Low-temperature assembly of ordered carbon nanotip arrays in low-frequency, high-density inductively coupled plasmas

High-density inductively coupled plasma (ICP)-assisted self-assembly of the ordered arrays of various carbon nanostructures (NS) for the electron field emission applications is reported. Carbon-based nano-particles, nanotips, and pyramid-like structures, with the controllable shape, ordering, and areal density are grown under remarkably low process temperatures (260-350 °C) and pressures (below 0.1 Torr), on the same Ni-based catalyst layers, in a DC bias-controlled floating temperature regime. A high degree of positional and directional ordering, elevated sp2 content, and a well-structured graphitic morphology are achieved without the use of pre-patterned or externally heated substrates.

A Raman spectroscopic study of the arsenate mineral chenevixite Cu2Fe23+(AsO4)2(OH)4⋅H2O

We have studied the mineral chenevixite from Manto Cuba Mine, San Pedro de Cachiyuyo District, Inca de Oro, Chañaral Province, Atacama Region, Chile, using a combination of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX) and vibrational spectroscopy. Qualitative chemical analysis shows a homogeneous composition, with predominance of As, Fe, Al, Cu, Fe and Cu. Minor amounts of Si were also observed. Raman spectroscopy complimented with infrared spectroscopy has been used to assess the molecular structure of the arsenate minerals chenevixite. Characteristic Raman and infrared bands of the (AsO4)3− stretching and bending vibrations are identified and described. The observation of multiple bands in the (AsO4)3− bending region offers support for the loss of symmetry of the arsenate anion in the structure of chenevixite. Raman bands attributable to the OH stretching vibrations of water and hydroxyl units were analysed. Estimates of the hydrogen bond distances were made based upon the OH stretching wavenumbers.

Visible-light-induced selective photocatalytic oxidation of benzylamine into imine over supported Ag/AgI photocatalysts

Titanate nanotubes (TNT) supported AgI nanoparticles were prepared by a two-step method: the deposition of Ag2O on titanate nanotubes from AgNO3 solution and the subsequent I-adsorption process from NaI solution. It is found that the supported AgI samples exhibited excellent photoactivity for the selective oxidation of benzylamine to the corresponding imine under visible light illumination and the photocatalyst can be used for many times without apparent activity loss. X-ray diffraction studies, transmission electron microscopy, diffuse reflectance UV-Vis spectroscopy and nitrogen adsorption measurements were used for the characterization of the as-prepared and recycled AgI samples. It is found that under visible light irradiation, AgI partially decomposed to produce Ag/AgI nanostructure and thus stabilized. The photoactivity of supported Ag/AgI for the selective oxidation of benzylamine was studied in terms of the light intensity, wavelength, temperature and substituent. It is proposed that the formation of plasmonic Ag nanoparticles should be responsible for the high activity and selectivity.

Three-dimensional analysis of budding sites and released virus suggests a revised model for HIV-1 morphogenesis

Current models of HIV-1 morphogenesis hold that newly synthesized viral Gag polyproteins traffic to and assemble at the cell membrane into spherical protein shells. The resulting late-budding structure is thought to be released by the cellular ESCRT machinery severing the membrane tether connecting it to the producer cell. Using electron tomography and scanning transmission electron microscopy, we find that virions have a morphology and composition distinct from late-budding sites. Gag is arranged as a continuous but incomplete sphere in the released virion. In contrast, late-budding sites lacking functional ESCRT exhibited a nearly closed Gag sphere. The results lead us to propose that budding is initiated by Gag assembly, but is completed in an ESCRT-dependent manner before the Gag sphere is complete. This suggests that ESCRT functions early in HIV-1 release-akin to its role in vesicle formation-and is not restricted to severing the thin membrane tether.

Adsorption of the herbicide 2,4-D on organo-palygorskite

Among the clay minerals, montmorillonite is the most extensively studied material using as adsorbents, but palygorskite and its organically modified products have been least explored for their potential use in contaminated water remediation. In this study, an Australian palygorskite was modified with cationic surfactants octadecyl trimethylammonium bromide and dioctadecyl dimethylammonium bromide at different doses. A full structural characterization of prepared organo-palygorskite by X-ray diffraction, infrared spectroscopy, surface analysis and thermogravimetric analysis was performed. The morphological changes of palygorskite before and after modification were recorded using scanning electron microscopy, which showed the surfactant molecules can attach on the surface of rod-like crystals and thus can weaken the interactions between palygorskite single crystals. Real surfactants loadings on organo-palygorskites were also calculated based on thermogravimetric analysis. 1 CEC, 2 CEC octadecyl trimethylammonium bromide modified palygorskites, 1 CEC and 2 CEC dioctadecyl dimethylammonium bromide modified palygorskites absorbed as much as 12 mg/g, 42 mg/g, 9 mg/g and 25 mg/g of 2,4- dichlorophenoxyacetic acid respectively. This study has shown a potential on organo-palygorskites for organic herbicide adsorption especially anionic ones from waste water. In addition, equilibration time effects and the Langmuir and Freundlich models fitting were also investigated in details.

