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The annealing of MoS2 films shows a transition from the mixed 1T′@2H local order (amorphous) toward the long-range 2H order (polycrystalline). So far uncovered potential of amorphous MoS2 as an agent for photothermal therapy is evidenced.

This article discusses the spectral dependences of the absorption coefficient of thin arsenic sulphide films obtained by spin-coating, identified using a single-beam spectrophotometer in the wavelength range of 400–1000 nm. The effect of doping of molybdenum on the optical band gap is studied. While for a pure glass the band gap decreases with higher sulphur concentration, the opposite trend is observed in glass doped with molybdenum. Molybdenum doping also leads to an increase in Urbach energy. The obtained experimental curves are compared with theoretical ab-initio calculations.

Herein, hierarchical MoSe2/1D TiO2 nanotube layer structure was successfully fabricated in a simple and fast fashion and its photocatalytic and electrocatalytic properties were assessed. The novelty of this work lies in the utilization of Atomic Layer Deposition (ALD) technique to deposit MoSe2 nanosheets on 1D TiO2 nanotube layers. The photoelectrochemical and photo- and electrocatalytic properties were explored and optimized as a function of the MoSe2ALD cycles. ALD allowed precise control on MoSe2 nanosheet size, and in turn, on the surface structure, which is pivotal for efficient catalysts. The MoSe2 nanosheets grew on both inner and outer 1D TiO2 nanotube surface mainly perpendicularly oriented, maximizing the exposed active edges, an essential aspect to fully exploit the MoSe2 photo- and electrochemical properties. Outstanding photo- and electrocatalytic activity were recorded in both dye organic pollutant degradation and hydrogen evolution reaction applications, respectively. The excellent photocatalytic and electrochemical activity stems from the synergy between tailored ALD loading of MoSe2 nanosheets on 1D TiO2 nanotubular structure with high surface/volume ratio, which provided fast electron transfer and easy access to the MoSe2 active edges, boosting the catalytic activity. V této práci jsme vytvořili hybridní strukturu MoSe2 nanodestiček na 1D TiO2 nanotrubicových vrstvách jednoduchým a rychlým způsobem. Novost naší práce spočívá ve využití techniky depozice atomárních vrstev (ALD) pro deponování MoSe2 nanodestiček na 1D TiO2 nanotrubicové vrstvy. U výsledných materiálů jsme zhodnotili výsledné fotokatalytické a elektrokatalytické vlastnosti v závislosti na počtu použitých depozičních ALD cyklů. ALD umožnilo velmi precizní kontrolu velikosti MoSe2 nanodestiček a také mělo vliv na na jejich povrchovou strukturu, která je klíčový pro výsledné vlastnosti. Tyto nanodestičky rostly jak uvnitř trubic, tak na jejich externím povrchu, kolmo orientované k trubicovým stěnám, což vedlo k maximálnímu možnému obnažení aktivních center na hranách nanodestiček. Velmi vysoké foto- a elektrokatalytické aktivity byly dosaženy pro rozklad modelových organických látek a pro vývoj vodíku, respektive. Tyto výkony pramení ze synergie mezi MoSe2 nanodestičkami a 1D TiO2 nanotrubicovými vrstvami s vysokým poměrem dostupného povrchu/objemu, což umožnilo velmi dobrý přenos elektronů a snadný přístup reaktantů k aktivním centrům MoSe2 nanodestiček.

The continuous emission of nitrous oxides contributes to the overall air pollution and deterioration of air quality. In particular, an effective NO2 sensor capable of low concentration detection fo...

Proper respiratory tract protection is the key factor to limiting the rate of COVID-19 spread and providing a safe environment for health care workers. Traditional N95 (FFP2) respirators are not easy to regenerate and thus create certain financial and ecological burdens; moreover, their quality may vary significantly. A solution that would overcome these disadvantages is desirable. In this study a commercially available knit polyester fleece fabric was selected as the filter material, and a total of 25 filters of different areas and thicknesses were prepared. Then, the size-resolved filtration efficiency (40–400 nm) and pressure drop were evaluated at a volumetric flow rate of 95 L/min. We showed the excellent synergistic effect of expanding the filtration area and increasing the number of filtering layers on the filtration efficiency; a filter cartridge with 8 layers of knit polyester fabric with a surface area of 900 cm2 and sized 25 × 14 × 8 cm achieved filtration efficiencies of 98 % at 95 L/min and 99.5 % at 30 L/min. The assembled filter kit consists of a filter cartridge (14 Pa) carried in a small backpack connected to a half mask with a total pressure drop of 84 Pa at 95 L/min. In addition, it is reusable, and the filter material can be regenerated at least ten times by simple methods, such as boiling. We have demonstrated a novel approach for creating high-quality and easy-to-breathe-through respiratory protective equipment that reduces operating costs and is a green solution because it is easy to regenerate.

In this work, we clearly demonstrate the efficacy of using XANES spectroscopy in conjunction with a Pilatus detector as a sensitive tool to allow the study of the oxidation process in GeTe alloys via depth profile analysis. On the basis of Ge K-edge XANES spectra, it was found that GeTe alloys do not oxidize readily after an initial native surface oxidation that occurs upon exposure to oxygen in the air at the elevated temperatures, 100 °C and 330 °C. We demonstrate that amorphous GeTe possesses a higher predisposition to oxidation than crystalline GeTe when exposed to the air at temperature of 100 °C. When the temperature is set to 330 °C in an air ambient, we show that the amorphous to crystal phase transition affects the oxidation process more significantly than the simple annealing of crystalline GeTe. We suggest that the higher tendency of GeTe films to oxidize during the phase transition is a consequence of the breaking of Ge–Ge bonds in the presence of oxygen atoms which subsequently leads to the extra formation of Ge–O bonds during crystallization.

