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Shape complementarity is of paramount importance in molecular recognition, but has rarely been adopted in the self-assembly of colloidal particles, especially in the case of nanoparticles of different shapes. Here, we demonstrated a simple, yet powerful strategy for fabricating gold nanoring-based heterogeneous nanostructures (AuNR-HNs) with well-defined geometries and high yield. The assembly of various geometries of AuNR-HNs is modulated by the shape complementarity of plasmonic nanorings and nanospheres. We also present experimental evidence of dark quadrupolar ring mode excitation in AuNR-HNs through single-particle optical measurements. Our strategy will be beneficial in the study of nanoparticle assembly, photonic element interaction, and the development of plasmon-based optical devices.

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

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

DNA nanotechnology can be used to precisely construct nanostructures of different shapes, sizes and surface chemistry, which is appreciated in a variety of areas such as biomaterials, nanodevices, disease diagnosis, imaging, and drug delivery. Enzymatic degradation resistance and cell-targeting capability are indispensable for the applications of DNA nanostructures in biological and biomedical fields, and is challenging to rationally design the desirable nanoscale DNA materials suitable for the clinical translation by the existing assembly methodologies. Herein, we present a simple and efficient method for the hierarchical assembly of a three-level DNA ring-based nanostructure (DNA h-Nanoring) in a precise order, where DNA compositions at the primary level, the second level and the third level are a single DNA ring, two-ring-hybridized duplex and uniform complex macro-cycle, respectively. Most as-assembled DNA h-Nanorings exhibit the regular two-dimensional cycle-shaped structure characterized by atomic force microscopy (AFM). The Nanoring exhibits a significantly enhanced resistance to enzymatic attack, such that it can remain intact in 10% fetal bovine serum (FBS) for 24 h, and even stably exist in the presence of nuclease at a high concentration. More importantly, it is very easy to modify the DNA h-Nanoring with functional moieties (e.g., targeting ligand aptamer) because there are many single-stranded fragments available for further hybridization. By combining with receptor-targeted Sgc8, the nanoring can be used to accomplish the cell imaging and criminate target CEM cells from control cells, demonstrating a potential platform for in vivo tumor imaging and targeted chemotherapeutics delivery.

Combining atomically resolved DNA-templated silver nanoclusters (AgNCs) with nucleic acid nanotechnology opens new exciting possibilities for engineering bioinorganic nanomaterials with uniquely tunable properties. In this unforeseen cooperation, nucleic acids not only drive the formation of AgNCs but also promote their spatial organization in supra-assemblies. In this work, we confirm the feasibility of this approach using programmable RNA rings to control formation and optical properteis of six individual AgNCs. “Red” (λEXC/λEM = 565/623 nm) and “green” (λEXC/λEM = 440/523 nm) emitting AgNCs are templated on cytosine-rich DNA fragments embedded into the RNA rings. Optical properties of the AgNCs formed on the RNA rings are characterized in detail. While all “red” species passively transition to “green” emitters with time, the initial fluorescent properties and relative stabilities of “red” AgNCs can be regulated by altering the relative orientation of AgNCs within the RNA rings. As such, the oxidative stability increases dramatically for AgNC positioned towards the center of the RNA rings rather than facing outward. Overall, our findings expand the existing AgNC fluorescent toolkit while uncovering the complexity of the AgNC electronic structures with the abundance of possibilities for controlling de-excitation processes.

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

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

The effects of CNR diameter and CNR number on tensile properties of the CNR-graphene hybrid structure (CGHS) were studied by molecular dynamics simulation in this paper. Results show that interactions between adjacent graphene sheets are significantly strengthened by the cross-linked CNRs. For CGHSs, the maximum strength is ~64.0 GPa and the maximum Young’s modulus strength is ~763 GPa. When the diameter of CNRs is large or the CNR linkers are dense, the tensile strength of CGHSs reached the maximum and the fracture mechanism of CGHSs changed from CNR-graphene junction fracture to graphene sheet fracture. Present work should serve as guide to experiments concerning physical properties of this novel material.

