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Abstract: Based on the three-dimensional micromagnetic simulations, we present a method to tailor the microwave permeabilities of magnonic metamaterials cells by a designed nanoring structure. The results show that the permeabilities and resonant frequency are depended on the wallʼs thickness of nanorings. The underlying mechanism is ascribed to the presence of strong demagnetization fields, which are associated to the ringʼs wall. In addition, the products of magnetic susceptibility and resonant frequency are larger than that predicted from Snoekʼs law in polycrystalline particles. These results are direct manifestations of the bi-anisotropy model. [Copyright &y& Elsevier]

Abstract: Ag-rich Ag–Pd–Pt nanoframes and their dealloyed nanoframes were compared successfully as catalysts in oxygen reduction reaction (ORR). Supported by electrochemical quartz crystal microbalance results, the dealloying process was complete and a Pd–Pt-rich surface for the ternary nanoframes was obtained by a cyclic voltammetric method in 0.5M H2SO4 electrolyte after the second cycle. Comparing the data of mass activity analyses in 1M NaOH electrolyte showed that the ternary catalysts without dealloying can show faster kinetics in ORR. [Copyright &y& Elsevier]

Abstract: The effects of a special topological transformation on the energy levels, far-infrared spectra and magnetization of one electron inside a semiconductor nanoring under magnetic fields are studied. We have called this transformation as bipartition, and it is defined by a change in ring topological structure, when its shape is changed successively from a single oval-shaped loop up to quasi-two disconnected loops. Our results show that in the course of such transformation the low-lying energies dependencies with multiple crossovers between them, typical for the free electron rotation along an almost circular loop, are converted into a set of non-crossing double plaits related to a sub-barrier electron tunneling along a strongly non-circular loop in a quasi-local state. Also, we find that during the restructuring of the oval-shaped nanostructures the selection rules for the dipole transitions are changed allowing the appearance of additional peaks in the FIR spectrum. [Copyright &y& Elsevier]

We present detailed experimental and numerical studies of plasmonic properties of gold nanoring (NR) arrays with different slab thicknesses from 15 to 125 nm. The hybrid plasmon resonances for the bonding and antibonding modes in gold NRs exhibit a high slab thickness dependence behavior in optical properties. For the thinner slab thickness below 50 nm, both hybrid modes show large spectral tunabilities by varying the slab thickness. Furthermore, for such hollow NR structure, the enhancements of electric field intensities at the inner and outer ring surfaces when reducing the slab thickness are investigated. We observe a significant transition of field distributions for the antibonding mode. All these features can be understood by surface charge distributions from our simulations. The results of this study offer a potential strategy to design a composite plasmonic nanostructure with large field enhancement for numerous applications. [ABSTRACT FROM AUTHOR]

Cobalt Ferrite (CoFe2O4) nanorods and nanorings have been successfully controllable synthesized by solvothermal method. The specific characteristics were confirmed by X-ray diffraction studies (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The measurement of their electrochemical properties as supercapacitor electrode materials indicate different morphological characterizations have various capacitive effects, and CoFe2O4 nanorings generally have larger specific capacitances than nanorods at different scan rates and current densities in 1.0 M KOH solution. [ABSTRACT FROM AUTHOR]

In the present paper, we have utilized Au nanoring arrays in an SiO2 host to provide a T-structure for the purpose of routing and switching optical energy in optical integrated devices to operate at optical communication band (λ ≈ 1550 nm). To employ this router at spectral region considered, localized surface plasmons resonance (LSPR) must be red-shifted around 1550 nm. This T-shaped router includes Au nanorings with a 175 nm inner diameter, a 35 nm thickness and a 35 nm height, and the intercenter distance between two nanorings is 330 nm. To demonstrate the routing properties, we utilized the finite-difference time-domain (FDTD) method. It is shown that the non-straight chain can transport and route the optical energy with certain velocity of light and transmission coefficient. In addition, the percentage of transmitted or power ratio for this structure has been calculated as almost 90%. The optical energy transport can take place at group velocity of approximately 25% of the velocity of light (0.25c0, where c0 is the velocity of light in the vacuum). The router based on nanoring chains shows better performance in switching and transporting the optical energy in comparison to other nanoparticles (nanospheres, nanodisks and nanorods). [ABSTRACT FROM AUTHOR]

Abstract: Optical properties of a nanoring with Winternitz–Smorodinsky confinement potential in the presence of an external magnetic field have been studied theoretically. Our results demonstrate that energy, oscillator strength and the linear, nonlinear and total absorption are strongly affected by size of the nanoring. Also, we found that magnetic field has little influence on energy difference, oscillator strength and optical absorption of the nanoring. [Copyright &y& Elsevier]