Atomic layer deposition (ALD) represents a unique deposition technique that allows to coat uniformly var-ious high aspect ratio (HAR) porous nanostructures, in addition to its traditional role to coat flat substrates(e.g. Si wafers). Self-organized anodic TiO2nanotube (TNT) layers belong among the most investigatedinorganic nanostructures. They possess highly functional materials with promising application potentialacross many technological fields. Herein, we review the utilization of ALD for the functionalization ofanodic TNT layers by secondary materials to advance their physicochemical and photoelectrochemicalproperties. First, the application of ALD for functionalization of porous aluminium oxide, which representfundamental HAR nanostructure, is briefly introduced. Then the main experimental parameters govern-ing the uniformity and the conformality of ALD coating within HAR nanostructures are discussed. Finally,the review focuses on the use of ALD to deposit secondary materials into TNT layers for various purposes— the introduction of pioneering studies is followed by particular examples of ALD based functional-izations of coated TNT layers for optimized visible-light absorption, charge separation and passivation,(photo)catalysis, stability, gas sensing, and energy storage. Depozice Atomárních vrstvev (ALD) je unikátní depoziční technika, jenž umožňuje pokrýt rovnoměrně různé porézní nanostruktury s vysokým poměřem stran (tloušťka vs průměr), kromě své tradiční role pro pokrývání rovných substrátů (např. Si waferů). Samoorganizované vrstvy anodických TiO2 nanotrubic (TNT) patří mezi nejstudovanější anorganické nanostruktury. Představují velmi funkční materiál s mnoha aplikačními příležitostmi v různých technologických oborech. V tomto přehledovém článku shrnujeme využití ALD pro funkcionalizaci anodických TNT různými sekundárními materiály s cílem ještě více lepšit jejich celkové fyzikálně-chemické a fotoelektrochemické vlastnosti. V první kapitole popisujeme využití ALD pro funkcinalizaci porezního oxidu hlinitého, což je základní porézní materiál a historicky předchází TNT. V druhé kapitole jsou diskutovány hlavní experimentální parametry techniky ALD, které ovlivňují rovnoměřnost a homogenitu ALD vrstev v jednodimenzionálních strukturách s vysokým poměřem stran. V hlavní části poskytujeme přehled využití různých ALD vrstev na TNT pro různé účely. Po představení pionýrských prací v relevantním oboru uvádíme různé příklady funkcionalizací, které mají zásadní vliv na absorpci viditelného světla do trubic, rozdělění náboje, pasivaci defektů, fotokatalýzu, stabilitu, citlivost na plyny a ukládání energie.

Annealing of amorphous TiO2 nanotubes has been performed by nano-, pico- and femtosecond lasers. Only picosecond high-power laser of the HiLASE Centre enabled achieving crystallization into anatase phase via explosive solid-phase crystallization at high throughput.

In this study, crystallization of amorphous TiO

The unique optical properties of phase change materials (PCMs) can be exploited to develop efficient reconfigurable photonic devices. Here, we design, model, and compare the performance of programmable 1 × 2 optical couplers based on: Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3, and Sb2S3 PCMs. Once programmed, these devices are passive, which can reduce the overall energy consumed compared to thermo-optic or electro-optic reconfigurable devices. Of all the PCMs studied, our ellipsometry refractive index measurements show that Sb2S3 has the lowest absorption in the telecommunications wavelength band. Moreover, Sb2S3 -based couplers show the best overall performance, with the lowest insertion losses in both the amorphous and crystalline states. We show that by growth crystallization tuning at least four different coupling ratios can be reliably programmed into the Sb2S3 directional couplers. We used this effect to design a 2-bit tuneable Sb2S3 directional coupler with a dynamic range close to 32 dB. The bit-depth of the coupler appears to be limited by the crystallization stochasticity.

In this work, for the first time, an anodic TiO2 nanotube layer of large area (~50 cm2) was used for photocatalysis in the gaseous phase. Hexane was chosen as model pollutant. The nanotube layer showed superior efficiency compared to a reference TiO2 layer of the same thickness composed of immobilized P25 nanoparticles. An additional TiO2 coating of the nanotube layer produced by atomic layer deposition did not enhance the photocatalytic degradation of hexane due to a decrease in the active surface area, in contrast to liquid state photocatalysis under applied external potential. Keywords: Titanium dioxide, Nanotubes, Large area, Photocatalysis, Hexane

Here we report on structural properties and the photo-electrochemical response of annealed TiO2 nanotube layers, grown on four different Ti substrates by an identical anodization process. TiO2 nanotube layers were grown on Ti substrates by anodization in glycerol containing NH4F and water. The layers were then annealed at 400 °C for 1 h in air. Photocurrent densities of annealed nanotubes were recorded upon irradiation with ultraviolet (UV) light at a constant potential of 0.4 V, in a 0.1 M Na2SO4 aqueous solution. Approximately, a 280% difference in the photocurrent densities was recorded from TiO2 nanotubes fabricated from different Ti substrates. To elucidate the origin of this difference, the nanotube layers were scrutinized by Mott-Schottky measurements, X-ray diffraction (XRD) and Electron Energy Loss Spectroscopy (EELS). Inspection of the XRD patterns revealed preferential crystallographic orientations in various Ti substrates from which TiO2 nanotube layers were produced. Subsequent EELS analyses of the annealed nanotube layers disclosed significant differences in the Ti:O stoichiometry, in accordance with XRD evaluation of preferential orientation differences among used Ti substrates.

