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Nanoscale ruthenium (Ru)-based materials are promising replacements for existing multilayered Cu interconnects in integrated circuits. However, it is not easy to apply the results of previously reported studies directly to the electrochemical damascene process because the previous studies have mainly focused on thin films by dry deposition. Here, we report the electrical resistivity and microstructure of electrodeposited Ru nanowires. We estimate that the resistivity value of a 10 nm diameter Ru nanowire to be 71.6 μΩ cm after analyzing the resistivity values of individual nanowires with various diameters. Furthermore, we investigate the electrical properties of RuxCo1-x nanowires where x is 0.04–0.99 at.% as possible replacements of the current TaN barrier structures. Over the entire composition range, the resistivity values of alloys are much lower than that of the conventional TaN. Additionally, Ru and Ru-alloy nanowires surrounded by dielectric silica are thermally stable after 450 °C heat treatment. Therefore, the nanoscale Ru and Ru-Co alloys possessing low resistivity values can be candidates for the interconnect and barrier materials, respectively.

Macrophages can associate with extracellular matrix (ECM) demonstrating nanosequenced cell-adhesive RGD ligand. In this study, we devised barcoded materials composed of RGD-coated gold and RGD-absent iron nanopatches to show various frequencies and position of RGD-coated nanopatches with similar areas of iron and RGD-gold nanopatches that maintain macroscale and nanoscale RGD density invariant. Iron patches were used for substrate coupling. Both large (low frequency) and externally positioned RGD-coated nanopatches stimulated robust attachment in macrophages, compared with small (high frequency) and internally positioned RGD-coated nanopatches, respectively, which mediate their regenerative/anti-inflammatory M2 polarization. The nanobarcodes exhibited stability in vivo. We shed light into designing ligand-engineered nanostructures in an external position to facilitate host cell attachment, thereby eliciting regenerative host responses.

The development of heat-generating magnetic nanostructures is critical for the effective management of tumors using magnetic hyperthermia. Herein, we demonstrate that polyethylene glycol (PEG)-coated iron oxide (magnetite, Fe3O4) multigranule nanoclusters (PEG-MGNCs) can enhance the efficiency of hyperthermia-based tumor suppression in vitro and in vivo. MGNCs consisting of granules (crystallites) measuring 22.9 nm in diameter were prepared via the hydrothermal polyol method, followed by the surface modification of MGNCs with PEG-dopamine. The freshly prepared PEG-MGNCs exhibit 145.9 ± 10.2 nm diameter on average under aqueous conditions. The three-dimensional structures of PEG-MGNCs enhance the hyperthermic efficacy compared with PEGylated single iron-oxide nanoparticles (NPs), resulting in severe heat damage to tumor cells in vitro. In the SCC7 tumor-bearing mice, near-infrared fluorescence dye (Cy5.5)-labeled PEG-MGNCs are successfully accumulated in the tumor tissues because of NP-derived enhanced permeation and retention effect. Finally, the tumor growth is significantly suppressed in PEG-MGNC-treated mice after two-times heat generation by using a longitudinal solenoid, which can generate an alternating magnetic field under high-frequency (19.5 kA/m, 389 kHz) induction. This study shows for the first time that the PEG-MGNCs greatly enhance the hyperthermic efficacy of tumor treatment both in vitro and in vivo.

Developing materials with remote controllability of macroscale ligand presentation can mimic extracellular matrix (ECM) remodeling to regulate cellular adhesion in vivo. Herein, we designed charged mobile nanoligands with superparamagnetic nanomaterials amine-functionalized and conjugated with polyethylene glycol linker and negatively charged RGD ligand. We coupled negatively a charged nanoligand to a positively charged substrate by optimizing electrostatic interactions to allow reversible planar movement. We demonstrate the imaging of both macroscale and in situ nanoscale nanoligand movement by magnetically attracting charged nanoligand to manipulate macroscale ligand density. We show that in situ magnetic control of attracting charged nanoligand facilitates stem cell adhesion, both in vitro and in vivo, with reversible control. Furthermore, we unravel that in situ magnetic attraction of charged nanoligand stimulates mechanosensing-mediated differentiation of stem cells. This remote controllability of ECM-mimicking reversible ligand variations is promising for regulating diverse reparative cellular processes in vivo.

