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Monolayer-ordered gold nanoring arrays were prepared by ion-sputtering method and used as surface enhanced Raman spectroscopy (SERS) substrates to test the individual atmospheric aerosols particle. Compared to other methods used for testing atmospheric aerosols particles, the collection and subsequent detection in our work is performed directly on the gold nanoring SERS substrate without any treatment of the analyte. The SERS performance can be tuned by changing the depth of the gold nanoring cavity as originating from coupling of dipolar modes at the inner and outer surfaces of the nanorings. The electric field exhibits uniform enhancement and polarization in the ordered Au nanoring substrate, which can improve the accuracy for detecting atmospheric aerosol particles. Combined with Raman mapping, the information about chemical composition of individual atmospheric aerosols particle and distribution of specific components can be presented visually. The results show the potential of SERS in enabling improved analysis of aerosol particle chemical composition, mixing state, and other related physicochemical properties. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Preparing the low-cost nanomaterials for electrocatalytic processes is still a big challenge. Mesoporous cobalt hydroxide and cobalt oxide nanoparticles were prepared through simple soft chemistry as high-performance materials for durable electrocatalyst for OER and supercapacitive applications. The synthesis method is used to prepare nanoring particles in neither emulsion nor template-directed method. The final nanoparticles display mesoporous hexagonal nanoring morphology. The physio-chemical properties of the as-synthesized nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen adsorption-desorption techniques. The TEM characterizations prove that NPs retain the topotactical relationship in their structure during the conversion process. The BET measurements prove the mesoporous nature of the nanorings, having good specific surface area and pore volume. Finally, the electrochemical performance toward water splitting and supercapacitor applications were investigated by electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and cyclic voltammetry (CV) techniques. The Co 3 O 4 NPs exhibits better catalytic properties than Co(OH) 2 NPs when applied as electrocatalyst in an alkaline medium for water splitting and supercapacitor measurements. The enhanced electrocatalytic performance attributed to the mesoporous structure along with high pore volume, which provides more active boundary sites for the electrochemical process, resulted in the enhanced exchange of the intermediates and more efficient electron transfer. This synthetic methodology, with the advantages of inexpensive/non-complicated experimental setup and high electrochemical performance, could shed light on the development of non-expensive electrocatalysts for clean energy production and storage. Image 1 • Cobalt hydroxide/oxide nanorings are synthesized by a facile approach. • NPs show excellent catalytic activity for oxygen production. • NPs exhibit superior electrochemical cyclic stability. • The superior performance of NPs mainly related to mesoporous structure. [ABSTRACT FROM AUTHOR]

Excellent wave absorbers are key materials for reducing electromagnetic radiation pollution. In this work, novel γ-Fe 2 O 3 nanoring/porous nitrogen-doped graphene (γ-Fe 2 O 3 NR/PNG) composites with varying mass ratios were successfully synthesized as lightweight absorbers using a two-step solvothermal method in combination with a partial reduction process. The diameter of the uniform γ-Fe 2 O 3 NRs is approximately 150 nm with a shell thickness of approximately 50 nm. The uniform γ-Fe 2 O 3 NRs are dispersed onto PNG sheets. Compared with pure γ-Fe 2 O 3 NRs and PNG, all γ-Fe 2 O 3 NR/PNG composites exhibit better microwave absorbing performance, among which a γ-Fe 2 O 3 NR/PNG composite with a 4:1 mass ratio of γ-Fe 2 O 3 NR:PNG shows the best absorption over a broad bandwidth for its special nanoring and porous structure and excellent impedance matching. The minimum reflection loss (RL min) reaches −40.18 dB at 7.80 GHz with a thickness of 2.5 mm; the absorption bandwidth (RL < −10 dB) is 3.41 GHz. Moreover, the composite also reveals a good absorption for microwaves in the low frequency range. At 3.38 GHz, RL min reaches −32.69 dB with a thickness of 5.5 mm. This work provides guidance for designing absorbers that are lightweight, wideband with strong absorption. [ABSTRACT FROM AUTHOR]

