Nanopore processing in dielectric materials and dielectric template-assisted nanoarray synthesis : using pulsed bias to enhance process throughput and precision

An effective technique to improve the precision and throughput of energetic ion condensation through dielectric nanoporous templates and reduce nanopore clogging by using finely tuned pulsed bias is proposed. Multiscale numerical simulations of ion deposition show the possibility of controlling the dynamic charge balance on the upper template's surface to minimize ion deposition on nanopore sidewalls and to deposit ions selectively on the substrate surface in contact with the pore opening. In this way, the shapes of nanodots in template-assisted nanoarray fabrication can be effectively controlled. The results are applicable to various processes involving porous dielectric nanomaterials and dense nanoarrays.

Investigation on bioactivity of titanium dioxide thin films fabricated by electron cyclotron resonance plasma aided pulsed laser deposition

Titanium dioxide thin films with a rutile crystallinite size around 20 nm were fabricated by pulsed laser deposition (PLD) aided with an electron cyclotron resonance (ECR) plasma. With annealing treatment, the crystal size of the rutile crystallinite increased to 100 nm. The apatite-forming ability of the films as deposited and after annealing was investigated in a kind of simulated body fluid with ion concentrations nearly equal to those of human blood plasma. The results indicate that ECR aided PLD is an effective way both to fabricate bioactive titanium dioxide thin films and to optimize the bioactivity of titanium dioxide, with both crystal size and defects of the film taken into account.

Pulsed i-PVD of dielectric nanodot arrays using a nanoporous template

The results of multi-scale numerical simulations of pulsed i-PVD template-assisted nanofabrication of ZnO nanodot arrays on a silicon substrate are presented. The ratios and spatial distributions of the ion fluxes deposited on the lateral and bottom surfaces of the nanopores are computed as a function of the external bias and plasma parameters. The results show that the pulsed bias plays a significant role in the ion current distribution inside the nanopores. The results of numerical experiments of this work suggest that by finely adjusting the pulse voltage, the pulse duration and the duty cycle of the external pulsed bias, the nanopore clogging can be successfully avoided during the deposition and the shapes of the deposited ZnO nanodots can be effectively controlled. A figure is presented.

Low-phosporous nickel-coated carbon microcoils : Controlling microstructure through an electroless plating process

Carbon microcoils (CMCs) have been coated with a nickel-phosphorus (Ni-P) film using an electroless plating process, with sodium hypophosphite as a reducing agent in an alkaline bath. CMC composites have potential applications as microwave absorption materials. The morphology, elemental composition and phases in the coating layer of the CMCs and Ni-coated CMCs were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The effects of process parameters such as pH, temperature and coating time of the plating bath on the phosphorus content and deposition rate of the electroless Ni-P coating were studied. The results revealed that a continuous, uniform and low-phosphorous nickel coating was deposited on the surface of the CMCs for 20 min at pH 9.0, plating bath temperature 70 °C. The as-deposited coatings with approximately 4.5 wt.% phosphorus were found to consist of a mix of nano- and microcrystalline phases. The mean particle size of Ni-P nanoparticles on the outer surface of the CMCs was around 11.9 nm. The deposition rate was found to moderately increase with increasing pH, whereas, the phosphorous content of the deposit exhibited a significant decrease. Moreover, the material of the coating underwent a phase transition between an amorphous and a crystalline structure. The thickness of the deposit and the deposition rate may be controlled through careful variation of the coating time and plating bath temperature.

Nutrient element-based bioceramic coatings on titanium alloy stimulating osteogenesis by inducing beneficial osteoimmmunomodulation

