Self-assembly of Quasi-monocrystal CdCO_3 Nanorings

Hierarchical CdCO3 nanostructures with complex morphologies, such as tetragonal, pentagonal and hexagonal nanorings, can be prepared via self-assembly of nanocrystals in a solvothermal environment. XRD pattern indicated that the product is trigonal CdCO3 phase （PDF#850989） with cell constants a = 6.112 A and a = 47.4°. Based on our experimental results, a possible nanoring formation mechanism was proposed.

A novel one-step method to synthesize copper nitrate hydroxide nanorings

With the purpose of searching for a convenient process to synthesize nanoparticles with special structure,a simple solid-state reaction in the presence of nonionic surfactant OP-10 at room temperature was adopted to prepare copper nitrate hydroxide(Cu_(2)(OH)_(3)NO_(3))nanorings with an average internal diameter of 250 nm and average wall thickness of 100 nm.The formation of Cu_(2)(OH)_(3)NO_(3) nanorings has a close relation with OP-10.Transmission electron microscopy(TEM),field emission scanning electron microscopy(FESEM),thermogravimetric analysis(TGA)and X-ray diffractometry(XRD)were used to characterize the obtained nanorings.The UV-Vis spectrum shows that the optical property of Cu_(2)(OH)_(3)NO_(3) nanorings is similar to that of CuO or CuS.The synthesis method used here proves both simplicity and high efficiency.

Ultrasonic synthesis, characterization and formation mechanism of aggregated nanorings of EuF_3

The aggregated nanorings of EuF3 were synthesized via ultrasonic irritation in aqueous solution. The products were characterized by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. XRD pattern proved that the crystalline phase of the EuF3 rings was hexagonal. The SEM and TEM images indicated that the as-prepared EuF3 nanocrystals had ring-like morphology and were aggregated by numerous small crystallites （about 10-15 nm in diameter）; the outer diameter of the rings was in the range of 200--300 nm, while the inner diameter was in the range of 50-80 nm with a thickness of 30-40 nm. Moreover, the time-depend experiments were carried out to disclose the formation mechanism of the as-prepared ring-like nanostructures.

Novel magnetic vortex nanorings/nanodiscs: Synthesis and theranostic applications

Recent discoveries in the synthesis and applications of magnetic vortex nanorings/nanodiscs in theranostic applications are reviewed. First, the principles of nanomagnetism and magnetic vortex are introduced. Second, methods for producing magnetic vortex nanorings/nanodiscs are presented. Finally, theranostic applications of magnetic vortex nanorings/nanodiscs are addressed.

Persistent currents in three-dimensional shell-doped nanorings

The persistent current in three-dimensional （P × N2） nanorings as a function of the unit cell number （P）, the channel number （M =N2）, surface disorder （ζ）, and temperature （T） is theoretically investigated in terms of rotational symmetry. On the whole, the typical current increases linearly with √M but decreases exponentially with P, while wide fluctuations exist therein. In the presence of surface disorder, the persistent current decreases with ζ in the regime of weak disorder but increases in the regime of strong disorder. In addition, it is found that the persistent current in perfect rings decreases exponentially with temperature even at T 〈 T＊, while in most disorder rings, the typical current decreases slightly with temperature at T 〈 T＊.

Electromagnetic wave absorption in reduced graphene oxide functionalized with Fe3O4/Fe nanorings

We report the preparation of nanocomposites of reduced graphene oxide with embedded Fe3O4/Fe nanorings （FeNR@rGO） by chemical hydrothermal growth. We illustrate the use of these nanocomposites as novel electromagnetic wave absorbing materials. The electromagnetic wave absorption properties of the nanocomposites with different compositions were investigated. The preparation procedure and nanocomposite composition were optimized to achieve the best electromagnetic wave absorption properties. Nanocomposites with a GO：cx-Fe203 mass ratio of 1：1 prepared by annealing in HdAr for 3 h exhibited the best properties. This nanocomposite sample （thickness = 4.0 mm） showed a minimum reflectivity of -23.09 dB at 9.16 GHz. The band range was 7.4-11.3 GHz when the reflectivity was less than -10 dB and the spectrum width was up to 3.9 GHz. These figures of merit are typically of the same order of magnitude when compared to the values shown by traditional ferric oxide materials. However, FeNR@rGO can be readily applied as a microwave absorbing material because the production method we propose is highly compatible with mass production standards.

