Articles in 2013

A novel heterojunction structure combining three kinds of semiconductors was designed and fabricated. The heterojunction structure can be used as a two-input OR gate with the combination of two diodes on the two interfaces of the organic/inorganic semiconductor. The research will have great influence in both the fundamental research field of nanoscience and the device application field of nanotechnology.

The work functions of indium tin oxide terminated with Cl and F have been studied using DFT calculations. The results show that the work function of Cl-terminated ITO is much higher than that of F-terminated ITO despite the fact that F is more electronegative than Cl. Detailed analysis through visualization of the atomic-scale charge transfer at these adatom–oxide interfaces reveals that both high electronegativity and atomic size are crucial to increase the work function of ITO.

In this article, we propose several kinds of simple nano-structures constructed by BP and SiC nanoribbons, which show peculiar electronic properties and might have promising applications in nano-electronics. SiC-BP-SiC nanoribbons are found to exhibit not only significant field-effect characteristics but also tunable negative differential resistance. ‘Y’- and ‘Δ’-shaped SiC-BP structures show significant spin polarization at their edges. Under the transverse electric field, the non-magnetic direct bandgap zigzag BP nanoribbons can change to non-magnetic indirect bandgap semiconductors, ferrimagnetic semiconductors or half-metals depending on the field strength and direction. These findings reveal the possibility of using SiC-BP nano-structures to construct multi-functional electronics.

Over the last decade, metal oxides have proven to be important materials for organic electronics. Oxides are often used as charge-injection and charge-selective interlayers to engineer the electrical resistance at electrode/organic interfaces in organic devices. An oxide’s behavior as an interlayer depends strongly on the oxide’s electronic properties—such as its band structure and work function. The numerous degrees of freedom in an oxide’s electronic properties allow these characteristics to be easily modified. The present review outlines the use of metal oxides in organic electronics, and discusses the factors that affect the oxide’s properties that are relevant to oxide/organic interfaces.

The influence of hydrophilic additives on the underlying factors and mechanisms that govern the release of the hydrophobic drug PCTX from a blended system was investigated. The incorporation of hydrophilic PEG additives resulted in a phase-separated system with randomly distributed PCTX–PEG-rich domains in the continuous PLGA matrix. Owing to their preferential association in these domains, the enhanced release of PCTX can be controlled and modulated by varying the concentration and MW of PEG additives. The extensive porosity due to the dissolution of PCTX–PEG domains created a significant reduction in the tensile strength of these films as evaluated under constant aqueous conditions.

We have developed a simple, effective, one-step, catalyst-free chemical vapor deposition method for the synthesis of high-quality LaB₆ nanostructure nanowire arrays. Field-emission (FE) measurements at room temperature (RT) show that LaB₆ nanowire arrays possess the best FE characteristics among all one-dimensional LaB₆ nanostructures, exhibiting with a low turn-on electric field, a low threshold electric field, a high current and a good stability. Temperature-dependent FE on the nanowire arrays shows that the turn-on and threshold electric fields decreased rapidly whereas the emission current density increases significantly in the ambient temperature from RT to 723 K.

Natural systems employ energy converters in the form of chlorophores or chemical entities to transform light into a mechanical response, which allows them to open and close pores. Inspired by nature, in this work, we used metallic nanoparticles as opto-thermal energy converters to switch thermally responsive polymers incorporated into nanporous membranes to open and close fluid flow.

Along with the rapid merge and development of biotechnology and nanotechnology, various DNA nanostructure scaffolds have been designed, characterized and exploited for a range of applications. Particularly, we have seen the evolution of surface-confined DNA probes with rational design from one-dimensional to two-dimensional and then to three-dimensional, which greatly improve our ability to control the density, orientation and passivation of the surface. In this review, we aim to summarize recent progress on the improvement of probe–target recognition properties by introducing DNA nanostructure scaffolds. A range of new strategies have proven to provide significantly enhanced spatial positioning range and accessibility of the probes on surface over previously reported linear structures. We will also describe applications of DNA nanostructure scaffold-based biosensors.

A novel marine silk fiber (named aneroin) from sea anemone has been discovered, and wet-spun and electrospun silk fibers from purified recombinant aneroins have been successfully fabricated. Aneroin fibers have promising mechanical properties, suggesting that this protein has potential for use as a novel fibrous biomaterial. Its use would expand the applications of silk in the development of multifunctional and bio-inspired materials.

The gas-sensing performances of the Au NP-embedded silica nanowire can be enhanced by visible light (532 nm) illumination at room temperature, which improves not only sensing response but also recover time.

Lipid-nanostructure hybrids possess dimensions that are comparable to biological molecules as well as unique and useful physicochemical properties arising from both lipids and nanomaterials. Therefore, the hybrids allow mimicking of the assembled structure and function of subcellular membrane components and monitoring of the membrane-associated reactions in a highly sensitive and controllable manner. In this review, we present recent advances in the synthesis of various lipid-nanostructure hybrids and the use of these structures for applications in nanobiotechnology. We further describe the scientific and practical applications of lipid-nanostructure hybrids for detecting membrane-targeting molecules, interfacing nanostructures with live cells and creating membrane-mimicking platforms to investigate cell–cell communication and intracellular processes.

