Original Article in 2015

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.

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.

Applying in situ TEM techniques to GST-based vertical PCRAM cells, we directly observed the DC set switching process of real devices for the first time. The results show that the microstructure of crystalline GST matrix is an important structural parameter determining the local temperature distribution. In the case of highly crystallized GST matrix, the device failure occurred via two-step void formation due to the polarity-dependent electromigration.

3D Networked NiCo₂S₄ nanosheet array/carbon cloth composites are synthesized by a facile hydrothermal reaction and subsequent sulfurization process, and the rational material composition and structure design lead to their outstanding overall performance as an anode material in lithium-ion batteries.

The transparent C₃N₂H₅ClO₄ ferroelectric film on ITO coated PET substrate can be bent to 3.1 mm radius without affecting its ferroelectric properties. Furthermore, its local piezoelectric response is comparable to that of Pb(Zr_0.2Ti_0.8)O₃ film.

Nanoporous metals made by dealloying can take the form of macroscopic bodies that exhibit a uniform and highly interconnected network of nanoscale ‘ligaments’. Our study used this material as the reinforcement phase in novel interpenetrating-phase nanocomposites. Tensile tests on our cm-sized composite samples for the first time demonstrate tensile ductility in a nanoporous-metal-based material. Whereas the strength, σ, of pure nanoporous metal scales with the phase faction, ϕ, as σ ∝ ϕ^3/2, the composite has a linear scaling relation σ ∝ ϕ that favors strengthening at small solid fraction. We find this strengthening also in quantitative agreement with the data behind the well-known ‘smaller is stronger’ of metal nanostructures. Thus, our material’s design strategy exploits the high strength of individual metal nano-objects such as nanowires for making a strong and ductile material from which macroscopic things can be formed.

We fabricated compact helical antenna operating in the industry-scientific-medical radio band. With a total length of only 5.5 mm, it is about five times smaller compared with the conventional dipole antenna. The transmission and receiving signals between helical antennas and the communication between a helical antenna and a smartphone is reported. Owing to the shape and dimensions, we successfully demonstrate the possibility to address the antenna, when embedded in a tooth, as well as to implant the antenna using standard medical syringes. These demonstrations highlight the potential of helical antennas for medical applications as components of smart system implants.

Novel high-κ dielectric materials are identified by automated ab initio calculations on ~1800 oxides. The cubic BeO is found to possess an unprecedented material property of 10 eV for band gap and 275 for dielectric constant. Candidate high-κ oxides are suggested for microelectronic devices such as CPU, DRAM and flash memory.

Ultra-small Ni(OH)₂ nanoparticles with different average sizes are prepared in large scale, and the best electrochemical performance is obtained at the critical size rather than the smallest size, which provides a new insight on nanosize effect on electrode materials in energy storage.

A nanosheet structure on a glass plate can transfer naked DNA into difficult-to-transfect cells (for example, stem cells) in limited time after contact (‘transfection window’) without any vector. The transfected cells express the specific proteins a week later. The gene uptake and expression are associated with the cytoskeleton arrangement on the silica nanosheets by activating the cell-membrane integrin receptor.

A novel confinement-free synthesis of CP-HMNSFs possessing straight channels at fiber center surrounded by concentric short-pitch helical channels is discovered. The chloropropyl groups are found mainly located at central cylindrical part of the nanofibers. Helical PtCo nanowires with small and narrowly distributed radii of gyration are also fabricated, showing distinct ferromagnetic properties as compared with the straight counterparts.

The rational all-oxide TiC_1-xO_x@TiO_y-TiO₂ heterostructures with the significantly enhanced thermoelectric properties had been designed, and a high dimensionless figure of merit (ZT) value of up to 0.84 at 973 K was achieved in all-oxide TiC_0.1O_0.9@TiO_y-TiO₂ heterostructures.