The team used a classic hydrothermal approach, dissolving ferric chloride hexahydrate in a 96 percent ethanol solution and sealing twelve-milliliter aliquots into a small PTFE-lined reactor held at 180 degrees Celsius. By quenching the reaction at 15, 30, 45, 60, 90, and 120 minutes, the researchers effectively froze the crystal growth process at successive stages. Each sample was then interrogated with X-ray diffraction to identify the crystalline phases present, field emission scanning electron microscopy to capture the changing particle shapes, and transmission electron microscopy, including high-resolution imaging, to probe the internal structure. Particle dimensions were extracted statistically, with at least fifty particles measured per stage and one hundred particles used for the final size distribution, a level of sampling that lends confidence to the quantitative claims.

The diffraction data tell a clean story of phase evolution. At fifteen and thirty minutes, the patterns show only the characteristic reflections of iron oxyhydroxide, FeOOH, with peaks at 2-theta values of 21.2, 33.3, and 36.6 degrees corresponding to its (110), (021), and (111) planes. By forty-five and sixty minutes, those peaks begin to fade while the signature reflections of alpha-Fe2O3, hematite, emerge at 24.1, 33.2, 35.6, 49.5, and 54.1 degrees. At ninety and one hundred twenty minutes, the FeOOH signal has vanished entirely, confirming complete conversion. This sequence supports a two-track transformation: dissolution and recrystallization in solution, running alongside a solid-state phase transition within the aggregates themselves.

The electron microscopy images add the visual drama. In the earliest frames, the reaction vessel is full of short, needle-shaped FeOOH crystals averaging about forty-three nanometers in size. By thirty minutes these needles have assembled into dense aggregates, and hematite begins to nucleate on their surfaces. Continued heating coaxes the aggregates into ellipsoidal particles, reaching an average length of 0.68 plus or minus 0.1 micrometers and a width of 0.42 plus or minus 0.1 micrometers. The most striking feature appears late in the process: the surfaces of the mature ellipsoids roughen and develop visible porosity, with a dominant pore diameter of 27.36 plus or minus 3 nanometers, measured across two hundred pore points on twenty particles.

Why should a simple dehydration reaction leave behind such an orderly porous architecture? The authors argue that the answer lies in crystallography rather than chemistry alone. FeOOH adopts a monoclinic, rhombohedral-type structure in which iron atoms sit in octahedral coordination with oxygen and hydrogen. Hematite, by contrast, is hexagonal, with oxygen layers packed in a hexagonal close-packed arrangement. Converting one into the other obliges every atom to migrate to a new lattice position. As the reaction proceeds, thermally driven dehydration strips structural water from the lattice, collapsing hydrogen-bonded water layers and forcing the iron-oxygen framework to reconfigure. The removal of that water builds internal stress, and the resulting anisotropic lattice contraction creates mismatches and voids that ultimately open to the surface as pores.

In other words, the porous ellipsoid morphology is not a byproduct of the synthesis but is inherently coupled to the monoclinic-to-hexagonal transition. The researchers also note that hematite becomes the thermodynamically favored phase above roughly eighty degrees Celsius, based on established Gibbs free-energy data, which explains why the conversion runs to completion under their hydrothermal conditions. Earlier classical studies of iron oxide precipitation, including the foundational work of Matijević and of Sugimoto and Muramatsu, examined largely non-porous morphologies under ambient or low-pressure conditions; the present study extends that framework to hydrothermal constraints, where interfacial nucleation and anisotropic lattice rearrangement jointly drive pore formation.

The growth pathway can be summarized in four stages. First, ferric ions in solution nucleate and grow into needle-shaped FeOOH. Second, those needles aggregate into micro-ellipsoid structures, a process the authors link to oriented attachment and aggregation-induced self-assembly, mechanisms well documented in oxide systems such as silica and iron oxide, where primary nanoparticles align into mesocrystals and then fuse their lattices under hydrothermal stress. Third, FeOOH within the aggregates converts to hematite through the combined action of solid-state transformation and dissolution-recrystallization, while free FeOOH in solution dissolves and feeds further hematite growth. Fourth, thermal stress drives dehydration and lattice rearrangement, opening the nano-pores and yielding the final ellipsoidal particles with their characteristic roughened surfaces.

The significance of the work extends beyond a single mineral. Because crystal morphology governs surface area, reactivity, and optical and magnetic behavior, controlling shape at the nanoscale is a central goal of materials chemistry. Porous hematite in particular is prized for applications ranging from photocatalysis and water treatment to catalysis and energy materials, and previous studies have reported porous hematite nanorods and nanosheets with useful photocatalytic and magnetic properties. By showing that the pores arise from a predictable crystallographic transition rather than from sacrificial templates or etchants, the study offers a template-free route to porous architectures, one in which reaction time and temperature become the primary control knobs.

The methodology itself is also worth noting for its rigor. The team calibrated particle statistics across large sample populations, fitted their diffraction data with pseudo-Voigt functions for microstructural analysis, and cross-checked morphology at multiple magnifications and with complementary techniques. Funding came from the National Natural Science Foundation of China’s Youth Fund and an open fund from a Ministry of Education key laboratory for solid waste treatment, reflecting the study’s dual relevance to fundamental mineralogy and applied resource science. The authors state that the findings provide a theoretical basis for future research on mineral crystal growth, with implications spanning mineralogy, geochemistry, and advanced material fabrication.

For a mineral that humans have ground into pigment for tens of thousands of years, hematite continues to yield new physics at the nanoscale. What this study makes clear is that even a seemingly mundane dehydration reaction encodes a rich sequence of dissolution, nucleation, aggregation, and lattice collapse, and that each step leaves its fingerprint in the final particle. Watching that sequence unfold in real time, one timed aliquot at a time, turns a jar of red powder into a record of its own formation, and suggests that other porous mineral morphologies may likewise be decoded by simply slowing down and watching the crystals grow.