With the development of advanced nanofabrication technologies over the last decade, plasmonic nanostructures have attracted wide attention for their potential in label-free biosensing applications. However, the sensing performance of nanostructured plasmonic sensors is primarily limited by the broad-linewidth features with low peak-to-dip signal ratio in the extinction spectra that result from strong radiative damping. Here, we propose and systematically investigate the in-plane and out-of-plane dipolar interactions in an array of plasmonic nanoring resonators that are from the spatial combination of classic nanohole and nanodisk structures. Originating from the strong coupling of the dipolar modes from parent nanohole and nanodisk structures, the subradiant lattice plasmon resonance in the nanoring resonator array exhibits narrow-linewidth spectral features with high peak-to-dip signal ratio and strong near-field electromagnetic enhancement, making it an ideal platform for high-sensitivity chemical and bio-medical sensing. We experimentally demonstrate that the plasmonic nanoring resonator array can be used for high-sensitivity refractive index sensing and real-time monitoring of biomolecular specific binding interactions at nanomolar concentration. Moreover, thanks to its simple normal incident illumination scheme and polarization independent optical response, we further transfer the plasmonic nanoring resonator array onto the optical fiber tip to demonstrate an integrated and miniaturized platform for label-free remote biosensing, which implies that the plasmonic nanoring resonator array may be a potential candidate for developing high performance and highly-integrated photonic biosensing systems.

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.

Synthetic strategies of web-above-a-ring (WAR) and web-above-a-lens (WAL) nanostructures are reported. The WAR has a controllable gap between the nanoring core and a nanoweb with nanopores for the effective confinement of electromagnetic field in the nanogap and subsequent surface-enhanced Raman scattering (SERS) of Raman dyes inside the gap with high signal reproducibility, which are attributed to the generation of circular 3D hot zones along the rim of Pt@Au nanorings with wrapping nanoweb architecture. More specifically, Pt@Au nanorings are adopted as a plasmonic core for structural rigidity and built porous nanowebs above them through a controlled combination of galvanic exchange and the Kirkendall effect. Both nanoweb and nanolens structures are also formed on Pt@Au nanoring, which is WAL. structure. Remarkably, plasmonic hot zone, nanopores, and hot lens are formed inside a single WAL nanostructure, and these structural components are orchestrated to generate stronger SERS signals.

The facile assembly of metal nanostructured arrays is a fundamental step in the design of plasmon enhanced chemical sensing and solar cell architectures. Here we have investigated methods of creating controlled formations of two-dimensional periodic arrays comprised of 20 nm Au nanoparticles (NPs) on a hydrophilic polymer surface using particle lithography. To direct the assembly process, capillary force and NP concentration both play critical roles on the resulting nanostructured arrays. As such, tuning these experimental parameters can directly be used to modify the nature of the nanostructures formed. To explore this, two different concentrations of Au NP solutions (~7 x 1011 NPs/mL or 4 x 1012 NPs/mL) were used in conjunction with a fixed concentration of polystyrene microspheres (PS MS, ~ 6 x 109 PS MS/mL). Assembly at a relative humidity (RH) of 45% with the higher concentration resulted in the formation of well-defined Au nanorings of ca. 23 nm in height and 881 nm in diameter with a pitch of 2.5 μ...

Recently, we reported the synthesis of two novel large π-extended carbon nanorings by incorporating hexa-peri-hexabenzocoronenes: cyclo[12]-paraphenylene[2]-2,11-hexa-peri-hexabenzocoronene ([12,2]CPHBC) and the [4]cyclo-2,11-para-hexa-peri-hexabenzocoronene ([4]CHBC). The successful synthesis was achieved by the rationally designed pathways via palladium-, nickel-, or platinum-mediated reactions and the final aromatization reaction. This Synpacts article highlights the synthetic methods to achieve these carbon nanorings with large conjugated systems. We also summarize the representative characterization evidences and interesting photophysical properties of these carbon nanoring structures. Furthermore, the selective supramolecular host–guest interaction between [4]CHBC and C70 is briefly discussed. The new π-extended carbon nanorings can be considered as examples of longitudinal extension of the cycloparaphenylene scaffold, forming large conjugated CNT segments.1 Introduction2 Large π-Extended Carbon Nanorings by Incorporating Hexa-peri-hexabenzocoronenes3 Conclusions

Correction for ‘Biomass-derived interconnected carbon nanoring electrochemical capacitors with high performance in both strongly acidic and alkaline electrolytes’ by Xianjun Wei et al., J. Mater. Chem. A, 2017, 5, 181–188.

