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At the micro and nanoscales, thermo-elastic damping is regarded as one of the most crucial factors for promoting energy dissipation in vibrating structures. The thermo-elastic damping of a thin rotational ring resonator is explored in this paper based on three phase lag heat conduction model for thermal relaxations and nonclassical elasticity for small scale effects. Solving the heat conduction equation for radial direction heat flow and zero heat flux boundary conditions yields the temperature spread across ring cross-section. The equation takes into account only the rotating narrow ring's in-plane vibrations. For the frequency dependent thermo-elastic damping, the combined nonlocal thermo-elasto-dynamic equations are solved. The present model is validated with the experimental and finite element data. The thermo-elastic damping of rotating rings has been found to be over predicted by classical elasticity. For a particular small scale factor, as rotational speed rises by 80%, the equivalent thermo-elastic damping of the ring resonator reduces by 43%. In addition, the effects of cross-sectional shape, nonlocal scale factor, rotating speed, modenumber, ambient temperature, and substance on thermo-elastic damping are thoroughly explored in this work. The results presented here are useful to build and construct future nanoscale resonant sensors and radio-frequency devices. [ABSTRACT FROM AUTHOR]

This research explored the behavior of glass when bombarded by high-energy radiation, especially electron beams inside transmission electron microscopy (TEM). Six types of glasses are investigated under e-beam. The work is conducted using three types of TEMs of energies of 120, 200, and 300 keV. The findings show that these microscopies have a significant impact on the glass, as various observations were documented. Using a wide electron beam, morphology changes combined with bubble formation are observed in the glass. These changes are rounding and smoothening of glass edges and surfaces. In addition, the findings show that there is no material loss due to irradiation as confirmed by the energy dispersive X-ray spectroscopy. The results also show that high silica glass is very sensitive, while high boron glass is found to be less sensitive to irradiation. Using a smaller size electron beam, on the other hand, resulted in the fabrication of a nanoring/nanocrater in glass. The possible applications of this research can be in the protection and packaging of three-dimensional electronic equipment and nanoscale pattern formation through roughening of the external glass contour through phase separation and the opposite through local changing of a part of the glass through the pseudo-melting and the stability of loaded and un-loaded glasses to the irradiation. Furthermore, by generating a nanoring or a nanocrater through e-beam, the lithography process is successfully performed, as the effect of the electron beam is solely at the irradiation region, while the regions outside the e-beam remain unaffected. [ABSTRACT FROM AUTHOR]

Sensors play a critical role in improving overall human quality of life. They have been employed in most aspects of our lives. A recently emerging sensing platform is based on plasmonic resonance at the boundary of metals and dielectrics. Localized surface plasmon resonances–based sensors offer miniaturization, a simple setup, and relatively high sensitivity for real-time measurements. The reported figure of merit (FOM) of the LSPR-based sensor is generally limited, primarily due to its broad resonance peak. Nanorings composed of metal nanoparticles are known for their broad-range resonance tunability, high field localization, and large sensing area. Asymmetry of the nanoring with the introduction of core offset relaxes the selection rule for mode mixing, thus resulting in a narrower resonance peak. This may overcome broad resonance peak restriction. Concentric and non-concentric nanorings were simulated using the boundary element method implemented with the MNPBEM toolbox. We map the performance of nanoring sensors over a wide range of geometrical variations, namely, diameter, ring shell thickness, and the offset of the inner ring to the center of the outer ring wall (core offset). Sensitivity and FOM were found to rely substantially on the nanoring size parameters. The sensing performance map helps to obtain optimized nanoring parameters for the intended spectral range region. The obtained high sensitivity and FOM are much higher than the data available in the literature over visible and NIR ranges. The findings demonstrate the potential of nanorings for biosensing applications. Doi: 10.28991/ESJ-2023-07-04-04 Full Text: PDF

