Physics

Normal mitochondrial function in stem cells is essential for effective bone regeneration, with mitochondrial complex IV (cytochrome c oxidase, CcO) playing a crucial role in sustaining electron transport chain activity and ATP synthesis. To address mitochondrial dysfunction associated with bone defects, we developed a dendritic mesoporous silica nanoparticle (DMSN)-based, CcO-mimetic nanozyme, named triphenylphosphonium (TPP)-DMSN-Fe/Cu. The nanozyme incorporated iron and copper single atoms to mimic the catalytic center of CcO and is modified with the mitochondria-targeting agent TPP. In vitro, TPP-DMSN-Fe/Cu nanozymes colocalized with mitochondria and enhanced mitochondrial function, effectively regulating cellular energy metabolism and promoting stem cell osteogenesis. In vivo, TPP-DMSN-Fe/Cu nanozymes resulted in significantly enhanced bone regeneration compared to the control, resulting in a 177% increase in bone volume and a 12% increase in mineral density at critical-sized bone defects in rats after 4 weeks of treatment. Taken together, these findings demonstrate that bioinspired, mitochondria-targeting TPP-DMSN-Fe/Cu nanozymes hold strong promise for accelerating bone regeneration via regulating cellular energy metabolism.

As a sustainable cathode material for sodium-ion batteries, Na₄MnFe(PO₄)₃ (NMFP) is prized for high theoretical operating voltage and cost-effectiveness. However, its practical electrochemical activity is notoriously poor, contradicting theoretical predictions. Here, we reveal that this inactivity stems primarily from Mott localization, driven by strong electron correlations within the high-spin 3d⁵ electronic configuration (t_2g ³e_g ²) of Mn²⁺ and Fe³⁺. This symmetric, half-filled state leads to pronounced charge localization, severely suppressing the intrinsic redox activity. To address this limitation, we devised a symmetry-breaking reconstruction strategy which reorganizes the spin ordering to promote electron delocalization and activates multiple redox couples (Mn⁴⁺/Mn³⁺, Mn³⁺/Mn²⁺, and Fe³⁺/Fe²⁺). More critically, induce a novel "Na2 dp Na1" migration path for Na⁺, with a remarkably lower energy barrier than those of conventional paths (0.39 vs. 0.98 eV). Consequently, the engineered Na₄Mn_0.5Fe_0.5Cr_0.5Ti_0.5(PO₄)₃ delivers 138.84 mAh g^-1 at 0.1C, which represents a 12.74-fold breakthrough over the pristine NMFP (10.9 mAh g^-1). Our findings elucidate symmetry-breaking as a critical route for activating Mott-localized states in polyanionic frameworks and establish a new paradigm for designing redox-active and sustainable cathode materials.

Polymer brush–gold nanoparticle (AuNP) hybrids have attracted considerable attention because the structural flexibility of polymer brushes complements the geometry-dependent plasmonic properties of AuNPs. When AuNPs are brought into close proximity, coupling between their localized surface plasmon resonance (LSPR) modes alters their electronic and optical characteristics, enabling the design of tunable plasmonic materials. Among various hybrid systems, precise control over the plasmonic responses of anisotropic AuNPs such as gold nanorods (AuNRs) remains challenging due to their increased structural and orientation-dependent complexity. Integrating AuNRs with polymer brushes offers additional tunability arising from the anisotropic shape of the nanorods, including orientation- and arrangement-dependent optical behavior. In this study, we demonstrate plasmonic modulation of AuNRs through structural regulation of poly(styrenesulfonate) (PSS) brushes. Drastic yet reversible orientation changes of AuNRs were achieved by compressing the PSS brushes using poor solvents. Furthermore, distinct plasmonic responses were observed depending on the assembled structures of tilted AuNRs within the brushes, reflecting different morphological states of the brush matrix under external stimuli. The brush–nanorod hybrids, which enable controllable orientation and assembly of AuNRs, exhibit tunable optical properties and hold promise for applications in colorimetric, optoelectronic, and plasmonic devices.

