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The development of superhydrophobic and water-repellent surfaces utilizing a facile, economic and environmental-friendly way constitute an important scientific challenge since these materials find applications in a great number of industrial sectors as manufacturing, healthcare, and everyday consumer products. In this work, two-dimensional layered MXenes are utilized as functional additives for the development of superhydrophobic and water-repellent coatings prepared using waterborne nanocomposite formulations, which contain a low surface energy, short-chain perfluoroalkyl silanol, to provide the appropriate hydrophobicity; the nanoadditives are introduced to create the necessary surface roughness. While traditional methods typically employ 0D nanoparticles to achieve surface nanostructuring, the flake-like structure of Ti3C2T x MXenes introduces roughness that extends into the micron-scale. Different smooth substrates were coated by a one-step spraying process and the surface properties were investigated as a function of the additive content. Moreover, ternary nanocomposite coatings were developed with MXenes and alumina nanoparticles by a single-step spraying of an aqueous suspension. This combination results in hierarchical surface structures (with micrometer- and nanometer-scale roughness), achieving excellent water repellence with significantly lower additive concentration than the one needed when single-type of nanoadditives were used. Due to the low Ti3C2T x MXene content, the use of our approach extends beyond dark-colored applications, even in cases where the aesthetic result is critical. The nanohybrid coated surfaces exhibited mechanical and chemical durability, retaining their hydrophobicity after repeated abrasion cycles and under extreme pH conditions (pH 2 or 13). This study highlights the potential of MXenes as an innovative additive for next-generation water-repellent coatings.
For the past few years, conventional peroxidase mimics of nanoscale materials have found limited applications because of their low catalytic activity. Hence, it is desirable to control and tune their physicochemical properties through precise engineering to achieve a superior catalytic efficiency. Herein, we demonstrate an efficient strategy for substantially improving the peroxidase-mimetic activity of nanomaterials, particularly those that exhibit mixed redox states. One of these synthesized redox-active nanostructures is plasmonic nanoceria (PNC), which consists of a cerium oxide core with several encapsulated plasmonic gold nanoparticles within its poly-(acrylic acid) polymer coating. PNC nanostructures exhibit enhanced catalytic activity with a K cat value of 106 s-1, 103-fold higher than that of natural enzymes. Importantly, the catalytic activity of PNC was present over a wide range of temperatures and pH. Density functional theory (DFT) calculations revealed that efficient electron transfer from gold (Au) to cerium (Ce) atoms in the PNC significantly boosts its catalytic activity. Using Escherichia coli O157:H7 as a target pathogen, it is demonstrated that when PNC is applied as a peroxidase mimic for an enzyme-linked immunosorbent assay (ELISA), lower limits of detection are achieved than in conventional assays employing natural enzymes.
Bimetallic nanoparticles are promising catalysts that can improve performance in heterogeneous catalysis and solid-state electrochemistry. Exsolution is a useful method for forming such nanoparticles; however, it is limited by the elements present within the host oxide lattice. In this work, we develop and demonstrate a strategy to form bimetallic particles from La0.5Sr0.5Ti0.94Ni0.06O3 (LSTN) exsolution and using a reducible SnO2 capping layer, expanding the range of elements available for bimetallic nanoparticle formation. Using this capping layer strategy, we formed nickel-tin (Ni0-Sn0) bimetallic nanoparticles via exsolution. We used in situ near-ambient pressure X-ray photoelectron spectroscopy to monitor surface chemical changes during exsolution, showing that first, SnO2 volatilized. This SnO2 loss exposed the perovskite surface of LSTN to reducing conditions, which induced Ni exsolution, and compounded with SnO2 reduction led to the formation of bimetallic Ni0-Sn0 particles. To evaluate the associated microstructural evolution, we measured grazing incidence small-angle X-ray scattering (GISAXS), which confirmed the loss of the SnO2 capping layer, and scattering simulations suggested the formation of bimetallic particles. We confirmed the bimetallic nanoparticle composition and morphology by Auger spectroscopy and scanning transmission electron microscopy. The resulting bimetallic nanoparticles were smaller and more thermally stable than the monometallic Ni counterparts on LSTN. This capping layer and exsolution approach allow synthesizing multimetallic nanoparticles and can be applied to other reducible metal oxides and perovskite hosts, broadening the compositional space for advanced catalytic materials.