This research explored the behavior of glass when bombarded by high-energy radiation, especially electron beams inside transmission electron microscopy (TEM). Six types of glasses are investigated under e-beam. The work is conducted using three types of TEMs of energies of 120, 200, and 300 keV. The findings show that these microscopies have a significant impact on the glass, as various observations were documented. Using a wide electron beam, morphology changes combined with bubble formation are observed in the glass. These changes are rounding and smoothening of glass edges and surfaces. In addition, the findings show that there is no material loss due to irradiation as confirmed by the energy dispersive X-ray spectroscopy. The results also show that high silica glass is very sensitive, while high boron glass is found to be less sensitive to irradiation. Using a smaller size electron beam, on the other hand, resulted in the fabrication of a nanoring/nanocrater in glass. The possible applications of this research can be in the protection and packaging of three-dimensional electronic equipment and nanoscale pattern formation through roughening of the external glass contour through phase separation and the opposite through local changing of a part of the glass through the pseudo-melting and the stability of loaded and un-loaded glasses to the irradiation. Furthermore, by generating a nanoring or a nanocrater through e-beam, the lithography process is successfully performed, as the effect of the electron beam is solely at the irradiation region, while the regions outside the e-beam remain unaffected

An approach to modulating the properties of carbon nanorings by incorporating pyrrolo[3,2‐b]pyrrole units is of particular interest due to the combined effect of heteroatom and antiaromatic character on electronic properties. The inclusion of units other than phenylene leads to the formation of stereoisomers. In this work, we computationally study how the spatial orientation of monomeric units in the ring affects the properties of cyclic dibenzopyrrolo[3,2‐b]pyrroles and their complexes with C60 fullerene. For [4]PP and [4]DHPP, the most symmetrical AAAA isomer is the most stable and forms stronger interactions with fullerene than the isomers where one or two monomeric units are flipped, mostly due to less Pauli repulsion. π‐Electron delocalization in the monomeric unit is crucial for directing the electron transfer (from or to nanoring). The energy of excited states with charge transfer depends on the HOMO–LUMO gap, which varies from one stereoisomer to another only for [4]DHPP⊃C60 with aromatic 1,4‐dihydropyrrolo[3,2‐b]pyrrole units. The rates of electron transfer and charge recombination reactions are relatively weakly dependent of the spatial isomerism of nanorings. [ABSTRACT FROM AUTHOR]

In the model of effective masses and rectangular potentials for an electron and a hole, the influence of a uniform electric field on the energy spectrum and wave functions of the exciton and the oscillator strengths of interband quantum transitions in the semiconductor (GaAs/AlxGa1-xAs) quantum dot-quantum ring nanostructure is theoretically investigated. The stationary Schrödinger equations for noninteracting quasiparticles in the presence of an electric field cannot be solved analytically. For their approximate solution, the unknown wave functions are sought in the form of an expansion over the complete set of cylindrically symmetric wave functions, and the electron energy is found by solving the corresponding secular equation. The exciton binding energy is found using perturbation theory. The dependences of the energy spectra, the wave functions of an electron, hole, and exciton, and the intensity of interband optical quantum transitions on the magnitude of the electric field strength are analyzed.

Rings of porphyrins mimic natural light‐harvesting chlorophyll arrays and offer insights into electronic delocalization, providing a motivation for creating larger nanorings with closely spaced porphyrin units. Here, we demonstrate the first synthesis of a macrocycle consisting entirely of 5,15‐linked porphyrins. This porphyrin octadecamer was constructed using a covalent six‐armed template, made by cobalt‐catalyzed cyclotrimerization of an H‐shaped tolan with porphyrin trimer ends. The porphyrins around the circumference of the nanoring were linked together by intramolecular oxidative meso‐meso coupling and partial β‐β fusion, to give a nanoring consisting of six edge‐fused zinc(II) porphyrin dimer units and six un‐fused nickel(II) porphyrins. STM imaging on a gold surface confirms the size and shape of the spoked 18‐porphyrin nanoring (calculated diameter: 4.7 nm). [ABSTRACT FROM AUTHOR]

In this paper, a plasmonic refractive index sensor based on metal–insulator-metal (MIM) topology in the form of a nanoring was investigated for the detection of prostate-specific antigen (PSA), which was validated using the finite-difference time-domain (FDTD) three-dimensional numerical equation method. We have tried to get the most optimal state of the nanoring-shaped sensor using various simulations. Here, two different types of metals (Au and Ag) in two different shapes of ring and disk were examined. The results of this study show the superiority of nanoring-shaped sensors to disk and the relative superiority of Ag to Au. The highest sensitivity and FOM for detecting PSA in the Ag nanoring shape are 567.23 and 3.72 nm/RIU, respectively, while these values are 478.34 and 2.91 nm/RIU for disk shapes, respectively. The wavelength range of the sensor is very close to the information communication window. In addition to its remarkable sensor capability, it can also be used in optical electronics applications such as optical switching, amplifiers, and all-optical plasmon modulators. [ABSTRACT FROM AUTHOR]

