Nanoscale Subunits Research Articles

Synthesis of Ti-Ni and Zr-Ni Core–Shell Particles Using Galvanic Replacement

This article focuses on the galvanic replacement synthesis of Ti-Ni and Zr-Ni metal systems with a “core-shell” structure, which are potential precursors for intermetallics. The authors defined effective synthesis parameters and formation features of polymetallic systems characterized by granulometric, phase, and elemental composition. X-ray fluorescence and X-ray phase analysis methods showed that the deposition of nickel on dispersed titanium and zirconium leads to the production of test samples with phase composition representing a mechanical mixture of Ni and Ti, and Ni and Zr. The method of X-ray fluorescence analysis showed that the presence of hydrofluoric acid with a 0.5-1.5 M concentration results in the formation of fixed quantitative ratios of elements in the precipitate, which allows the quantitative composition of dispersed systems “titanium-nickel” and “zirconium-nickel” to be regulated within a relatively wide range. Scanning electron microscopy proved that all synthesized systems are characterized by a highly porous structure that follows the titanium and zirconium particle surface contour and the presence of spherical nanoscale subunits on the formed particle surface.

Mixed-valence realizations of quantum dot cellular automata

This article reviews recent progress in the design and theoretical investigation of molecular implementations of quantum-dot cellular automata (QCA) for field-coupled nanocomputing applications. QCA is a classical computing paradigm based on Coulombic quantum interactions between nanoscale subunits consisting of two or more quantum dots. Shrinking these dots to the molecular scale maximizes device density and permits operation at ambient temperatures. The essential feature of molecular QCA systems is the presence of two or more coupled redox centers separated by spacers. In this work candidate systems ranging from simple organic molecules to self-assembled multi-center mixed-valence organometallic complexes are surveyed, and some of the challenges remaining to be faced both in theoretical understanding and practical implementation are discussed.

Tunable Synthesis of Hematite Structures with Nanoscale Subunits for the Heterogeneous Photo-Fenton Degradation of Azo Dyes

Facile syntheses of branched hematite (α-Fe2O3) crystals with fine-tuning of their nanoscale subunit morphologies were reported. Starting from Prussian red and bisolvent systems with controlled temperature as the crucial parameters, fine-tuning of the nanoscale subunit morphologies in the context of controlling the anisotropic growth of branched α-Fe2O3 crystals was demonstrated. The systematic and optimized studies significantly improved the controlled synthesis of the hierarchical growth of nanoscale subunits, leading to the formation of branched dendritic leaflike (secD3D, tertD2D, and tertD3D) and hyperbranched (secS2D and hypB2D) α-Fe2O3 particles for their size-reduced variants used in photocatalysis. The kinetics of the photo-Fenton degradation of three azo dyes (chlorazol black, direct blue, and methyl orange) with five types of branched dendritic α-Fe2O3 particles were compared systematically.

Hierarchically Nanostructured ZnO with Enhanced Photocatalytic Activity

Hierarchical nanostructures of ZnO are integrated architectures comprising well-ordered nanoscale subunits and excellent photocatalytic properties. In this study, synthesis of ZnO nanoparticles using methods such as co-precipitation, hydrothermal, thermal decomposition, and electrochemical precipitation yielded microsphere, nanorod, pyramid, and nanopetal-like morphologies, respectively. The catalysts obtained were characterized using XRD, IR, SEM-EDX, UVDRS, TGA, PL, and Zeta potential analysis. The XRD spectra confirmed that all the different morphologies of ZnO have hexagonal wurtzite structures The photocatalytic activity of these nanostructures was determined using a dye degradation study on a model pollutant Methylene Blue (MB) under simulated visible light. The kinetic study of the dye degradation reveals that it obeys pseudo-first-order kinetics with a maximum rate constant of 0.01503 min−1. The nanorod structured ZnO particles prepared by the hydrothermal method showed the best catalytic activity.

FRET-enabled monitoring of the thermosensitive nanoscale assembly of polymeric micelles into macroscale hydrogel and sequential cognate micelles release.

