Van der Waals Epitaxy Suppresses Thermal Rupture in Ultrathin Metals

 

Thin metallic films are indispensable for modern electronics. However, when their thickness is reduced to the nanoscale, they can exhibit instabilities similar to those observed in liquids. One of these is dewetting, which causes the film to spontaneously retract, leading to roughness, rupture and eventual loss of continuity. These thermal instabilities limit the operating temperature of thin metallic films to around 300 °C, making their integration into two-dimensional (2D) devices challenging.

To overcome this limitation, scientists from several institutions in China developed approximately 40-nm-thick gold films through van der Waals (vdW) epitaxy on graphene, using electron-beam evaporation. Unlike conventional epitaxy—in which material layers are deposited onto a substrate with an ordered surface, allowing their atoms to align precisely—vdW epitaxy relies on the weaker vdW interactions between the layers. This approach enables materials to grow on substrates with different crystal structures without necessarily forming direct chemical bonds between the two surfaces, owing to van der Waals forces.

The results show that vdW epitaxy on graphene promotes the formation of a more uniform microstructure, characterized by preferentially oriented (111) grains and low-energy grain boundaries. This microstructure changes the behavior of the film at high temperatures: it reduces the capillary forces that normally promote film rupture and facilitates self-healing processes that help maintain its continuity. As a result, the thin gold films remain continuous even at temperatures approaching 850 °C, far above the conventional limit of approximately 300 °C. In contrast, films produced using conventional methods exhibit a more heterogeneous microstructure and grain boundaries that are less favorable for thermal stability.

These findings show that controlling the microstructure through vdW epitaxy can be a strategy for significantly improving the thermal stability of ultrathin metallic films and facilitating their integration into 2D devices. This new methodology makes it possible to increase fabrication temperatures and times, enabling the production of next-generation devices with high-quality components.

For further information go to: nature communications

Programmable In Vivo Synthesis of Quantum Dots for Cancer Treatment

 

Quantum dots (QDs) are semiconductor nanoparticles capable of converting incident light into heat or re-emitting it at different wavelengths. In medicine, silver selenide QDs are promising because they are sensitive to near-infrared light (NIR-II), which can penetrate biological tissues with relative ease. However, when these nanoparticles are synthesized in vitro and injected into the body, they are rapidly cleared by the organism before reaching the tumor.

To overcome this obstacle, a team from Nankai University in China developed an innovative strategy: synthesizing quantum dots directly inside cancer cells.

To achieve this, the researchers developed a multifunctional platform known as a spatially hierarchical integrated nanosynthesizer, or SHINE, which delivers the two ingredients needed to form Ag₂Se quantum dots: silver and selenium.

SHINE integrates a ferritin-encapsulated silver source with a selenium source specifically synthesized for this purpose. Both are contained within a physically isolated, silica-coated nanocapsule that is sensitive to glutathione. The key to the system lies in its sequential release mechanism: the silica layer acts as a timer, regulating the precise moment at which the two precursors are released.

The mechanism is activated by the tumor itself. Cancer cells have a microenvironment rich in glutathione, an endogenous antioxidant. Glutathione degrades the SHINE coating, releasing selenium first and silver afterward. Within the malignant tissue, the two components spontaneously react to form nanocrystals as small as 3 nm.

In experiments using mouse models, fluorescence produced by laser excitation illuminated the tumors two hours after injection and remained stable for several days. In addition to serving as imaging agents for diagnostic purposes, the process provides an additional therapeutic function. The formation of the Ag₂Se particles depletes glutathione in the tumor, weakening its antioxidant defenses and increasing oxidative stress. When exposed to NIR-II infrared light, the quantum dots reach temperatures of 50–56 °C, destroying cancer cells through photothermal therapy. Tumor growth is reduced by more than 50%, while laser irradiation increases tumor inhibition to as much as 70%.

This advance demonstrates a strategy for the controlled production of functional nanomaterials within living organisms and opens the possibility of synthesizing diagnostic and therapeutic agents in situ, potentially avoiding the toxicity associated with administering prefabricated nanoparticles.

Angewandte Chemie International Edition

Synthesis and active assembly of DNA networks by biomolecular nanomachines

 

Cells use molecular nanomachines, such as enzymes and motor proteins, to perform work and actively control the organization of matter within them. In this context, microtubules—filamentous structures made of tubulin proteins, which are part of the cellular cytoskeleton—serve as tracks for the transport and organization of components within cells. Motor proteins, such as kinesins and dyneins, move along microtubules, transporting molecules in different directions: kinesins move cargo from the center of the cell toward the membrane, whereas dyneins move it in the opposite direction. These proteins use the chemical energy of ATP to power their movement.

