Ezüst-tartalmú anyagok előállítása, jellemzése, azok stabilitásának és fotokatalitikus aktivitásának vizsgálata

One of the most concerning Earth’s problems is the lack of adequate water supply. A modern highly efficient water treatment technology could be a solution to the above-mentioned problem, which could be the advanced oxidation processes (AOP). The best-known type of AOP is heterogeneous photocatalysis. The present doctoral thesis is based on heterogeneous photocatalysis, including Ag-based semiconductors. This current work aimed to synthesize, characterize, investigate of the morphological, structural, and photocatalytic properties of various Ag-containing compounds. The key issue was to investigate the effect of the Ag species formed on the surface of the semiconductor on the stability and photocatalytic activity. Our objectives included the study of the impact of different shape-tailoring agents and alkali metal salt cations on the properties of AgX. The oxoacid salts of Ag, such as silver carbonate and silver phosphate was also investigated. In the case of silver carbonate, the effect of the precursors and reaction temperature were also investigated, while in the case of silver phosphate, the impact of the precursors and their concentration was analysed. The stability of the Ag-based semiconductors is still questionable, while only the silver phosphate is reusable. The effect of the different crystal phases of the titanium dioxide on the formation of the Ag and AgO nanoparticles was also investigated. Ag nanoparticles formed on the surface of the rutile crystal phase, while AgO formed on the surface of the anatase. The latter one showed higher stability

Production of CNT forests by a simple layer building method on a conductive substrate

The carbon nanotubes (CNTs) play an important role in nanotechnology research today because the CNT have outstanding properties. Many substrates can be used to fabricate carbon nanotube forests (CNT forests); however, it is important that the desired structure is achieved on a conductive substrate, and for these reasons, carbon nanotube forests have been synthetized on a titanium substrate in this research. Environmental protection is highly discussed nowadays, therefore it is necessary to be able to produce CNT forests with less energy investment and costeffectively. For these reasons, we used dip-coating method, which is a simple process and without heat-treatments step to save energy in achieving the forest structure. Therefore, this research uses a dip-coating method to form a catalyst layer on the surface of the substrate, and to investigate the effect of heat-treatment of the substrate to produce CNT forests directly on the titanium substrate

A simple method to build catalyst layers for the synthesis of vertically aligned carbon nanotubes

Nowadays, environmental protection and sustainability are getting more and more attention. Thus, our aim was to develop a cost and energy efficient catalyst layer building method for the synthesis of carbon nanotube forests. A simple spray coating method was used to develop a catalyst layer on the surface of the titanium substrates. Then vertically aligned carbon nanotubes (VACNTs) were synthesized directly on the substrate via catalytic chemical vapor deposition (CCVD) method. During our research, the effect of catalyst layer deposition parameters on the structure of CNTs was investigated and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy

Ag-alapú fotoaktív anyagok előállítása, jellemzése és alkalmazhatósági vizsgálata: Synthesis, characterization and applicability of Ag-based photoactive materials

One of the most actual problems is the continuous decrease in clean water suitable for human consumption or industrial use. One of the main reasons for this is the use of organic pollutants (including organic dyes) used in industrial activities, their efficient removal being often challenging from wastewaters. Silver-based photocatalysts can be used efficiently in these processes due to their physicochemical properties (e.g. low band gap energy) and can be obtained relatively easily.Considering the aspects mentioned above, we focused our research on Ag3PO4 and AgBr-based photocatalysts, investigating their morpho-structural and optical properties, using XRD, SEM, and DRS. The photocatalytic efficiency of as-obtained semiconductors was investigated in the presence of an organic contaminant (methyl orange) under visible light irradiation, paying particular attention to the stability of our photoactive materials Kivonat Napjaink egyik legkiemelkedőbb problémája az emberi fogyasztásra vagy akár ipari felhasználásra alkalmas tiszta víz mennyiségének csökkenése. Ennek egyik oka az ipari tevékenységek során felhasznált szerves szennyezőanyagok (többek között festékek és színezőanyagok), melyek szennyvizeinkből történő eltávolítása gyakran nehézségekbe ütközik. Erre a problémára nyújthatnak megoldást az ezüst alapú fotokatalizátorok, amelyek fizikai-kémiai tulajdonságai alapján (alacsony tiltottsáv szélesség) látható fényben aktiválhatóak, emellett könnyen előállíthatóak.A fentiek alapján kutatásainkat két anyagcsoport irányába indítottuk el, kísérleteink során  Ag3PO4 és AgBr alapú fotokatalizátorokat állítottunk elő, majd vizsgáltuk ezek anyagszerkezeti és optikai jellemzőit (többek között XRD, SEM és DRS segítségével). Fotoaktív anyagaink aktivitását metilnarancs modellszennyező bontásával vizsgáltunk látható fény megvilágítása mellett, külön figyelmet szentelve a félvezetőnk stabilitásának.  &nbsp

