Network-like Architecture Research Articles

Facile one-step aqueous-phase synthesis of porous PtBi nanosponges for efficient electrochemical methanol oxidation with a high CO tolerance

• Facile, green, and templet-free approach is developed for one-step preparation of PtBi nanosponge. • PtBi nanosponges enhanced the methanol oxidation activity and stability than Pt and Pt/C. • The formation mechanism of PtBi nanosponges is attributed to oriented attachment growth. • PtBi nanosponges showed nanosponge structure with 3D interconnected pores. • PtBi nanosponges revealed high CO tolerance than Pt/C and Pt. Deliberate control in the composition and morphology of Pt-based catalysts is an efficient route for enhancing the methanol oxidation reaction (MOR). Herein we developed a facile method for rational one-step aqueous-phase synthesis of PtBi nanosponges with tunable composition, based on the prompt reduction of an aqueous solution of Pt and Bi precursors using NaBH 4 . Mechanistically, the high-reduction power of NaBH 4 formed multiple small colloidal PtBi nanocrystals (NCs), which coalesce together to reduce their interfacial energy resulting in oriented attachment growth. The fabrication process is simple, quick (2 min), productive, and free of surfactants or organic solvents. PtBi nanosponges showed 3D network-like architectures with a rough surface and interconnected pores (mesopore and macropore). The MOR mass (specific) activity of Pt 67 Bi 33 , 1.8 A/mg Pt (15.4 mA cm −2 ), outperformed Pt 78 Bi 22 , Pt, and Pt/C, by 2.3 (1.2), 4.8 (3.6), and 5.1 (24.7) times, respectively besides greater stability and CO tolerance. This method could be extended to synthesize other binary Pt-based catalysts for various electrocatalytic applications.

Synthesis of spherical Y2O3:Er emitting particles with variable radial composition by controlled double-jet precipitation of layered precursors

Spherical (Y0.98Er0.02)2(OH)5(NO3)·xH2O particles were synthesized by controlled double-jet precipitation, with a “core” of pure layered yttrium hydroxide nitrate, and a “shell” of co-precipitated yttrium-erbium layered hydroxide nitrates. With an increase in precipitation pH from 7 to 9.5, the size of layered “building units” decreases and the architecture of their assemblies changes from flower-like through network-like spherical to irregular agglomerates. From there, spherical particles gradually increase their diameter due to the continuous uniform growth of curved layered sheets on their surface. It was established that such growth behavior and network-like architecture of spherical particles was retained even when yttrium was replaced by erbium ions in the layered host lattice during the formation of an Er-enriched “shell”. Analysis of SEM, EDS, XPS, photoluminescence spectra and concentration quenching effects of heat-treated Y2O3:Er (2 at.%) particles indicate that the radial distribution of erbium in particles is most controllable in a narrow pH range of co-precipitation of layered precursors (pH 8). Вy widely varying the elemental composition of “building units” during co-precipitation, one can simultaneously finely control the composition of layered hydroxides in the radial direction of the spherical particles and grow multicomponent “multi-shell” powders with desired properties.

ChangeGAN: A Deep Network for Change Detection in Coarsely Registered Point Clouds

In this letter we introduce a novel change detection approach called ChangeGAN for coarsely registered point clouds in complex street-level urban environment. Our generative adversarial network-like (GAN) architecture compounds Siamese-style feature extraction, U-net-like use of multiscale features, and Spatial Trans-formation Network (STN) blocks for optimal transformation estimation. The input point clouds are represented by range images, which enables the use of 2D convolutional neural networks. The result is a pair of binary masks showing the change regions on each input range image, which can be backprojected to the input point clouds without loss of information. We have evaluated the proposed method on various challenging scenarios and we have shown its superiority against state-of-the-art change detection methods.

Post-transcriptional control of mitochondrial protein composition in changing environmental conditions.

In fluctuating environmental conditions, organisms must modulate their bioenergetic production in order to maintain cellular homeostasis for optimal fitness. Mitochondria are hubs for metabolite and energy generation. Mitochondria are also highly dynamic in their function: modulating their composition, size, density, and the network-like architecture in relation to the metabolic demands of the cell. Here, we review the recent research on the post-transcriptional regulation of mitochondrial composition focusing on mRNA localization, mRNA translation, protein import, and the role that dynamic mitochondrial structure may have on these gene expression processes. As mitochondrial structure and function has been shown to be very important for age-related processes, including cancer, metabolic disorders, and neurodegeneration, understanding how mitochondrial composition can be affected in fluctuating conditions can lead to new therapeutic directions to pursue.

