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In the present study, a modified solvothermal reaction of (hematite) with titanium(IV) butoxide and gold(III) chloride produced ternary Au@TiO2/α-Fe2O3 nanocomposite. The designed Au@TiO2/α-Fe2O3 photocatalyst exhibits nanoring-like structure with high crystallinity indicating the possibility of manufacturing extreme structures and offering a new nanostructure that was not previously studied. Both TiO2 and Au nanoparticles (NPs) were found to be dispersed uniformly on the α-Fe2O3 surface. X-ray diffraction powder technique combined with X-ray photoelectron (XPS) and Raman spectroscopy confirm the formation of the three materials with cubic Au, anatase TiO2 and hematite α-Fe2O3 structures, respectively. The photocatalytic activity proves the performance of this ternary heterojunction to decomposes different pollutants. It was found that, TiO2 absorbs UV-light, α-Fe2O3 absorbs both UV and Visible light and plasmonic gold NPs work as an electron mediator and therefore exhalt the photocatalytic efficiency of the ternary Au@TiO2/α-Fe2O3 photocatalyst. The present work delivers a novel perception to develop a stable photocatalyst based metal oxide/noble-metal hetero-nanostructure for the degradation of different types of pollutants in the industrial zones.

Thermoelastic damping (TED) is one of the significant factor to design the high-efficiency sensors or resonators. Up to now, the single-phase-lagging (SPL) has been analyzed for the various TED mod...

As an ideal high-density storage unit, magnetic nanorings have become a research hotspot in recent years. We can both study the evolution of microscopic state of magnetization and acquire macroscopic magnetic properties by micromagnetic simulation, which has thus been widely used. However, traditional micromagnetism cannot simulate complex stress state. Due to the introduction of microelasticity theory, the phase field method for magnetic materials can be used to calculate the coupling effect of stress and magnetic field. However, the computing model usually needs to satisfy periodic boundary condition. In this paper, the phase field simulation combined with the finite element method is employed. By using user defined element, the evolution of magnetic domain structures of the double-hole nanorings has been studied. In different diameter of the holes and external magnetic field direction, we have found seven kinds of magnetic domain evolution mechanism. Among them, the twin-vortex evolution mechanism with high stability and low demagnetization interference characteristics of advantages, has good application prospect in magnetic random-access memory (MRAM) unit.

Gold nanoring arrays are widely applied in various fields benefitting from their localized surface plasmon resonance (LSPR) properties. A key advantage of gold nanoring arrays is that the dipole resonance peak can be systematically tuned by changing the dimensions of gold nanoring arrays. However, most of the currently reported methods for preparing gold nanoring arrays cannot conveniently control the heights of the nanorings at a low cost. Here we introduce a facile method for preparing gold nanoring arrays with tunable plasmonic resonances using colloidal lithography. The dimensions of the nanorings including diameters, lattice constants, even the heights of the nanorings can be conveniently varied. Fourier transform near-infrared (FT-NIR) absorption spectroscopy was used to obtain the plasmonic resonance spectra of the nanoring arrays. All the prepared gold nanoring arrays exhibited a strong NIR or infrared (IR) plasmonic resonance which can be tuned by varying the nanoring dimensions. This versatile method can also be used to fabricate other types of plasmonic nanostructures, such as gold nanocone arrays. The obtained gold nanoring arrays as well as nanocone arrays may have potential applications in surface-enhanced spectroscopy or plasmonic sensing.

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 Co3O4 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.

Given the special place of hybrid logic circuits such as all-optical full adders in next-generation digital systems, a new kind of these structures using two-dimensional (2D) photonic crystals (2D-PC) is designed and simulated herein. The proposed structure is made of a hexagonal nanoring resonator (NRR), a coupling rod, and several waveguides. In this all-optical full adder, the mechanism of the interference effect in the PCs is used to simplify and minimize the structure. To make the structure flexible, the radius of the dielectric rod in the whole structure and the NRR are considered based on a lattice constant of 0.2a and 0.04a, respectively. The structure is operated at a wavelength of 1550 nm, considering the value of the power entering the waveguides and that exiting the Carry and Sum ports. To analyze the all-optical full adder, the plane-wave expansion method and finite-difference time-domain method are applied respectively to calculate the bandgap diagram and obtain the transmission and propagation of the optical field. In the proposed structure, the contrast ratio at the Carry and is been investigated in a unique and novel way, yielding values of 10.68 and 9.03 dB, respectively. In addition, the maximum and minimum response time for the Carry and Sum are obtained as 1.6 and 0.75 ps, respectively. The total footprint of the structure is about 183 µm2. Due to its ultracompact size, low power consumption, fast response time, and simple structure, this all-optical full adder is suitable for use in low-power optical integrated circuits.