For the reliable design of flexible and wearable devices, it is important to understand the effect of mechanical deformation on thermal transport in the constituent materials. Here, a scanning thermal microscopy (SThM) bending test is proposed for the quantitative evaluation of the in-plane thermal conductivity of suspended bionanofilms through controlled bending deflection. Graphene oxide (GO)/silk fibroin (SF) and water-vapor-annealed GO/SF bionanofilms (thickness: ∼40 nm) are examined to understand the role of interfacial interactions in bending-dependent thermal transport. In the bending test, changes in the in-plane thermal conductivity are evaluated by systematically comparing SThM probe signals under contact and noncontact conditions; such a comparison helps separate solid heat conduction through the bionanofilm from the background heat transfer. This approach can facilitate a quantitative analysis of bending-induced thermal conductivity changes. At a bending deflection of 50 nm, the normalized thermal conductivity retention of the water-vapor-annealed bionanofilm was 97.7%, while that of the unannealed bionanofilm was 90.6%. Furthermore, the thermal degradation rate of the annealed film was lower by 75.1% (0.47 vs 1.89 × 10-3 nm-1). This improved stability is attributed to annealing-enhanced interfacial coupling, which suppresses phonon scattering and promotes continuous in-plane heat transport through silk fibroin bridging. These results demonstrate the influence of mechanical deformation on thermal conductivity in flexible nanocomposites and offer practical design guidelines for flexible electronics, wearable sensors, and bendable thermal management materials.
Aerogels composed of chiral nanoparticles combine the high surface area, extensive porosity, and low density of aerogels with the chiroptical and enantioselective properties of nanoscale chiral building blocks, thereby opening up potential applications in photonics, enantioselective catalysis, and molecular recognition. Here, we report the fabrication of a chiral TiO2-based aerogel from l/d-threoninol-functionalized nanoparticles. Gelation was induced by controlled destabilization of the nanoparticle dispersion through the addition of a nonsolvent, leading to the formation of a highly porous three-dimensional network. Remarkably, nuclear magnetic resonance (NMR) spectroscopy, supported by Fourier-transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy, thermogravimetric analysis (TGA), and elemental analysis, reveals that the chiral ligand interacting with the titania surface is largely removed during the gelation and solvent exchange processes. Despite the absence of the ligand, circular dichroism (CD) measurements demonstrate that the nanoparticles constituting the aerogel retain the chiroptical response with a g-factor comparable to that of the ligand-functionalized particles. These results indicate that the observed chirality arises from the inorganic TiO2 nanoparticles rather than from threoninol, suggesting that chiral structural features were imprinted onto the nanoparticle surface during synthesis. This work demonstrates that chiral information can be preserved within an inorganic aerogel architecture, laying the groundwork for the use of such materials in heterogeneous asymmetric photocatalysis.
Lignin is an attractive precursor for renewable carbon materials due to its low cost and comparatively high carbon yield. The resulting carbons may be used in energy storage devices (supercapacitors and batteries) and structural composites. Since lignin has substantial variability in its chemical structure, influenced by its botanical origin and the method of extraction, this work explores the effect of lignin type on the structure and performance of porous carbon materials, using electrospun carbon nanofibers applied as freestanding supercapacitor electrodes as an example. Precursor nanofiber mats were electrospun from aqueous NaOH solutions of six technical lignins, which originated from commercially relevant biomass types, i.e., hardwood (eucalyptus and beech), softwood (pine/spruce mix), and grass (Miscanthus) and three extraction methods (ethanol organosolv, Kraft, and ionosolv), with poly-(ethylene oxide) (PEO) as the spinning aid. After stabilization at 250 °C and carbonization/activation at 1000 °C, the supercapacitor performance was evaluated in symmetric two-electrode cells using an aqueous electrolyte (6 M KOH). Correlation of a large number of microstructural characteristics and lignin chemical properties showed that a high micropore (1-2 nm) volume increased gravimetric capacitance of the lignin-derived carbon nanofiber (LCNF) mats (up to 192 F/g at 0.25 A/g), while a high packing density maximized volumetric capacitance (up to 19.9 F/cm3 at 0.25 A/g). The packing density of the LCNF electrodes was strongly correlated to the viscosity of the lignin-PEO solution, showing potential for engineering material performance through spinning solution composition. Technical lignins with higher contents of phenylpropanoid linkages and hydroxyl groups, especially phenolic hydroxyl groups, exhibited increased microporosity and hence gravimetric capacity but also decreasing packing density and hence volumetric capacitance, indicating a trade-off situation. Finally, by changing the aqueous electrolyte to a water-in-salt electrolyte (12 mol/kg NaNO3), the energy density of the best-performing supercapacitor cell was increased from 8.9 to 15.5 Wh/kg, due to the higher stable operating voltage (1.8 vs 1.2 V), delivering competitive performance with typical activated carbon powder-based supercapacitors (5-15 Wh/kg) and highlighting the importance of the whole device design for boosting performance.