A large-scale, uniform array of particle-in-aperture (PIA) hybrid architectures for highly reproducible surface-enhanced Raman spectroscopy (SERS) is rationally designed and prepared via electrostatic self-assembly of Au nanospheres and vertical deposition of Ag. By controlling the thickness of the Ag coating, polarization-independent ring-shaped hot spots with tunable width can be created around individual nanospheres, offering far higher Raman enhancements than a bare Au nanosphere array and a flat Ag film do. Three PIA substrates with different Ag thicknesses and an identical nanosphere diameter of 58 nm were investigated. Consequently, it is found that a 28 nm Ag coating enables the wavelength matching between the plasmonic coupling band and the laser line, leading to an enhancement factor of up to 4.5 × 106. Meanwhile, remarkable reproducibility of SERS signals is realized by ruling out the impact of anomalous hot spots. To this end, three guidelines are meticulously followed, i.e. using monodisperse Au nanospheres, distributing nanoring cavities evenly onto the substrate, and decoupling adjacent nanoparticles by isolating them far away from each other. This work offers a reliable strategy to fabricate high-performance SERS substrates in a simple, cost-effective and scalable manner, paving the way for practical sensing applications, such as quantitative SERS measurements.

A versatile nanosphere composite lithography (NSCL) combining both the advantages of multiple-exposure nanosphere lens lithography (MENSLL) and nanosphere template lithography (NSTL) is demonstrated. By well controlling the development, washing and the drying processes, the nanosphere monolayer can be well retained on the substrate after developing and washing. Thus the NSTL can be performed based on MENSLL to fabricate nanoring, nanocrescent and hierarchical multiple structures. The pattern size and the shape can be systemically tuned by shrinking nanospheres by using dry etching and adjusting the tilted angle. It is a natural nanopattern alignment process and possesses a great potential in the scope of nano-science due to its low cost, simplicity, and versatility for variuos nano-fabrications.

We propose a novel and facile method to fabricate epitaxial ferroelectric BiFeO3 (BFO) nanorings using anodized alumina (AAO) template-assisted PLD and ion-beam etching. The morphology and dimensions of these nanorings are revealed by atomic force microscopy (AFM) and confirmed by transmission electron microscopy (TEM). The typical dimensions of the BFO nanorings are 12 nm inner diameter with 30 nm wall thickness and heights of around 10 nm. The X-ray diffraction (XRD), reciprocal space mapping (RSM) and TEM data demonstrate the epitaxial structure of these nanorings. Moreover, the ferroelectric properties are investigated by piezoresponse force microscopy (PFM), showing the polarization reversal behaviors of the isolated BFO nanorings, which have great potential applications for high-density non-volatile memory devices. In addition, this novel method could also be extended to other material systems (such as BaTiO3, ZnO and Au). Furthermore, the fabrication of high quality nanoring structures may open a pathway to explore related emerging physical phenomena (e.g., ferroelectric vortices).

Gold nanorings are attractive as plasmonic metal nanocrystals because they have a hollow inner cavity. Their enhanced electric field inside the ring cavity is accessible, which is highly desirable for assembling with other optical components and studying their plasmon-coupling behaviors. However, the lack of robust methods for synthesizing size-controllable and uniform Au nanorings severely impedes the study of their attractive plasmonic properties and plasmon-driven applications. Herein, an improved wet-chemistry method is reported for the synthesis of monodisperse colloidal Au nanorings. Using circular Au nanodisks with different thicknesses and diameters as templates, Au nanorings are synthesized with thicknesses varied from ≈30 to ≈50 nm and cavity sizes varied from ≈90 to ≈40 nm. The produced Au nanorings are assembled with colloidal Au nanospheres to yield Au nanoring-nanosphere heterodimers in sphere-in-ring and sphere-on-ring configurations on substrates. The sphere-in-ring heterodimers exhibit the interesting feature of plasmonic Fano resonance upon the excitation of the dark quadrupolar plasmon mode of the Au nanorings. The open cavity in a nanoring holds a great promise for studying plasmon-coupled systems, which will facilitate the construction of advanced metamaterials and high-performance Fano-based devices.

