1,721,190 research outputs found
Un approccio di disinfezione aspecifico che mima il sistema immunitario dei vertebrati
No full textIl sistema di difesa del nostro organismo si basa sostanzialmente sull’attività dei leucociti (neutrofili, macrofagi): le cellule estranee vengono dapprima fagocitate e poi distrutte grazie all’azione dell’acido ipocloroso (HOCl), un agente biocida prodotto da un enzima, la mieloperossidasi (MPO), a partire da perossido d’idrogeno e ioni cloruro, durante la cosiddetta esplosione ossidativa (respiratory burst).
Il ricorso a tecnologie elettrochimiche avanzate consente di mimare la natura, portando alla sintesi dell’acido ipocloroso, un principio attivo non tossico, non corrosivo e non pericoloso, che può essere utilizzato in numerose applicazioni: dalla disinfezione dell’acqua potabile, all’eliminazione dei microorganismi presenti nelle reti idriche, alla disinfezione di superfici ed ambienti (quest’ultima applicazione richiede la dispersione del principio attivo mediante nebulizzazione).
Il presente contributo esamina le peculiarità del processo di disinfezione, ponendo l’accento sull’azione ossidante dell’acido ipocloroso nei confronti dei diversi substrati e fornendo altresì indicazioni sulle modalità più idonee per la sintesi del biocida. Tra le varie applicazioni possibili, la protezione della produzione ortofrutticola (con trattamenti pre- e post-raccolta) e la zootecnia costituiscono settori nei quali l’utilizzo di tecnologie sostenibili è quanto mai desiderabile
The bromine electrode Part III: reaction kinetics at highly boron-doped diamond electrodes
No full textBromide oxidation and bromine reduction were investigated at boron-doped diamond (BDD) electrodes, in acidic media. Both the anodic and the cathodic reactions of the bromine redox couple were found to take place through a mechanism in which the Volmer step is rate-determining, as a result of a very poor stabilization of intermediate radical species. Accordingly, exchange current densities at BDD and polycrystalline Pt differ by more than five orders of magnitude. Finally, from the analysis of CV data, estimations of the anodic and cathodic transfer coefficients, as well as of heterogeneous rate constants, were obtained
Synthesis of diamond
No full textDiamond is impressive because of its wide range of extreme properties. By most measures, diamond is 'the biggest and best': it is the hardest known material, has the lowest coefficient of thermal expansion, is chemically inert and wear resistant, offers low friction, has high thermal conductivity, and is electrically insulating and optically transparent from the ultraviolet to the far infrared. Diamond already finds use in many different applications including, of course, its use as a precious gem, but also as a heat sink, as an abrasive, and as inserts and/or wear-resistant coatings for cutting tools. Obviously, it is possible to envisage many other potential applications for diamond as an engineering material, but progress in implementing many such ideas has been hampered by the comparative scarcity of natural diamond. This paper reports on the progress of the long running quest for ways to synthesize diamond in the laboratory
Electrochemical reactions at conductive diamond electrodes
No full textThe preparation of synthetic, highly conductive, diamond thin films has been achieved by different research groups from the end of the Eighties. Different papers appeared, together with many patents (relating both on semi-conducting and insulating films); however, a number of questions remains still open. In order to further elucidate this topic, highly boron-doped diamond (BDD) electrodes have been studied, both physically and by means of electrochemical investigations.
This thesis work starts with a brief introduction on diamond, from a mineralogical as well as a jeweler point of view (chapter one). Chapter two deals with the synthesis of diamond: both the HP-HT (high pressure, high temperature) and the CVD (chemical vapor deposition) method of preparation have been reviewed and thoroughly discussed [1]. The electric / electronic properties of BDD are summarized in chapter three; although a lot of work has been reported on semi-conducting diamond thin films, little is known about the highly-doped material. Chapter four concerns with the BDD physical characterization, illustrating the most commonly adopted techniques; in particular, a non-exhaustive collection of papers, dealing with X-ray Photoelectron Spectroscopy, is reported and briefly evaluated. Starting with chapter five, original results are reported, relating to BDD films synthesized at CSEM (Neuchâtel, Switzerland); firstly, the properties of the material has been investigated through SEM, AFM, XRD, Raman, XPS and CV analyses. The behavior of some simple electron transfer reactions (ironIII/ironII [2], ferri/ferro-cyanide [2], ceriumIV/ ceriumIII [3] and europiumIII/ europiumII) has been investigated, and results are reported in chapter six. Extending the investigation on multi step electrode processes, chapter seven contains data on the chlorine evolution reaction (chl.e.r.) at BDD [4]. Finally, chapter eight takes profit of the unique chemical and electrochemical stability of conductive diamond, reporting data on modified BDD films: physical and electrochemical characterizations of noble-metal oxide nanoparticles are described, together with the discussion of a radical-spillover mechanism possibly occurring, during the chl.e.r., at slightly modified BDD films [5-7].
