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Agia Paraskevi, Greece

Vourdas N.,Technological Educational Institute of Sterea Ellada | Tserepi A.,Institute of Microelectronics, Greece | Stathopoulos V.N.,Technological Educational Institute of Sterea Ellada
Applied Physics Letters

We present a generic method to reversibly switch the mobility of a droplet after impingement onto a hydrophobic porous surface, from a sticky to a slippery state and back. By means of a pneumatic system, the backpressure of the porous medium is adjusted to favor the pressure balance towards the desired state. By applying overpressure above a certain threshold, the antiwetting pressures increase over the wetting pressures, which eventually results to a slippery state, while vacuum enhances the wetting pressures, thus, rendering the droplet sticky. This pressure-induced switching method is very flexible and can be applied even after decay of the hydrophobic character of the porous medium, does not entail the use of a superhydrophobic or hierarchical surface, and can be applied for actuation and valving in microfluidics. © 2013 AIP Publishing LLC. Source

Kokkinos C.,National and Kapodistrian University of Athens | Economou A.,National and Kapodistrian University of Athens | Raptis I.,Institute of Microelectronics, Greece
Analytica Chimica Acta

This work reports the fabrication of disposable three-electrode cells with integrated metal-film electrodes. The devices were fabricated by a multi-step micro-fabrication approach combining sputtering for the deposition of metals and the dielectric material (SiO 2) on the surface of a silicon wafer and photolithography for the definition of the geometry of the sensors. The working electrode was a microelectrode array consisting of bismuth microdisks while the reference and counter electrode strips were made of Ag and Pt, respectively. The utility of these devices was tested for the trace determination of Pb(II) and Cd(II) by anodic stripping voltammetry and Ni(II) by adsorptive stripping voltammetry. The detection of these trace metals was carried out in unstirred and undeoxygenated solutions exhibiting sub-μgL -1 limits of detection and enhanced analytical characteristics compared to conventional bismuth-film electrodes. © 2011 Elsevier B.V. Source

Polychronopoulou K.,University of Cyprus | Giannakopoulos K.,Institute of Materials Science | Giannakopoulos K.,Institute of Microelectronics, Greece | Efstathiou A.M.,University of Cyprus
Applied Catalysis B: Environmental

The present work is focused on the sol-gel synthesis, characterization and catalytic performance evaluation of novel Mg-Ce-Zr-O-based mixed oxides supported Rh catalysts for the purification of H 2-rich gas streams from phenol through steam reforming in the 575-730°C range. Phenol is used as a model compound of tars, the former being one of the main constituents of tars formed during steam gasification and pyrolysis of biomass. Novel Rh catalysts (0.1wt%) supported on Mg-Ce-Zr-O-based mixed oxides modified by alkaline-earth, rare earth, and transition metal ions, having the general formula Mg-Ce-Zr-X-O (where X stands for La, Sr, Ba, Ca and Zn) were systematically studied. The physicochemical properties of the catalysts were evaluated using complementary bulk and surface characterization techniques, such as BET, XPS, in situ XRD, TEM/SAED and SEM/EDX. Transient techniques including H 2-TPR, TPD-CO 2 and TPD-NH 3 were employed in order to characterize redox behavior, surface basicity, and surface acidity of support, respectively. Among the catalysts examined, a 0.1wt% Rh/40Mg-20Ce-20Zr-20La-O was found to exhibit the highest hydrogen product yield, specific H 2 production rate (μmol/m 2min), and the lowest CO/CO 2 product ratio (575-730°C), even when compared to a Ni-based commercial steam reforming of tars catalyst. At 655°C, a H 2 yield of ∼95% and a specific reaction rate of 100μmolH 2/m 2min were obtained for a feed containing 0.5vol% phenol and 40vol% H 2O at a gas hourly space velocity of ∼80,000h -1. This activity behavior is correlated with the largest concentration of basic sites and labile oxygen species (μmol/m 2), and also with the largest acid/base site ratio present in the 40Mg-20Ce-20Zr-20La-O support composition. Steam was also found to be an efficient reagent for the removal of carbonaceous deposits (e.g., C xH y) formed on the catalyst surface during phenol steam reforming. The H/C atom compositional ratio of the carbonaceous deposits was found to depend on reaction temperature. © 2011 Elsevier B.V. Source

Pasparakis G.,Foundation for Research and Technology Hellas | Manouras T.,Institute of Microelectronics, Greece | Argitis P.,Institute of Microelectronics, Greece | Vamvakaki M.,Foundation for Research and Technology Hellas | Vamvakaki M.,University of Crete
Macromolecular Rapid Communications

Photodegradable polymers constitute an emerging class of materials that finds numerous applications in biotechnology, biomedicine, and nanoscience. This article highlights some of the emerging applications of photodegradable polymers in the form of homopolymers, particles and self-assembled constructs in solution, hydrogels for tissue engineering, and photolabile polymers for biopatterning applications. Novel photochemistries have been combined with controlled polymerization methods, which result in well-defined photodegradable materials that exhibit light mediated and often controlled fragmentation processes. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Papanikolaou N.,Institute of Microelectronics, Greece | Psarobas I.E.,Institute of Microelectronics, Greece | Stefanou N.,National and Kapodistrian University of Athens
Applied Physics Letters

By means of full electrodynamic and elastodynamic multiple-scattering calculations we study the optical and acoustic properties of three-dimensional lattices of metallic nanospheres implanted in a dielectric host. Our results show that such structures exhibit omnidirectional spectral gaps for both telecom infrared light and hypersound, with relatively low absorptive losses. This class of dual (phoxonic) band-gap materials is an essential step toward the hypersonic modulation of light and could lead to the development of efficient acousto-optical devices. © 2010 American Institute of Physics. Source

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