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Multiple thick film samples of the AgcPd1-c solid solution were prepared using physical vapour deposition over a borosilicate glass substrate. This synthesis technique allows continuous variation in stoichiometry, while the distribution of silver or palladium atoms retains the arrangement into an on-average periodic lattice with smoothly varying unit cell parameters. The alloy concentration and geometry were measured over a set of sample points, respectively, via energy-dispersive X-ray spectroscopy and via X-ray diffraction. These results are compared with ab initio total energy and electronic structure calculations based on density functional theory, and using the coherent potential approximation for an effective medium description of disorder. The theoretically acquired lattice parameters appear in qualitative agreement with the measured trends. The numerical study of the Fermi surface also shows a variation in its topological features, which follow the change in silver concentration. These were related to the electrical resistivity of the AgcPd1-c alloy. The theoretically obtained variation exhibits a significant correlation with nonlinear changes in the resistivity as a function of composition. This combined experimental and theoretical study suggests the possibility of using resistivity measurements along concentration gradients as a way to gain some microscopic insight into the electronic structure of an alloy.

Background: Tooth cementum covers the surface of the root dentine and is produced and laid down in thin layers continuously throughout life. Functionally, different types of tooth cementum can be distinguished, which can be roughly divided into acellular (primary cementum) and cellular (secondary cementum) forms. One main type is acellular extrinsic fibre cementum (AEFC), which covers the cervical and middle third of the root. Light microscopic examinations of transverse sections of AEFC show lamellar patterns of alternating light and dark lines called growth or incremental lines. Following mammalian research, a seasonal rhythm of incremental line formation is also assumed in humans. Previous attempts at visualising incremental lines in the AEFC by scanning electron microscopy (SEM) were not particularly successful. The aim of the present study was to detect incremental lines in the AEFC and to analyse their underlying structure by SEM., Methods: For this purpose, non-embedded and resin-embedded transverse and longitudinal sections of three single-rooted teeth obtained from different patients were investigated. The thin sections were not pre-treated (e.g. by etching, grinding or coating)., Results: Lamellar structures, which could be identified as incremental lines, were detectable in both transverse and longitudinal sections, with transverse orientation in the cross-section and longitudinal orientation in the longitudinal section. The lamellar pattern was created by broad fibre-rich layers alternating with narrow fibre-poor layers. The orientation of the collagen fibres changed from layer to layer from transverse to radial direction. The visibility of the layered structure discovered varied significantly., Conclusions: The study demonstrate that it is possible, in principle, to detect incremental lines in AEFC and to identify their basic structure using SEM. Our results suggest that the density and orientation of the fibres play an essential role in the formation of incremental lines. Functional aspects seem to be of particular importance., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier GmbH. All rights reserved.)

We set out to demonstrate the development of a highly conductive polymer based on poly-(3,4-ethylenedithia thiophene) (PEDTT), PEDOTs structural analogue historically notorious for structural disorder and limited conductivities. The caveat therein was previously described to lie in intra-molecular repulsions. We demonstrate how a tremendous >2600-fold improvement in conductivity and metallic features, such as magnetoconductivity can be achieved. This is achieved through a careful choice of the counter-ion (sulphate) and the use of oxidative chemical vapour deposition (oCVD). It is shown that high structural order on the molecular level was established and the formation of crystallites tens of nanometres in size was achieved. We infer that the sulphate ions therein intercalate between the polymer chains, thus forming densely packed crystals of planar molecules with extended π-systems. Consequently, room-temperature conductivities of above 1000 S cm -1 are achieved, challenging those of conventional PEDOT:PSS. The material is in the critical regime of the metal-insulator transition., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

Composite memristors based on anodic oxidation of Hf superimposed on Ta thin films are studied. A layered structure is obtained by successive sputtering of Ta and Hf thin films. The deposition geometry ensured components' thickness gradient profiles (wedges) aligned in opposite directions. Anodization in citrate buffer electrolyte leads to a nanoscale columnar structuring of Ta 2 O 5 in HfO 2 due to the higher electrical resistance of the latter. Following the less resistive path, the ionic current forces Ta oxide to locally grow toward the electrolyte interface according to the Rayleigh-Taylor principle. The obtained composite oxide memristive properties are studied as a function of the Hf/Ta thickness ratio. One pronounced zone prominent for memristive applications is found for ratios between 4 and 5. Here, unipolar and bipolar memristors are found, with remarkable endurance and retention capabilities. This is discussed in the frame of conductive filament formation preferentially along the interfaces between oxides.