Herein, a convenient and cost-effective approach carried out for the synthesis of hexagonal mesoporous β-cobalt hydroxides nanorings via chemical precipitation. Transmission electron microscopic and X-ray diffraction results reveals that these nanorings mostly consist of β-Co(OH) 2 with well crystalline hexagonal brucite like structure. The inert gas sorption-desorption measurements represents the mesoporous nature of the NPs. The Brunauer Emmett Teller surface area and average pore size of the as synthesized nanoparticles were about 210 m2/g and 5 nm. The especial mesoporous structures with excellent specific area are the reason for the good electrochemical capacitance performance and superior cyclic stability (only about 1% decay) in supercapacitor application. The as prepared nanoparticles have been used for oxygen evolution reaction. The oxygen evolution reaction performance is related to the active surface area of the nanoparticles due to the formation of mesoporous structure within the cobalt hydroxide nanoparticles. Furthermore, the presented facile synthetic process, which does not need any surfactant or template, could be extended to the preparation of other nanomaterials with excellent morphologies for supercapacitor and oxygen evolution reaction applications. Image 1 • Mesoporous cobalt hydroxide nanorings are synthesized. • The BET surface area and the average pore size of the NPs were about 210 m2/g and 5 nm. • The NPs exhibits superior cyclic stability (only about 1% decay). • Superior performance of Co(OH) 2 NPs mainly due to mesoporous structure. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Micro patterned a gold nanoring electrode (Au NRE) on top of a silicon micropillar. • Au NRE show remarkable signal-to-noise ratios of 2500. • Semicircle spectrum with kinetically-controlled current response is unique to NRE. • NRE geometry is varied from inlaid to nanotrench by tuning microfabrication steps. • Modified NRE detects dopamine and lead with high sensitivity and selectivity. Abstract We report on the microfabrication and characterization of a gold nanoring electrode (Au NRE) patterned on top of a silicon (Si) micropillar. An NRE of 165 ± 10 nm in width was micropatterned on 4.6 ± 1 μm diameter × 17.5 ± 2.5 μm long Si micropillar with an intervening 50 nm thick hafnium oxide insulating layer. Scanning electron microscopy and energy dispersive spectroscopy data confirmed excellent cylindricality of the micropillar with vertical sidewalls and a completely intact layer of Au NRE encompassing the entire micropillar perimeter. The electrochemical behavior of the Au NRE was characterized by a steady-state cyclic voltammogram with extremely high signal-to-noise ratios of 2500 and charging currents as small as 1.5 ± 0.3 pA. A "semicircle spectrum" from the Nyquist plot indicates a kinetically-controlled voltammetric current response, which is unique to nanoscale electrodes. The variations in the exchange current values, which are dependent on the NRE area and standard rate constant, place a greater emphasis on the isotropic gold wet etching process that defined the geometry of the Au NRE. Circuit fitting of the electrochemical impedance spectra suggests that the NRE geometry can be varied from inlaid to nanotrench with depths controllable by the etching process. This resulted in differing stead-state voltammetric currents and interfacial properties in terms of charge transfer resistance, constant phase element and trench resistance values. The applicability of Au NREs to electrochemical sensing is demonstrated by detecting lead, a neurotoxin at 100 ppb levels. Also, by surface-modification with multi-walled carbon nanotubes, dopamine, a neurochemical implicated in various brain disorders, is detected at a sensitivity as low as 100 nM with 1000-fold selectivity versus common interferents. The flexibility of the microfabrication approach allows for the creation of multiple NREs of controllable width and nanometer spacing on a single micropillar. This capability and in particular where the NRE is micropatterned on three-dimensional microstructures as will be reported herein, facilitates unique electroanalytical capabilities such as intracellular electrochemistry and highly multiplexed detection for emerging biological applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • At finite temperature, a CNT nanoring can be driven to rotate by CNT stators. • As protecting gas, argon can also become a temperature-dependent on–off to the rotary ring. • Periodic formation of the argon cluster leads to periodically fluctuated rotation of the ring. • The nanoring can act as an engine of a nanomachine with controllable speed. Abstract Using argon to protect the rotary nanoring made from curved carbon nanotube, we discover that the gas can act as an on–off and/or a speed controller of the rotary nanoring. The mechanism is that the argon cluster formed at lower temperature provides friction on the nanoring, which may stop rotating due to the friction. Molecular dynamics simulation results demonstrate that the nanoring cannot rotate at 100 K, but rotates at 300 K, or it rotates faster at higher temperature. Periodic fluctuation of the rotational frequency of the ring happens when the argon cluster is formed periodically. Using the nanoring as an engine of a nanomachine, the speed of the machine can be adjusted by changing the ambient temperature. Hence, the argon on–off provides potential application in nanodevices. [ABSTRACT FROM AUTHOR]