Herein, a new strategy to efficiently harvest photons in solar cells is presented. A solar cell heterostructure is put forward, based on a 1D conical TiO2 nanotubular scaffold of high aspect ratio, homogenously coated with a thin few nm layer of CdS light absorber using atomic layer deposition (ALD). For the first time, a large variety of conical nanotube layers with a huge span of aspect ratios was utilized and ALD was used for the preparation of a uniform CdS coating within the entire high surface area of the TiO2 nanotubes. The resulting 1D conical CdS/TiO2 tubular heterostructure acts as a sink for photons. Due to the multiple light scattering and absorption events within this nanotubular sink, a large portion of photons (nearly 80%) is converted into electrons. It is the combination of the scaffold architecture and the light absorber present on the high surface area as a very thin layer, the optimized charge transport and multiple optical effects that make this heterostructure very promising for the next generation of highly performing solar cells.

The crystallization process acts as a bottleneck to the development of phase-change memory devices. Here, we compare the crystallization of as-deposited and pressure-induced amorphous phases of Ge2Sb2Te5 under hydrostatic pressures up to 8.5 GPa. The as-deposited phase fully converts to a stressed metastable cubic phase (at ca. 135 °C) at pressures below 3 GPa and remains cubic up to the maximum temperature used (240 °C). At higher pressures, the as-deposited phase partially crystallizes directly into the stable hexagonal phase at a significantly lower temperature (110 °C), however a significant volume fraction of the amorphous phase remains even for temperatures as high as 240 °C. The intensities of the Bragg diffraction peaks dramatically decrease with increasing pressure, further underscoring the suppression of crystal growth. In stark contrast, the pressure-induced amorphous phase- due to memory effects originating from the crystalline phase - crystallizes at ambient conditions at a lower temperature than its as-deposited counterpart. Furthermore, the pressure-induced amorphous phase also fully transforms directly into the hexagonal modification at pressures up to ca. 5 GPa. At higher pressure (8.5 GPa), an orthorhombic phase is formed. Different from the as-deposited phase, the crystallization temperature of pressure-induced amorphous Ge2Sb2Te5 increases with pressure. The results reported here demonstrate that differences in nanoscale ordering in as-deposited (statistically ordered) and pressure-induced (chemically ordered) amorphous phases dramatically influence crystallization and will serve as a guideline for insightful development of phase-change devices.

The possibility of making lithographic masks based on As2S3 chalcogenide glass with ultimately small size of resist elements has been investigated. Interference lithography using synchrotron radiation with a wavelength of 13.4 nm, corresponding to extreme ultraviolet light, was used. High-quality masks with elements of 30 nm in size were obtained. In a dynamic light scattering study, resist particles of about 3 nm in size were found in the developer after the development process, which corresponds to the intermediate-range order parameter in the structure of the chalcogenide glass. It is assumed that this grain size determines the ultimate resolution, roughness and unevenness of the edge of the inorganic resist mask. Byla zkoumána možnost výroby litografických masek na bázi chalkogenidového skla As2S3 s ultimátně malou velikostí rezistových prvků. Byla použita interferenční litografie využívající synchrotronového záření o vlnové délce 13,4 nm, odpovídající extrémnímu ultrafialovému světlu. Byly získány vysoce kvalitní masky s prvky o velikosti 30 nm. Ve studii dynamického rozptylu světla byly ve vývojce po procesu vyvolávání nalezeny částice rezistu o velikosti asi 3 nm, což odpovídá uspořádání na střední vzdálenost ve struktuře chalkogenidového skla. Předpokládá se, že tato velikost zrna určuje konečné rozlišení, drsnost a nerovnosti okraje masky anorganického rezistu.

New materials bearing thiophene and helicene moieties were prepared by a potential-driven on/off switch strategy onto the surface of glassy carbon and indium tin oxide substrates. Specifically, a 3-([7]helicen-9-yl)-thiophene hybrid monomer was electrooxidized in acetonitrile by cyclic voltammetry with anodic potential limits of +1.5 V or +2.5 V, resulting in a conductive and non-conductive polymer, respectively. The electrochemical findings were supplemented by microscopy investigations; UV-Vis, fluorescence and vibrational spectroscopies; 1H NMR spectroscopy; ellipsometry measurements and computational chemistry. The electrodeposited polymers could be used for the further development of materials applicable in organic electronics, optoelectronics and sensing technologies.

Using N K-edge XANES studies, we demonstrate a noticeable difference in local structure around the nitrogen atoms in as-deposited amorphous and annealed N-doped GeTe-based phase change alloys. The pronounced changes appear as a ≈ 2 eV shift in the absorption edge to higher photon energies and the overall shape of the XANES spectrum. Comparison of the experimental XANES spectrum of the as-deposited amorphous phase with ab-initio XANES simulations discloses that the as-deposited phase mainly consists of the NGe3 and the NTe3 pyramidal units in approximately equal concentration. When annealed, NTe3 units gradually rebond to the NGe3 units and at the same time N atoms diffuse through the amorphous phase to form the GexNy aggregates. Upon long-standing annealing at 400 ∘ C a compact interlayer of Ge3N4 is formed in the crystalline phase.

ALD CdS-coated TiO2 nanotube layers: effect of downscaling diameter of TiO2 nanotubes and their annealing treatment on IPCE., Herein, a novel photoelectrochemical heterostructure based on TiO2 nanotube layers uniformly coated by a CdS thin layer (using ALD) is presented. Downscaling the nanotube diameter (from 95 to 35 nm) resulted in a 2-fold enhancement of the UV and Vis light photocurrents. Further photocurrent improvement resulted from the prior annealing of the TiO2 nanotube layers from 300 to 600 °C.

