Self-assembly of ferria - nanocellulose composite fibres.

An environmentally benign synthesis of a magnetically responsive carboxymethylated cellulose nanofibril-based material is reported. Applied experimental conditions lead to the in-situ formation of magnetite nanoparticles with primary particle sizes of 2.0-4.0 nm or secondary particles of 3.6-16.4 nm depending on whether nucleation occurred between individual carboxymethylated cellulose nanofibrils, or on exposed fibril surfaces. The increase in magnetite particle size on the cellulose fibril surfaces was attributed to Ostwald ripening, while the small particles formed within the carboxymethyl cellulose aggregates were presumably due to steric interactions. The magnetite nanoparticles were capable of coordinating to carboxymethylated cellulose nanofibrils to form large "fibre-like" assemblies. The confinement of small particles within aggregates of reductive cellulose molecules was most likely responsible for excellent conservation of magnetic characteristics on storage of this material. The possibility for using the material in drug delivery applications with release rate controlled by daylight illumination is presented.

Coordination of rare earth element cations on the surface of silica-derived nanoadsorbents.

Silica (SiO2)-derived nanoadsorbents are a powerful and attractive tool for the extraction and separation of rare earth elements (REE) from many perspectives such as reusability, efficiency and minimum impact on the environment. In the present work, we investigated two different methods of adsorption down to the molecular level: (1) the mechanism of the coordination of different groups of REE (light, medium, heavy) with iminodiacetic acid (IDA) was revealed by exploiting models obtained from X-ray crystallography, explaining the selectivity of this type of ligand, and (2) the mechanism of the seeding of RE(OH)3 initiated by SiO2-based nanoadsorbents was investigated by EXAFS, both individually and in combination with mechanism (1), showing the coexistence of both mechanisms. The REE loaded nanoadsorbents possess a high magnetic susceptibility. This property was studied by magnetometry to quantify the REE adsorption efficiency and compared with the values obtained from complexometry.

Enzyme immobilization on a nanoadsorbent for improved stability against heavy metal poisoning.

Magnetic nanoparticles modified with siloxane layers bearing amino and thiol functions have been used for immobilization of urease either by adsorption or via surface grafting. The activity of the immobilized enzyme in the hydrolysis of urea extended to the levels typical of the native enzyme, while its long-term stability in combination with magnetic retraction opened for its repeated use in both analysis and detoxification of bio-fluids. The immobilized urease revealed strongly enhanced stability and 65% activity in the presence of 0.1mmol/l of Hg(2+) or 0.3mmol/l of Cu(2+) while the native urease did not retain any activity at all. The enzyme grafting was shown to be a potentially perspective tool in alleviation of heavy metal poisoning and to be providing an opportunity for use of the developed adsorbents as both biosensors and bio-reactants for removal of urea from biofluids.

Self-assembled SnO2 micro- and nanosphere-based gas sensor thick films from an alkoxide-derived high purity aqueous colloid precursor.

Tin oxide is considered to be one of the most promising semiconductor oxide materials for use as a gas sensor. However, a simple route for the controllable build-up of nanostructured, sufficiently pure and hierarchical SnO2 structures for gas sensor applications is still a challenge. In the current work, an aqueous SnO2 nanoparticulate precursor sol, which is free of organic contaminants and sorbed ions and is fully stable over time, was prepared in a highly reproducible manner from an alkoxide Sn(OR)4 just by mixing it with a large excess of pure neutral water. The precursor is formed as a separate liquid phase. The structure and purity of the precursor is revealed using XRD, SAXS, EXAFS, HRTEM imaging, FTIR, and XRF analysis. An unconventional approach for the estimation of the particle size based on the quantification of the Sn-Sn contacts in the structure was developed using EXAFS spectroscopy and verified using HRTEM. To construct sensors with a hierarchical 3D structure, we employed an unusual emulsification technique not involving any additives or surfactants, using simply the extraction of the liquid phase, water, with the help of dry butanol under ambient conditions. The originally generated crystalline but yet highly reactive nanoparticles form relatively uniform spheres through self-assembly and solidify instantly. The spheres floating in butanol were left to deposit on the surface of quartz plates bearing sputtered gold electrodes, producing ready-for-use gas sensors in the form of ca. 50 µm thick sphere-based-films. The films were dried for 24 h and calcined at 300 °C in air before use. The gas sensitivity of the structures was tested in the temperature range of 150-400 °C. The materials showed a very quickly emerging and reversible (20-30 times) increase in electrical conductivity as a response to exposure to air containing 100 ppm of H2 or CO and short (10 s) recovery times when the gas flow was stopped.

Nano titania aided clustering and adhesion of beneficial bacteria to plant roots to enhance crop growth and stress management.

