Proximal High-Index Metamaterials based on a Superlattice of Gold Nanohexagons Targeting the Near-Infrared Band.

Plasmonic nanoparticles can be assembled into a superlattice, to form optical metamaterials, particularly targeting precise control of optical properties such as refractive index (RI). The superlattices exhibit enhanced near-field, given the sufficiently narrow gap between nanoparticles supporting multiple plasmonic resonance modes only realized in proximal environments. Herein, the planar superlattice of plasmonic Au nanohexagons (AuNHs) with precisely controlled geometries such as size, shape, and edge-gaps is reported.

Percolated Plasmonic Superlattices of Nanospheres with 1 nm-Level Gap as High-Index Metamaterials.

Nanophotonics relies on precise control of refractive index (RI) which can be designed with metamaterials. Plasmonic superstructures of nanoparticles (NPs) can suggest a versatile way of tuning RI. However, the plasmonic effects in the superstructures demand 1 nm-level exquisite control over the interparticle gap, which is challenging in a sub-wavelength NPs.

Unraveling the Simultaneous Enhancement of Selectivity and Durability on Single-Crystalline Gold Particles for Electrochemical CO Reduction.

Electrochemical carbon dioxide reduction is a mild and eco-friendly approach for CO mitigation and producing value-added products. For selective electrochemical CO reduction, single-crystalline Au particles (octahedron, truncated-octahedron, and sphere) are synthesized by consecutive growth and chemical etching using a polydiallyldimethylammonium chloride (polyDDA) surfactant, and are surface-functionalized. Monodisperse, single-crystalline Au nanoparticles provide an ideal platform for evaluating the Au surface as a CO reduction catalyst.

Morphologically homogeneous, pH-responsive gold nanoparticles for non-invasive imaging of HeLa cancer.

Gold nanoparticles (AuNPs) have been widely used as nanocarriers in drug delivery to improve the efficiency of chemotherapy treatment and enhance early disease detection. The advantages of AuNPs include their excellent biocompatibility, easy modification and functionalization, facile synthesis, low toxicity, and controllable particle size. This study aimed to synthesize a conjugated citraconic anhydride link between morphologically homogeneous AuNPs and doxorubicin (DOX) (DOX-AuNP).

Strong Coupling of Carbon Quantum Dots in Plasmonic Nanocavities.

Confining light in extremely small cavities is crucial in nanophotonics, central to many applications. Employing a unique nanoparticle-on-mirror plasmonic structure and using a graphene film as a spacer, we create nanoscale cavities with volumes of only a few tens of cubic nanometers. The ultracompact cavity produces extremely strong optical near-fields, which facilitate the formation of single carbon quantum dots in the cavity and simultaneously empower the strong coupling between the excitons of the formed carbon quantum dot and the localized surface plasmons.

Biophysical restriction of growth area using a monodispersed gold sphere nanobarrier prolongs the mitotic phase in HeLa cells.

Gold nanoparticles are widely exploited for biological and biotechnical applications owing to their stability, biocompatibility, and known effects on cellular behaviors. Many studies have focused on nanoparticles that are internalized into cells, but extracellular nanoparticles also can regulate cell behavior, a practice known as in-plane surface nanotopography. We demonstrated that nanobarriers composed of morphologically homogeneous gold nanospheres prolonged the mitotic (M) phase in the cervical cancer cell line HeLa without inducing apoptosis.

Understanding metal-enhanced fluorescence and structural properties in Au@Ag core-shell nanocubes.

Au@Ag core-shell structures have received particular interest due to their localized surface plasmon resonance properties and great potential as oxygen reduction reaction catalysts and building blocks for self-assembly. In this study, Au@Ag core-shell nanocubes (Au@AgNCs) were fabricated in a facile manner stepwise Ag reduction on Au nanoparticles (AuNPs). The size of the Au@AgNCs and their optical properties can be simply modulated by changing the Ag shell thickness.

Hierarchically three-dimensional (3D) nanotubular sea urchin-shaped iron oxide and its application in heavy metal removal and solar-induced photocatalytic degradation.

In this study, hierarchically three-dimensional (3D) nanotubular sea urchin-shaped iron oxide nanostructures (3D-FeO) were synthesized by a facile and rapid ultrasound irradiation method. Additives, templates, inert gas atmosphere, pH regulation, and other complicated procedures were not required. Dense 3D-FeO with a relatively large Brunauer-Emmett-Teller (BET) surface area of 129.