On the basis of the growth mechanism of a GaAs/InAs nanoring, we propose a fine model which reflects the confinement details of real nanoring. Through calculations of the two-electron energy and far-infrared (FIR) spectra, we find that the ring topological structure and electron-electron interaction have great influence on the FIR spectra. The two unknown transition peaks in the experiment are determined theoretically. The theoretical results are in good agreement with the experiments. [ABSTRACT FROM AUTHOR]

Novel β-BiO crystals with nanoring and nanoplate surperstructures, which are composed of porous nanoparticles with mean pore diameter of 8 nm, were produced via a facile soft chemistry route of solvent refluxing technique. Most of the rings have the average inner diameter of 200 nm and the mean rim thickness of 20 nm. Photoluminescence spectra of the nanorings at room temperature were investigated, which demonstrated that the rings presented excellent optical properties. The influence of aging time on the morphology and structure of β-BiO superstructures was also studied, indicating that the nanoring superstructures transformed into nanoplates after a long aging time. The formation mechanism of the β-BiO superstructures was also explored. This approach will be further extended to solvent-controlled fabrication of related oxides with novel complex superstructures. [ABSTRACT FROM AUTHOR]

Nanoring magnetic tunnel junction (NR-MTJs) with outer diameter of 90 nm, and nanoelliptical ring (NER) -shaped MTJ with major outer diameter of 120 nm, and minor outer diameter of 70 nm were fabricated. For both geometrical structures, the ring width was kept at around 30 nm. The magnetic field driven and current-induced magnetization switching of the NR-MTJs and NER-MTJs were investigated. Compared with the NR-MTJs, the NER-MTJs show a sharp magnetization switching and lower coercivity under the sweep of an external magnetic field, which indicates the higher uniaxial anisotropy of NER-MTJs. In addition, the current-induced magnetization switching was achieved in both MTJs which indicated a lower critical current density in sandwiched-type and spin-valve-type NER-MTJs. This reduction of critical current could be resulting from different distribution of current-induced Oersted field in the NR-MTJs and NER-MTJs, which play an assisted role in spin transfer torque switching. This work proposes the NER-MTJs with the low current density, and small stray field, as data storage bits of magnetic random access memory (MRAM), could be a promising candidate for further reducing the power consumption, scaling memory cell size and increasing density of MRAM. [ABSTRACT FROM AUTHOR]

We study the thermal stability and morphological variations of nanorings with different radii during the temperature elevation using the molecular dynamics (MD) simulation method. Five metastable nanorings were generated using the different initial C-C bond length of armchair carbon nanotubes. The stable structures of the two smallest nanorings have several kinked regions around the nanorings, with the deformations of the inner and outer walls occurring at the same temperature. For the largest three cases, the morphologies of nanorings from the top view display circular shapes at 0 K. For the nanoring with a radius of 146 Å(350 units), the thermal deformation process is very similar to the smallest two cases, but the temperature at which the thermal deformation begins is higher. For the nanoring with nanoring radii of 165 Å (400 units) and 185 Å (450 units), thermal deformation will take place at the inner wall of the nanoring, and then will induce deformation of the outer wall at a higher temperature. Variations of local structures at the kinked regions at different temperatures are also drawn. [ABSTRACT FROM AUTHOR]

In this paper, a facile, one-step hydrothermal method for synthesis of Co(OH) nanodisks and nanorings without using any surfactants is reported. As-prepared samples were thoroughly characterized and analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), etc. The results showed that the size of as-prepared Co(OH) nanodisks could be determined by controlling the concentration of NaOH (8-16 mM) while maintaining other reaction conditions (such as temperature, reaction time, and solution compositions) unchanged. Furthermore, hexagonal nanorings could be obtained by changing the molar ratio between Ni and Co precursors. [ABSTRACT FROM AUTHOR]

This paper presents studies of the size effect on magnetic switching and interlayer magnetostatic coupling in synthetic antiferromagnet (SAF)-pinned spin-valve nanorings connected to nano stripes with a nanoconstriction. Micromagnetic simulation has been successfully used to reveal the detailed magnetization reversal process of these nanorings. It was observed that SAF-pinned spin-valve nanorings exhibit a double (onion—vortex—reverse onion) or single (onion—reverse onion) magnetization switching process depending on the ring diameter, which is contrary to narrow single-layer NiFe rings that show a double switching process only. Micromagnetic simulations of the SAF-pinned spin valve nanorings suggest that the magnetostatic coupling between the pinned layers of the SAF and the free layer is dependent on the ring size: it plays a very important role in the magnetization switching of small nanorings (600 nm outer diameter), but only a minor role in the switching of big nanorings (1600 nm outer diameter). An efficient reduction of the magnetostatic interaction results in a small shift of the minor magnetoresistance curve, which is beneficial to the magnetic memory applications. [ABSTRACT FROM AUTHOR]