Subject of Research: Hydrothermal synthesis and crystal growth mechanism of nano-porous ellipsoidal hematite from FeOOH precursors

Article Title: Synthesis of nano-porous ellipsoid hematite and the crystal growth mechanism

Article References: Synthesis of nano-porous ellipsoid hematite and the crystal growth mechanism. (n.d.). https://doi.org/10.5194/ejm-38-575-2026

Image Credits: AI Generated

DOI: 10.5194/ejm-38-575-2026

Keywords: hematite, iron oxide, FeOOH, hydrothermal synthesis, crystal growth, nanoporous materials, phase transformation, lattice rearrangement, mineralogy, X-ray diffraction, electron microscopy, nanomaterials

The research team, led by Dipali Potdar of Jaysingpur College and Shivaji University together with colleagues including corresponding authors Shivaji Sadale and Prashant Chikode, electrodeposited nickel thin films onto 304-grade stainless steel substrates from simple sulfate baths. They systematically varied three parameters that any plating shop can control: the applied deposition potential, the pH of the electrolyte, and the concentration of nickel ions in solution. By sweeping nickel sulfate concentrations from 25 to 50 millimolar and adjusting pH from 4 to 8 with ammonium hydroxide, they created a matrix of deposition conditions whose effects could be traced all the way from current signatures to crystal structure.

The central analytical tool was the Scharifker-Hills model, a theoretical framework developed in 1983 that remains the workhorse for interpreting nucleation during electrodeposition. The model distinguishes between two limiting behaviors. In instantaneous nucleation, all active sites on the electrode surface are occupied essentially at once, so the number of nuclei is fixed from the start and each nucleus simply grows. In progressive nucleation, new sites continue to activate throughout the deposition, so the population of nuclei keeps increasing. The shape of the current-time transient, recorded when a fixed potential is applied, carries the fingerprint of whichever mechanism dominates, and comparing normalized experimental curves against the model’s dimensionless predictions reveals the mechanism at work.

Before diving into transients, the team used cyclic voltammetry to establish the electrochemical landscape of their bath. Sweeping the potential from 0.7 volts down to minus 1 volt against a silver-silver chloride reference electrode, they observed a stable current until an onset potential near minus 0.7 volts, followed by a rapid rise and a cathodic peak at minus 0.88 volts, which they attribute to the reduction of nickel ions on the stainless steel surface. A further surge at more negative potentials signaled the onset of the hydrogen evolution reaction, the parasitic process that plagues nickel plating by generating gas bubbles at the electrode. Two crossover points on the reverse scan, at minus 0.78 and minus 0.43 volts, marked the initiation of nucleation and the adsorption of nickel ions on the surface, while an anodic peak at minus 0.2 volts reflected nickel oxidation.

The voltammetry also revealed that the deposition reaction is diffusion-controlled. Recording curves at scan rates of 10, 20, and 30 millivolts per second, the researchers found that the anodic peak current density scaled linearly with the square root of the scan rate, exactly the relationship predicted by the Randles-Sevcik equation for a process limited by how fast nickel ions can travel to the electrode. This diffusion control proved crucial for interpreting everything that followed, because when ions arrive at the surface faster than they can be replenished from the bulk solution, the geometry of the depletion zones around growing nuclei shapes both the current response and the final film morphology.

Chronoamperometry, the recording of current as a function of time at a fixed applied potential, then exposed the three-act drama of nickel electrocrystallization. In the first fraction of a millisecond, a sharp spike and decay of current reflects double-layer charging and ion adsorption. A rapid rise follows as new nuclei form and each one draws a hemispherical diffusion zone around itself, pushing the current to a maximum. Beyond that peak, the current decays in a manner governed by the Cottrell equation, the classic signature of diffusion-limited mass transfer, before settling into a plateau where the supply of nickel ions from the bulk solution constrains everything. This characteristic profile confirmed that nickel deposition on stainless steel follows a three-dimensional nucleation process, with hemispherical clusters growing and eventually coalescing into a continuous film.

The comparison with the Scharifker-Hills model produced the study’s most striking finding: the nucleation mechanism is not fixed but shifts with deposition conditions. At underpotentials, where the driving force is modest, the transients tracked the progressive nucleation curve, because the nucleation rate lagged behind the growth rate and new sites kept activating. At overpotentials, the curves aligned closely with instantaneous nucleation, since the nucleation barrier is overcome quickly and a large population of nuclei forms simultaneously. At the reduction potential itself, a mixed mechanism appeared. Raising the bath pH from 4 to 8 pushed the system toward progressive nucleation, which the authors attribute to pH-dependent changes in hydroxide species and surface energetics that favor the continuous creation of new nucleation sites over time.

Concentration played an equally decisive role. Films grown from the most dilute 25 millimolar bath followed the instantaneous nucleation curve, while the 37 and 50 millimolar baths produced mixed instantaneous and progressive behavior, echoing earlier observations of silver deposition on glassy carbon. The team notes that experimental curves deviated from ideal theory in places, with a slower current decay than predicted, which they attribute to side processes such as hydrogen evolution, adsorption, and charge-transfer resistance. These deviations are a reminder that real plating baths are chemically messy systems, and that the clean limiting cases of nucleation theory blend into one another under practical conditions.

What makes the study compelling is that the electrochemical fingerprints translated directly into physical film quality. X-ray diffraction confirmed the cubic crystal structure of nickel in every film, with a prominent reflection from the (111) planes at 44.5 degrees, and the Williamson-Hall analysis of peak broadening revealed compressive microstrain induced by the stainless steel substrate. Notably, crystallite size, lattice constant, and texture coefficient barely changed across the parameter range, but strain and dislocation density dropped to negligible levels at the highest pH and concentration. Meanwhile, field-emission scanning electron microscopy showed a dramatic morphological transition: films from acidic, dilute baths were rough and cracked, riddled with grain boundaries, while films from alkaline, concentrated baths were smooth, uniform, and compact. The culprit behind the cracking is the hydrogen evolution reaction, whose disruptive bubbles and induced internal stress scar the growing film at low pH but are largely suppressed in alkaline conditions.