Neural physical engines for inferring the halo mass distribution function

ABSTRACT An ambitious goal in cosmology is to forward model the observed distribution of galaxies in the nearby Universe today from the initial conditions of large-scale structures. For practical reasons, the spatial resolution at which this can be done is necessarily limited. Consequently, one needs a mapping between the density of dark matter averaged over ∼Mpc scales and the distribution of dark matter haloes (used as a proxy for galaxies) in the same region. Here, we demonstrate a method for determining the halo mass distribution function by learning the tracer bias between density fields and halo catalogues using a neural bias model. The method is based on the Bayesian analysis of simple, physically motivated, neural network-like architectures, which we denote as neural physical engines, and neural density estimation. As a result, we are able to sample the initial phases of the dark matter density field while inferring the parameters describing the halo mass distribution function, providing a fully Bayesian interpretation of both the initial dark matter density distribution and the neural bias model. We successfully run an upgraded borg (Bayesian Origin Reconstruction from Galaxies) inference using our new likelihood and neural bias model with halo catalogues derived from full N-body simulations. In preliminary results, we notice there could potentially be orders of magnitude improvement in modelling compared to classical biasing techniques.

Glycine-Induced Electrodeposition of Nanostructured Cobalt Hydroxide: A Bifunctional Catalyst for Overall Water Splitting.

Herein, an interconnected α-Co(OH)2 structure with a network-like architecture was used as a bifunctional electrocatalyst for the overall water splitting reaction in alkaline medium. The complexing ability of glycine with a transition metal was exploited to form [Co(gly)3 ]- dispersion at pH 10, which was used for the electrodeposition. High-resolution TEM, UV/Vis-diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy were used to confirm that the as-synthesized materials had an α-Co(OH)2 phase. The electrocatalytic oxygen and hydrogen evolution activity of the glycine-coordinated α-Co(OH)2 was found to be approximately 320 and 145 mV, respectively, at 10 mA cm-2 . The material required approximately 1.60 V (vs. reversible hydrogen electrode; RHE) to achieve the benchmark of 10 mA cm-2 for overall water splitting with a mass activity of approximately 63.7 A g-1 at 1.60 V (vs. RHE). The chronoamperometric response was measured to evidence the stability of the material for overall water splitting for up to 24 h. Characterization of the catalyst after the oxygen and hydrogen evolution reactions was performed by XPS and showed the presence of a CoII /CoIII oxidation state.

Interfacial Self-Assembly of Closely Packed Nanoparticle Arrays of Silica@Multiporphyrin Hybrids as Light-Sensitizers for Dye Degradation and Viologen Photochromism.

Light-sensitizer functionalized organic-inorganic hybrid materials have attracted much attention owing to their potential applications in the fields of optoelectronics, heterogeneous catalysis, sensors, and nanotechnology. Here, an interfacial self-assembly of zero-dimensional (0D) silica@multiporphyrin array nanohybrids and their 3D Langmuir-Blodgett (LB) films is reported. Photoactive tetrapyridylporphyrin (TPyP) was first assembled on the silica nanoparticles' surfaces via silane, substitution, and coordination reactions to produce nanoSiO2 @(Pd-TPyP)n hybrids. Then, the Cd2+ -nanoSiO2 @(Pd-TPyP)n monolayers and LB films were constructed on the CdCl2 subphase surface. These monolayers and LB films displayed stronger stability, as well as more uniform and closely packed nanoparticle arrays compared with those prepared on the pure water surface, owing to the formation of strong network-like Pd- and Cd-TPyP coordination units, which significantly enhanced the nanoparticles' interaction. Further, compared with that of the 0D nanoSiO2 @(Pd-TPyP)n hybrids, the degradation efficiency was nearly 20 times higher when the hybrids' LB films were used as light-sensitizers for the photocatalytic degradation of RhB. Finally, flexible photochromic devices were constructed by using the LB films sandwiched between two electrodes, which displayed a reversible photoinduced redox reaction of viologen together with a color change process. Because TPyP was strongly immobilized on the nanoparticles' surfaces and the particles were connected through the Py-Pd2+ -Py and Py-Cd2+ -Py coordination units with the 3D network-like architecture, the present nanohybrids and LB films had good stability and reusability.