Graphitic nanorings for super-long lifespan lithium-ion capacitors

Porous graphitic carbon nanorings(PGCNs)are proposed by smart catalytic graphitization of nano-sized graphene quantum dots(GQDs).The as-prepared PGCNs show unique ring-like morphology with diameter around 10 nm,and demonstrate extraordinary mesoporous structure,controllable graphitization degree and highly defective nature.The mechanism from GQDs to PGCNs is proven to be a dissolution-precipitation process,undergoing the procedure of amorphous carbon,intermediate phase,graphitic carbon nanorings and graphitic carbon nanosheets.Further,the relationship between particles size of GQDs precursor and graphitization degree of PGCNs products is revealed.The unique microstructure implies PGCNs a broad prospect for energy storage application.When applied as negative electrode materials in dual-carbon lithium-ion capacitors,high energy density(77.6 Wh·kg^(−1))and super long lifespan(89.5%retention after 40,000 cycles at 5.0 A·g^(−1))are obtained.The energy density still maintains at 24.5 Wh·kg^(−1)even at the power density of 14.1 kW·kg^(−1),demonstrating excellent rate capability.The distinct microstructure of PGCNs together with the strategy for catalytic conversion from nanocarbon precursors to carbon nanorings opens a new window for carbon materials in electrochemical energy storage.

Efficient adsorption of europium(Ⅲ)and uranium(Ⅵ)by titanate nanorings:Insights into radioactive metal species

Radioactive wastewater containing high concentration of radionuclides poses severe threats to ecosystem and human health,so efficient removal of these toxic heavy metals is urgently needed.Titanate nanomaterials have been demonstrated good adsorbents for heavy metals due to ion exchange property.In this study,titanate nanorings(TNRs)were synthesized using the facile hydrothermal-cooling method.The TNRs were composed of sodium trititanate,with a chemical formula of Na_(0.66)H_(1.34)-Ti_(3)O_(7)·0.27H_(2)O and a Na content of 2.38 mmol/g.The TNRs demonstrated sufficient adsorption performance to radionuclides europium(Eu)and uranium(U)ions.Specifically,even at a high initial concentration of 50 mg/L,86.5% and 92.6% of the two metal ions can be rapidly adsorbed by the TNRs within 5 min,and equilibrium was reached within 60 min at pH 5.The maximum adsorption capacity(Qmax)obtained by the Langmuir isotherm model was 115.3 mg/g for Eu(Ⅲ)and 282.5 mg/g for uranium U(Ⅵ)at pH 5,respectively.The adsorption capacities of the two metals under various water chemical conditions were highly related to their species.Ion exchange between metal cations and Na^(+) in the TNR interlayers was the dominant adsorption mechanism,and adsorption of U(Ⅵ)was more complicated because of the co-existence of various uranyl(UO_(2)^(2+))and uranyl-hydroxyl species.The spent TNRs were effectively regenerated through an acid-base or ethylenediamine tetraacetic acid(EDTA)treatment and reused.Considering the large adsorption capacity and quick kinetic,TNRs are promising materials to remove radionuclides in environmental purification applications,especially emergent treatment of leaked radionuclides.

All-inorganic dual-phase halide perovskite nanorings

In the present work,we report the growth of all-inorganic perovskite nanorings with dual compositional phases of CsPbBr_(3)and CsPb_(2)Br5 via a facile hot injection process.The self-coiling of CsPbBr_(3)-CsPb_(2)Br5 nanorings is driven by the axial stress generated on the outside surface of the as-synthesized nanobelts,which results from the lattice mismatch during the transformation of CsPbBr_(3)to CsPb_(2)Br5.The tailored growth of nanorings could be achieved by adjusting the key experimental parameters such as reaction temperature,reaction time and stirring speed during the cooling process.The photoluminescence intensity and quantum yield of nanorings are higher than those of CsPbBr_(3)nanobelts,accompanied by a narrower full width at half maximum(FWHM),suggesting their high potential for constructing self-assembled optoelectronic nanodevices.

