Performance and characterization of Ag-cotton and Ag/TiO2 loaded textiles during the abatement of E. coli

The bacterial inactivation of Escherichia coli on Ag–cotton textiles were investigated under different experimental conditions with novel Ag-nanoparticles fixed on cotton textiles. The evaluation of the bactericide performance of the Ag–cotton was compared with the one observed for Ag–TiO2–cotton loaded textiles. The procedure used allowed us to prepare highly dispersed Ag-cluster species, 2–4 nm in size, as observed by transmission electron microscopy (TEM). By depth profile analysis, the X-ray photoelectron spectroscopy (XPS) revealed that the Ag profile in the 15 topmost layers remained almost constant before and after E. coli inactivation. The cotton loading was fairly low and of the order of 0.10 wt.% Ag/wt. of cotton. By infrared spectroscopy no modification of the Ag–cotton could be detected before or after E. coli inactivation due to the small absorption coefficient of Ag and the very low metal loading of Ag on the cotton. The E. coli was completely abated on Ag–cotton textiles immediately after the contact took place, due to the strong bacteriostatic effect of the dispersed silver clusters on the cotton surface.

Combinatorial High-Vacuum Chemical Vapor Deposition of Textured Hafnium-Doped Lithium Niobate Thin Films on Sapphire

Giacomo Benvenuti, Ali Dabirian, Scott Harada, Patrik Hoffmann, Yury Kuzminykh, Paul Muralt, Silviu Cosmin Sandu, Estelle Wagner

Combinatorial high-vacuum chemical vapor deposition (HV-CVD) was used to identify the conditions required to obtain hafnium-doped lithium niobate thin films on sapphire {001} substrates. Niobium tetraethoxydimethylaminoethoxide (Nb(OEt)(4)(dmae)), lithium tert-butoxide (Li(OBut)), and hafnium tert-butoxide (Hf(OBut)(4)) were used as precursors. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that a single phase of textured {001} Hf-doped lithium niobate film was obtained under certain precursor flux conditions. The lithium content ([Li]/([Li] + [Nb])) of the textured film was estimated using Raman spectroscopy to be about 49 mol %. The presence of hafnium inside the films was confirmed by X-ray photoelectron spectroscopy (XPS) measurements, and the hafnium content of the textured film ([Hf]/([Hf] + [Nb])) was estimated to be about 3 mol %. XPS data confirmed that Hf and Nb, respectively, are in the +4 and +5 oxidation states inside the film. The film consists of nearly parallel {001} hafnium-doped lithium niobate columns with different in-plane orientations.

2011

Effect of fuels on combustion synthesis of TiO2 - Towards efficient photocatalysts for methylene blue oxidation and Cr (VI) reduction under natural sunlight

Nicolas Xanthopoulos

A facile synthesis of carbon and nitrogen co-doped nano-TiO2 with pure anatase phase and high surface area was achieved by using combustion synthesis without the need of surfactants in a single step approach. Organic fuels such as hexamine, triethyl amine and glycine were tested as different fuels with titanylnitrate as the common oxidant. Effect of mixture of fuels has also been studied by taking the combinations of the above mentioned fuels. X-ray diffraction confirms the anatase phase titania and nano-crystalline size of the prepared catalysts was confirmed by transmission electron microscopy (TEM). N-2 adsorption confirmed the high surface area of nanocrystalline titania. Red shifts in UV-Vis absorption spectra was assigned due to the C and N-doping into the TiO2 matrix, whereas the presence of C and N in the TiO2 matrix was confirmed by X-ray photoelectron spectroscopy. Photocatalytic activity of the catalysts has been estimated from the oxidation of methylene blue (MB) and reduction of Cr (VI) under natural sunlight in open atmosphere. Among the TiO2 catalysts prepared, the one obtained with glycine as the fuel showed the best photocatalytic activity, which was correlated to the number of moles of gases evolved during the synthesis. (C) 2013 Elsevier B.V. All rights reserved.

Elsevier Science Sa2013

Selective solar absorber coatings on receiver tubes for CSP - energy-efficient production process by sol-gel dip-coating and subsequent induction heating

Yannik Antonetti, Thomas Gascou, Aïcha Hessler-Wyser, Martin Joly, Martin Python, Jean-Louis Scartezzini, Andreas Schueler

The energy efficiency of production processes for components of solar energy systems is an important issue. Other factors, which are important for the production of black selective solar coatings include production speed, cycle time and homogeneity of the coating, as well as the minimization of the quantity of the needed chemical precursors. In this paper a new energy-efficient low-cost production process is presented for production of optically selective coatings for solar thermal absorbers. The used method to produce such coatings is sol-gel dip-coating for which all the solutions have been synthetized at the Solar Energy and Building Physics Laboratory of EPFL. The used precursors are tetraethyl orthosilicate, manganese acetate tetrahydrate, copper chloride dihydrate and cobalt chloride hexahydrate. Solutions were obtained by dissolving these precursors in a solution based on a mixture of absolute ethanol, nitric acid and demineralized water. The layers deposited on sheetlike substrates were annealed in a benchtop furnace. For 2 meter long austenitic stainless steel tubes, a novel, fast and energy-efficient process based on induction heating was developed for the thermal annealing. An induction coil passes along the tube. An alternating current flowing in the coil induces a current in the tube. By resistive heating, the temperature of both the metallic tube wall and the deposited film increases. The homogeneity of the temperature distribution of the tube after a single passage of the coil was monitored by infrared imaging. The optical and morphological properties of the Cu-Co-Mn-Si-0 based triple layer have been characterized by spectrophotometry, transmission electron microscopy (TEM), time-of-flight secondary ion mass spectroscopy (ToFSIMS) and X-ray photoelectron spectroscopy (XPS). After optimization of the multilayer design, a solar absorptance of 0.95 and a thermal emissivity of 0.12 at 100 C have been achieved. The intermediate Cu-Co-Mn-Si-0 layer was analyzed by transmission electron microscopy. The likewise obtained images show an agglomeration of crystalline grains with 5-20 nm in diameter. Therefore, we can consider that the Cu-Co-Mn-Si-0 phase is nanocrystalline. In order to roughly estimate the corrosion resistance of the coating in an acidic environment, a simple corrosion test in harsh conditions confirmed the durability of the novel sol-gel coating. Moreover, the excellent stability at elevated temperatures in ambient air makes the coating an interesting candidate for solar applications involving concentrated solar radiation, such as the generation of solar electricity (concentrated solar power), industrial process heating and solar cooling. For that reason, prototype coatings consisting of stacks of three individual layers were deposited on 2 meter long stainless steel tubes. (C) 2014 Published by Elsevier Ltd.

Elsevier Science Bv2014

Selective solar absorber coatings on receiver tubes for CSP - energy-efficient production process by sol-gel dip-coating and subsequent induction heating

Yannik Antonetti, Thomas Gascou, Aïcha Hessler-Wyser, Martin Joly, Martin Python, Jean-Louis Scartezzini, Andreas Schueler

Elsevier Science Bv2014