We report on the optical properties of Er-doped As3S7 chalcogenide films prepared using the two step dissolution process utilizing the As3S7 glass dissolved with propylamine and by further addition of the tris(8-hydroxyquinolinato)erbium(III) (ErQ) complex acting as an Er3+ precursor. Thin films were deposited by spin-coating, thermally stabilized by annealing at 125 °C and further post-annealed at 200 or 300 °C. The post-annealing of films at 200 °C and 300 °C densifies the films, improves their optical homogeneity, and moreover activates the Er3+:4I13/2 → 4I15/2 (λ ≈ 1.5 μm) PL emission at pumping wavelengths of 808 and 980 nm. The highest PL emission intensity was achieved for As3S7 films post-annealed at 300 °C and doped with ≈1 at% of Er which is beyond the normal Er3+ solubility limit of As–S melt-quenched glasses. The solution-processed deposition of the rare-earth-doped chalcogenide films utilizing the organolanthanide precursors has much potential for application in printed flexible optoelectronics and photonics.

We report the synthesis and characterization of self-supported sulphurized TiO2 nanotube layers as a cathode material for Li microbatteries. Sulphurized TiO2 nanotubes were obtained by annealing of selfsupported TiO2 nanotubes in sulphur atmosphere. The morphology, structure, composition and thermal stability of the TixOySz nanotube layers were studied by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and thermogravimetric analysis. The electrochemical behaviors of the chemically modified nanotubes were investigated by cyclic voltammetry and chronopotentiometry techniques. This nanostructured electrode used as a cathode material showed high rate capabilities even at very fast kinetics. Remarkably, a high discharge capacity (340 mu Ah cm(-2)) has been retrieved after 100 cycles with 100% coulombic efficiency attesting the excellent stability of the electrode. (C) 2019 The Authors. Published by Elsevier Ltd. Popisujeme syntézu a charakterizaci samonosných sířených vrstev TiO2 nanotrubic jako katod pro lithiové mikrobaterie. Sířené TiO2 nanotrubice byly získány žíháním samonosných TiO2 nanotrubiček v atmosféře síry. Morfologie, struktura, složení a tepelná stabilita vrstev TixOySz nanotrubic byly studovány skenovací elektronovou mikroskopií, transmisní elektronovou mikroskopií, rentgenovou difrakcí, rentgenovou fotoelektronovou spektroskopií a termogravimetrickou analýzou. Elektrochemické chování chemicky modifikovaných nanotrubic bylo zkoumáno technikami cyklické voltametrie a chronopotenciometrie. Tato nanostrukturovaná elektroda použitá jako katoda vykazovala vysoké rychlosti i při velmi rychlé kinetice. Je pozoruhodné, že po 100 cyklech byla získána vysoká vybíjecí kapacita (340 μAh cm−2) se 100% coulombickou účinností, což svědčí o vynikající stabilitě elektrody.

Two-dimensional MoS2 nanostructures are highly interesting and effective in a number of energy-related applications. In this work, the synthesis of ultra-thin MoS2 nanosheets produced by the thermal Atomic Layer Deposition (ALD) process is reported for the first time using a previously unpublished set of precursors, namely bis(t-butylimido)bis(dimethylamino)molybdenum and hydrogen sulfide. These nanosheets are homogenously deposited within one-dimensional anodic TiO2 nanotube layers that act as a high surface area conductive support for the MoS2 nanosheets. The decoration of high aspect ratio TiO2 nanotube layers with MoS2 nanosheets over the entire nanotube layer thickness is shown for the first time. The homogeneous distribution of the MoS2 nanosheets is proved by STEM/EDX. This resulting new composite is employed as anode for Li-ion microbatteries. The MoS2-decorated TiO2 nanotube layers show a superior performance compared to their counterparts without MoS2. Compared to electrochemical performance of pristine TiO2 nanotube, a more than 50% higher areal capacity and a coulombic efficiency of 98% are obtained on the MoS2 decorated TiO2 nanotube layers, demonstrating clear synergic benefits of the new composite structure. Dvojdimenzionální MoS2 nanostruktury jsou velmi efektivní a zajimavé v řade energeticky zaměřených aplikací. V této práci popisujeme syntézu ultratenkých MoS2 nanovrstev pomocí termální depozice atomárních vrstev (ALD) s využitím doposud nepopsané kombinace prekursorů, jmenovitě bis(t-butylimido)bis(dimethylamino)molybdenum a sulfanu. Tyto nanovrstvy byly připraveny na jednodimenzionálních vrstvách TiO2 nanotrubic, které figurují jako vysoce porézní a vodivá matrice pro MoS2 nanovrstvy. Pomocí analýzy skenovací transmisní elektronovou mikroskopií v kombinaci s energiově disperzní rentgenovou spektroskopií (STEM/EDX) dokládáme homogenní pokrytí nanovrstev MoS2 ve vrstvách TiO2 nanotrubic. akto vytvořené komposity jsou popsány poprvé v tomto článku a jsou také poprvé využiti jako anody v lithiových mikrobateriích. Vrstvy nanotrubic dekorované MoS2 nanovrstvami vykazují až o 50% vyšší plošnou kapacitu než samotné trubice. Bylo také dosaženo vysoké kolumbické účinnosti (až 98%) při nabíjení a vybíjení, což je vynikající výsledek, který jasně demonstruje synergické benefity tohoto nového kompositu.