Chlorine doped graphitic carbon nitride nanorings as an efficient photoresponsive catalyst for water oxidation and organic decomposition

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 m V at current density of 10 m A cm^-2 and Tafel slope of 83 m V 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 m V and 28 m V 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.

S incorporated RuO_(2)-based nanorings for active and stable water oxidation in acid

The design of highly active and stable RuO_(2)-based nanostructures for acidic oxygen evolution reaction(OER)is extremely important for the development of water electrolysis technology,yet remains great challenges.We here demonstrate that the incorporation of S into RuCuO nanorings(NRs)can significantly enhance the acidic OER performance.Experimental investigations show that the incorporation of S can optimize the interaction of Ru and O,and therefore significantly suppresses the dissolution of Ru in acidic condition.The optimized catalyst(SH-RuCuO NRs)displays superior OER performance to the commercial RuO_(2)/C.Impressively,the SH-RuCuO NRs can exhibit significantly enhanced stability for 3,000 cycles of cyclic voltammetry test and more than 250 h chronopotentiometry test at 10 mA·cm^(-2)in 0.5 M H_(2)SO_(4).This work highlights a potential strategy for designing active and stable RuO_(2)-based electrocatalysts for acidic OER.

Electrochemical Fabrication of rGO-embedded Ag-TiO2 Nanoring/Nanotube Arrays for Plasmonic Solar Water Splitting

Effective utilization of hot electrons generated from the decay of surface plasmon resonance in metal nanoparticles is conductive to improve solar water splitting efficiency.Herein,Ag nanoparticles and reduced graphene oxide(rGO)co-decorated hierarchical TiO2 nanoring/nanotube arrays(TiO2 R/T)were facilely fabricated by using two-step electrochemical anodization,electrodeposition,and photoreduction methods.Comparative studies were conducted to elucidate the effects of rGO and Ag on the morphology,photoresponse,charge transfer,and photoelectric properties of TiO2.Firstly,scanning electron microscope images confirm that the Ag nanoparticles adhered on TiO2 R/T and TiO2 R/T-rGO have similar diameter of 20 nm except for TiO2 R-rGO/T.Then,the UV-Vis DRS and scatter spectra reveal that the optical property of the Ag-TiO2 R/T-rGO ternary composite is enhanced,ascribing to the visible light absorption of plasmonic Ag nanoparticles and the weakening effect of rGO on light scattering.Meanwhile,intensity-modulated photocurrent spectroscopy and photoluminescence spectra demonstrate that rGO can promote the hot electrons transfer from Ag nanoparticles to Ti substrate,reducing the photogenerated electron-hole recombination.Finally,Ag-TiO2 R/T-rGO photoanode exhibits high photocurrent density(0.98 mA cm?2)and photovoltage(0.90 V),and the stable H2 evolution rate of 413μL h?1 cm?2 within 1.5 h under AM 1.5 which exceeds by 1.30 times than that of pristine TiO2 R/T.In line with the above results,this work provides a reliable route synergizing rGO with plasmonic metal nanoparticles for photocatalysis,in which,rGO presents a broad absorption spectrum and effective photogenerated electrons transfer.

Topological structure effect on far-infrared spectra in a GaAs/InAs nanoring

On the basis of the growth mechanism of a GaAs/InAs nanoring, we propose a fine model which reflects the confinement details of real nanoring. Through calculations of the two-electron energy and far-infrared （FIR） spectra, we find that the ring topological structure and electron-electron interaction have great influence on the FIR spectra. The two unknown transition peaks in the experiment are determined theoretically. The theoretical results are in good agreement with the experiments.