Abstract: This work is the first step towards proving that general planar polygonal networks can be constructed as patterns of carbon nanotubes. A subset of the planar polygonal networks, namely the trivalent planar networks, are studied. These patterns can be constructed from carbon nanotubes such that every intersection point of the networks is replaced with a carbon nanotube Y-junction. Accordingly the basic task is to show the basic connections of the carbon nanotube Y-junctions. The basic set of connected Y-junctions is defined and models of the structures are shown. Nanorings with two, three or more branches are constructed from two, three or more Y-junctions such that two tubes of every Y-junction are joined to the neighbouring tubes with the third tube being free. Because of the known, exceptional electronic behaviour of carbon nanotubes, combinations of basic elements of planar nanotube networks could motivate new experimental and theoretical works having the goal of finding the basic electronic tools for nanocircuits. [ABSTRACT FROM AUTHOR]

Carbon-nitrogen nanorings with formulae (CN) and in the form of [ n]pyrazine cyclacenes appear either as closed-shell singlets (S) for n = 5, 10, and 12, or open-shell singlets (S) for n = 6, 7, 9, and 11 at restricted and unrestricted broken spin-symmetry density functional theory (DFT). All of their corresponding acyclic isomers, which are called [ n]pyrazine polyacenes or nanoribbons, appear as S for n = 5-12. As a result, nitrogen substitutions alter the electronic ground state of cyclacenes and polyacenes and appear to increase their viability, which invites further experimental and theoretical realization and exploration. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: The electronic structure of the conduction and valence bands of a quantum ring containing a layer inside the ring opening is modeled. This structure (nanocup) consists of a GaAs nanodisk (the cup’s bottom) and a GaAs nanoring (the cup’s rim) which encircles the disk. The whole system is embedded in an (Al,Ga)As matrix, and its shape resembles realistic ring structures grown by the droplet epitaxy technique. The conduction-band states in the structure are modeled by the single-band effective-mass theory, while the 4-band Luttinger–Kohn model is adopted to compute the valence-band states. We analyze how the electronic structure of the nanocup evolves from the one of a quantum ring when the size of either the nanodisk or the nanoring is changed. For that purpose, (1) the width of the ring, (2) the disk radius, and (3) the disk height are separately varied. For dimensions typical for experimentally realized structures, we find that the electron wavefunctions are mainly localized inside the ring, even when the thickness of the inner layer is 90% of the ring thickness. These calculations indicate that topological phenomena, like the excitonic Aharonov–Bohm effect, are negligibly affected by the presence of the layer inside the ring. [ABSTRACT FROM AUTHOR]

Abstract: Dynamic susceptibility spectra of the vortex state in nanorings and nanodots are studied using three-dimensional micromagnetic simulations. Spatial maps of the susceptibility have enabled identification of various resonance modes. For an exciting field along the x axis, several resonance peaks appear for a thin dot, including a core mode, whereas only one main resonance peak is detected for a ring corresponding to a volume mode with uniform magnetization perpendicular to the exciting field (x direction). A low-frequency resonance peak related to a surface mode and a high-frequency resonance peak viewed as an edge mode are additionally observed for a thick ring. These three resonance modes (surface, volume and edge modes) which correspond to low, intermediate and high-frequency resonance peaks, respectively, are also captured for an exciting field along the y axis. In addition, a mixed edge and volume mode is revealed at a higher frequency. [Copyright &y& Elsevier]

Abstract: Semiconducting zinc oxide nanowires (NWs) and nanobelts (NBs) are a unique group of quasi-one-dimensional nanomaterial. This review mainly focuses on the rational synthesis, structure analysis, novel properties and unique applications of zinc oxide NWs and NBs in nanotechnology. First, we will discuss rational design of synthetic strategies and the synthesis of NWs via vapor phase and chemical growth approaches. Secondly, the vapor–solid process for synthesis of oxide based nanostructures will be described in details. We will illustrate the polar surface dominated growth phenomena, such as the formation of nanosprings, nanorings and nanohelices of single-crystal zinc oxide. Third, we will describe the unique and novel electrical, optoelectronic, field emission, and mechanical properties of individual NWs and NBs. Finally, we will illustrate some novel devices and applications made using NWs as ultra-sensitive chemical and biological nanosensors, solar cell, light emitting diodes, nanogenerators, and nano-piezotronic devices. ZnO is ideal for nanogenerators for converting nano-scale mechanical energy into electricity owing to its coupled piezoelectric and semiconductive properties. The devices designed based on this coupled characteristic are the family of piezotronics, which is a new and unique group of electronic components that are controlled by external forces/pressure. [Copyright &y& Elsevier]