Illumination of colloid sphere monolayers by circularly polarized beams enables the fabrication of concave patterns consisting of circular nanohole miniarrays that can be transferred into convex metal nanoparticle patterns via a lift-off procedure. Unique spectral and near-field properties are achievable by tuning the geometry of the central nanoring and quadrumer of slightly rotated satellite nanocrescents and by selecting those azimuthal orientations that promote localized plasmon resonances. The spectral and near-field effects of hexagonal patterns made of uniform gold nanorings and nanocrescents, that can be prepared by transferring masks fabricated by a perpendicularly and obliquely incident single homogeneous circularly polarized beam, were studied to uncover the supported localized plasmonic modes. Artificial rectangular patterns made of a singlet nanoring and singlet nanocrescent as well as quadrumer of four nanocrescents were investigated to analyze the role of nano-object interactions and lattice type. It was proven that all nanophotonical phenomena are governed by the azimuthal orientation independent localized resonance on the nanorings and by the C2, C1 and U resonances on the nanocrescents in case of $\bar{E}$-field oscillation direction perpendicular and parallel to their symmetry axes. The interaction between localized surface plasmon resonances on individual nano-objects is weak, whereas scattered photonic modes have a perturbative role at the Rayleigh anomaly only on the larger periodic rectangular pattern of miniarrays. Considerable fluorescence enhancement of dipolar emitters is achievable at spectral locations promoting the C and U resonances on the composing nano-objects., arXiv admin note: substantial text overlap with arXiv:2005.07616

Breaking the morphological and compositional symmetries of metallic nanoparticle (NP) dimers provides a novel approach to modulate plasmon coupling between the NPs. In this study, we theoretically investigate the effect of symmetry breaking on the plasmonic coupling in morphologically asymmetric Au nanoring-nanodisk (NR-ND) dimer, compositionally heterogeneous Au-Ag nanoring dimer, and compositionally as well as morphologically asymmetric Au-Ag NR-ND heterodimers. It has been found that when the inner radii of symmetrical Au NR dimer is decreased, the scattering spectral intensity of coupled bonding mode and higher-order coupled bonding mode drastically decreases and increases, respectively. Besides, the effect of aspect ratio on the plasmon resonance modes is investigated. Furthermore, with fixed geometric parameters of one NR and by morphing the shape of the other NR into ND through inner radius, we show the generation and modification of a Fano resonance. As a result of introducing morphological and compositional asymmetry separately, single Fano-type spectral feature is observed in the scattering spectra. We demonstrate that the double Fano resonances can be easily achieved in compositionally and morphologically asymmetric heterodimer with double symmetry breaking. These dual modes are caused by the interference of dipolar bright mode (localized LSPR modes) of Ag NP with the quadrupole and hexapole modes (interband transitions) of the Au NP. Finally, at optimum asymmetric heterodimers, we discussed the effect of refractive index on the Fano-type resonance. These new and simple designs provide a novel insight to modulate optical response and the generation of higher-order Fano resonances, which have many potential applications such as in photonics and refractive index sensing.

The volatile organic compound, nitrobenzene (NB) is made to interact with the primary material, Red-Tricycle-Arsenene (red-T-As) nanoring at four global minima sites (bridge, hollow, valley and ring-sites) by employing density functional theory method. The structural sturdiness of the primary material is evidenced with the cohesive conformation energy of – 3.462 eV/atom. Furthermore, the electronic fingerprints of the pristine and NB surface-assimilated red-T-As nanoring like the energy-gap based Band-Structure and Projected Density of States (PDOS) spectrum along with electron difference density are reckoned. In addition, the adsorption features of NB on red-T-As nanoring, namely, the Bader charge transfer, binding energy, and average energy gap variation are determined. The ciphered attributes articulate the utility of red-tricycle-arsenene nanoring as an efficient chemi-resistor to detect nitrobenzene.

The supramolecular complexes of metallofullerenes and carbon nanoring were constructed and their properties were studied. The size-selective encapsulation of metallofullerene Sc3N@C78, Sc3N@C80 and Sc2C2@C82 by a carbon nanoring of [12]Cycloparaphenylene ([12]CPP) was found. Fluorescence spectral titration experiments showed the different quenching effect of matallofullerenes on photoluminance of [12]CPP. It was found that Sc2C2@C82 has a stronger affinity to [12]CPP, and their supramolecular complex has a stronger host-guest interaction. Electrochemical results revealed that the redox potentials of encapsulated matallofullerenes are shifted compared to pristine species. Moreover, these supramolecular complexes can be dissociated using a metal-organic framework (MOF-177), which can only absorb the metallofullerene, leaving behind hollow [12]CPP. These results reveal the special supramolecular chemistry for metallofullerenes, [12]CPP nanoring, and porous MOF-177. In addition, the powerful attraction of porous MOF-177 for metallofullerene can break the host-guest interaction between metallofullerene and nanoring, which is applicable in separation.

The electronic structure and structural and optoelectronic properties of hexathiopentacene (HTP) nanorings have been carried out by density functional theory (DFT) and time-dependent DFT (TD-DFT). Herein, the binding energy per atom, ionization potential, electron affinity, chemical hardness, highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap, refractive index, charge distributions, absorbance spectra and non-linear optical properties have been measured. The calculations on these nanorings show that the HOMO–LUMO gaps range from 1.87 eV to 1.28 eV, which corresponds to the bandgap of known photovoltaic semiconductors, while the absorbance spectrum increases from 674 nm (1.84 eV) to 874 nm (1.42 eV), which indicates that the HTP nanorings absorb more light as the nanoring size is increased. From the binding energy, the stability of the HTP nanorings is higher than that of the HTP structure. Our results show that an increase in the size may play a significant role in improving the design of optoelectronic devices based upon these HTP nanorings. © 2020, The Minerals, Metals & Materials Society.