The ascertainment of magnetic aromaticity is not necessarily straightforward, especially for large and bent systems, such as the cycloporphyrin nanorings recently synthesized by the group of Anderson. Six of these cycloporphyrin nanorings were studied here computationally. Indirect methods, based on nuclear shielding and magnetizabilities, and direct methods, based on standard quantum mechanics, were both used effectively to determine their magnetically induced current strength, which mostly confirmed Anderson’s classification. However, in the case of hexanions, and in particular for cyclohexaporphyrin hexacations, a significant cancellation of delocalized diatropic and paratropic flow occurred, showing that the resultant faint aromatic character was a result of competing aromatic and antiaromatic contributions, as also evidenced by the ipsocentric method. A warning is renewed on the use of isotropic shielding to determine the tropicity of the magnetically induced current.

Fe3O4 nanoparticles have been widely used as drug carriers, but their toxicity is rarely reported. Herein, we compared the toxicity of novel Fe3O4 nanorings, nanotubes and conventional Fe3O4 nanospheres. The structure, morphology and magnetic properties of Fe3O4 nanoparticles were characterized via X-ray diffraction, scanning electron microscope and vibrating sample magnetometer. Scanning electron microscope images revealed that the morphologies of Fe3O4 particles were annular, tubular or spherical. The magnetic property measurements demonstrated that saturation magnetization values of nanorings, nanotubes and nanospheres were 85.3, 90.1 and 74.8 emu/g, respectively. In addition, the cytotoxic effects on the 264.7 mouse macrophages cells of Fe3O4 nanorings, nanotubes and nanospheres were determined by cck-8 test and TUNEL staining assay. Cell viability was slightly decreased on spherical Fe3O4 nanoparticles compared to annular and tubular Fe3O4 nanoparticles. Fe3O4 nanospheres are synthesized by one-step synthesis method. Nanorings and nanotubes are first synthesized into Fe3O4 nanoparticles by hydrothermal method and then reduced to Fe3O4 nanoparticles. The synthesis method of nanotubes is basically the same as that of nanorings, the only difference is the amount of NH4H2PO4 added. Hollow nanostructured materials (compare with nanospheres) can reduce particle sedimentation agglomeration and toxicity. [ABSTRACT FROM AUTHOR]

Iron oxide (maghemite and magnetite) nanoparticles are the most commonly used magnetic materials in nanomedicine because of their high biocompatibility. However, their low saturation magnetization (60–90 emu/g) limits their applicability. Here, we report a new core–shell (Fe@FexOy) nanoring system, which combines the high magnetic saturation of a metallic iron core (220 emu/g) and the biocompatibility of an iron oxide shell. To produce these nanostructures, hematite (α-Fe2O3) nanorings were annealed in a H2 gas atmosphere for different periods to optimize the amount of metallic iron percentage (δ) in the system. Thus, nanostructures with different magnetic saturation (97 to 178 emu/g) could be obtained; based on their metallic iron content, these particles are labeled as Vortex Iron oxide Particle δ (VIPδ). Micromagnetic simulations confirmed that the VIPδ nanorings exhibit a vortex configuration, guaranteeing low remanence and coercitivity. Moreover, the system shows good biocompatibility in various assays as determined through cell viability measurements performed using two different human cell lines, which were exposed to VIP78% for 24 h. Therefore, VIPδ nanorings combine a magnetic vortex state and biocompatibility with their high magnetic saturation and can thus serve as a platform that can be tuned during the synthesis based on desired biomedical application.

