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In this work, different structures are designed based on graphene square-nanoring resonator (GSNR) and simulated by the three-dimensional finite-difference time-domain (3D-FDTD) method. Depending on the location and number of graphene nanoribbons (GNR), the proposed structures can be utilized as a band-pass filter, wavelength demultiplexer, or power splitter in the mid-infrared (MIR) wavelengths. The tunability of the suggested assemblies is easily controlled by changing the dimensions and/or the chemical potential of the GSNRs. Benefiting from the nanoscale and ultra-compact GNRs, these structures can be proposed as basic blocks for optical computing and signal processing in the MIR region.

In this work, the thermoelastic dissipation (TED) for circular-cross-sectional micro/nanoring model is studied including the single-phase-lag (SPL) time based on the non-Fourier heat conduction model. The toroidal solid ring is simple to manufacture and thus the potential is high for future development. Also, the present model is more precise than the 1D or 2D beam or rectangular-cross-sectional ring because the governing equation is established by 3D coordinate system. Moreover, the SPL shows the delay time of heat-flux and is especially important in cryogenic or ultrafast-vibration environments. In this regard, characteristics of the TED is mainly analyzed according to the lagging time, geometrical shape, mode number and temperature, etc. Using the experimental data in literatures, the effectiveness of this work is verified to represent the investigations. The spectra of the TED with the phenomenon of multiple peaks are presented, and then the results can be grouped and compared with previous works. Moreover, the temperature distribution is graphically described to explain the SPL mechanism.

The first example of a neutral spin‐delocalized carbon‐nanoring radical was achieved by integration of the open‐shell phenalenyl unit into cycloparaphenylene (CPP). Spin distribution in this hydrocarbon is localized primarily on the phenalenyl segment and partially on the CPP segment as a consequence of steric and electronic effects. The resulting geometry is reminiscent of a diamond ring, with pseudo‐perpendicular arrangement of the radial and the planar π‐surface. The phenylene rings attached directly to the phenalenyl unit give rise to a steric effect that governs a highly selective dimerization pathway, yielding a giant double nanohoop. Its π‐framework made of 158 sp2‐carbon atoms was elucidated by single‐crystal X‐ray diffraction, which revealed a three‐segment CPP‐peropyrene‐CPP structure. This nanocarbon shows a fluorescence profile characteristic of peropyrene, regardless of which segment gets excited. These results in conjunction with DFT suggest that adjusting the size of the CPP segments in this double nanohoop could deliver donor–acceptor systems., A neutral open‐shell carbon nanoring was achieved by integration of the phenalenyl unit into the cycloparaphenylene framework. It is shown that the spin distribution and reactivity of this hydrocarbon in the shape of a diamond ring are a result of steric and electronic effects and that selective dimerization yields a double nanohoop with a radial‐planar‐radial arrangement of its three π‐conjugated segments comprising a total of 158 sp2‐carbon atoms.

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

We report a novel strategy for the synthesis of Pt@Au nanorings possessing near-field focusing capabilities at the center through which single-particle surface enhanced Raman scattering could be readily observed. We utilized Pt@Au nanorings as a light-absorber; the absorbed light could be focused at the center with the aid of a Au nanoporous structure. We synthesized the Au nanolens structure through a Galvanic exchange process between Au ions and Ag block at the inner domain of the Pt@Au nanoring. For this step, Ag was selectively pre-deposited at the inner domain of the Pt@Au nanorings through electrochemical potential-tuned growth control and different surface energies with regard to the inner and outer boundaries of the nanoring. Then, the central nanoporous architecture was fabricated through the Galvanic exchange of sacrificial Ag with Au ions leading to the resulting Au nanoring with a Au nanoporous structure at the center. We monitored the shape-transformation by observing their corresponding localized surface plasmon resonance (LSPR) profiles. By varying the rim thickness of the starting Pt@Au nanorings, the inner diameter of the nanolens was accordingly tuned to maximize near-field focusing, which enabled us to obtain the reproducible and light-polarization independent measurements of single-particle SERS. Through theoretical simulation, the near-field electromagnetic field focusing capability was visualized and confirmed through single-particle SERS measurement showing an enhancement factor of 1.9 × 108 to 1.0 × 109., We synthesized a Au nanolens with electromagnetic near-field focusing capability by integrating a Au nanoporous structure at the center of the Pt@Au nanoring via synthetic steps of eccentric growth of Ag and nanoscale Galvanic exchange reaction.

