Pokročilé nízkodimenzionální nanomateriály
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- ItemComparative Analysis of Thermal Activation on Felts and Continuous Carbon Filament Electrodes for Vanadium Redox Flow Batteries(WILEY-V C H VERLAG GMBH, 2024-11-04) Noemí Aguiló Aguayo, Noemí; Ebert, Toni Alena; Amade, Roger; Bertran, Enric; Ospina, Rogelio; Rodriguez Pereira, Jhonatan; de Leon, Carlos Ponce; Bechtold, Thomas; Pham, TungThermal treatments are commonly used to improve electrode kinetics in vanadium redox flow batteries (VRFB). The impact of the widely adopted thermal treatment-400 degrees C for least 24 hours-was investigated on polyacrylonitrile (PAN)-based continuous carbon filaments (tows) and compared to PAN-based graphite felts. Surface properties were assessed with scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and wettability measurements. The electrode activity was investigated via electrochemical impedance spectroscopy (EIS). Charge-transfer resistances and the constant phase element parameters related to the electric double layer were determined, revealing a correlation between enhanced electrode activity and increased double layer across all electrodes. An 8-hour 400 degrees C thermal treatment was sufficient to improve electrode activity for tows, whereas felts required longer durations, up to 24 hours, attributed to differences in the carbonization process employed for each material, with the tows undergoing continuous processing and the felts following a batch process. Three-electrode half-cell EIS measurements were conducted to elucidate positive and negative electrode contributions. Activated continuous carbon filament electrodes exhibited consistent electrode activities in both the catholyte (VO2+/VO2+) and anolyte (V3+/V2+), whereas the electrochemical activity of felts was limited by the electrode deactivation in the anolyte.
- ItemDesign of collectors in centrifugal spinning: Effect on the fiber yield and morphology(SAGE PUBLICATIONS INC, 2024-10-01) Naseri Joda, Nasrollah; Ince, Ahmet Erdem; Říhová, Martina; Pavliňák, David; Macák, JanCentrifugal spinning is an increasingly popular and viable method to produce fibers of different compositions. However, there are still aspects to investigate and improve in the centrifugal spinning process, such as optimizing the fiber yield and obtaining defect-free fiber morphology. To address this gap, the effects of the collectors on the fiber yield and their morphology were investigated in this work. An aqueous solution with 18 wt% of PVP and two needles (18G and 21G) with different diameters and three different spinning speeds (5000, 7000, and 9000 RPM) were used to explore a set of fiber collectors with various collector spacing (1, 3, 6, 12, and 18 cm distance between the collectors' bars). The results of the experiments showed that fiber collectors affect the yield of the process and the fiber morphology to some (non-negligible) extent. Denser collectors enabled higher yield, thus reducing the waste, and positively affecting the beading of fibers. The knowledge obtained in this work about the influence of collectors on the centrifugal processing of basic polymers can be with an advantage applied to the processing of different polymers and needles used within the centrifugal spinning process.
- ItemCarbon fibers decorated with TiO2 nanoparticles for photocatalytic degradation of methylene blue dye(Frontiers Media S.A., 2024-10-23) Chennam, Pavan Kumar; Sepúlveda Sepúlveda, Lina Marcela; Říhová, Martina; Alijani, Mahnaz; Kachlík, Martin; Zazpe Mendioroz, Raúl; Pavliňák, David; Maca, Karel; Macák, JanThis report demonstrates the development of carbon fibers (CFs) decorated with TiO2 nanoparticles (NPs) as an efficient photocatalyst for the photocatalytic degradation of methylene blue (MB) as a model dye. Carbon fibers were produced by carbonization of polyacrylonitrile fibers, previously produced by centrifugal spinning. Subsequently, the CFs were decorated with TiO2 NPs (CFs@TiO2) by tailored soaking protocol using aqueous TiCl4 solution with different concentrations (0.025, 0.05, 0.1, and 0.2 M). SEM analyses revealed that soaking in TiCl4 produced a smooth, conformal, continuous TiO2 nanoparticulate coating with thickness increasing from 40.4 +/- 21.2 to 257.9 +/- 63.9 nm with increasing TiCl4 concentration. X-ray diffraction and Raman spectroscopy confirmed the anatase nature of TiO2. Photocatalytic decomposition rates of MB were assessed under UV light illumination for all CFs@TiO2 samples, and it was revealed that the lowest amount of TiO2 NP on C yielded the highest rates. The synergistic interaction between CFs and TiO2 NPs with a uniform morphology and a well-crystalline anatase structure, present in an optimal amount of fiber bodies, is the key reason for the remarkable photocatalytic performance. This work shows that C fibers decorated with an optimal amount of TiO2 NPs have a great potential as an effective photocatalytic material.
- ItemRecent advances in TiO2 nanotube layers - A mini review of the latest developments in nanotube preparation and applications in photocatalysis and microwave sensing(WILEY, 2024-08-01) Sopha, Hanna Ingrid; Alijani, Mahnaz; Sepúlveda Sepúlveda, Lina Marcela; Macák, JanSelf-organized anodic TiO2 nanotube (TNT) layers prepared by anodization of Ti substrates have attracted great interest within the last 20 years, due to their unique properties and low-cost synthesis. This mini review article aims to shortly summarize the most recent developments in the TNT layer synthesis and applications. It presents the synthesis of high aspect ratio (HAR) TNT layers in a short time by accelerating the TNT layer growth rates in lactic acid containing electrolytes. Furthermore, the etching of TNT layers towards TNT bundles of homogeneous size and single tube powders is discussed, as well as the possibility to grow TNT layers on non-planar Ti substrates, which cannot be directly connected to the potentiostat (e.g., Ti spheres or 3D Ti meshes). As a relatively new application, the employment of TNT layers in microwave resonator sensors is introduced. Last, but not least, approaches of upscaling the TNT layer size from the laboratory scale towards significantly larger scale are outlined and reviewed.
- 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.