|
| |
|
|
Metal nanoparticles in zeolites
Zhang, Yuyan ; Čejka, Jiří (vedoucí práce) ; Zima, Vítězslav (oponent) ; Kubička, David (oponent)
Zeolity se zapouzdřenými kovovými nanočásticemi vzbudily v heterogenní katalýze velkou pozornost díky své vysoké katalytické aktivitě, selektivitě a stabilitě. Tato diplomová práce byla zaměřena na syntézu zeolitových katalyzátorů s malými a rovnoměrně distribuovanými kovovými nanočásticemi. Hlavními cíly bylo zapouzdření kovových nanočástic do zeolitu pomocí kokrystalizační strategie a 2D-3D transformce zeolitu. Doktorská práce byla provedena na oddělení syntézy a katalýzy J. Heyrovského Ústav fyzikální chemie a Katedře fyzikální a makromolekulární chemie na Přírodovědecké fakultě Univerzity Karlovy pod dohledem Prof. Jiřího Čejky. Zeolity jsou anorganické krystalické hlinitokřemičitany s mikroporézní strukturou. Mikropóry zeolitů poskytují ideální prostředí pro umístění kovových nanočástic. Kovových nanočástice vznikající v mikropórech zeolitu mohou být omezeny jeho krystalickou mříží, zabraňující agregaci a vyplavování kovu během reakčního procesu. Průměry mikropórů zeolitu se obvykle pohybujív rozmezí0,3-1,5 nm, což může sloužit k oddělení molekul v závislosti na jejich velikosti a tvaru, čímž se katalyzátory zeolite s kovovými nanočásticemi obohatí o tvarovou selektivitu. Zapouzdření kovových nanočástic do zeolitů může navíc ovlivnit distribuci kovových a kyselých center a vytvořit tak...
|
|
|
Stabilization of metal nanoparticles in MWW zeolite for catalytic applications
Molitorisová, Sidónia ; Shamzhy, Mariya (vedoucí práce) ; Hronec, Mlan (oponent)
Controlling both size of metal nanoparticles (MNPs) and acidobasic characteristics of the zeolite support is highly desirable for preparation of stable and active bifunctional catalysts. 2D-3D transformation of layered zeolite precursor into three-dimensional zeolite coupled with metal encapsulation is one of the most efficient synthetic strategies so far to achieve the appropriate metal dispersion and aggregative stability of MNPs within zeolite matrix. Nevertheless, the effect of support acidic characteristics on the properties of thus prepared metal@zeolite catalyst remained unrevealed, while the synthetic strategy itself requires further optimization to minimize the loss of metal component. This work addresses the influence of chemical composition of zeolite layered precursor on physical-chemical and catalytic properties of metal@zeolite catalysts prepared via 2D-3D transformation strategy, taken Pd@MCM-222D-3D system as a representative example. Both Si/Al ratio of MCM-22P layered precursor (e.g., Si/Al = 15, 20, 30) and Pd loading (e.g., 0.1, 0.3, 0.8 wt.%) were varied resulting in a set of nine Pd@MCM-222D-3D catalysts. In addition, three Pd@MCM-22impreg catalysts with the same metal loading (0.1 wt.%), but different Si/Al ratios of a support were synthesized via conventional impregnation...
|
|
|
Algicidal properties nanofibrous fabrics doped by metals
Ryparová, Pavla ; Wasserbauer, R. ; Rácová, Z. ; Demo, Pavel ; Tesárek, Pavel
The paper presents a novel protection against algae by nanofiber fabrics doped with metal ions. Nanofiber textiles were prepared by electrospinning on the Nanospider LB 500 device, equipped with cylindrical electrodes of a length 600 mm and electrode distance about 140 mm. The produced nanofiber textiles had a specific weight between 2 and 4 g/m2. The entire surface was covered with algae commonly accompanied by bacteria. The sample had placed in the middle of circular dishes having the diameter 20 mm. The cultivation took place at light environment in common laboratory conditions. Algicidal effect was evaluated as the resulting halo size and quality around the sample. The PVA treated sample had not produce any halo effect, unlike the samples with the addition of metal salts (AgNO3, CuSO4 center dot 5H(2)O) that exhibited the halo effect dependent on the concentration the salts, usually ranging from 0.3-2 mm, giving the evidence about their algicidal properties.\n
|
|
| |
|
|
LAYERS OF METALS NANOPARTICLES ON VARIOUS SEMICONDUCTORS FOR HYDROGEN DETECTION
Černohorský, Ondřej ; Žďánský, Karel ; Yatskiv, Roman ; Grym, Jan
Metal nanoparticles have many interesting properties which is given by their space restriction. Their large active surface is very well exploited during catalysis. Pd and Pt are metals know for their ability to dissociate molecular hydrogen on single atoms. We prepared Schottky diodes on semiconductors InP, GaN, GaAs, and InGaAs to obtain hydrogen sensor. Method of preparation such diodes is electrophoretic deposition of Pd or Pt nanoparticles from their colloid solution onto semiconductor substrate. Over the layer of nanoparticles, porous metal contact was prepared. Hydrogen molecules are dissociated on these metal nanoparticles and single atom which settles on the interface between metal and semiconductor and they increase or decrease Schottky barrier height. By this method we can measure from 1 ppm H2 in the air, where the current change is over one order of magnitude
|
host ::
RSS.