Panagiotis Lianos

Effect of alcohol on the properties of micellar systems: I. Critical micellization concentration, micelle molecular weight and ionization degree, and solubility of alcohols in micellar solutions

Additions of alcohols of medium chain length (butanol to hexanol) to micellar solutions result in a decrease of critical micelle concentration and micelle molecular weight, and an increase of the micelle ionization degree. Moreover, the micelle molecular weight (or surfactant aggregation number) at a given alcohol concentration increases with the surfactant concentration and may reach values larger than in the absence of alcohol. Striking differences have been found in the changes of molecular weight of TTAB micelles in H/sub 2/O-pentanol mixtures in the presence of 0.1 M KBr and in the absence of salt. These various results have been explained by considering the effect of the micelle solubilized alcohol on the micelle surface charge density and on the dielectric constant of the palisade layer. 48 references.

Production of electricity and hydrogen by photocatalytic degradation of organic wastes in a photoelectrochemical cell: The concept of the Photofuelcell: A review of a re-emerging research field

The present review aims to give to a researcher who has no experience with Photofuelcells all necessary basic knowledge to join the field without much trouble and to give to an experienced researcher a handy manual of reference. The author has dealt with the principal matters related with the design of a photoelectrochemical cell and the factors that affect efficient production of electricity by photocatalytic degradation of (principally) organic and (secondarily) inorganic waste materials. A large portion of the paper is devoted to the review of materials used for making a photoanode since most of the accomplished research is on this exact matter. The paper also briefly reviews the materials used to make the rest of the components of the cell as well as the models of cell efficiency and photodegradation procedures during cell operation.

Solar light-responsive Pt/CdS/TiO2 photocatalysts for hydrogen production and simultaneous degradation of inorganic or organic sacrificial agents in wastewater.

Photocatalytic degradation of waste material in aqueous solutions and simultaneous production of hydrogen was studied with the double purpose of environmental remediation and renewable energy production. Both powdered and immobilized Pt/CdS/TiO(2) photocatalysts were used to oxidize model inorganic (S(2-)/SO(3)(2-)) and organic (ethanol) sacrificial agents/pollutants in water. Powdered Pt/CdS/TiO(2) photocatalysts of variable CdS content (0-100%) were synthesized by precipitation of CdS nanoparticles on TiO(2) (Degussa P25) followed by deposition of Pt (0.5 wt %) and were characterized with BET, XRD, and DRS. Immobilized photocatalysts were deposited either on plain glass slides or on transparent conductive fluorine-doped SnO(2) electrodes. The results show that it is possible to produce hydrogen efficiently (20% quantum efficiency at 470 nm) by using simulated solar light and by photocatalytically consuming either inorganic or organic substances. CdS-rich photocatalysts are more efficient for the photodegradation of inorganics, while TiO(2)-rich materials are more effective for the photodegradation of organic substances.

A High-Performance Solid-State Dye-Sensitized Photoelectrochemical Cell Employing a Nanocomposite Gel Electrolyte Made by the Sol-Gel Route**

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Perovskite solar cell with low cost Cu-phthalocyanine as hole transporting material

Low cost copper phthalocyanine has been used as hole-transporting material for the construction of organolead halide solid state perovskite solar cells. The cells were assembled and tested under ambient conditions. They achieved a power conversion efficiency of 5.0% using copper phthalocyanine, which appears to have potential to replace the currently used organic hole transporters. The present work has also examined the possibility of upscaling by construction of small cell modules.