These ATP-dependent processes are known as active assembly, and they allow the generation of structures and complex transformations that do not occur through conventional self-assembly. Understanding and reproducing active assembly represents an important challenge for nanoscience, as it could enable the fabrication of materials with high levels of organization and dynamic responses.

A team of researchers in Japan developed a strategy for fabricating molecular materials using one of these biomolecular nanomachines. They attached DNA strands to microtubules and increased the length of the strands using the enzyme DNA polymerase, which is responsible for replicating genetic material. They then placed the microtubules in a chamber on whose surface they anchored kinesins.

Using fluorescence microscopy, they observed that adding an ATP-containing solution induced the microtubules to move, causing the long DNA strands attached to them to stretch and intertwine, forming a two-dimensional network within a few minutes. Finally, they determined that the concentration of microtubules and the duration of the DNA synthesis altered the connectivity and complexity of the two-dimensional network.

The DNA–microtubule system provides a model for studying how forces generated by molecular motors can control the formation, connectivity, and organization of networks. Moreover, DNA sequences can be designed to program the interactions and connectivity of the network. This work proposes a strategy for fabricating biomaterials using active molecular nanomachines, paving the way for the development of bioinspired materials with adaptive and potentially self-healing properties.

For further information go to:

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Magnetic Removal of PFAS from Water — From Molecules to Microplastics

 

Per- and polyfluoroalkyl substances (PFAS) are synthetic compounds known as “forever chemicals,” found in many industrial and everyday products, including nonstick cookware, water- or stain-resistant textiles, food packaging, firefighting foams, laundry detergents, cosmetics, and others. They are among the most problematic contaminants today because of their resistance to chemical degradation by heat, water, and oil. They are extremely persistent and can accumulate in the environment as well as in living organisms, and their removal from water has proved to be very difficult.

In this study, a group of researchers in Germany reported a procedure for removing a broad spectrum of PFAS from water using functionalized magnetic nanoparticles.

Commercial superparamagnetic iron oxide nanoparticles (SPIONs) were used. These nanoparticles, consisting of γ-Fe₂O₃ and with an average diameter of 10.7 nm, were coated with a self-assembled monolayer of different phosphonic acid-based molecules capable of establishing hydrophobic and electrostatic interactions with PFAS. These noncovalent interactions promoted the adsorption of PFAS onto the nanoparticle surface, thereby enabling their removal from water.

The researchers focused on removing PFAS of different sizes, ranging from nanoplastics to fluorinated microplastics found in water used for washing clothes or containing cosmetics. They demonstrated that SPIONs can remove PFAS of different dimensions. Once the PFAS have been removed, the SPIONs can be reused.

This technology was also applied to water sources intended for human consumption, such as river water contaminated by runoff from land or textile washing. The study demonstrated that PFAS concentrations can be reduced by 87%, even below the limit established by German regulations of 100 ng per liter.

The proposed methodology demonstrated its ability to remove contaminants both at the molecular level and as microscopic particles. It highlights the potential of SPIONs as a sustainable platform for treating water containing complex mixtures of these contaminants.

For further information, see Materials Today doi:10.1016/j.mattod.2026.103471

In situ confinement of perovskite nanocrystals for efficient blue light-emitting LEDs

 

Metal halide perovskites have emerged as promising semiconductor materials for the fabrication of next-generation light-emitting diodes (LEDs) owing to their outstanding luminescent properties, tunable band gaps, high color purity, and low-cost fabrication processes. Perovskite LEDs (PeLEDs) have undergone rapid development, achieving external quantum efficiencies exceeding 30% for green and red emissions. 

However, for blue light emitters, the performance of PeLEDs has not yet matched that of organic LEDs (OLEDs) or metal chalcogenide quantum-dot LEDs (QD-LEDs). Blue PeLEDs still lag behind in terms of efficiency, operational lifetime, or both. Improving the performance of blue PeLEDs requires perovskite materials with both high crystallinity and nanoscale grain sizes.

High crystallinity with a low defect density suppresses non-radiative recombination losses and material degradation, whereas small grains enhance radiative efficiency through charge confinement and limited carrier diffusion. However, simultaneously achieving highly crystalline and nanoscale-confined perovskite nanocrystals via in situ synthesis on substrates remains a major challenge.

Researchers from China and the Netherlands have developed a simple in situ polymerization strategy to produce highly crystalline and size-confined Cs₀.₇EA₀.₃PbBr₃ perovskite nanocrystals (EA = ethylamine). The polymer network formed in situ from oligo(ethylene glycol) methyl ether acrylate (OEGA) dynamically restricts the excessive growth of nanocrystals during crystallization, reducing their size from more than 250 nm to 11 nm while achieving a high photoluminescence quantum yield of 83%.

