a universal solution: performance depends on PFAS chain length, water chemistry, competing organic matter, ionic strength, and the ever-growing diversity of short-chain and replacement compounds entering the environment.

What emerges from this synthesis is a roadmap. Graphene offers unmatched surface area and chemical versatility; MXenes add electrochemical robustness and electrosorption capability; MOFs and COFs contribute designer porosity and molecular recognition; LDHs deliver charge-matched capture with regeneration options; h-BN combines stability with the possibility of integrated adsorption and destruction; and phosphorene beckons as a reactive, strain-tunable frontier. The authors emphasize that translating these laboratory successes into real-world water treatment will require advances in synthesis scalability, adsorbent cost, regeneration cycles, and validation across the complex matrices of actual drinking water and wastewater. Yet the trajectory is unmistakable. As regulators worldwide tighten PFAS limits and public concern over forever chemicals intensifies, these atomically thin materials, each just one or a few atoms thick, are positioning themselves as some of the most powerful tools yet devised for cleaning up one of the most stubborn pollution problems of the modern age.

Subject of Research: Two-dimensional nanomaterials for the adsorption and removal of PFAS from contaminated water

Article Title: Emerging two-dimensional materials in PFAS remediation: a comprehensive review of adsorption mechanisms and efficiency

Article References: Adnan, T. M., Hasan, M. B., Jweeg, M. J., Hamad, A. J., Salih, S., Ammory, Z. H., Tariq, M. F., & Kadhom, M. (2026). Emerging two-dimensional materials in PFAS remediation: a comprehensive review of adsorption mechanisms and efficiency. Environmental Science and Pollution Research. https://doi.org/10.1007/s11356-026-38227-4

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38227-4

Keywords: PFAS, forever chemicals, two-dimensional materials, graphene, MXenes, metal-organic frameworks, covalent organic frameworks, layered double hydroxides, hexagonal boron nitride, phosphorene, adsorption, water treatment

The underlying problem is well known to memory engineers. Crossbar arrays, in which memory elements sit at the intersections of perpendicular word lines and bit lines, offer the most compact possible memory layout and can be stacked in three dimensions. But in a passive crossbar without a selector, current sneaks through neighboring unselected cells along paths known as sneak currents, corrupting the readout of the intended cell. Selectors are two-terminal devices placed in series with each memory element—forming one-selector-one-resistor or one-selector-one-capacitor cells—to suppress these parasitic currents. An ideal selector must be extremely nonlinear, passing large current only at its selected operating voltage while blocking current at half or a fraction of that voltage, yet it must also survive trillions of switching cycles, respond in nanoseconds, remain stable across temperatures and operate identically from device to device. No single selector technology has satisfied all of these requirements simultaneously.

The USC-led team’s answer is a graded tunnel barrier realized entirely within a van der Waals heterostructure. Instead of a single uniform insulating barrier, the device stacks materials of different band alignments so that the effective barrier profile changes with applied voltage. At low voltages, the barrier remains thick and high, strangling leakage current to negligible levels. As the voltage across the device rises toward the read or write condition, the barrier is thinned and lowered in a controlled fashion, allowing electrons to tunnel through with high efficiency. The result is an exponential increase in current over a small voltage window—precisely the nonlinearity that crossbar selectors demand.

To move beyond trial and error, the researchers developed a theoretical model that predicts the electrical characteristics of selectors with graded tunnel barriers. Guided by this model, they designed and fabricated two specific device structures. In the first, the primary tunnel barrier is hexagonal boron nitride, the wide-bandgap insulator often called white graphene. In the second, the barrier is gallium sulfide, a layered semiconductor with a smaller bandgap. Both variants sandwich the barrier between two layers of molybdenum disulfide, with graphene sheets serving as the top and bottom electrodes, forming the complete five-layer stack graphene/molybdenum disulfide/barrier/molybdenum disulfide/graphene.

The performance of the hexagonal boron nitride device is striking. It exhibits a nonlinearity exceeding 10 million, meaning the current at the operating voltage is more than ten million times larger than the leakage current at reduced voltages—among the highest values reported for any two-terminal selector. Perhaps more impressive is its endurance: the device survived more than a trillion switching cycles without failure, a figure that dwarfs the lifetimes of many competing selector technologies and approaches what commercial memory products require. Switching occurs in less than 20 nanoseconds, the current-voltage characteristics show minimal temperature dependence, and the variation from one device to another is low—critical attributes for manufacturing, where billions of cells must behave nearly identically.