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

We report a facile method for the synthesis of Pt-Pd nanocages and Pt nanorings by conformally coating Pd nanoplates with Pt-based shells using polyol- and water-based protocols, respectively, followed by selective removal of the Pd cores. For the polyol-based system, Pd nanoplates were conformally coated with Pt-Pd alloy shells due to the use of a high reaction temperature of 200 oC and a slow injection rate for the Pt precursor. In comparison, Pt shells were formed on Pd nanoplates (with a larger thickness on the side face than on the top/bottom face) in the water-based system due to the use of a low reaction temperature of 80 oC and the presence of twin boundaries on the side face. As such, the Pd@Pt nanoplates prepared using the polyol- and water-based protocols evolved into Pt-Pd nanocages and Pt nanorings, respectively, when the Pd templates in the cores were selectively removed by wet etching. The wall thickness of the nanocages and the ridge thickness of the nanorings could be reduced down to 1.1 nm and 1.8 nm, respectively, without breaking the hollow structures.

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

We investigate the self-assembly and aggregation behaviors of nanoparticles in hybrid assemblies made from amphiphilic block copolymer tethered nanoparticles using the dissipative particle dynamics (DPD) approach. By varying the arm number of the tethered amphiphilic block copolymers, hydrophobic block chain length, and interaction parameter between nanoparticle and hydrophobic block, different morphological hybrid aggregates are obtained, including branching rod-like micelles, ring-like micelles, disk-like micelles, and vesicles. Most importantly, the nanoparticles aggregate in the various micelles and form nanowires, nanorings, and nanoclusters. Only using amphiphilic block copolymer tethered nanoparticles, hybrid vesicles including patchy vesicles and heterogeneous vesicles are obtained. Moreover, nanoclusters with distinct number of nanoparticles in hybrid disk-like micelles and vesicles are fabricated through controlling the interaction parameter between nanoparticle and hydrophobic block.

We report a new type of nanosphere colloidal lithography to directly fabricate monodisperse silica (SiO2) nanorings by means of reactive ion etching of hollow SiO2 spheres. Detailed TEM, SEM, and AFM structural analysis is complemented by a model describing the geometrical transition from hollow sphere to ring during the etching process. The resulting silica nanorings can be readily redispersed in solution and subsequently serve as universal templates for the synthesis of ring-shaped core-shell nanostructures. As an example we used silica nanorings (with diameter of ∼200 nm) to create a novel plasmonic nanoparticle topology, a silica-Au core-shell nanoring, by self-assembly of Au nanoparticles (20 nm) on the ring's surface. Spectroscopic measurements and finite difference time domain simulations reveal high quality factor multipolar and antibonding surface plasmon resonances in the near-infrared. By loading different types of nanoparticles on the silica core, hybrid and multifunctional composite nanoring structures could be realized for applications such as MRI contrast enhancement, catalysis, drug delivery, plasmonic and magnetic hyperthermia, photoacoustic imaging, and biochemical sensing.

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

(Received 17 June 2014 ; in final form 16 August 2015) Abstract In this paper, we studied the electronic conductance of a carbon nanoring using Green’s function method at the tightbinding approach for different positions of contacts in the presence and absence of magnetic field. The results show that as the conductors approch in the nanoring, the tunneling conductance in the gap region improves. Moreover, applying the magnetic field dramatically influences the conductance spectrum of the nanoring so that the existence of the magnetic field causes the configurations with coinciding conductance to be disarticulated. The study of the carbon nanoring including binary benzene rings indicates that the variation of the position of these benzene rings in the nanoring shifts the positions of anti-resonances in the conductance spectrum.

Molecular dynamics simulations demonstrate that the cut defect can induce and guide the self-assembly of an isolated graphene nanoring (GNR) to form multi-layered funnel morphology. The vdW force is the driving force; the tangent component drives the self-assembly of GNR and the normal component adjusts and maintains the vertical distance between graphene layers, which is two times of the vdW radius. Moreover, the offset π-π stacking aids the adjacent layers to achieve the lowest energy of AB stacking. With different diameters of the annular GNRs, the final configurations experience multilayered cone, funnel and tube-shaped structures. It also illustrates the influence of temperature in the funnel-forming process. The wide gap with two edges beyond the cutoff distance of vdW force can utilize fullerenes to help and induce the assembly of the GNR. Cutting defect fissure would be a new way to induce the self-assembly of isolated graphene to design and fabricate new carbon nanostructures without impurities.