Metallic barcode nanowires (BNWs) composed of repeating heterogeneous segments fabricated by template-assisted electrodeposition can offer extended functionality in magnetic, electrical, mechanical, and biomedical applications. We can consider such nanostructures as a three-dimensional system of magnetically interacting elements with magnetic behavior strongly affected by complex magnetostatic interactions. This study discusses the influence of geometrical parameters of segments on the character of their interactions and the overall magnetic behavior of the array of BNWs having alternating magnetization. By controlling the applied current densities and the elapsed time in the electrodeposition, we regulate the dimension of the Fe-Au BNWs. We show that the Fe and Au segments are made of Fe-Au alloys with high and low magnetization. With the help of micromagnetic simulations, we discover and analyze the three types of magnetostatic interactions in the BNW arrays. As a result, we demonstrate that the dominating type of interaction depends on the geometric parameters of the Fe and Au segments and the interwire and intrawire distances., Comment: 29 pages, 7 figures

Barcode nanowires (BNWs) composed of multiple layered segments of different materials are attractive to bioengineering field due to their characteristics that allow the adjustment of physicochemical properties and conjugation with two or more types of biomolecules to facilitate multiple tasks. Here, we report a metallic Fe (iron)-Au (gold) BNW-based platform for capturing CD8 T cells and the interferon-γ (γ) they secrete, both of which play key roles in controlling infectious diseases such as tuberculosis, at the single-cell level. We also describe an efficient approach for conjugating distinct antibodies, which recognize different epitopes to appropriate materials. The platform achieved detection even with 4.45-35.6 μg mL-1 of BNWs. The T cell capture efficiency was close to 100% and the detection limit for interferon-γ was 460 pg mL-1. This work presents a potential guideline for the design of single-cell immunoassay platforms for eliminating diagnostic errors by unambiguously identifying disease-relevant immune mediators.

Native extracellular matrix (ECM) can exhibit cyclic nanoscale stretching and shrinking of ligands to regulate complex cell-material interactions. Designing materials that allow cyclic control of changes in intrinsic ligand-presenting nanostructures in situ can emulate ECM dynamicity to regulate cellular adhesion. Unprecedented remote control of rapid, cyclic, and mechanical stretching ("ON") and shrinking ("OFF") of cell-adhesive RGD ligand-presenting magnetic nanocoils on a material surface in five repeated cycles are reported, thereby independently increasing and decreasing ligand pitch in nanocoils, respectively, without modulating ligand-presenting surface area per nanocoil. It is demonstrated that cyclic switching "ON" (ligand nanostretching) facilitates time-regulated integrin ligation, focal adhesion, spreading, YAP/TAZ mechanosensing, and differentiation of viable stem cells, both in vitro and in vivo. Fluorescence resonance energy transfer (FRET) imaging reveals magnetic switching "ON" (stretching) and "OFF" (shrinking) of the nanocoils inside animals. Versatile tuning of physical dimensions and elements of nanocoils by regulating electrodeposition conditions is also demonstrated. The study sheds novel insight into designing materials with connected ligand nanostructures that exhibit nanocoil-specific nano-spaced declustering, which is ineffective in nanowires, to facilitate cell adhesion. This unprecedented, independent, remote, and cytocompatible control of ligand nanopitch is promising for regulating the mechanosensing-mediated differentiation of stem cells in vivo.