Sub-10 nm porous alumina templates to produce sub-10 nm nanowires

Abstract The versatility of Anodic Aluminum Oxide has led to the development of a variety of templates with ranging sizes, periodic modulations, and network-like architectures. These templates allow for the nanostructuration and study of new meta-materials, with interesting and important properties enhanced through size-reduction effects. In this work, we further extend the utility of these templates through the use of current anodization in concentrated Sulfuric acid and 25% V/V of ethanol under low current density values, obtaining small pore architectures with sub-10 nm features. In addition, polymer infiltration was performed as a proof of concept application, resulting in 8 nm nanowires. The templates reduced sizes allow for their application in the search for stable, extremely small diameter nanowires, and also for their use as scaffolds or filters.

Bicontinuous Spider Network Architecture of Free-Standing MnCoO X @NCNF Anode for Li-Ion Battery.

Herein, a smart strategy is proposed to tailor unique interwoven nanocable architecture consisting of MnCoOx nanoparticles embedded in one-dimensional (1D) mesoporous N-doped carbon nanofibers (NCNFs) by using electrospinning technique. The as-prepared network mat of N-doped carbon nanofibers with embedded MnCoOx nanoparticles (MnCoOx@NCNFs) is tested as a current collector-free and binder-free flexible anode, which eliminates slurry preparation process during electrode fabrication in the Li-ion battery (LIB). The MnCoOx@NCNFs possess versatile structural characteristics that can address simultaneously different issues such as poor conductivity, low cycling stability, volume variation, flexibility, and binder issue associate with the metal oxide. The free-standing mat electrode shows not only high initial discharge and charge capacities but also reversible discharge cycling stability of almost 80% retention up to 100 cycles and 60% retention up to 500 cycles at 1.0 A/g. Such high Li storage capacity and excellent cycling stability are attributed to the unique flexible and free-standing spider network-like architecture of the 1D MnCoOx@NCNFs that provides the platform for bicontinuous electron/ion pathways for superior electrochemical performance. Along with excellent electrochemical performance, simple synthesis procedure of unique binder-free MnCoOx@NCNFs can achieve cost-effective scalable mass production for practical use in a flexible mode, not merely in LIBs but also in a wide spectrum of energy storage fields.

A novel organic-inorganic hybrid polyoxometalate-based 3D framework constructed by organo-functionalized [As2W21O72(mal)2]18 − units and Ce3 + ions

A novel organic-inorganic hybrid polyoxometalate-based 3D framework K5H4{Ce3(H2O)9[As2W21O72(mal)2]}·20H2O (1) (mal=malic acid) has been synthesized by the metastable precursor [As2W19O67(H2O)]14−, which was further characterized by IR spectrum, thermogravimetric analysis (TGA), and X-ray single-crystal diffraction. Structural analysis revealed that 1 consists of the organo-functionalized [As2W21O72(mal)2]18− units linked together by the Ce3+ ions resulting in 3D network-like architecture. Magnetic property studies indicate that obvious antiferromagnetic interactions exist in three Ce3+ ions.

3D network-like porous MnCo2O4 by the sucrose-assisted combustion method for high-performance supercapacitors

3D network-like porous MnCo2O4 nanostructures have been successfully fabricated through a facile and scalable sucrose-assisted combustion route followed by calcination treatment. Benefiting from its advantages of the unique 3D network-like architectures with large specific surface area (216.15m2g−1), abundant mesoporosity (2–50nm) and high electronic conductivity, the as-prepared MnCo2O4 electrode displays a high specific capacitance of 647.42Fg−1 at a current density of 1Ag−1, remarkable capacitance retention rate of 70.67% at current density of 10Ag−1 compared with 1Ag−1, and excellent cycle stability (only 6.32% loss after 3000 cycles). The excellent electrochemical performances coupled with facile and cost effective method will render the as-fabricated 3D network-like porous MnCo2O4 as a promising electrode material for supercapacitors.