The practical implications ripple outward from the plating bath. The authors point out that cracked, fine-grained films with abundant grain boundaries resist dislocation movement and are therefore harder, but the same boundaries promote corrosion, whereas the coarser, compact films grown at higher pH and concentration conduct electricity better and resist corrosion. Because nickel coatings serve industries ranging from metal decoration and electronic components to catalysis and energy storage, the ability to dial in a specific nucleation mechanism and morphology through nothing more exotic than pH, concentration, and potential offers a low-cost route to tailored coatings. The researchers acknowledge support from the Mahatma Jyotiba Phule Research and Training Institute, and their work stands as a reminder that some of the most consequential physics in manufacturing happens in the first milliseconds, when a handful of atoms decides what kind of surface the world will see.

Subject of Research: Nucleation and growth kinetics during the electrodeposition of nickel thin films on stainless steel

Article Title: Studies on nucleation and growth kinetics during electrodeposition of nickel thin films

Article References: Potdar, D., Patil, S., Kulkarni, Y., Pawar, N., Banne, S., Sadale, S., & Chikode, P. (2026). Studies on nucleation and growth kinetics during electrodeposition of nickel thin films. Discover Electrochemistry, 3(1), Article 29. https://doi.org/10.1007/s44373-026-00115-4

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00115-4

Keywords: electrodeposition, nickel thin films, nucleation kinetics, Scharifker-Hills model, chronoamperometry, cyclic voltammetry, stainless steel substrate, hydrogen evolution reaction, X-ray diffraction, FESEM, bath pH, crystal growth

Chirality, the property of an object that cannot be superimposed on its mirror image, is usually associated with the handedness of molecules such as amino acids or DNA. Pasteur famously separated the left- and right-handed crystals of tartaric acid in 1848, and chemists have long known that achiral molecules can occasionally crystallize into chiral forms. But deliberate, controllable twisting in inorganic crystals remains rare, and in layered materials it is rarer still. Previous examples have relied on screw dislocations, which impose an Eshelby twist on growing whiskers, or on growth on curved, non-Euclidean surfaces that force layered crystals into supertwisted spirals. The new work demonstrates a different mechanism altogether, one rooted in the internal architecture of the crystal lattice itself.

The materials at the heart of the study are two-dimensional organic-inorganic hybrid perovskites of the general form (organic)2PbBr4, in which sheets of corner-sharing lead-bromide octahedra are separated by layers of organic cations. These cations are not passive spacers. In the compound (FCA3)2PbBr4, where FCA3 is a fluorinated aromatic cation, the organic layers form hydrogen-bonded networks that the authors describe as hydrogen-bonded organic frameworks embedded within the inorganic lattice. Using single-crystal X-ray diffraction, the team determined the structures at 150 K and 294 K, with crystallographic data deposited at the Cambridge Crystallographic Data Centre under deposition numbers 2485415, 2485416 and 2485417. The structures revealed that the hydrogen-bonded organic networks and the inorganic lead-bromide sheets want to deform in incompatible ways when the crystal grows.

That incompatibility is the essence of geometric frustration. As a ribbon grows from a supersaturated solution, mismatched strains accumulate between the organic and inorganic sublattices. When the strain is released, the ribbon relieves it by bending and twisting, exactly as a seed pod, made of two layers with different shrinkage directions, coils as it dries. The researchers combined brightfield and cross-polarized optical microscopy, scanning electron microscopy, transmission electron microscopy with selected-area electron diffraction, and molecular dynamics simulations to connect the atomic-scale mismatch to the macroscopic shape. The simulations, carried out by Zhichen Nian under the supervision of Brett M. Savoie, reproduced the spontaneous deformation of the ribbons and confirmed that incompatible elasticity within the lattice, rather than any external influence, drives the twisting.

The scale of the phenomenon is remarkable. The team documented ribbons roughly one micrometer wide and about a millimeter long carrying as many as 86 complete twists along their length, grown simply by cooling a supersaturated solution at 2.5 degrees Celsius per minute from 75 to 55 degrees Celsius. Crucially, microscopy under brightfield, photoluminescence and cross-polarized modes showed that the twisted microribbons are free of internal boundaries, meaning each ribbon is a single crystal that has deformed elastically rather than a composite of misoriented domains. Statistical and mechanical analyses of hundreds of ribbons showed that the shape is governed by intrinsic elastic strain and geometric constraints, and that tuning those parameters allows a continuous transition from twisted ribbons to fully helical ones.

Perhaps the most consequential discovery concerns handedness. Because the underlying molecules are achiral, one might expect equal numbers of left- and right-handed ribbons, yielding no net optical signature. Instead, the researchers found that the direction of twisting is controlled by crystal symmetry and by growth kinetics. By adjusting the cooling rate, for example to a slow 0.044 degrees Celsius per minute, they could bias nearly all ribbons in a bulk sample to twist in the same direction, producing centimeter-sized forests of ribbons with a single handedness. Ensemble-averaged circular dichroism measurements on these chirality-pure samples showed genuine chiroptical activity. The team took particular care to isolate the true signal: by rotating the sample about the light axis and flipping it, they removed artifacts arising from linear birefringence and linear dichroism, leaving the circular dichroism that arises from the coupling between electronic and magnetic transition dipoles.

The symmetry analysis explains why the effect appears in some compositions and not others. The inorganic [PbBr4]2- lattices contain specific symmetry elements, such as 21 screw axes or inversion centers, positioned at precise crystallographic sites, and the morphology of the growing crystal reflects these elements. When the team doped a second cation, BrCA3, into the (FCA3)2PbBr4 lattice, the doped crystals adopted the triclinic space group P-1 and their hydrogen-bonded organic networks aligned in a configuration resembling that of the pure (BrCA3)2PbBr4 compound. Partial occupancy refinement, made possible by the strong scattering contrast between fluorine and bromine, established a doping level of about 18 percent in one crystal, corresponding to the composition (FCA3)1.821(BrCA3)0.179PbBr4. The doped crystals showed markedly different twisting behavior, demonstrating that molecular doping offers a practical handle for tuning the frustration and hence the final morphology.