[Display omitted] • Two-step preparation of a core@shell (Fe@Fe x O y) nanotube system allows the tunning of the metallic iron and iron oxide phases. • The Fe@Fe x O y nanotubeś magnetic saturation can adjust for a desirable application by varying the synthesis conditions. • The Fe@Fe x O y nanotubes have a vortex state, which guarantees low remanence and coercivity. • Fe@Fe x O y nanotubes present good biocompatibility for two cells line: HEK and SAOS2. Iron oxide (maghemite and magnetite) nanoparticles are the most commonly used magnetic materials in nanomedicine because of their high biocompatibility. However, their low saturation magnetization (60–90 emu/g) limits their applicability. Here, we report a new core–shell (Fe@Fe x O y) nanoring system, which combines the high magnetic saturation of a metallic iron core (220 emu/g) and the biocompatibility of an iron oxide shell. To produce these nanostructures, hematite (α-Fe 2 O 3) nanorings were annealed in a H 2 gas atmosphere for different periods to optimize the amount of metallic iron percentage (δ) in the system. Thus, nanostructures with different magnetic saturation (97 to 178 emu/g) could be obtained; based on their metallic iron content, these particles are labeled as Vortex Iron oxide Particle δ (VIPδ). Micromagnetic simulations confirmed that the VIPδ nanorings exhibit a vortex configuration, guaranteeing low remanence and coercitivity. Moreover, the system shows good biocompatibility in various assays as determined through cell viability measurements performed using two different human cell lines, which were exposed to VIP78% for 24 h. Therefore, VIPδ nanorings combine a magnetic vortex state and biocompatibility with their high magnetic saturation and can thus serve as a platform that can be tuned during the synthesis based on desired biomedical application. [ABSTRACT FROM AUTHOR]

ZnO nanorings were synthesized on a large scale by an easy solution-based method at 70°C for 5 h using hexamethylenetramine (C6H12N4, HMT) and Zn (NO3)2·2H2O as raw materials in the presence of surfactant poly(acrylamide- co-diallyldimethylammonium chloride) (PAM-CTAC). The structure and morphology of the products were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The influence of experimental conditions such as concentration of surfactant and reactants, reaction temperature on the structure and morphology of the products were investigated. A probable formation mechanism of ZnO nanorings in the presence of surfactant PAM-CTAC was discussed. The results show that the products are wurtzite hexagonal ZnO nanorings with an inner diameter of 220 nm and a wall thickness of 70 nm. Reaction temperature and concentration of reactants influence the shape and size of ZnO nanorings but PAM-CTAC plays the key role in the formation of ZnO nanorings. Through adjusting the concentration of PAM-CTAC, controlled-synthesis of ZnO nanorings can be realized. A room temperature photoluminescence (PL) spectrum of ZnO obtained shows that the full width at half maximum (FWHM) of the UV emission (∼7 nm) is much narrower than that of commercial ZnO bulk crystals (∼18 nm). The narrow FWHM confirms the uniformity and narrow size distribution of the synthesized ZnO crystals. [ABSTRACT FROM AUTHOR]

Frontispiece: How Aromatic Are Molecular Nanorings? Keywords: aromaticity; delocalization error; nanoring EN aromaticity delocalization error nanoring 1 1 1 10/27/21 20211102 NES 211102 B Aromaticity b In their Research Article on page 24080, Eloy Ramos-Cordoba, Miquel Torrent-Sucarrat, Eduard Matito et al. present a computational study of a six-porphyrin nanoring structure and provide evidence that the molecule is not aromatic. Aromaticity, delocalization error, nanoring. [Extracted from the article]

Abstract: Several nanostructures composed of fine ZnS nanoparticles was prepared at the air–water interface via reactions between Zn2+ and H2S under monolayers of 5,10,15,20-tetra-4-oxy(2-stearic acid) phenyl porphyrin (TSPP) at room temperature and characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–vis and fluorescent spectroscopy. It was found that networks and round rings were formed under different conditions, and belts appear in the pores of the networks. After ripening at 60°C, the belts preserve with improved crystallinity of the nanoparticles. After treated at 300°C, the belts preserve, too. The formation of the rings at room temperature should be attributed to the templating effect of liquid films formed by TSPP molecules at the interface, the formation of the belts should be attributed to the attachment of the cubic zinc blende ZnS nanoparticles possibly under the direction of linear supramolecules of TSPP. [Copyright &y& Elsevier]