Anodic HfO 2 memristors grown in phosphate, borate, or citrate electrolytes and formed on sputtered Hf with Pt top electrodes are characterized at fundamental and device levels. The incorporation of electrolyte species deep into anodic memristors concomitant with HfO 2 crystalline structure conservation is demonstrated by elemental analysis and atomic scale imaging. Upon electroforming, retention and endurance tests are performed on memristors. The use of borate results in the weakest memristive performance while the citrate demonstrates clear superior memristive properties with multilevel switching capabilities and high read/write cycling in the range of 10 6 . Low temperature heating applied to memristors shows a direct influence on their behavior mainly due to surface release of water. Citrate-based memristors show remarkable properties independent on device operation temperatures up to 100 °C. The switching dynamic of anodic HfO 2 memristors is discussed by analyzing high resolution transmission electron microscope images. Full and partial conductive filaments are visualized, and apart from their modeling, a concurrency of filaments is additionally observed. This is responsible for the multilevel switching mechanism in HfO 2 and is related to device failure mechanisms.

Wide range binary and ternary thin film combinatorial libraries mixing Al, Cu, and Ga were screened for identifying alloys with enhanced ability to withstand electromigration. Bidimensional test wires were obtained by lithographically patterning the substrates before simultaneous vacuum co-deposition from independent sources. Current-voltage measurement automation allowed for high throughput experimentation, revealing the maximum current density and voltage at the electrical failure threshold for each alloy. The grain boundary dynamic during electromigration is attributed to the resultant between the force corresponding to the electron flux density and the one corresponding to the atomic concentration gradient perpendicular to the current flow direction. The screening identifies Al-8 at. % Ga and Cu-5 at. % Ga for replacing pure Al or Cu connecting lines in high current/power electronics. Both alloys were deposited on polyethylene naphthalate (PEN) flexible substrates. The film adhesion to PEN is enhanced by alloying Al or Cu with Ga. Electrical testing demonstrated that Al-8 at. % Ga is more suitable for conducting lines in flexible electronics, showing an almost 50% increase in electromigration suppression when compared to pure Al. Moreover, Cu-5 at. % Ga showed superior properties as compared to pure Cu on both SiO 2 and PEN substrates, where more than 100% increase in maximum current density was identified.

In this work, we show that intramolecular hydrogen bonding can be used to stabilize tri-coordinated phosphane-gold(I) complexes. Two molecular structures of 2-(diphenylphosphino)benzoic acid (L) coordinated to a gold(I) atom were determined by single-crystal X-ray diffraction. The linear L-Au-Br shows a standard linear coordination and dimerizes via hydrogen bonds of the carboxylic acid. Upon addition of two additional phosphane ligands the complex [L 3 Au]X is formed which is stabilized by three intramolecular -C(O)O-H … X hydrogen bonds as proven by the X-ray structure of the respective chlorido-complex. X-ray powder diffractograms suggest the same structure also for X -  = Br - and I - ., Supplementary Information: The online version contains supplementary material available at 10.1007/s00706-021-02843-2., (© The Author(s) 2021.)

The electrochemical behavior of a tungsten trioxide-nickel oxide (WO 3 -NiO) thin film library was investigated using scanning droplet cell microscopy (SDCM) in 0.1 mol dm -3 sodium perchlorate (NaClO 4 ) solution. The WO 3 -Ni film library was deposited by thermal coevaporation on an indium tin oxide (ITO)-coated glass substrate in an atomic Ni concentration range from 2.8 to 15.6 at. %. After an oxidation/crystallization heat treatment, the Ni was oxidized and the crystal structure of WO 3 -NiO was transformed from monoclinic WO 3 (3.5 at. % Ni) to cubic WO 3 (up to 7.1 at. % Ni) and again to monoclinic WO 3 when the Ni amount increased (>11.8 at. %). Proton (H + ) intercalation (cathodic reaction) and deintercalation (anodic reaction) into the WO 3 -NiO mixed phases was induced. Electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) analysis revealed that the WO 3 -NiO film has n-type bilayer capacitive property, with the outer capacitive layer having a higher defect density than the inner capacitive layer. With a Ni concentration of 7.1 at. %, the WO 3 -NiO film was the most defective in the library. Introduction of the Ni cation into the WO 3 network was associated with changes of the semiconducting properties of the film.