Thermosensitive "micellar hydrogel" is prepared based on poly(ε-caprolactone-co- 1,4,8-trioxa[4.6]spiro-9-undecanone)-b-poly(ethylene glycol)- b-poly(ε-caprolactone- co-1,4,8-trioxa[4.6]spiro-9-undecanone) (PECT) triblock copolymer. Fluorescence resonance energy transfer (FRET) is adopted to explore its assembly (formation) and disassembly (degradation) mechanism within the range of 10nm. Results prove that the thermosensitive non-covalent aggregation of micelles facilitates the hydrogel formation and the sustained shedding of cognate micelles induces the hydrogel degradation, during which polymers are steadily incorporated in micelles without any micelle disassembly or reassembly. It is confirmed that using multiple-tags based imaging technology, such as FRET imaging, the fate of macro biodegradable materials invitro and invivo can be followed at a precise nano even molecular level. Such an unique hydrogel composed of nothing more than PECT micelles can act as not only an injectable nanomedicine reservoir by subcutaneous or peri-tissue administration, but also an advanced "combo" macroscale platform for co-delivery of multi-modal therapeutic agents. Our findings also indicate that biological stimuli (e.g., temperature, enzymes)-induced non-covalent micelle self-assembly may provide us an effective strategy to prepare a macroscale device from nanoscale subunits.

Hierarchically porous TiO2-MnTiO3/hollow activated carbon fibers heterojunction photocatalysts with synergistic adsorption-photocatalytic performance under visible light

An ideal photocatalysts is expected to not only involve nanoscale subunits with high catalytic activity, but also possess a 3D hierarchically porous microstructure to obtain more activated sites as well as easy recovery. Herein, we demonstrated an efficient route to synthesize self-support hierarchically porous TiO2-MnTiO3/HACFs (hollow activated carbon fibers) heterojunction photocatalysts with tunable band gaps by a facile biotemplated method. The heterojunctions with suitable TiO2/MnTiO3 ratios on HACFs supports had fascinating 3D hollow fiber morphology and exhibited exceptionally synergistic adsorption-photocatalytic activities in visible-light degradation of methylene blue (MB). The photocatalytic degradation rate of MB could reach 99.1% in 60 min under visible light irradiation and cycled experiments showed stably photocatalytic activities. The enhanced photocatalytic performance could be attributed to the high efficiency of electron separation, the high specific surface area and strong adsorption ability toward the MB molecule, and the tunable visible light absorption of TiO2-MnTiO3/HACFs.

Static and Dynamic Magnetic Properties of Ferromagnetic Cobalt Particles Containing Nanoscale Subunits

In this work, cobalt micro-particles containing various nanoscale subunits were hydro- thermally synthesized and controlled by the content of sodium tartrate in reaction solution. Both the static and dynamic magnetization properties of cobalt particles changes accordingly. As the content of sodium tartrate varies from 0 g, 0.552 g to 4.416 g, subunits of the cobalt particles shrinks from dendrites, coralloids to small bumps, saturation magnetization changes from 122.5 emu/g, 86.5 emu/g, to 95.79 emu/g, and the coercive force reduces from 195 Oe, 148 Oe, to 62 Oe. Consequently, ferromagnetic resonance bandwidth of the cobalt particles decreases due to the diminishing surface scatterers (subunits), whereas low frequency loss tangential increases following the growth of spherical particle core. The proposed cobalt particles with nanoscale subunits shows potential for electromagnetic wave absorption and shielding application.

UV-assisted, template-free synthesis of ultrathin nanosheet-assembled hollow indium oxide microstructures for effective gaseous formaldehyde detection

Hollow micro-/nanostructures, especially those with well-defined nanoscale subunits, have been widely used in a variety of areas including catalysis, sensing, energy storage, drug delivery, etc. Herein, we report a novel, UV-assisted, template-free synthesis of hollow indium oxide microstructures that are composed of ultrathin nanosheets (∼2.5nm). The two key steps for the synthesis of the materials being successful are: (i) the UV-induced conversion of a photoactive solid indium alkoxide precursor into hollow indium hydroxide microspheres composed of ultrathin nanosheets, and (ii) the thermal treatment of the resulting hollow hydroxide microspheres into the hollow In2O3 material with a morphological preservation. Moreover, we show that the as-obtained hollow nanomaterials exhibit excellent sensing performance (e.g., high response value, good stability, as well as fast response speed) for the detection of ppm-level gaseous formaldehyde. The efficient sensing performance of the material is attributed to their overall conducive structural features, including their hollow architecture and ultrathin nanoscale building blocks. These structural features can offer a large amount of active sites on the surface, facilitate the diffusion and adsorption of the target gas, and thus enhance the material's sensing performance.

Hierarchical Porous ZnMn2 O4 Hollow Nanotubes with Enhanced Lithium Storage toward Lithium-Ion Batteries.

