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As a semiconductor material with a 2D-laminate structure, g-C3N4 (bandwidth 2.7 eV) has a similar structure and excellent performance to graphene. However, high surface energy and photogenerated e–h recombination of g-C3N4 seriously hinder its application in the field of marine anticorrosion and antifouling. To solve these problems, we synthesized the g-C3N4 nanosheets decorated with ZnO nanoring via chemical etching technology. Whether the NR ZnO-CNNs have surface protection performance among the pure EP on the corrosion protection for metal substrate were investigated. The antifouling properties NR ZnO-CNNs hybrid were also estimated through photocatalytic bacterial and algae resistance tests. Combined with the electrochemical results, it was found that the impedance modulus of NR ZnO-CNNs/EP within 45 days showed two orders of magnitude higher than that of pure EP in the 3.5 wt% NaCl solution. Besides, Local electrochemical impedance spectroscopy (LEIS) further explored the anticorrosion behavior of NR ZnO-CNNs/EP coating, which indicated that the NR ZnO-CNNs/EP coating with a scratch maintained an excellent corrosion resistance between 0–24 h. Under the visible light conditions, the lifetime of photogenerated e–h was prolonged due to the formation of NR ZnO-CNNs heterojunction structure, it was observed that the antibacterial rate against Bacillus subtilis reached 100% within 8 h. An Antialgae test was performed on chlorella seawater solution, which indicated that 5 mg/mL of NR ZnO-CNNs hybrid could make chlorella sharply reduce within 4 days. Simultaneously, the corrosion protection and photocatalytic antifouling mechanisms of NR ZnO-CNNs were proposed, thus it provided a broader platform for the design of versatile marine protection materials.

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.

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.

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 design of a facile and scalable method to synthesize solar light driven photocatalyst to generate H2 from water and degradation of toxic dyes from waste water is highly challenging field of research. Here, we are reporting a one pot synthesis of CdS/CdO colloidal nanocomposite with variable amount of CdS thickness and finally CdS nanoring. Different outward diffusion rate of oxygen and inward diffusion rate of sulphur ions generates hollow CdS/CdO nanocomposite based on nanoscale Kirkendall effect. Au nanoparticles (NPs) have been selectively deposited over CdS. Proper band alignment among CdO, CdS and Au results in a Z-type photocatalyst. Efficient spatial charge separation and large surface area lead to high photocatalytic dye degradation and Cr (VI) reduction in water. The amount of Cd in purified water is lesser than 0.003 ppm which maintains world Health Organization (WHO) guideline. The as developed catalyst is also active for generation of H2 from water in presence of solar light irradiation. Our present work may provide a promising way to fabricate an efficient photocatalyst for dye degradation and solar to fuel energy conversion using semiconductor (CdO)-semiconductor (CdS)-metal (Au) nanocomposite.

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

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.

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.

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.

A 18-metal Yb(III) nanoring was constructed by the using of a Schiff base ligand. It exhibits interesting NIR luminescent sensing behavior to antibiotics and explosives, in particular to NFAs and TNP with high sensitivity. The KSV values and LODs of this lanthanide nanoring to NFAs and TNP are 1.5 × 104–4.6 × 104 (mol/L)−1 and 1.7–5.1 μmol/L, respectively. Its high luminescence sensitivities to NFAs and TNP are not affected by the existence of other antibiotics and explosives.

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.

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.

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.

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.

We study the evolution of the magnetic field-induced switching between the stable domain configurations of permalloy nanoring structures, when magnetic nano-wires are attached to them. Magnetoresistance measurements were performed on such devices for two configurations of the attached nano-wires: (i) when they are at diametrically opposite ends of the nanoring, and (ii) when the nanowires are at an obtuse angle with respect to each other. During the measurements, the direction of application of the in-plane magnetic field is varied to understand the switching properties of the devices. Micromagnetic simulations were carried out in order to understand the domain configuration and reversal mechanism. We show that due to the nature of domain walls created by the presence of the nano-wires in the obtuse configuration, a vortex state can be stabilized in the nano-ring. We extended our studies to various nanoring devices with different widths while keeping a constant thickness.