We report on the promising thermoelectric performance of p-type polycrystalline BiCuSeO, which is a layered oxyselenide composed of conductive (Cu₂Se₂)²⁻ layers that alternate with insulating (Bi₂O₂)²⁺ layers. Electrical transport properties can be optimized by substituting Bi³⁺ with Ca²⁺. Moreover, BiCuSeO shows very low thermal conductivity in the temperature ranges of 300 (∼0.9 W m⁻¹K⁻¹) to 923 K (∼0.45 W m⁻¹ K⁻¹). These intrinsically low thermal conductivity values may result from the weak chemical bonds of the material as well as the strong anharmonicity of the bonding arrangement. The combination of the optimized power factor and the intrinsically low thermal conductivity results in a high ZT of ∼0.9 at 923 K for Bi_0.925Ca_0.075CuSeO.

Modulating the drug release from polyester matrices independently from the material properties would be beneficial to those designing biodegradable medical implants, such as drug delivery devices, stents and screws. We propose that modulated drug release can be obtained via an additive-free mechanism in polyesters by simply controlling polymer erosion through acidic terminal functional groups. The formulations can be tuned to produce large ranges in drug release with relatively small changes in terminal acidic functional groups. For example, poly(lactic-co-glycolic acid) (PLGA) 53/47 thin films could be tuned to have 10–90% drug release at 20 days, depending on the concentration of acidic terminal groups.

We propose the simple and novel ‘aqueous route’ for realizing oxide thin-film transistors (TFTs) at low annealing temperatures <200 °C with low cost. These results provide substantial progress toward solution-processed metal-oxide TFT through naturally born unique indium complex and post annealing. They exhibit acceptable electrical performance with good large-area uniformity at low temperature. The additional vacuum annealing facilitates the condensation reaction by effective removal of byproduct water molecule and activates the In₂O₃ TFT at low temperature, even with 100 °C annealing. Also, we have demonstrated the flexible and transparent oxide TFTs on a plastic substrate with good stability to the external gate bias stress.

Nanoscale graphene oxide (NGO) has emerged as extremely attractive nanomaterials for diagnostics and therapeutics. In this work, we present a systematic study on the in vivo distribution and pulmonary toxicity of NGO for up to 3 months after exposure. Radioisotope tracing and morphological observation demonstrated that intratracheally instilled NGO was mainly retained in the lung. NGO could result in acute lung injury (ALI) and chronic pulmonary fibrosis, which raises environmental concerns about the large-scale production of graphene oxide. Nevertheless, we also noted that the NGO-induced ALI was related to oxidative stress and could effectively be relieved with dexamethasone treatment.

Poly(3-hexylthiophene) nanowires, microns in length and nanometers in diameter, are stably suspended in solution, and crystallize by adjusting solvent strength. Cocrystalization of P3HT with P3HT-covered CdSe nanorods gave hybrid nanostructures in which the p-type P3HT fibrils were flanked by the n-type CdSe nanorods. The close proximity and arrangement of the two materials provides direct, continuous pathways suitable for charge transport in photovoltaic devices.

In this review, nanoporous thin-film template was obtained from the self-assembly of block copolymer PS-PLLA, at which the PLLA block can be hydrolyzed to form the nanopatterns. Nanoporous PS thin films with well-oriented cylinder nanochannels can be used for pore-filling with various ingredients to create specific drug delivery systems and optoelectronic devices. Moreover, nanoporous ceramics with high-specific surface area and high porosity can be fabricated for optical applications using hydrolyzed gyroid-forming PS-PLLA for templated sol–gel reaction. In addition, the formation of inorganic nanoporous templates from self-assembled PS-PDMS after oxygen plasma treatment and its corresponding applications in nanolithography will be discussed.

Biological sensing with silicon nanowires has drawn much attention due to the enhanced sensitivity of these devices. However, both bottom-up and top-down fabrication techniques are thus far resistant to commercialization, mainly due to the incompatibility of the bottom-up methodology with mass production and the non-standard, top-down process complexity. We report on a specific, label-free, and real-time detection of femtomolar protein concentrations with a novel type of nanowire-based biosensor. The biosensor is based on an electrostatically formed nanowire that requires standard integrated circuit processes with relaxed fabrication requirements.

Nanostructured materials always exhibit high strength, ultra-large elasticity and unusual plastic deformation behaviors. The atomic-scale understanding of the microstructure evolution process of nanomaterials when they are subjected to external stress is crucial for understanding these ‘unusual’ phenomena and is important for designing new materials and applications. In situ transmission electron microscopy (TEM) experiments provide the possibility for direct observation of the deformation mechanisms at the atomic scale. This review presents the recent developments of techniques and scientific progress for the atomic-scale in situ TEM deformation dynamics on nanomaterials. Current limitations and future aspects are also discussed.

We demonstrate a single-domain photovoltaic switch based on lateral BiFeO₃ channels, in which such photovoltaic switching is achieved by a coherent single-domain reversal with a short electrical pulse. We then provide visual evidence for such operations with a series of spatially and spectrally resolved short circuit photocurrent images. Specifically, it reveals that the sequential photovoltaic current images directly reflect the remanent polarization states of a single-domain channel. We also verify that, in multidomain channels, the diffusive switching characteristics is determined not only by the internal polarization vector within the domain but also by oxygen vacancy migration at the domain walls.