A Model Procedure for Catalytic Conversion of Waste Cotton into Useful Chemicals.

Cotton is grown in about 90 countries and accounts for 24% of the fibers used in the global production of textiles. In 2018/2019, 25.8 Mt of cotton were produced around the world. Since this natural product consists mainly of cellulose, it can be used as a raw material in the so-called "sugar economy". This paper discusses a model procedure for thermally assisted acidic hydrolysis of cotton into glucose and subsequent oxidation of the glucose into calcium gluconate over Pd-Au/SiO2 catalyst. In the first step, H2SO4 was used as a catalyst for hydrolysis. The cotton hydrolysates were neutralized using CaCO3 and applied as a substrate in the second step, where glucose was oxidized over Pd-Au/SiO2 prepared by ultrasound assisted co-impregnation. With the appropriate Au/Pd molar ratio, small crystallites of palladium and gold were created which were active and selective towards the formation of gluconate ions. This approach to the transformation of glucose represents as a viable alternative to biological processes using fungal and bacterial species, which are sensitive to the presence of inhibitors such as furfurals and levulinic acid in hydrolysates.

Nanofibrous TiO2 produced using alternating field electrospinning of titanium alkoxide precursors: crystallization and phase development.

High-yield, free-surface alternating field electrospinning (AFES) was effectively used in the fabrication of titanium oxide nanofibrous materials from the precursors based on titanium alkoxide and a blend of polyvinylpyrrolidone and hydroxypropyl cellulose. The alkoxide/polymer mass ratio in the precursor solution has significant effects on the precursor fiber production rate as well as the structure of resulting TiO2 nanofibers after thermal processing of precursor fibers at temperatures from 500 to 1000 °C. Within the range of tested process parameters, the best fiber production rate of ∼5.2 g h-1 was achieved, in terms of the mass of crystallized TiO2 nanofibers, with the precursor that corresponded to 1.5 : 1 TiO2/polymer mass ratio. TiO2 nanofibers produced by calcination at 500 °C for 3 h had 100-500 nm diameters and were composed of anatase (20-25 nm crystallite size) with rutile content 0.1-6.0 mol%, depending on the precursor composition. A considerable amount of anatase phase (up to 80 mol%) can be retained after thermal processing of TiO2 nanofibers at 750 °C for 3 h. A nanofibrous material composed of smooth and long, predominantly monocrystalline rutile, fibrous segments was produced at 1000 °C from the precursor with 2.5 : 1 TiO2/polymer mass ratio.

Fabrication of dual-functional composite yarns with a nanofibrous envelope using high throughput AC needleless and collectorless electrospinning.

Nanotechnologies allow the production of yarns containing nanofibres for use in composites, membranes and biomedical materials. Composite yarns with a conventional thread core for mechanical strength and a nanofibrous envelope for functionality, e.g. biological, catalytic, have many advantages. Until now, the production of such yarns has been technologically difficult. Here, we show an approach to composite yarn production whereby a plume of nanofibers generated by high throughput AC needleless and collectorless electrospinning is wound around a classic thread. In the resulting yarn, nanofibres can form up to 80% of its weight. Our yarn production speed was 10 m/min; testing showed this can be increased to 60 m/min. After the yarn was embedded into knitwear, scanning electron microscope images revealed an intact nanofibrous envelope of the composite yarn. Our results indicate that this production method could lead to the widespread production and use of composite nanofibrous yarns on an industrial scale.

WxC-ß-SiC Nanocomposite Catalysts Used in Aqueous Phase Hydrogenation of Furfural.

This study investigates the effects of the addition of tungsten on the structure, phase composition, textural properties and activities of ß-SiC-based catalysts in the aqueous phase hydrogenation of furfural. Carbothermal reduction of SiO2 in the presence of WO3 at 1550 °C in argon resulted in the formation of WxC-ß-SiC nanocomposite powders with significant variations in particle morphology and content of WxC-tipped ß-SiC nano-whiskers, as revealed by TEM and SEM-EDS. The specific surface area (SSA) of the nanocomposite strongly depended on the amount of tungsten and had a notable impact on its catalytic properties for the production of furfuryl alcohol (FA) and tetrahydrofurfuryl alcohol (THFA). Nanocomposite WxC-ß-SiC catalysts with 10 wt % W in the starting mixture had the highest SSA and the smallest WxC crystallites. Some 10 wt % W nanocomposite catalysts demonstrated up to 90% yield of THFA, in particular in the reduction of furfural derived from biomass, although the reproducible performance of such catalysts has yet to be achieved.