Titanium dioxide films made from reverse micelles and their use for the photocatalytic degradation of adsorbed dyes

Abstract Titanium dioxide mesoporous films have been deposited on glass slides by dip-coating in reverse micellar gels containing titanium isopropoxide. Reverse micelles were first made in cyclohexane, and the alkoxide was added last. Hydrolysis and inorganic polymerization produced composite organic/inorganic gels that were deposited on glass slides giving uniform transparent films. Calcination at 450°C gave TiO 2 nanoparticle mesoporous films. The films possessed a high capacity for adsorption of several different dyes from aqueous or alcoholic solutions. Illumination of the colored films by visible light led to a rapid degradation of the adsorbed dyes. The phenomenon is explained by a photosensitisation process involving the semiconductor and the adsorbed dye itself [N. Chouhaid, K. Vinodgopal, L. Fisher, S. Hotchandani, A.K. Chattopadhyay, P. Kamat, J. Phys. Chem. 100 (1996) 8436]. The differences between films made by varying some parameters are discussed.

Chapter 8 TiO2-Based Advanced Oxidation Nanotechnologies for Water Purification and Reuse

Abstract Advanced oxidation technologies (AOTs) produce highly reactive radical species, which readily attack and decompose organic pollutants in water eventually mineralizing them to water, carbon dioxide, and other simple inorganic species. AOTs involve nonselective oxidizing species and are among the most efficient chemical oxidation processes for the treatment of water contaminated with biologically toxic and nondegradable chemicals. Among such technologies, TiO 2 photocatalysis has attracted great attention for the development of efficient water purification and reuse systems due to the effectiveness of TiO 2 to generate the highly oxidizing hydroxyl radicals in the absence of any externally added chemicals in the system. In this chapter, we provide an overview of TiO 2 -based AOTs; from fundamentals to environmental applications. The mechanism of radical generation from TiO 2 /UV systems, principle of photocatalytic water purification, and applications of TiO 2 photocatalysis are described. The chapter also deals with some challenging issues in TiO 2 -based AOTs, including the need for enhancement of photocatalytic activity, challenges in reactor design with immobilized TiO 2 , the concept and multifunction of photocatalytic membranes, aspects on solar energy-based TiO 2 photocatalysis, and catalyst deactivation and fouling problems. Current advances in the technology such as tailor-design of TiO 2 materials at the nanoscale and simultaneous generation of hydroxyl radicals and sulfate radicals are of high interest and are also discussed. Finally, previous and current efforts, point to further development of TiO 2 -based AOTs, and more growth as a competitive process for full-scale applications in the near future are described in the end of this chapter.

Electroluminescence by a Sm3+-diketonate-phenanthroline complex

Abstract An organic light emitting diode (OLED) emitting reddish-orange light has been constructed using a Sm 3+ complex, composed of 4,4,4-trifluoro-1-phenyl-1,3-butanedione and 1,10-phenanthroline, as emitting layer and poly(vinylcarbazole) (PVK) and 2-(4-biphenylyl)-5-(4- tert -butylphenyl)-1,3,4-oxadiazole (PBD) as hole and electron transporters, respectively. Photoluminescence (PL) spectra suggest that energy pumping is made through both Sm 3+ -complexed ligands and poly(vinylcarbazole) providing an efficient electroluminescent system.

Preparation of thin Ureasil films with strong photoluminescence based on incorporated europium–thenoyltrifluoroacetone–bipyridine complexes

Abstract The photoluminescence (PL) of europium ions in the presence of the β-diketonate ligand thenoyltrifluoroacetone and 2,2′-bipyridine has been studied in poly(ethylene glycol)-200 solutions and in thin films made of Ureasil gels obtained through the sol–gel method. Films emit intense red PL, comparable to that of the laser dye rhodamine, by Near-UV excitation through energy transfer from the organic ligands to europium. Ureasils themselves take part in the energy transfer process.

Subphthalocyanine as hole transporting material for perovskite solar cells

Non planar 14-π aromatic subphthalocyanine has been introduced for the first time as hole transporting material for organometal halide perovskite solar cells and achieved a power conversion efficiency of 6.6%. Cells stored in the dark under ambient conditions underwent an incubation period of nine days during which, we observed an increase in efficiency followed by slow progressive deterioration. However, Raman spectral analysis of pristine perovskite deposited on titania revealed a much faster degradation thus indicating that the subphthalocyanine layer provides a temporary protection to the underlying perovskite layer.