A paradigm shift has taken place in which bone implant materials has gone from being relatively inert to having immunomodulatory properties, indicating the importance of immune response when these materials interact with the host tissues. It has therefore become important to endow the implant materials with immunomodulatory properties favouring osteogenesis and osseointegration. Strontium, zinc and silicon are bioactive elements that have important roles in bone metabolism and that also elicit significant immune responses. In this study, Sr-, Zn- and Si-containing bioactive Sr2ZnSi2O7 (SZS) ceramic coatings on Ti–6Al–4V were successfully prepared by a plasma-spray coating method. The SZS coatings exhibited slow release of the bioactive ions with significantly higher bonding strength than hydroxyapatite (HA) coatings. SZS-coated Ti–6Al–4V elicited significant effects on the immune cells, inhibiting the release of pro-inflammatory cytokines and fibrosis-enhancing factors, while upregulating the expression of osteogenic factors of macrophages; moreover, it could also inhibit the osteoclastic activities. The RANKL/RANK pathway, which enhances osteoclastogenesis, was inhibited by the SZS coatings, whereas the osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs) was significantly enhanced by the SZS coatings/macrophages conditioned medium, probably via the activation of BMP2 pathway. SZS coatings are, therefore, a promising material for orthopaedic applications, and the strategy of manipulating the immune response by a combination of bioactive elements with controlled release has the potential to endow biomaterials with beneficial immunomodulatory properties.

On natures of sub-gap photoelectric and optical spectra in nitrogen-contaminated nanocrystalline diamond

Experimentally observed optical and photoelectrical spectra of nitrogen-contaminated (unintentionally doped) nano-crystalline CVD diamond films are simulated using semi-empirical adiabatic General Skettrup Model (GSM), which presumes dominant contributions of defect states from sp 3-coordinated intra-granular carbon atoms to intra-band single electron spectrum N(E) of the material. This picture disagrees with a common viewpoint that the N(E) spectrum of the gap states in diamond powders and polycrystalline CVD films mainly originates from π and π* bonds of sp2-coordinated carbon atoms, which are distributed nearly uniformly over outer surfaces and/or interfaces of the diamond grains. The GSM predicts as well strong effect of granular morphology on the density of intra-band defect states in polycrystalline diamonds.

Plasma-controlled nanocrystallinity and phase composition of TiO2 : a smart way to enhance biomimetic response

This contribution sheds light on the role of crystal size and phase composition in inducing biomimetic apatite growth on the surface of nanostructured titania films synthesized by reactive magnetron sputtering of Ti targets in Ar+O2 plasmas. Unlike most existing techniques, this method enables one to deposit highly crystalline titania films with a wide range of phase composition and nanocrystal size, without any substrate heating or postannealing. Moreover, by using this dry plasma-based method one can avoid surface hydroxylation at the deposition stage, almost inevitable in wet chemical processes. Results of this work show that high phase purity and optimum crystal size appear to be the essential requirement for efficient apatite formation on magnetron plasma-fabricated bioactive titania coatings. © 2006 Wiley Periodicals, Inc.

The complete mitochondrial genome of the yellow coaster, Acraea issoria (Lepidoptera: Nymphalidae: Heliconiinae: Acraeini): sequence, gene organization and a unique tRNA translocation event

In this paper, the complete mitochondrial genome of Acraea issoria (Lepidoptera: Nymphalidae: Heliconiinae: Acraeini) is reported; a circular molecule of 15,245 bp in size. For A. issoria, genes are arranged in the same order and orientation as the complete sequenced mitochondrial genomes of the other lepidopteran species, except for the presence of an extra copy of tRNAIle(AUR)b in the control region. All protein-coding genes of A. issoria mitogenome start with a typical ATN codon and terminate in the common stop codon TAA, except that COI gene uses TTG as its initial codon and terminates in a single T residue. All tRNA genes possess the typical clover leaf secondary structure except for tRNASer(AGN), which has a simple loop with the absence of the DHU stem. The sequence, organization and other features including nucleotide composition and codon usage of this mitochondrial genome were also reported and compared with those of other sequenced lepidopterans mitochondrial genomes. There are some short microsatellite-like repeat regions (e.g., (TA)9, polyA and polyT) scattered in the control region, however, the conspicuous macro-repeats units commonly found in other insect species are absent.

