ACS Materials Letters最新文献

Single-crystal metal-halide perovskites hold significant promise for optoelectronic applications due to their tunable physical properties and the possibility of low-cost, low-temperature synthesis. Compared to their polycrystalline counterparts, they exhibit reduced defect densities and enhanced stability. Their intrinsically soft lattice facilitates integration with conventional semiconductors via heterostructures. However, their high ionic mobility can lead to interdiffusion processes that compromise the integrity of adjacent layers, making the formation of well-defined interfaces a critical challenge for device optimization. Here, we exploit the temperature dependence of the perovskite growth kinetics to demonstrate a one-pot, space-confined growth method for synthesizing vertical 2D/3D lead-halide perovskite heterostructures in single-crystal form. The process leverages differences in precursor solubility to drive sequential crystallization and create well-defined interfaces. Structural and optical analyses confirm the formation of stable, phase-separated heterostructures, which are promising for optoelectronic applications.

In this work, we present a Δ-learning approach for predicting the eigenvalues calculated with the hybrid functional HSE06 (ϵ_nk^HSE) for a set of metal and nitrogen doped graphene catalysts (MNCs) from Perdew-Burke-Ernzerhof (PBE) inputs. The model presented here incorporates electronic scalar features along with structural information in a graph neural network (GNN). In particular, the PBE eigenvalues for different bands and k-points and orbital-resolved projectors are combined with the applied potential as node-level features along with structural information within the Atomistic Line Graph Neural Network (ALIGNN) architecture. These features enable flexibility for systems with electrified interfaces, such as in electrocatalysts and achieves mean absolute error (MAE) of less than 0.1 eV. The machine learning model reported here achieves a strong generalization to left-out adsorbates (MAE = 0.074 eV) and leave-one-chemical-space-out (MAE = 0.08 eV) and completely left-out metals (MAE = 0.072 eV), confirming the robustness of the machine learning (ML) model in predicting ϵ_nk^HSE.

Memristors that can be used to simulate biosynaptic functions offer great potential for energy-efficient neuromorphic computing. Ti₃C₂ exhibits excellent electrical conductivity and has been investigated for its application in memristor-based artificial synapse. However, despite the crucial importance of a high switching ratio for minimizing data read/write errors, current research on Ti₃C₂-based memristors with high switching ratios remains limited in memristor-based neuromorphic computing systems. Here, we synthesized a Ti₃C₂:V₂O₅ nanocomposite by introducing V₂O₅ nanowires into a Ti₃C₂ matrix and fabricated a vertical memristor based on this composite, which exhibits excellent resistive switching characteristics including a high switching ratio of 10⁶ and an average set power as low as 127 nW. The memristor effectively simulated various biological synaptic functions, the light and dark adaptation behavior of the human retina and the changes in human body water content at different temperatures, providing insights for applications in the field of neuromorphic computing.

Size-dependent electronic, magnetic, and optical behavior suggests that metal–organic frameworks become softer materials as their particle sizes decrease, but direct evidence is lacking. Here, we report variable-temperature powder X-ray diffraction data of Fe(1,2,3-triazolate)₂ particles that offer crystallographic insight into size-dependent bond flexibility. Rietveld refinement reveals size-dependent positive thermal expansion upon downsizing the crystalline domains from 178 to 9 nm, with a 6-fold increase from 16 MK^–1 to 96 MK^–1. This behavior occurs in tandem with size-dependent elongation of metal–ligand bonds and increasing thermal displacement parameters, consistent with pronounced metal-linker bond lability. We propose that these effects, as well as size-dependent annealing of crystallite sizes, originate from the high charge density and surface stress of smaller particles. Taken together, these results provide structural evidence that size reduction serves as a synthetic route to controlling the dynamic response of materials to external stimuli.

Self-healing in covalently bonded matter remains challenging due to the high energy barrier for bond reconstruction. Nanotwinned diamond composites (ntDCs) have demonstrated room-temperature fracture self-healing, while the atomic mechanisms of cracking and self-healing remain unclear. Using atomistic simulations, we uncovered the mechanisms of amorphization-mediated self-healing of fractured ntDCs. Mechanical mismatch at crack-boundary interfaces induced local disorder, forming high-energy amorphous clusters with mixed hybridizations. These amorphous clusters act as sites for self-healing, where the disordered environment promotes a preferential sp²-to-sp³ transition. Furthermore, the simulated pressure-driven self-healing of fractured ntDCs suggested that the posthealing fracture mode is highly dependent on the pressure. Higher pressures facilitate the formation of continuous diamond grains across the fractured interfaces, enhancing the mechanical integrity and recovery efficiency. Our findings provide molecular insights into the self-healing of covalent materials and offer theoretical support for the fabrication of large-sized noncrystalline carbons.