The melamine·barbiturate H-bonded rosette motif is of comparable dimensions and symmetry to the cavity of a butadiyne-linked 6-porphyrin nanoring. Functionalisation of each of the barbiturate components and the pyrimidine components of a H-bonded rosette with a pyridine ligand leads to a self-assembled hexapyridine ligand, which binds cooperatively to the zinc porphyrin nanoring. UV-vis-NIR and 1H NMR experiments show that the 7-component assembly forms at concentrations at which neither the H-bonding interactions nor the zinc porphyrin–pyridine interactions are formed in the absence of one of the three components. The mean effective molarities of these rosette complexes are around 200 mM in chloroform at 298 K., Mixing barbiturates and pyrimidines equipped with pyridine ligands to leads to self-assembly of a hexadentate rosette ligand, which is complementary to a hexameric zinc porphyrin macrocycle.

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

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

In this work, a novel reduction-responsive disulfide bond-containing cycloparaphenylene nanoring molecule (DSCPP) with a pyriform shape has been designed. In addition, the interactions between the designed nanoring (host) and fullerenes C60 and C70 (guests) were investigated theoretically at the M06-2X/6-31G(d,p) and M06-L/MIDI! levels of theory. By analyzing geometric characteristics and host–guest binding energies, it is revealed that the designed DSCPP is an ideal host molecule of guests C60 and C70. DSCPP presents excellent elastic deformation during the encapsulation of C60 and C70. The high binding energies suggest that both DSCPP⊃C60 and DSCPP⊃C70 (∼92 and 118 kJ·mol–1 at the M06-2X/6-31G(d,p) level of theory) are stable host–guest complexes, and the guest C70 is more strongly encapsulated than C60 in the gas phase. The thermodynamic information indicates that the formation of the two host–guest complexes is thermodynamically spontaneous. In addition, the frontier molecular orbital (FMO) features and intermolecular weak interaction region between DSCPP and fullerenes gusts are discussed to further understand the structures and properties of the DSCPP⊃fullerene systems. Finally, the ring-opening mechanism of the DSCPP under reduction conditions is investigated.

International audience; For the last ten years, ring-shaped -conjugated macrocycles possessing radially directed -orbitals have been subject to intense research. The electronic properties of these rings are deeply dependent on their size. However, most studies involve the flagship family of nanorings: the cyclo-para-phenylenes. We report herein the synthesis and study of the first examples of cyclofluorenes possessing five constituting fluorene units. The structural, optical and electrochemical properties were elucidated by X-ray crystallography, UV-vis absorption and fluorescence spectroscopy, and cyclic voltammetry. By comparison with a shorter analogue, [4]-cyclofluorene, we show how the electronic properties of [5]-cyclofluorenes are drastically different from those of [4]-cyclofluorenes, highlighting the key role played by the ring size in the cyclofluorene family.

