Challenges of vertically aligned carbon nanotubes production and application

Carbon nanotubes (CNTs) have play a dominant role in nanotechnology research for over 20 years due to their exceptional properties. Different solid catalytic substrates can be used to produce vertically aligned carbon nanotubes (VACNTs); however it is important that this structure can be achieved mainly on conductive substrates. It is important that further application of this structure is preferable on conductive substrates. The conditions under which the catalytic layer is prepared and synthesized also have major impact on the structure and properties of the resulting vertically aligned carbon nanotubes. Environmental protection and green chemistry are highly discussed topics nowadays. Therefore, the development of energyefficient, sustainable technological solutions is also receiving increasing attention in vertically aligned carbon nanotubes research. Thus, the progress in this direction will be briefly review in this work

The synthesis and the catalytic (catalase and tyrosinase) activities of amino acid copper complexes covalently grafted onto silica gel

In this work the synthesis, structure and certain catalytic properties of amino acid copper complexes covalently grafted onto silica gel are described. The following enzyme mimicking complexes were synthesized and characterised by experimental (FT-IR) and computational (mainly MM+) methods: BOC-His-Cu/silica gel, BOC-Tyr-Cu/silica gel, His-OMe-Cu/silica gel, Tyr-OMe-Cu/silica gel, H-His-Cu/silica gel, H-Tyr-Cu/silica gel His-OH-Cu/silica gel and Tyr-OH-Cu/silica gel. The activities of these substances were also tested in the decomposition of hydrogen peroxide. The majority of the substances proved to be good enzyme mimics displaying either catalase or tyrosinase activity

SOD activity of immobilized enzyme mimicking complexes

A binuclear, imidazolato-bridged, possible superoxide dismutase-mimicking complex (Cu(II)-diethylenetriamino-μ-imidazolato-Zn(II)-tris-aminoethylamine-triperchlorate) was prepared and immobilized on silica gel or among the layers of montmorillonite. The superoxide dismutase (SOD) activity of the complex before and after immobilization was studied by a SOD assay. It was found that the SOD activity of the host-free complex decreased somewhat when montmorillonite was the host, however, using silica gel as host it increased

Szén nanocsövek katalitikus szintézise, felületének és nedvesíthetőségének módosítása szervetlen anyagokkal = Carbon nanotubes: Catalytic synthesis, modification of their surface and wettability properties by inorganic materials

A projekt négy éve alatt - összhangban az eredeti munkatervvel - a szén nanocsövek CVD szintézisének tanulmányozása során kerestük annak a lehetőségét, hogyan növelhető a CNT hozama, illetve hogyan javíthatók a termék mechanikai tulajdonságai. Ezekhez a munkákhoz elengedhetetlenül kapcsolódnak olyan vizsgálatok, melyek a mintáink fizikai-kémiai jellemzését jelentik. A továbbiakban a szén nanocsövek alkalmazhatóságához kapcsolódó vizsgálatokat végeztünk, ami sok esetben első lépésként azok felületi tulajdonságainak módosítását jelenti. Az így módosított anyagok további alkalmazási lehetőségeit is tanulmányoztuk. A vizsgálatokat jelentős részben a pályázatban szereplő kutatók, illetve az ő témavezetésükkel dolgozó hallgatók végezték. (Ezekből számos projektmunka, TDK-dolgozat, diplomamunka készült, és részét képezi nem egy előkészületben lévő PhD disszertációnak is.) | During the four year of the project (in tune with the original proposal) further optimization of CVD synthesis of carbon nanotubes was studied. It is important to improve both the yield and mechanical properties of this material. These investigations were completed with various physico-chemical characterizations. Henceforth the possibility of surface modification of carbon nanotubes was also studied. Due to wettability problem it can be essential for potential application. The possibility of further use of these modified materials was also investigated. The work done mainly by the original staff of the project and of course by students supervised by the above-mentioned researchers. In addition to publication in this report, numerous diploma work and PhD thesis contain these results

Spirális szén nanocsövek CCVD szintézise és tisztítása = Large scale synthesis of purified coiled carbon nanotubes by CCVD method