Today, Cu-based photocathodes are increasingly employed due to Cu abundance, environmental benefits, and high photoelectrocatalytic activity. However, despite significant advances in this field, the development of controllable methodologies to produce highly crystalline, structurally tailored, and reproducible CuO nanoarchitectures remains challenging. Here, we propose an alternative route for the fabrication of nanostructured CuO photocathodes that can address these goals. We have grown highly controlled CuO nanoparticles onto fluorine-doped tin oxide, FTO, electrodes by using a sputter gas aggregation source. The photoelectrochemical response was optimized by different thermal treatments, tuning the environment, duration, and temperature. We have systematically studied the influence of the treatments on the structure of the films and their correlation with the photoresponse of the photoelectrodes. We showed that the thermal treatments first induced nanoparticle growth, which is subsequently followed by coalescence. The best photoelectrochemical performance was obtained after complete recrystallization in the form of CuO nanocubes (thermal treatment in vacuum, 18 h, 500 °C), resulting in a porous film photocathode. This electrode presents maximum current densities of -1.2 mA/cm2, an applied bias photon-to-current efficiency of 1.4%, and a moderate operational stability for bare CuO photocathodes operating in aqueous electrolyte. The structural changes with improved crystallinity play a crucial role in favoring charge transport and reducing the recombination of photogenerated electron-hole pairs, thereby enhancing the photocurrent generated by the photocathode. Therefore, this methodology for producing CuO nanostructured films emerges as an alternative approach for fabricating photoelectrocathodes.
We investigate phase-coherent quantum transport in nanoscale Al-Bi2Se3-Al nanoribbon Josephson junctions by combining normal-state conductance spectroscopy with a junction-length-dependent study of Josephson transport. Differential conductance maps versus bias and gate voltage reveal Fabry-Pérot interference, whose periodicity matches the nanoribbon width, consistent with transverse quantization and quasi-ballistic surface-state trajectories in 430 nm wide devices. A systematic investigation of the characteristic voltage I c R n as a function of junction length L exhibits a clear plateau for L ≤ 500 nm, indicative of a short ballistic contribution to the Josephson transport, and decreases for longer junctions as diffusive transport dominates. Together, Fabry-Pérot interference and Josephson transport measurements provide complementary, channel-selective evidence for quasi-ballistic surface-state transport persisting over several hundred nanometers in hybrid topological insulator nanostructures. These results demonstrate the potential of Bi2Se3 nanoribbon Josephson junctions as a nanoscale platform for phase-coherent superconducting electronics, topological quantum computing architectures, and topological spintronic devices.