Doped ZnO thin films on ITO substrates were prepared by reactive co-sputtering of ZnO and several dopant metals, namely Al, Mn, Ti, W or Zr. To elucidate the influence of the dopant, morphological and compositional investigations were performed applying SEM/EDX, XRD and AFM. The optical band gaps of the materials were determined by UV-VIS measurements and the subsequent analysis of the derived Tauc plots. SKP (Scanning Kelvin Probe) measurements were performed under alternating illumination periods in order to measure the CPD (contact potential difference) response on UV irradiation; effective donor concentrations were calculated from the SKP results. The obtained X-ray diffractograms revealed that W : ZnO is amorphous, whereas all other dopants form crystalline structures with diffraction angles shifted towards lower values. SEM and AFM imaging revealed a significant influence of the dopant on the film morphology. The optical band gap values are in the range of the ZnO value (∼3.30 eV), with the lowest value of 3.29 eV being measured for Mn : ZnO. An exception was found for W : ZnO, which exhibits significant band gap widening reaching 4.35 eV. The effective donor concentrations are low for all samples under dark conditions, whereas they showed enhanced values under illumination. The sensitivity of all materials towards illumination makes them promising candidates for future research activities in the field of photovoltaics., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

This communication is focused on the synthesis, characterization and experimental proof of the mechanism of antimicrobial activity of powders from the molybdenum-tungsten-oxygen (Mo-W-O) system. Materials with a discrete ratio of Mo/W ranging from 100% MoO 3 to 100% WO 3 with a stepwise increase of 5-10 wt % W were synthesized by the spray drying method following calcination. Spherical hollow particles with a broad size distribution were formed and the composition influenced the crystalline phases in such a way that either pure and/or mixed oxides (Mo 0.6 W 0.4 O 3 ) were obtained. A good correlation between composition variation and phases present on the antimicrobial activity is obtained and provides a detailed screening of the activity efficiency versus compositional transition. Antimicrobial tests were performed against a model Gram-negative bacterium ( Escherichia coli ). Furthermore, the mechanism of antimicrobial activity is proven by correlating the medium acidification via pH measurements to the bacteria lifespan at low pH values. The mechanism is additionally supported by the bacterial growth when a buffered nutrient medium was used, together with the evidence that the powder particles have no disruptive effect on the cell wall. Consequently, an extended mechanism is proposed for the mixed oxide, relating both the structure and solubility results. Solubility measurements displayed a steep decrease in metal ions concentration with the addition of W. A narrow compositional range was identified (80 to 60 wt % Mo) where the antimicrobial activity was present, which is concurrent with a very strong decrease in solubility. Materials within this range show adequate features for being implemented into hybrid systems consisting of inorganic materials-polymers/varnishes that can be used for touch surfaces in healthcare settings.

Camptothecin (CPT), a potent anticancer drug with known antiviral activity, is halted of clinical use. Few drug delivery systems of CPT are approved for therapy. Hereby, we propose the encapsulation of hydrophobic CPT in the inner core of cellulose nanoaggregates for sustained release with retaining of antiproliferative activity. Cellulose conjugates were synthesized by esterification of methyl cellulose, hydroxyethyl cellulose and (hydroxypropyl)methyl cellulose with testosterone, ergocalciferol and dl-α-tocopherol hemisuccinates. The degree of substitution attained ranged from 0.004 to 0.025 and no depolymerization was observed by size exclusion chromatography. ATR-FTIR and NMR spectroscopies confirmed grafting of testosterone and vitamins to celluloses. According to dynamic light scattering, it resulted in their self-assembly in aqueous medium as stable and slightly negatively charged nanoaggregates of 213 to 731 nm. Nanoaggregates formation was also assessed using transmission electron and atomic force microscopies. CPT was encapsulated in the cellulose nanoaggregates, achieving a content of 1.7-13.0 wt %. Sustained release of camptothecin over 150 h was observed in simulated physiological conditions. CPT-loaded cellulose nanoparticles appeared to be possible candidates for chemotherapy, according to observed cytotoxicity against MCF-7 cancer cells., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A thin film combinatorial library deposited by co-sputtering of Hf, Nb and Ta was employed to characterise fundamental properties of the Hf-Nb-Ta system. Compositional mappings of microstructure and crystallography revealed similarities in alloy evolution. Distinct lattice distortion was observed upon addition of hexagonal Hf, leading to amorphisation of alloys containing more than 32 at.% Hf and less than 27 and 41 at.% Nb and Ta, respectively. Volta potential and open circuit potential mappings indicated minimal values for the highest Hf concentration. Localised anodisation of the library by scanning droplet cell microscopy revealed valve metal behaviour. Oxide formation factors above 2 nm V -1 were identified in compositional zones with high amounts of Nb and Ta. Fitting of electrochemical impedance spectroscopy data allowed electrical permittivity and resistivity of mixed oxides to be mapped. Their compositional behaviours were attributed to characteristics of the parent metal alloys and particularities of the pure oxides. Mott-Schottky analysis suggested n-type semiconductor properties for all Hf-Nb-Ta oxides studied. Donor density and flat-band potential were mapped compositionally, and their variations were found to be related mainly to the Nb amount. Synergetic effects were identified in mappings of Hf-Nb-Ta parent metals and their anodic oxides.