This paper proposes a plasmonic nanostructure comprising a silver nanoring and a built-in nanocross (NRC). The plasmon resonance coupling of the NRC was investigated by numerical simulation. The NRC produced multiple resonances and strong electric field enhancement. The resonance position was tuned by changing the parameters of the nanostructure. The corresponding electric field enhancement was observed in different areas of the NRC nanostructure. The adjustable plasmon resonance and the enhanced electric field exhibit potential for subwavelength lithography, surface-enhanced spectroscopy, and biochemical sensing. [ABSTRACT FROM AUTHOR]

Mesoporous nanoring-like Zn-Co mixed oxides are synthesized via a simple template-free solvothermal method with a subsequent annealing process. The ring-like nanostructures with hollow interiors are formed under the complexing effects of potassium sodium tartrate. Numerous mesopores are generated after the precursor is annealed at 500 °C. When applied as anode materials, the mesoporous nanoring-like Zn-Co mixed oxides can deliver a high discharge capacity of 1102 mAh g −1 after 200 cycles at 500 mA g −1 . Even when the current density is increased to 2 A g −1 , the mixed oxides can still retain a reversible capacity of 761 mAh g −1 . Such high cycling stability and rate capability are mainly derived from the unique mesoporous ring-like nanostructures and the synergistic effects between Zn and Co based oxides. [ABSTRACT FROM AUTHOR]

The structural stability and electronic properties of silicane nanoribbon (SiNR) and silicane nanoring (SiNRG) are studied using density functional theory method. The formation energy of SiNR and SiNRG confirms the stable structure. The formation energy for SiNR and SiNRG is found to in the range of −3.33 to −3.80 eV. The adsorption properties of NH 3 molecules on SiNR and SiNRG are explored in terms of adsorption energy, natural bond orbital analysis, energy gap and average energy gap variation. The adsorption energy is observed to be in the range of −0.60 to −0.71 eV, which clearly confirms the adsorption of NH 3 molecules on silicane nanostructures. The change in the electron density along SiNR and SiNRG is observed upon adsorption of NH 3 molecules. The density of states spectrum shows variation in the peak maxima upon adsorption of NH 3 molecules on SiNR and SiNRG base material. The transfer of electrons takes place upon adsorption of NH 3 molecules on SiNR and SiNRG. Moreover, the substitution of phosphorus on SiNR and SiNRG shows enhanced adsorption of NH 3 molecules. The findings suggest that SiNR and SiNRG can be used for the development of NH 3 chemical sensor based on chemi-resistor. [ABSTRACT FROM AUTHOR]

A novel two-step nano-patterning method is proposed to fabricate epitaxial ferroelectric BiFeO 3 (BFO) nanoring array, which maintains well-epitaxial structure and possesses strong ferroelectricity demonstrated by X-ray diffraction (XRD) and piezoresponse force microscopy (PFM). The ferroelectric polarizations were examined by PFM, revealing the reversible switching behavior under an electric field. This novel method could also be extended to other oxide material systems. The fabrication of high quality ferroelectric nanoring structure provides the possibility to explore novel functionalities (e.g., ferroelectric vortices) and offers application potentials for the high-density non-volatile memory devices. [ABSTRACT FROM AUTHOR]

We report here on the results of a systematic investigation of the interfacial reactions and microstructural evolution of nanoscale Ni metal dots on N 2 + -implanted amorphous Si (a-Si) substrates under different annealing conditions. During annealing, Ni 2 Si was the first phase to form, followed by NiSi and NiSi 2 . The three Ni-silicide phases formed were polycrystalline and the average sizes of the annealed nanodots were observed to increase with the annealing temperature, up to 500 °C. After a further increase of the annealing temperature and/or time, it is interesting to note that the NiSi 2 grains gradually migrated outward from their original nanodot positions to the a-Si regions, which resulted in the formation of a remarkable NiSi 2 nanoring structure. The inner regions of the NiSi 2 nanorings were found to be comprised of a single crystalline Si phase, indicating mediation of the epitaxial crystallization of N 2 + -implanted a-Si by the lateral migration of the NiSi 2 nanodots. Furthermore, the annealing temperature required for complete recrystallization of the a-Si layer in the Ni nanodot/N 2 + -implanted a-Si sample could be significantly reduced to 550 °C, 200 °C lower than that which was required the blank N 2 + -implanted a-Si sample. It is suggested that the formation of these remarkable NiSi 2 nanoring structures and the enhancement of N 2 + -implanted a-Si recrystallization in the presence of NiSi 2 nanodots were due to the silicide-induced crystallization mechanism. [ABSTRACT FROM AUTHOR]