TiO 2 with Nanoring/Nanotube (R/T) hierarchical structure can be prepared by tuning the oxidation time and oxidation voltage in the second step anodization. The resulting multiabsorption oscillating peaks in the visible light region present a strong dependence on the tube length which are derived from the interference of light reflected from the top nanorings and the bottom Ti substrate, and the optical path length in TiO 2 R/T hierarchical structure can be estimated as about 2 μm. The tube length of the as-prepared TiO 2 photoelectrode affects greatly its saturation photocurrent density, and the different tube-wall thickness can change the photocurrent-saturation potential. Under simulated AM 1.5 irradiation (100 mW/cm 2 ), TiO 2 R/T hierarchical structure with tube diameters of 20–40 nm and tube length of about 1.5 μm shows higher photocurrent density and hydrogen production rate at the bias of 0 V (vs. Ag/AgCl). The results from the IPCE plots and I-t curves verify that TiO 2 R/T hierarchical structure can exhibit the visible light activity, which is more related to the absorption induced by the defects rather than oscillating peaks. Based on the unique multiple light reflection in TiO 2 R/T hierarchical structure, surface treatment will pave a way for the better utilization of oscillating peaks in the visible light region.

In this paper, we reported a multilayer metamaterial system with ultrahigh absorption, consisting of silver nanoring, upconversion nanoparticles(UCNPs) and silver film, which can dramatically enhance the upconversion emission. A simplified theoretical expression of the upconversion enhancement factor(EFupc) was derived, and the structure parameter and the local field-UCNPs coupling were considered for the EFupc analysis. It was found that the bottom silver film was crucial for the tremendous upconversion enhancement since it gave rise to a pronounced absorption peak and resulted in a strong field confinement of the 980 nm excitation light. Comparing with the nanodisk, the nanoring performed better in enhancing the upconversion, and an enhancement factor of ∼3.2 × 104 was achieved based on the numerical and theoretical analysis. This metamaterial system provided a novel approach in enhancing upconversion, and the research findings could be helpful to the design of biosensor and photovoltaic devices.

Strong electric and magnetic dipole in infrared region and higher order multi-pole resonance at visible wavelengths are observed in all-dielectric nanoring metasurfaces. We discuss some of the parameters that influence the optical response of the dielectric nanoring. Adjustment of nanoring radius (inner radius and outer radius) and height can change the absorption intensity and the resonance peaks. Dipole, quadrupole, six-pole and ten-pole resonance modes can be found in the silicon nanoring at resonance wavelength. The transmission spectrum of nanoring with high Q-factor and contrast is achieved with appropriate parameters. Further the nanoring is used to application of sensing in which the sensitivity reaches 228 nm/RIU. This research is an important step to understand resonance in silicon nanoring and paves way for designing some optic devices such as sensor, nanoantennas, and photovoltaics.

In this issue of Chem, Cheung et al. have produced armchair (12,12) and chiral (18,12) carbon nanobelts through the Scholl reaction of carbon nanoring precursors. The design of the carbon nanorings is key to the successful synthesis of the carbon nanobelts., ファイル公開：2020-04-11

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.

Fe 3 O 4 nanoring (NR) composites anchored on the nanolayers of expanded graphite (EG) were prepared through solvothermal–surface modification–sintering approach to break Snoek's limit. The samples were characterized by XRD, EDX, XPS, FESEM, TEM, STEM, and Raman spectroscopy analyses. Fe 3 O 4 NR content, NR size, and EG size were well adjusted by changing precursor mass and size and ball milling EG for various times. The composites exhibited controllable saturation magnetization and remarkably enhanced permittivity and permeability. A proper Fe 3 O 4 content (6.38 wt.%–22.12 wt.%), large EG size, and large NR size favor the enhancement of permeability and permittivity due to the synergistic effect of easy-plane anisotropy, high magnetization ( M s ), microcurrent induced plasmonic resonance, and microcurrent induced electromagnetic coupling. Specifically, the composites exhibit light weight, strong absorption, and broad-absorbing band compared with those of pure EG and Fe 3 O 4 NRs. The optimal microwave absorption property was found in composites containing 29.82 wt.% Fe 3 O 4 with a minimum R L value of −45.8 dB at 8.55 GHz, frequency range ( R L ≤ −20 dB, 99% absorption) of 12.97 GHz, and mass fraction of 10 wt.%. This work provides a significant guide for designing and synthesizing microwave absorbers with high Snoek's limit, broad bandwidth, and light weight.