n this work, we show that sulfur treated 1D anodic TiO2nanotube layers lead to improved photo-electrochemical and catalytic properties compared to the blank nanotube layers. This treatment wasperformed in the evacuated quartz ampoules in the temperature range from 250 to 450◦C. Inspectionof the sulfurized nanotube layers via scanning electron microscopy (SEM) and X-ray diffraction (XRD)has disclosed a gradual crystal growth within nanotube walls, represented by TiS2or TiS3phases. Opti-mally sulfurized TiO2nanotube layers exhibit 3 times enhanced photocurrent in the UV spectral region,compared to the blank counterpart, with a shift of the light absorption up to the wavelength of 550 nm.In addition, the photocatalytic decomposition of a methylene blue aqueous solution using a wavelengthof 365 nm is gradually improved with increasing sulfurization temperature. The highest photocatalyticdecomposition rate is 2.3 times larger compared to the blank TiO2nanotube layer. The application ofsulfurized TiO2nanotube layers for the electrocatalytic hydrogen evolution is also discussed. V této práci jsme ukázali, že modifikace 1D anodických TiO2 nanotrubic sírou vede ke zlepšení fotoelektrochemických a katalytických vlastností ve srovnání s nesířenými nanotrubicemi. Síření bylo provedeno v evakuovaných křemenných ampulích v teplotním rozmezí od 250 do 450 ° C. Pozorování vrstev sířených nanotrubic pomocí skenovací elektronové mikroskopie (SEM) a rentgenové difraktometrie (XRD) odhalilo postupný růst krystalů ve stěnách nanotrubic, reprezentovaných fázemi TiS2 nebo TiS3. Optimálně sířené vrstvy TiO2 nanotubic vykazují ve srovnání s nesířenými vrstvami v UV spektrální oblasti 3krát vyšší fotoproud a posun absorpce světla až do vlnové délky 550 nm. Navíc, fotokatalytický rozklad vodného roztoku methylenové modři při použití vlnového délky 365 nm se postupně zlepšuje se zvyšující se teplotou síření. Nejvyšší rychlost fotokatalytického rozkladu je 2.3krát větší ve srovnání s nesířenou vrstvou TiO2 nanotrubic. Diskutováno je také použití sířených vrstev TiO2 nanotrubic. pro elektrokatalytický vývoj vodíku.

Local- and intermediate-range atomic order in a (Ga2Se3)0.25(GeSe2)0.75, or Ga2Ge3Se9 glass, having a high infrared transparence coefficient, was investigated by using a combination of anomalous X-ray scattering (AXS), X-ray and neutron diffraction (XRD and ND), and reverse Monte Carlo (RMC) modeling. By adding the ND pair distribution function to AXS and XRD results, reasonable partial structure factors and partial pair distribution functions were obtained, even applying no constraints of shortest interatomic distances during the RMC calculation procedure. Total coordination numbers around Ga, Ge, and Se atoms are 3.80, 4.68, and 2.25, respectively, which contradict the 8 − N rule. The numbers of Ga-Ga, Ga-Ge, Ge-Ga, and Ge-Ge wrong bonds were found to be 0.71, 1.32, 0.76, and 1.12, respectively. In the three-dimensional atomic configuration, the structure looks inhomogeneous in both density and concentration.

Here we report on a Li-S battery with cathode, based on a S powder obtained from bulk amorphous S, by cryogenic grinding. The cathode was prepared from a slurry, wherein the content of cryo-ground S powder was equal to 80 wt % (corresponds to ≈ 2.26 mg cm−2). Other slurry components included carbon Super P, and polyvinylidene fluoride, dispersed in N-methylpyrrolidone. The electrochemical performance of the as-prepared battery was compared to a battery based on an identically prepared paste, but containing reference S powder (with the orthorhombic structure). A longer life cycle, and enhanced capacity per gram, as well as per cm2 of electrode was revealed for the cryo-ground S-based cathode. The electrochemical results show that the loss in capacity of the cryo-ground S powder cathode was just 3% after 50 cycles, which suggests on a higher stability of S inside the cathode during cycling.

This work reveals that doping Ag into Sb 2 S 3 substantially decreases its crystallisation temperature. We show that applying an electric field to Sb 2 S 3 through Ag electrodes provides control of the crystallisation temperature and crystallisation rate. The crystal nuclei incubation time decreases substantially when the applied electric field is set to 200 kV/m. The applied electric field appears to force the Ag cations through the amorphous chalcogenide film resulting in Ag doped Sb 2 S 3 filaments that extend from the cathode to the anode. This was confirmed by X-ray fluorescence composition mapping. Density functional theory molecular dynamics modelling of Ag doped Sb 2 S 3 reveals that the diffusion constant of Ag is twice that of Sb or S over a wide temperature range, which implies that the Ag atoms are mobile in the amorphous Sb 2 S 3 structure. The applied electric field provides a mechanism to enhance the crystallisation kinetics of Ag-doped Sb 2 S 3 .

This article reviews metastability in three different classes of chalcogenides-chalcogenide glasses, phase-change alloys, and transition-metal dichalcogenides-with the focus on the relationship between structural metastability and the nature of chemical bonding. While the presence of lone-pair electrons in chalcogenide glasses enables a variety of bond switching processes, the existence of resonant (metavalent) bonding in phase-change alloys is key to the transformation between the crystalline and amorphous states. Strong covalent bonds in 2D transition-metal dichalcogenides limit the transformation to slides and buckling of atomic planes without major bond rupture. It is proposed that combining different kinds of local bonding may be an efficient way to engineer amorphous chalcogenides with desired properties. Tento článek hodnotí metastabilitu ve třech různých třídách chalkogenidů - chalkogenidových skel, slitin s fázovými změnami a dichalkogenidů přechodných kovů - se zaměřením na vztah mezi strukturní metastabilitou a povahou chemické vazby. Zatímco přítomnost volných elektronových párů v chalkogenidových sklech umožňuje řadu procesů přepínání vazeb, existence rezonanční (metavalentní) vazby ve slitinách s rychlou fázovou přeměnou je klíčovým faktorem k transformaci mezi krystalickým a amorfním stavem. Silné kovalentní vazby ve 2D dichalkogenidech přechodných kovů omezují transformaci mezi rovnými a “cik-cak” atomovými rovinami bez většího prasknutí vazeb. Navrhujeme, že kombinace různých druhů lokálních vazeb může být účinným způsobem, jak připravit amorfní chalkogenidy s požadovanými vlastnostmi.