We study electron energies in a double concentric quantum ring with anisotropy in the rims heights in the presence of the external magnetic field applied along the symmetry axis. To this end, we consider a model in which the thickness grows linearly from the axis up to the inner rim with a slope different from one between the inner and the outer rims. The anisotropy in the rims heights originated by the presence in the structure of various valleys we simulate by periodic dependence of the slope on the radial direction. We show that the wave functions of the electron confined in such structure can be found analytically if the slopes in all radial directions are the same, and by using a simple exact diagonalization procedure otherwise. The behavior of the electron energies as functions of the magnetic field, rings radii and rims heights, as well as the number of the valleys and their depths is consistently described with our formalism. The entanglement of the states with different radial and orbital quantum numbers, the period and the amplitude of the Aharonov–Bohm oscillations are very sensible to any variations of the rims heights. [ABSTRACT FROM AUTHOR]

In this paper, we study the coherent phonon transport through a cyclic mass-spring structure which is embedded between two longitudinal phononic leads within the harmonic approximation. We assume only the in-plane vibrations for the atoms of the structure and also the nearest neighbor interaction between them. By starting from the system potential energy and then using the Green's function method, we construct a formalism to compute the phononic transmission coefficient and density of states/modes of the system. The numerical calculations are performed for a hexagonal mass-spring ring in the presence and absence of a massive impurity. The results reveal that, the variation of value of the masses or spring constants in the ring leads to appearance of the Fano resonance in the transmission spectrum. This phenomenon occurs at a special phonon frequency independent of the impurity position in the structure. [ABSTRACT FROM AUTHOR]

In this paper, we consider the influence of impurity on the graphene flakes and nanorings conductance. Based on the jumping Hamiltonian for graphene electrons with its direct diagonalization, we obtain the density of states. Further, the tunneling current is calculated for the following contacts: graphene flake-metal, graphene flake-quantum dots, graphene nanoring-quantum dots. We analyze the effect of the flake dimensions and the positions of the adsorbed molecule of impurity on the characteristic properties of the tunneling current. [ABSTRACT FROM AUTHOR]

We analyse the alteration of the density of states of the light- and the heavy-hole magnetoexcitons due to the presence of an impurity donor in InAs quantum ring. It is shown that the donor provides a noticeable redshift of the lower peaks of the density of states, corresponding to the vibrational states of the exciton bound to the donor, while the effect on the higher energy levels related to a relative electron-hole rotation is mainly reduced to the splitting of the twofold degenerate states. Energies dependencies on the external magnetic field, applied along the growth direction show that the exciton-donor interaction leads to the flattening of the curves of the Aharonov-Bohm oscillations of the lowest energy levels and to diminishing of their amplitudes. This effect is more pronounced for heavy-hole magneto-exciton. [ABSTRACT FROM AUTHOR]

The deformation and vibration of vertical flexible loops are investigated theoretically and experimentally. Both upright and hanging loops are considered. Potential applications include nanorings and carbon nanotubes as force sensors or structural components. The upright tubes rest on a rigid or linearly elastic (Winkler) foundation, and cases with adhesion and nonlocal elasticity are included in the analysis. The hanging loops are suspended by a clamp with zero or finite length. The effects of self-weight, foundation stiffness, work of adhesion, and nonlocal elasticity on the loop height or depth are determined, as well as the effects of self-weight and foundation stiffness on the lowest frequency for in-plane symmetric vibration. Good agreement is attained between theoretical results (based on an inextensible-elastica model) and experimental data. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, Au nanorings in a SiO2 substrate have been utilized to design a plasmonic waveguide with lower losses and perfect energy coupling. Our recommended structure consists of a chain of dozen Au nanorings with a given intercenter space between them going on resonance, if a beam with specific wavelength is launched in the input area of the waveguide. Nanoring has an extra degree of freedom in its geometry and have a preferable tunability in comparison to other shapes of nanoparticles (e.g. nanospheres). It is shown that a modified plasmon waveguide structure can be utilized at optical communication band (λ =1550nm), in optical integrated devices. Red-shifted of localized surface plasmon resonance (LSPR) has been considered as a fundamental condition to have a maximum of optical response at λ =1550nm. Cross-sectional depictions of field propagation through the structure are displayed in order to show the absorption and scattering of light by particles. Ultimately, transmitted power ratio is computed for the structure to clear-cutting its characteristics. [Copyright &y& Elsevier]