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.

We have studied the effects of surface shape anisotropy in the magnetization behavior of a torus nanoring by means of Monte Carlo simulations. Stable states (vortex and reverse vortex states) and metastable states (onion and asymmetric onion states) were found in the torus nanoring. The probability of occurrence of the metastable states (stable states) tends to decrease (increase) as the amount of Monte Carlo steps per spin, temperature steps and negative values of the anisotropy constant increase. We evaluated under which conditions it is possible to switch the magnetic state of the torus nanoring from a vortex to a reverse vortex state by applying a circular magnetic field at certain temperature interval. The switching probability (from a vortex to a reverse vortex state) depends on the value of the current intensity, which generates the circular magnetic field, and the temperature interval where the magnetic field is applied. There is a linear relationship between the current intensity and the minimum temperature interval above which the vortex state can be switched.

With the aim of developing a new sort of highly effective and eco-friendly catalyst for NOx abatement, 40 wt.% 12-tungstophosphoric acid (TPA)-decorated Fe 2 O 3 nanorings were synthesized via a microwave-assisted hydrothermal method followed by simple mechanical-chemistry grinding. Analyses of SEM,TEM and XRD demonstrated the successful synthesis of Fe 2 O 3 nanorings. HRTEM image manifested that 3 layers of TPA polyanions were coated on the external surface of Fe 2 O 3 nanorings. FTIR and NH 3 -TPD were also employed to characterize the loading of TPA on Fe 2 O 3 and the distribution of acid sites of the composite material. The results indicated the existence of interaction between the terminal oxygen of TPA and Fe 3+ of Fe 2 O 3 nanorings. H 2 -TPR and SCR experiment showed that TPA played a significant promotion role in the SCR reaction of NOx, while Fe 2 O 3 served not only as the active ingredient but also as the support of TPA. TPA/Fe 2 O 3 achieved a satisfactory SCR performance, with the NOx conversion higher than 92% maintained in a wide temperature range between 230 and 500 °C. Additionally, the catalyst exhibited an excellent SO 2 -resistance capacity.

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.

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.

By changing the constituent amino acid residues, peptide nanorings (PNRs) are expected to be applicable to molecular separation technology. In this paper, chiral recognition of guest amino acids by a host PNR is studied using ab initio calculations. We designed a theoretical host PNR consisting of four glycine and two d -asparagine residues that would work as a chiral selector even if the guest amino acid is protonated or deprotonated. We then considered the energy stability of the PNR complexes with the D and L bodies of guest amino acids. The PNR showed enhanced properties that could allow for chiral recognition of guest amino acids with polar and dissociable side chains at any solvent pH.

The eigenstates of a hydrogenic complex confined in a washer-shaped quantum ring with lateral position-controllable protuberances with a Gaussian aspect under the presence of crossed magnetic and electric probes were calculated. The size and position of the protuberances affect significantly the degree of the electron localization observable in Aharonov-Bohm and Stark-like patterns. The influence of the size of the protuberances, off-centered impurities, and in-plane electric fields on the localization of states was studied in detail. Finally, based on the electron mobility, a mechanism to detect narrow intervals of electric fields thorough the measurement of nanoscopic loop-currents as a function of the non-uniform washer-shaped quantum ring morphology was studied.

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.

The effects of electron-impurity interaction on energy levels and far-infrared absorption in semiconductor nanoring under the action of intense laser and lateral electric fields have been investigated. Numerical calculations are performed using exact diagonalization technique. It is found that the electron-impurity interaction and external fields change the energy spectrum dramatically, and also have significant influence on the absorption spectrum. Strong dependence on laser field intensity and electric field of lowest energy levels, also supported by the Coulomb interaction with impurity, is clearly revealed.