Developing novel compounds with antimicrobial properties can be an effective approach to decreasing the number of healthcare-associated infections, particularly in the context of medical devices and touch surfaces. A variety of molybdate powders (Ag 2 MoO 4 , CaMoO 4 , CuMoO 4 and Cu 3 Mo 2 O 9 ) were synthesized and characterized, and Escherichia coli was used as a model gram-negative bacterium to demonstrate their antimicrobial properties. Optical density measurements, bacterial colony growth, and stained gel images for protein expression clearly showed that silver- and copper molybdates inhibit bacterial growth, whereas CaMoO 4 exhibited no bactericidal effect. All tests were performed in both daylight and darkness to assess the possible contribution of a photocatalytic effect on the activity observed. The main mechanism responsible for the antibacterial effect observed for Ag 2 MoO 4 is related to Ag + release in combination with medium acidification, whereas for compounds containing copper, leaching of Cu 2+ ions is proposed. All these effects are known to cause damage at the cellular level. A photocatalytic contribution to the antibacterial activity was not clearly observable. Based on the pH and solubility measurements performed for powders in contact with various media (ultrapure water and bacterial growth medium), silver molybdate (Ag 2 MoO 4 ) was identified as the best antibacterial candidate. This compound has great potential for further use in hybrid powder-polymer/varnish systems for touch surfaces in healthcare settings.

Optical bandgap mapping of Nb-Ti mixed oxides anodically grown on a thin film parent metallic combinatorial library was performed via variable angle spectroscopic ellipsometry (VASE). A wide Nb-Ti compositional spread ranging from Nb-90 at.% Ti to Nb-15 at.% Ti deposited by cosputtering was used for this purpose. The Nb-Ti library was stepwise anodized at potentials up to 10 V SHE, and the anodic oxides optical properties were mapped along the Nb-Ti library with 2 at.% resolution. The surface dissimilarities along the Nb-Ti compositional gradient were minimized by tuning the deposition parameters, thus allowing a description of the mixed Nb-Ti oxides based on a single Tauc-Lorentz oscillator for data fitting. Mapping of the Nb-Ti oxides optical bandgap along the entire compositional spread showed a clear deviation from the linear model based on mixing individual Nb and Ti electronegativities proportional to their atomic fractions. This is attributed to the strong amorphization and an in-depth compositional gradient of the mixed oxides. A systematic optical bandgap decrease toward values as low as 2.0 eV was identified at approximately 50 at.% Nb. Mixing of Nb 2 O 5 and TiO 2 with both amorphous and crystalline phases is concluded, whereas the possibility of complex Nb a Ti b O y oxide formation during anodization is unlikely.

A combinatorial thin film material library from the molybdenum-tungsten refractory metals oxides system was prepared by thermal coevaporation, and its structural and morphological properties were investigated after a multiple step heat treatment. A mixture of crystalline and amorphous oxides and suboxides was obtained, as well as surface structuring caused by the enrichment of molybdenum oxides in large grains. It was found that the oxide phases and the surface morphology change as a function of the compositional gradient. Tests of the library antimicrobial activity against E. coli were performed and the antimicrobial activity was proven in some defined compositional ranges. A mechanism for explaining the observed activity is proposed, involving a collective contribution from (i) increased local acidity due to the enrichment in large grains of molybdenum oxides with different stoichiometry and (ii) the release of free radicals from the W18O49 phase under visible light.