Highly stable mesoporous silica nanospheres embedded with FeCo/graphitic shell nanocrystals as magnetically recyclable multifunctional adsorbents for wastewater treatment.

Highly stable and magnetically separable mesoporous silica nanospheres (MSNs) embedded with 4.6 ± 0.8 nm FeCo/graphitic carbon shell nanocrystals (FeCo/GC NCs@MSNs) were synthesized by thermal decomposition of metal precursors in MSNs and subsequent methane CVD.

Assembly of "3D" plasmonic clusters by "2D" AFM nanomanipulation of highly uniform and smooth gold nanospheres.

Atomic force microscopy (AFM) nanomanipulation has been viewed as a deterministic method for the assembly of plasmonic metamolecules because it enables unprecedented engineering of clusters with exquisite control over particle number and geometry. Nevertheless, the dimensionality of plasmonic metamolecules via AFM nanomanipulation is limited to 2D, so as to restrict the design space of available artificial electromagnetisms. Here, we show that "2D" nanomanipulation of the AFM tip can be used to assemble "3D" plasmonic metamolecules in a versatile and deterministic way by dribbling highly spherical and smooth gold nanospheres (NSs) on a nanohole template rather than on a flat surface.

Shape-controlled Pt nanocubes directly grown on carbon supports and their electrocatalytic activity toward methanol oxidation.

Synthesis of shape-controlled Pt nanocrystals is substantial and important for enhancing chemical and electrochemical reactions. However, the removal of capping agents, shape-controlling chemicals, on Pt surfaces is essential prior to conducting the catalytic reactions. Here we report a facile one-pot synthesis of Pt nanocubes directly grown on carbon supports (Pt nanocubes/C) with modulating the kinetic reaction factors for shaping the nanocrystals, but without adding any capping agents for preserving the clean Pt surfaces.

Interplay Between Optical Bianisotropy and Magnetism in Plasmonic Metamolecules.

The smallness of natural molecules and atoms with respect to the wavelength of light imposes severe limits on the nature of their optical response. For example, the well-known argument of Landau and Lifshitz and its recent extensions that include chiral molecules show that the electric dipole response dominates over the magneto-electric (bianisotropic) and an even smaller magnetic dipole optical response for all natural materials. Here, we experimentally demonstrate that both these responses can be greatly enhanced in plasmonic nanoclusters.

Graphene growth from reduced graphene oxide by chemical vapour deposition: seeded growth accompanied by restoration.

Understanding the underlying mechanisms involved in graphene growth via chemical vapour deposition (CVD) is critical for precise control of the characteristics of graphene. Despite much effort, the actual processes behind graphene synthesis still remain to be elucidated in a large number of aspects. Herein, we report the evolution of graphene properties during in-plane growth of graphene from reduced graphene oxide (RGO) on copper (Cu) via methane CVD.

Deterministic assembly of metamolecules by atomic force microscope-enabled manipulation of ultra-smooth, super-spherical gold nanoparticles.

Atomic force microscope (AFM)-enabled manipulation of individual metallic nanoparticles (NPs) has proven useful for assembling diverse structural motifs of metamolecules. However, for the reliable verifications of their electric/magnetic behaviors and translations into practical applications (e.g.

Low-ppm-Level colorimetric acid detection using gold nanoparticles with electro-steric stabilization.

Electro-sterically stabilized gold suspensions were employed in a colorimetric system for the detection of strong acid in water. Using oleyamine and oleic acid as steric stabilizer in 1,2-dichlorobenzene, hydrophobic gold nanoparticles were first synthesized by a reduction reaction of gold salts and were then transferred into water with a cationic surfactant. When the hydrochlo- ric acid solution higher than critical concentration was injected, particles were quickly aggregated and precipitated, creating a clear solution from the colored suspension.

In situ probing of doping- and stress-mediated phase transitions in a single-crystalline VO₂ nanobeam by spatially resolved Raman spectroscopy.

We demonstrate an experimental in situ observation of the temperature-dependent evolution of doping- and stress-mediated structural phase transitions in an individual single-crystalline VO₂ nanobeam on a Au-coated substrate under exposure to hydrogen gas using spatially resolved Raman spectroscopy. The nucleation temperature of the rutile R structural phase in the VO₂ nanobeam upon heating under hydrogen gas was lower than that under air. The spatial structural phase evolution behavior along the length of the VO₂ nanobeam under hydrogen gas upon heating was much more inhomogeneous than that along the length of the same nanobeam under air.