Strong light–matter interaction at room temperature is significant for quantum optics, especially for exploring advanced nano-optical devices. We report herein a light–matter interaction in the strong coupling regime between plasmons confined within a single isolated bimetallic nanoring or nanocuboid and molecular excitons of J-aggregates under ambient conditions. We show that a bimetallic Au@Ag nanoring possesses larger enhanced electric field distribution than a Au@Ag nanocuboid, which enables bimetallic nanorings to couple with more excitons efficiently and overcome the large dissipation of the hybrid system. A large vacuum Rabi splitting of 200 meV was observed in this Au@Ag nanoring/J-aggregate hybrid. Finite-difference time-domain (FDTD) simulation and theoretical calculation show that there are ∼196 excitons in each Au@Ag nanoring/J-aggregate hybrid contributing to the coupling with a coupling constant of ∼111.3 meV, which is much higher than that of a single Au@Ag nanocuboid. Our work demonstrates that strong coupling can be realized via the enlargement of the overlap volume between excitons and plasmons, which can maximize the number of excitons contributing to coupling, giving rise to giant vacuum Rabi splitting. Our result provides additional flexibility to the experimental realization of novel plexcitonic architectures to attain strong coupling in an easily integrated and ultracompact platform.

Excellent wave absorbers are key materials for reducing electromagnetic radiation pollution. In this work, novel γ-Fe2O3 nanoring/porous nitrogen-doped graphene (γ-Fe2O3 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-Fe2O3 NRs is approximately 150 nm with a shell thickness of approximately 50 nm. The uniform γ-Fe2O3 NRs are dispersed onto PNG sheets. Compared with pure γ-Fe2O3 NRs and PNG, all γ-Fe2O3 NR/PNG composites exhibit better microwave absorbing performance, among which a γ-Fe2O3 NR/PNG composite with a 4:1 mass ratio of γ-Fe2O3 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 (RLmin) reaches −40.18 dB at 7.80 GHz with a thickness of 2.5 mm; the absorption bandwidth (RL

Using the linear combination of atomic orbitals real-time-propagation rt-TDDFT technique (LCAO-rt-TDDFT) and transition contribution maps, we study the optical and plasmonic features of a metal nanoring (made up of sodium atoms) with respect to the modulation in the ring thickness from a sharp edge (one-atom-thick) to a flat edge (four-atoms-thick). The birth of the localized surface plasmon resonance was accessed by many factors including the number of contributing electron-hole transitions, the relative strengths of these contributions, and the nature of the induced charge density oscillation. We reveal that the occurrence of a large number of contributing electron-hole transitions to an absorption peak cannot be treated as an indicator of plasmonicity. Nonetheless, plasmonicity can be accessed from the transition contribution map (occurrence of many spots with strong contributions and distributed on a large domain of energy) and from the profile of the induced charge density. Our results are useful for designing ultra-small plasmonic devices based on metal nanorings as building blocks.

Photothermal/magnetothermal-based hyperthermia cancer therapy techniques have been widely investigated, and associated nanotechnology-assisted treatments have shown promising clinical potentials. However, each method has some limitations, which have impeded extensive applications. For example, the penetration ability of the photothermal is not satisfactory, while the heating efficiency of the magnetothermal is very poor. In this study, a novel magnetite vortex nanoring nanoparticle-coated with polypyrrole (denoted as nanoring Fe3O4@PPy-PEG) was first synthesized and well-characterized. By combining photothermal and magnetothermal effects, the performance of the dual-enhanced hyperthermia was significantly improved, and was thoroughly examined in this study. Benefiting from the magnetite vortex nanoring and polypyrrole, Fe3O4@PPy-PEG showed excellent hyperthermia effects (SAR = 1,648 Wg–1) when simultaneously exposed to the alternating magnetic field (300 kHz, 45 A) and near-infrared (808 nm, 1 W cm–2) laser. What is more, nanoring Fe3O4@PPy-PEG showed a much faster heating rate, which can further augment the antitumor effect by incurring vascular disorder. Besides, Fe3O4@PPy-PEG exhibited a high transverse relaxation rate [60.61 mM–1 S–1 (Fe)] at a very low B0 field (0.35 T) and good photoacoustic effect. We believe that the results obtained herein can significantly promote the development of multifunctional nanoparticle-mediated magnetic and photo induced efficient hyperthermia therapy.

International audience; Microdevices composed of microwell arrays integrating nanoelectrodes (OptoElecWell) are developed to achieve dual high‐resolution optical and electrochemical detections on single Saccharomyces cerevisiae yeast cells. Each array consists of 1.6 × 105 microwells measuring 8 µm in diameter and 5 µm height, with a platinum nanoring electrode for in situ electrochemistry, all integrated on a transparent thin wafer for further high‐resolution live‐cell imaging. After optimizing the filling rate, 32% of cells are effectively trapped within microwells. This allows to analyse S. cerevisiae metabolism associated with basal respiration while simultaneously measuring optically other cellular parameters. In this study, the impact of glucose concentration on respiration and intracellular rheology is focused. It is found that while the oxygen uptake rate decreases with increasing glucose concentration, diffusion of tracer nanoparticles increases. The OptoElecWell‐based respiration methodology provides similar results compared to the commercial gold‐standard Seahorse XF analyzer, while using 20 times fewer biological samples, paving the way to achieve single cell metabolomics. In addition, it facilitates an optical route to monitor the contents within single cells. The proposed device, in combination with the dual detection analysis, opens up new avenues for measuring cellular metabolism, and relating it to cellular physiological indicators at single cell level.