[1] S. Ferro, “Synthesis of Diamond”, Journal of Materials Chemistry, Accepted for publication.
[2] S. Ferro and A. De Battisti, “Electron Transfer Reactions at Conductive Diamond Electrodes”, Electrochimica Acta, 47 (10), 1637-1645 (2002).
[3] S. Ferro and A. De Battisti, “Electrochemistry of the aqueous Ceric/Cerous redox couple at conductive diamond and gold electrodes”, Physical Chemistry Chemical Physics, 4 (10), 1915-1920 (2002).
[4] S. Ferro, A. De Battisti, I. Duo, Ch. Comninellis, W. Haenni and A. Perret, “Chlorine evolution at highly boron-doped diamond electrodes”, Journal of the Electrochemical Society, 147 (7), 2614-2619 (2000).
[5] A. De Battisti, S. Ferro and M. Dal Colle, “Electrocatalysis at conductive diamond modified by noble-metal oxides”, Journal of Physical Chemistry B, 105 (9), 1679-1682 (2001).
[6] S. Ferro and A. De Battisti, “Electrocatalysis and chlorine evolution reaction at ruthenium dioxide deposited on conductive diamond”, Journal of Physical Chemistry B, 106 (9), 2249-2254 (2002).
[7] Duo, S. Ferro, A. De Battisti and Ch. Comninellis, “Conductive Metal-Oxide nanoparticles on synthetic boron-doped diamond surfaces”, in “Catalysis of Nanoparticles Surfaces”; A. Wieckowski, E. R. Savinova and C. G. Vayenas Eds.; Marcel Dekker, Inc.; Projected publication date: 2002 (in press)
Electrochemical activated solutions
No full textThe presence of microorganisms is often cause of concerns; in water systems, it can lead to disease transmission (e.g., Legionnaires’ disease), in addition to the risk of bacterially induced corrosion, and to inefficient heat transfer due to coating of surfaces with heavy microbial growth (biofilm). The former problem mentioned is of particular concern when the water is intended for human consumption
Removal of Nitrates from industrial wastewater
No full textNitrates in water result mainly from the organic pollution caused by urban agglomerations. However, other important nitrate-sources are fertilizers used in agriculture, discharges from certain industries, as well as some combustion processes. Typically, wastewater undergoes a complex series of mechanical, physical, chemical and biological treatments, which point at the elimination of pollutants for the subsequent restitution of purified water to the environment or for reutilization. While anions that form insoluble compounds are removable by precipitation, nitrates are water-soluble and their abatement from aqueous media requires specific approaches.
Obviously, among the existing solutions, those that do not involve the production of additional waste materials should be preferred
Physicochemical and Electrical Properties of Praseodymium Oxides
Full text linkThe industrial research is continuously looking for novelties that could improve the applied processes, increasing the yields, lowering the costs, or improving the performances. In industrial electrochemistry, one more aspect is the stability of electrode materials, which is generally balanced by the catalytic activity: the higher the latter, the lower the former. A compromise has to be found, and an optimization is often the result of new ideas that completely change the way of thinking. Praseodymium-oxide-based cathodes have been proved to be quite interesting devices: the hydrogen evolution reaction is guaranteed by the presence of a noble metal (platinum and/or rhodium), while the stability and poisoning resistance seem to be strongly improved by the presence of lanthanide oxides
Electrochemical reactor
No full textAn electrochemical reactor comprises at least one electrolytic cell, each cell is divided by a membrane into two electrode chambers, each one is crossed by flows of liquid and each having at least a corresponding electrode. Both the electrodes have one own face directly in contact with the membrane and have a plurality of openings for the passage of the liquid. Each electrode is provided with one or more contact means for the power supply
Compounds having anti-inflammatory and anti-oxidant activity
No full textThe present invention relates to the field of pharmaceuticals.
In particular, it relates to new compounds of the steroid type having an anti-inflammatory and antioxidant activit
Composti con attività antiinfiammatoria ed antiossidante
No full textLa presente invenzione si riferisce al settore farmaceutico.
In particolare, si riferisce a nuovi composti di tipo steroideo con attività antinfiammatoria e antiossidante
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