Electron-Delocalization Across High Surface Entropy Sub-1 nm Nanobelts Toward Enhanced Electrocatalytic Urea Oxidation.

Integration of inherently incompatible elements into a single sublattice, resulting in the formation of monophasic metal oxide, holds great scientific promise; it unveils that the overlooked surface entropy in subnanometer materials can thermodynamically facilitate the formation of homogeneous single-phase structures. Here a facile approach is proposed for synthesizing multimetallic oxide subnanometer nanobelts (MMO-PMA SNBs) by harnessing the potential of phosphomolybdic acid (PMA) clusters to capture inorganic nuclei and inhibiting their subsequent growth in solvothermal reactions. Experimental and theoretical analyses show that PMA in MMO-PMA SNBs not only aids subnanometer structure formation but also induces in situ modifications to catalytic sites. The electron transfer from PMA, coupled with the loss of elemental identity of transition metals, leads to electron delocalization, jointly activating the reaction sites. The unique structure makes pentametallic oxide (PMO-PMA SNBs) achieve a current density of 10 mA cm-2 at a low potential of 1.34 V and remain stable for 24 h at 10 mA cm-2 on urea oxidation reaction (UOR). The exceptional UOR catalytic activity suggests a potential for utilizing multimetallic subnanometer nanostructures in energy conversion and environmental remediation.

Unraveling the Unique Strong Metal-Support Interaction in Titanium Dioxide Supported Platinum Clusters for the Hydrogen Evolution Reaction.

Strong metal-support interaction (SMSI) is crucial to modulating the nature of metal species, yet the SMSI behaviors of sub-nanometer metal clusters remain unknown due to the difficulties in constructing SMSI at cluster scale. Herein, we achieve the successful construction of the SMSI between Pt clusters and amorphous TiO2 nanosheets by vacuum annealing, which requires a relatively low temperature that avoids the aggregation of small clusters. In situ scanning transmission electron microscopy observation is employed to explore the SMSI behaviors, and the results reveal the dynamic rearrangement of Pt atoms upon annealing for the first time. The originally disordered Pt atoms become ordered as the crystallizing of the amorphous TiO2 support, forming an epitaxial interface between Pt and TiO2. Such a SMSI state can remain stable in oxidation environment even at 400 °C. Further investigations prove that the electron transfer from TiO2 to Pt occupies the Pt 5d orbitals, which is responsible for the disappeared CO adsorption ability of Pt/TiO2 after forming SMSI. This work not only opens a new avenue for constructing SMSI at cluster scale but also provides in-depth understanding on the unique SMSI behavior, which would stimulate the development of supported metal clusters for catalysis applications.

Regulating Li-Ion Transport through Ultrathin Molecular Membrane to Enable High-Performance All-Solid-State-Battery.

Solid-state lithium metal batteries with garnet-type electrolyte provide several advantages over conventional lithium-ion batteries, especially for safety and energy density. However, a few grand challenges such as the propagation of Li dendrites, poor interfacial contact between the solid electrolyte and the electrodes, and formation of lithium carbonate during ambient exposure over the solid-state electrolyte prevent the viability of such batteries. Herein, an ultrathin sub-nanometer porous carbon nanomembrane (CNM) is employed on the surface of solid-state electrolyte (SSE) that increases the adhesion of SSE with electrodes, prevents lithium carbonate formation over the surface, regulates the flow of Li-ions, and blocks any electronic leakage. The sub-nanometer scale pores in CNM allow rapid permeation of Li-ions across the electrode-electrolyte interface without the presence of any liquid medium. Additionally, CNM suppresses the propagation of Li dendrites by over sevenfold up to a current density of 0.7 mA cm-2 and enables the cycling of all-solid-state batteries at low stack pressure of 2 MPa using LiFePO4 cathode and Li metal anode. The CNM provides chemical stability to the solid electrolyte for over 4 weeks of ambient exposure with less than a 4% increase in surface impurities.

Non-planar Nest-like [Fe2 S2 ] Cluster Sites for Efficient Oxygen Reduction Catalysis.

Metal-nitrogen-carbon catalysts, as promising alternative to platinum-based catalysts for oxygen reduction reaction (ORR), are still highly expected to achieve better performance by modulating the composition and spatial structure of active site. Herein, we constructed the non-planar nest-like [Fe2 S2 ] cluster sites in N-doped carbon plane. Adjacent double Fe atoms effectively weaken the O-O bond by forming a peroxide bridge-like adsorption configuration, and the introduction of S atoms breaks the planar coordination of Fe resulting in greater structural deformation tension, lower spin state, and downward shifted Fe d-band center, which together facilitate the release of OH* intermediate. Hence, the non-planar [Fe2 S2 ] cluster catalyst, with a half-wave potential of 0.92 V, displays superior ORR activity than that of planar [FeN4 ] or [Fe2 N6 ]. This work provides insights into the co-regulation of atomic composition and spatial configuration for efficient oxygen reduction catalysis.

