Articles in 2015

A large number of multilayered stacking faults are detected along {111} planes during aging (arrows in a) of present superalloy. Every γ′ phase particle is isolated by multilayered stacking-fault ribbons and grows slightly. The coarsening rate of the γ′ phase decreases significantly after plastic deformation, implying that the formation of multilayered stacking-fault ribbons as a consequence of Suzuki segregation can obviously retard the coarsening of γ′ phase in this novel alloy.

We at the first time demonstrate that the Ni/Mn disordering in LNMO spinel is decoupled from the presence of Mn³⁺ ions by doping Li and strongly affects phase transformation resulting in the increase of solid-solution phase transformation. The resulting material with 1–2 μm achieves superior rate capability, 120 mAh g⁻¹ at ~38 C and 60 mAh g⁻¹ at 60 C.

Enhanced thermoelectric figure of merit in the fully densified Cu₂Te bulk materials by direct annealing method.

We prepared a hybrid hydrogel system by doping the gold nanorods (GNRs) into the thermal responsive hydrogel. The near-infrared (NIR) laser was used to trigger the release of loaded Doxorubicin (DOX) by utilizing the photothermal effect of GNRs to induce the contraction of thermo-responsive hydrogels. The development of the hydrogel as the carrier is for the chemo-photothermal co-therapy of local breast cancer recurrence. The DOX-PCNA-GNRs hydrogel effectively prevented breast cancer recurrence after primary tumor resection in a mouse model.

Development of methylammonium lead halide perovskites for efficient solar cell is best approach towards efficient building photovoltaic. This article demonstrates the synthetic strategy for the synthesis of efficient and stable CH₃NH₃PbBr₃ quantum dots for efficient mesoscopic solid-state perovskite solar cells. The influence of different CH₃NH₃PbBr₃ quantum dot size and different hole-transporting materials has been discussed systematically.

Formation of nanoparticles have shown significant improvement in quality of size, shape and dispersity based on recent advanced biosynthesis approaches by understanding the natural mechanisms underlying nanoparticles synthesis. Considering the biocompatibility, cost effectiveness and eco-friendliness, bio-associated synthesis of nanoparticles may provide the promising solutions to the challenge faced in the applications of industry and biomedicine.

We report the catalyst-free growth of InAs/In_xGa_1−xAs coaxial nanorod heterostructures on large-area graphene layers using molecular beam epitaxy and our investigation of the chemical composition and crystal structure of these heterostructures using electron microscopy. Cross-sectional electron microscopy images showed that In_xGa_1−xAs layers, having uniform composition, coated heteroepitaxially the entire surface of the InAs nanorods, without interfacial layers or structural defects. The catalyst-free growth mechanism of InAs nanorods on graphene was investigated using in situ reflection high-energy electron diffraction.

The as-prepared multifunctional upconversion–nanoparticles–trismethylpyridylporphyrin–fullerene nanocomposite (UCNP–PEG–FA/PC₇₀) nanocomposite not only could utilize UCNPs to convert NIR light to ultraviolet–visible one to activate PC₇₀ producing ¹O₂ for killing cancer cells under low-oxygen conditions, but also could act as a theranostic agent for trimodal fluorescence/upconversion luminescence/magnetic resonance imaging-guided photodynamic therapy (PDT). The synthesized UCNP–PEG–FA/PC₇₀ would pave the way of efficient PDT, namely, limited penetration depth and oxygen-deficient microenvironment, which hinder the efficiency of PDT.

A general method for assembling patterned interfaces of uniform, flexible mesoporous iron oxide nanopyramid islands is presented. The 3D porous interfaces possess a unique mesostructure that features a large surface area, a large pore size and excellent flexibility. Furthermore, the 3D porous Au–NPI interfaces allow efficient immobilization of cytochrome c and a significant enhancement of localized surface plasmon resonance. More importantly, the ultrasensitive integrated interfaces demonstrate over 1000-fold enhancement of the photocurrent variation on the 3D mesostructures based on the switchable direct electrochemistry cytochrome c. The strategy of interfacial assembly offers new possibilities for the chemical design of patterned mesoporous semiconductors with high flexibility and tailored photocatalytic characteristics.