Scalable, ultra-resistant structural colors based on network metamaterials

Structural colors have drawn wide attention for their potential as a future printing technology for various applications, ranging from biomimetic tissues to adaptive camouflage materials. However, an efficient approach to realize robust colors with a scalable fabrication technique is still lacking, hampering the realization of practical applications with this platform. Here, we develop a new approach based on large-scale network metamaterials that combine dealloyed subwavelength structures at the nanoscale with lossless, ultra-thin dielectric coatings. By using theory and experiments, we show how subwavelength dielectric coatings control a mechanism of resonant light coupling with epsilon-near-zero regions generated in the metallic network, generating the formation of saturated structural colors that cover a wide portion of the spectrum. Ellipsometry measurements support the efficient observation of these colors, even at angles of 70°. The network-like architecture of these nanomaterials allows for high mechanical resistance, which is quantified in a series of nano-scratch tests. With such remarkable properties, these metastructures represent a robust design technology for real-world, large-scale commercial applications.

Does mechanical stimulation really protect the architecture of trabecular bone? A simulation study.

Although it is beyond doubt that mechanical stimulation is crucial to maintain bone mass, its role in preserving bone architecture is much less clear. Commonly, it is assumed that mechanics helps to conserve the trabecular network since an "accidental" thinning of a trabecula due to a resorption event would result in a local increase of load, thereby activating bone deposition there. However, considering that the thin trabecula is part of a network, it is not evident that load concentration happens locally on the weakened trabecula. The aim of this work was to clarify whether mechanical load has a protective role for preserving the trabecular network during remodeling. Trabecular bone is made dynamic by a remodeling algorithm, which results in a thickening/thinning of trabeculae with high/low strain energy density. Our simulations show that larger deviations from a regular cubic lattice result in a greater loss of trabeculae. Around lost trabeculae, the remaining trabeculae are on average thinner. More generally, thin trabeculae are more likely to have thin trabeculae in their neighborhood. The plausible consideration that a thin trabecula concentrates a higher amount of strain energy within itself is therefore only true when considering a single isolated trabecula. Mechano-regulated remodeling within a network-like architecture leads to local concentrations of thin trabeculae.

Controllable synthesis of 3D NiχCo1−χ oxides with different morphologies for high-capacity supercapacitors

3D NiχCo1−χ oxides with different morphologies for high-capacity supercapacitors were controllably synthesized via an electrodeposition method combined with a simple post annealing process. The synthesis involves the co-electrodeposition of the bimetallic (Ni, Co) hydroxide precursor on a nickel foam scaffold and subsequent thermal transformation to NiχCo1−χ oxides. The crystalline structure, morphology and electrochemical performance of the 3D NiχCo1−χ oxides can be readily manipulated by simply varying the Co/Ni molar ratio in the electrodeposition electrolyte. With the increase of the Co/Ni molar ratio, the characteristic peak intensities and the signal sites were gradually changed from a NiO crystal dominant structure to NiCo2O4 and finally to a Co3O4 dominant structure. Moreover, the morphology also can be controlled by adjusting the Co/Ni molar ratio in the electrodeposition electrolyte. In addition, the Ni0.61Co0.39 oxide electrode shows a large specific capacitance of 1523.0 F g−1 at 2 A g−1 and 95.30% of that can be retained, even at a high current density of 30 A g−1. The superior rate capability should be attributed to the unique 3D network-like architecture, which can enlarge the liquid–solid interfacial area, facilitate the electron and ion transport, and further increase the utilization of the active material. To demonstrate its practical application, an asymmetric supercapacitor based on the Ni0.61Co0.39 oxide electrode as a positive electrode and activated carbon as a negative electrode was fabricated. Owing to the outstanding capacitive behavior of the Ni0.61Co0.39 oxide electrode, the asymmetric device delivers a prominent energy density of 36.46 W h kg−1 at a power density of 142 W kg−1, and which holds great promise for potential applications in energy storage.