Ultrasmooth, highly spherical monocrystalline gold particles for precision plasmonics.

Ultrasmooth, highly spherical monocrystalline gold particles were prepared by a cyclic process of slow growth followed by slow chemical etching, which selectively removes edges and vertices. The etching process effectively makes the surface tension isotropic, so that spheres are favored under quasi-static conditions. It is scalable up to particle sizes of 200 nm or more.

β-FeOOH nanorod bundles with highly enhanced round-trip efficiency and extremely low overpotential for lithium-air batteries.

β-FeOOH nanorod (NR) catalysts prepared by ultrasonic-irradiated chemical synthesis enabled lithium-air cells to have high round-trip efficiency and extremely low overpotential as well as an outstanding rate capability. Good catalytic activities of the β-FeOOH NR bundle could be ascribed to its crystal structure, which consists of 2 × 2 tunnels formed by edge- and corner-sharing Fe(O,OH)6 octahedra as well as to its one-dimensional morphology, which makes the configured electrode highly porous, indicating that the -OOH-based catalyst can be a good substitute for oxide-base catalysts in lithium-air batteries. The ultrasonic-irradiated chemical synthesis suggested here may be a good solution to optimize the morphology of catalyst materials for maximum catalytic activity.

Hierarchical hollow spheres of Fe2O3 @polyaniline for lithium ion battery anodes.

Hierarchical hollow spheres of Fe2 O3 @polyaniline are fabricated by template-free synthesis of iron oxides followed by a post in- and exterior construction. A combination of large surface area with porous structure, fast ion/electron transport, and mechanical integrity renders this material attractive as a lithium-ion anode, showing superior rate capability and cycling performance.

Surfactant size effect on surface-enhanced Raman scattering intensity from silver nanoparticles.

We report on the synthesis of two types of Ag nanoparticles (NPs) and the influence of adsorbed surfactant size on the NP surface for surface-enhanced Raman scattering (SERS) signals. Both particles were of similar size and morphology but were covered by surfactants of different sizes; one surfactant was sodium citrate (molecular weight: 258) and the other was sodium polyacrylate (molecular weight: 2100). For SERS measurement, 4-mecapobenzoic acid and 4-naphthalene thiol as Raman-active dyes were immobilized on the surface of each AgNP.

Synthesis and assembly of colloidal particles with sticky dimples.

The preparation of anisotropic colloidal particles by a simple yet versatile temperature-controlled swelling process is described. The resulting polymeric particles feature a surface dimple, the size and shape of which were determined by the amount of oil captured in particles and the interfacial tension between the three phases: polystyrene (PS), decane, and the suspending medium. Following the removal of free or physically adsorbed surfactant from the swollen particles, hydrophobic dimples were produced upon evaporation of the oil phase.

Controlled generation of submicron emulsion droplets via highly stable tip-streaming mode in microfluidic devices.

Submicron emulsions could be produced via the tip-streaming process in a flow-focusing microfluidic device. In this article, the stability of the liquid cone and thread for tip-streaming mode could be significantly improved by employing a three-dimensional flow-focusing device, in which the hydraulic resistance was adjusted by modulating the channel heights in the flow focusing area, orifice, downstream and dispersed phase inlet channel. The pressure range for tip-streaming mode was enlarged significantly compared with two-dimensional flow-focusing devices.

Tetraglyme-mediated synthesis of Pd nanoparticles for dehydrogenation of ammonia borane.

Palladium nanoparticles (PdNPs) were conveniently prepared in tetraglyme (TG) solution using a variety of palladium precursors. At 140 °C, TG promoted Pd(3)(OAc)(6) to produce irregular shaped PdNPs with an average size of 4 nm. When these PdNPs were re-dispersed in TG and used for the dehydrogenation of ammonia borane (AB) at 85 °C, remarkably enhanced catalytic performance was achieved to release 2.

Ultrasound-assisted synthesis of Li-rich mesoporous LiMn2O4 nanospheres for enhancing the electrochemical performance in Li-ion secondary batteries.

The hierarchically structured mesoporous LiMn(2)O(4) (LMO) nanospheres were synthesized using a template-free self-assembly process that was coupled with ultrasound (U). The ultrasound technique suggested here is very powerful for controlling an ordered nanostructure and improving crystallinity with large single-crystalline domains. Owing to the hierarchical mesoporous structure and high crystallinity, U-LMO provides an excellent rate capability and cycle stability with a capacity retention of more than 98% up to 50 cycles at a 0.