Zinc oxide nanowire rigid platforms on elastomeric substrates.

Zinc oxide nanostructured thin films are transparent semiconducting ceramics increasingly used in a wide range of integrated devices. This paper outlines a simple strategy to integrate arrays of zinc oxide nanostructured thin films on elastomeric substrates using templated patterning. The arrays are robust to large uniaxial strains (up to 20% strain), do not fracture, and maintain electrical functionality. The integration of brittle nanostructured semiconducting materials on elastomeric substrates opens promising routes for the manufacture of deformable and stretchable electronics.

Encapsulated inorganic nanostructures: a route to sizable modulated, noncovalent, on-tube potentials in carbon nanotubes.

The large variety of hybrid carbon nanotube systems synthesized to date (e.g., by encapsulation, wrapping, or stacking) has provided a body of interactions with which to modify the host nanotubes to produce new functionalities and control their behavior. Each, however, has limitations: hybridization can strongly degrade desirable nanotube properties; noncovalent interactions with molecular systems are generally weak; and interlayer interactions in layered nanotubes are strongly dependent upon the precise stacking sequence. Here we show that the electrostatic/polarization interaction provides a generic route to designing unprecedented, sizable and highly modulated (1 eV range), noncovalent on-tube potentials via encapsulation of inorganic partially ionic phases where charge anisotropy is maximized. Focusing on silver iodide (AgI) nanowires inside single-walled carbon nanotubes, we exploit the polymorphism of AgI, which creates a variety of different charge distributions and, consequently, interactions of varying strength and symmetry. Combined ab initio calculations, high-resolution transmission electron microscopy, and scanning tunneling microscopy and spectroscopy are used to demonstrate symmetry breaking of the nanotube wave functions and novel electronic superstructure formation, which we then correlate with the modulated, noncovalent electrostatic/polarization potentials from the AgI filling. These on-tube potentials are markedly stronger than those due to other noncovalent interactions known in carbon nanotube systems and lead to significant redistribution of the wave function around the nanotube, with implications for conceptually new single-nanotube electronic devices and molecular assembly. Principles derived can translate more broadly to relating graphene systems, for designing/controlling potentials and superstructures.

Novel nonvolatile memory with multibit storage based on a ZnO nanowire transistor.

We demonstrate a room temperature processed ferroelectric (FE) nonvolatile memory based on a ZnO nanowire (NW) FET where the NW channel is coated with FE nanoparticles. A single device exhibits excellent memory characteristics with the large modulation in channel conductance between ON and OFF states exceeding 10(4), a long retention time of over 4 × 10(4) s, and multibit memory storage ability. Our findings provide a viable way to create new functional high-density nonvolatile memory devices compatible with simple processing techniques at low temperature for flexible devices made on plastic substrates.

Cs corrected STEM EELS: Analysing beam sensitive carbon nanomaterials in cellular structures.

Identification of individual single wall nanotubes (SWNTs) within a cellular structure can provide vital information towards understanding the potential mechanisms of uptake, their localisation and whether their structure is transformed within a cell. To be able to image an individual SWNT in such an environment a resolution is required that is not usually appropriate for biological sections. Standard transmission electron microscopy (TEM) techniques such as bright field imaging of these cellular structures result in very weak contrast. Traditionally, researchers have stained the cells with heavy metal stains to enhance the cellular structure, however this can lead to confusion when analysing the samples at high resolution. Subsequently, alternative methods have been investigated to allow high resolution imaging and spectroscopy to identify SWNTs within the cell; here we will concentrate on the sample preparation and experimental methods used to achieve such resolution.

Uptake of noncytotoxic acid-treated single-walled carbon nanotubes into the cytoplasm of human macrophage cells.

Water-soluble single-walled nanotubes (SWNTs) are being tested as contrast agents for medical imaging and for the delivery of therapeutically active molecules to target cells. However, before they become used commercially, it will be essential to establish their subcellular distribution and whether they are cytotoxic. Here we characterize uptake of unlabeled, acid-treated, water-soluble SWNTs by human monocyte derived macrophage cells using a combination of Raman spectroscopy and analytical electron microscopy and compare our findings to previous work on unpurified SWNTs. Raman spectroscopy demonstrated that acid-treated SWNTs had a greater number of functional groups on the carbon walls than nontreated SWNT. The acid-treated SWNTs were less aggregated within cells than unpurified SWNTs. Bundles, and also individual acid-treated SWNTs, were found frequently inside lysosomes and also the cytoplasm, where they caused no significant changes in cell viability or structure even after 4 days of exposure.

Carbon nanotube array: a new MIP platform.

Here we demonstrate that a free-standing carbon nanotube (CNT) array can be used as a large surface area and high porosity 3D platform for molecular imprinted polymer (MIP), especially for surface imprinting. The thickness of polymer grafted around each CNT can be fine-tuned to imprint different sizes of target molecules, and yet it can be thin enough to expose every imprint site to the target molecules in solution without sacrificing the capacity of binding sites. The performance of this new CNT-MIP architecture was first assessed with a caffeine-imprinted polypyrrole (PPy) coating on two types of CNT arrays: sparse and dense CNTs. Real-time pulsed amperometric detection was used to study the rebinding of the caffeine molecules onto these CNT-MIPPy sensors. The dense CNT-MIPPy sensor presented the highest sensitivity, about 15 times better when compared to the conventional thin film, whereas an improvement of 3.6 times was recorded on the sparse CNT. However, due to the small tube-to-tube spacing in the dense CNT array, electrode fouling was observed during the detection of concentrated caffeine in phosphate buffer solution. A new I-V characterization method using pulsed amperometry was introduced to investigate the electrical characterization of these new devices. The resistance value derived from the I-V plot provides insight into the electrical conductivity of the CNT transducer and also the effective surface area for caffeine imprinting.