Research articles

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.

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.

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.

This paper reports a facile cyclic reduction–decomposition method for the aqueous-based synthesis of highly luminescent Ag nanoclusters (NCs) with tunable emissions. A reduction–decomposition–reduction cycle was used to modify the non-luminescent Ag NC intermediates with improved stability against subsequent etching by thiol ligands, which created a mild size-/structure-focusing (or etching) environment and produced highly luminescent Ag NCs with intense red (Ag₁₆(SG)₉) and green (Ag₉(SG)₆) emission. The highly luminescent Ag NCs also possessed superior antimicrobial properties against the multidrug-resistant bacteria Pseudomonas aeruginosa via generating a high concentration of intracellular reactive oxygen species.

Springtails, wingless arthropods, are adapted to cutaneous respiration in temporarily rain-flooded habitats by a hierarchically structured skin surface. A tunable polymer replication process was applied to dissect the contributions of different structural elements and surface chemistry to the omniphobic performance of the skin.

We report that single-layered and single-crystalline graphene flakes (GFs) with highly regular and hexagonal symmetric patterns can be grown on a liquid copper surface using a CH₄ chemical vapor deposition (CVD) method. Different morphologies of these GFs can be precisely tailored by varying the composition of inert gas/H₂ carrier gas mixture, and the GF edges can be continuously tuned over the full spectrum from negative to zero to positive curvature in a controllable way. This study provides a well-behaved two-dimensional crystal growth system mimicking snowflakes, opening rich opportunities for engineering graphene patterns and studying graphene structure/property relationships.

Multilevel nonvolatile transistor memories were fabricated with inserted electret dielectric of star-shaped poly((4-diphenylamino)benzyl methacrylate). The devices could be controllably charged and retain the digital states even when the supply voltage was removed. The multilevel data storage characteristics by applying different gate voltages suggested novel ‘write-many-read-many memory’ behaviors.

Organic field-effect transistors with a self-doped (SD) polyaniline charge-trapping energy well structure exhibit outstanding nonvolatile memory characteristics. The charges generated by the field-effect operation are effectively stored in the SD poly(o-anthranilic acid) charge-trapping energy well layer so that the present memory transistor performs excellent data writing–reading–erasing functions with highly stable data retention characteristics.

The key factor and mechanism for reported toxicity of CNTs are unclear. Here we firstly quantify the contribution of metal residues and fiber structure to the toxicity of CNTs. Significant quantities of metal can be mobilized from CNTs into surrounding fluids, depending on the properties and constituent of biological microenvironment and metal particles. Hydroxyl radicals were generated by CNT containing metal impurities and leachable metal, while several inherent biomolecules facilitate the generation of free radical. Cell viability is highly dependent on the amount of metal residues and iron in particular but not tube structure, while the negative effect of CNT was limited in a certain concentration range below 80 μg ml⁻¹.

Graphene, owing to its remarkable electronic and structural properties, has attracted considerable attention in both science and technology communities. However, a major roadblock to the realization of graphene-based field-effect transistors is the fact that large-area graphene behaves like a semimetal with zero bandgap, making it unsuitable for real applications in sensing, detecting and switching systems. Surface functionalization could result in the construction of periodic micro/nanostructures by breaking sp² bonds and forming sp³ bonds. Therefore, direct chemical grafting might provide a useful way to covalently modify graphene for tailoring its properties. Owing to the inert reactivity of its surface, however, up to date only few chemical reactions were used to modify its atomic structure. Here, we demonstrate a controllable and efficient means of mild plasma methylation to manipulate the reversible interconversion of two distinct species of graphene (one crystalline and the other methylated). The strategy of incorporating diverse functional substituents (methyl group and hydrogen atoms here) into graphene instead of a single type of chemical groups could provide a useful route for the development of different applications, such as chemical/biosensors and multifunctional electrical circuits. Moreover, the methylated graphene with fine tunability is stable at room temperature, which suggests the intrinsic potential of novel applications in graphene-based optoelectronic devices that invites further studies.

It is commonly believed that bulk SnO2 is not a suitable ultraviolet (UV) light emitter due to the dipole-forbidden nature of its band-edge states, which has hindered its potential use in optical applications. Here, we demonstrate both theoretically and experimentally an effective method to break the dipole-forbidden rule in SnO2 via nano-engineering its crystalline structure. Furthermore, we designed and fabricated a prototypical UV-light-emitting diode (LED) based on SnO2 thin films. Our methodology is transferable to other semiconductors with ‘forbidden’ energy gaps, offering a promising route toward adding new members to the family of light-emitting materials.

Peptide-mimic poly(n-hexyl isocyanate) (PHIC) with stiff chain characteristics demonstrated to selectively form a well-ordered hexagonal close packing structure with 8₃ helical conformation in the nansocale thin films annealed with carbon disulfide. Moreover, this polymer showed to selectively form a well-ordered multi-bilayer structure with β-sheet conformation in the thin films annealed with toluene. These two self-assembled structures were reversibly transformed by consecutive annealing with carbon disulfide and toluene. These chain conformations and self-assembled structures were confirmed by synchrotron grazing incidence X-ray scattering analysis.