The molecular carbon nanoring, cycloparaphenylene (CPP), is fascinating as a new class of carbonaceous porous solids with the uniform structure of an all-benzene surface., The molecular carbon nanoring, cycloparaphenylene (CPP), is fascinating as a new class of carbonaceous porous solids with the uniform structure of an all-benzene surface. We explored the feasibility of [12]CPP as a carbon-based porous material and uncovered its unique adsorption properties due to its shape and highly nonpolar surface. Unlike other porous carbon solids, [12]CPP shows stepwise adsorption behaviors sensitive to the functionalities of the guest molecules. In situ powder X-ray diffraction and infrared spectra provided insights into how [12]CPP accommodates the guest molecules with structural deformation retaining its structural periodicity during the whole adsorption process, which exemplifies that this molecular nanoring represents an unprecedented carbon-based soft porous solid.

This work was financially supported by the National Nature Science Foundation of China (No: 51302280, 51574286), Natural Science Foundation in Qinghai province (No: 2014-ZJ- 936Q). CAS "Light of West China" Program and Youth Innovation Promotion Association (2016377), CAS. α-Fe2O3 nanoparticle with different morphologies, such as hollow spheres, nanotubes with limited {0001} plane exposed, nanoplates and nanorings with the {0001} plane predominantly exposed, have been synthesised by using NaH2PO4 and urea in a facile hydrothermal method. The mechanism of the morphology evolution from hollow sphere to nanoring has been investigated. It is proposed that the polymerisation of Fe3+/H2PO4− plays an important role in the formation of these morphologies. The adsorption of Cr (VI) from aqueous solution onto these α-Fe2O3 nanoparticles showed that the α-Fe2O3 with nanoring morphology has the highest removal efficiency, and the adsorption capacity reached to 16.9 mg/g. These results indicate that the adsorption mechanism of Cr (VI) onto hematite nanoparticles is a chemisorption process through doubly and triply coordinated hydroxyl groups on the outer surface of α-Fe2O3. Postprint

In this article, we report the formation of nanoring structures on Fe coated substrate and their application in guiding the growth of carbon nanotube (CNT) patterns with hierarchical structures. The formation of nanorings involves the etching of polystyrene (PS) monolayer colloidal crystals (MCCs) under reactive ion etching (RIE), and the redeposition and cross-linkage of the active degradation products at the contact line between the MCCs and the substrate. After washing out the MCCs, insoluble nanorings with hexagonal order on the substrate are developed. The RIE process can control the morphology of the nanorings, as well as the distribution of the Fe element on the substrate; thus, a continuous Fe layer and separated Fe discs on the substrate are created on substrate after washing, depending on the etching time and the shield of MCCs. The surviving Fe element can work as the catalyst to initiate the in situ growth of aligned CNTs in the following chemical vapor deposition (CVD) process, while the Fe element underneath the nanorings keep its inactivity. Eventually, CNT patterns with hierarchical structures are formed. One level originates from the surviving Fe layer; the other level is templated from the nanoring structures, which cause the blank area in the CNT bundles.

Due to their outstanding electronic and mechanical properties, single-walled carbon nanotubes (SWCNTs) are promising nanomaterials for the future generation of optoelectronic devices and composites. However, their scarce solubility limits their application in many technologies that demand solution-processing of high-purity SWCNT samples. Although some non-covalent functionalization approaches have demonstrated their utility in extracting SWCNTs into different media, many of them produce short-lived dispersions or ultimately suffer from contamination by the dispersing agent. Here, we introduce an unprecedented strategy that relies on a cooperative clamping process. When mixing (6,5)SWCNTs with a dinucleoside monomer that is able to self-assemble in nanorings via Watson-Crick base-pairing, a synergistic relationship is established. On one hand, the H-bonded rings are able to associate intimately with SWCNTs by embracing the tube sidewalls, which allows for an efficient SWCNT debundling and for the production of long-lasting SWCNT dispersions of high optical quality along a broad concentration range. On the other, nanoring stability is enhanced in the presence of SWCNTs, which are suitable guests for the ring cavity and contribute to the establishment of multiple cooperative noncovalent interactions. The inhibition of these reversible interactions, by just adding, for instance, a competing solvent for hydrogen-bonding, proved to be a simple and effective method to recover the pristine nanomaterial with no trace of the dispersing agent., Funding from the European Union (ERC-Starting Grants: 279548 (DGR) and 307609 (EMP)), MINECO (Grants: CTQ2014- 57729-P (DGR) and CTQ2014-60541-P (EMP), FPU13/03371 (LdJ), JdC-2015-23531 postdoctoral fellowship (BNO)) and the Comunidad de Madrid (Grant: MAD2D-CM program S2013/ MIT-3007 (EMP)) is gratefully acknowledged. IMDEA Nanociencia acknowledges support from the 'Severo Ochoa' Programme for Centres of Excellence in R&D (MINECO, Grant SEV- 2016-0686).