A comparative study of Sr-incorporated mesoporous bioactive glass scaffolds for regeneration of osteopenic bone defects

SUMMARY: Recently, the use of the pharmacological agent strontium ranelate has come to prominence for the treatment of osteoporosis. While much investigation is focused on preventing disease progression, here we fabricate strontium-containing scaffolds and show that they enhance bone defect healing in the femurs of rats induced by ovariectomy. INTRODUCTION: Recently, the use of the pharmacological agent strontium ranelate has come to prominence for the treatment of osteoporosis due to its ability to prevent bone loss in osteoporotic patients. Although much emphasis has been placed on using pharmacological agents for the prevention of disease, much less attention has been placed on the construction of biomaterials following osteoporotic-related fracture. The aim of the present study was to incorporate bioactive strontium (Sr) trace element into mesoporous bioactive glass (MBG) scaffolds and to investigate their in vivo efficacy for bone defect healing in the femurs of rats induced by ovariectomy. METHODS: In total, 30 animals were divided into five groups as follows: (1) empty defect (control), (2) empty defects with estrogen replacement therapy, (3) defects filled with MBG scaffolds alone, (4) defects filled with MBG + estrogen replacement therapy, and (5) defects filled with strontium-incorporated mesopore-bioglass (Sr-MBG) scaffolds. RESULTS: The two groups demonstrating the highest levels of new bone formation were the defects treated with MBG + estrogen replacement therapy and the defects receiving Sr-MBG scaffolds as assessed by μ-CT and histological analysis. Furthermore, Sr scaffolds had a reduced number of tartrate-resistant acid phosphatase-positive cells when compared to other modalities. CONCLUSION: The results from the present study demonstrate that the local release of Sr from bone scaffolds may improve fracture repair. Future large animal models are necessary to investigate the future relationship of Sr incorporation into biomaterials.

Plasma Enabled Fabrication of Silicon Carbide Nanostructures

Silicon carbide is one of the promising materials for the fabrication of various one- and two-dimensional nanostructures. In this chapter, we discuss experimental and theoretical studies of the plasma-enabled fabrication of silicon carbide quantum dots, nanowires, and nanorods. The discussed fabrication methods include plasma-assisted growth with and without anodic aluminium oxide membranes and with or without silane as a source of silicon. In the silane-free experiments, quartz was used as a source of silicon to synthesize the silicon carbide nanostructures in an environmentally friendly process. The mechanism of the formation of nanowires and nanorods is also discussed.

Spectroscopic vibrations of austinite (CaZnAsO4⋅OH) and its mineral structure : Implications for identification of secondary arsenic-containing mineral

Austinite (CaZnAsO4⋅OH) is a unique secondary mineral in arsenic-contaminated mine wastes. The infrared and Raman spectroscopies were used to characterize the austenite vibrations. The IR bands at 369, 790 and 416 cm−1 are assigned to the ν2, ν3 and ν4 vibrations of AsO43− unit, respectively. The Raman bands at 814, 779 and 403 cm−1 correspond to the ν1, ν3 and ν4 vibrations of AsO43− unit respectively. The sharp bands at 3265 cm−1 for IR and 3270 cm−1 both reveals that the structural hydroxyl units exist in the austenite structure. The IR and Raman spectra both show that some SO4 units isomorphically replace AsO4 in austinite. X-ray single crystal diffraction provides the arrangement of each atom in the mineral structure, and also confirms that the conclusions made from the vibrational spectra. Micro-powder diffraction was used to confirm our mineral identification due to the small quantity of the austenite crystals.

Atmospheric-pressure plasma jets : effect of gas flow, active species, and snake-like bullet propagation

Cold atmospheric-pressure plasma jets have recently attracted enormous interest owing to numerous applications in plasma biology, health care, medicine, and nanotechnology. A dedicated study of the interaction between the upstream and downstream plasma plumes revealed that the active species (electrons, ions, excited OH, metastable Ar, and nitrogen-related species) generated by the upstream plasma plume enhance the propagation of the downstream plasma plume. At gas flows exceeding 2 l/min, the downstream plasma plume is longer than the upstream plasma plume. Detailed plasma diagnostics and discharge species analysis suggest that this effect is due to the electrons and ions that are generated by the upstream plasma and flow into the downstream plume. This in turn leads to the relatively higher electron density in the downstream plasma. Moreover, high-speed photography reveals a highly unusual behavior of the plasma bullets, which propagate in snake-like motions, very differently from the previous reports. This behavior is related to the hydrodynamic instability of the gas flow, which results in non-uniform distributions of long-lifetime active species in the discharge tube and of surface charges on the inner surface of the tube.