Mesocrystals, consisting of small subunits, have gained research interests owing to their ability to simultaneously modify material-specific properties and interactions among subunits. However, despite these unique characteristics, most mesocrystals are composed of a single material, and there is a disjunction between academic discovery and practical application. In this study, the synthesis of multi-component mesocrystalline nanoparticles composed of Fe3 O4 , ZnFe2 O4 , and ZnO subunits using a polymerization induced heterogeneous nucleation method is reported. The structure has small ZnFe2 O4 and ZnO nanocrystals covering the Fe3 O4 crystallites. It exhibits not only magnetic and catalytic properties determined by the size of each subunit nanocrystal, but also enhances photocatalytic and colloidal properties that originates because of its crowded arrangement. The magnetically recoverable catalysts exhibit remarkable photodegradation of organic molecules under the irradiation of visible light for 1 h; thus, improving its applicability in purifying a large amount of wastewater during the daytime.

The native extracellular matrix (ECM) can exhibit heterogeneous nano-sequences periodically displaying ligands to regulate complex cell-material interactions in vivo. Herein, an ECM-emulating heterogeneous barcoding system, including ligand-bearing Au and ligand-free Fe nano-segments, is developed to independently present tunable frequency and sequences in nano-segments of cell-adhesive RGD ligand. Specifically, similar exposed surface areas of total Fe and Au nano-segments are designed. Fe segments are used for substrate coupling of nanobarcodes and as ligand-free nano-segments and Au segments for ligand coating while maintaining both nanoscale (local) and macroscale (total) ligand density constant in all groups. Low nano-ligand frequency in the same sequences and terminally sequenced nano-ligands at the same frequency independently facilitate focal adhesion and mechanosensing of stem cells, which are collectively effective both in vitro and in vivo, thereby inducing stem cell differentiation. The Fe/RGD-Au nanobarcode implants exhibit high stability and no local and systemic toxicity in various tissues and organs in vivo. This work sheds novel insight into designing biomaterials with heterogeneous nano-ligand sequences at terminal sides and/or low frequency to facilitate cellular adhesion. Tuning the electrodeposition conditions can allow synthesis of unlimited combinations of ligand nano-sequences and frequencies, magnetic elements, and bioactive ligands to remotely regulate numerous host cells in vivo.

The architecture of nanostructures is pivotal to determine material properties at the nanoscale, indicating the importance of harnessing sophisticated nanochemistry to elicit desirable material morphology with uniformity. The simplicity of template-assisted electrodeposition makes it a promising strategy for the fabrication of anisotropic nanomaterials. However, a challenge it faces is the complexity of the materials. This study presents a facile strategy and fabrication mechanism to synthesize nanotubes or nanocoils by selecting additives such as vanadyl ions and L-ascorbic acid. Vanadyl ions stick to the protonated anodized aluminum oxide surface, paving the way for electronic conduction. When a higher electrical field is applied, linear sweep voltammetry implies surface conduction mode is dominant in the spatially confined template. As L-ascorbic acid is included in the electrolyte, the nanostructure can be regulated from nanotubes to nanocoils. The nanocoils consist of numerous nanocrystalline primary particle considered as building blocks, and their relationship affects the final structures. The reaction product, vanadyl ascorbate, acts as a hurdle by partially hindering surface conduction and a helical modifier, inducing the formation of primary particle and their nanocoil assembly. Finally, a state diagram is provided to illustrate the diverse nanostructures at optimized applied current and additive ratio conditions.

MnOx-based catalysts have been applied to the selective catalytic reduction of NOx with ammonia (NH3) owing to their high NOx removal efficiency and catalytic stability. In general, the fabrication of a variety of nanomaterials in a complex structure requires complicated processes, including heat treatment and a series of cleaning steps. In addition, MnO2 which has diverse polymorphs, exhibits different catalytic effects depending on its crystalline structure. Among them, synthesizing the e-MnO2 phase, which functions as a nanocatalyst, has been the most difficult and has hardly been reported. Here, we report the synthesis of heterostructured composite nanocatalysts consisting of e-MnO2 nanowires (NWs) and CeO2 nanoparticles (NPs) by applying pulsed currents sequentially. This method drastically simplifies the overall process compared to the conventional techniques. Through X-ray diffraction and transmission electron microscopy, it was confirmed that 2–3 nm of CeO2 NPs were formed on the surfaces of the e...