The work situates layered perovskites within a broader family of twisting crystals that includes benzamide, hippuric acid, aspirin and cholesterol monohydrate, all of which form helicoidal or twisted habits through growth-actuated bending. It also echoes recent advances in van der Waals materials, where chiral twisted nanowires and helical crystals with discretized Eshelby twist have been reported, and in nanoplatelet systems where ligand-induced curvature mismatches control polymorphism and chirality. What distinguishes the new result is the mechanism: rather than dislocations, external templates or curved substrates, the twist emerges from the interplay of two chemically distinct, hydrogen-bonded and ionic sublattices within a single crystal. The authors suggest this provides a general strategy for programming chiral shapes into layered two-dimensional materials through molecular design.

The practical implications could extend well beyond crystallography. Chiral perovskites are already of intense interest for spintronics, where chiral-induced spin selectivity has enabled room-temperature spin light-emitting diodes, and for photovoltaics, where chiral-structured heterointerfaces have been shown to improve the durability of solar cells. A material that can be grown in bulk with controlled handedness, using nothing more than cooling rate and molecular doping, would be an attractive platform for such technologies, as well as for circularly polarized light detection and chiral optoelectronics. Because the twisting is an elastic response baked into the lattice, it also raises the possibility of dynamic behavior, analogous to the reversible twisting motions observed in other molecular crystals and to light-powered flagella-like motion in photomechanical microwires.

For now, the study stands as an elegant demonstration that macroscopic chirality can be encoded in the geometry of interactions at the molecular scale. A crystal built from mirror-symmetric parts, given the right internal mismatch and the right growth conditions, will coil itself into a helix with a preferred hand, and that hand can be read out optically from an ensemble of thousands of ribbons. The researchers, whose work was supported by the US Department of Energy Office of Basic Energy Sciences and the US National Science Foundation, describe their results as a route to controlling chiral morphologies in layered two-dimensional materials. If the principle generalizes across the rich family of hybrid perovskites and related layered compounds, the humble twisted ribbon may become a standard building block in the designer materials of the coming decade.

Subject of Research: Geometric frustration driving spontaneous chiral twisting in layered halide perovskite nanoribbons

Article Title: Geometric frustration in morphologically chiral nanoribbons of layered perovskites

Article References: Shao, W., Nian, Z., Lu, Y., Yang, H., Yu, Y., Savoie, B. M., & Dou, L. (2026). Geometric frustration in morphologically chiral nanoribbons of layered perovskites. Nature Synthesis. https://doi.org/10.1038/s44160-026-01167-5

Image Credits: AI Generated

DOI: 10.1038/s44160-026-01167-5

Keywords: layered perovskites, geometric frustration, chirality, nanoribbons, two-dimensional materials, hydrogen-bonded organic frameworks, circular dichroism, molecular doping, crystal growth, elastic strain, chiroptical activity, metal-halide perovskites

Writing in Nature Photonics, Jiaqi Liu and colleagues, working under the supervision of Guangda Niu of the Wuhan National Laboratory for Optoelectronics at Huazhong University of Science and Technology and Mengling Xia of the Wuhan University of Technology, describe a design strategy built on so-called zero-dimensional structured materials. In such crystals, the functional building blocks are isolated molecular units that do not share bonding directions with their neighbours in any crystallographic orientation. Because each unit is electronically self-contained, cutting or growing the crystal in any direction never leaves behind broken chemical bonds at the surface. The result is a semiconductor that is, in the researchers’ terminology, dangling-bond-free along all crystallographic directions.

The significance of this property becomes clear when one considers how defects arise in ordinary semiconductors. A conventional three-dimensional crystal, such as silicon, shares covalent bonds in every direction, so any grain boundary or surface necessarily terminates those bonds and creates dangling bonds, chemically unsatisfied sites that trap charge carriers and dissipate energy as heat rather than light. Two-dimensional materials such as transition-metal dichalcogenides avoid this problem within their atomically thin planes, but their edges remain problematic. One-dimensional wires solve the edge problem along their axis yet still expose discontinuities at their tips and side surfaces. Even the celebrated halide perovskites, which have revolutionized solar cells and radiation detectors with their remarkable defect tolerance, rely on passivation strategies to tame their interfacial defects rather than eliminating them structurally.

Zero-dimensional materials sidestep this entire problem, but until now they carried a penalty of their own. Because the functional units are electronically isolated, charge and energy transport within them tends to be isotropic, meaning that a crystal grows with similar rates in all directions and adopts compact, blocky morphologies. That isotropy is excellent for electronic performance but awkward for imaging, where the geometry of the scintillator film matters enormously. In X-ray scintillation imaging, light generated deep inside a thick film scatters as it travels to the detector, and lateral spreading degrades spatial resolution. Columnar structures, in which parallel rods act like optical fibres channeling light toward the detector, are the standard remedy, as demonstrated by the structured caesium iodide scintillators used commercially since the late 1990s. Achieving such columnar growth without sacrificing the defect-free electronic character of the material seemed impossible, because the two requirements pull in opposite directions.

The Chinese team’s insight was that the geometry of a crystal and the electronic dimensionality of its structure can be decoupled. To do so, they exploited a subtle chemical lever built into the uranyl ion, a linear O=U=O unit in which a uranium atom is flanked by two strongly bonded oxygen atoms. In the model compound caesium uranyl chloride, Cs2UO2Cl4, the uranium–oxygen double bonds are dramatically stronger and more directional than the uranium–chlorine bonds that link neighbouring uranyl groups. This bonding disparity means the crystal’s growth kinetics differ from one crystallographic direction to another, even though the uranyl units themselves remain electronically isolated. By tuning the balance between the fast-growing and slow-growing facets, the researchers drove the crystals to elongate into one-dimensional rods while preserving the zero-dimensional, dangling-bond-free electronic framework intact.