Reduction and adsorption of Pb2+ in aqueous solution by nano zero-valent iron : a SEM, TEM and XPS study

This study reports the synthesis, characterization and application of nano zero-valent iron (nZVI). The nZVI was produced by a reduction method and compared with commercial available ZVI powder for Pb2+ removal from aqueous phase. Comparing with commercial ZVI, the laboratory made nZVI powder has a much higher specific surface area. XRD patterns have revealed zero valent iron phases in two ZVI materials. Different morphologies have been observed using SEM and TEM techniques. EDX spectrums revealed even distribution of Pb on surface after reaction. The XPS analysis has confirmed that immobilized lead was present in its zero-valent and bivalent forms. ‘Core-shell’ structure of prepared ZVI was revealed based on combination of XRD and XPS characterizations. In addition, comparing with Fluka ZVI, this lab made nZVI has much higher reactivity towards Pb2+ and within just 15 mins 99.9% removal can be reached. This synthesized nano ZVI material has shown great potential for heavy metal immobilization from waste water.

Dispersion of zero valent iron nanoparticles onto bentonites and the decolourization of orange II

Nano Zero valent iron (Fe0) were reported as an effective material for azo dye removal, however, similar to other nano-materials, ultra-fine powder has a strong tendency to agglomerate into larger particles, resulting in an adverse effect on both effective surface area and catalyst performance. Here we report nano sized Fe0 particles dispersed onto the surface of natural bentonites. X-ray diffraction was used to study the sample phases. Scanning electron microscopy and transmission electron microscopy were applied to study the morphology and morphological changes. Spherical individual Fe0 particles were observed after dispersion onto bentonites, and these samples were used for orange II (OII) decolourization with wide working pH range. Higher reactivity is attributed to good dispersion of Fe0 particles on clay minerals’ surface. This study is significant for providing novel modified clay based catalyst materials for the decolourization of azo dye contaminants from wastewater.

Nanomorphology influence on the light conversion mechanisms in highly efficient diketopyrrolopyrrole based organic solar cells

In this work, diketopyrrolopyrrole-based polymer bulk heterojunction solar cells with inverted and regular architecture have been investigated. The influence of the polymer:fullerene ratio on the photoactive film nanomorphology has been studied in detail. Transmission Electron Microscopy and Atomic Force Microscopy reveal that the resulting film morphology strongly depends on the fullerene ratio. This fact determines the photocurrent generation and governs the transport of free charge carriers. Slight variations on the PCBM ratio respect to the polymer show great differences on the electrical behavior of the solar cell. Once the polymer:fullerene ratio is accurately adjusted, power conversion efficiencies of 4.7% and 4.9% are obtained for inverted and regular architectures respectively. Furthermore, by correlating the optical and morphological characterization of the polymer:fullerene films and the electrical behavior of solar cells, an ad hoc interpretation is proposed to explain the photovoltaic performance as a function of this polymer:blend composition.

Water-based nanoparticulate solar cells using a diketopyrrolopyrrole donor polymer

Organic photovoltaic devices with either bulk heterojunction (BHJ) or nanoparticulate (NP) active layers have been prepared from a 1:2 blend of (poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1, 4-dione-alt-naphthalene}) (PDPP-TNT) and the fullerene acceptor, ([6,6]-phenyl C71-butyric acid methyl ester) (PC70BM). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used to investigate the morphology of the active layers of the two approaches. Mild thermal treatment of the NP film is required to promote initial joining of the NPs in order for the devices to function, however the NP structure is retained. Consequently, whereas gross phase segregation of the active layer occurs in the BHJ device spin cast from chloroform, the nanoparticulate approach retains control of the material domain sizes on the length scale of exciton diffusion in the materials. As a result, NP devices are found to generate more than twice the current density of BHJ devices and have a substantially greater overall efficiency. The use of aqueous nanoparticulate dispersions offers a promising approach to control the donor acceptor morphology on the nanoscale with the benefit of environmentally- friendly, solution-based fabrication. © 2014 the Owner Societies.