Large conjugated rings with persistent currents are novel promising structures in molecular‐scale electronics. A six‐porphyrin nanoring structure that allegedly sustained an aromatic ring current involving 78π electrons was recently synthesized. We provide here compelling evidence that this molecule is not aromatic, contrary to what was inferred from the analysis of 1H‐NMR data and computational calculations that suffer from large delocalization errors. The main reason behind the absence of an aromatic ring current in these nanorings is the low delocalization in the transition from the porphyrins to the bridging butadiyne linkers, which disrupts the overall conjugated circuit. These results highlight the importance of choosing a suitable computational method to study large conjugated molecules and the appropriate aromaticity descriptors to identify the part of the molecule responsible for the loss of aromaticity. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The ascertainment of magnetic aromaticity is not necessarily straightforward, especially for large and bent systems, such as the cycloporphyrin nanorings recently synthesized by the group of Anderson. Six of these cycloporphyrin nanorings were studied here computationally. Indirect methods, based on nuclear shielding and magnetizabilities, and direct methods, based on standard quantum mechanics, were both used effectively to determine their magnetically induced current strength, which mostly confirmed Anderson's classification. However, in the case of hexanions, and in particular for cyclohexaporphyrin hexacations, a significant cancellation of delocalized diatropic and paratropic flow occurred, showing that the resultant faint aromatic character was a result of competing aromatic and antiaromatic contributions, as also evidenced by the ipsocentric method. A warning is renewed on the use of isotropic shielding to determine the tropicity of the magnetically induced current. [ABSTRACT FROM AUTHOR]

The influence of a homogeneous electric field on the exciton energy spectrum and the intensity of interband quantum transitions in double semiconductor (GaAs/AlxGa1–xAs) cylindrical quantum rings has been studied. Assuming that the lattice constant and the dielectric constant of the nanosystem elements differ slightly from each other, a model of effective masses and rectangular potentials is used to calculate the electron and hole spectra. The corresponding stationary Schrödinger equations for non-interacting electrons and holes in the absence of an electric field are solved analytically exactly. Radial wave functions are obtained as a linear combination of the Bessel, Neumann and modified Bessel functions. The stationary Schrödinger equations for quasiparticles in the presence of an electric field are not analytically solved. For their approximate solution, the unknown wave functions are sought in the form of an expansion over a complete set of cylindrically symmetric wave functions, and the energy of an electron or a hole is found from the solution of the corresponding secular equation. Since the interaction energy between an electron and a hole is much less than the sum of the size-quantized energies of the corresponding quasiparticles, the exciton binding energy is found using perturbation theory. The dependences of the energies of an electron, a hole, and an exciton on the magnitude of the electric field strength are analyzed. It is shown that the electric field significantly affects the localization of quasiparticles in the system of double nanorings. In this case, both the energies of an electron, a hole, and an exciton and the intensities of interband quantum transitions nonmonotonically depend on the magnitude of the electric field strength. [ABSTRACT FROM AUTHOR]

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

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

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. [ABSTRACT FROM AUTHOR]

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

Abstract We demonstrate the existence of Fano resonance spectral response in a system of nanoscale plasmonic resonant ring stacked by means of a half nanoring. Our proposed scheme exploits the stacked method under normal incidence to excite the subradiant mode. The nanostructure, which utilizes the combination of Fano resonance and polarization-resolved, has a new rotation mode and high tunability, providing a dynamic control of plasmonic spectral response. High-quality resonant line shapes corresponding to the different order modes of Fano structures are readily achieved at near-infrared wavelengths, which is a benefit to the application for nanosensor in highly integrated circuits.

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

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

The electronic and adsorption properties of dimethyl and methyl-ethyl ester molecules on a silicene nanoring (SiNR) are studied using first-principles calculations. The adsorption properties of dimethyl and methyl-ethyl ester molecules on the surface of a silicene nanoring is investigated in terms of density of states spectrum, adsorption energy, average energy gap variation, Mulliken charge and Bader charge transfer. The structural stability of the SiNR is ensured using formation energy. The variation in the electron density and energy gap is noticed upon adsorption of dimethyl and methyl-ethyl ester molecules in the SiNR base material compared with its isolated counterpart. The highlights of the present work are silicene nanoring is used as a base material for ester molecule adsorption. The adsorption behavior of ester molecules is studied using energy band structure. The DOS spectrum confirms the transfer of electrons between the SiNR and ester molecules. The findings suggest that a SiNR can be used as a base material for the detection of dimethyl and methyl-ethyl ester molecules. [ABSTRACT FROM AUTHOR]

The effect of homogeneous electric field on the energy spectrum, wave functions of electron and oscillator strengths of intra-band quantum transitions in a double cylindrical quantum ring (GaAs/AlxGai- xAs) is studied within the approximations of effective mass and rectangular potentials. The calculations are performed using the method of expansion of quasiparticle wave function over a complete set of cylindrical wave functions obtained as exact solutions ofSchrodinger equation for an electron in a nanostructure without electric field. It is shown that the electric field essentially affects the electron localization in the rings of a nanostructure. Herein, the electron energies and oscillator strengths of intra-band quantum transitions non-monotonously depend on the intensity of electric field. [ABSTRACT FROM AUTHOR]