The concept draws on classical crystal-growth theory that dates back more than a century. In 1901, Georg Wulff proposed that the equilibrium shape of a crystal is determined by the relative surface energies of its facets, and Carl Herring’s theorems of 1951 formalized how surface free energy governs morphology. The team applied this thermodynamic framework to the chemically anisotropic uranyl system, using it to predict which facets would dominate the equilibrium rod shape. They then validated the prediction at the atomic scale with transmission electron microscopy, characterizing the crystal boundaries to confirm that the expected surfaces form and that no problematic bonding discontinuities appear. The work was a collaboration among the Wuhan University of Technology, Huazhong University of Science and Technology and Beijing University of Technology, with Wei Wang and Yue Lu contributing the atomic-scale electron microscopy characterization.

On the computational side, the researchers employed density functional theory calculations with the DFT-1/2 correction method, a technique developed to overcome the systematic underestimation of band gaps in conventional approximations to density functional theory. This allowed them to model the electronic structure of the material accurately enough to confirm that the anisotropic crystal growth does not compromise the isotropic, defect-free electronic properties that make zero-dimensional semiconductors attractive in the first place. The combination of thermodynamic growth modelling, atomic-resolution microscopy and corrected band-structure calculations gave the team confidence that their design principle is physically robust rather than a lucky accident of one particular compound.

The payoff came when the columnar Cs2UO2Cl4 crystals were tested as an X-ray scintillator. Uranyl compounds have attracted growing interest as scintillator materials since 2018, when researchers first highlighted uranium as a distinct metal centre for building intrinsic X-ray scintillators, with the heavy uranium nucleus providing strong X-ray absorption and the uranyl luminescence providing efficient light emission. Subsequent work explored uranium-organic frameworks and uranyl-cluster compounds for flexible and thermally adaptive scintillators, but spatial resolution remained limited by the film structures those materials formed. The new columnar geometry changes that picture decisively: the team’s Cs2UO2Cl4 scintillator achieved a spatial resolution of 34 line pairs per millimetre, a figure that places it among the highest-resolution scintillation imaging media reported and corresponds to the ability to distinguish features finer than fifteen micrometres across.

The practical implications extend across medical diagnostics, industrial inspection and scientific instrumentation. In clinical X-ray imaging and computed tomography, higher spatial resolution translates directly into the ability to visualize finer anatomical structures and subtler lesions at lower radiation doses, because fewer photons are wasted on scattered, blurred light. In industrial and security screening, fine-resolution scintillators enable detection of small defects or threats. The researchers also emphasize the generalizability of their approach: the underlying principle, that anisotropic chemical bonding can be introduced within a zero-dimensional framework to sculpt crystal geometry without disturbing electronic isotropy, is not limited to uranyl halides. Any material family containing chemically inequivalent bonds between electronically isolated units could, in principle, be engineered the same way, opening a route to defect-tolerant semiconductors with customizable shapes for light-emitting diodes, photodetectors and other optoelectronic devices where interfacial defects have long been the performance bottleneck.

The study, published on 25 September 2026 in Nature Photonics, arrives amid intense global competition to improve radiation detection materials, with halide perovskites and their derivatives dominating recent advances. What distinguishes this work is its conceptual reframing: rather than passivating defects after they form, the team designed them out of the material at the structural level, then recovered the anisotropic geometry needed for high-resolution imaging through chemistry rather than through growth tricks that would reintroduce broken bonds. The authors declare no competing interests, and the work was supported by the National Natural Science Foundation of China, the National Key Research and Development Program of China, the Beijing Natural Science Foundation, the Shenzhen Science and Technology Program and Huazhong University of Science and Technology. If the zero-dimensional design philosophy proves as transferable as the authors anticipate, the humble dangling bond, long the bane of semiconductor engineering, may finally lose its grip on the next generation of imaging technology.

Subject of Research: Dangling-bond-free zero-dimensional Cs2UO2Cl4 scintillators for ultrahigh-resolution X-ray imaging

Article Title: Dangling-bond-free, chemically anisotropic semiconductors for ultrahigh-resolution X-ray imaging

Article References: Liu, J., Liao, M., Liu, X., Ma, N., Li, H., Wang, W., Lu, Y., Xu, Y., Luo, G., Tang, J., Xia, M., & Niu, G. (2026). Dangling-bond-free, chemically anisotropic semiconductors for ultrahigh-resolution X-ray imaging. Nature Photonics. https://doi.org/10.1038/s41566-026-02013-y

Image Credits: AI Generated

DOI: 10.1038/s41566-026-02013-y

Keywords: X-ray imaging, scintillators, zero-dimensional materials, dangling bonds, Cs2UO2Cl4, uranyl halide, crystal growth, spatial resolution, defect tolerance, semiconductors, Nature Photonics, optoelectronics

Each new family of twisted materials has repeatedly brought new rules for how electrons move and interact. In the language of theorists, each family offers a different Hamiltonian, the mathematical object that specifies a system’s energies and interactions, and therefore a new kind of quantum simulator. A recent Nature study of so-called M-point twisting illustrated the principle vividly: by changing the starting electronic structure of the constituent layers, researchers accessed fundamentally different models with new symmetries. The implication is that exploring other atomic architectures could uncover quantum states and theoretical models that today’s familiar platforms, built almost entirely around graphene and dichalcogenides, simply cannot reach.

Now an international collaboration spanning more than a dozen institutions has provided both the raw building blocks and a practical guide to that vast search. In two back-to-back papers publishing in Science on September 24, the team presents a sweeping computational survey of the two-dimensional materials universe. The first paper maps the electronic structures and topology of nearly 9,000 two-dimensional entries, regardless of whether they are topological. The second paper identifies more than 1,600 candidates whose electronic properties make them promising for twisting, each offering a different starting point for constructing entirely new kinds of quantum simulators.