Owing to its strong coordination affinity, OEGA interacts effectively with the perovskite precursors, moderating the rapid initial growth of perovskite seeds and thereby improving crystallinity. The fully confined nanocrystals exhibit a cubic phase at room temperature with reduced octahedral distortions, substantially mitigating non-radiative losses caused by electron-phonon coupling. Consequently, the resulting blue PeLEDs achieve an external quantum efficiency of 21.8% at 491 nm, placing them among the best-performing blue PeLEDs reported to date.

This work demonstrates a viable in situ nanocrystal confinement strategy that provides deeper insight into the role of ligand engineering in perovskite nanocrystal synthesis, thereby advancing the development of efficient blue PeLEDs and related optoelectronic technologies.

For further information go to Nature 

Synthesis of 2D diamonds

 

Diamond is renowned for its exceptional hardness, high thermal conductivity, and low chemical reactivity. However, it exhibits low fracture toughness and poor electrical conductivity compared with many metallic materials and nonmetallic inorganic solids. For decades, it has been theorized that two-dimensional (2D) diamond may exhibit enhanced properties relative to bulk diamond because of its two-dimensional nature, including greater mechanical strength, extraordinary carrier mobility, and a tunable band gap.

Researchers from institutions in China successfully synthesized high-quality two-dimensional diamonds by heating graphene layers with a near-infrared (NIR) laser. They employed a high-pressure, high-temperature (HPHT) process to irreversibly transform graphene layers into 2D diamond. A polished rhenium (Re) metal foil was used as both the substrate and the laser-energy absorber to facilitate the heating process. The researchers succeeded in synthesizing 2D diamonds with thicknesses ranging from the equivalent of a graphene bilayer (~1 nm) to several hundred nanometers.

The 2D diamonds were characterized by Raman spectroscopy, whose spectra exhibited a well-defined characteristic peak at 1332 cm⁻¹ with a full width at half maximum (FWHM) of approximately 3.6 cm⁻¹, indicating their high crystalline quality. Photoluminescence measurements demonstrated that these diamonds are excellent candidates for quantum computing and sensing applications. 

Furthermore, the researchers found that the band gap can be tuned within the range of 1.4 to 1.9 eV, depending on the proportion of sp³ species in the sample, which varied from 71.3% to 89.9%. Finally, they found that the diamonds remain stable at temperatures above 1000 °C.

This study demonstrates the successful synthesis of 2D diamond and reveals properties that differ from those of bulk (3D) diamond. The results indicate that 2D diamonds possess significant potential for applications in nanoelectronics and optoelectronics.

For further information go to nature communications

Competitive reactivities determine the size and composition of multimetallic nanocrystals

 

Multimetallic nanocrystals (NCs) have attracted considerable attention due to their physical, chemical, and catalytic properties, which often surpass those of their monometallic counterparts. The distinctive properties of NCs are determined by the synergistic interactions among their constituent metals.

Synthesizing these materials with precise control over size and composition remains a major challenge because of the differences in the reactivities of the metal precursors. Owing to these differences, one would expect that increasing the number of metal precursors would enhance the formation of heterogeneous products (mixtures of particles with different sizes and compositions).

However, a multinational team of researchers demonstrated a counterintuitive effect in the synthesis of multimetallic nanocrystals: differences in the reactivities of metal precursors can actually promote the formation of highly uniform multimetallic nanocrystals.

Ru nanoparticles (≈ 4.5 nm) and precursor solutions of Fe, Co, Ni, and Cu were used as seeds. Upon introducing five metals (RuFeCoNiCu), a uniform product was obtained: pentametallic nanocrystals of ≈ 14.1 ± 1.4 nm with a narrow size distribution. This effect persisted even when the seed size, precursor ratios, and additional metals (Cr, In) were varied.

The mechanism underlying this remarkable process was elucidated through time-lapse analysis of intermediate products and tomography. As shown in the Figure, the formation of pentametallic nanocrystals proceeded through three distinct stages: (i) predominant reduction of Cu on previously formed Ru seeds, (ii) onset of Co, Ni, and Fe reduction accompanied by partial surface-layer formation, and (iii) complete reduction and integration of all constituent metals into fully formed RuFeCoNiCu nanocrystals.

When the pentametallic nanocrystals supported on Al2O3 were used as catalysts, they exhibited a reaction rate more than four times higher than that of monometallic Ru in ammonia decomposition (NH3 → N2 + 3H2), while maintaining comparable activation energy and thermal stability.

This work proposes a new principle for the design of complex multimetallic nanocrystals: rather than suppressing the competition among metal precursor reactivities, it can be harnessed. This finding leads the way toward libraries of nanomaterials with unique synergistic properties for applications such as catalysis and sustainable energy technologies.

For further information go to: Science