Sub-Nanometer Confined Ions and Solvent Molecules Intercalation Capacitance in Microslits of 2D Materials.

The ion intercalation behavior in 2D materials is widely applied in energy storage, electrocatalysis, and desalination. However, the detailed effect of ions on the performance, combining the influence of interlayer force and the change of solvent shell, is far less well understood. Here the solvated alkali metal ions with different sizes are intercalated into the lattice of 2D materials with different spacings (Ti3 C2 Tx , δ-MnO2 , and reduced graphene oxide) to construct the intercalation model related with sub-nanometer confined ions and solvent molecules to further understand the intercalation capacitance. Based on electrochemical methods and density functional theory calculation, the ions lose the electrostatic shielding solvent shell or shorten the distance between the layers, resulting in a significant increase in capacitance. It is found that the intercalation capacitance arises from the diffusion of solvated ions and is controlled by quantum and electrochemical capacitance for desolvated ions. This effect of solvation structure on performance can be applied in a variety of electrochemical interface studies and provides a new research view for energy storage mechanisms.

Multifunctionalized Gold Sub-Nanometer Particles for Sensitizing Radiotherapy against Glioblastoma.

Glioblastoma is the most common lethal malignant intracranial tumor with a low 5-year survival rate. Currently, the maximal safe surgical resection, followed by high-dose radiotherapy (RT), is a standard treatment for glioblastoma. However, high-dose radiation to the brain is associated with brain injury and results in a high fatality rate. Here, integrated pharmaceutics (named D-iGSNPs) composed of gold sub-nanometer particles (GSNPs), blood-brain barrier (BBB) penetration peptide iRGD, and cell cycle regulator α-difluoromethylornithine is designed. In both simulated BBB and orthotopic murine GL261 glioblastoma models, D-iGSNPs are proved to have a beneficial effect on the BBB penetration and tumor targeting. Meanwhile, data from cell and animal experiments reveal that D-iGSNPs are able to sensitize RT. More importantly, the synergy of D-iGSNPs with low-dose RT can exhibit an almost equal therapeutic effect with that of high-dose RT. This study demonstrates the therapeutic advantages of D-iGSNPs in boosting RT, and may provide a facile approach to update the current treatment of glioblastoma.

Sub-Nanometer Thick Wafer-Size NiO Films with Room-Temperature Ferromagnetic Behavior.

Adding ferromagnetism into semiconductors attracts much attentions due to its potential usage of magnetic spins in novel devices, such as spin field-effect transistors. However, it remains challenging to stabilize their ferromagnetism above room temperature. Here we introduce an atomic chemical-solution strategy to grow wafer-size NiO thin films with controllable thickness down to sub-nanometer scale (0.92 nm) for the first time. Surface lattice defects break the magnetic symmetry of NiO and produce surface ferromagnetic behaviors. Our sub-nanometric NiO thin film exhibits the highest reported room-temperature ferromagnetic behavior with a saturation magnetization of 157 emu/cc and coercivity of 418 Oe. Attributed to wafer size, the easily-transferred NiO thin film is further verified in a magnetoresistance device. Our work provides a sub-nanometric platform to produce wafer-size ferromagnetic NiO thin films as atomic layer magnetic units in future transparent magnetoelectric devices.

Synthesis of Highly Active Sub-Nanometer Pt@Rh Core-Shell Nanocatalyst via a Photochemical Route: Porous Titania Nanoplates as a Superior Photoactive Support.

Sub-nanometer Pt@Rh nanoparticles highly dispersed on MIL-125-derived porous TiO2 nanoplates are successfully prepared for the first time by a photochemical route, where the porous TiO2 nanoplates with a relatively high specific surface area play a dual role as both effective photoreductant and catalyst support. The resulting Pt@Rh/p-TiO2 can be utilized as a highly active catalyst.

Sub-1 nm Nickel Molybdate Nanowires as Building Blocks of Flexible Paper and Electrochemical Catalyst for Water Oxidation.

Sub-1 nm, extremely long nickel molybdate nanowires are synthesized based on a good/poor solvent system. The ultrathin nanowires can be hierarchically assembled into flexible, free-standing films with good mechanical properties. Compared with the large-size counterpart, nickel molybdate ultrathin nanowires display promising oxygen evolution reaction catalytic performance derived from the ultrathin feature.