Helicity, a natural property of macro-, micro-, and nano-objects, potentially offers a new dimension to mechanical and electromagnetic applications for creating emerging nanodevices, such as nanorobots, nanomagnets, nanosensors, and high-density magnetic memory. Helical magnetic nanosprings are unique objects with remarkable magnetic properties, including the absence of stray fields in remanence owing to the chiral geometry, which makes them promising for data storage devices, nanoelectromechanical systems, and biomedical usage. Here, we investigated Co and CoFe nanospring arrays electrodeposited in highly ordered nanoporous templates. We report helical-shape-driven magnetization reversal of the nanosprings in comparison with the behavior of dipolarly coupled nanowires. We reveal two magnetization reversal modes depending on the orientation of the external magnetic field: coherent rotation of magnetization in the longitudinal geometry and three-dimensional vortex domain wall motion in the transverse geometry. The experimental findings are supported by analytical calculations and micromagnetic simulations that help to explain the field-dependent spin configurations observed by magnetic force microscopy.

The fabrication of 3D hollow nanostructures not only allows the tactical provision of specific physicochemical properties but also broadens the application scope of such materials in various fields. The synthesis of 3D hollow nanocoils (HNCs), however, is limited by the lack of an appropriate template or synthesis method, thereby restricting the wide-scale application of HNCs. Herein, a strategy for preparing HNCs by harnessing a single sacrificial template to modulate the interfacial reaction at a solid-liquid interface that allows the shape-regulated transition is studied. Furthermore, the triggering of the Kirkendall effect in 3D HNCs is demonstrated. Depending on the final state of the transition metal ions reduced during the electrochemical preparation of HNCs, the surface states of the binding anions and the composition of the HNCs can be tuned. In a single-component CrPO4 HNC with a clean surface, the Kirkendall effect of the coil shape is analyzed at various points throughout the reaction. The rough-surface multicomponent MnOx P0.21 HNCs are complexed with ligand-modified BF4 -Mn3 O4 nanoparticles. The fabricated nanocomposite exhibits an overpotential decrease of 25 mV at neutral pH compared to pure BF4 -Mn3 O4 nanoparticles because of the increased active surface area.

Magnetic nanosprings have applications in various fields, e.g., in sensors, actuators, and biomedical applications. However, it is difficult to synthesize them due to their complicated structure. Here, we report the synthesis of CoFe nanosprings by electrodeposition using vanadium oxide ions and ascorbic acid. The nanosprings have a helical structure and exist in the form of the Co53Fe47 alloy. Hysteresis curves of CoFe nanowire and nanospring arrays show soft ferromagnetic characteristics. The CoFe nanowires have shape anisotropy with an easy axis parallel to the array direction, whereas the CoFe nanosprings exhibit an isotropic behavior.

Owing to their chemical and thermal stability and doping effects on providing electrons to the conduction band, doped ZnO nanowires have generated interest for use in electronic devices. Here we report hydrothermally grown Fe-doped ZnO nanowires and their gas-sensing properties. The synthesized nanowires have a high crystallinity and are 60 nm in diameter and 1.7 μm in length. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) are employed to understand the doping effects on the microstructures and gas sensing properties. When the Fe-doped ZnO nanowire arrays were evaluated for gas sensing, responses were recorded through changes in temperature and gas concentration. Gas sensors consisting of ZnO nanowires doped with 3-5 at.% Fe showed optimum formaldehyde (HCHO) sensing performance at each working temperature.

A facile synthesis of nanostructured vanadium oxide catalysts grown inside a honeycomb ceramic filter by electrodeposition without heat treatment is reported. The prepared catalysts are investigated for a selective catalytic reduction (SCR) of nitrogen oxide (NOx) with ammonia (NH3) in the temperature ranges from 250 to 450 °C. The SCR test results indicate that the NOx removal efficiency of the as-deposited sample is comparable to that of the sample heat treated at 600 °C as well as that of the sample prepared by conventional wash coating method. The nanostructured catalysts show similar NOx removal efficiencies after several recycles. Both polycrystalline and amorphous phases co-exist in the electrodeposited V-oxide catalysts confirmed by X-ray diffraction and selective area electron diffraction. The V-oxide catalysts show stronger V=O bond peaks and higher ratio of V4+/V5+ and Oα/Oβ on their surfaces as characterized by Raman spectroscopy and X-ray photoelectron spectroscopy.