The self-organized 1D TiO2 nanotubular layers have attracted considerable scientific and technological interest over the past two decades, all motivated by a great performance in the range of applications including photo-catalysis, solar cells, hydrogen generation and biomedical uses [1,2]. The synthesis of these nanotubular layers has been carried out by a conventional electrochemical anodization of Ti sheet. Except the 1D character, these nanotubes possess unique features such as tunable dimensionality, structural flexibility, unidirectional electron transport through nanotube walls, chemical and mechanical stability and biocompatibility. One of the major application targets of TiO2 nanotubes has been their utilization as scaffolds or templates for deposition of secondary materials towards new applications [3]. In particular, for the photoelectrochemical applications (e.g. photovoltaics) ordered nanostructures, such as self-organized TiO2 nanotubes, offer the advantage of directed charge transport and controlled phase separation between the donor and acceptor materials, unlike within randomly ordered mesoporous TiO2 supports. Numerous techniques were utilized for this purpose, such as for example hydrothermal routes, electrodeposition or Atomic Layer Deposition (ALD) techniques. Electrodeposition is very powerful technique to deposit metals [4], oxides [5] or other rather complex materials (such as CuInSe2 [6]) within the nanotubes various by means of complete filling or decoration with. On the other hand, ALD can deposit the widest range of secondary materials within TiO2 nanotubes by means of homogenous coatings [7-10]. ALD is the only technique of choice to coat in particular high-aspect ratio nanotube layers. Overall, the deposited materials influence strongly photo-electrochemical properties of nanotube layers. The presentation will be focused in detail on TiO2 nanotube layers of various aspect ratios filled, decorated or coated by various chalcogenide-based materials using electrodeposition and ALD. Experimental details and some very recent photo-electrochemical and structural characterizations of a new type of heterostructured photo-chemical cell will be presented and discussed. References 1] J.M. Macak et al., Curr. Opin. Solid State Mater. Sci., 2007 , 1-2, 3-17. 2] K.Lee, A. Mazare, P. Schmuki, Chem. Rev., 2014, 114, 9385-9454. 3] J.M. Macak, Chapter 3 in: D. Losic and A. Santos, Electrochemically Engineered Nanoporous Structures, Springer International Publishing, Switzerland, 2015 4] J. M. Macak, B.G. Gong, M. Hueppe, P. Schmuki, Adv. Mater., 2007, 19, 3027. 5] L. Wu & G. Zangari, J. Phys. Chem. C, 2010, 114, 1155 6] S. Das & J. M. Macak et al., ChemElectroChem, 2017, 4, 495 7] R. Zazpe et al, Langmuir, 2016, 32, 10551 8] S. Ng et al., Adv. Eng. Mater., DOI: 10.1002/adem.201700589 9] R.Zazpe et al., Nanoscale, 2018, 10, 16601-16612. 10] F. Dvorak et al., Appl. Mater. Today, 2019 , 14, 1-20.

Anodic TiO2 nanotube layers (TNTs) of different thicknesses (≈1, 5 and 20 µm) were homogeneously decorated with Pt nanoparticles using atomic layer deposition (ALD) and explored for the electrocatalytic activity in methanol oxidation reaction (MOR). Six different numbers of ALD cycles (NALD) – 24, 40, 56, 72, 88 and 104 – were used. Pt nanoparticles with diameter in the range of 1.3–4.6 nm were obtained for the first five NALD and a complete coating was achieved for the highest NALD (1 0 4). The SEM/TEM analyses revealed that Pt nanoparticles uniformly decorated exteriors and interiors of TNTs. A linear increase of the particle diameter of Pt was observed with increasing NALD. Highest electrocatalytic activities of Pt/TNTs electrodes represented by current density of 74 mA/cm2 were obtained for NALD = 88 and for thickest TNTs (20 µm). The electrooxidation performance of Pt-decorated TiO2 nanotube layers was thoroughly compared to reference substrates: Pt-decorated graphite sheets and TiO2 flat layers (on annealed Ti foils) as well as for a commercial Pt/C catalyst attached on graphite sheets. From chronoamperometric measurements it turned out that the catalytic activity of Pt-loaded nanotube layers is superior and long lasting compared to other substrates, where significant degree of catalyst poisoning takes place. The presented ALD decoration approach is an effective strategy for the homogeneous distribution of precious Pt nanoparticles on a high surface area catalyst support for high-performance electrocatalysis.

We demonstrate that pressure-induced amorphization in Ge–Sb–Te alloys across the ferroelectric–paraelectric transition can be represented as a mixture of coherently distorted rhombohedral Ge8Sb2Te11 and randomly distorted cubic Ge4Sb2Te7 and high-temperature Ge8Sb2Te11 phases. While coherent distortion in Ge8Sb2Te11 does not prevent the crystalline state from collapsing into its amorphous counterpart in a similar manner to pure GeTe, the pressure-amorphized Ge8Sb2Te11 phase begins to revert to the crystalline cubic phase at ∼9 GPa in contrast to Ge4Sb2Te7, which remains amorphous under ambient conditions when gradually decompressed from 40 GPa. Moreover, experimentally, it was observed that pressure-induced amorphization in Ge8Sb2Te11 is a temperature-dependent process. Ge8Sb2Te11 transforms into the amorphous phase at ∼27.5 and 25.2 GPa at room temperature and 408 K, respectively, and completely amorphizes at 32 GPa at 408 K, while some crystalline texture could be seen until 38 GPa (the last measurement...