Nano-TiO2 particles impair adhesion of airway epithelial cells to fibronectin.

Titanium dioxide engineered nanoparticles (nano-TiO(2)) are widely used in the manufacturing of a number of products. Due to their size (<100 nm), when inhaled they may be deposited in the distal lung regions and damage Clara cells. We investigated the mechanisms by which short-term (1-h) incubation of human airway Clara-like (H441) cells to nano-TiO(2) (6 nm in diameter) alters the ability of H441 cells to adhere to extracellular matrix. Our results show that 1h post-incubation, there was a 3-fold increase of extracellular H(2)O(2), increased intracellular oxidative stress as demonstrated by 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) oxidation, and a 5-fold increase of phosphor-ERK1/2 as measured by Western blotting. These changes were accompanied by a 25% decrease of H441 adherence to fibronectin (p<0.05 compared to vehicle incubated H441 cells). Pretreatment with the ERK1/2 inhibitor U0126 for 3h, partially prevented this effect. In conclusion, short-term exposure of H441 cells to nano-TiO(2) appears to reduce adherence to fibronectin due to oxidative stress and activation of ERK1/2.

Titanium oxide nanoparticle instillation induces inflammation and inhibits lung development in mice.

Nanoparticles are used in an increasing number of biomedical, industrial, and food applications, but their safety profiles in developing organisms, including the human fetus and infant, have not been evaluated. Titanium oxide (TiO(2)) nanoparticles, which are commonly used in cosmetics, sunscreens, paints, and food, have been shown to induce emphysema and lung inflammation in adult mice. We hypothesized that exposure of newborn mice to TiO(2) would induce lung inflammation and inhibit lung development. C57BL/6 mice were exposed to TiO(2) (anatase; 8-10 nm) nanoparticles by intranasal instillation as a single dose on postnatal day 4 (P4) or as three doses on postnatal days 4, 7, and 10 (each dose = 1 µg/g body wt). Measurements of lung function (compliance and resistance), development (morphometry), inflammation (histology; multiplex analysis of bronchoalveolar lavage fluid for cytokines; PCR array and multiplex analysis of lung homogenates for cytokines) was performed on postnatal day 14. It was observed that a single dose of TiO(2) nanoparticles led to inflammatory cell influx, and multiple doses led to increased inflammation and inhibition of lung development without significant effects on lung function. Macrophages were noted to take up the TiO(2) nanoparticles, followed by polymorphonuclear infiltrate. Multiple cytokines and matrix metalloproteinase-9 were increased in lung homogenates, and VEGF was reduced. These results suggest that exposure of the developing lung to nanoparticles may lead to ineffective clearance by macrophages and persistent inflammation with resulting effects on lung development and may possibly impact the risk of respiratory disorders in later life.

Sputtered tungsten-based ternary and quaternary layers for nanocrystalline diamond deposition.

Many of today's demanding applications require thin-film coatings with high hardness, toughness, and thermal stability. In many cases, coating thickness in the range 2-20 microm and low surface roughness are required. Diamond films meet many of the stated requirements, but their crystalline nature leads to a high surface roughness. Nanocrystalline diamond offers a smoother surface, but significant surface modification of the substrate is necessary for successful nanocrystalline diamond deposition and adhesion. A hybrid hard and tough material may be required for either the desired applications, or as a basis for nanocrystalline diamond film growth. One possibility is a composite system based on carbides or nitrides. Many binary carbides and nitrides offer one or more mentioned properties. By combining these binary compounds in a ternary or quaternary nanocrystalline system, we can tailor the material for a desired combination of properties. Here, we describe the results on the structural and mechanical properties of the coating systems composed of tungsten-chromium-carbide and/or nitride. These WC-Cr-(N) coatings are deposited using magnetron sputtering. The growth of adherent nanocrystalline diamond films by microwave plasma chemical vapor deposition has been demonstrated on these coatings. The WC-Cr-(N) and WC-Cr-(N)-NCD coatings are characterized with atomic force microscopy and SEM, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and nanoindentation.

Mesenchymal stem cell responses to bone-mimetic electrospun matrices composed of polycaprolactone, collagen I and nanoparticulate hydroxyapatite.