High-Q factor can enhance the interaction between light and matter, which is an important parameter to decrease the threshold of nanolasers. Here, we theoretically propose an eccentric nanoring structure with a high and controllable Q factor to realize a low-threshold and controllable nanolaser by amplifying the quasi-bound states in the continuum (quasi-BIC). The designed nanostructure supports a quasi-BIC because of the symmetry protection-breaking of the nanostructure. The quasi-BIC has a very high Q factor of about 9.6×104 and can also be adjusted by changing structural parameters. We use the energy level diagram of the four-level two-electron system to study the lasing action of the eccentric nanoring structure. The results show that the nanolaser has a relatively low threshold of about 6.46 μJ/cm2. Furthermore, the lasing behavior can be tuned by controlling the structural parameters of the eccentric circular ring structure.

Rationally engineering the microstructure and electronic structure of catalysts to induce high activity for versatile applications remains a challenge. Herein, chlorine doped graphitic carbon nitride (Cl-doped g-C3N4) nanorings have been designed as a superior photocatalyst for pollutant degradation and oxygen evolution reaction (OER). Remarkably, Cl-doped g-C3N4 nanorings display enhanced OER performance with a small overpotential of approximately 290 mV at current density of 10 mA cm−2 and Tafel slope of 83 mV dec-1, possessing comparable OER activity to precious metal oxides RuO2 and IrO2/C. The excellent catalytic performance of Cl-doped g-C3N4 nanorings originates from the strong oxidation capability, abundant active sites exposed and efficient charge transfer. More importantly, visible light irradiation gives rise to a prominent improvement of the OER performance, reducing the OER overpotential and Tafel slope by 140 mV and 28 mV dec-1, respectively, demonstrating the striking photo-responsive OER activity of Cl-doped g-C3N4 nanorings. The great photo-induced improvement in OER activity would be related to the efficient charge transfer and the OH radicals arising spontaneously on CN-Cl100 catalyst upon light irradiation. This work establishes Cl-doped g-C3N4 nanorings as a highly competitive metal-free candidate for photoelectrochemical energy conversion and environmental cleaning application.

Cycloparaphenylene (CPP) crystals comprising of molecular carbon nanorings are a unique class of carbon-based nanomaterials possessing inimitable properties. Based on molecular dynamics simulations and density functional theory calculations, the mechanical and thermal properties of CPP crystals are investigated in the present study. Our results show that CPP crystals possess an ultrahigh energy absorption capacity, an ultralow thermal conductivity and an ultralight weight simultaneously, which can be attributed to their intrinsically porous lattice structures and also the nanoscale dimension of their component nanoring cells. Such unique coexistence of high energy absorption and thermal insulation capacities in CPP crystals makes them more appealing in some extreme environment applications when compared to most existing engineering materials. Moreover, the energy absorption capacity and thermal conductivity of CPP crystals are also found to strongly depend on the cell size and packing mode of their component CPP molecules. The high tunability of the energy absorption capacity and thermal conductivity observed in CPP crystals raises the potential to design them for specific application requirements.

A magnetic nanoring model with surface anisotropy by bending a single-walled nanotube was proposed and was placed in an inhomogeneous magnetic field produced by an electric current passing through the center of the nanoring and perpendicular to the ring plane. The ground state with vortex spin structure was determined and the magnetization was calculated by using the spin Green’s function method. It is found that the strong surface anisotropy can ensure the spins vortex state of the system. With the increase of temperature, the total order parameter of the spins gradually decreases to zero from their classical values. As the radius of the nanoring increases, the transition temperature of the system decreases rapidly and then gradually tends to a finite value. Changing the direction of the current, the generated reverse toroidal magnetic field can switch the magnetic state of spins from a vortex state to a reversal vortex state. The value of the current required for magnetization switching shows monotonic relationship to the radius of nanoring, surface anisotropy and the temperature which is far below the transition temperature. When the temperature is greater than the transition temperature, system shows the paramagnetic behavior.

In this paper, we demonstrate a dual-band metamaterial perfect absorber based on a Ag-dielectric-Ag multilayer nanostructure. The structure of top metal film covers nanoring grooves array. A dielectric layer has a function of confining electromagnetic fields. Theoretical analysis shows that two absorption peaks (1059 nm and 1304 nm) with the absorption of 99.2% and 99.9% have been achieved, respectively. The physical origin of perfect absorption peaks are related to the Fabry-Perot resonance effect and localized surface plasmon resonance (LSPR) of the nanoring grooves. Its perfect absorption and resonance wavelength can be well regulated by adjusting the relevant structural parameters. Additionally, the absorber demonstrates good operation angle-polarization-tolerance at wide incident angles (0–60°). We believe that our design has a promising application in plasmon-enhanced photovoltaic, optical absorption switching, and modulator optical communications in the infrared regime.

Improving the photon absorption in ultrathin-film solar cells with active layer thickness of a few micrometers is important for enhancing efficiency and reducing cost. We present a computational study of novel design consisting of ultrathin absorber layer made of gallium arsenide (GaAs) integrated with plasmonic square nanoring particles. The energy absorbed by GaAs layer is significantly enhanced with the help of plasmonic nanorings, resulting in substantial absorption enhancement of approximately 34% compared with bare active layer. For qualitative analysis, the short-circuit current density of thin-film cell is evaluated for AM 1.5 G solar illumination and is found to be 1.4 times higher compared with unpatterned solar cell structure. Furthermore, the structure is optimized by varying different parameters and materials of functional layers, yielding a photocurrent density of 30.185 mA/cm2, which is close to the Yablonovitch limit.