We designed an ingenious plasmonic core-shell-satellite nanostructure (HPGNPs@mSiO2-AuNR) including a hollow porous gold nanoshell (HPGNP) core, a protective silica shell with mesoporous (mSiO2) interlayer, and a high level of gold nanoring (AuNR) satellite coverage by in situ etching. The HPGNP core modified with 4-mercaptobenzoic acid (4-MBA) possessed relatively strong local-field enhancement. The mSiO2 coating acted as a continuous interior nanogap and protective shell, and the variable external satellites in the morphology had tunable optical responses and designed “hotspot” regions. Specifically, AuNR satellites exhibited superior plasmonic properties, intense core-satellite plasmon coupling with the HPGNP core, and favorable biocompatibility. Meanwhile, the nanoassemblies had larger surface-to-volume ratios for molecular modification and were penetrable for analyte. With their abundant built-in hotspots and less hindrance for analyte penetration into the hollow interior, the labeled nanoassemblies were successfully used in SERS/fluorescence sensing system for carcinoembryonic antigen (CEA) detection. These immunoprobes with high SERS activity could be used in SERS-based immunoassay for CEA detection with a linear response ranging from 1 pg/mL to 1000 pg/mL. CEA detection in the fluorescence sensing system showed that the fluorescence quenching efficiency gradually decreased as the CEA level increased, with a linear response of 0.5–400 pg/mL. This SERS/fluorescence-based immunoassay had the same CEA detection limit of 0.1 pg/mL. The fine-engineered penetrable nanoassemblies with Au ring satellites can provide an insight into the rational and optimal design of multifunctional nanostructures. They can also broaden the field of vision for the design of multifunctional sensing probes in biochemical detection.

The absorption and scattering efficiencies of light by a single magnetoplasmonic nanoparticle, based on magnetite and gold, embedded in human tissue are analyzed theoretically in the framework of Finite-Difference-Time-Domain method and Lorenz-Mie theory. We consider separately three different architectures for the magnetoplasmonic nanoparticle: rectangular three-layer gold/magnetite/gold nanobar, circular three-layer gold/magnetite/gold nanoring and magnetite/gold core/shell nanosphere. We address the influence of particle sizes and magnetite-layer and gold-layer thicknesses on the optical response of such nanostructures. Particular attention is paid to the effectiveness of these designed nanostructures in photothermal therapy. Our simulation shows that these hybrid nanostructures support the famous localized surface plasmon resonance mode of gold, which manifests itself in the absorption spectrum by an intense peak whose spectral position can be adjusted to be in the first and second NIR-biological windows. The magnitude of the resonant absorption peak as well as that of the corresponding scattering peak vary from one nanostructure to another and, for the same nanostructure, change with its characteristic sizes. The three-layer nanobars as well as the three-layer nanorings can support significant absorption accompanied by significant scattering of light into both NIR-biological windows. For core/shell nanospheres, the low scattering efficiency of light within the second NIR-biological window, together with their large sizes, limit the usefulness of these nanostructures in photothermal therapy operating in the first NIR-biological window only.

The α-arsenene nanoring (α-AsNRing) is constructed and the adsorption behavior of aromatic compounds (ACs) namely, 1,3-Diethylbenzene (DEB) and 3-Ethyltoluene (ET) on α-AsNRing is explored using the ab-initio method. The base substrate α-AsNRing exhibits semiconductor nature with the energy gap of 0.302 eV. Initially, the structural and dynamical stableness of α-AsNRing was authenticated using cohesive formation energy (-3.682 eV/atom) and phonon-band-spectrum, respectively. The electronic characteristics of α-AsNRing are explored in terms of the projected density of states spectrum and band structure. Besides, three prominent interaction sites (bridge, hollow, and top-site) of ACs on α-AsNRing are identified. The interactions of DEB and ET on α-AsNRing are explored by dominant factors such as binding energy, average band gap changes, and Bader charge transfer. The binding energy of global minima sites is noticed in the range between −0.125 eV and −0.581 eV referring to the physisorption nature of interaction on α-AsNRing. The findings confirm that α-AsNRing can be practically deployed as a chemiresistor (chemical sensor) to sense the ACs in the surroundings.

Stress anisotropy guided controllable morphologies in core–shell nanowires are investigated by linear stability analyses and three dimensional dynamic simulations. Our results reveal that various morphologies including nanoring array, helically ordered quantum dots, and longitudinally oriented quantum wire array on the nanowire substrate can be obtained by tuning the stress anisotropy via applied stress to the nanowire. In the presence of elastic anisotropy regulating the orientation of the core–shell nanowire is another efficient way toward growth of ordered morphologies. Our studies demonstrate the possibility of stress anisotropy tailoring self-organized morphologies in core–shell nanostructures.