Understanding how lipid nanocarriers behave inside cells is key to improving nucleic acid and protein therapies. However, direct visualization of intracellular trafficking mechanisms is challenging because liposomes possess low intrinsic electron density and highly dynamic and flexible structural features. In this study, we present Lipo-Gold, a hybrid nanosystem consisting of clinically relevant liposomes containing multiple intraluminal small gold nanoparticles (AuNPs) and demonstrate its utility for nanoscale-resolution investigation of intracellular delivery pathways. Using an optimized adaptation of a stepwise in situ reduction strategy, specifically tailored to a cholesterol-containing lipid formulation, we generated multiple nonspace-filling AuNPs (15-20 nm) within each vesicle without altering the bilayer structure, surface charge, or colloidal stability, and overall vesicle architecture. Comprehensive physicochemical characterization, including dynamic light scattering, nanoparticle tracking analysis, and transmission electron microscopy (TEM), along with cellular uptake investigations by flow cytometry and confocal microscopy, demonstrates that Lipo-Gold retains the same biological identity and cellular interaction profile as the corresponding unmodified liposomes. In HeLa cells, Lipo-Gold also exhibits similar uptake kinetics and intracellular trafficking behavior comparable to unloaded vesicles. The intraluminal AuNPs generate strong electron contrast, enabling direct visualization of intracellular nanoscale transport events, including endocytic uptake, vesicle maturation, and subcellular confinement. Correlative light-electron microscopy (CLEM) further enabled spatial overlap between fluorescent liposome signals and electron-dense AuNP clusters, providing a multimodal imaging platform with nanometric structural resolution. Across all examined sections, AuNPs remained confined to membrane-bound endosomal compartments, with no evidence of cytosolic dispersion, consistent with the expected behavior of anionic, nonfusogenic liposomes. By combining fluorescence tracking with high-resolution structural imaging while preserving native liposome-cell interactions, Lipo-Gold offers a valuable tool for investigating intracellular delivery barriers and for guiding the rational development of next-generation lipid-based therapeutics.
Doped metal oxide nanocrystals have emerged as a versatile platform for optoelectronic, catalytic, and energy-related applications, owing to their tunable electronic structure, chemical robustness, and solution processability. Recent advances in continuous injection ("living") synthesis have transformed these materials from static products of batch reactions into programmable inorganic architectures, enabling deterministic control over size, faceting, surface chemistry, and, critically, radial dopant distribution. In this Review, we examine how precursor flux, reagent identity, and temporal dopant delivery encode growth pathways that directly map onto plasmonic response, charge transport, electrochromic behavior, and chemical reactivity. We highlight how controlled dopant placement and surface electrostatics define depletion layers and tune active nanocrystal response. Beyond optical and electronic function, we discuss emerging opportunities in catalysis, photoinduced charge storage, and chromogenic devices, where nanocrystals designed at the synthesis stage enable functionalities not accessible through postsynthetic modification alone. Finally, we outline future directions toward predictive synthesis and scalable integration, positioning continuous growth as a general design framework for next-generation functional oxide-based nanomaterials.
Complex refractive indices of materials encode fundamental information on light-matter interactions and are critical for the design of advanced photonic and optoelectronic devices. In many emerging materials, refractive indices change under external stimuli such as temperature, electric fields, or strain. Tracking these changes in-operando is critical for active photonic and optoelectronic device design, but remains challenging. Conventional methods such as ellipsometry rely on labor-intensive model fitting and are often impractical for multilayer stacks or in-operando measurements. Optical reflectometry offers a simpler alternative but suffers from ambiguous extraction of refractive index from reflectance spectra and limited applicability under dynamic modulation. Here, we present ReflectoRNN, an artificial intelligence (AI)-powered reflectometry framework based on recurrent neural networks (RNN), for real-time extraction of complex refractive indices in evolving materials. ReflectoRNN extracts refractive indices from reflectance spectra under thermal, electrical, magnetic, or mechanical stimuli. It achieves a median Pearson's correlation coefficient (PCC) of 0.998 and a relative accuracy score (RAS) of 0.968 on generated datasets. Validation experiments on MoS2 and WS2 across diverse substrates, including single-layer and multilayer dielectric stacks, and distributed Bragg reflectors (DBRs), demonstrate high accuracy and physical consistency, with temperature-dependent exciton resonance energy matching Bose-Einstein predictions. ReflectoRNN enables in-operando optical characterization of materials across complex photonic structures and offers a pathway toward automated, real-time monitoring and accelerated materials discovery.