A novel use of Titania nanoparticles as agents in the nano interface interaction between a beneficial plant growth promoting bacterium (Bacillus amyloliquefaciens UCMB5113) and oilseed rape plants (Brassica napus) for protection against the fungal pathogen Alternaria brassicae is presented. Two different TiO2 nanoparticle material were produced by the Sol-Gel approach, one using the patented Captigel method and the other one applying TiBALDH precursor. The particles were characterized by transmission electron microscopy, thermogravimetric analysis, X-ray diffraction, dynamic light scattering and nano particle tracking analysis. Scanning electron microscopy showed that the bacterium was living in clusters on the roots and the combined energy-dispersive X-ray spectroscopy analysis revealed that titanium was present in these cluster formations. Confocal laser scanning microscopy further demonstrated an increased bacterial colonization of Arabidopsis thaliana roots and a semi-quantitative microscopic assay confirmed an increased bacterial adhesion to the roots. An increased amount of adhered bacteria was further confirmed by quantitative fluorescence measurements. The degree of infection by the fungus was measured and quantified by real-time-qPCR. Results showed that Titania nanoparticles increased adhesion of beneficial bacteria on to the roots of oilseed rape and protected the plants against infection.

Cellulose nanofiber-titania nanocomposites as potential drug delivery systems for dermal applications.

In this work, new efficient drug delivery systems based on cellulose nanofiber-titania nanocomposites grafted with three different types of model drugs such as diclofenac sodium, penicillamine-D and phosphomycin were successfully synthesized and displayed distinctly different controlled long-term release profiles. Three different methods of medicine introduction were used to show that various interactions between TiO2 and drug molecules could be used to control the kinetics of long-term drug release. All synthesis reactions were carried out in aqueous media. The morphology, chemical structure and properties of the obtained materials were characterized by SEM, TEM and AFM microscopy, nanoparticle tracking analysis, X-ray diffraction, and TGA analysis. According to FT-IR and UV-Vis spectroscopy data, the titania binds to cellulose nanofibers via formation of ester bonds and to drug molecules via formation of surface complexes. The drug release kinetics was studied in vitro for diclofenac sodium and penicillamine-D spectrophotometrically and for phosphomycin using a radio-labeling analysis with 33P-marked ATP as a model phosphate-anchored biomolecule. The results demonstrated that the obtained nanocomposites could potentially be applied in transdermal drug delivery for anesthetics, analgesics and antibiotics.

Antibacterial and photochemical properties of cellulose nanofiber-titania nanocomposites loaded with two different types of antibiotic medicines.

Nanocomposite dermal drug delivery systems based on cellulose nanofibers with grafted titania nanoparticles loaded by two antibiotic medicines from different classes, i.e. tetracycline (TC) and phosphomycin (Phos), were successfully produced by a "green chemistry" approach in aqueous media. The influence of a different surface binding mechanism between the drug molecule and modified cellulose nanofibers on the release of the drug and, as a result, on antimicrobial properties against common pathogens Gram-positive, Staphylococcus aureus and Gram-negative Escherichia coli was investigated. The disk diffusion method and broth culture tests using varying concentrations of drugs loaded to nanocomposites were carried out to investigate the antibacterial effects. The influence of UV irradiation on the stability of the obtained nanocomposites and their antibacterial properties after irradiation were also investigated, showing enhanced stability especially for the TC loaded materials. These findings suggest that the obtained nanocomposites are promising materials for the development of potentially useful antimicrobial patches.

The first depleted heterojunction TiO2-MOF-based solar cell.

A single-step hydrothermal synthesis of a TiO2-Mil-125 composite was applied for the first time to produce a depleted perovskite/TiO2-MOF heterojunction solar cell with 6.4% power conversion efficiency (PCE), characterized by durable stability in air.

Immobilization of urease on magnetic nanoparticles coated by polysiloxane layers bearing thiol- or thiol- and alkyl-functions.

Magnetically retrievable formulations of urease potentially promising for biomedical and environmental applications were constructed by immobilization of the enzyme on the surface of magnetite nanoparticles functionalized by siloxane layers with active thiol or thiol-and-alkyl moieties. The latter were deposited using a hydrolytic polycondensation reaction of tetraethoxysilane with either 3-mercaptopropyltrimethoxysilane, or with 3-mercaptopropyltrimethoxysilane and methyltriethoxysilane, or alternatively n-propyltriethoxysilane. Immobilization of urease was carried out in different ways for comparison: by adsorption, by entrapment during the hydrolytic polycondensation reaction, or by covalent bonding. For entrapment the enzyme was introduced into solution before functionalization of the magnetite. Entrapment bound high amounts of enzyme (more than 700 mg per g of carrier), but its activity was decreased compared to the native form to between 18 and 10%. In the case of covalent binding of urease using Ellman's Reagent, binding of the enzyme was almost as efficient as in the case of entrapment but its residual activity was 75%. The residual activity of urease immobilized by adsorption on the surface of thiol-functionalized particles was truly high as compared to that of the native enzyme (97%), but binding was significantly less efficient (46%). Introduction of alkyl functions permitted increase of the amounts of the adsorbed enzyme but its activity was somewhat decreased.