The morphologies of an azobenzene-bridged biscalix[4]arene organogel (1) in different organic solvents can be photo-reversibly switched between nanofibers and nanorings as well as between closed and open-form vesicles.

Plasmonic nanostructures have become the most promising candidates for biosensing applications because of their miniature sizes, ease of integration, and high-throughput detection. Both propagating and localized surface plasmon modes in the nanostructures have been used for sensing and biomolecular detection. However, to maximize the biosensing potential of nanostructures, the choice of an optimized sensing detection strategy among two plasmon modes depends on the relationship between the biomolecule sizes and field decay length of plasmon modes. Here, we propose and investigate plasmonic coupling on a single-crystalline gold film, wherein there are two distinct optical modes, a gap mode (localized surface plasmon) originating from the parallel coupling of a nanoring and a surface lattice mode (propagating surface plasmon) originating from the anti-parallel coupling of a nanoring in an array. The sensing performances of the above two modes are thoroughly investigated and compared by considering two aspects, i.e., bulk and surface sensitivities. It is demonstrated that there is a reciprocal relationship between bulk and surface sensitivities for two modes, which also illustrates that the surface sensitivity is indispensable to fully describe the sensing performance of nanostructures. Furthermore, due to their different decay lengths, the gap and surface lattice modes on a single optical substrate can achieve simultaneous detection of target analytes with various sizes. Therefore, we can provide a high performance sensing platform based on a metallic nanoring array for a broad range of biomolecules with various sizes.

Graphene paper (GP) has attracted great attention as a heat dissipation material due to its unique thermal transfer property exceeding the limit of graphite. However, the relatively poor thermal transfer properties in the normal direction of GP restricts its wider applications in thermal management. In this work, a 3D bridged carbon nanoring (CNR)/graphene hybrid paper is constructed by the intercalation of polymer carbon source and metal catalyst particles, and the subsequent in situ growth of CNRs in the confined intergallery spaces between graphene sheets through thermal annealing. Further investigation demonstrates that the CNRs are covalently bonded to the graphene sheets and highly improve the thermal transport in the normal direction of the CNR/graphene hybrid paper. This full-carbon architecture shows excellent heat dissipation ability and is much more efficient in removing hot spots than the reduced GP without CNR bridges. This highly thermally conductive CNR/graphene hybrid paper can be easily integrated into next generation commercial high-power electronics and stretchable/foldable devices as high-performance lateral heat spreader materials. This full-carbon architecture also has a great potential in acting as electrodes in supercapacitors or hydrogen storage devices due to the high surface area.

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

The paper presents a method for the high-resolution production of polymer nanopatterns with controllable geometrical parameters by means of a single-spot electron-beam lithography technique. The essence of the method entails the overexposure of a positive-tone resist, spin-coated onto a substrate where nanoscale spots are exposed to an electron beam with a dose greater than 0.1 pC per dot. A single-spot enables the fabrication of a nanoring, while a chain of spots placed at distance of 5–30 nm from each other allows the production of a polymer pattern of complex geometry of sub-10 nm resolution. We demonstrate that in addition to the naturally oxidized silicon substrates, gold-coated substrates can also successfully be used for the single-spot nanopattering technique. An explanation of the results related to the resist overexposure was demonstrated using Monte Carlo simulations. Our nanofabrication method significantly accelerates (up to 10 times) the fabrication rate as compared to conventional lithography on positive-tone resist. This technique can be potentially employed in the electronics industry for the production of nanoprinted lithography molds, etching masks, nanoelectronics, nanophotonics, NEMS and MEMS devices.

We show a novel approach to fabricate plasmonic nanoantennae based on a maskless focused ion beam nanoring patterning process. Antenna nanoarrays with desired outlines are achieved by precisely controlling the geometric parameters during the milling process. Various nanoantenna designs of bow-tie, nanoclusters (pentamers), and ellipsoid shaped satellites surrounded particle lattices are realized. The whole fabrication method is programmable and monolithic since only a one-step milling process is involved. The optical properties are experimentally characterized. Such nanoantennae may find extensive applications in chemical/bio-sensing due to remarkably enhanced near field intensity at the plasmon resonance.