Droplet evaporation is widespread in natural and industrial application, and the rapid and efficient evaporation can significantly improve energy efficiency. However, the fundamental mechanism of contact line dynamics and the microscopic characteristics of evaporating nanodroplets are not well understood. Moreover, how to design a nanostructure surface to enhance nanodroplet evaporation remains unclear. Here, through molecular dynamics simulation, we investigated the evaporation dynamics of nanodroplets on various nanoring surfaces with different geometric parameters and wettability. By measuring the changes of contact radius and contact angle, the results showed that nanodroplets successively exhibit constant contact angle (CCA), constant contact radius (CCR), and mix mode during evaporation, and the evaporation-induced CCA-CCR transition, in essence, is a Cassie-Wenzel wetting transition, whose onset time is remarkably dependent on the surface roughness and wettability. We found that this evaporation-induced wetting transition is postponed on the surface with small nanostructure spacing and weak hydrophilicity, and the evaporation rate of nanodroplets improves accordingly. The dense and hydrophobic nanostructures can not only restrain the Cassie-Wenzel transition, but also enhance the evaporation rate of nanodroplets. Last, through the potential energy field analysis of nanoring substrates, we revealed that the Cassie-Wenzel wetting transition of nanodroplets is a process of molecule migration to low potential energy regions. Our work provides guidance for designing nanostructure surfaces to effectively control the droplet wetting state and enhance its mass transfer performance of phase change.

Precise control over the spatial arrangement of inorganic nanoparticles on a large scale is desirable for the design of functional nanomaterials, sensing, and optical/electronic devices. Although great progress has been recently made in controlling the organization of nanoparticles, there still remains a grand challenge to arrange nanoparticles into highly-ordered arrays over multiple length scales. Here, we report the directed arrangement of inorganic nanoparticles into arrayed structures with long-range order, up to tens of microns, by using hexagonally-packed cylindrical patterns of block copolymer nanosheets self-assembled within collapsed emulsion droplets as scaffolds. This technique can be used to generate nanoparticle arrays with various nanoparticle arrangements, including hexagonal honeycomb structures, periodic nanoring structures, and their combinations. This finding provides an effective route to fabricate diverse nanoparticle arrayed structures for the design of functional materials and devices.

Metallofullerenes have a cage-shaped molecular structure and special properties derived from encapsulated metal atoms. Owing to the ball-like fullerene cage, it is still a challenge to manipulate the metallofullerene molecule and to control its properties. Herein, we use the molecular carbon nanoring of [12]cycloparaphenylene to hoop the C80-based metallofullerene Y3N@C80 and azafullerene Y2@C79N, resulting in a stable supramolecular complex, induced molecule orientation, changed assembly behavior, and tunable spin state. These supramolecular complexes and their host–guest interactions were systematically characterized by DFT-calculations, spectroscopy, NMR, and electrochemical analysis. Scanning tunneling microscopy was employed to reveal that the metallofullerene guests dominate the assembly process on the Au(111) surface and the [12]CPP nanoring can change the weak van der Waals forces and influence self-assembly. Moreover, the electron spin in paramagnetic Y2@C79N was employed to percept the host–gues...

Due to its potential application in magnetic memory, the vortex magnetization configuration has drawn much attention, which had been found in many magnetic nanostructure. In this paper, static and dynamic characteristics of magnetism in permalloy oval nanoring are investigated with varying thickness and arm width via micromagnetic simulation. Two magnetization configuration (vortex and onion states) were found in oval nanoring and the vortex state is a stable state. Although onion is a metastable state, it become more stable with the decrease of thickness. The magnetic hysteresis loop along long axis of oval nanoring is simulated and coercive forces are investigated as function of arm width and thickness. Coercive force increases firstly and then decrease with the increase of thickness. In meanwhile, the dynamic magnetic susceptibility of vortex state in oval nanoring is simulated for varying arm width and thickness. Uniform resonance mode and edge resonance mode can be found when thickness is above 25 nm. However, there is a single uniform resonance mode in oval nanoring with thickness less 20 nm. The resonance frequency can be significantly modulated in the region of 8.2–13.7 GHz when thickness changes from 4 to 100 nm.

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.

The optical performance of two dimensional (2D) metallic nanoring arrays is inevitably affected by their substrate. This problem can be solved by using three dimensional (3D) nanorings, whose height is larger. However, most reported 3D-metallic nanoring arrays were prepared through focused ion beam lithography, which is high cost and low efficiency. Herein, we provided a new approach to fabricate highly ordered 3D-silver nanoring arrays (3D-AgNRAs) over a large area through multistep colloidal lithography combined with metal deposition. The specific structure of the 3D-AgNRAs could be facilely tuned by modulating the etching conditions. After gradual optimization of the 3D-AgNRAs’ structural parameters with respect to their optical and sensing performance, the optimized 3D-AgNRAs’ structural features were finally settled to be 1 μm period, 200 nm nanoring height, 300 nm silver layer thickness, 830 nm outer diameter, and 428 nm inner diameter. The optimized 3D-AgNRAs achieved high refractometric sensitivity of 1105.8 nm per RIU and relative sensitivity of 50.2% per RIU. Ultimately, the optimized 3D-AgNRAs were employed as an immunoassay substrate to prove their label-free biosensing potential in the future.

