Superlattice nanowires and nanoribbons are categorized as axial superlattice nanowires and lateral superlattice and planar superlattice nanoribbons according to their superlattice stacking directions. We analyze the dependence of X-ray diffraction (XRD) and select-area electron diffraction results on the different diffraction configurations of these superlattice structures. By use of the analysis, we have identified the formation of planar superlattice structures in In-doped ZnO nanoribbons by XRD and cross section transmission electron microscopy investigations. The In-doped ZnO superlattice nanoribbons are formed by alternately stacking layers of In/Zn−O and In−O along ZnO (001) direction, resulting in a nanoribbon with (001) polar surface as its wide surface.

We investigated the depth dependence of coherence times of nitrogen-vacancy (NV) centers through precise depth control using oxidative etching at 580 °C in air. By successive nanoscale etching, NV centers could be brought close to the diamond surface step by step, which enabled us to track the evolution of the number of NV centers remaining in the chip and to study the depth dependence of coherence times of NV centers with diamond etching. Our results showed that the coherence times of NV centers declined rapidly with the depth reduction in the last about 22 nm before they finally disappeared, which revealed a critical depth for the influence of a rapid fluctuating surface spin bath. Moreover, by using the slow etching method combined with low-energy nitrogen implantation, NV centers with depths shallower than the initially implanted depths can be generated, which are preferred for detecting external spins with higher sensitivity.

We present a facile, environment-friendly and mild method to fabricate graphene hydrogel by heating graphene oxide (GO) suspension containing sodium bicarbonate (NaHCO3). This method demonstrates a new type of in situ reduction-assembly approach to construct graphene hydrogel through simultaneous water evaporation and GO reduction. The freeze-dried graphene aerogel (G-Gel) shows excellent adsorptivity to heavy metal ions and dyes. The thermally treated G-Gel (TG-Gel) exhibits promising performance in recyclable selective absorption of oils and organic solvents.

In this paper, we present electron diffraction and high-resolution transmission electron microscopy (HRTEM) evidence that graphene can be laterally homoepitaxially grown from homo-seeds. We demonstrate that exfoliated thin graphite flakes and CVD-grown graphene grains can both serve as seed crystals. Raman spectra indicate that the epitaxial graphene is 1–2 layers thick, regardless of seed thickness. A two-step growth procedure is developed to epitaxially synthesize large graphene grains. Lateral homoepitaxial growth makes it a reality to duplicate the structure and increase the size of small high-quality graphene crystals.

•Pt/3D-G/FTO was prepared by a facile, convenient, inexpensive and green method.•Pt/3D-G/FTO exhibits much enhanced catalytic activity and better stability for MOR.•3D graphene possesses high surface area, large void volume and high conductivity.•The catalytic ability of Pt/3D-G/FTO raised with the deposition potential.•Pt/3D-G/FTO prepared by CV deposition shows the largest methanol oxidation ability.We report a facile, low-cost and green route to fabricate platinum nanoparticle (Pt NP) decorated three-dimensional (3D) graphene assembled on fluorine-doped tin oxide (FTO) electrodes (Pt/3D-G/FTO) with enhanced electrocatalytic activity. The fabrication process was accomplished by preparation of 3D graphene (3D-G/FTO) electrodes through electrochemical reduction of a graphene oxide suspension followed by electrodeposition of Pt NPs onto them. The Pt/3D-G/FTO electrode exhibits much higher catalytic activity and better stability for methanol oxidation compared with the electrodes prepared by electrodeposition of Pt NPs onto two-dimensional graphene sheets substrate (Pt/G/FTO) or bare FTO (Pt/FTO) under the same condition. These enhancements can be attributed to the high surface area, large void volume and high electrical conductivity as well as smaller size of Pt NPs in the hollows of the 3D architecture and a large amount of ridges on it.

