Facile functionalization of lipid bilayer vesicles by titania: the use of cerasome-forming lipids for surface and core modification

Two kinds of functionalization of a lipid bilayer vesicle by titania were achieved by utilizing a cerasome-forming lipid, which is the starting material to prepare a cerasome, a morphologically stable lipid bilayer vesicle having an atomic layer of siloxane networks on its surface. One system is the preparation of the titania-coated cerasomes by immobilizing nanaometer-sizes of titania onto the surface siloxane network of cerasomes. The other is the creation of an asymmetric lipid bilayer structure on the surface of the colloidal titania particles. The characteristics of these surface- and core-functionalized vesicles were investigated, and it was found that these conjugates showed photocatalytic activity as evaluated by photolysis experiments of the cationic dye methylene blue.     

Enhancement of the biodegradability of model wastewater containing recalcitrant or inhibitory chemical compounds by photocatalytic pre-oxidation

m-Dinitrobenzene, diphenylamine and resorcinol, threearomatic compounds found inhibitory or recalcitrant tobiological treatments, were chosen as model chemicalsfor this study on the integration ofphotocatalytic-biological treatments. The degradationof each of these compounds was achieved by ultravioletphotocatalytic oxidation, leading to the formation ofintermediate compounds. The photocatalytic treatmentwas performed in a TiO₂ slurry reactor containingan aqueous solution of one of the three chemicals. Thebiodegradability of model wastewater treatedphotocatalytically was measured in terms ofBOD₁/TOC. Intermediate compounds that appeared atearly stages of the photocatalytic degradation ofm-dinitrobenzene or diphenylamine seemed to be moreinhibitory than the parent compounds but this was notthe case for resorcinol. A substantial improvement inBOD₁/TOC could be achieved, but it required themineralization of at least 80% of the organic carbonoriginally in the water. Microtox® toxicityresults confirmed the BOD₁/TOC trends fordiphenylamine.     

Seasonal variation in the properties of titania photocatalysts produced from Ti-salt flocculated bioresource sludge

Ti-salt flocculation of biologically treated sewage effluent (BTSE) was carried out on monthly basis during one year to trace the seasonal variation in the properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts. Titania photocatalysts were produced from incineration of Ti-salt flocculated sludge at 600 °C. The physio-chemical properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts were investigated. The photocatalytic activity of titania was examined using different substrates of rhodamine B and humic acid under UV light irradiation. Results indicated that the flocculation performance of Ti-salt was not affected by the seasonal variation of BTSE. BTSE characteristics resulted in marginal effect in titania characterisation and photocatalytic activity. Titania photocatalysts produced from Ti-salt flocculated sludge in different seasons showed constant anatase phase, high BET surface area and high photocatalytic activity.     

In-situ upgrading of biomass pyrolysis vapors: catalyst screening on a fixed bed reactor

In-situ catalytic upgrading of biomass fast pyrolysis vapors was performed in a fixed bed bench-scale reactor at 500 °C, for catalyst screening purposes. The catalytic materials tested include a commercial equilibrium FCC catalyst (E-cat), various commercial ZSM-5 formulations, magnesium oxide and alumina materials with varying specific surface areas, nickel monoxide, zirconia/titania, tetragonal zirconia, titania and silica alumina. The bio-oil was characterized measuring its water content, the carbon-hydrogen-oxygen (by difference) content and the chemical composition of its organic fraction. Each catalytic material displayed different catalytic effects. High surface area alumina catalysts displayed the highest selectivity towards hydrocarbons, yielding however low organic liquid products. Zirconia/titania exhibited good selectivity towards desired compounds, yielding higher organic liquid product than the alumina catalysts. The ZSM-5 formulation with the highest surface area displayed the most balanced performance having a moderate selectivity towards hydrocarbons, reducing undesirable compounds and producing organic liquid products at acceptable yields.     

Photocatalytic processes by polyoxometalates. Splitting of water. The role of dioxygen

Photolysis of polyoxometalates at the oxygen to metal charge transfer bands, at the near visible and UV areas, in the presence of a great variety of organic compounds, results in multielectron reduction of polyoxometalates and concomitant oxidation of organic compounds. In the absence of dioxygen, photolysis accumulates electrons on polyoxometalates, moving the redox potential to more negative values, until the reduced catalyst is able to deliver its electrons to H⁺. At this point, a steady state is produced at which the rate of photoreduction of polyoxometalate is matched by its rate of reoxidation by H⁺ (H₂-evolution). The presence of dioxygen has the following results: (a) It reoxidizes very fast and effectively and photoreduced polyoxometalate, accelerating the photocatalytic cycle by an order of magnitude, and (b) its activation by the reduced catalyst provides, usually, an extra step in which further oxidations of a variety of organic compounds have been obtained.     