Phase-change memories are usually associated with GeTe-${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ quasibinary alloys, where the large optical contrast between the crystalline and amorphous phases is attributed to the formation of resonant bonds in the crystalline phase, which has a rocksalt-like structure. The recent findings that tetrahedrally bonded ${\mathrm{Ga}}_{2}{\mathrm{Te}}_{3}$ possesses a similarly large property contrast and very low thermal conductivity in the crystalline phase and undergoes low-energy switching [H. Zhu et al., Appl. Phys. Lett. 97, 083504 (2010); K. Kurosaki et al., Appl. Phys. Lett. 93, 012101 (2008)] challenge the existing paradigm. In this work we report on the local structure of the crystalline and amorphous phases of ${\mathrm{Ga}}_{2}{\mathrm{Te}}_{3}$ obtained from x-ray absorption measurements and ab initio simulations. Based on the obtained results, a model of phase change in ${\mathrm{Ga}}_{2}{\mathrm{Te}}_{3}$ is proposed. We argue that efficient switching in ${\mathrm{Ga}}_{2}{\mathrm{Te}}_{3}$ is due to the presence of primary and secondary bonding in the crystalline phase originating from the high concentration of Ga vacancies, whereas the structural stability of both phases is ensured by polyvalency of Te atoms due to the presence of lone-pair electrons and the formation of like-atom bonds in the amorphous phase.

The synthesis of highly-ordered nanostructures of valve metal oxides has recently attracted huge scientific and technological interest motivated by their possible use in many applications. The most established member of this group of materials is nanoporous Al2O3, which has been prepared two decades ago by anodic oxidation of Al into perfectly ordered, honeycomb-like porous structures employing suitable electrochemical conditions [1]. Owing to the flexibility of the pore diameter/length and the relative ease of the Al2O3 dissolution, its porous membranes have been since than widely used as template material of choice for a range of materials [2-4]. Self-organized TiO2 nanotube layers have received the highest attention after Al2O3 motivated by its range of applications, including photocatalysis, water splitting, solar cells and biomedical uses. Very significant research efforts have led to reproducible synthesis of self-organized TiO2 nanotube layers by means of anodic oxidation, during which the starting Ti substrate is converted into a highly-ordered nanotubular layer by anodization in suitable electrolytes [5-8]. Many new applications can be derived upon modification of the nanotubes by decoration, filling or coating by secondary materials [9]. Atomic layer deposition (ALD) has been shown to be an effective technique to coat TiO2 nanotube layers homogenously with secondary materials or to decorate them with noble metals [9]. The resulting structures offer many advantages and opportunities in various applications. TiO2 nanotubes in particular appeal as highly ordered electron-conductive supports for noble metal particles. This presentation will focus in detail on the decoration of the nanotube layers of different aspect ratios by noble metals using ALD. We will show and discuss our recent catalytic results on water splitting [10] and electrocatalytic results on the oxidation of methanol [11]. References: H. Masuda, K. Fukuda, Science, 268 (1995) 1466. K. Nielsch, F. Müller, A.-P. Li, U. Gösele, Adv. Mater. 12 (2000) 582. H. Asoh et al., J. Electrochem.Soc. 148 (2001) B152. J. Kolar, J. M. Macak, K. Terabe, T. Wagner, J. Mater. Chem. C, 2 (2014) 349. J. M. Macak, H. Tsuchiya, P. Schmuki, Angew. Chem. Int. Ed. 44 (2005) 2100. J.M. Macak et al., Curr. Opin. Solid State Mater. Sci. 1-2 (2007) 3. K. Lee, A. Mazare, P. Schmuki, Chem. Rev. 114 (2014) 9385. J.M. Macak, S. P. Albu, P. Schmuki, Phys. Stat. Sol. (RRL) 1 (2007) 181. F. Dvorak et al., Appl. Mater. Today 14 (2019) 1. J. Yoo et al., Electrochem. Commun. 86 (2018) 6. V.C. Anitha et al., J. Catal. 365 (2018) 86.