Background: The need for practical and adaptable terahertz sources is apparent in the areas of application such as early cancer diagnostics, nondestructive inspection of pharmaceutical tablets, visualization of concealed objects. We outline the operation principle and suggest the design of a simple appliance for generating terahertz radiation by a system of nanoobjects – gold nanobars (GNBs) or nanorings (GNRs) – irradiated by microwaves.Results: Our estimations confirm a feasibility of the idea that GNBs and GNRs irradiated by microwaves could become terahertz emitters with photon energies within the full width at half maximum of the longitudinal acoustic phononic DOS of gold (ca. 16–19 meV, i.e., 3.9–4.6 THz). A scheme of the terahertz radiation source is suggested based on the domestic microwave oven irradiating a substrate with multiple deposited GNBs or GNRs.Conclusion: The size of a nanoobject for optimal conversion is estimated to be approx. 3 nm (thickness) by approx. 100 nm (length of GNB, or along the GNR). This detailed prediction is open to experimental verification. An impact is expected onto further studies of interplay between atomic vibrations and electromagnetic waves in nanoobjects.

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.

Proteins unfold in chaotropic salt solutions, a process that is difficult to observe at the single protein level. The work presented here demonstrates that a liquid-based atomic force microscope and graphene liquid-cell-based scanning transmission electron microscope make it possible to observe chemically induced protein unfolding. To illustrate this capability, ferritin proteins were deposited on a graphene surface, and the concentration-dependent urea- or guanidinium-induced changes of morphology were monitored for holo-ferritin with its ferrihydrite core as well as apo-ferritin without this core. Depending on the chaotropic agent the liquid-based imaging setup captured an unexpected transformation of natively folded holo-ferritin proteins into rings after urea treatment but not after guanidinium treatment. Urea treatment of apo-ferritin did not result in nanorings, confirming that nanorings are a specific signature of denaturation of holo-ferritins after exposture to sufficiently high urea concentrations. Mapping the in situ images with molecular dynamics simulations of ferritin subunits in urea solutions suggests that electrostatic destabilization triggers denaturation of ferritin as urea makes direct contact with the protein and also disrupts the water H-bonding network in the ferritin solvation shell. Our findings deepen the understanding of protein denaturation studied using label-free techniques operating at the solid-liquid interface.

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

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

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

A novel plasmonic mirror-image nanoepsilon ( MINE) structure is studied to achieve significantly enhanced and localized near-field. It is well-known that the nanorod dimer is able to gain a high local field at the center of the structure by adjusting its rod width, rod length, and gap distance. When adopting an auxiliary nanoring structure electron reservoirs surrounding the nanorod-dimer to form the MINE structure, the local field can be further enhanced owing to a large amount of charges into sharp dimer structure which can confine the accumulation of charges to apexes. Thus, better synergistic interaction of gap effect and lightning-rod effect can be achieved for high field enhancement around nanoscale gap. The symmetric mode in the MINE structure enables strong near-field with a concentrated distribution around the gap. The influences of rod-tip angle and gap distance on the optical properties of plasmonic MINE structures are numerically investigated. With reducing the rod-tip angle and gap distance, considerable enhancements on the field intensities at the rod tips and the gap center can be attributed to the improved lightning-rod and gap effects. The near-field intensities at the rod tip and gap center are dramatically enlarged ~1.94 × 10 and ~1.41 × 10 times with the rod-tip angle of 41° and gap distance of 10 nm, and the near-field is localized within an extremely small range. These features are very beneficial for various plasmonic applications. [ABSTRACT FROM AUTHOR]

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

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

This letter, for the first time, investigates interactive logic cell schemes and transistor architecture scaling options for 5-nm technology node (N5) and beyond. The proposed novel transistors, such as Hexagonal NanoWire (NW) and NanoRing (NR) architectures, are introduced having higher current drivability and lower parasitic capacitance than conventional NW or NanoSlab devices. The standard cell sizing options, including a 1-fin-per-device version and a 2-fin-per-device design, are systematically evaluated. Each device flavor has multiple vertical stacks when wire-like or slab-like structure is used. Comprehensive transistor and logic cell studies demonstrate that the novel NR is the optimal structure for N5 and beyond. [ABSTRACT FROM AUTHOR]

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