High-entropy-alloy (HEA) nanoparticles containing at least five elements are an emerging family of catalysts. Due to the increased complexity of multicomponent atomic mixing, the size reduction of HEA nanoparticles down to around 1 nm is a substantial challenge, which is crucial to enhance the efficiency of atom utilization. Herein, we report a template-confined synthesis strategy for constructing a library of ultrasmall HEA nanoparticles with sizes of approximately 1 nm and compositions containing up to ten elements, including Pt, Pd, Ru, Rh, Fe, Co, Ni, Cu, Mo, and Zn. By leveraging the confinement effect of the mesoporous carbon structure and the autocatalytic reduction of the metal-precursor mixture at a low reaction temperature, we successfully achieve the uniform embedding of a diverse array of ultrasmall multicomponent HEA nanoparticles within the mesoporous framework. Additionally, we demonstrate that the 1 nm PtRuFeCoNi nanoparticles exhibit enhanced mass activity and superior atom utilization in both hydrogen evolution and hydrogen oxidation reactions, surpassing other quinary HEA and commercial Pt/C catalysts. Furthermore, operando X-ray absorption spectroscopy and theoretical calculations suggest a cooperative multielement effect among the five constituent elements, in which Pt- and Ru-containing local environments provide favorable sites for H-intermediate adsorption and contribute to the enhanced catalytic performance.
The fabrication of high-performance submicrometer copper indium sulfoselenide (CISSe) absorbers from environmentally friendly solutions offers a promising strategy to reduce material consumption and enable large-scale production. However, the presence of a carbon residual layer in solution-processed absorbers typically limits device efficiency. To address this issue, this research employs a copper-indium-thiourea-N,N-dimethylformamide (Cu-In-TU-DMF) solution to fabricate high-quality CISSe (without a carbon residual layer). Furthermore, to mitigate nonradiative recombination loss, randomly distributed dielectric silica (SiO2) nanospheres (250 nm in diameter) are incorporated near the rear interface of the absorber. As a result, the proposed strategy simultaneously improves open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF), resulting in a champion device efficiency of 9.9%, with a Voc of 496.2 mV, a Jsc of 29.4 mA/cm2, and an FF of 67.6%. Moreover, when the SiO2 nanospheres are applied to passivate the rear interface of a semitransparent CISSe device fabricated on an indium tin oxide (ITO) back contact, all photovoltaic parameters are boosted. In summary, our research demonstrates that embedding SiO2 nanospheres into the absorber layer provides a simple and effective strategy for enhancing the performance of solution-processed solar cells. This method can be easily applied to other solution-based photovoltaic technologies, such as copper indium gallium selenide (Cu(In,Ga)Se2), copper zinc tin selenide (Cu2ZnSnSe4), antimony selenide (Sb2Se3), silver bismuth sulfide (AgBiS2), and perovskite solar cells.
Metal-organic frameworks have been intensively investigated for their ability to effectively control the growth and surface chemistry of nanosized guests, with their pores acting as templates and potentially providing anchoring sites. Since the speciation, as determined by the geometry and surface chemistry of hydride-forming metals, such as Pd, under particular conditions (T, p), is controlled by their size at and beyond the nanoscale, metal-organic frameworks are a prospective matrix for speciation or phase selection. This is of relevance because the role and characteristics of the phases in hydrogenation reactions involving hydride-forming Pd catalysts are open questions. In particular, it is a matter of debate which palladium phase is the most active and most selective, as they often occur simultaneously under catalytic conditions. For the first time, our thorough investigation, including operando XAFS and computer simulations, demonstrates that by embedding Pd nanoclusters, ≤1 nm in diameter, in the pores of the NH2-UiO-66 metal-organic framework, the speciation of subnanometric Pd particles can be controlled, such that the active particles only exist in their metallic state under reaction conditions; in fact, the Pd-H2 mixture only affords surface-bound hydrogen atoms. This control of Pd speciation consequently enables the direct probing of the phase activity and selectivity in the model reaction of 1,3-butadiene hydrogenation to butenes, wherein it showed no deactivation and improved selectivity compared to conventionally prepared catalytic systems. This result shows that the metallic phase can be stabilized through subnanometric size control and that it is more selective and less prone to overhydrogenating the butadiene reactant to butane, resulting in a purer product.