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

Hydrogen can be produced by photoelectrochemical (PEC) water splitting using a KOH solution as an electrolyte and TiO2 as a photoanode. In this work, we fabricated anatase TiO2 nanoring/nanotube arrays and TiO2 nanotube arrays using an anodic oxidation method, confirmed by field-emission scanning electron microscopy (FESEM) and X-ray diffractometry (XRD), and then conducted the photoelectrochemical experiments with 1 M KOH and Na2SO4 solutions. The bias voltage, small impedance, negative flat-band potential, large capacitance, and depletion layer width in the anatase TiO2-KOH system were observed, leading to the stable and large photocurrent density. To understand the effects of KOH on the interface properties of TiO2/H2O, the electric double layers of anatase TiO2(001), (100), (101)/KOH interfaces were further investigated by calculating the ion-surface interaction with molecular dynamics simulations. It is noted that the number density of potassium ions has the same trend as that of oxygen atoms due to the layering effect in liquids and the strongest ionic hydration of K+ on anatase (101) is observed by analyzing the radial distribution function and coordination number. In addition, the electrostatic characteristics along the TiO2/KOH interfaces were analyzed based on the Grahame double layer model. The potential drops in the outer Helmholtz layer of anatase (001), (100), and (101) surfaces are 1.08, 0.26, and 0.51 V, respectively. Compared with TiO2-H2O systems, the larger potential drops in the TiO2-KOH system explain the phenomenon that KOH solute contributes substantially to a chemical bias in PEC reactions. At the same time, we estimated the depletion layer widths of anatase TiO2(001), (100), and (101) surfaces as 37.48, 173.25, and 64.49 A, respectively, which are of similar magnitude to the experimental results. Anatase TiO2(100) with the widest depletion layer is suggested in photocatalysis. These works provide a clear understanding of interfacial behavior of KOH on anatase TiO2 from a microscale, which can be used to explain the promotion effect of the KOH electrolyte and guide the design of TiO2 nanocrystals in the PEC system.

Frequency selective absorbing property (FSAP) is a key to realize radar frequency selective surfaces' stealth technology, which has great application prospects in national military industry. Different from traditional metal materials, herein, through the design of polyaniline microstructure as well as doping modification of the polymerization, polyaniline nanorings (PANI NRs) with certain electrical conductivity have been constructed. By constructing nanoring-shaped morphology, PANI NRs achieve strong reflection and great absorption of electromagnetic waves (EMWs) in different frequency ranges. These two properties are vital for realizing high-efficient FSAP. PANI NRs demonstrate negative permittivity within 50–1000 MHz frequency range where they can show strong EMWs reflection, and the negative permittivity is attributed to the plasma-like behavior of conductive network formed by plenty of overlapping nanorings. In addition, this porous structure also contributes to increase reflection and refraction of incident EMWs and then continuously consuming their energy, ensuring outstanding EMWs absorption property during 2–18 GHz frequency bandwidth.

Large-scale application of sustainable energy devices urgently requires cost-effective electrocatalysts to overcome the sluggish kinetics related to the oxygen evolution reaction (OER) under acidic conditions. Here, we first report the highly efficient electrocatalytic characteristics of α-Fe2O3 nanorings (NRs), which exhibits prominent OER electrocatalytic activity with lower overpotential of 1.43 V at 10 mA cm−2 and great stability in 1 M HCl, surpassing the start-of-the art Ir/C electrocatalyst. The significantly optimized OER activity of the α-Fe2O3 NRs mainly attributes to the synergistic effect of the excellent electrical conductivity and a large effective active surface because of their unique nanoring structure, disordered surface, and the dynamic stability of α-Fe2O3 NRs in acidic conditions.

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

We present an aluminum (Al) laminated nanostructure stacked on a glass substrate to produce highly transmitted narrowband ultraviolet (UV) filters. The laminated nanostructure was mainly composed of an Al nanohole array, and each Al nanohole had a coaxial Al nanoring at the bottom. This UV filter showed a single dominant peak with a high transmission over 50% and a narrow bandwidth less than 80 nm in the 200–400 nm waveband that was achieved based on the synergy of surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR). The electric field profiles of the laminated nanostructure indicate that SPR selects the transmission wavelength and LSPR contributes to single peak. This narrowband UV filter can be utilized in UV detectors.