Concave palladium nanocrystals are attractive for their superior catalytic ability arising from high densities of atomic steps and kinks. However, it is still a challenge to generate the concave surface, which is not favored by thermodynamics owing to its higher surface energy. In this study, concave palladium nanocubes have been synthesized kinetically in high yield via a facile one-step wet chemical method using sodium ascorbate (NaA) as the reductant in an aqueous solution. This process allows independent control of the average edge length and the surface curvature of the nanocubes, respectively. The particle morphology can be tuned by changing the reducing rate during the reaction. Right bipyramids and 5-fold twinned nanorods with concave surfaces have also been synthesized with two reductants at the different stages or an appropriate amount of ascorbic acid only. Remarkable enhancements in both electrocatalytic activity and stability are observed on concave Pd nanocubes and twinned nanocrystals over conventional Pd nanocrystals with flat surfaces and commercial Pd/C.

Submillimeter single-crystal monolayer and multilayer graphene domains were prepared by an atmospheric pressure chemical vapor deposition method with suppressing nucleation on copper foils through an annealing procedure. A facile oxidation visualization method was applied to study the nucleation density and morphology of graphene domains on copper foils. Scanning electron microscopy, transmission electron microscopy, atomic force microscopy, polarized optical microscopy, and Raman spectra showed that the submillimeter graphene domains were monolayer single crystals.

We report the morphology control of one-dimensional (1D) SnO2 nanostructures by Ga catalysts using thermal evaporation method. Gallium (Ga), either from decomposition of GaN powder or from Ga metal, is adopted as a catalyst for the growth of long SnO2 nanowires and nanobelts. At similar experimental conditions, quantities of nanobelts are formed instead of nanowires when the temperature and reaction time are increased. Such approach enables us to synthesize various morphologies of SnO2 nanobelts with different side facets. Novel nanobelts with [0 0 1] growth direction with high energy side facets are obtained for the first time, which is attributed to the large amount of oxygen vacancies introduced in the nanobelts by the Ga catalysts.Graphical abstractMorphology control of one-dimensional SnO2 nanostructures are realized via a thermal evaporation method. Novel nanobelts along [0 0 1] direction having high energy side facets were fabricated for the first time.Highlights► Morphology control of one-dimensional SnO2 nanostructures are realized by Ga catalysts using thermal evaporation method. ► Oxygen vacancies influenced the growth directions in order to neutralize thermodynamic instability. ► Novel nanobelts with [0 0 1] growth direction with high energy side facets are obtained for the first time.

CdS nanoparticle-sensitized TiO2 (CdS-TiO2) nanotube arrays are synthesized with a facile one-step electrodeposition technique. In these composited nanostructures, CdS nanoparticles uniformly distribute in the TiO2 nanotubes and partially embed in the shell of TiO2 nanotubes. These structures effectively prevent CdS nanoparticles assembling or clogging the nanotubes and improve the contact area between CdS nanoparticles and the TiO2 shells. Furthermore, the size and distribution density of CdS nanoparticles can be tuned easily by controlling the concentration of electrolyte. Coupling TiO2 nanotubes with CdS nanoparticles extends the optical absorption from ultraviolet into the visible-light region up to 580 nm. An 11-fold enhancement in photoelectrochemical (PEC) activity is observed for CdS-TiO2 nanotube arrays compared with plain TiO2 nanotube arrays. This unique method is also suitable for the synthesis of other narrow band gap semiconductor-sensitized TiO2 nanotubes.

In this paper, we report a one-step, high-yield synthesis of one-dimensional Ag heteronanostructures in aqueous solution. Besides the usual fcc phase of Ag, the heteronanostructures also contain a rare hcp (4H polytypic) phase, which favors asymmetrical growth. The rod−needle heteronanostructures (RNHSs) and plate−belt heteronanostructures (PBHSs) are formed through two different mechanisms. For RNHSs, the 4H and fcc phases coexist but have different densities in different segments, while for PBHSs, the fcc and 4H crystal structures exist in plate and belt segments, respectively. Condition-sensitive coexisting phase preferences can be applied as a new way of controlling the shape and thus the properties of Ag nanostructures.

Nanobubbles with ultrathin single crystal shells, a new kind of closed nanostructure, have been synthesized from a nonlayered indium oxidesemiconductor.