Surface engineering has produced remarkable advances in green- and red-light-emitting CsPbX3 (X = Br, I) nanocrystals. However, realizing efficient and stable blue-light emission from the higher-bandgap CsPbCl3 remains challenging due to its intrinsically defect-prone nature. This work computationally screens diverse X-type ligands to establish rational design principles for effectively passivating the trap-forming halide vacancies in CsPbCl3 nanocrystals. The multidentate anionic oxygen donors from phosphonic, sulfonic, and carboxylic acids passivate undercoordinated Pb sites with strong, stable binding. Out of these, electronic structure analyses identify 16 ligands that eliminate midgap defect states and restore a clean bandgap in CsPbCl3 nanocrystals. Such surface passivation not only removes trap states but also restores delocalized band edges, leading to the desired shortened radiative lifetimes. The fast radiative process suggests enhanced blue light emission from these passivated CsPbCl3 nanocrystals. Crucially, the effective passivation does not depend solely on the headgroup but is equally dictated by the molecular backbone and substituents. While the aliphatic chains in the ligand backbone promote a clean bandgap, π-conjugated aromatic moieties often introduce in-gap molecular states. Moreover, bulky ligand tails introduce steric hindrance, weakening adsorption energies despite an optimal binding headgroup. Overall, our findings outline a roadmap to achieve high-efficiency blue light emission from CsPbCl3 nanocrystals through strategic ligand engineering.

Atomic scale processes such as plasma-enhanced atomic layer deposition (ALD) and atomic layer etching (ALE) are vital to fabricate critical features in semiconductor devices that require excellent thickness control. Inert atomic plasmas are typically used for material removal by plasma ALE, whereas reactive molecular plasmas are used for synthesizing thin films by plasma ALD. To achieve accurate thickness control, high etch selectivity, and desirable material properties, accurate control of the ion energy is often important for these plasmas. However, controlling the ion energy by conventional radio-frequency sinusoidal waveform biasing results in a broad ion energy distribution. In this work, we investigate more precise ion energy control with tailored waveform biasing in atomic and molecular plasmas. A commercial remote plasma reactor was equipped with a prototype tailored voltage waveform generator for applying tailored bias waveforms, consisting of a positive voltage pulse and a negative linear voltage ramp. Various aspects of tailored bias waveforms including the voltage ramp rate, voltage pulse amplitude, voltage pulse duty cycle, and waveform repetition frequency were thoroughly investigated in terms of their influence on the ion flux-energy distribution functions of an inert atomic plasma (Ar). Moreover, it is demonstrated that this accurate ion energy control can be applied to reactive molecular plasmas (O2, Ar–H2, and N2) as well. This work serves as a guideline for the implementation of tailored waveform biasing in plasma-enhanced atomic scale processing.

Hybrid superconductor–semiconductor platforms can host subgap electronic excitations such as Andreev bound states; in topological regimes, a special zero-energy class, Majorana bound states, can emerge. Here we report the growth of epitaxial Al films by molecular-beam epitaxy on In0.75Ga0.25As under near-room-temperature substrate conditions. Using a combination of AFM/SEM, cross-sectional TEM, and in situ RHEED, we map how substrate temperature and Al deposition rate govern film morphology, continuity, and interface quality. We identify a growth window that yields continuous, superconducting Al films with an abrupt Al/In0.75Ga0.25As interface and no detectable indium interdiffusion. We further investigate the thermal stability of these films under in situ postgrowth heating and ex situ annealing following surface oxidation. For unoxidized Al, rapid surface diffusion triggers solid-state dewetting at approximately 165°C, resulting in the formation of {111}-faceted Al islands. In contrast, the presence of a native oxide largely suppresses dewetting, with failure occurring only locally at surface defects. Annealing above the indium melting point (156.6°C) induces significant In surface migration in both cases, leading either to localized interfacial In inclusions beneath Al agglomerates or to uniform surface contamination at sites of localized layer breakdown. Together, these results define growth and annealing conditions for thermally robust epitaxial Al on III–V semiconductors and provide practical guidance for fabricating high-quality superconductor–semiconductor hybrid platforms for quantum devices.

Carbon exhibits both a layered ground-state structure that produces two-dimensional (2D) nanosheets and a nonlayered diamond structure created under high pressure conditions. Motivated by this metastability relationship, we revisit the ground state structure of metal dichalcogenides that are known to have a nonlayered pyrite-type structure. Ultrathin films of pyrite-type ${\mathrm{ZnSe}}_{2}$ spontaneously transform into a layered phase. This phase is identified as a ground state, and the monolayer exhibits strong elastic anisotropy and a semiconducting bandgap larger than that of the pyrite phase by a factor of two. We demonstrate that a two-valued but directional potential energy surface exists along a Bain-like distortion path, hiding the layered ground state. This work implies that many 2D materials are hidden in nonlayered materials and connects 2D materials science with surface and high-pressure science.