We have purposefully developed a smart template-engaged methodology to efficiently fabricate well-defined ternary spinel ZnMn2 O4 hollow nanotubes (NTs). The procedure involves coating carbon nanotubes (CNTs) with ZnMn2 O4 nanosheets (NSs), followed by heating at high temperature in air to oxidize the CNT template. Physicochemical characterization demonstrated that the formed ZnMn2 O4 NTs with a diameter of approximately 100 nm were composed of assembled NSs and/or nanoparticles (NPs) as building blocks and possessed numerous nanopores of several nanometers in the sidewall of the NTs. In favor of the intrinsic structural advantages, the resulting ZnMn2 O4 NTs exhibited superior electrochemical lithium-storage performance with a large capacity, good rate behavior, and excellent cyclability when evaluated as promising anodes for lithium-ion batteries (LIBs). The remarkable electrochemical performance was rationally ascribed to the appealing one-dimensional (1D) porous hollow tubular architecture with nanoscale subunits and mesopores in the sidewalls, which decreased the diffusion length for the Li(+) ions, improved the kinetic process, and enhanced the structural integrity with sufficient void space to tolerate the volume variation during Li(+) -ion insertion/extraction. These results highlight the promising application of 1D ZnMn2 O4 NTs as anodes for high-performance LIBs.

Template‐Free Fabrication of Mesoporous Hollow ZnMn2O4 Sub‐microspheres with Enhanced Lithium Storage Capability towards High‐Performance Li‐Ion Batteries

In this work, we rationally designed an efficient template‐free synthetic strategy to fabricate hierarchical mesoporous hollow ZnMn2O4 sub‐microspheres (HZSMs) constructed entirely from nanoparticle (NP) building blocks of size ≈15 nm. The well‐known inside‐out Ostwald ripening process was tentatively proposed to shed light on the formation mechanism of the mesoporous hollow nano‐/microarchitecture. In favor of the intrinsic structural advantages, these resulting HZSMs exhibited superior electrochemical lithium‐storage performance with high specific capacity, excellent cyclability, and good rate capability when evaluated as an anode material for advanced Li‐ion batteries (LIBs). The excellent electrochemical performance should be reasonably ascribed to the porous and hollow structure of the unique HZSMs with nanoscale subunits, which reduced the diffusion length for Li+ ions, improved the kinetic process and enhanced the structural integrity with sufficient void space for tolerating the volume variation during the Li+ insertion/extraction. These results further revealed that the as‐prepared mesoporous HZSMs would be a promising anode for high‐performance LIBs.

Controlled synthesis of three-dimensional CoNi microstructures composed of single crystal CoNi nanoleaves

Three dimensional (3D) alloyed micro- and nanostructures composed of nanoscale subunits with regular and novel morphologies have received intensive attention due to their interesting physicochemical properties and wide applications in different areas. In this study, 3D CoNi microstructures consisting of well-defined CoNi nanoleaves are synthesized by a complexant-assisted wet-chemical reduction process free of any surfactant or template, which is suitable for large scale production. Elemental maps obtained by X-ray energy-dispersive spectroscopy (EDS) indicate that Co and Ni elements are homogenously distributed in the microstructures, verifying that the sample is an alloy rather than a mixture of Co and Ni. High resolution transmission electron microscopy (HRTEM) images and the selected area electron diffraction (SAED) pattern demonstrate the nanoleaves in the 3D microstructures are single crystals. Magnetic measurements at room temperature revealed that the as-prepared 3D CoNi microstructures exhibit a ferromagnetic property with a coercivity of 197.4 Oe, which is much higher than that of many CoNi micro- and nanostructures reported in recent literature. Based on the evolution of the morphology of the products with increasing reaction time, a possible formation mechanism is proposed to illustrate the growth of the CoNi microstructures.

Interactions between a Solid Spherical Particle and a Chemically Heterogeneous Planar Substrate

The Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction forces between a chemically heterogeneous substrate and a spherical particle approaching the surface are calculated using a simple model. This model decomposes the heterogeneous substrate into nanoscale subunits and applies a pairwise summation of forces between each subunit and the approaching particle to determine the net DLVO force. This approach leads to a three-dimensional description of the forces arising from the chemical heterogeneity of the surface. In this three-dimensional realm, we observe the emergence of a substantial lateral force at specific separation distances from the substrate. More specifically, the lateral forces become significantly larger than the normal forces at separation distances between those of the repulsive barrier and the secondary minimum of the DLVO interaction energy curve. These lateral forces are most pronounced at high electrolyte concentrations, particularly at biological salt concentrations of approximately 0.1 M. Furthermore, the lateral forces are found to be significantly higher when the particle is near the edge of a heterogeneous region of the substrate. On the basis of the evidence of this study, and depending on the characteristics of the system, both the physical roughness and the chemical heterogeneity of a surface can significantly affect how a particle will interact with it.