Phase change memory (PCM) is one of the most promising candidates for next-generation nonvolatile memory devices because of its high speed, excellent reliability, and outstanding scalability. However, the high switching current of PCM devices has been a critical hurdle to realize low-power operation. Although one solution is to reduce the switching volume of the memory, the resolution limit of photo- lithography hinders further miniaturization of device dimensions. In this study, we employed unconventional self-assembly geometries obtained from blends of block copolymers (BCPs) to form ring-shaped hollow PCM nanostructures with an ultrasmall contact area between a phase- change material (Ge2Sb2Te5) and a heater (TiN) electrode. The high- density (approximately 0.1 terabits per square inch) PCM nanoring arrays showed extremely small switching current of 2−3 μA. Furthermore, the relatively small reset current of the ring-shaped PCM compared to the pillar-shaped devices is attributed to smaller switching volume, which is well supported by electro-thermal simulation results. This approach may also be extended to other nonvolatile memory device applications such as resistive switching memory and magnetic storage devices, where the control of nanoscale geometry can significantly affect device performances.

The encapsulations of fullerene C70 by carbon-nanorings are of great interest because, unlike the spheroidal C60, several distinct geometrical orientations are possible. Additionally, due to experimental difficulties, there is a great deal of opportunity for the computational efforts to deeply explore the intrinsic nature of π–π noncovalent interactions of the CPP carbon-nanoring⊃fullerene host–guest systems. In this paper, the structures and properties of the host–guest complexes formed with nanoring host [n]cycloparaphenylene (n =10, 11, and 12) ([n]CPP) and guest fullerene C70 were detailed and explored by theoretical calculations. The results showed that three different kinds of quasi-inclusion configurations can be obtained for [10]CPP⊃C70 and [11]CPP⊃C70 host–guest complexes in which C70 is lying, half-lying, and standing in the cavities of the hosts, respectively. However, there are only two kinds of stable configurations for [12]CPP⊃C70 host–guest complexes in which C70 is half-lying and standing ...

Atomically thick and flexible Pt-Cu alloy nanosheets are prepared and loaded with either Pd or Pt to produce sandwich structures or nanoring-like nanosheet structures, respectively. Core-shell alloy nanoparticles containing Rh, Ir, and Ru are also prepared. All of these structures exhibit superior specific and mass activities for the oxidation of formic acid for fuel cells for portable electronic devices as compared to commercial Pd/C catalyst.

Polymer crystallization confined at liquid/liquid (L/L) interface has attracted increasing attention during the past decade. In this study, we show that single-walled carbon nanotubes (SWCNTs) can be bent into ring-shaped structure via a Pickering emulsion method. These SWCNT rings are pinned at L/L interface of nanosized oil droplets suspended in water. When dilute crystalline polymer solution was used as the oil phase, upon cooling, these polymers crystallize onto the SWCNT nanorings. This system thus provides a unique platform to investigate heterogeneous nucleation and crystal growth at L/L interface. Polyethylene, poly( l -lactic acid), and poly(3-hexylthiophene) are used as the crystalline homopolymers. Our results show that heterogeneous nucleation dominates the crystallization process, and nano hybrid shish kebab nanorings have been formed. Despite small diameters of the rings, the previously reported soft epitaxy mechanism still holds. Polyethylene-b-poly(ethylene oxide) has also been patterned onto the SWCNT nanorings, leading to hierarchically ordered nanostructures. The block copolymer-decorated SWCNTs have been used to direct nanoparticle assembly. Our work therefore shows a promising means to produce complex, hierarchical, and functional hybrid materials.

We fabricated a variety of reduced graphene oxide (RGO) nanoring arrays using Au@Pt nanoplates as a pattern mask. RGO nanoflakes were assembled into a 2-dimensional assembly at the water-oil interface, and then various shapes of Au@Pt nanoplates were utilized as a pattern mask in order to convert the RGO into circular, triangular, and hexagonal RGO nanorings.