The performance of biomaterials designed for bone repair depends, in part, on the ability of the material to support the adhesion and survival of mesenchymal stem cells (MSCs). In this study, a nanofibrous bone-mimicking scaffold was electrospun from a mixture of polycaprolactone (PCL), collagen I, and hydroxyapatite (HA) nanoparticles with a dry weight ratio of 50/30/20 respectively (PCL/col/HA). The cytocompatibility of this tri-component scaffold was compared with three other scaffold formulations: 100% PCL (PCL), 100% collagen I (col), and a bi-component scaffold containing 80% PCL/20% HA (PCL/HA). Scanning electron microscopy, fluorescent live cell imaging, and MTS assays showed that MSCs adhered to the PCL, PCL/HA and PCL/col/HA scaffolds, however more rapid cell spreading and significantly greater cell proliferation was observed for MSCs on the tri-component bone-mimetic scaffolds. In contrast, the col scaffolds did not support cell spreading or survival, possibly due to the low tensile modulus of this material. PCL/col/HA scaffolds adsorbed a substantially greater quantity of the adhesive proteins, fibronectin and vitronectin, than PCL or PCL/HA following in vitro exposure to serum, or placement into rat tibiae, which may have contributed to the favorable cell responses to the tri-component substrates. In addition, cells seeded onto PCL/col/HA scaffolds showed markedly increased levels of phosphorylated FAK, a marker of integrin activation and a signaling molecule known to be important for directing cell survival and osteoblastic differentiation. Collectively these results suggest that electrospun bone-mimetic matrices serve as promising degradable substrates for bone regenerative applications.

Nanostructured carbon beads--properties and biomedical applications.

In this study, amorphous carbonaceous nanoparticles were prepared by a simple hydrothermal process using glucose as precursor. The nearly perfect spherical particles (beads) with the dimensions in the range of 10-500 nm were obtained depending on the main process parameters (precursor concentration, temperature, and time). The particles size, surface morphology, structure, and composition have been examined by TEM, SEM, X-ray diffraction, XPS, FTIR and Raman spectroscopy. These amorphous carbonaceous nanobeads (a-CNBs) have been found nontoxic in vitro with a variety of cultured cell lines. The size-dependent effect of a-CNBs addition on cell function has been observed. For example, a-CNBs can, in some cases, substantially increase interleukin-12 (IL-12) production by bone marrow dendritic cells. It has been further demonstrated that a-CNBs can be modified with fluorescent dye molecules or loaded with anti-cancer drugs for bioimaging or therapeutic purposes, respectively. The results of these tests and the strategies for the particle preparation and functionalization for biomedical applications have been discussed.

Tribological properties of undoped and boron-doped nanocrystalline diamond films.

Undoped and boron-doped nanocrystalline (NCD) diamond films were deposited on mirror polished Ti-6Al-4V substrates in a Microwave Plasma Assisted Chemical Vapor Deposition system. Sliding wear tests were conducted in ambient air with a nanotribometer. A systematic study of the tribological properties for both undoped and boron-doped NCD films were carried out. It was found for diamond/diamond sliding, coefficient of friction decreases with increasing normal loads. It was also found that the wear rate of boron-doped NCD films is about 10 times higher than that of undoped films. A wear rate of ~5.2×10(-9) mm(3)/Nm was found for undoped NCD films. This value is comparable to the best known value of that of polished polycrystalline diamond films. Although no surface deformation, film delamination or micro-cracking were observed for undoped films, boron-doped NCD film undergoes a critical failure at a normal stress of 2.2 GPa, above which surface deformation is evident. Combined with high hardness and modulus, tunable conductivity and improved open air thermal stability, boron-doped nanocrystalline diamond film has tremendous potentials for applications such as Atomic Force Microscope probes, Micro-Electro-Mechanical System devices and biomedical sensors.

Nanomechanical properties of electrospun composite scaffolds based on polycaprolactone and hydroxyapatite.