The motivation behind the effort is straightforward but profound. Every new family of twisted materials gives researchers a chance to ask a different question about quantum matter, and the field has so far sampled only a handful of the possibilities. B. Andrei Bernevig, a professor of physics at Princeton University and coauthor of both studies, framed the ambition directly: the goal is to move beyond the few platforms currently known and explore the enormous range of physics that other layers and other twist angles could make possible. The two catalogs are designed to turn that open-ended dream into a systematic research program that any laboratory with an internet connection can join.

The first study extends topological quantum chemistry, a theoretical framework that connects a crystal’s chemistry and symmetries to the topology of its electronic states, to nonmagnetic two-dimensional materials. Symmetries are the operations, such as rotations and reflections, that leave a crystal’s atomic pattern unchanged, and they constrain how electronic waves can fit together throughout the crystal. Some electronic patterns carry a special robustness: their topology cannot change without a fundamental alteration of the electronic structure. A quantum spin Hall insulator, for example, can be insulating in its interior while carrying current along its edges through channels protected against certain disturbances. Such states offer a route to studying robust quantum behavior and have motivated a wide range of proposals for new electronic devices.

Working from entries in two computational materials databases, the researchers analyzed 8,872 two-dimensional materials and identified 4,073 with nontrivial topology or an obstructed atomic limit. The latter describes a different kind of unusual electronic organization: in one such class, symmetry constrains the centers of electronic charge to sit away from the atoms themselves. Cutting such a crystal along particular boundaries can then expose distinctive electronic states localized at the surface. Luis Elcoro of the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, senior author of one of the studies, explained the philosophy behind the work: the symmetry of a crystal yields rules for how electronic states can be arranged, and the team developed those rules for atomically thin layers and turned them into tools that other researchers can apply across thousands of materials.

Alongside the calculations, the collaboration developed crystallographic tables, analysis programs and a public resource called the Topological 2D Materials Database, which carefully distinguishes experimentally reported structures from purely computational candidates. Crucially, the catalog records electronic band structures, the spectrum of energies available to electrons, for layers both with and without topology. Its nearly 9,000 entries thus form a library of Lego-like building blocks. Two identical layers can be combined into a homobilayer, while two different layers can form a heterobilayer, and adding the freedom to choose their relative twist angle multiplies the possibilities into what the authors describe as an embarrassment of riches. It is precisely this combinatorial explosion that the second paper brings structure to.

The second study is built on the physics of moiré patterns, the large-scale interference patterns that emerge when two fine meshes are overlaid with a slight rotation. Something analogous happens when two atomically thin crystals are stacked and twisted: a moiré superlattice forms that dramatically changes how electrons move through the combined system. In suitable materials, twisting produces narrow electronic bands, in which electrons’ kinetic energy is suppressed and interactions between electrons become especially influential. This regime is fertile ground for superconductivity, magnetism and fractional quantum states, and it offers a controllable way to build quantum simulators, materials that physically enact models of interacting electrons, including models whose behavior remains unknown even to theorists.

Led by Yi Jiang, a Princeton postdoctoral researcher, the second study identifies 61 semimetal candidates and 1,568 insulating candidates whose electronic structures are suited to twisting and admit relatively simple theoretical descriptions. The candidates span hexagonal, square, rectangular and oblique crystal lattices, as well as different patterns of electron motion, so that each starting geometry corresponds to a different physical problem. Twisted square lattices, for instance, could simulate the Hubbard model, the paradigmatic framework central to research on high-temperature superconductivity, while rectangular systems could reveal behavior resembling electrons confined to one-dimensional chains. The team’s earlier M-point twisting study, published in Nature in 2025, showed that a different starting electronic structure produces models with new symmetries and new possibilities for simulating interacting electrons, and the new catalog vastly expands the range of such starting points.

The work also reaches beyond computation into the laboratory. The researchers calculated selected twisted bilayers and found narrow bands in compounds including tin diselenide and hafnium disulfide, and they grew bulk crystals of these compounds along with tin disulfide, gallium telluride and zirconium nitride chloride. Initial sample preparation confirmed that the grown materials can be exfoliated, peeled down layer by layer, to single atomic sheets, a critical practical requirement for assembling twisted devices. Leslie M. Schoop, professor of chemistry and director of the Princeton Center for Complex Materials, emphasized that connecting the catalog to crystal growth and exfoliation provides a practical route from an electronic structure computed on a computer to a real sample in the laboratory. Kin Fai Mak of Cornell University added that some candidates are already crystals that can be grown and peeled to a single layer, giving experiments a concrete starting point for building new twisted structures and testing the physics predicted for them. The catalog classifies candidates purely by their electronic suitability for twisting, so the next step is to assemble the layers into devices and probe their collective behavior, a challenge that coauthor Dmitri K. Efetov of Ludwig Maximilian University of Munich says will involve controlling both twist angle and electron density in each new material.

The shared database, assembled by Princeton physics researcher Nicolas Regnault, who is also affiliated with the Flatiron Institute, the École normale supérieure in Paris and the French National Centre for Scientific Research, is intended as a community resource that lets researchers compare individual layers and select candidates for whichever physics they wish to investigate. The logic of the project is deliberately bidirectional: theorists can start from a known problem about interacting electrons and ask which crystal, which layers and which twist will let them study it, while experiments on the cataloged materials may reveal collective states no one anticipated. As Bernevig concluded, the exciting part is that an experiment can also show researchers something they did not know to ask. The publicly available preprints behind the studies, covering the two-dimensional topological quantum chemistry catalog and the theoretically twistable material database, ensure that the full library of building blocks, from quantum spin Hall insulators to Hubbard-model-ready square lattices, is now open to anyone hunting for the next quantum state of matter.

