Pokročilé nízkodimenzionální nanomateriály
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- ItemTop-down Surfactant-Free Synthesis of Supported Palladium-Nanostructured Catalysts(WILEY, 2024-03-01) Schott, Christian M.; Schneider, Peter M.; Sadraoui, Kais; Song, Kun-Ting; Garlyyev, Batyr; Watzele, Sebastian; Michalička, Jan; Macák, Jan; Viola, Arnaud; Maillard, Frederic; Senyshyn, Anatoliy; Fischer, Johannes A.; Bandarenka, Aliaksandr S.; Gubanova, Elena L.Nanostructured palladium (Pd) is a universal catalyst that is widely used in applications ranging from catalytic converters of combustion engine cars to hydrogenation catalysts in industrial processes. Standard protocols for synthesizing such nanoparticles (NPs) typically use bottom-up approaches. They utilize special and often expensive physical techniques or wet-chemical methods requiring organic surfactants. These surfactants should often be removed before catalytic applications. In this article, the synthesis of Pd NPs immobilized on carbon support by electrochemical erosion without using any surfactants or toxic materials is reported. The Pd NPs synthesis essentially relies on a Pd bulk pretreatment, which causes material embrittlement and allows the erosion process to evolve more efficiently, producing homogeneously distributed NPs on the support. Moreover, the synthesized catalyst is tested for hydrogen evolution reaction. The activity evaluations identify optimal synthesis parameters related to the erosion procedure. The electrocatalytic properties of the Pd NPs produced with sizes down to 6.4 +/- 2.9 nm are compared with a commercially available Pd/C catalyst. The synthesized catalyst outperforms the commercial catalyst within all properties, like specific surface area, geometric activity, mass activity, specific activity, and durability. A surfactant-free top-down approach, called "electrochemical erosion", allows the fabrication of palladium (Pd) nanoparticles (NPs) supported on Vulcan carbon. Crucially, a Pd wire pretreatment is identified as the essential step to synthesize NPs with sizes below 10 nm. The synthesized Pd/C catalysts are thoroughly analyzed for their structure, morphology, chemical composition, and electrochemical activity toward the hydrogen evolution reactions.image (c) 2024 WILEY-VCH GmbH
- ItemPhotocatalytic degradation of naproxen using TiO2 single nanotubes(FRONTIERS MEDIA SA, 2024-03-13) Sepúlveda Sepúlveda, Lina Marcela; Musial, Joanna; Saldan, Ivan; Chennam, Pavan Kumar; Rodriguez Pereira, Jhonatan; Sopha, Hanna Ingrid; Stanisz, Beata J.; Macák, JanHerein, TiO2 single-tube (TiO2 ST-NT) powders with and without magnetite Fe3O4 nanoparticles (TiO2 ST-NT@Fe(3)O(4)NPs) are presented for the first time as excellent photocatalysts for the degradation of one of the most popular non-steroidal anti-inflammatory drugs (NSAIDs), naproxen (NPX). The TiO2 ST-NT powders were synthesized by anodization followed by etching of the double wall, bending, sonication, ultra-centrifugation, and finally annealing at 600 degrees C. A part of the obtained TiO2 ST-NT powders was decorated with Fe3O4 nanoparticles using a simple one-step decoration process. The best photocatalytic performance of TiO2 ST-NT and TiO2 ST-NT@Fe(3)O(4)NPs powders was obtained under the white light (6.2 x 10(-4) s(-1)) and the blue light (2.7 x 10(-4) s(-1)), respectively. During NPX photodegradation using TiO2 ST-NT powders, three main NPX transformation products (P1, P2, and P3) were detected. Upon excitation with the blue light illumination, TiO2 ST-NT@ Fe(3)O(4)NPs powders exhibited higher performance (similar to 80%) than TiO2 ST-NT powders (similar to 23%) within 1 h, resulting in an approximately three times increased photocatalytic rate constant. Moreover, under simulated sunlight conditions, TiO2 ST-NT powders demonstrated remarkable activity, achieving a 94% NPX degradation within 1 h. TiO2 ST-NT and TiO2 ST-NT@Fe(3)O(4)NPs powders represent excellent photocatalysts for NPX degradation.