The gallium sulfide variant trades some nonlinearity for a dramatically reduced operating voltage. Because gallium sulfide has a smaller barrier height than hexagonal boron nitride, the device can deliver a nonlinearity above one million while operating at only 2.5 volts. Low-voltage operation matters enormously for modern memory, which must integrate with silicon circuitry whose supply voltages continue to shrink. A selector that requires high voltages to turn on forces the surrounding periphery circuitry to handle elevated stress; a selector that switches at 2.5 volts eases that burden and reduces overall energy consumption during write operations.

Beyond single devices, the team demonstrated that their selectors can be integrated into functional memory cells. They built one-selector-one-resistor cells by pairing the selectors with memristive devices, including a hafnium-oxide-based memristor stack with palladium electrodes, and they also demonstrated one-selector-one-capacitor configurations. This dual compatibility with both resistive nonvolatile memory and capacitive volatile memory suggests the selector technology is genuinely universal, applicable across different memory families rather than tied to a single cell type. The researchers benchmarked their devices against the broad landscape of existing selector technologies—including ovonic threshold switching chalcogenides, niobium oxide threshold devices, metal-insulator-metal tunnel diodes and mixed-ionic-electronic-conduction access devices—and found that the van der Waals approach uniquely combines high selectivity with trillion-cycle endurance, nanosecond speed, temperature stability and low variability.

Choosing van der Waals materials is central to the achievement. These layered crystals are held together by weak interlayer forces, so each atomic plane can be exfoliated and restacked like molecular building blocks without the dangling bonds and interfacial defects that plague conventional three-dimensional semiconductors. Atomically sharp interfaces mean the tunnel barrier thickness is controlled layer by layer, giving designers reproducible, deterministic barrier profiles. Graphene electrodes contribute their own advantages, providing chemically inert, highly conductive contacts that do not interdiffuse with the underlying layers. The same properties that have made van der Waals heterostructures a playground for condensed matter physics here translate directly into manufacturable device metrics: negligible cycling variation, minimal temperature dependence and good interdevice uniformity all flow from the crystalline perfection of the interfaces.

The implications extend toward the long-sought goal of three-dimensional memory stacking. Because the entire selector is built from vertically stacked two-dimensional layers, it is inherently stackable, unlike selectors that rely on complex oxide growth or electroforming processes that are difficult to repeat layer upon layer. Paired with scalable nonvolatile memories such as memristors and phase-change or resistive cells, these selectors could enable dense three-dimensional crossbar memories for storage-class memory, in-memory computing and neuromorphic artificial intelligence hardware, where analog crossbar arrays perform vector-matrix multiplications directly in hardware. The research team, whose work was supported by the Army Research Office, the Air Force Office of Scientific Research and the National Science Foundation, has also released the experimental and simulation data through the Harvard Dataverse, giving the broader community the tools to build on the design framework. As the demand for data storage and energy-efficient computation continues its relentless climb, devices that tame sneak currents with atomic precision may prove to be one of the quiet enablers of the next memory generation.

Subject of Research: Van der Waals tunnel-junction selector devices with graded tunnel barriers for high-density memory crossbar arrays

Article Title: High-performance tunnel-junction selectors with graded tunnel barriers based on five-layer van der Waals heterostructures

Article References: Liu, H., Liao, H.-T., Li, M., Yang, N., Hsu, T.-H., Zhao, R., Xu, Y., Kim, S. J., Ni, Y., Chenna, V., Mahalingam, K., Bowers, C., Ganguli, S., Roy, A. K., Watanabe, K., Taniguchi, T., Hashemi, H., Guo, J., Dubey, M., … Joshua Yang, J. (2026). High-performance tunnel-junction selectors with graded tunnel barriers based on five-layer van der Waals heterostructures. Nature Electronics. https://doi.org/10.1038/s41928-026-01704-2

Image Credits: AI Generated

DOI: 10.1038/s41928-026-01704-2

Keywords: van der Waals heterostructures, tunnel-junction selector, memory crossbar arrays, molybdenum disulfide, hexagonal boron nitride, gallium sulfide, memristors, nonlinearity, endurance, three-dimensional memory, nanoelectronics, Nature Electronics