Subject of Research: Computational catalogs of topological and twistable two-dimensional materials for quantum simulation

Article Title: New catalogs map the quantum possibilities of atomically thin materials

Article References: New catalogs map the quantum possibilities of atomically thin materials. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: twistronics, two-dimensional materials, topological quantum chemistry, moiré patterns, quantum simulators, superconductivity, quantum spin Hall insulators, twisted bilayers, materials database, fractional Chern insulators, crystal growth, narrow bands

That bottleneck may finally be easing. A team led by Wei Zhai, Zhenyu Shi, Rui Tao, Zijian Li, Zhuangchai Lai and Hua Zhang, working across the City University of Hong Kong, The Hong Kong Polytechnic University and partner institutions, has published a detailed protocol in Nature Protocols describing a salt-assisted method that reliably converts ordinary 2H-phase crystals into phase-pure, highly crystalline 1T′-phase materials. The procedure covers a broad compositional palette, including MoS2, MoSe2, WS2, WSe2 and the mixed-chalcogen alloys MoS2xSe2(1−x) and WS2xSe2(1−x), and it does so at a scale that previous approaches could only dream of: gram quantities per batch, with individual crystals reaching hundreds of micrometers across.

The elegance of the method lies in its simplicity. Rather than building 1T′ crystals from scratch under exotic conditions, the protocol starts with commercially available 2H-phase transition metal dichalcogenides and co-anneals them with elemental chalcogen powders, such as sulfur or selenium, together with common alkali metal salts such as potassium oxalate hydrate or potassium carbonate. The reaction is carried out in a sliding tube furnace under a hydrogen-argon atmosphere. When the mixture is heated, the alkali metal salts act as the trigger for a remarkable structural transformation, coaxing the atomic layers of the stable 2H phase to slide and distort into the metastable 1T′ configuration. The chalcogen vapor maintains the correct chemical environment, preventing decomposition while the phase change proceeds.

Understanding why this works requires a brief tour of the underlying crystallography. In the 2H phase, each metal atom sits in a trigonal prismatic coordination environment, and the layers stack in a specific sequence that renders the material a semiconductor. The 1T′ phase, by contrast, features octahedral coordination with a periodic lateral displacement of the metal atoms, breaking the symmetry in a way that produces metallic conductivity. Because the 1T′ arrangement is metastable, it does not form spontaneously under ordinary synthesis conditions; it must be kinetically trapped. Alkali metal ions appear to facilitate this trapping by intercalating between the layers, weakening the interlayer bonding and lowering the energetic barrier for the intralayer atomic rearrangement. Subsequent deintercalation of these ions leaves behind the transformed lattice, now locked into its new metastable geometry.

The published protocol walks researchers through every stage of this process with unusual care. It specifies the setup of the sliding tube furnace, a configuration that allows the reactants to be rapidly moved into and out of the hot zone, giving precise control over reaction timing. It details the loading of the 2H-phase starting materials, the chalcogen powders and the salt, the purging and establishment of the hydrogen-argon atmosphere, the heating profile and the post-reaction washing steps that remove residual salts and recover the transformed crystals. The entire procedure takes approximately 37 hours and 20 minutes from start to finish, a time investment that is modest compared with the weeks of trial and error that often accompany attempts to grow metastable phases by conventional routes.

Equally important is the protocol’s emphasis on verification. Phase purity is not assumed; it is demonstrated. The authors prescribe a characterization workflow built on three complementary techniques. Raman spectroscopy probes the vibrational fingerprints of the lattice, which differ distinctly between the 2H and 1T′ arrangements. X-ray photoelectron spectroscopy examines the chemical states of the metal and chalcogen atoms, confirming that the transformation is complete and that no residual intercalants or decomposition products remain. X-ray diffraction provides the definitive structural verdict, revealing the characteristic peak positions of the 1T′ lattice and the absence of any detectable 2H-phase remnants. Together, these measurements give researchers the confidence that the material they are studying is genuinely the phase they intended to make.

The significance of gram-scale availability is difficult to overstate. Much of the early literature on metastable transition metal dichalcogenides relied on chemically exfoliated nanosheets produced through lithium intercalation, a method dating back to the 1980s that yields small, often defective flakes with variable phase content. Colloidal synthesis routes later offered better control but typically produced nanometer-scale particles rather than the large, well-ordered crystals needed for fundamental physics experiments and device fabrication. Hydrothermal and solution-phase approaches to 1T′ WSe2 and related compounds expanded the toolkit further, yet crystal size and phase purity remained persistent limitations. With crystals hundreds of micrometers wide available in gram batches, experiments that were previously impractical, such as building van der Waals heterostructures from 1T′ layers, performing detailed transport measurements, or loading industrial-scale electrocatalyst electrodes, become routine possibilities.

The applications that stand to benefit span an impressive range. In electrocatalysis, the metallic character of 1T′-phase materials makes them natural candidates for the hydrogen evolution reaction, the cathodic half of water splitting that underpins green hydrogen production. Previous work by members of the same team demonstrated that the phase of the support material dramatically influences how platinum catalysts grow and perform on molybdenum disulfide, achieving highly efficient hydrogen evolution when the metal deposited on metallic-phase surfaces. In electronics, 1T′ phases offer low-resistance contacts to semiconducting 2H layers, a strategy known as phase engineering that has been used to build better transistors. In photonics and sensing, 1T′ monolayers stabilized on gold nanowires have enabled ultrasensitive surface-enhanced Raman scattering detection. And in condensed matter physics, the metallic 1T′ phases of certain dichalcogenides host superconductivity, making high-purity crystals essential for studying emergent quantum phenomena.

The protocol also reflects a maturing view of what its authors call phase engineering of nanomaterials, a discipline that treats crystal phase as a design parameter on par with composition and dimensionality. Over the past decade, reviews in Chemical Reviews and Nature Reviews Chemistry have charted the rapid growth of this field, cataloguing unconventional phases across two-dimensional materials and the synthetic strategies developed to access them. The salt-assisted approach described here joins other recent innovations, including photoredox phase transformation driven by light, as part of a growing arsenal for navigating the energy landscapes of metastable matter. By codifying the method into a reproducible, step-by-step protocol, the team has effectively lowered the barrier to entry for laboratories worldwide.