Inspiration from nature has driven the development and applications of greener inorganic nanomaterials prepared using biotemplates in the field of nanoscience. In this study, we report the superiority of using a biosynthesized silver nanoring material for CO formation in CO2 saturated KHCO3. Compared to bulk silver and free silver nanoparticles prepared by pure chemical reduction, this silver nanoring (assembled on tobacco mosaic virus coat protein) exhibits significantly enhanced activity and selectivity for the conversion of CO2 to CO. The highest CO faradaic efficiency reaches 95.0% at an overpotential of 910 mV. Additionally, the CO partial current density is 2.7-fold higher than that of the free silver nanoparticles. We believe that the improved catalytic performance is related to the structuring ligand effect of the protein. The numerous functional groups on the protein may tune the reaction activity by influencing the binding energies of the intermediate species from CO2 reduction or hydrogen evolution.

Nanostructured transition metal oxide anodes have attracted considerable attention for high-performance lithium-ion batteries (LIBs). However, their low rate capability and rapid capacity decline resulting from their low electronic conductivities and inevitable substantial volumetric changes prevent them from being commercialized as anodes for LIBs. Herein, we design a high-performance anode for LIBs consisting of a yolk–shell structured Fe2O3@C nanoring (NR) composite that comprises a NR-like Fe2O3 core entirely protected by a fine porous carbon (C) shell to overcome such obstacles. This advantageous yolk–shell structural design can buffer the significant volume variations of Fe2O3 cores without damaging the microstructure of the electrode. Thanks to the unique structural features, the as-built electrode shows a remarkable electrochemical performance, namely, a large specific capacity of 846 mA h g−1 after 100 cycles at 0.2 A g−1, a superior rate performance of 688 mA h g−1 at 4 A g−1, and a remarkable cycling life (300 cycles, 945 mA h g−1 at 4.0 A g−1). Hence, this electrode is much better than a pure Fe2O3 NR electrode.

Remote modulation of nanoscale biochemical processes in a living system using magnetic stimulation is appealing but is restricted by the lack of a highly efficient nanomediator which can deliver timely and effective response to biological molecules under an external magnetic field. Herein, we report the development of a novel nanocatalyst based on a ferrimagnetic vortex-domain nanoring (FVIO)-enzyme hybrid that enables real-time modulation of enzymatic catalysis under an alternating magnetic field (AMF). The role of the FVIO is to provide localized heating immediately upon exposure to an AMF, which efficiently and selectively promotes the activity of conjugated enzymes on the surface. The reaction rate of the as-fabricated FVIO-β-Gal hybrid was shown to be boosted up to 180% of its initial value by localized heat generated under an AMF of 550 Oe in less than 2 s and without heating up the bulk solution. Moreover, the degree of activity acceleration was shown to be tunable by increasing the strength of the AMF. The concept of remote magnetic stimulation of enzymatic reactions has been further applied to other enzymes (e.g. FVIO-KPC and FVIO-GOx), demonstrating the general applicability of this strategy. Since almost all metabolic processes in cells rely on enzymatic catalysis to sustain life, the FVIO-enzyme system developed in this work provides a valuable nanoplatform for spatiotemporally manipulating biochemical reactions, which might pave the way for future remote manipulation of living organisms.

In this work, we proposed an all-dielectric nanostructure composed of silicon concentric nanoring resonator dimers (Si CNRD). We studied the scattering properties of Si CNRD and demonstrated the magnetic Fano resonance resulting from the interference between a narrow magnetic dipole mode and a broad magnetic dipole mode coupled into Si CNRD excited by an azimuthally polarized beam (APB). The spectral characteristics of the magnetic Fano resonance are characterized quantitatively by a coupled oscillator model. By changing the geometric parameters of the Si CNRD, the wavelength and intensity of the magnetic Fano resonance can be effectively adjusted. The nanostructure we proposed exhibits potential applications in low-loss sensors, nonlinearity, and laser devices.

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.

Structural color has been particularly attractive as it provides a highly promising approach for next-generation color printing. Plasmonic nanostructures have been intensively investigated for color printing, while suffering from intrinsic loss that degrades the quality of the coloration. Dielectric materials have emerged as an alternative because of their high refractive index that enables highly confined optical modes within the nanostructure at the diffraction limit. Here, we demonstrate an all-dielectric nanoring metasurface for coloration. By harnessing the intrinsic nanoring structure design, vivid structural color has been achieved in the visible range. The color gamut is expected to occupy 115% of the standard color space (sRGB) on the chromaticity diagram of the International Commission on Illumination (CIE) 1931 in theory. Our structure can be applied to various complex devices and materials and find potential applications such as displays, information, and art works.

Nanostructured polymeric materials, functionalized with an appropriate receptor, have opened up newer possibilities for designing a reagent that shows analyte-specific recognition and efficient scavenging of an analyte that has either a detrimental influence on human physiology and environment or on its recovery for further value addition. Higher active surface area, morphological diversity, synthetic tunability for desired surface functionalization, and the ease of regeneration of a nanostructured material for further use have provided such materials with a distinct edge over conventional reagents. The use of a biodegradable polymeric backbone has an added significance owing to the recent concern over the impact of polymers on the environment. Functionalization of biodegradable sodium alginate with AENA (6.85% grafting) as the receptor functionality led to a unique open framework nanoring (NNRG) morphology with a favorable spatial orientation for specific recognition and efficient binding to uranyl ions (U) in an aqueous medium over a varied pH range. Nanoring morphology was confirmed by transmission electron microscopy and atomic force microscopy images. The nanoscale design maximizes the surface area for the molecular scavenger. A combination of all these features along with the reversible binding phenomenon has made NNRG a superior reagent for specific, efficient uptake of UO22+ species from an acidic (pH 3-4) solution and compares better than all existing UO22+-scavengers reported till date. This could be utilized for the recovery of uranyl species from a synthetic acidic effluent of the nuclear power. The results of the U uptake experiments reveal a maximum adsorption capacity of 268 mg of U per g of NNRG in a synthetic nuclear effluent. X-ray photoelectron spectroscopy studies revealed a reductive complexation process and stabilization of U(IV)-species in adsorbed uranium species (U@NNRG).