The cobalt (Co)–tungsten (W) alloys exhibit unique combinations of mechanical and magnetic properties, biocompatibility, resistance against corrosion, wear, and high-temperature, which makes them desirable materials for various practical applications. A nanoporous template with incorporated Co–W alloy nanowires is a soft magnetic composite, whose dielectric and magnetic properties can be tuned through the host material, pore distribution and size, Co–W composition and crystal structure, and geometry of the nanowires. Here, we report the composition-dependent structural and magnetic properties of Co–W alloy nanowires embedded in alumina templates by electrodeposition. The addition of W transforms cobalt from the crystalline hexagonal-close-packed (hcp) Co to a mixed nanocrystalline/amorphous-like Co(W) solid solution with ferromagnetic behavior and composition similar to that of the weakly magnetic Co3W compound. The combination of the approach to magnetic saturation, anisotropy field distribution method, micromagnetic simulations, and first-order reversal curve diagram identification method elucidates the structure-driven magnetization reversal processes in both individual nanowires and magnetostatically coupled array as a whole.

As the design rule of the integrated circuits is decreasing to a 10 nm scale, the total electrical resistance of conventional Cu metallization increases rapidly. New conducting materials such as Co with shorter electron mean free paths, have gained significant attention and may replace Cu. Further, Co W alloys are being considered as alternatives to replace the TaN/Ta barrier layers. However, limited studies have been carried out to elucidate electrical resistivity changes in nanoscale Co and its alloys depending on the size and composition. In this study, we report the variations in electrical resistivity and the microstructural evolution of a series of single Co nanowires (NWs) prepared using template-assisted electrochemical deposition, with diameters ranging from 16 to 130 nm. Besides, we investigate Co W alloy NWs with W content ranging from 0 to 25.1 at.%. The Co NWs, in all diameter ranges, show substantially lower resistivity values compared to that in previous reports, where the value of an NW with a diameter of 16 nm is approximately 40 μΩ∙cm. The grain size also decreases as NW diameter decreases. Alloying W with Co NWs increases electrical resistivity. The 30 nm diameter Co W alloy NW with 25.1 at.% W shows the highest electrical resistivity value at 170 μΩ∙cm. This value decreases as post-deposition annealing temperature increases.

MnO

We report a facile fabrication concept for nanotubes (NTs) based upon template-assisted electrodeposition, which is widely applied for metallic nanowire (NW) synthesis. Co NTs have been synthesized into nanoporous anodized aluminum oxide (AAO) templates via electrodeposition by simply adding a small amount of chemicals including vanadyl ions (VO2+).

Magnetic nanoparticles (NPs) generate growing interest of scientists not only from physics and chemistry areas, but also from biomedicine including cancer research. By means of self-organization, NPs can form agglomerates, superlattices or ordered arrays consisting of finite number of nanoparticles. The understanding of magnetic behavior of coupled NPs in chains will open up new routes of their practical usage.

Understanding the ferromagnetic behavior of coupled magnetic nanoparticles (NPs) in a chain structure, called a “nanochain (NC)”, will open up new routes for its practical use. Here, we report the magnetization reversal modes in isolated magnetite (Fe3O4) NPs with diameters of 100 and 200 nm, as well as those of one-dimensional (1D) self-assembled NCs consisting of these NPs. NCs consisting of 100-nm diameter NPs switched through a transverse domain wall-like motion. Meanwhile, in 200-nm diameter NPs and NCs, we observed 3D magnetic vortex states that were more energetically favorable than single domain or multidomain states.