Abstract: We consider a model of a quantum ring in the form of a thin layer, whose thickness increases linearly between inner and outer radii. We show that in the structural adiabatic limit, when the quantum ring thickness is much smaller than its lateral dimension, the wave equation for the electron confined in such structure can be completely separated. We use analytical solutions found for this model as the base functions for analyzing the effect of the structural non-homogeneity on the electronic spectrum and the Aharonov–Bohm oscillations of the energy levels, in the framework of the exact diagonalization method we found that the pattern of the electron's possible pathways in its displacements generated by the external magnetic field, forms a quasi-one-dimensional region along a guideline marked by a set of highest points of the crater. Therefore, the Aharonov–Bohm oscillations of the energy levels in a crater-shaped quantum dot without non-uniformities are similar to those in 1D quantum ring independently on the crater width. We show that a slight non-uniformity produced by a single valley and single mountain supresses the oscillations of several lower levels due to the localization of the corresponding rotational states close to the mountain. Nevertheless, when the non-uniformity becomes substantial due to the presence of multiple valleys and mountains, the rotational electron motion and the Aharonov–Bohm oscillations generated by the external magnetic field are restored, owing to the electron tunneling through mountains. We consider that our model of crater-shaped structure would be applicable in the analysis of a variety of more complicated problems related to systems of few carriers confined in nanostructures with ring-like geometry, as a starting point in the framework of the diagonalization method. [Copyright &y& Elsevier]

Abstract: With the purpose of guiding and splitting of optical power at C-band spectrum, we studied Y-shape splitters based on various shapes of nanoparticles as a plasmon waveguide. We applied different configurations of Gold (Au) and Silver (Ag) nanoparticles including spheres, rods and rings, to optimize the efficiency and losses of two and four-branch splitters. The best performance in light transportation specifically at telecom wavelength (λ≈1550nm) is achieved by nanorings, due to an extra degree of freedom in their geometrical components. In addition, comparisons of several values for offset distance (d offset) of examined structures shows that Au nanoring splitters with feasible lower d offset have high quality in guiding and splitting of light through the structure. Finally, we studied four-branch Y-splitters based on Au and Ag nanorings with least possible offset distances to optimize the splitter performance. The power transmission as a key element is calculated for examined structures. [Copyright &y& Elsevier]

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]

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]

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]

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: 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]

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]

Plasmonic colour from metals has been recently attracting attention because it is less likely to deteriorate due to environmental change. However, metals such as silver easily react chemically with the atmosphere. Although plasmonic colour in various materials and structures has been assessed, the effects of chemical changes on plasmonic properties have not been deeply investigated. In this paper, we have evaluated the changes in optical properties and structure of silver plasmonic colour from the viewpoint of a phase diagram. As a result, we report remarkable colour changes and the formation of nanorings with a diameter of approximately 100 nm by vacuum ultraviolet light irradiation and heat annealing. [Display omitted] [ABSTRACT FROM AUTHOR]

Magnetic skyrmionium is a donut-shaped spin texture with zero topological number (Q) and has promising application in future spintronic devices. In this work, using micromagnetic simulation based on Landau-Lifshitz-Gilbert (LLG) equation, we report the generation of skyrmionium in an ultrathin magnetic nanoring in the presence of Dzyaloshinskii-Moriya interaction (DMI) and external magnetic field. By varying the DMI strength and outer diameter of a nanoring, the possibilities of creation of other skyrmion states (kπ states) are explored and we have reported the existence of 3π state and 4π state in nanoring for the first time. Also, we report that the transition of skyrmion state from kπ to (k-1)π occurs for a few millitesla (mT) magnetic fields in the out-of-plane configuration. Further, we have demonstrated the degeneration of skyrmionium (Q = 0) into an isolated skyrmion (Q = ± 1) and a pair of skyrmions (Q = − 2) in a nanoring of small dimension by applying an in-plane spin-polarized current. A complete study of the generation of skyrmionium and its topological stability is done by performing the micromagnetic simulation. Our results will provide guidelines for the design of spin-polarized current-controlled skyrmionium-skyrmion based spintronic memory and logic devices. [Display omitted] • Generation of skyrmionium in an ultrathin magnetic nanoring. • Reported 3π state and 4π state by varying DMI strength and diameter of nanoring. • Transition of skyrmion state from kπ to (k-1)π under the influence of magnetic field. • Degeneration of skyrmionium (Q = 0) into skyrmion (Q = ±1) and pair of skyrmions(Q = −2). [ABSTRACT FROM AUTHOR]