Computer Models Describing Structural Changes in Living Bone on Two Different Length Scales

AbstractThe structure of living bone changes continuously due to the processes of bone remodeling and mineralization. This paper describes computational work, which addresses structural changes on two different length scales: on the millimeter length scale changes in the network-like architecture of so-called trabecular bone, and on the submillimeter scale changes in the heterogeneity of the bone material. The mathematical background of the models is described in detail, highlighting the model assumptions. A central question of the presented simulations is how the processes are controlled, e.g., by mechanical strains. The models are designed in such a way that the control part is not experimentally accessible, but the result of the simulations can be compared with experimental data.

Nano-structured CuO films prepared by simple solution methods: Plate-like, needle-like and network-like architectures

Two simple, safe and environmental friendly chemical solution methods which are suitable to mass production, applicable at low temperatures and cost effective, were used to prepare homogenous nano-structured cupric oxide (CuO) films. By using different types of substrates (glass, quartz, Cu foil and Si) and techniques various types of CuO nanostructures (plate, needle and network like) were produced. The products were characterized by scanning electron microscopy, X-ray diffraction and temperature dependant dark electrical resistivity measurements in order to investigate the effects of substrate on morphology, crystallographic structure and electrical properties of the films. From these characterizations it was seen that there are significant differences in the morphological, crystallographic, structural and electrical properties of the nanostructures that were produced by different techniques and/or on different substrates. Besides, growth mechanisms of CuO films have been investigated.

One Step Solvothermal Synthesis of Flower-Like β-In<sub>2</sub>S<sub>3</sub> Microstructures

Uniform 3D flower-like β-In2S3 microstructures were synthesized using InCl3·4H2O and KSCN as starting reagents in ethylene glycol at 200-220°C for 30h under solvothermal conditions. The prepared products were characterized by various techniques, such as XRD, XPS, FESEM, TEM and ED. FESEM and TEM observation reveals that the as-prepared flower-like β-In2S3 microstructures are assembled by plate-like nanocrystals with average thickness of 10nm. These nanoplates interconnect with each other to form an entangled network-like architecture with irregular-shaped pore in the flower-like β-In2S3 microstructures. Photoluminescence (PL) spectrum indicates that the synthesized β-In2S3 porous micro spheres have shown considerably greater quantum size effects.

Electrophoretic deposition of network-like carbon nanofiber as a conducting substrate for nanostructured nickel oxide electrode

A vapor-grown carbon nanofiber (VGCF) film with network-like architecture was fabricated by electrophoretic deposition (EPD) in the isopropanol suspension containing Ni(NO 3) 2 additive. Nickel ions adsorbed on the VGCFs increase the zeta potential of VGCFs, consequently, the EPD rate and nanofiber dispersion are remarkably improved. Nickel deposition is accompanied by reducing the nickel ions on the surface of VGCFs. Nickel appears to be suitable as a conducting metal binder for attaching the VGCFs. EPD of the nickel oxide on VGCF-coated film exhibits excellent capacitive behavior compared with that bare NiO electrode, resulting from the reduced electron conducting and charge-transfer resistances.

Facile Electrophoretic Deposition of Ni-Decorated Carbon Nanotube Film for Electrochemical Capacitors

Ni-decorated carbon nanotube (CNT) film of a networklike architecture has been formed on a stainless steel substrate by electrophoretic deposition (EPD) in CNT suspension containing nickel nitrate. Adsorption of nickel ions on the CNTs increases the measured zeta potential and consequently favors the dispersion and EPD of CNTs. Nickel ions are reduced on the CNT surface to form Ni-decorated CNT film in the EPD process. The deposited nickel layer plays an important role in improving the adhesion, wettability, and electrochemical reaction of the film. Therefore, the Ni-decorated CNT film exhibits an excellent capacitive behavior compared with the bare CNT film.

Fabrication of CuO film with network-like architectures through solution-immersion and their application in lithium ion batteries

A novel CuO negative electrode with network-like architectures was fabricated on copper substrate by a simple solution-immersion step and subsequent heat treatment, which avoids the use of binder and conducting agent that necessary to the conventional electrode-preparation process. The as-prepared CuO electrodes exhibit not only high reversible capacity but also long cycling life, high rate capability in Li ion batteries. The result of this approach creates a new and attractive negative electrode with good electrochemical performance, which is simple, mild conditions, low cost, and easy control. It also opens a pathway for the application of other nanostructured materials of transition metal oxides in lithium ion batteries.