A recent Research Article published in this journal by Matito and coworkers claimed that none of the oxidation states of a butadiyne-linked six-porphyrin nanoring exhibit global aromaticity or antiaromaticity. Here we show that this conclusion is incorrect. A combination of density functional theory (DFT) calculations and experimental NMR data provides compelling evidence for global (anti)aromaticity in a variety of six-porphyrin nanorings in their 2+, 4+ and 6+ oxidation states. The strength of the predicted ring current depends on the choice of DFT functional, so it is crucial to use a functional that reproduces the experimental 1H NMR chemical shifts in these cations.

A new member of the cycloparaphenylene double-nanohoop family was synthesized. Its π-framework features two oval cavities that display different shapes depending on the crystallization conditions. Incorporation of the peropyrene bridge within the nanoring cycles via bay-regions alleviates steric effects and thus allows 1:1 complexation with C60 in the solid state. This nanocarbon adopts a lamellar packing motif, and our results suggest that the structural adjustment of this double nanohoop could enable its use in supramolecular and semiconductive materials.

An optical refractive index sensor is a detection device that can convert changes in the refractive index into detectable optical information. The combination of surface plasmon resonance (SPR) and Fano resonance can improve some key indicators, i. e., sensing sensitivity, figure of merit (FOM), band number, and polarization sensitivity, which are all related to the comprehensive performance for high-precision and multi-band sensing. In our manuscript, we proposed a refractive index sensor composed of a nanoring array and a Fabry-Pérot (F-P) resonant cavity. The coupling of the localized surface plasmon resonances (LSPR) of the nanoring array and the cavity mode of the F-P resonant cavity can produce double Fano resonances. The corresponding sensing sensitivities can reach 621.5 nm/RIU and 906.9 nm/RIU, and the corresponding FOMs can reach 119.7 and 119.0. Then we studied the influence of the structure parameters on the sensitivity and FOM of the sensor through simulation calculation and theoretical analysis and verified the insensitivity of the structure to the polarization of incident light. Our structure has high comprehensive performance, not only polarization insensitivity but also high sensing sensitivity and FOM in both bands, which is more suitable for practical applications.

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

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

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

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.

Open in a separate window The focus of the work is the synthesis of SnS2 nanomaterials with (peg-SnS2NF) and without (sf-SnS2NR) the involvement of the organic template and the comparative study of their catalytic activities. The synthesis of these materials was achieved in a single-step procedure aided by hexamethyldisilazane (HMDS). These nanoparticles were subjected to X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, and UV–vis spectroscopy analyses to investigate their structural, topographical, surface, and optical properties. The present work suggests that the surfactant-free SnS2 nanoring (sf-SnS2NR) catalyst has lower surface area compared to the poly(ethylene glycol)-stabilized SnS2 nanoflower (peg-SnS2NF) catalyst but shows high activity under visible light for the photoreduction of Cr(VI) and the photocatalytic degradation of organic dyes. The work exposed the importance of the clean surfaces on the catalyst and is expected to have a high impact on the photocatalytic activity of the SnS2 nanomaterial. The study also endorses the utility of the HMDS-assisted synthetic method for the production of multifunctional semiconductor tin disulfide nanomaterials with multiple potential applications.

One method to increase bit density in magnetic memory devices is to use multi-state structures, such as a ferromagnetic nanoring with multiple domain walls (DWs), to encode information. However, there is a competition between decreasing the ring size in order to more densely pack bits and increasing it to make multiple DWs stable. This paper examines the effects of ring geometry, specifically inner and outer diameters (ODs), on the formation of 360° DWs. By sequentially increasing the strength of an applied circular magnetic field, we examine how DWs form under the applied field and whether they remain when the field is returned to zero. We examine the relationships between field strength, number of walls initially formed, and the stability of these walls at zero field for different ring geometries. We demonstrate that there is a lower limit of 200 nm to the ring diameter for the formation of any 360° DWs under an applied field, and that a high number of 360° DWs are stable at remanence only for narrow rings with large ODs.