Wu et al.¹ demonstrated a two-dimensional (2D) material-based laser that required only 1 W cm⁻² of pump power to reach the threshold limit. This value is low enough to be optically driven by a regular household light bulb! Reducing the power level for the onset of lasing action is a desirable goal in laser science. A series of design choices led to this breakthrough: (1) the 2D gain material exhibited high conversion efficiencies; and (2) the laser cavity—a photonic crystal cavity (PCC)—had a high quality factor (Figure 1).

Regenerative underwater superhydrophobicity was achieved in hierarchical ZnO/Si surfaces via hydrogen gas from photoelectrochemical reaction and unique surface structures for capturing and retaining a stable gas layer. Furthermore, we developed a model to determine the optimum structural factors of hierarchical ZnO/Si for complete regeneration of superhydrophobicity.

Confining quantum dots (QDs) into one-dimensional polymer nanostructures, we develop an inter-dot spacing control technique by which we can effectively isolate QDs in the solid-state film. The resultant isolated QDs in this nanostructure have clear monomeric features caused by attenuation of several problematic interactions, such as self-quenching. By incorporating isolated QD as an auxiliary light harvester, we can improve the performance of light-harvesting devices due to its additional absorption and efficient energy transfer. This study provides a general strategy that could be potentially useful for the spatial control of other functional moieties in various devices.

We made ‘Gd-peapod’, which is a double-walled carbon nanotube filled with gadolinium chloride. After Gd-peapods were injected to a rat via tail vein, we evaluated the organs by magnetic resonance imaging (MRI). As a result, the peapods in rats were easily visualized by MRI and the change in signal intensity was dose dependent. This newly developed method can be used to monitor carbon nanotube biokinetics in vivo without tedious tissue preparation.

Inspired by the intrinsic morphology of smooth muscle cells (SMCs), a micropatterned hydrogel is developed to direct and define the boundary conditions for efficient SMC differentiation of human mesenchymal stem cells (hMSCs). The results show that in conjunction with TGF-β1 treatment, muscle-mimicking shapes with intermediate aspect ratios ranging from 5:1 to 10:1 exert the strongest pro-SMC differentiation effects in a structural–contractile force-dependent manner. These findings are expected to provide critical insights and design rules for vascular-related engineered tissue grafts.

Reversible electric-field-driven magnetization switching between perpendicular-to-plane and in-plane orientations in Cu/Ni multilayers on ferroelectric BaTiO₃ is demonstrated at room temperature. Fully deterministic magnetic switching is based on efficient strain transfer from ferroelastic domains in BaTiO₃ and the high sensitivity of perpendicular magnetic anisotropy in Cu/Ni to electric-field-induced strain modulations. The magnetoelectric coupling effect can also be used to realize 180° magnetization reversal if the out-of-plane symmetry of magnetic anisotropy is temporarily broken by a small magnetic field.

A series of new poly(glycidyl methacrylate)-based supramolecular polycations with Gd³⁺ chelation were designed for low-toxicity and high-efficiency multifunctional gene delivery systems.

The interplay between hybridization, orbital occupancy and spin that governs the macroscopic transport and magnetic properties of ultra-thin manganites is revealed using a combination of spectroscopic ellipsometry, X-ray absorption, X-ray magnetic circular dichroism and transport measurements.

Silicene is the silicon counterpart of graphene, that is, it consists of a single layer of Si atoms arranged in a hexagonal network. This new two-dimensional material, first predicted by theory, has been recently grown on different metallic surfaces.^{1, 2, 3} An obvious advantage of silicene (over graphene) for nanoelectronic applications is its better compatibility and expected integration with the existing Si nanotechnology platform. A new breakthrough on this material has been recently reported by Tao et al.,⁴ who have successfully fabricated the first silicene-based field effect transistors (FETs) operating at room temperature. Their success relies on the development of a layer transfer process, called ‘silicene-encapsulated delamination with native electrodes’ (SEDNE). This innovative process includes the following key steps: (1) epitaxial growth of silicene on Ag(111) thin films grown on mica substrates; (2) Al₂O₃ in situ encapsulation of the silicene layer, followed by its delamination transfer on a p⁺⁺Si/SiO₂ substrate; and (3) subsequent Ag source/drain contact formation by e-beam lithography. A resulting silicene-based FET, with the p⁺⁺Si substrate used as a back-gate contact, is shown in Figure 1a.

This review highlights the recent developments and contributions of advanced electron microscopy studies to the research of lithium-ion battery materials. Both static, ex situ studies and newly developed in situ AEM techniques are emphasized, and future directions are also proposed.