• Sb deposition sequentially forms flat (√7 × √7), buckled antimonene and nanoring phases. • The nanoring phase shows bias-voltage dependent STM topography and high stability. • Antimonene and nanoring phases show bandgap signatures contrary to the (√7 × √7) phase. Monolayer and few layer antimony allotropes fabricated on oxide layers are essential for practical applications in fields of solar cells, electronic and photonic devices. Here the antimony structural phases are systemically studied on corrugated copper oxide of Cu(111) by atomically-resolved scanning tunneling microscopy (STM). We find that initial deposition of Sb atoms causes the structural changes of the underlying oxide layer and sequentially gives rise to the formation of flat (√7 × √7)-Sb and buckled antimonene phases. Finally, a nanoring-like antimony configuration is observed with triangle-shaped atomic arrays closely packing and shows high stabilities for oxygen exposure. The (√7 × √7) phase exhibits the metallic property with energetically continuous electronic states existing near Fermi level. For the antimonene and nanoring phases, band gap signatures are observed, implying the semiconducting features. Our results provide a method for fabricating stable elemental allotropes on oxide surfaces. [ABSTRACT FROM AUTHOR]

Abstract: Magnetoresistance for a tri-layered nanoring with wires attached to the ring edges has been investigated. The magnetic domain in the tri-layered ring is well defined due to the GMR effect caused by tri-layered structure. Magnetization reversal is controllable in case that a magnetic field is applied along the wire axis, indicating the present system is promising for an electron interferometer. [Copyright &y& Elsevier]

Abstract: Magnetostatic mode calculations are presented for the bulk and surface modes in long cylindrical magnetic nanorings with arbitrary values of the inner and outer radii. Numerical examples for the dispersion relations are presented for the cases of the ferromagnet Ni and the uniaxial antiferromagnet GdAlO3. The generalization to include retardation effects and hence magnetic polaritons in a ring is briefly indicated. [Copyright &y& Elsevier]

We demonstrate a spaser based on a dark quadrupole surface-plasmon (SP) mode of a trapezoidal nanoring theoretically. The dark quadrupole SP mode can be excited at normal incidence, which is caused by the opposite phase of two different dipoles distributed on the left and right sides of the nanoring. This physical mechanism of the quadrupole SP mode excitation was confirmed by varying the quadrupole SPs as a function of the structural parameters d s and h 0 , and the trapezoidal nanoring with the same circumference. For the demonstration, we study the properties of the spaser based on the dark quadrupole and bright dipolar SP modes of the trapezoidal ring nanostructure. The dark quadrupole SP mode-based spaser exhibits a lower lasing threshold than the dipole SP mode-based spaser. The lasing wavelength can be tuned over a wide wavelength range. The results should be significant to the development of dark SP mode-based spasers. [ABSTRACT FROM AUTHOR]

We report the electronic properties of black phosphorene nanoring (BPN) and adsorption behavior of chronic kidney disease biomarker vapors on BPN. The designed BPN is stable, which is ensured by the formation energy with a value of −3.857eV/atom. The band gap of BPN is recorded as 0.716eV showing the semiconductor property. The prominent kidney disease biomarker vapors, namely isoprene, pentanal, hexanal, heptanal are allowed to interact on BPN and studied based on adsorption property on BPN. Based on charge transfer, energy band gap variation and adsorption energy, we studied the adsorption behavior of BPN towards kidney disease biomarkers. Our findings show that BPN can be used to detect the presence of kidney biomarkers. Image 1 • We studied the stability of black phosphorene nanoring (BPN) based on formation energy. • BPN is used as base material to adsorb kidney disease biomarkers namely isoprene, pentanal, hexanal, heptanal vapors. • The findings shows that BPN is a suitable substrate to detect the severity of kidney disease based on exhaled volatiles. [ABSTRACT FROM AUTHOR]