A novel hierarchical 3D Ti–Fe–O nanorings/nanotube structure (H–Ti–Fe–O NN) has been fabricated by in situ multi-stepped anodization, which exhibited obviously enhanced visible-light photoelectrochemical (PEC) activity. This performance was benefited from the unique 3D structure that the upper nanoring layer provided visible-light trapping capability by multiple light reflection/scattering and bottom nanotube array provided the improved carrier mobility. In addition, the heterojunction of Fe2O3 and TiO2 further contributed to the effective charge separation.

We demonstrate a simple and high-performance laser-assisted technique for silver nanoring fabrication, which includes the ablation of the Ag film by focused nanosecond pulses and subsequent reactive ion polishing. The nanoring diameter and thickness can be controlled by optimizing both the pulse energy and the metal film thickness at laser ablation step, while the subsequent reactive ion polishing provides the ability to fabricate the nanoring with desirable height. Scattering patterns of s-polarized collimated laser beam obliquely illuminating the nanoring demonstrate the focal spot inside the nanoring shifted from its center at a distance of ~0.57 R ring . Five-fold enhancement of the photoluminescence signal from the Rhodamine 6G organic dye near the Ag nanoring was demonstrated. This enhancement was attributed to the increase of the electromagnetic field amplitude near the nanoring surface arising from excitation of the multipole plasmon modes traveling along the nanoring. This assumption was confirmed by dark-field back-scattering spectrum of the nanoring measured under white-light illumination, as well as by supporting finite-difference time-domain simulations.

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.

The dynamic susceptibility spectra of torus nanoring with a perpendicular or canted external DC magnetic field are studied by means of micromagnetic simulation. Due to the shape anisotropy of the torus nanoring, the system has a vortex spin structure when there is no external DC magnetic field, and the imaginary part of the dynamic susceptibility shows a single resonance peak. With the increase of DC magnetic field which is perpendicular to the plane of the ring, the resonant frequency decreases firstly and then increases monotonically. When the angle between the direction of the DC magnetic field and the center axis of the nanoring increases, the imaginary part of the magnetic susceptibility gradually shows one low frequency and three high frequency resonance peaks. By calculating the dynamic magnetic susceptibility of different parts of the nanoring, the corresponding region of each resonance mode is determined. Finally, we also discuss the effect of size on the magnetic susceptibility of the torus nanoring.

Nanorings are prone to folding as a result of the competition between van der Waals interactions and mechanical rigidity, and thus have promising potential applications in reprogrammable/reconfigurable and strain engineering fields. A small-deformation continuum model is proposed to investigate the folding of nanorings and to predict their critical radii for stable folding. The critical radius of a nanoring is found to be dependent on the ratio of the component nanotube bending stiffness to the inter-tube binding energy, both of which are dependent on the radius of the component nanotube. The unfolding of folded nanorings by annealing is also studied through molecular dynamics simulations.

We explored the potential application of kekulene nanoring in the anode of Li-ion batteries using B3LYP-gCP-D3/6-31G* model chemistry. Molecular electrostatic potential analysis indicates a current density alternatively on the kekulene hexagons, being compatible with the Clar’s aromaticity model. Li atom or cation prefer deposit above the aromatic rings with adsorption energies of −53.4 or −21.4 kcal/mol. The maximum deformation energy upon the Li/Li+ adsorption is 5.2 kcal/mol, demonstrating that the kekulene nanoring preserves its initial geometry during the adsorption process. The Li cation has to overwhelm a small maximum energy barrier of 4.7 kcal/mol to migrate in the kekulene surface, indicating an ultra-high ion mobility. The specific capacity and cell voltage are predicted to be 504.6 mAh/g and 1.38 V, respectively. Thus, the large cell voltage, high ion mobility, and great storage capacity make the kekulene a plausible candidate for application as an anode material of Li-ion batteries.

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.