Sub-2 nm Microstrained High-Entropy-Alloy Nanoparticles Boost Hydrogen Electrocatalysis.

High-entropy alloys (HEAs) confine multifarious elements into the same lattice, leading to intense lattice distortion effect. The lattice distortion tends to induce local microstrain at atomic level and thus affect surface adsorptions toward different adsorbates in various electrocatalytic reactions, yet remains unexplored. Herein, this work reports a class of sub-2 nm IrRuRhMoW HEA nanoparticles (NPs) with distinct local microstrain induced by lattice distortion for boosting alkaline hydrogen oxidation (HOR) and evolution reactions (HER). This work demonstrates that the distortion-rich HEA catalysts with optimized electronic structure can downshift the d-band center and generate uncoordinated oxygen sites to enhance the surface oxophilicity. As a result, the IrRuRhMoW HEA NPs show a remarkable HOR kinetic current density of 8.09 mA µg-1 PGM at 50 mV versus RHE, 8.89, 22.47 times higher than those of IrRuRh NPs without internal strain and commercial Pt/C, respectively, which is the best value among all the reported non-Pt based catalysts. IrRuRhMoW HEA NPs also display great HER performances with a turnover frequency (TOF) value of 5.93 H2 s-1 at 70 mV versus RHE, 4.6-fold higher than that of Pt/C catalyst, exceeding most noble metal-based catalysts. Experimental characterizations and theoretical studies collectively confirm that weakened hydrogen (Had) and enhanced hydroxyl (OHad) adsorption are achieved by simultaneously modulating the hydrogen adsorption binding energy and surface oxophilicity originated from intensified ligand effect and microstrain effect over IrRuRhMoW HEA NPs, which guarantees the remarkable performances toward HOR/HER.

Monolithic DNApatite: An Elastic Apatite with Sub-Nanometer Scale Organo-Inorganic Structures.

Hydroxyapatite (HA) exhibits outstanding biocompatibility, bioactivity, osteoconductivity, and natural anti-inflammatory properties. Pure HA, ion-doped HA, and HA-polymer composites are investigated, but critical limitations such as brittleness remain; numerous efforts are being made to address them. Herein, the novel self-crystallization of a polymeric single-stranded deoxyribonucleic acid (ssDNA) without additional phosphate ions for synthesizing deoxyribonucleic apatite (DNApatite) is presented. The synthesized DNApatite, DNA1Ca2.2(PO4)1.3OH2.1, has a repetitive dual phase of inorganic HA crystals and amorphous organic ssDNA at the sub-nm scale, forming nanorods. Its mechanical properties, including toughness and elasticity, are significantly enhanced compared with those of HA nanorod, with a Young's modulus similar to that of natural bone.

Engineering Sub-Nanometer Hafnia-Based Ferroelectrics to Break the Scaling Relation for High-Efficiency Piezocatalytic Water Splitting.

Reversible control of ferroelectric polarization is essential to overcome the heterocatalytic kinetic limitation. This can be achieved by creating a surface with switchable electron density; however, owing to the rigidity of traditional ferroelectric oxides, achieving polarization reversal in piezocatalytic processes remains challenging. Herein, sub-nanometer-sized Hf0.5 Zr0.5 O2 (HZO) nanowires with a polymer-like flexibility are synthesized. Oxygen K-edge X-ray absorption spectroscopy and negative spherical aberration-corrected transmission electron microscopy reveal an orthorhombic (Pca21 ) ferroelectric phase of the HZO sub-nanometer wires (SNWs). The ferroelectric polarization of the flexible HZO SNWs can be easily switched by slight external vibration, resulting in dynamic modulation of the binding energy of adsorbates and thus breaking the "scaling relationship" during piezocatalysis. Consequently, the as-synthesized ultrathin HZO nanowires display superb water-splitting activity, with H2 production rate of 25687 µmol g-1  h-1 under 40 kHz ultrasonic vibration, which is 235 and 41 times higher than those of non-ferroelectric hafnium oxides and rigid BaTiO3 nanoparticles, respectively. More strikingly, the hydrogen production rates can reach 5.2 µmol g-1  h-1 by addition of stirring exclusively.

Arming Ru with Oxygen-Vacancy-Enriched RuO2 Sub-Nanometer Skin Activates Superior Bifunctionality for pH-Universal Overall Water Splitting.