We obtained a water-soluble clusteroluminescence (CL) copolymer comprising a photo-responsive aromatic luminophore. The copolymer emits concentration- and excitation-dependent visible light luminescence. After photodimerization crosslinking of the photo-responsive units, a hierarchal clustered domain with densely confined space induces a fluorescence red shift via through-space interactions. In its film-forming solid state, the polymer emits high-quantum-yield fluorescence-enhanced white light. The emission is almost pure white (CIE coordinates x = 0.30, y = 0.33) and derives from the intense overlapped short- and long-wavelength CL resulting from changes in the photodimerization degree. This is the first white-light emission coating with external photo-responsiveness produced by an environmentally benign and water-based process. We present a method of efficiently increasing fluorescence by regulating the hierarchical structures of the CL polymer and restricting intermolecular motion. The polymer will be useful for thinner flexible light displays and information encryption.

Vinylene-linked covalent organic frameworks (COFs) have attracted widespread interest as photocatalysts, largely due to their remarkable chemical stability and extensive π-conjugation. Nevertheless, the development of innovative monomers for the construction of vinylene-linked COFs with adjustable electronic properties remains at an early stage. To tackle this issue, a tetratopic monomer incorporating a thieno[3,2-b]thiophene backbone was rationally designed and subsequently polymerized with terephthalaldehyde and 4,4′-biphenyldicarboxaldehyde, affording two vinylene-linked COFs (PTT-BDA and PTT-BPA) that exhibited high crystallinity, outstanding stability, and pronounced π-electron delocalization. More significantly, tuning the π-conjugation length within the COF frameworks enabled the optimization of their semiconducting characteristics. Owing to its extended π-conjugation, PTT-BPA exhibited excellent semiconducting properties, which endowed it with outstanding photocatalytic activity. This study not only expands the library of vinylene-linked COFs but also introduces a straightforward strategy to modulate their semiconducting properties by adjusting the π-conjugation length within the framework structure.

Herein we report the first observation of magneto-chiral dichroism (MChD) on paramagnetic nanoparticles. Magnetic nanoparticles based on cobalt(II) were synthesized in the presence of enantiopure (d or l)-aspartic acid. The chiral ligands coordinate the Co²⁺ ions at the nanoparticle surface inducing a strong natural circular dichroism (g_NCD = 10^–2) for the ⁴T₁(⁴P) ← ⁴T₁(⁴F) electronic transitions of the Co²⁺ ion in octahedral sites. Magneto-chiral dichroism measurements reveal an unambiguous MChD signal at low temperatures for the same transitions, which represent the first evidence of the phenomenon for functionalized nanoparticles. These results demonstrate the possibility of detecting the magneto-optical properties of a nanomaterial without the need for light polarization and open alternative perspectives in magnetic sensing, optical devices, and biomedical fields.

The polyol process, developed over the past four decades, has emerged as a versatile soft chemical route for the synthesis of metal nanoparticles with broad technological relevance. It offers several advantages, including low cost, operational simplicity, and proven scalability for industrial application. Among its key uses, polyol-assisted nanoparticles play a critical role in selective catalytic hydrogenation in the petrochemical and fine chemical industries. Nevertheless, synthesis becomes more challenging when substrates possess multiple functional groups, requiring high selectivity. In this context, palladium nanoparticles prepared via the polyol method have demonstrated notable efficiency in hydrogenation reactions. This review highlights the polyol-mediated synthesis of Pd nanoparticles, considering first-row transition metals to provide a broader perspective. In particular, biphasic systems that enable efficient phase separation and recovery have been broadly demonstrated. Overall, this review emphasizes the potential of polyol-derived nanoparticles in selective organic transformations, particularly hydrogenation processes.

Since breast cancer often occurs in the upper quadrant, the use of the second near-infrared (NIR-II) light that penetrates deeper tissues and matches phototherapy agents is a prerequisite for true phototherapy treatment. NIR-II absorbing organic functional dye is an ideal choice for effective antitumor phototherapy. Herein, we developed a series of aza-BODIPYs (NN-azaBDPs) with 1,4-dimethyl-1,2,3,4-tetrahydroquinoxaline (NN) as an ultra electron-donating group at 3,5-sites. CF₃-NN bearing the D–A–A′ system absorbs at 990 nm and emits at 1240 nm in the NIR-II region. CF₃-NN nanoparticles have fluorescence imaging capabilities in the NIR-II region and significant photothermal conversion efficiency (77.8%), and the twisted structure of the NN segment creates a basis for the generation of reactive oxygen species. NN-azaBDPs provide a platform for photothermal-photodynamic combined therapy for breast cancer.