Többfalú szén nanocsövek nagy mennyiségben történő előállításához a CVD technika népszerű módszer. A képződő szén nanoszerkezetek mérete, szerkezete, morfológiája nagymértékben függ a katalizátor készítés módszerétől és a szintézis módjától. Spirális szén nanocsöveket eddig csak CVD módszerrel sikerült előállítani. Ezek a helikális szerkezetek értelemszerűen nagy jelentőségűek lehetnek nanoelektromechanikai rendszerekhez, mivel rendkívüli sajátságokkal rendelkeznek. Elméleti számítások alapján várható, hogy a szén nanocsövek extra jellemzői kedvezően párosulhatnak a hélixek speciális tulajdonságaival, így kivételes mechanikai, elektromos és mágneses sajátságok alakulhatnak ki. Jelen projekt keretében a spirális szén nanocsövek szelektív szintézisét kívántuk kidolgozni. A legmagasabb szelektivitást (>90%) értünk el abban az esetben, amikor szilícium lap hordozón alakítottuk ki a vas katalizátorunkat: a hordozóra merőlegesen, egymással párhuzamosan növesztettünk spirálokat, létrehozva ezzel spirális szén nanocső erdőket/szőnyegeket. | The large-scale production of multi-wall carbon nanotubes by CVD method is a popular technique. The size, structure and morphology of the resulting carbon nanostructures depends mainly on the method of catalyst preparation and synthesis parameters. Helically carbon nanotubes have been produced only by CVD method. These helical structures can be obviously high potential for nano-electromechanical systems, as extraordinary properties. Based on theoretical studies it is expected that carbon nanotubes combined with the extra features and special properties of a helix has exceptional mechanical, electrical and magnetic propertie. In the present project weour main goal was to develop the selective synthesis of the helical carbon nanotubes. The highest selectivity (> 90%) was achieved in the case where formed our iron catalyst on silicon substrate sheet: our helically coiled carbon nanotubes were grown perpendicularly to the substrate, and parallel to each other, creating herewith spiral carbon nanotube forests / carpets

BiOCl/BiOI composit photocatalysts - investigation of their efficiency using UV and visible led light sources

Due to its unique layered structure, bismuth oxyhalide (BiOX, where X=F, Cl, Br, I) has potential applications as a photocatalytic material in clean energy utilization and environmental purification. In this work, BiOI, BiOCl, and their composites with various BiOI:BiOCl molar ratios were synthesized and characterized for their heterogeneous photocatalytic applications. The methyl orange was used as a model pollutant and UV and visible LED light sources were applied. Adsorption measurements and photocatalytic tests proved that, the BiOI/BiOCl composite, which contains 80% BiOI and 20% BiOCl, showed the best activity. The composite catalyst showed good activity under visible light and was particularly better than pure BiOI and BiOCl under UV radiation. The transformation mechanism of methyl orange is initiated by direct charge transfer processes, via photosensitization

Controlled Synthesis of Visible Light Active CuxS Photocatalyst: The Effect of Heat Treatment on Their Adsorption Capacity and Photoactivity

The effects of different precursor salts, stabilizing agents, and heat treatment parameters are already known to have an influence on the synthesis of nano-sized semiconductors in heterogenous photocatalysis. In the present work, CuxS materials were prepared by using different precursors (copper (II) chloride dihydrate or copper (II) acetate monohydrate) and shape tailoring/stabilizing agents, such as ethylenediaminetetraacetic acid/polyvinylpyrrolidone, and thiourea as the sulfur source. The polyvinylpyrrolidone (PVP) kinetically controlled the growth rate of the nanoplates, while ethylenediaminetetraacetic acid (EDTA) adjusted the nucleation process through the complexation of copper. A one-step hydrothermal method was used for the synthesis, and the materials were characterized by means of morphological and structural complementary investigation methods. Furthermore, the adsorption capacity and photocatalytic activity were also measured for these materials. It was found that the vacancy sites formed by changing the precursor salt, as confirmed by Raman measurements, affect the photocatalytic activity. The rise of the specific surface area was achieved by heat treatment, and concomitantly, the adsorption capacity of the treated samples was found to increase likewise