Improvement of the mode II interface fracture toughness of glass fiber reinforced plastics/aluminum laminates through vapor grown carbon fiber interleaves

The effects of acid treatment, vapor grown carbon fiber (VGCF) interlayer and the angle, i.e., 0° and 90°, between the rolling stripes of an aluminum (Al) plate and the fiber direction of glass fiber reinforced plastics (GFRP) on the mode II interlaminar mechanical properties of GFRP/Al laminates were investigated. The experimental results of an end notched flexure test demonstrate that the acid treatment and the proper addition of VGCF can effectively improve the critical load and mode II fracture toughness of GFRP/Al laminates. The specimens with acid treatment and 10 g m−2 VGCF addition possess the highest mode II fracture toughness, i.e., 269% and 385% increases in the 0° and 90° specimens, respectively compared to those corresponding pristine ones. Due to the induced anisotropy by the rolling stripes on the aluminum plate, the 90° specimens possess 15.3%–73.6% higher mode II fracture toughness compared to the 0° specimens. The improvement mechanisms were explored by the observation of crack propagation path and fracture surface with optical, laser scanning and scanning electron microscopies. Moreover, finite element analyses were carried out based on the cohesive zone model to verify the experimental fracture toughness and to predict the interface shear strength between the aluminum plates and GFRP laminates.

Improved energy harvesting capability of poly(vinylidene fluoride) films modified by reduced graphene oxide

Piezoelectric energy harvesters can be used to convert ambient energy into electrical energy and power small autonomous devices. In recent years, massive effort has been made to improve the energy harvesting ability in piezoelectric materials. In this study, reduced graphene oxide was added into poly(vinylidene fluoride) to fabricate the piezoelectric nanocomposite films. Open-circuit voltage and electrical power harvesting experiments showed remarkable enhancement in the piezoelectricity of the fabricated poly(vinylidene fluoride)/reduced graphene oxide nanocomposite, especially at an optimal reduced graphene oxide content of 0.05 wt%. Compared to pristine poly(vinylidene fluoride) films, the open-circuit voltage, the density of harvested power of alternating current, and direct current of the poly(vinylidene fluoride)/reduced graphene oxide nanocomposite films increased by 105%, 153%, and 233%, respectively, indicating a great potential for a broad range of applications.

Furan substituted diketopyrrolopyrrole and thienylenevinylene based low band gap copolymer for high mobility organic thin film transistors

A novel solution processable donor-acceptor (D-A) based low band gap polymer semiconductor poly{3,6-difuran-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4- c]pyrrole-1,4-dione-alt-thienylenevinylene} (PDPPF-TVT), was designed and synthesized by a Pd-catalyzed Stille coupling route. An electron deficient furan based diketopyrrolopyrrole (DPP) block and electron rich thienylenevinylene (TVT) donor moiety were attached alternately in the polymer backbone. The polymer exhibited good solubility, film forming ability and thermal stability. The polymer exhibits wide absorption bands from 400 nm to 950 nm (UV-vis-NIR region) with absorption maximum centered at 782 nm in thin film. The optical band gap (Eoptg) calculated from the polymer film absorption onset is around 1.37 eV. The π-energy band level (ionization potential) calculated by photoelectron spectroscopy in air (PESA) for PDPPF-TVT is around 5.22 eV. AFM and TEM analyses of the polymer reveal nodular terrace morphology with optimized crystallinity after 200 °C thermal annealing. This polymer exhibits p-channel charge transport characteristics when used as the active semiconductor in organic thin-film transistor (OTFT) devices. The highest hole mobility of 0.13 cm 2 V -1 s -1 is achieved in bottom gate and top-contact OTFT devices with on/off ratios in the range of 10 6-10 7. This work reveals that the replacement of thiophene by furan in DPP copolymers exhibits such a high mobility, which makes DPP furan a promising block for making a wide range of promising polymer semiconductors for broad applications in organic electronics.