Capture of biomolecules within porous membranes underpins the performance of lateral flow immunoassays and membrane chromatography, yet direct measurement of binding kinetics on sub-second timescales remains challenging. Here, we introduce an approach based on rapid filtration that enables quantitative measurement of antibody and nanoparticle capture on porous membranes over contact times ranging from 0.25 to 10 s. Using Fusion 5 silica membranes functionalized with protein A, we measured the capture of Alexa Fluor 555-labeled antibodies and antibody-conjugated europium nanoparticles at flow rates between 0.5 and 8 mL s-1. Antibody capture on protein A surface scaled with contact time rather than flow rate, indicating that binding under these conditions is not transport-limited. Increasing protein A surface density enhanced antibody capture up to ca. 0.42 μg mm -2, above which no further increase was observed, suggesting saturation of accessible binding sites. For IgG-conjugated nanoparticles, rapid filtration resolved distinct positive and negative signals within 0.5 s, demonstrating sensitivity on time scales relevant to lateral-flow line formation. This rapid filtration analysis could be widely applied to the study short-time adsorption kinetics in porous matrices and offers quantitative insights for optimizing membrane-based assays and chromatographic separations.
Piezoelectric dynamic therapy utilizes the acoustic-electric conversion of piezoelectric materials under ultrasound (US) to generate abundant reactive oxygen species (ROS) to kill tumor cells, offering an attractive protocol for tumor therapy. However, traditional piezoelectric sonosensitizers generally exhibit wide band gaps, resulting in suboptimal charge separation, low ROS generation efficiency, and insufficient induction of immunogenic cell death (ICD), which limits their therapeutic efficacy. In this study, we report a narrow-band gap piezoelectric nanoplatform engineered from porphyrin-osmapentalyne hybrids (P-OsPT). By strategically coupling anti-Hückel carbolong electron acceptor (A) with a Hückel-compliant porphyrin electron donor (D), a pronounced A-D-A architecture is established. The incorporation of osmium within the carbolong framework facilitates a dπ-pπ conjugation system, which not only significantly narrows the band gap and provides efficient channels for intraparticle charge transport but also imparts piezoelectric properties to the material. Under US irradiation, P-OsPT nanoparticles (NPs) achieve efficient acoustic-electric conversion, resulting in high ROS generation efficiency. In vitro and in vivo studies demonstrate that P-OsPT NPs-mediated piezoelectric immunotherapy can effectively kill tumor cells while inducing ICD, resulting in activation of immune response and inhibition of tumor metastasis. This study highlights the potential of carbolong complexes as a versatile platform for piezoelectric immunotherapy.
The inherent magnetism of iron oxide nanoparticles (IONPs) provides appealing benefits for antibacterial treatment, as IONPs can be readily guided, concentrated, and removed from a specific site. Additionally, gold and silver demonstrate antibacterial properties that effectively inhibit bacterial growth. By combining one of these antibacterial metals and the IONP, a dual-purpose metallic nanoparticle treatment can thus be constructed. In our study, we developed silica-coated IONPs to facilitate the binding and decoration with either gold (Au) or silver (Ag). Therefore, the focus of this research is to apply the hard/soft acid/base (HSAB) theory by investigating the affinity of Au or Ag after encapsulating the IONPs with one of three silane capping agents, providing either an amine (AP-SIONP), hydroxide (T-SIONP), or thiol (MP-SIONP). With the use of inductively coupled plasma optical emission spectroscopy (ICP-OES), the amount of metal decorated on the antibacterial metallic SIONPs was compared. We demonstrated that although both Au and Ag had an affinity for all three ligands, Au (79 ± 18 and 23 ± 0 μg/L) and Ag (72 ± 36 and 160 ± 23 μg/L) had a higher affinity for amines and thiols, respectively. Finally, the optimal Au and Ag SIONPs were applied to a Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterium to investigate their antibacterial and capturing potential. Our findings indicate that AgMP-SIONPs demonstrated superior antibacterial potential by providing inhibitory concentrations at 62.5 and 500 μg/mL for E. coli and S. aureus, respectively. Moreover, AgMP-SIONPs provided a minimum bacterial concentration (MBC) at 62.5 μg/L but did not reach MBC for the Gram-positive bacterium. Overall, this study provides the protocol for an optimal antibacterial metallic SIONP through the application of the HSAB theory and demonstrated the promise of silver for its antibacterial potential and SIONP ability to further capture bacteria, all of which opens a promising research exploration.