Photon scattering and the ensuing excitation of surface plasmons in single rings, single composite rings, and many-ring systems was recently shown to provide dispersion and field distributions [K. V. Garapati et al., J. Phys. Commun. 2, 015031 (2018)] of potential for specific applications in particle and molecular trapping [R. Alaee et al., Appl. Phys. Lett. 109, 141102 (2016); M. Salhi et al., Phys. Rev. A 92, 033416 (2015)], in addition to metamaterials and sensing. Following photon or electron interactions with metallic nanorings, both radiative and nonradiative decay channels are important in the consideration of the nanoparticle as a photon or phonon source, and in related applications. Here, we quantize the electronic normal modes of the ring torus and obtain the radiative decay of plasmons. Due to a geometry-related complexity, we employ a perturbation approach to obtain analytical expressions for the radiative decay channel for a vacuum bounded single solid nanoring. In quantizing the fields, the frequency spectrum of the charge density normal modes of the nanoring is obtained and shown to agree with the exact quasistatic plasmon dispersion relations. Higher-order corrections beyond the presented zero- and first-order calculations may be obtained following the presented results. The results are of potential interest in quantum sensing such as entangling photons and plasmons, or plasmons and trapped molecules.

In this paper, a novel structure based on nanodisk and nanoring resonators in a Metal-Insulator-Metal (MIM) plasmonic waveguide for triple-channel wavelength demultiplexer (WDM) is proposed. WDM structure consists of a bus waveguide which has been perpendicularly coupled with several nanodisks and nanorings and three drop waveguides. The proposed structure can be adjusted by appropriate choose of refractive index and geometrical parameters. The simulation results present that the transmission spectrum efficiency in the proposed structure increases up to about 80%. The proposed structure can be used in the ultra-compact demultiplexer devices, nanosensors and optical integrated circuits. In this paper, the used numerical method is two dimensional Finite-Difference Time-Domain (FDTD) approach.

We numerically and theoretically investigate a highly sensitive and tunable plasmonic refractive index sensor that is composed of a metal-insulator-metal waveguide with a side-coupled nanoring, containing silver nanorods using the finite element method. Results reveal that the presence of silver nanorods in the nanoring has a significant impact on sensitivity and tunability performance. It gives a flexible way to tune the system response in the proposed structure. Our designed sensor has a sensitivity of 2080 nm/RIU (RIU is the refractive index unit) along with a figure of merit and a quality factor of 29.92 and 29.67, respectively. The adequate refractive index sensitivity can increase by adding the silver nanorods in a nanoring, which can induce new surface plasmon polaritons (SPPs) modes that cannot be found by a regular nanoring. For a practical application, a valid introduction of silver nanorods in the nanoring can dramatically reduce the dimension of the proposed structure without sacrificing performance.

The key point of improving the thermal conductivity of polymer is to increase the orientation of the chains and reduce the disorder conformation. Recently, the nanoring structures are incorporated into polymers to tune the chain dynamics. In this work, the wide diameter (4~7 nm) but short length (~10 nm) BN nantube as nanoring incorporated into polyethylene. The thermal conductivity of nanocomposite can be increased by about 3 times from the nonequilibrium molecular dynamics calculation. Structurally, the polyethylene chains are aligned along the nanoring. In addition, the confinement of nanoring reduces the mobility of polyethylene chains by 40% and enhances the interatomic and interaction, which results in red shift of low frequency phonons. The results provide valuable guidance for improving the thermal conductivity of polymers by doping nanoring.

Ferromagnetic nanorings exhibit tunable magnetic states with unique magnetization reversal processes and dynamic behavior that can be exploited in data storage and magnonic devices. Traditionally, probing the magnetization dynamics of individual ferromagnetic nanorings and mapping the resonance modes has proved challenging. In this study, micro-focused Brillouin light scattering spectroscopy is used to directly map the spin wave modes and their intensities in nanorings as a function of ring width and applied magnetic field. Micromagnetic simulations provide further insights into the experimental observations and are in good agreement with the experimental results. These results can help in improving the understanding of spin wave confinement in single elements for magnonic devices and waveguides.

A U-shaped tunnel connected side coupled nanoring resonator waveguide system is proposed to generate Fano interference in a novel mechanism. By mutually coupling the infrared light through the artificially introduced U-tunnel to the two nanorings with the same resonant wavelength, single symmetric Lorentzian resonance transforms to asymmetric Fano resonance within the original resonant spectral range. The transparency window bridges the distinct constructive interferences in either rings instead of the canceling the bright mode resonance compared to former conceptions. The sensitivity of the system reaches 167 μ m ∕ R I U far higher than the level of hundreds nanometers and is highly tunable. The light at resonance is successfully trapped and slowed down to 1/144 times the speed in vacuum, which is also flexible to release by tuning the Fermi energy of graphene rings. Overall, our ideas may pave new avenues to the design of classical analogy of Fano resonance metastructures, sensors or light storage devices.