Synthesis of WO3 nanorods by reacting WO(OMe)4 under autogenic pressure at elevated temperature followed by annealing.

This article reports on the fabrication of WO(3) nanorods using an efficient straightforward synthetic technique, without a catalyst, and using a single precursor. The thermal dissociation of WO(OMe)(4) at 700 degrees C in a closed Swagelok cell under an air/inert atmosphere yielded W(18)O(49) nanorods. Annealing of W(18)O(49) at 500 degrees C under an air atmosphere led to the formation of pure WO(3) nanorods. The obtained products are characterized by morphological (scanning electron microscopy and transmission electron microscopy), structural (X-ray diffraction analysis, high-resolution scanning electron microscopy, and Raman spectroscopy), and compositional [energy-dispersive X-ray and elemental (C, H, N, S) analysis] measurements. The mechanism of the formation of nonstoichiometric W(18)O(49) nanorods is supported by the measured analytical data and several control experiments.

The Effect of a Magnetic Field on a RAPET (Reaction under Autogenic Pressure at Elevated Temperature) of MoO(OMe)(4): Fabrication of MoO(2) Nanoparticles Coated with Carbon or Separated MoO(2) and Carbon Particles.

In this article, we present results of the RAPET dissociation of MoO(OMe)4 at 700 degrees C in a closed Swagelok cell. The reaction produces molybdenum dioxide nanoparticles (20 nm) coated with carbon (20 nm). We have also carried out the same reaction under an applied magnetic field of 10 T. This reaction yielded different products. It produces a mixture of comparatively larger (50 nm) molybdenum dioxide nanoparticles and separated uncoated carbon particles (20-30 nm).

Preparation of porous cobalt and nickel oxides from corresponding alkoxides using a sonochemical technique and its application as a catalyst in the oxidation of hydrocarbons.

Porous nickel and cobalt oxides were prepared using their alkoxides as inorganic precursors. The stabilization of the mesostructure is especially critical for divalent elements such as Ni and Co, which do not form any network structure, like silicates. The lack of a network-forming multivalent bond is the probable reason why no stable mesoporous oxides have been synthesized for divalent elements yet. Here we have reported our attempt to synthesize porous oxides of Ni and Co. Octadecylamine has been used as the organic structure-directing agent. The product obtained was put under solvent extraction and calcination at various temperatures to remove the surfactant, followed by characterization using XRD, TEM and BET measurements. The FT/IR and thermal analyses (TGA and DSC) were also carried out for supporting information, such as extent of removal of surfactant from the pores of the metal oxide. A relatively better surface area has been obtained for the Co oxide, but in Ni the surface area found is not as good. A possible reason for that has been discussed. The porous (solvent extracted) cobalt oxide has been used as a catalyst in the oxidation reaction of cyclohexane in mild conditions. The catalyst has shown relatively better conversion of cyclohexane into cyclohexanone and cyclohexanol than the nanostructured cobalt oxide catalyst of regular structure.

Electrochemical synthesis, X-ray single crystal, IR spectroscopic, and quantum chemical investigation of molybdenum and tungsten hexamethoxides.

The anodic oxidation of molybdenum metal in MeOH at both low anodic and cathodic current density (0.025 A/cm2) and electrolyte temperatures kept below 20 degrees C provides an efficient approach to Mo(OMe)6 (I). W(OMe)6 (II) can be obtained from the electrolytes, prepared via anodic dissolution of tungsten, by fractional crystallization. The symmetrically independent units in the structures of I and II, being isomorphous, follow the C1 (slightly distorted D2d) symmetry. Theoretical calculations performed for a free molecule of I indicate that this low symmetry may be the result of the packing of the molecules in the crystal structure and also an inherent property imposed by the bonding in this compound. Crystal data for I: Mo(OMe)6 at 22 degrees C, a = 7.0976(13), b = 6.6103(12), and c = 12.286(2) A, beta = 90.068(3) degrees, V = 576.41(18) A3, monoclinic P2/n, Z = 2. Crystal data for II: W(OMe)6 at 22 degrees C, a = 7.1164(19), b = 6.6414(18), and c = 12.304(3) A, beta = 90.047(5) degrees, V = 581.5(3) A3, monoclinic P2/n, Z = 2.