Pokročilé nízkodimenzionální nanomateriály

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    Structural and Optical Properties of Luminescent Copper(I) Chloride Thin Films Deposited by Sequentially Pulsed Chemical Vapour Deposition
    (MDPI, 2018-10-01) Krumpolec, Richard; Homola, Tomáš; Cameron, David Campbell; Humlíček, Josef; Caha, Ondřej; Kuldová, Karla; Zazpe Mendioroz, Raúl; Přikryl, Jan; Macák, Jan
    Sequentially pulsed chemical vapour deposition was used to successfully deposit thin nanocrystalline films of copper(I) chloride using an atomic layer deposition system in order to investigate their application to UV optoelectronics. The films were deposited at 125 degrees C using [Bis(trimethylsilyl)acetylene](hexafluoroacetylacetonato)copper(I) as a Cu precursor and pyridine hydrochloride as a new Cl precursor. The films were analysed by XRD, X-ray photoelectron spectroscopy (XPS), SEM, photoluminescence, and spectroscopic reflectance. Capping layers of aluminium oxide were deposited in situ by ALD (atomic layer deposition) to avoid environmental degradation. The film adopted a polycrystalline zinc blende-structure. The main contaminants were found to be organic materials from the precursor. Photoluminescence showed the characteristic free and bound exciton emissions from CuCl and the characteristic exciton absorption peaks could also be detected by reflectance measurements.
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    Intrinsic properties of high -aspect ratio single- and double -wall anodic TiO 2 nanotube layers annealed at different temperatures
    (Elsevier, 2020-08-20) Motola, Martin; Hromádko, Luděk; Přikryl, Jan; Sopha, Hanna Ingrid; Krbal, Miloš; Macák, Jan
    TiO2 nanotube layers of different thicknesses and tube wall morphologies exploited. Single-wall nanotubes were obtained by chemical etching of double-wall ones. Photocurrents, structure, optical and electronic properties of tubes were compared.
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    Anodization of electrodeposited titanium films towards TiO2 nanotube layers
    (Elsevier, 2020-09-01) Sopha, Hanna Ingrid; Norikawa, Yutaro; Motola, Martin; Hromádko, Luděk; Rodriguez Pereira, Jhonatan; Černý, Jiří; Nohira, Toshiyuki; Yasuda, Kouji; Macák, Jan
    Ti films electrodeposited on Ni foils from molten salts were anodized towards TiO2 nanotube formation for the first time. The resulting TiO2 nanotube (TNT) layers were compared with TNT layers prepared under identical conditions on Ti foils by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) measurements, X-ray photoelectron spectroscopy (XPS), and photocurrent measurements. No significant differences were found between the TNT layers prepared on the two different substrates. Electrodeposited Ti films prepared in this way could thus be a viable option for anodization purposes.
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    Fabrication of TiO2 nanotubes on Ti spheres using bipolar electrochemistry
    (Elsevier, 2020-02-01) Sopha, Hanna Ingrid; Hromádko, Luděk; Motola, Martin; Macák, Jan
    In this work, the anodization of Ti spheres using bipolar electrochemistry is reported for the first time. TiO2 nanotubes were found over the entire surface area of the Ti spheres when a square-wave potential was employed. The TiO2 nanotubes were similar to 77 nm in inner diameter and had a thickness of similar to 2 mu m on the extremities of the Ti spheres. Due to their increased surface area, the Ti spheres covered with TiO2 nanotubes had a rate constant for the photocatalytic degradation of methylene blue which was approximately 2.15 times higher than that of non-anodized Ti spheres with a thin thermal oxide layer.
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    Anodic TiO2 nanotube walls reconstructed: Inner wall replaced by ALD TiO2 coating
    (Elsevier, 2021-05-30) Motola, Martin; Zazpe Mendioroz, Raúl; Hromádko, Luděk; Přikryl, Jan; Čičmancová, Veronika; Rodriguez Pereira, Jhonatan; Sopha, Hanna Ingrid; Macák, Jan
    A reconstruction process of TiO2 nanotube (TNT) layers towards their superior photoelectrochemical performance and photocatalytic activity is presented. At first, TNT layers (similar to 5 mu m thick, similar to 250 nm in diameter) were prepared via electrochemical anodization to obtain double-wall (DW) TNT layers. Second, a selective chemical treatment was conducted to etch the inner wall, yielding single-wall (SW) TNT layers. Third, TNT layers were coated by an additional approx. 5.5 nm, 11 nm, and 16 nm thick TiO2 coatings, respectively, using Atomic Layer Deposition (ALD). A pronounced increase in the incident photon-to-electron conversion efficiency (reaching similar to 85% at lambda - 350 nm) was achieved on SW TNT layers coated with 11 nm thick ALD coatings compared to SW without coating (similar to 35% at lambda = 350 nm). This is due to the optimal thickness of the ALD TiO2 coating that passivates surface states and improves the separation of the photogenerated charge carriers. Photocatalytic performance of SW TNT layers with 11 nm thick ALD coatings (rate constant; k = 0.1156 min(-1)) was increased by approx. 10-times compared to that of the nowadays most reported blank DW TNT layers (rate constant; k = 0.0119 min(-1)).