For the broader materials community, the message is one of cautious optimism. Metastable phases have long been viewed as fragile curiosities, accessible only to specialists with finely tuned equipment and generous patience. A protocol that transforms shelf-stable commercial powders into gram quantities of phase-pure 1T′ crystals using a standard tube furnace and inexpensive salts suggests that these materials are ready to move from the margins of feasibility into the mainstream of research practice. Whether the next breakthrough comes in hydrogen catalysis, quantum devices or entirely unforeseen directions, the raw ingredients are now, quite literally, available by the gram.

Subject of Research: Salt-assisted synthesis of high phase-purity metastable 1T′-phase group VIB transition metal dichalcogenide crystals

Article Title: Salt-assisted synthesis of high phase-purity metastable 1T′-phase group VIB transition metal dichalcogenides

Article References: Zhai, W., Shi, Z., Tao, R., Li, Z., Dong, D., Tang, J., Wang, W., Wang, L., Yang, H., Zhai, L., Ruan, X., Wu, Y., Wang, J., Yao, Y., Zhao, C., He, Q., Lai, Z., & Zhang, H. (2026). Salt-assisted synthesis of high phase-purity metastable 1T′-phase group VIB transition metal dichalcogenides. Nature Protocols. https://doi.org/10.1038/s41596-026-01429-8

Image Credits: AI Generated

DOI: 10.1038/s41596-026-01429-8

Keywords: transition metal dichalcogenides, 1T′ phase, phase engineering, salt-assisted synthesis, metastable materials, two-dimensional materials, hydrogen evolution, electrocatalysis, MoS2, WS2, crystal growth, Nature Protocols

The fundamental process behind the team’s research is rooted in the unique characteristics of diarylethene crystals. When these crystals are exposed to ultraviolet (UV) light, they not only change color but also undergo significant morphological transformations. These shape changes add complexity to the methodologies employed in their manipulation and control. What makes this research particularly fascinating is how the team, consisting of graduate student Mami Isobe, lecturer Daichi Kitagawa, and Professor Seiya Kobatake, utilized sublimation to pattern these crystals on a substrate.

Sublimation is a phase transition process where a solid transforms directly into vapor without passing through the liquid phase. In the context of this research, powdered diarylethene crystals were sublimated onto a substrate, allowing the researchers to control the orientation and position of these crystals with exceptional precision. This control extends to the creation of functional structures, including minute crystals formed on convex shapes, thereby demonstrating the potential for intricate designs that can respond to environmental stimuli.

The team successfully produced convex structures with dimensions in the range of several microns in height and several microns in width, designed in the shape of straight lines and numerals ranging from 0 to 20. This design showcases not only the versatility of the method but also emphasizes how tailored configurations can yield unique photomechanical responses. The ability to design structures of various shapes signifies a significant advancement in the domain of material science, where form can dictate function.

One of the key expectations from this research is the application of the crystal patterning method to other sectors, particularly semiconductor materials and pharmaceuticals. Organic compounds similar to diarylethene have found a significant footing in these domains, and the insights gained from this study may lead to enhanced functionalities and novel applications. Graduate student Mami Isobe commented on the anticipation surrounding this method, reflecting a broader excitement about the possibilities it holds for future material developments.

Professor Kobatake’s remarks highlight the ambition to expand upon this research further. He expressed a desire to analyze how different sizes and shapes of the convex structures influence crystal growth and orientation. This exploration aims to unveil quantitative explanations of the underlying principles driving crystal pattern formation. Such insights could unlock new methodologies for crystal engineering, which is pivotal in various scientific fields.

The publication of these findings in the journal Small Methods signifies their relevance in the scientific community. It adds to the ongoing discourse in material science, especially regarding the fundamental interactions between light and matter at the microstructural level. The ability to manipulate such systems opens a door to numerous possibilities in research that extends beyond the current scope.

Moreover, the study showcases the potential of pattern formation techniques, paving the way for advancements in organic electronics and optoelectronics. As the field moves forward, the interest in photomechanical materials is likely to grow, especially with the increasing integration of smart materials in technology. These materials can provide intelligent responses to environmental changes, thus enhancing functionality in multiple applications.

The implications of this research are far-reaching. By controlling the orientation of diarylethene crystals at such a fine scale, researchers are opening up possibilities for the next generation of responsive materials. Such advancements are crucial in developing systems that require specific responses to stimuli such as light, heat, or electric fields. The work done by the Osaka Metropolitan University team provides a springboard for future investigations into the fundamental properties of materials and their applications in technology.

This research also invites the attention of industries looking to innovate in smart material technologies. As companies seek to enhance the capabilities of their devices and systems, understanding how molecular orientation impacts performance will be essential. The findings demonstrated by the Osaka Metropolitan University team will undoubtedly inspire further research aimed at harnessing the properties of crystals engineered for specific applications.

The imperative now for scientists and researchers in this domain is to comprehend the principles unveiled through this study and adapt them to various practical scenarios. The exploration of new materials and methods will drive much of the future technological landscape, particularly as we seek to integrate more sophisticated functions into everyday devices. As industries prepare for the adoption of these materials, a wave of innovation is likely on the horizon, driven by the very principles of molecular science explored in this research.

In summary, the work conducted by Osaka Metropolitan University represents a significant milestone in the field of photomechanical materials. Combining precision in crystal manipulation with the fundamental properties of diarylethene offers transformative possibilities for future materials science applications. Researchers and industries alike will benefit from understanding and utilizing the techniques developed through this pioneering study.

Subject of Research: Photomechanical materials, specifically diarylethene crystals; crystal patterning methods.
Article Title: Patterning of Photochromic Diarylethene Crystals by Sublimation for Morphological Controls.
News Publication Date: 19-Jan-2025.
Web References: Osaka Metropolitan University.
References: DOI.
Image Credits: Credit: Osaka Metropolitan University.
Keywords: Diarylethene, photomechanical materials, crystal patterning, sublimation method, semiconductor, pharmaceuticals, molecular structure, organic compounds, crystal growth, shape control, responsive materials, material science.