Arrays of Ni nanoparticle chains embedded in TiO2 nanotubes (TiO2/Ni) were fabricated by one-step electrodeposition in anodic aluminum oxide membranes. The formation of spacing Ni nanoparticles or continuous nanorods in the TiO2 nanotubes depends on the deposition potential, the potential waveform, and the pH value in the electrolyte. The growth mechanism is attributed to the generation of H2 bubbles and their periodical evolution outside of the TiO2 nanotubes.

This paper reports a high-yield synthesis of Ag nanospheres made up of primary nanoparticles. The size of the silver nanospheres can be controlled by changing the concentration of poly(vinylpyrrolidone) (PVP) which acts as a stabilizer. In addition, the surface morphology of the nanospheres can be well controlled through controlling the shape of primary Ag nanoparticles by introducing a small quantity of ionic capping agents in the solution. Different surface morphologies of Ag nanospheres lead to different surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) properties. The SERS property of the nanospheres used as substrates is very sensitive to the nanoscale characteristics of the surfaces, and the nanospheres with sharp tips on their surface exhibit much better Raman scattering enhancement than non-agglomerated spherical Ag nanoparticles.

We report a method to prepare nanocube-based super-crystals, which not only have a well-defined structure but also have a well-defined shape and size.

Zn-doped gallium nitride (GaN) nanotubes with zigzag morphology have been synthesized by a chemical vapor deposition method. A single-crystalline zigzag nanotube consists of two building blocks with equivalent growth directions, hexagonal cross sections, and about 10 nm wall thicknesses. The formation of the nanotube is attributed to the reduction of electrostatic interaction energy caused by the polar side surfaces of GaN. A room temperature photoluminescence spectrum of Zn-doped GaN nanotubes with zigzag morphology shows two peaks at 2.97 and 2.16 eV, respectively.

InGaO3(ZnO)m (m = 3, 5) nanowires with perfect superlattice structures were synthesized via a catalyst-assisted vapor−liquid−solid (VLS) growth mechanism. Different from In2O3(ZnO)m nanowires maintaining wurtzite structure, the InGaO3(ZnO)m (m = 3, 5) superlattice nanowires have a monoclinic crystal structure. High resolution transmission electron microscopy (HRTEM) indicates that the nanowires have an axial superlattice structure, which consists of an In−O layer and In, Ga/Zn−O layers stacking alternately along the nanowire length. The period of a InGaO3(ZnO)3 nanowire consists of four atom layers, which is the shortest period in quasi-one-dimensional superlattice structures.

Synthesis of Ni/TiO2 core/shell nanorod arrays is carried out using a one-step electrodeposition technique. The TiO2 shell and Ni core are synthesized at the same time. Furthermore, this approach makes the Ni core directly connect with the Ni substrate without a barrier layer, which would benefit electron transport from the Ni core to the substrate. The TiO2 shell thickness can be tuned from about 20 to 90 nm by changing the concentration of TiF4, and the length of the Ni/TiO2 core/shell nanorods can be tuned from about 2 to 60 μm by changing the deposition potential or time. The Ni/TiO2 core/shell nanorods are characterized by scanning electron microscopy and transmission electron microscopy. Energy dispersive spectroscopy and selected area electron diffraction are used to determine the chemical composition and crystal structure of the Ni/TiO2 core/shell nanorods. The present approach can be used for synthesizing variable metal/TiO2 core/shell nanostructure.

Ordered sub-10 nm cuprous oxide nanowires were synthesized by electrodeposition in anodic aluminum oxide (AAO) membranes assisted with poly(vinyl pyrrolidone) (PVP) as soft templates. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy demonstrate that a nanowire has a core of Cu2O and a thin shell of CuO. The formation of ultrathin nanowires is attributed to the arrangement of the PVP in the channels of AAO membranes under an electric field. The diameter and the length of the nanowires depend on the applied potential in the elctrodeposition. UV−vis absorption spectroscopy shows the quantum confinement effect of the Cu2O nanowires.

We demonstrate a preferential nucleation, epitaxial growth, and self-attraction of crystal orientation-ordered ZnO nanorod bundles on (0001) plane of single-crystal ZnO microcones.