Water electrolysis has been expected to assimilate the renewable yet intermediate energy-derived electricity for green H2 production. However, current benchmark anodic catalysts of Ir/Ru-based compounds suffer severely from poor dissolution resistance. Herein, an effective modification strategy is proposed by arming a sub-nanometer RuO2 skin with abundant oxygen vacancies to the interconnected Ru clusters/carbon hybrid microsheet (denoted as Ru@V-RuO2 /C HMS), which can not only inherit the high hydrogen evolution reaction (HER) activity of the Ru, but more importantly, activate the superior activity toward the oxygen evolution reaction (OER) in both acid and alkaline conditions. Outstandingly, it can achieve an ultralow overpotential of 176/201 mV for OER and 46/6 mV for the HER to reach 10 mA cm-2 in acidic and alkaline solution, respectively. Inspiringly, the overall water splitting can be driven with an ultrasmall cell voltage of 1.467/1.437 V for 10 mA cm-2 in 0.5 m H2 SO4 /1.0 m KOH, respectively. Density functional theory calculations reveal that armoring the oxygen-vacancy-enriched RuO2 exoskeleton can cooperatively alter the interfacial electronic structure and make the adsorption behavior of hydrogen and oxygen intermediates much close to the ideal level, thus simultaneously speeding up the hydrogen evolution kinetics and decreasing the energy barrier of oxygen release.

Polishing Approaches at Atomic and Close-to-Atomic Scale.

Roughness down to atomic and close-to-atomic scale is receiving an increasing attention in recent studies of manufacturing development, which can be realized by high-precision polishing processes. This review presents polishing approaches at atomic and close-to-atomic scale on planar and curved surfaces, including chemical mechanical polishing, plasma-assisted polishing, catalyst-referred etching, bonnet polishing, elastic emission machining, ion beam figuring, magnetorheological finishing, and fluid jet polishing. These polishing approaches are discussed in detail in terms of removal mechanisms, polishing systems, and industrial applications. The authors also offer perspectives for future studies to address existing and potential challenges and promote technological progress.

Spin Selectivity in Chiral Hybrid Cobalt Halide Films with Ultrasmooth Surface.

Introducing chirality into low-dimensional hybrid organic-inorganic halides (HOIHs) creates brand-new opportunities for HOIHs in spintronics and spin-related optoelectronics owing to chirality-induced spin selectivity (CISS). However, preparing smooth films of low-dimensional HOIHs with small roughness is still a great challenge due to the hybrid and complex crystal structure, which severely inhibits their applications in spintronic devices. Exploring new lead-free chiral HOIHs with both efficient spin selectivity and excellent film quality is urgently desired. Here, cobalt-based chiral metal halide crystals (R/S-NEA)2 CoCl4 constructed by 0D [CoCl4 ] tetrahedrons and 1-(1-naphtyl)ethylamine (NEA) are synthesized. The orderly configuration of NEA molecules stabilized by noncovalent CH···π interaction endows (NEA)2 CoCl4 with good film-forming ability. (NEA)2 CoCl4 films exhibit strong chiroptical activity (gCD  ≈ 0.05) and significant spin-polarized transport (CISS efficiency up to 90%). Furthermore, ultrasmooth films (roughness ∼ 0.3 nm) with enhanced crystallinity can be achieved by incorporating tiny amount tris(8-oxoquinoline)aluminum that has analogous conjugated structure to NEA. The realization of highly efficient spin selectivity and sub-nanometer roughness in lead-free chiral halides can boost the practical process of low-dimensional HOIHs in spintronics and other fields.

Sub-Nanometer Accuracy Combination Processing Technology for Nickel-Phosphorus Modified Surfaces Based on Aluminum Reflector Mirror.

The surface of metal mirrors is often polished by electroless coating with a Ni-P modified layer after single-point diamond turning. In practice, however, improvements in mirror quality are closely related to the polishing environment, polishing medium, and polishing force. If not adequately controlled, processing defects such as visible scratches can lead to the deterioration of surface roughness. Based on the Ni-P modified surface of a metal reflector mirror, this study optimizes the configuration of magnetorheological figuring (MRF) fluid and polishing process parameters so that MRF high-efficiency surface modification can be realized and the scratch problem can be resolved. The processing method of a high-performance metal mirror is developed by studying the high-efficiency and high-precision processing technology based on small head smoothing. The surface roughness achieved by the proposed method was better than Ra = 0.39 nm. The ultrasonic cleaning process effectively improved the surface roughness after processing. According to the combined processing technology developed in this study, the modified layer of the parabolic mirror with a diameter of 370 mm was processed, and the surface quality was increased from RMS = 338.684 nm to RMS = 21.267 nm.

Enhancing the Spin-Orbit Torque Efficiency by the Insertion of a Sub-nanometer ß-W Layer.