A microelectrode array has been applied for single cell analysis with relatively high throughput; however, the cells were typically cultured on the microelectrodes under cell-size microwell traps leading to the difficulty in the functionalization of an electrode surface for higher detection sensitivity. Here, nanoring electrodes embedded under the microwell traps were fabricated to achieve the isolation of the electrode surface and the cell support, and thus, the electrode surface can be modified to obtain enhanced electrochemical sensitivity for single cell analysis. Moreover, the nanometer-sized electrode permitted a faster diffusion of analyte to the surface for additional improvement in the sensitivity, which was evidenced by the electrochemical characterization and the simulation. To demonstrate the concept of the functionalized nanoring electrode for single cell analysis, the electrode surface was deposited with prussian blue to detect intracellular hydrogen peroxide at a single cell. Hundreds of picoamperes were observed on our functionalized nanoring electrode exhibiting the enhanced electrochemical sensitivity. The success in the achievement of a functionalized nanoring electrode will benefit the development of high throughput single cell electrochemical analysis.

Biological motors are highly complex protein assemblies that generate linear or rotary motion, powered by chemical energy. Synthetic motors based on DNA nanostructures, bio-hybrid designs or synthetic organic chemistry have been assembled. However, unidirectionally rotating biomimetic wheel motors with rotor–stator units that consume chemical energy are elusive. Here, we report a bio-hybrid nanoengine consisting of a catalytic stator that unidirectionally rotates an interlocked DNA wheel, powered by NTP hydrolysis. The engine consists of an engineered T7 RNA polymerase (T7RNAP-ZIF) attached to a dsDNA nanoring that is catenated to a rigid rotating dsDNA wheel. The wheel motor produces long, repetitive RNA transcripts that remain attached to the engine and are used to guide its movement along predefined ssDNA tracks arranged on a DNA nanotube. The simplicity of the design renders this walking nanoengine adaptable to other biological nanoarchitectures, facilitating the construction of complex bio-hybrid structures that achieve NTP-driven locomotion. The DNA nanoengine constitutes a chemical energy-driven unidirectional rotor that directionally walks along a predefined multistep track.

Highly dispersed Fe3+-doped layered double hydroxide (LDH-Fe) nanorings were obtained by a simple coprecipitation-acid etching approach. The morphology, structure, magnetic resonance imaging (MRI) performance in vitro, drug loading and releasing, Fe3+ leakage, and cytotoxicity of the as-prepared LDH-Fe nanorings were characterized. The LDH-Fe nanorings showed good water dispersity and a well-crystallized structure. The DLS average size of nanoparticles was measured to be 94.5 nm. Moreover, the MRI tests showed a favourable T1-weighted MRI performance of the LDH-Fe nanoring with r1 values of 0.54 and 1.68, and low r2/r1 ratios of 10.1 and 6.3, pre- and after calcination, respectively. The nanoparticles also showed high model drug (ibuprofen) loading capacities, low Fe3+ leakage, and negligible cytotoxicity. All these results demonstrate the potential of LDH-Fe nanorings as an imageable drug delivery system.

The role of quantum coherence in photochemical functions of molecular systems such as photosynthetic complexes is a broadly debated topic. Coexistence and intermixing of electronic and vibrational coherences has been proposed to be responsible for the observed long-lived coherences and high energy transfer efficiency. However, clear experimental evidence of coherences with different origins operating at the same time has been elusive. In this work, multidimensional spectra obtained from a six-porphyrin nanoring system are analyzed in detail with support from theoretical modeling. We uncover a great diversity of separable electronic, vibrational, and mixed coherences and show their cooperation in shaping the spectroscopic response. The results permit direct assignment of electronic and vibronic states and characterization of the excitation dynamics. The clear disentanglement of coherences in molecules with extended π-conjugation opens up new avenues for exploring coherent phenomena and understanding their importance for the function of complex systems.

Numerous otherwise difficult applications have been realized with materials, the chemical/physical properties of which can be controlled by external stimuli such as heat, pressure, photo-irradiation, and voltage bias. However, the complexity of design and the lack of easy-to-conduct synthetic methods make the creation of on-demand stimuli responsive materials a formidable task. Here we report an electric-stimuli-responsive multifunctional material, [10]CPP-I: crystalline assembly of a hydrocarbon nanoring ([10]cycloparaphenylene: [10]CPP) as an "electro-responsive porous host" and iodine as a "potentially functional molecule". Through applying electric stimulus, [10]CPP-I turned to exhibit two attractive properties: electronic conductivity and white light emission. We revealed that electric stimuli trigger the cascade formation of polyiodide chains inside the [10]CPP assembly through charge transfer, leading to the emergence of these properties. This "responsive porous host" approach is expected to be applicable for different stimuli, and opens the path for devising a generic strategy to the development of stimuli-responsive materials.