Impact of al passivation and cosputter on the structural property of β-FeSi2 for Al-Doped β-FeSi2/ n -Si(100) based solar cells application

The aluminum (Al) doped polycrystalline p-type β-phase iron disilicide (p-β-FeSi2) is grown by thermal diffusion of Al from Al-passivated n-type Si(100) surface into FeSi2 during crystallization of amorphous FeSi2 to form a p-type β-FeSi 2/n-Si(100) heterostructure solar cell. The structural and photovoltaic properties of p-type β-FeSi2/n-type c-Si structures is then investigated in detail by using X-ray diffraction, Raman spectroscopy, transmission electron microscopy analysis, and electrical characterization. The results are compared with Al-doped p-β-FeSi2 prepared by using cosputtering of Al and FeSi2 layers on Al-passivated n-Si(100) substrates. A significant improvement in the maximum open-circuit voltage (Voc) from 120 to 320 mV is achieved upon the introduction of Al doping through cosputtering of Al and amorphous FeSi2 layer. The improvement in Voc is attributed to better structural quality of Al-doped FeSi2 film through Al doping and to the formation of high quality crystalline interface between Al-doped β-FeSi2 and n-type c-Si. The effects of Al-out diffusion on the performance of heterostructure solar cells have been investigated and discussed in detail.

Chromosomal genotoxicity of nitrobenzene and benzonitrile

In order to investigate the chromosomal genotoxicity of nitrobenzene and benzonitrile, we studied the induction of micronuclei (MN) by these test compounds in V79 cells, as well as effects on the formation and stability of microtubules and on motor protein functions. No cytotoxicity was seen in V79 cell cultures in terms of Neutral red uptake after 18 h treatment with up to 1 mM nitrobenzene or 1 mM benzonitrile. Subsequently, a concentration range up to 100 μM was used in the experiments on induction of MN. Both test compounds exhibit a weak, but definitely positive test result compared to the solvent (DMSO) control. Minimal effect concentrations of nitrobenzene and benzonitrile appeared as low as 0.01 μM, and no-effect-concentrations were between 0.001 and 0.005 μM. Clearly enhanced MN rates were found at 0.1 μM and higher. Both, nitrobenzene and benzonitrile, induced mostly kinetochor (CREST)-positive micronuclei, thus characterising the chromosomal effects as aneugenic. In cell-free assays, a slight effect on tubulin assembly was observed at 1 mM nitrobenzene without addition of DMSO. Higher concentrations (5 mM) led to secondary effects. In presence of 1% DMSO, nitrobenzene exerted no detectable effect on tubulin assembly up to the solubility limit in water of about 15 mM. For benzonitrile in presence of DMSO, a clear dose-response of inhibition of tubulin assembly at 37°C was seen above the no-effect-concentration of 2 mM, with an IC50 of 13 mM and protein denaturation starting above a level of about 20 mM. The nature of the effects of nitrobenzene and benzonitrile on the association of tubulin to form microtubules was confirmed by electron microscopy. Treatment by either 5 mM nitrobenzene or 13 mM benzonitrile plus 1% DMSO left the microtubular structure intact whereas 5 mM nitrobenzene, in absence of DMSO, led to irregular cluster formations. The experiments demonstrate that both nitrobenzene and benzonitrile, in millimolar concentration ranges, may lead to interference with tubulin assembly in a cell-free system. The functionality of the tubulin-kinesin motor protein system was assessed using the microtubule gliding assay. Nitrobenzene affected the gliding velocity in a concentration-dependent manner, starting at about 7.5 μM and reaching complete inhibition of motility at 30 μM, whereas benzonitrile up to 200 μM did not affect the kinesin-driven gliding velocity. The micronucleus assay data demonstrate a chromosomal endpoint of genotoxicity of nitrobenzene and benzonitrile. Aneugenic effects of both compounds occur at remarkably low concentrations, with lowest-effect-concentrations being 0.1 μM. This points to the relevance of interactions with the cellular spindle apparatus.