Spin-orbit torque (SOT) efficiency is one of the key issues of spintronics. However, enhancing the SOT efficiency is usually limited by the positive correlation between resistivity and the spin Hall ratio, where a high resistivity often accompanies a large spin Hall ratio. Here, we demonstrate that sub-nanometer ß-W intercalation has a considerable impact on the SOT efficiency in α-W (6 nm)/Co (8 nm)/Pt (3 nm) samples. The damping-like SOT efficiency per unit current density, ξDLj, of α-W (5.7 nm)/ß-W (0.3 nm)/Co (8 nm)/Pt (3 nm) shows a ∼ 296% enhancement compared to that of the α-W/Co/Pt system. Meanwhile, a resistivity similar to that of α-W and the spin Hall ratio larger than ß-W induce a giant damping-like SOT efficiency per applied electric field, ξDLE, which is about 12.1 times larger than that of ß-W. Our findings will benefit the SOT devices by reducing energy consumption.

Sub-Nanometer Electron Beam Phase Patterning in 2D Materials.

Phase patterning in polymorphic two-dimensional (2D) materials offers diverse properties that extend beyond what their pristine structures can achieve. If precisely controllable, phase transitions can bring exciting new applications for nanometer-scale devices and ultra-large-scale integrations. Here, the focused electron beam is capable of triggering the phase transition from the semiconducting T'' phase to metallic T' and T phases in 2D rhenium disulfide (ReS2 ) and rhenium diselenide (ReSe2 ) monolayers, rendering ultra-precise phase patterning technique even in sub-nanometer scale is found. Based on knock-on effects and strain analysis, the phase transition mechanism on the created atomic vacancies and the introduced substantial in-plane compressive strain in 2D layers are clarified. This in situ high-resolution scanning transmission electron microscopy (STEM) and in situ electrical characterizations agree well with the density functional theory (DFT) calculation results for the atomic structures, electronic properties, and phase transition mechanisms. Grain boundary engineering and electrical contact engineering in 2D are thus developed based on this patterning technique. The patterning method exhibits great potential in ultra-precise electron beam lithography as a scalable top-down manufacturing method for future atomic-scale devices.

Highly efficient sub-nanometer RuxCuyP2 nanoclusters designed for hydrogen evolution under alkaline media.

Design of highly active and stable non-precious electrocatalysts towards hydrogen evolution reaction (HER) is a hot research topic in low cost, clean and sustainable hydrogen energy field, yet remaining the important challenge caused by the sluggish reaction kinetics for water-alkali electrolyzers. Herein, a robust electrocatalyst is proposed by designing a novel sub-nanometer of copper and ruthenium bimetallic phosphide nanoclusters (RuxCuyP2) supported on a graphited carbon nanofibers (CNF). Uniform RuxCuyP2 (~1.90 nm) on the surface of CNF are obtained by introducing the dispersed Ru, thereby improving the intrinsic activity for HER. On optimizing the Ru ratio, the (x = y = 1) RuCuP2/CNF catalyst exhibits an excellent HER electroactivity with an overpotential of 10 mV in 1.0 M NaOH electrolyte to produce 10 mA cm-2 current density, which is lower than commercial 20% Pt/C in alkaline solution. Moreover, the kinetic study demonstrated that electrochemical activation energies for HER of RuCuP2/CNF is 20.7 kJ mol-1 highest among different ratio bimetallic phosphide. This simple, cost-effective, and environmentally friendly methodology can pave the way for exploitation of bimetallic phosphide nanoclusters for catalyst design.

Quantum Plasmonics: Energy Transport Through Plasmonic Gap.

At the interfaces of metal and dielectric materials, strong light-matter interactions excite surface plasmons; this allows electromagnetic field confinement and enhancement on the sub-wavelength scale. Such phenomena have attracted considerable interest in the field of exotic material-based nanophotonic research, with potential applications including nonlinear spectroscopies, information processing, single-molecule sensing, organic-molecule devices, and plasmon chemistry. These innovative plasmonics-based technologies can meet the ever-increasing demands for speed and capacity in nanoscale devices, offering ultrasensitive detection capabilities and low-power operations. Size scaling from the nanometer to sub-nanometer ranges is consistently researched; as a result, the quantum behavior of localized surface plasmons, as well as those of matter, nonlocality, and quantum electron tunneling is investigated using an innovative nanofabrication and chemical functionalization approach, thereby opening a new era of quantum plasmonics. This new field enables the ultimate miniaturization of photonic components and provides extreme limits on light-matter interactions, permitting energy transport across the extremely small plasmonic gap. In this review, a comprehensive overview of the recent developments of quantum plasmonic resonators with particular focus on novel materials is presented. By exploring the novel gap materials in quantum regime, the potential quantum technology applications are also searched for and mapped out.