- ItemTop-down surfactant-free electrosynthesis of magnéli phase Ti9O17 nanowires(Royal Society of Chemistry, 2024-03-18) Schneider, Peter M.; Schott, Christian M.; Maier, Dominic; Watzele, Sebastian; Michalička, Jan; Rodriguez Pereira, Jhonatan; Hromádko, Luděk; Macák, Jan; Baran, Volodymyr; Senyshyn, Anatoliy; Viola, Arnaud; Maillard, Frederic; Gubanova, Elena L.; Bandarenka, Aliaksandr S.TiO2 nanowires have proven their importance as a versatile material in numerous fields of technology due to their unique properties attributable to their high aspect ratio and large surface area. However, synthesis is an enormous challenge since state-of-the-art techniques rely on complex, multi-stage procedures with expensive, specialized equipment, employing high-temperature steps and potentially toxic precursor materials and surfactants. Hence, we elucidate a simple and facile top-down methodology for the synthesis of nanowires with non-stoichiometric Magn & eacute;li phase Ti9O17. This methodology relies on the electrochemical erosion of bulk Ti wires immersed in an aqueous electrolyte, circumventing the use of environmentally harmful precursors or surfactants, eliminating the need for high temperatures, and reducing synthesis complexity and time. Using multiple techniques, including transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, we provide evidence of the successful synthesis of ultrathin nanowires with the crystal structure of non-stoichiometric Ti9O17 Magn & eacute;li phase. The nanowire width of similar to 5 nm and the Brunauer-Emmett-Teller surface area of similar to 215 m(2) g(-1) make the nanowires presented in this work comparable to those synthesized by state-of-the-art bottom-up techniques.
- ItemSynergistic effect of Pd single atoms and nanoparticles deposited on carbon supports by ALD boosts alkaline hydrogen evolution reaction(Elsevier, 2024-02-15) Bawab, Bilal; Thalluri, Sitaramanjaneya Mouli; Kolíbalová, Eva; Zazpe Mendioroz, Raúl; Jelínek, Luděk; Rodriguez Pereira, Jhonatan; Macák, JanThe synergistic effects between carbon supports and noble metal species of an electrocatalyst are known to effectively boost the alkaline hydrogen evolution reaction (HER). Herein, Atomic Layer Deposition (ALD) was employed to decorate carbon papers with Pd species comprising single atoms (SAs) and nanoparticles (NPs). Transmission electron microscopy analysis revealed the metallic nature and coexistence of Pd as SAs and NPs. The results of X-ray photoelectron spectroscopy supported the evidenced SA species, manifested as the Pd+2. An increase in the electrochemical active surface area from 12.98 to 413.48 cm -2 was evidenced with increasing ALD cycles from 30 to 300c Pd and remained unchanged until 600c Pd. The exceptional overpotential for CP 600c Pd exhibits the lowest value of 4.55 mV, compared to previous reports for Pd electrocatalysts in a nonacidic environment, and confirms the synergistic effect of Pd SAs and NPs that plays a major role in enhancing alkaline HER.
- ItemWell-Blended PCL/PEO Electrospun Nanofibers with Functional Properties Enhanced by Plasma Processing(MDPI, 2020-06-22) Kupka, Vojtěch; Dvořáková, Eva; Manakhov, Anton; Michlíček, Miroslav; Petruš, Josef; Vojtová, Lucy; Zajíčková, LenkaBiodegradable composite nanofibers were electrospun from poly(epsilon-caprolactone) (PCL) and poly(ethylene oxide) (PEO) mixtures dissolved in acetic and formic acids. The variation of PCL:PEO concentration in the polymer blend, from 5:95 to 75:25, revealed the tunability of the hydrolytic stability and mechanical properties of the nanofibrous mats. The degradation rate of PCL/PEO nanofibers can be increased compared to pure PCL, and the mechanical properties can be improved compared to pure PEO. Although PCL and PEO have been previously reported as immiscible, the electrospinning into nanofibers having restricted dimensions (250-450 nm) led to a microscopically mixed PCL/PEO blend. However, the hydrolytic stability and tensile tests revealed the segregation of PCL into few-nanometers-thin fibrils in the PEO matrix of each nanofiber. A synergy phenomenon of increased stiffness appeared for the high concentration of PCL in PCL/PEO nanofibrous mats. The pure PCL and PEO mats had a Young's modulus of about 12 MPa, but the mats made of high concentration PCL in PCL/PEO solution exhibited 2.5-fold higher values. The increase in the PEO content led to faster degradation of mats in water and up to a 20-fold decrease in the nanofibers' ductility. The surface of the PCL/PEO nanofibers was functionalized by an amine plasma polymer thin film that is known to increase the hydrophilicity and attach proteins efficiently to the surface. The combination of different PCL/PEO blends and amine plasma polymer coating enabled us to tune the surface functionality, the hydrolytic stability, and the mechanical properties of biodegradable nanofibrous mats.