A miniature resonator sensor based on a hybrid plasmonic nanoring with a gold layer coated uniformly on the outer boundary is described and investigated. By using the Lumerical finite-difference-time-domain (FDTD) method, the optimized sizes of the plasmonic layer thickness and the central hole are given and insight into the dependence of spectral displacements, Q factors, sensitivity and detection limits on the ambient refractive index is presented. Simulation results reveal that the miniature resonator sensor featuring high sensitivity of 339.8 nm/RIU can be realized. The highest Q factor can reach ∼60,000 with this nanoring and the minimum detection limit is as low as 1.5 × 10−4 RIU. The effects on the resonance shifts and Q factors due to geometric shapes of the inner boundary of the nanoring are discussed as well. This miniature resonator sensor has good potential for highly sensitive ultracompact sensing applications.

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.

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.

This paper proposes a methane sensor based on localized surface plasmon resonance (LSPR) of a hexagonal periodic gold nanoring array. The effects of structural parameters on the extinction spectrum and refractive index (RI) sensitivity are analyzed to obtain optimal parameters. In particular, the RI sensitivity can reach 550.08 nm/RIU through improvement of the sensor structure, which is an increase of 17.4% over the original value. After coating a methane-sensitive membrane on the inner and outer surfaces of the gold rings, the methane concentration can be accurately measured with a gas sensitivity of &minus, 1.02 nm/%. The proposed method is also applicable to quantitative analyses of components concentration and qualitative analyses of gas composition.

Designing nanomaterials with advanced functions and physical properties to improve cancer diagnosis and treatment has been an enormous challenge. In this work, we report the synthesis of magnetic gold nanowreaths (AuNWs) by combining wet-chemical synthesis with layer-by-layer self-assembly. The presence of Au branches, small junctions, and central holes in AuNWs led to improved photothermal effect compared with Au nanoring seeds and thick Au nanoring with smooth surface. The self-assembly of exceedingly small magnetic iron oxide nanoparticles (ES-MIONs) on the surfaces of AuNWs not only effectively quenched the T1-weighted magnetic resonance imaging (MRI) ability due to the enhanced T2 decaying effect but also provided the responsiveness to glutathione (GSH). After intravenous injection, the T1 signal of magnetic AuNWs initially in the “OFF” state can be intelligently switched on in response to the relatively high GSH concentration in tumor, and the formation of larger assemblies of ES-MIONs improved thei...

This work reports on a study regarding the plasmonic properties of a symmetry-breaking silver nanoring structure, in the wavelength range of 0.6–4.5 µm. A broken silver ring with a certain angle, as well as a full ring composed of silver and other metallic/dielectric materials, are proposed. The extinction efficiencies of the nanostructure are numerically calculated with several parameters being varied, including the broken angle, the inner and outer radii, and the thickness of the broken ring, as well as the material in the composite full ring. Multiple plasmonic resonances are observed in the extinction efficiency curves, which are attributed to the quadrupolar, octupolar, and hexadecapolar resonance modes that are revealed by the electric field distributions. The results demonstrate that the high-order modes can be altered, by varying the value of the broken angle of the ring. It is also illustrated that the resonance wavelength and the full width at half maximum of certain high-order plasmonic resonance peaks can be tuned in the wavelength range studied, by adjusting the values of the geometrical parameters of the nanoring. The plasmonic characteristics of the symmetry-breaking nanoring structure revealed in this study, provide a great platform for the designs of plasmonic devices utilizing the high-order plasmonic resonances. Besides, it is also proposed a scheme to switch the device between the multi-wavelength and single-wavelength modes.

Optical properties of the asymmetric nanoring/ellipsoid dimers with breaking of geometric symmetry are investigated theoretically. A tunable high-order surface plasmonic resonance is achieved. It is demonstrated that such high-order resonances result from the plasmonic coupling between the modes of a nanoellipsoid and of an asymmetric nanoring. Interestingly, a current loop is observed on the nanoellipsoid under coupling of the two nanostructures. The surface plasmonic resonance of this nanostructure can also produce enhanced local fields that can be applied in surface-enhanced spectroscopy and biosensing.

We developed a simple method to adjust the structural transformation of DNA-gold nanoparticles assemblies from linear arrays to nanorings by increasing salt concentrations. A DNA nanoladder constructing from RCA origami acted as templates to assemble periodic AuNPs arrays by a terminal thiol located on staple oligonucleotides. The linear AuNPs arrays could be transformed into nanorings only by changing the concentration of NaCl aqueous solution during the assembly process. It was proven that the electrostatic repulsion, being asymmetrically diminished by the high concentration of NaCl, caused the formation of nanoring architectures.

Not only amphiphiles but also non-amphiphilic or π–conjugated molecules, if rationally designed, have been found to self-assemble in liquid media to form discrete tubular architectures with well-defined dimensions. This review covers most of the molecular building blocks that spontaneously produce organic nanotubes (ONTs) through self-assembly. Starting with the comparison of synthetic procedures and physical properties between the ONTs and carbon nanotubes (CNTs), the author discusses the classification of formation mechanism for the self-assembled ONTs. Then, membrane- or sheet-based, nanoring- or nanotoroid-based, stacking-based, and supramolecular stacking-based pathways of the self-assembly are described in relation to the presence or absence of intermediate structures. Concerning the membrane- or sheet-based mechanism, the molecular design and functionalities of each building block, and the dimensions of obtained ONTs are discussed in terms of the self-assembling features of amino acids, bile acids,...