A magnetic skyrmion is a small magnetic whirlpool, in which the local magnetic moments point in a concerted manner forming a nontrivial spin arrangement. This topological spin texture has been predicted to behave as a composite particle with finite mass. The mass effect plays a key role in describing skyrmion dynamics. In this paper, we put forward a method to measure the mass of a skyrmion. This measurement is realized by forming a simple harmonic oscillator in a semicircular nanoring, in which a skyrmion oscillates like a particle in a simple pendulum. Then we verify the method by using micromagnetic simulations.

In this paper, the Cu2O/TiO2 heterostructure is composed of Cu2O particles and TiO2 nanoring/nanotube(R/T). The high order TiO2(R/T) were prepared by two-step anodization. With small diameter Cu2O particles deposited on the TiO2(R/T) by a simple thermal decomposition process, the photoelectrochemical properties of the TiO2(R/T) has been enhanced. As-prepared samples were characterized by scanning electron microscopy, X-ray diffraction and energy dispersive spectrometer. The photoelectrochemical behavior of the samples was studied through electrochemical impedance spectroscopy and photo-to-current conversion efficiency measurement. It was found that the combination of Cu2O with TiO2(R/T) could not only improve the carrier separation efficiency, but also extend the optical response range of TiO2(R/T) to the visible light region. Finally, the mechanism that Cu2O can enhance the photoelectrochemical properties of TiO2(R/T) is discussed.

This article presents an efficient method for the design of a sensor combining localized surface plasmon resonance (LSPR) sensing with quartz crystal microbalance with dissipation monitoring (QCM-D). The sensor uses a quartz crystal coated with 7 mm radium transparent indium tin oxide (ITO) top electrode and 6 mm radium gold bottom electrode. An array of gold nanorings is fabricated on the surface of ITO electrode. The gold nanoring arrays cause 12.11 Hz frequency shift which is very small compared with 5 MHz resonance frequency. The mass sensitivity profiles of various types of “n-m” electrode sensors are compared using MATLAB and the results show that the “7-6” is more sensitive than others. Finite element modeling in ANSYS shows good sensitivity to low relative permittivity in range from 1 to 10.

A kinetic Monte Carlo model of droplet epitaxy is suggested and realized. A basis for the Monte Carlo model is the vapor–liquid–solid mechanism. The proposed model was used for the analysis of GaAs nanostructure formation mechanism during crystallization of Ga drops under the arsenic flux. The dependences of the grown structure morphology on temperature, As 2 flux intensity and GaAs substrate surface orientation were analyzed. Depending on temperature and arsenic flux intensity, different shapes of nanostructures (crystal dots, core–shell compact clusters, nanoholes and nanorings) were achieved. A lack of etching of GaAs substrates with (1 1 1)А and (1 1 1)В surface orientations by liquid gallium was revealed. Nanohole and nanoring formation was observed only on substrates with (0 0 1) surface orientation. The kinetics of nanoring formation was examined.

In this study, we have investigated the optical properties and spectral response of an isolated aluminum nanoring in pure and compositional regimes. The effects of geometrical and chemical modifications regarding examined Al nanoparticle have been studied theoretically and numerically using a finite-difference time-domain (FDTD) method. Changing the structural sizes of the pure Al nanoring, modifications in the thickness of covering oxide layer, and utilizing various substrates with different permittivities ( e ) have been considered as the key factors which have dramatic influences on the scattering efficiency of the structure. Considering nanoring strategic structural versatility, the peak of scattering intensity can be adjusted and shifted to the desired spectrum, and this opportunity allows us to red-shift the dipolar plasmon resonance extreme from the UV to the visible and near infrared region (NIR) efficiently. Utilizing Al nanoring with appropriate geometrical sizes and the oxide layer thickness of 48% and glass substrate to design a plasmonic dimer nanostructure, we investigated the quality of plasmon resonance peak shifting along the wavelength variations (from UV to NIR). Considering studied nanoparticles in dimer regime (composed of Al/Al 2 O 3 /SiO 2 ), we measured the LSPR sensitivity of the structure while the configuration is immersed in dielectric liquid substances. Using different materials with different refractive indices as a surrounding medium, we plotted a linear figure of merit (FoM=5.9) for the configuration to quantify the LSPR sensitivity. It is shown that proposed nanostructure has a strong potential to exploit in designing CMOS-compatible plasmonic devices, localized surface plasmon resonance (LSPR) sensing and biochemical sensing nanostructures, and SERS applications.