Carbon Nanobelts:Brief History and Perspective

Carbon nanotubes(CNTs)are an emerging nanomaterial because of their outstanding performance in various applications.In recent years,the segment molecules of CNTs,referred to as carbon nanorings(CNRs)or carbon nanobelts(CNBs),have gained attention for their unique structures and properties,as well as their potential as seed molecules for the precise synthesis of CNTs.CNBs are rigid and thick segments of CNTs whose synthesis has been addressed by scientists fascinated by the uniqueness of CNBs long before the discovery of CNTs.After 60 years of efforts by synthetic chemists all over the world,the synthesis of the first CNB,(6,6)CNB,was achieved by our group in 2017.Since this milestone,diverse types of nanobelts have been synthesized through various synthetic routes,thereby demonstrating their photophysical,magnetic,and redox properties derived from rigid belt structures.The applications of CNBs have also been introduced recently.The formation of the host−guest complex,transformation to three-dimensional molecules,and measurement of conductivity have been reported for CNBs.This paper summarizes the brief history and perspective of CNBs.Further synthetic campaigns and aggressive application of CNBs would create novel and groundbreaking scenes in materials science.

Polymer-assisted fabrication of gold nanoring arrays

In this paper, we report a new strategy for the fabrication of gold nanoring arrays via colloidal lithography and polymer-assisted self-assembly of gold nanoparticles （Au NPs）. First, multi-segmented polymer nanorod arrays were fabricated via colloidal lithography. They were then used as templates for Au NP adsorption, which resulted in nanoparticles on the poly（4-vinyl pyridine） （P4VP） segments. Continuous gold nanorings were formed after electroless deposition of gold. The diameter, quantity, and spacing of the gold nanorings could be tuned. Three dimensional coaxial gold nanorings with varying diameters could be fabricated on a polymer nanorod by modifying the etch parameters. The nanorings exhibited optical plasmonic resonances at theoretically predicted wavelengths. In addition, the polymer-assisted gold nanorings were released from the substrate to generate a high yield of flee-standing nanorings. This simple, versatile method was also used to prepare nanorings from other metals such as palladium.

Designing a dual-functional material with barrier anti-corrosion and photocatalytic antifouling properties using g-C_(3)N_(4) nanosheet with ZnO nanoring

As a semiconductor material with a 2 D-laminate structure, g-C_(3)N_(4)(bandwidth 2.7 e V) has a similar structure and excellent performance to graphene. However, high surface energy and photogenerated e–h recombination of g-C_(3)N_(4)seriously hinder its application in the field of marine anticorrosion and antifouling.To solve these problems, we synthesized the g-C_(3)N_(4)nanosheets decorated with Zn O nanoring via chemical etching technology. Whether the NR Zn O-CNNs have surface protection performance among the pure EP on the corrosion protection for metal substrate were investigated. The antifouling properties NR Zn OCNNs 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 Zn O-CNNs/EP within 45 days showed two orders of magnitude higher than that of pure EP in the 3.5 wt% Na Cl solution. Besides, Local electrochemical impedance spectroscopy(LEIS) further explored the anticorrosion behavior of NR Zn O-CNNs/EP coating, which indicated that the NR Zn O-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 Zn O-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/m L of NR Zn O-CNNs hybrid could make chlorella sharply reduce within 4 days. Simultaneously, the corrosion protection and photocatalytic antifouling mechanisms of NR Zn O-CNNs were proposed, thus it provided a broader platform for the design of versatile marine protection materials.

Au nanoring arrays as surface enhanced Raman spectroscopy substrate for chemical component study of individual atmospheric aerosol particle

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.

Au nanoring arrays with tunable morphological features and plasmonic resonances

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

Phase-field simulation of magnetic double-hole nanoring and its application in random storage

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.

Synthetic Strategies of Carbon Nanobelts and Beyond

Carbon nanobelts(CNBs)with aesthetically appealing molecular structures and outstanding physical properties have attracted more and more attentions from the scientific community due to their potential applications in synthetic materials,host-guest chemistry,optoelectronics,and so on.The synthesis of CNBs at different stages was overviewed and some representative breakthroughs and advances in synthetic strategies were highlighted and discussed.The key issue for the synthesis of CNBs is how to construct curved structures with high strain energy.We not only proposed a few unconventional CNBs as the promising target molecules,but also pointed out the bottom-up synthesis of conjugated tubular segments of carbon nanotubes sharing similar properties as carbon nanotubes is the next focus in this emerging area.