A comparative study of the proliferation and osteogenic differentiation of human periodontal ligament cells cultured on β-TCP ceramics and demineralized bone matrix with or without osteogenic inducers in vitro

The repair of bone defects that result from periodontal diseases remains a clinical challenge for periodontal therapy. β-tricalcium phosphate (β-TCP) ceramics are biodegradable inorganic bone substitutes with inorganic components that are similar to those of bone. Demineralized bone matrix (DBM) is an acid-extracted organic matrix derived from bone sources that consists of the collagen and matrix proteins of bone. A few studies have documented the effects of DBM on the proliferation and osteogenic differentiation of human periodontal ligament cells (hPDLCs). The aim of the present study was to investigate the effects of inorganic and organic elements of bone on the proliferation and osteogenic differentiation of hPDLCs using three-dimensional porous β-TCP ceramics and DBM with or without osteogenic inducers. Primary hPDLCs were isolated from human periodontal ligaments. The proliferation of the hPDLCs on the scaffolds in the growth culture medium was examined using a Cell‑Counting kit‑8 (CCK-8) and scanning electron microscopy (SEM). Alkaline phosphatase (ALP) activity and the osteogenic differentiation of the hPDLCs cultured on the β-TCP ceramics and DBM were examined in both the growth culture medium and osteogenic culture medium. Specific osteogenic differentiation markers were examined using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). SEM images revealed that the cells on the β-TCP were spindle-shaped and much more spread out compared with the cells on the DBM surfaces. There were no significant differences observed in cell proliferation between the β-TCP ceramics and the DBM scaffolds. Compared with the cells that were cultured on β-TCP ceramics, the ALP activity, as well as the Runx2 and osteocalcin (OCN) mRNA levels in the hPDLCs cultured on DBM were significantly enhanced both in the growth culture medium and the osteogenic culture medium. The organic elements of bone may exhibit greater osteogenic differentiation effects on hPDLCs than the inorganic elements.

Characterization of the tail-specific protease (Tsp) from Legionella

Bacterial tail-specific proteases (Tsps) have been attributed a wide variety of functions including intracellular virulence, cell wall morphology, proteolytic signal cascades and stress response. This study tested the hypothesis that Tsp has a key function for the transmissive form of Legionella pneumophila. A tsp mutant was generated in Legionella pneumophila 130b and the characteristics of this strain and the isogenic wild-type were examined using a range of growth and proteomic analyses. Recombinant Tsp protein was also produced and analyzed. The L. pneumophila tsp mutant showed no defect in growth on rich media or during thermo-osmotic stress conditions. In addition, no defects in cellular morphology were observed when the cells were examined using transmission electron microscopy. Purified recombinant Tsp was found to be an active protease with a narrow substrate range. Proteome analysis using iTRAQ (5% coverage of the proteome) found that, of those proteins detected, only 5 had different levels in the tsp mutant compared to the wild type. ACP (Acyl Carrier Protein), which has a key role for Legionella differentiation to the infectious form, was reduced in the tsp mutant; however, tsp(-) was able to infect and replicate inside macrophages to the same extent as the wild type. Combined, these data demonstrate that Tsp is a protease but is not essential for Legionella growth or cell infection. Thus, Tsp may have functional redundancy in Legionella.

Vibrational spectroscopy of the borate mineral priceite : implications for the molecular structure

Priceite is a calcium borate mineral and occurs as white crystals in the monoclinic pyramidal crystal system. We have used a combination of Raman spectroscopy with complimentary infrared spectroscopy and scanning electron microscopy with Energy-dispersive X-ray Spectroscopy (EDS) to study the mineral priceite. Chemical analysis shows a pure phase consisting of B and Ca only. Raman bands at 956, 974, 991, and 1019 cm−1 are assigned to the BO stretching vibration of the B10O19 units. Raman bands at 1071, 1100, 1127, 1169, and 1211 cm−1 are attributed to the BOH in-plane bending modes. The intense infrared band at 805 cm−1 is assigned to the trigonal borate stretching modes. The Raman band at 674 cm−1 together with bands at 689, 697, 736, and 602 cm−1 are assigned to the trigonal and tetrahedral borate bending modes. Raman spectroscopy in the hydroxyl stretching region shows a series of bands with intense Raman band at 3555 cm−1 with a distinct shoulder at 3568 cm−1. Other bands in this spectral region are found at 3221, 3385, 3404, 3496, and 3510 cm−1. All of these bands are assigned to water stretching vibrations. The observation of multiple bands supports the concept of water being in different molecular environments in the structure of priceite. The molecular structure of a natural priceite has been assessed using vibrational spectroscopy.