Energy supply in early development of living cell

It is proposed that before light and oxidation of organic compounds became the predominant energy suppliers of the living cell, electron charge energy derived from heat energy by mineral particles, was the first energy source. The basis of this hypothesis is the finding that Al2O3 in electrolytic condensors can produce an electron driving force with a potential high enough for electrolysis of water and subsequent reduction of CO2 into organic molecules. This electron driving force is likely to originate from one-way movement of electrons in tunnel structures of the Al2O3 layer, driven by temperature kinetic energy.     

Demonstration of phosphates in calcium deposits: A modification of von Kossa's reaction

Summary It has been suggested that in von Kóss'as technic silver cations replace calcium bound to phosphate or carbonate groups and are then reduced to black metallic silver during exposure to light. However, in test tube experiments silver phosphate retains its yellow color for days. These differences between reactions of pure calcium phosphates and calcium deposits in tissues were emphasized already by von Kóssa; he regarded only the initial yellow coloration of calcium diagnostic for calcium phosphates and deplored the subsequent blackening caused by organic compounds. Von Kóssa's experiments were easily reproducible. A review of the literature showed that reduction of silver nitrate by organic compounds was well known in the 19th century. For histochemical studies of phosphates it was deemed desirable to avoid the formation of black by-products. Sections of paraffin-embedded human tissues were exposed to solutions of silver nitrate in subdued light or darkness and then treated with sodium thiosulfate. Silver phosphate was yellow to yellowish brown; other tissue structures remained colorless. No darkening was observed in sections stored for eight years. Other compounds which form yellow silver salts, e.g. iodides and periodates, are unlikely to occur in paraffin sections of human tissues.     

The effects of manganese doping on UVA absorption and free radical generation of micronised titanium dioxide and its consequences for the photostability of UVA absorbing organic sunscreen components.

The effect of manganese doping on the free radical generation rate, free radical scavenging and UVA absorption properties of micronised sunscreen grade titania has been studied with respect to enhancement of the UVA photostability of test sunscreen formulations containing the organic UVA absorber Parsol 1789. Manganese doping has been shown to increase the UVA:UVB absorption ratio of titania, reduce free radical generation rates by over 90%, and provide free radical scavenging behaviour. Adding manganese-doped titania to a test formulation incorporating Parsol 1789 shows that manganese doping increases UVA attenuation stability by up to 3 times the amount achieved by comparable commercial undoped titania materials. HPLC data shows this to be related to an improved stabilisation of the organic sunscreen components. Manganese doped titania shows improved efficacy over undoped titania in sunscreen formulations containing organic UV absorbers.     

Inhibitory effect of dissolved organic matter on triplet-induced oxidation of aquatic contaminants.

Excited triplet states of organic chromophores, in particular aromatic ketones, are capable of inducing oxidation of a variety of organic compounds. These reactions probably play an important role in the degradation of organic contaminants in sunlit natural waters. The effect of dissolved natural organic matter (DOM) on the oxidation rate of twenty-two aquatic organic contaminants, including phenols, anilines, phenylurea and s-triazine herbicides, and some pharmaceuticals, was investigated using photoexcited benzophenone-4-carboxylate (CBBP) as the oxidant. For about half of the studied compounds, a decrease in depletion rate was observed in the presence of Suwannee River fulvic acid, used as a reference DOM. Also, depletion rates decreased with increasing DOM concentration, as verified for five selected compounds. Such an inhibitory effect of DOM on oxidation is attributed to its antioxidant properties, whereby oxidation intermediates of the contaminants are supposed to be reduced back to their parent compounds. The presented screening study shows that DOM may be a relevant factor for inhibiting the oxidation of many organic contaminants in surface waters and possibly in engineered water treatment systems.     