Increasing the Seebeck coefficient has long been pursued for increasing thermoelectric efficiency, but other changes in transport properties may compensate this effect and ultimately lead to no improvement in figure of merit. The Seebeck coefficient can be enhanced by either the addition of resonant states or the involvement of multiple band conduction. This work demonstrates the beneficial effect of multiple band conduction for highefficiency thermoelectrics.

We report a microfluidic chip integrated with a bioengineered membrane for two-dimensional (2D) and three-dimensional (3D) spheroid tissue cultures to achieve deterministic patterning of cells. The cell-supporting membrane was selectively deposited with extracellular matrix molecules. Results show cell-trapping rate attains 97%. Tuning of the surface enables not only highly controlled geometry of the monolayer (2D) cell mass but also 3D culture of uniformly sized multicellular spheroids. The 3D spheroids of human ovarian epithelial cancer cells acquired mesenchymal traits—increased expressions of N-cadherin, vimentin and fibronectin—and lowered expression of epithelial marker (CD326/epithelial cell adhesion molecule) compared with that in 2D cultures, indicative of epithelial–mesenchymal transition. These results offer new opportunities to achieve active control of 2D cellular patterns and 3D multicellular spheroids on demand, and may be amenable toward study of the metastatic process in vitro.

We report the first attempt of magnetic manipulation of photoresponse in an one-dimensional device, in which a highly sensitive photodetector in the UV region composed of tin oxide nanowire and ferromagnetic nickel electrodes have been fabricated and characterized. Surprisingly, as the Nickel electrodes were magnetized, the photocurrent gain can be greatly enhanced by up to 20 times. The underlying mechanism is attributed to both oxygen molecules adsorbed and surface band bending effects due to the migration of electrons to the surface of tin oxide nanowire caused by the magnetic field of ferromagnetic electrodes.

Barcodes that composed of multiple colloidal crystal or magnetic-tagged ETPTA cores and PEG hydrogel shells were developed by using microfluidics. As the cores are with distinct reflection peaks, the barcodes allow for substantial number of coding levels for multiplexing. The hydrogel shells surrounding the barcodes enable the creation of three-dimensional scaffolds for immobilizing probes. Moreover, the presence of magnetism in the barcodes confer them controllable movement under magnetic fields, which could significantly increase the sensitivity and simplify the processing of the bioassays.

We demonstrate the growth of high-quality GaN films with flat surface and uniform morphology on large-scale polycrystalline chemical vapor-deposited graphene films. The films exhibit stimulated emission even at room temperature, a highly c-axis-oriented crystal structure, and a preferred in-plane orientation. Furthermore, the GaN films grown on the graphene films can be used for fabrication of blue and green light-emitting diodes.

We present a facile and reliable approach for the assembly of crack-free single-crystalline photonic crystals (PCs) with centimeter scale by the synergistic effects of substrate deformation and monomer infiltration/polymerization. The critical thickness of crack-free PCs is ∼5.6 μm, below which crack-free PCs can be fabricated on proper substrate. The co-assembling monomer infiltrates and polymerizes in the interstices of the colloidal spheres to form an elastic polymer network, which could lower the tensile stress generated from colloid shrinkage and strengthen the long range interactions of the colloidal spheres. Otherwise, the timely transformation of the flexible substrate releases the residual stress. This approach to centimeter-scale crack-free single-crystalline PCs will not only prompt the practical applications of PCs in high-performance optic devices, but also have great implications for the fabrication of crack-free thin films in other fields, such as wet clays, coating and ceramic industry.

Strain-driven micro- and nanorolls fabrication is generally restricted to multilayer and multiprocessing systems, which limit the possibility of exploiting the self-organization at different length scales. We have designed a hybrid organic–inorganic film whose surface shows a selective response to external stimuli, which induces mechanical strain and self-rolling in one-step–one-layer fabrication. The scrolling is initiated by water and any aqueous solution that also contains molecules or colloidal particles. During scrolling, the different species in solution remain entrapped in the rolls, giving rise to functional microrolls.

High-power applications at fast charge and discharge rates are still great challenges in the development of rechargeable lithium batteries. Here, we demonstrate that ultralong LiV₃O₈ nanowire cathode materials synthesized by topotactic Li intercalation present excellent high-rate and long-life performance. At the current density of 2000, mA g⁻¹, the initial and the six-hundredth discharge capacities can reach 137 and 120 mAh g⁻¹, respectively, corresponding to a capacity fading of only 0.022% per cycle. Such performance indicates that the topotactically synthesized ultralong LiV₃O₈ nanowires are promising cathode materials for high-rate and long-life rechargeable lithium batteries.