Abstract: Gold nanorings were prepared at the air/water interface through reduction of AuCl4 − ions by UV-light irradiation or formaldehyde gas treatment at room temperature templated by thin films of phthalocyanine derivatives. Silver nanorings were produced at the air/water interface via reduction of Ag+ ions by UV-light irradiation templated by poly(9-vinylcarbazole) (PVK) thin films. These nanostructures were investigated by transmission electron microscopy (TEM), selective-area electron diffractometry (SAED), and high-resolution TEM (HRTEM). It was found that the gold nanorings are composed of close-packed nanoplates whose (110) crystal planes are parallel to the air/water interface; while silver rings are composed of nanoparticles. It is demonstrated that the ring-like aggregates formed by parallel linear supramolecules of the phthalocyanine derivatives and the ring-like structure of PVK supramolecules are responsible for the formation of the gold and silver nanorings, respectively. [Copyright &y& Elsevier]

Abstract: Nanoparticles self-assembled into ring-shaped aggregates that were arranged in a two-dimensional (2D) hexagonal pattern. This hierarchic pattern was prepared by casting a toluene solution composed of polystyrene (PS) and Ag nanoparticles (NP). Dewetting of the thin composite layer induced the mesoscopic hexagonal array of PS–NP droplets. Within each dried droplet (dot), Ag nanoparticles self-assembled into a spot- or a ring-shaped 2D superlattice alternatively depending on the size of the dot, which was controlled by the molecular weight of PS. [Copyright &y& Elsevier]

Abstract: We report a new technique for fabricating metal nanoring array. In the process, a Cr nanodisk array was first formed by evaporating Cr onto the bottom of a 200nm period hole array having large undercut. The hole array was produced by NIL and RIE pattern transfer in a polymer sandwiched between a thin SiO2 and Si layer, which were stacked on a second polymer layer; and the undercut was formed by excessive polymer RIE. The thin Si surrounding the Cr disk was subsequently etched through by SF6 RIE, resulting in a ring-shaped hole structure in Si. After removing SiO2 and the first polymer layer and etching through the second polymer layer, a metal ring array was created by standard evaporation and liftoff. As examples, we fabricated Cr nanoring array with height 15nm, inner diameter 70–120nm and ring-width down to 22nm. We have found that, for a fixed hole diameter, the ring-diameter is strongly dependent on the hole depth. The ring symmetry and the wafer edge effect are discussed. The process can certainly be extended to metals other than Cr. Compared to previous methods, the current one is simpler, less costly and more suitable for narrow ring fabrication, though it suffers from reduced ring symmetry. However, asymmetric (nonconcentric) nanoring could be desirable for magnetic data storage and plasmonic devices. [Copyright &y& Elsevier]

Exact solution for two spatially separated particles in two coaxial one-dimensional nanorings has been obtained by using trigonometric sweep method. The structure of the energy spectrum of two electrons and electron-hole pair in nanoring with different sizes has been calculated. The comparative analysis of the quantum size effect on the energy levels in the case of the electron-hole attraction and the electron-electron repulsion is presented. As the radii of coaxial rings merge our results coincide with those obtained previously for one-dimensional nanoring. [ABSTRACT FROM AUTHOR]

Abstract: Various types of inorganic nanostructures including one-dimensional and nanocircle structures are prepared via simple solution mixing reaction. As confirmed by atomic force microscope (AFM) and transmission electron microscope (TEM), one-dimensional iron nanostrucutres with 1–10nm in diameter as well as nanocircle with ca. 10nm of inner diameter are spontaneously formed upon mixing and shaking of aqueous solution of FeCl3 with ethanol followed by addition of aqueous hydroxylamine solution. Autogenerated nano-, mirco-sized air bubbles during the mixing of aqueous FeCl3 solution and ethanol are believed to play a critical role for the formation of nanostructures. [Copyright &y& Elsevier]

A one-dimensional wave equation for low-lying energy levels of hydrogenic donors located inside or outside of a very narrow nanoring is derived. It is solved numerically by using the trigonometric sweep method. Calculation results of the energies for several D0 low-lying energy levels as functions of the distance from the impurity to the symmetric axis for different ring thicknesses are presented. [ABSTRACT FROM AUTHOR]