The use of nanoscale visible light-responsive photocatalyst TiO2-Pt for the elimination of soil-borne pathogens

Exposure to the soil-borne pathogens Burkholderia pseudomallei and Burkholderia cenocepacia can lead to severe infections and even mortality. These pathogens exhibit a high resistance to antibiotic treatments. In addition, no licensed vaccine is currently available. A nanoscale platinum-containing titania photocatalyst (TiO(2)-Pt) has been shown to have a superior visible light-responsive photocatalytic ability to degrade chemical contaminants like nitrogen oxides. The antibacterial activity of the catalyst and its potential use in soil pathogen control were evaluated. Using the plating method, we found that TiO(2)-Pt exerts superior antibacterial performance against Escherichia coli compared to other commercially available and laboratory prepared ultraviolet/visible light-responsive titania photocatalysts. TiO(2)-Pt-mediated photocatalysis also affectively eliminates the soil-borne bacteria B. pseudomallei and B. cenocepacia. An air pouch infection mouse model further revealed that TiO(2)-Pt-mediated photocatalysis could reduce the pathogenicity of both strains of bacteria. Unexpectedly, water containing up to 10% w/v dissolved soil particles did not reduce the antibacterial potency of TiO(2)-Pt, suggesting that the TiO(2)-Pt photocatalyst is suitable for use in soil-contaminated environments. The TiO(2)-Pt photocatalyst exerted superior antibacterial activity against a broad spectrum of human pathogens, including B. pseudomallei and B. cenocepacia. Soil particles (<10% w/v) did not significantly reduce the antibacterial activity of TiO(2)-Pt in water. These findings suggest that the TiO(2)-Pt photocatalyst may have potential applications in the development of bactericides for soil-borne pathogens.     

Silver nanoparticles: partial oxidation and antibacterial activities

The physical and chemical properties of silver nanoparticles that are responsible for their antimicrobial activities have been studied with spherical silver nanoparticles (average diameter approximately 9 nm) synthesized by the borohydride reduction of Ag+ ions, in relation to their sensitivity to oxidation, activities towards silver-resistant bacteria, size-dependent activities, and dispersal in electrolytic solutions. Partially (surface) oxidized silver nanoparticles have antibacterial activities, but zero-valent nanoparticles do not. The levels of chemisorbed Ag+ that form on the particle's surface, as revealed by changes in the surface plasmon resonance absorption during oxidation and reduction, correlate well with the observed antibacterial activities. Silver nanoparticles, like Ag+ in the form of AgNO3 solution, are tolerated by the bacteria strains resistant to Ag+. The antibacterial activities of silver nanoparticles are related to their size, with the smaller particles having higher activities on the basis of equivalent silver mass content. The silver nanoparticles aggregate in media with a high electrolyte content, resulting in a loss of antibacterial activities. However, complexation with albumin can stabilize the silver nanoparticles against aggregation, leading to a retention of the antibacterial activities. Taken together, the results show that the antibacterial activities of silver nanoparticles are dependent on chemisorbed Ag+, which is readily formed owing to extreme sensitivity to oxygen. The antibacterial activities of silver nanoparticles are dependent on optimally displayed oxidized surfaces, which are present in well-dispersed suspensions.     

microAg particle-based molecular sensing/recognition via surface-enhanced Raman spectroscopy

In this study, we demonstrate that powders of commercially available 2-microm-sized Ag (microAg) can be used as a core material for constructing molecular sensing/recognition units operating via surface-enhanced Raman scattering (SERS). This is possible because microAg powders are very efficient substrates for both the infrared and Raman-spectroscopic characterization of molecular adsorbates prepared in a similar manner on silver surfaces. The Raman spectrum of organic monolayers on powdered silver is a SERS spectrum. The agglomeration of microAg particles in a highly concentrated buffer solution could be prevented by the deposition of polar molecules like 1,4-phenylenediisocyanide (1,4-PDI), and mixed self-assembled monolayers of 1,4-PDI and N-(+)-biotinyl-6-aminocaproic acid on microAg particles were then confirmed via the SERS of 1,4-PDI to selectively recognize the avidin arrays formed on a separate biotinylated substrate. According to a dose response curve, avidin at >10(-6)g/mL could be easily identified by the present method. In addition, the non-specific adsorption of microAg particles was found to be negligibly small, probably because the Ag particles were too heavy to be retained on organic substrates solely by non-specific interaction.     

Inhibition of growth, iron, and sulfur oxidation in Thiobacillus ferrooxidans by simple organic compounds.