Spin-orbit-torque-driven auto-oscillations in spin Hall nano-oscillators (SHNOs) provide a promising route toward energy-efficient, nanoscale microwave devices for neuromorphic computing and high-frequency technologies. Achieving robust oscillations requires lowering the threshold current (Ith), governed by the spin Hall efficiency (θSH). Conventional approaches to enhance θSH often involve trade-offs, such as increased resistivity and interfacial effects. Here, we demonstrate a pronounced enhancement of the bulk spin Hall effect in PtBi alloys via crystallographic engineering, achieving a 3-fold increase in θSH from 0.07 in Pt100.0Bi0.0 to 0.24 in Pt94.0Bi6.0 and 0.19 in Pt91.3Bi8.7, extracted from DC-bias spin-torque ferromagnetic resonance. The enhancement arises from bulk-dominated extrinsic side-jump scattering. Correspondingly, Ith is reduced by 42% and 32% in 100 nm SHNOs based on Co40Fe40B20(3 nm)/Pt94.0Bi6.0(4 nm) and Co40Fe40B20(3 nm)/Pt91.3Bi8.7(4 nm), respectively. The devices exhibit narrower linewidths (∼25 MHz), enhanced quality factors (350 ≤ Q ≤ 550, ∼4× higher than Pt (Pt100.0Bi0.0)), and a 61.6% reduction in threshold power. These findings establish PtBi alloys as efficient spin Hall materials, enabling reduced power consumption for SHNO-based neuromorphic and memory technologies.
The recent perspective of multiprincipal element alloys (MPEAs), also known as high-entropy alloys (HEAs), has emerged as a very promising area for material design. Additive manufacturing (AM) strategies have also been noted to provide additional strength to HEA systems. In the selected dual-nanoprecipitation Al0.2Co1.5CrFeNi1.5Ti0.3 HEA system, an additional strength of approximately 300-400 MPa was achieved by adopting an additive manufacturing route as compared to its cast and wrought counterparts. However, the challenge of oxidation degradation always imposes a severe limitation for high-temperature applications in gas turbines, power plants, and aerospace components. Hence, ensuring material sustainability, longevity, and integrity for high-temperature applications inevitably requires the exploration of the oxidation behavior of alloys. In the current study, the oxidation performance of Al0.2Co1.5CrFeNi1.5Ti0.3 HEA, in as-printed as well as nanoprecipitation-strengthened aged states, was evaluated from 600°C to 1200°C. A comparative framework elucidating the mechanistic aspects and elemental redistribution of nanoprecipitates on oxidation behavior has been highlighted. In both the as-printed and aged states, the alloys followed subparabolic oxidation weight gain kinetics below 900°C. However, the thickness growth kinetics exhibited parabolic behavior above 900°C. The oxide layer exploration manifested the formation of a homogeneous Cr-oxide layer, which acts as a protective barrier against oxidation activity. The impact of atomic size on mobility also played a significant role in suppressing the formation of outer Al and Ti oxide layers, instead of having a lower reduction potential compared to Cr.
Nickel nanoparticles (denoted as Ni NPs), being applicable in catalysis, battery manufacturing, and bioseparation, have garnered considerable attention due to their remarkable magnetism, crystalline anisotropy, high coercivity, and excellent chemical stability. Unlike previous studies that require multi-step surface functionalization with chelating ligands, such as nitrilotriacetic acid (abridged as NTA), to achieve histidine-tagged (denoted as His-tagged) protein binding, this study reports a one-step hydrothermal synthesis of Ni NPs with a spherical-spiky architecture that provides abundant intrinsic Ni2+ active sites. A series of synthesis experiments were conducted to systematically optimize the hydrothermal reaction conditions (solution pH, temperature, and time). The ability of Ni NPs to separate and purify His-tagged fusion proteins was evaluated in relation to their abundant Ni2+ active binding sites and robust magnetic responsiveness. It was found that Ni NPs were able to rapidly, specifically, and efficiently purify a variety of His-tagged proteins, achieving a high saturation adsorption capacity of 80.36 mg/g, significantly higher than commercial Ni-NTA resins and previously reported Ni-based adsorbents, while retaining excellent recyclability (>80% after 5 cycles). These features underscore the potential of Ni NPs as cost-effective, reusable, and high-performance nano-adsorbents for protein separation, offering distinct advantages over conventional functionalization-dependent methods.