Ordered ZnO nanowire arrays were fabricated by cathodic electrodeposition based on anodic alumina membrane from a non-aqueous dimethyl sulfoxide solution containing zinc chloride and a molecular oxygen precursor. Their microstructures were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The results indicate that the ZnO nanowires with wurtzite polycrystalline structure are uniformly embedded into the hexagonally ordered nanopores of anodic alumina membrane. A sharp ultraviolet emission at 383 nm and visible broad emission bands around 592 nm are observed from ZnO nanowire arrays.

(001)-oriented ZnO films on Zn substrates were synthesized by cathodic electrodeposition from an aqueous solution composed only of 0.05 M zinc nitrate at 65 °C. A bound exciton emission band around 3.34 eV along with three longitudinal optical (LO) phonon replicas and an intensive broad emission band around 2.17 eV were observed from the photoluminescence (PL) spectra of ZnO films prepared at more positive potential (− 0.6∼− 0.8 V). When more negative potential (− 1.0∼− 1.4 V) was applied, the ultraviolet emission band disappeared. These results indicate that more positive electrodeposition potential favors the high quality ZnO film growth. The PL spectra of the annealed ZnO films prepared at more positive electrodeposition potentials − 0.6∼− 1.0 V exhibit the ultraviolet emission at 3.35 eV and a negligibly weak emission from defects. Annealing resulted in the enhancement and sharpening of the excitonic emission band and decrease of the deep level emission. The bandgap (Eg) of the ZnO film prepared at − 1.0 V on indium tin oxide (ITO) substrate decreased from 3.56 to 3.29 eV due to the removing of Zn(OH)2 from the film after annealing.

In-doped ZnO nanobelts were fabricated by thermal evaporation with assistance of gold catalyst. The nanobelts have high crystal quality and grow along direction with (0 0 0 1) dominated surface, and have an average In:Zn value of 1:30. A growth mechanism based on VLS is proposed to understand the nanobelts growth, explaining Au particles are only found at the ends of short narrow part of the nanobelts that are mostly uniform broad flat. The ZnO UV emission peak redshifting about 200 meV after doping gives an estimate of the carrier density in the doped ZnO nanobelts can be as high as 7 × 1019 cm−3.

Raman micro-spectroscopy using exciting light with an approximately 2-μm diameter exciting spot was undertaken to investigate the micro-structure of cross-section of a 100-μm thick diamond film prepared by hot-filament chemical vapor deposition (HFCVD). The Raman spectra exhibited different features with changing position, suggesting that the composition of crystalline diamond, amorphous carbon and graphitic phases varied in the HFCVD process. The presence of a broad band and high background intensity in the spectra near the substrate surface was attributed to the amorphous carbon synthesized in the nucleation process of the film. A decreasing proportion of sp2-bond structure in the amorphous carbon phase with increasing film thickness was believed to account for the decline in the intensity of the 1200–1600-cm−1 band. The different composition of the diamond grains and of the grain boundaries in the film was shown in the Raman spectra obtained from different positions at the same cross-sectional thickness by scanning the exciting light parallel to the surface of the film.

This paper reports a high-yield synthesis of Ag nanospheres made up of primary nanoparticles. The size of the silver nanospheres can be controlled by changing the concentration of poly(vinylpyrrolidone) (PVP) which acts as a stabilizer. In addition, the surface morphology of the nanospheres can be well controlled through controlling the shape of primary Ag nanoparticles by introducing a small quantity of ionic capping agents in the solution. Different surface morphologies of Ag nanospheres lead to different surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) properties. The SERS property of the nanospheres used as substrates is very sensitive to the nanoscale characteristics of the surfaces, and the nanospheres with sharp tips on their surface exhibit much better Raman scattering enhancement than non-agglomerated spherical Ag nanoparticles.

We present a facile, environment-friendly and mild method to fabricate graphene hydrogel by heating graphene oxide (GO) suspension containing sodium bicarbonate (NaHCO3). This method demonstrates a new type of in situ reduction-assembly approach to construct graphene hydrogel through simultaneous water evaporation and GO reduction. The freeze-dried graphene aerogel (G-Gel) shows excellent adsorptivity to heavy metal ions and dyes. The thermally treated G-Gel (TG-Gel) exhibits promising performance in recyclable selective absorption of oils and organic solvents.