Iron and sulfur oxidation by Thiobacillus ferrooxidans as well as growth on ferrous iron were inhibited by a variety of low molecular weight organic compounds. The influences of chemical structure of the organic inhibitors, pH, temperature, physical treatment of cells, and added inhibitory or stimulatory inorganic ions and iron oxidation suggest that a major factor contributing to the inhibitory effects on iron oxidation is the relative electronegativity of the organic molecule. The data also suggest that inhibitory organic compounds may (i) directly affect the iron-oxidizing enzyme system, (ii) react abiologically with ferrous iron outside the cell, (iii) interfere with the roles of phosphate and sulfate in iron oxidation, and (iv) nonselectively disrupt the cell envelope or membrane.     

An integrated MBR-TiO2 photocatalysis process for the removal of Carbamazepine from simulated pharmaceutical industrial effluent

This paper aims to demonstrate that integrating biological process and photocatalytic oxidation in a system operated in recycling mode can be a promising technology to treat pharmaceutical wastewater characterized by simultaneous presence of biodegradable and refractory/inhibitory compounds. A lab-scale system integrating a membrane bioreactor (MBR) and a TiO₂ slurry photoreactor was fed on simulated wastewater containing 10 mg/L of the refractory drug Carbamazepine (CBZ). Majority of chemical oxygen demand (COD) was removed by the MBR, while the photocatalytic oxidation was capable to degrade CBZ. CBZ degradation kinetics and its impacts on the biological process were studied. The adoption of a recycling ratio of 4:1 resulted in removal of up to 95% of CBZ. Effluent COD reduction, sludge yield increase and respirometric tests suggested that the oxidation products were mostly biodegradable and not inhibiting the microbial activity. These results evidenced the advantages of the proposed approach for treating pharmaceutical wastewater and similar industrial effluents.     

Enhanced chemiluminescence of the luminol–AgNO3 system by Ag nanoparticles

The oxidation reaction of luminol with AgNO₃ can produce chemiluminescence (CL) in the presence of silver nanoparticles (NPs) in alkaline solution. Based on the studies of UV‐vis absorption spectra, photoluminescence (PL) spectra and CL spectra, a CL enhancement mechanism is proposed. The CL emission spectrum of the luminol–AgNO₃–Ag NPs system indicated that the luminophore was still 3‐aminophthalate. On injection of silver nanoparticles into the mixture of luminol and AgNO₃, they catalysed the reduction of AgNO₃ by luminol. The product luminol radicals reacted with the dissolved oxygen, to produce a strong CL emission. As a result, the CL intensity was substantially increased. Moreover, the influences of 18 amino acids, e.g. cystine, tyrosine and asparagine, and 25 organic compounds, including gallic acid, tannic acid and hydroquinone, on the luminol–AgNO₃–Ag NPs CL system were studied by a flow‐injection procedure, which led to an effective method for detecting these compounds. Copyright © 2011 John Wiley & Sons, Ltd.     

Stimulation of larval emergence in Heterodera schachtii Schmidt, by certain concentrations of silver compounds

Certain dilute solutions of organic silver compounds, e.g. 0.001% silver proteinate, acting for a short time on cysts of the potato strain of Heterodera schachtii , cause increased numbers of larvae to emerge from the cysts when the latter are transferred to potato root excretion. More prolonged exposure of cysts to these solutions tends to result in a toxic effect which is also produced by more concentrated solutions. It is concluded that many more eggs in H. schachtii cysts are mature and capable of hatching than can be accounted for by ordinary larval liberation brought about by means of root excretion alone. Increasing periods of pre-treatment of cysts in tap water tend to produce increases in larval emergence, although this stimulation is probably of a different type from that given by silver compounds.     

Ultrastructural autometallography: a method for silver amplification of catalytic metals

The autometallographic technique involves application of a silver bromide-containing emulsion on the surface of ultrathin sections placed on grids that are subsequently exposed to a photographic developer. In tissue sections from animals treated intravitally with gold, silver, or mercury compounds, accumulations of the metals are visualized by autometallography and can be used for quantitative studies. After amplification, sections can be stained with lead citrate and uranyl acetate. Using autometallography, particles of colloidal gold dispersed in a film of gelatin showed a time-dependent growth and were gradually amplified up to 3.5-fold after 15 min of development. Hence the method may prove useful tracing colloidal gold particles in sections with low particle density, and be a powerful tool for revealing metals in biological tissues.     

Biological oxidation of thianthrene,thioxanthene and dibenzothiophene by the thermophilic organismSulfolobus acidocaldarius

Summary Microbial oxidation of some model aromatic organic sulfur compounds such as thianthrene, thioxanthene and dibenzothiophene by the thermophilic organismSulfolobus acidocaldarius has been studied. Sulfate ions released as an oxidation product were measured to quantify the oxidations. The oxidation of the aforementioned refractory aromatic sulfur compounds byS. acidocaldarius may have applications in organic sulfur removal from hydrocarbon fuels such as coal and oil.     