Kereskedelmi TIO2 fotokatalizátorok, arany nanoketrecekkel való módosítása és aktivitására való hatása

Modified TiO2-based composite photocatalysts were applied in order to degrade phenol and oxalic acid model pollutants. As co-catalysts noble metal nanoparticles (Ag nanoparticles and Au nanocages) were deposited onto the base photocatalysts. The Au nanocages were obtained by both a direct and an indirect synthesis approach, while the composites were fabricated by using either in-situ or impregnation techniques for noble metal deposition. The obtained Au/TiO2 and Ag/TiO2 composites were characterized by different methods, such as XRD (X-ray Diffraction), TEM (Transmission Electron Microscopy), DRS (Diffuse Reflectance Spectroscopy) and XRF (X-ray fluorescence). The result of our research is that the amount of oxalic acid was lower in case of silver nanoparticles, similarly in the case of phenol degradation to the silver nanoparticles/TiO2 composites were more active. The gold nanocages composites low conversion value is due to the intermediates adsorption on the surface of TiO2

Detailed investigation of Phenol Degradation on Au/TiO2 Composite Materials

Photocatalytic applicability of different TiO2-based nanomaterials is a current hot topic. Therefore, our interest for the present research was to elucidate the formation of primary and secondary intermediates during the phenol degradation by photocatalysis, in the presence of Au/TiO2 nanocomposites. The composites consisted of differently shaped gold nanoparticles and commercial titania (Evonik Aeroxide P25). The obtained composites and the noble metal nanoparticles’ morphology was investigated by Transmission Electron Microscopy (TEM), their optical properties were explored using Diffuse Reflectance Spectroscopy (DRS), while the crystal structure was characterized by X-ray diffraction (XRD). The photocatalytic activity was investigated by photodegradation of phenol and methyl orange. In case of phenol it was shown that, the formation of degradation intermediates, was dependent on the Au nanoparticles’ shape, leading to high amounts of different intermediates as follows: hydroquinone for composites with spherical Au nanoparticles, 1,2,4-trihydroxy-benzene for triangle shaped nanoparticles, and pyrocatechol for TiO2

Ag3PO4 tartalmú bioaktív üveg kompozitok előállítása, jellemzése és antibakteriális hatásának a vizsgálata: Synthesis, characterization, and antibacterial behavior analysis of the Ag3PO4 containing bioactive glass

Based on the low stability of the Ag nanoparticles and the high biocompatibility of phosphate-ion, this work deals with a combination of the above-mentioned two ions (Ag3PO4), and their application in biological systems. The precipitation synthesis method was used for Ag3PO4 synthesis. The microcrystals were analyzed by using scanning electron microscopy; X-ray diffractometry; infrared spectroscopy; and diffuse reflectance spectroscopy. The sol-gel method was used for the synthesis of bioactive glass, where the silver-phosphate was added in 3 different proportions (0; 0.1; 0.2; 0.4 mol%). Afterward, as-prepared samples were characterized by the above-mentioned methods and X-ray photoelectron spectroscopy. Antibacterial behavior of the samples was analyzed by using two different bacterial strains, where the composite, with 0.4% of Ag3PO4 resulted in the highest antibacterial character. Kivonat Az ezüst nanorészecskék gyenge stabilitását és a foszfát-ion erős biokompatibilitását alapul véve célunk volt ezen két ion együttes alkalmazása (Ag3PO4) és azok biológiai közegben való felhasználása. Az ezüst-foszfátok előállításakor csapadékképző reakciót alkalmaztunk. A mikrokristályokat pásztázó elektronmikroszkóp, röntgendiffraktométer, infravörös spektrométer és diffúz reflexiós spektrofotométer segítségével jellemeztünk. Az ezüst-foszfátot 3 különböző mennyiségben (0; 0,1; 0,2; 0,4 mol%) adagoltuk a bioaktív üveg rendszerébe, szol-gél módszert alkalmazva. Majd a fent említett műszerek segítségével és röntgen fotoelektron spektroszkóppal vizsgáltuk a szerkezeti, optikai és morfológiai változásokat. A minták antibakteriális hatását két különböző baktériumtörzsön vizsgáltuk, ahol azt vettük észre, hogy a 0,4% Ag3PO4-t tartalmazó minta rendelkezett a legmagasabb antibakteriális hatással.&nbsp