The success of graphene opened a door for a new class of chalcogenide materials with unique properties that can be applied in the semiconductor technology [1]. Monolayers of two-dimensional transition metal dichalcogenides (2D TMDCs) possess a direct band gap [2] that is crucial for optoelectronic applications. Additionally, the direct band gap can be easily tuned by either chemical composition or external stimuli. Next to the optoelectronic applications, where a monolayer planar structure is necessary to employ, a layer of standing flakes, which possesses a large surface area, can be used for hydrogen evolution [3] a photodegradation of organic dyes [4] or as electrodes in Li ion batteries [5]. In principle, TMDCs can be prepared by various top-down (e.g. exfoliation) and bottom-up techniques, such as chemical vapor deposition (CVD) and atomic layer deposition (ALD) growth techniques [1]. MoS2, a typical representative of TMDCs, has been widely studied for many applications. Recently, the possibility to employ ALD as a technique to grow MoS2 has been reported. In these works (CH3)2S2 [6] or H2S [7, 8] were used as the S precursor and Mo(CO)6 [6], MoCl5 [7] or Mo(thd)3 [8] as the Mo precursors. From the practical point of view, MoSe2 is even more interesting than MoS2 since MoSe2 possesses a higher electrical conductivity than MoS2 [9, 10]. Recently, we have shown that ALD deposition of MoSe2 [11] or Mo-O-Se [12] using ((CH3)3Si)2Se as the Se precursor and the MoCl5 or Mo(CO)6, respectively, as the Mo precursors is feasible. The presentation will focus on the synthesis of MoS2 and MoSe2 by ALD, their characterization and applications in various fields. Experimental details and some recent results for photocatalytic, battery and hydrogen evolution applications will be presented and discussed. References: [1] A. V. Kolobov, J. Tominaga, Two-Dimensional Transition-Metal, Dichalcogenides. Springer Series in Materials Science, Springer International Publishing AG, Switzerland 2016 [2] B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, A. Kis, Nat. Nanotechnol. 2011, 6, 147. [3] L. Wang, Z. Sofer, J. Luxa, M. Pumera, Adv. Mater. Interfaces 2015, 2, 1500041 [4] Y. Wu, M. Xu, X. Chen, S. Yang, H. Wu, J. Pan, X. Xiong, Nanoscale 2016, 8, 440 [5] D. Ilic, K. Wiesener, W. Schneider, H. Oppermann, G. Krabbes, J.Power Sources 1985, 14, 223 [6] Z. Jin, S.Shin,D.H.Kwon, S. J.Han,Y. S.Min,Nanoscale 2014, 6, 14453. [7] L. K. Tan, B. Liu, J. H. Teng, S. Guo, H. Y. Low, K. P. Loh, Nanoscale 2014, 6, 10584 [8] M. Mattinen et al., Adv. Mater. Interfaces 2017, 4, 1700123. [9] D. Kong, H. Wang, J. J. Cha, M. Pasta, K. J. Koski, J. Yao, Y. Cui, Nano Lett. 2013, 13, 1341. [10] A. Eftekhari, Appl. Mater. Today 2017, 8. [11] M. Krbal et al., Phys. Stat. Sol. RRL, 2018, 12, 1800023 [12] S. Ng et al., Adv. Mater. Interfaces 2017, 1701146.

The self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest over the past 13 years motivated by their possible range of applications including photocatalysis, solar cells, hydrogen generation and biomedical uses [1,2]. The synthesis of these 1D TiO2 nanotube layers is carried out by a conventional electrochemical anodization of valve Ti metal sheet. Among other TiO2 nanomaterials, these nanotube layers stand out due to their directionality, tunability of dimensions, ability to absorb significant amount of incident light and the possibility to utilize nanotube interiors and exteriors for decoration-coating of secondary materials. One of the most significant applications of TiO2 nanomaterials is photocatalysis, which is very effective to decompose various pollutants (e.g. dyes) and kill bacteria [3,4]. The presentation will focus on the utilization of the nanotube layer for photocatalytic removal of various species in the liquid phase [5, 6] as well as gas phase [7]. We will also show that various secondary materials have a positive influence on photo-electrochemical properties of nanotube layers [8, 9]. Experimental details and some recent photocatalytic results will be presented and discussed. References: [1] J. M. Macak et al., Curr. Opin. Solid State Mater. Sci., 2007, 1-2, 3. [2] K. Lee et al., Chem. Rev., 2014, 114, 9385. [3] K. Rajeshwar et al., J. Photochem. Photobiol. C: Photochem. Rev. 2008, 9, 171. [4] Ch. Wei et al., Environ.Sci. Technol. 1994, 28, 934. [5] J.M. Macak et al., Small, 2007, 3, 300. [6] H. Sopha et al., Appl. Mater. Today, 2017, 9, 104. [7] H. Sopha et al., Electrochem. Commun., 2018, 97, 91. [8] S. Ng et al., Adv. Mater. Interfaces 2017, 1701146. [9] F. Dvorak et al., Appl. Mater. Today, 2019, 14, 1.

Anodic self‐organized TiO2 nanotube layers (with different aspect ratios) were electrochemically infilled with CuInSe2 nanocrystals with the aim to prepare heterostructures with a photoelectrochemical response in the visible light. The resulting heterostructure assembly was confirmed by field‐emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). High incident photon‐to‐electron conversion efficiency values exceeding 55% were obtained in the visible‐light region. The resulting heterostructures show promise as a candidate for solid‐state solar cells.

We report on the photoelectrochemical and terahertz measurements, of the charge transport properties of 1 μm thick self-organized TiO2 nanotube layers, prepared by the anodization of titanium. We provide evidence regarding the complexity of electron transport, and dynamics in the nanotubes. Shortly after photoexcitation, charge mobilites in amorphous and crystalline nanotubes are similar, but still lower compared to the bulk anatase. The mobility subsequently decreases due to trapping-detrapping processes. The recombination rate in anatase nanotubes is much slower than in the amorphous ones, enabling the material to reach an internal photon to electron conversion efficiency exceeding 60%.

Disorder in the amorphous state of phase-change alloys has been a focus of much research, however, more recently it has become clear that there is significant temperature activated disorder in the crystalline phases that may have important implications for electrical transport. We explore order on different length scales using a variety of techniques. Bragg diffraction (BD) to determine average order, X-ray absorption to analyze order on nearest neighbor length scales, and total scattering to investigate structure on intermediate length scales. We find that Ge-rich phase-change alloys lying along the technological important (GeTe)x–(Sb2Te3)1 − x pseudobinary tie line exhibit a ferroelectric transition at a Curie temperature Tc from rhombohedral to cubic symmetry using BD while short-range order probes such as X-ray absorption spectroscopy indicate that local rhombohedral symmetry is maintained. Using total X-ray scattering, we demonstrate that this apparent discrepancy can be resolved by the introduction of disorder on intermediate length scales using a simple model.

While it is generally believed that the role of light in phase-change process is simply to heat the material, we demonstrate that amorphisation process in both phase-change materials and chalcogenide glasses can proceed without going through the liquid phase. We discuss the crucial role that resonant bonding and bonding energy hierarchy play in athermal amorphisation.