One carbon metabolism in SAR11 pelagic marine bacteria

The SAR11 Alphaproteobacteria are the most abundant heterotrophs in the oceans and are believed to play a major role in mineralizing marine dissolved organic carbon. Their genomes are among the smallest known for free-living heterotrophic cells, raising questions about how they successfully utilize complex organic matter with a limited metabolic repertoire. Here we show that conserved genes in SAR11 subgroup Ia (Candidatus Pelagibacter ubique) genomes encode pathways for the oxidation of a variety of one-carbon compounds and methyl functional groups from methylated compounds. These pathways were predicted to produce energy by tetrahydrofolate (THF)-mediated oxidation, but not to support the net assimilation of biomass from C1 compounds. Measurements of cellular ATP content and the oxidation of (14)C-labeled compounds to (14)CO(2) indicated that methanol, formaldehyde, methylamine, and methyl groups from glycine betaine (GBT), trimethylamine (TMA), trimethylamine N-oxide (TMAO), and dimethylsulfoniopropionate (DMSP) were oxidized by axenic cultures of the SAR11 strain Ca. P. ubique HTCC1062. Analyses of metagenomic data showed that genes for C1 metabolism occur at a high frequency in natural SAR11 populations. In short term incubations, natural communities of Sargasso Sea microbial plankton expressed a potential for the oxidation of (14)C-labeled formate, formaldehyde, methanol and TMAO that was similar to cultured SAR11 cells and, like cultured SAR11 cells, incorporated a much larger percentage of pyruvate and glucose (27-35%) than of C1 compounds (2-6%) into biomass. Collectively, these genomic, cellular and environmental data show a surprising capacity for demethylation and C1 oxidation in SAR11 cultures and in natural microbial communities dominated by SAR11, and support the conclusion that C1 oxidation might be a significant conduit by which dissolved organic carbon is recycled to CO(2) in the upper ocean.     

Cupric Oxide (CuO) Oxidation Detects Pyrogenic Carbon in Burnt Organic Matter and Soils

Wildfire greatly impacts the composition and quantity of organic carbon stocks within watersheds. Most methods used to measure the contributions of fire altered organic carbon–i.e. pyrogenic organic carbon (Py-OC) in natural samples are designed to quantify specific fractions such as black carbon or polyaromatic hydrocarbons. In contrast, the CuO oxidation procedure yields a variety of products derived from a variety of precursors, including both unaltered and thermally altered sources. Here, we test whether or not the benzene carboxylic acid and hydroxy benzoic acid (BCA) products obtained by CuO oxidation provide a robust indicator of Py-OC and compare them to non-Py-OC biomarkers of lignin. O and A horizons from microcosms were burned in the laboratory at varying levels of fire severity and subsequently incubated for 6 months. All soils were analyzed for total OC and N and were analyzed by CuO oxidation. All BCAs appeared to be preserved or created to some degree during burning while lignin phenols appeared to be altered or destroyed to varying extents dependent on fire severity. We found two specific CuO oxidation products, o-hydroxybenzoic acid (oBd) and 1,2,4-benzenetricarboxylic acid (BTC2) that responded strongly to burn severity and withstood degradation during post-burning microbial incubations. Interestingly, we found that benzene di- and tricarboxylic acids (BDC and BTC, respectively) were much more reactive than vanillyl phenols during the incubation as a possible result of physical protection of vanillyl phenols in the interior of char particles or CuO oxidation derived BCAs originating from biologically available classes of Py-OC. We found that the ability of these compounds to predict relative Py-OC content in burned samples improved when normalized by their respective BCA class (i.e. benzene monocarboxylic acids (BA) and BTC, respectively) and when BTC was normalized to total lignin yields (BTC:Lig). The major trends in BCAs imparted by burning persisted through a 6 month incubation suggesting that fire severity had first order control on BCA and lignin composition. Using original and published BCA data from soils, sediments, char, and interfering compounds we found that BTC:Lig and BTC2:BTC were able to distinguish Py-OC from compounds such as humic materials, tannins, etc. The BCAs released by the CuO oxidation procedure increase the functionality of this method in order to examine the relative contribution of Py-OC in geochemical samples.