Fibrous nanocomposite scaffolds were electrospun from dispersions of hydroxyapatite nanoparticles (nanoHA) in polycaprolactone (PCL) with varying nanoHA contents (from 0% to 50% by weight). Such scaffolds were produced to mimic the nano-features of the extracellular matrix (ECM) for natural bone tissue regeneration. NanoHA was found to be well dispersed in the PCL fibers up to the addition of 30 wt%, whereas beads and agglomeration of HA particles was observed above this nanoHA concentration. The structural and morphological characterizations were evaluated by scanning electron microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD). The average fiber diameter decreased with increased nanoHA concentration. The nanomechanical properties of the as-spun fibrous scaffolds as well as pressure-consolidated (pelletized) composites were evaluated by nanoindentation. Elastic modulus increased with increasing HA content, but was especially pronounced for 40-50% HA content where the indenter tip is more likely to probe agglomerated HA particles.

Hydroxyapatite nanoparticle loaded collagen fiber composites: microarchitecture and nanoindentation study.

Hydroxyapatite (HA) nanoparticle-collagen composite materials with various HA/collagen weight ratios were prepared from HA/collagen dispersions using the solution deposition and electrospinning with static or rotating collectors. The composites with nanoparticle HA to collagen weight ratio of 80:20 can be easily prepared in the solution deposition approach, whereas in the electrospun fibrous composites it was possible to reach a maximum HA/collagen weight ratio of 30:70 while maintaining a good fibrous structure. The structure, surface morphology, and nanoindentation properties of these nanoparticle HA/collagen composites with different microarchitectures were investigated. The values from 0.2 GPa to 20 GPa for nanoindentation Young's modulus and from 25 MPa to 500 MPa for hardness, were obtained depending on the fabrication technique, composition, and microarchitecture of the composites. It was observed that the nanoindentation Young's modulus and hardness of the HA/collagen composite materials seem to achieve maximum values for 45-60% HA content by weight.

Preliminary tribological evaluation of nanostructured diamond coatings against ultra-high molecular weight polyethylene.

BACKGROUND: Some loss of joint prostheses has been attributed to osteolytic loosening associated with debris from wear of polyethylene articulating against metal alloys. Reduced polyethylene wear has been reported with ceramics serving as an alternative counterface. METHODS: Nanostructured Diamond (NSD) coatings were deposited onto Ti6Al4V by microwave plasma-assisted chemical vapor deposition, with both hydrogen-rich (H-NSD) and helium-rich (He-NSD) feedgas mixtures. Pin-on-disk wear tests of polyethylene against NSD and CoCr were performed in serum lubrication at body temperature. Scanning electron microscopy was used to examine surface morphology, and nanoindentation was used to determine hardness and modulus of the polyethylene wear surfaces. Raman spectroscopy, surface roughness, and wettability analyses of the NSD coatings were performed. RESULTS: Raman spectroscopy confirmed sp(2) and sp(3) bonded carbon in the NSD coatings. No significant differences in wear factors were found between polyethylene on H-NSD, He-NSD, and CoCr, despite higher roughness and friction coefficients for the He-NSD and H-NSD coatings, compared with CoCr. Contact angles for the diamond coatings were reduced following the wear tests, indicating that these surfaces became more hydrophilic. Numerous small protuberances were observed on pins articulated against CoCr, and a single, large protuberance was observed in polyethylene-on-NSD. These features were conjectured to be reconsolidated polyethylene particles. Nanoindentation modulus and hardness of the worn polyethylene surfaces were lower for polyethylene-on-diamond than for polyethylene-on-CoCr. CONCLUSIONS: As a counterface to polyethylene, NSD-coated Ti6Al4V produced wear factors comparable to CoCr in the present pin-on-disk tests, a promising step towards its use in joint replacement bearing applications.

Synthesis of complex shape gold nanoparticles in water-methanol mixtures.

Gold nanoparticles with shapes which varied from spheres to multipods and polygons were prepared with a seedless approach in water/methanol mixtures in the presence of polyvinyl alcohol using sodium ascorbate as the reducing agent. The shape of Au nanoparticles is critically affected by the water/methanol ratio, as well as by the ratio of hydrogen tetrachloroaurate (HAuCl4) to sodium ascorbate and the concentration of HAuCl4 in the reaction mixture. A decreased ratio of water to methanol below 30/70 leads to the formation of multi-branched nanoparticles with the size in the range of 30-70 nm at relatively low HAuCl4 concentration, whereas polygons are formed when HAuCl4 concentration increases. The polyvinyl alcohol stabilized multi-branched Au nanoparticle colloids were stable at room temperature for a period of at least six-month.