Three-dimensional (3D) fibrous networks based on metal oxides were obtained by a bio-inspired approach: the replication of an ecological daily-waste, the eggshell membrane (ESM). The biomorphic ...process consists in the immersion of the ESM into aqueous solutions containing the metal salt precursors followed by the calcination of the metal ions impregnated ESM. Biomorphic ZnO, CuO and ZnO–CuO composite networks were obtained, their morphological, structural, compositional, optical, photocatalytical and electrical properties being evaluated. The scanning electron microscopy investigations proved that the hierarchical structure of the original organic template is perfectly replicated into inorganic architectures consisting of interconnected fibers containing metal oxide nanoparticles as building blocks. The photocatalytical properties of the metal oxide networks under solar simulator irradiation were tested through the degradation of methylene blue. Using Si/SiO2 patterned with interdigitated metallic electrodes as substrates during the calcination step, the electrical properties of the self-contacted metal oxide networks were investigated. Thus, by replicating the unique architecture of the ESM, 3D metal oxide interwoven meshwork can be easily developed for various applications in fields such as photocatalysis, sensing, optoelectronic devices, etc.
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•3D fibrous networks based on ZnO, CuO and ZnO–CuO were obtained by replicating the eggshell membranes.•Networks were formed by interconnected fibers containing metal oxide nanoparticles as building blocks.•Metal oxide networks were featured by the typical structure and optical signatures of the two components.•Biomorphic networks induce the MB photodegradation under solar simulation irradiation.•I–V properties of the self-contacted networks were studied using Ti/Pt interdigitated electrodes.
Potassium hydrogen phthalate (KAP) crystals doped with rhodamine 6G (Rh 6G) and polyvinylpyrrolidone (PVP) were grown by solution evaporation technique. Nucleation occurred without the use of seeds ...and optically transparent crystals were obtained. The grown crystals were characterized by XRD measurements performed on crystals and their powders, optical transmission and photoluminescence measurements. The influence of the dopants on the structural, morphological and optical properties of the KAP crystals was analysed. Dopants do not change the structure of the single crystals while the addition of PVP changes the morphology of crystals from pseudo-hexagonal to rhomb. Three new XRD reflections are observed in all single-crystal and powder XRD spectra and are probably (0
3
0), (0
4
0) and (0
5
0) lines. The UV cut-off and transparency of the crystals are not changed by doping. Dye-doped KAP crystals exhibit a strong emission band centred at 550
nm excited with 480
nm wavelength. For the dye-doped crystals the up-conversion was investigated and its second harmonic origins are proved using photoluminescence measurements.
The influence of the partial substitution of Fe by Si and thermal treatments on the structural, magnetic and magnetostrictive properties of the Fe
67.5
Pd
30.5
Si
2
rapidly solidified ribbons has ...been investigated. A remarkable decrease in the martensite transformation temperature, with ~ 65 K lower than that of the Fe–Pd archetype alloy, is observed in the as-prepared ribbons. The thermal treatments shift the martensite transformation temperatures upward, with approximately 13 K for the higher thermal treatment. Also, these induce an improvement in the crystallinity in these ribbons with high texture and an increase in the crystallite size as a result of reducing the internal defects and stress. The thermodynamic considerations discussed in the frame of the Clapeyron–Clausius relation by using the calorimetric and thermomagnetic measurements (up to 7 T) reveal a weak influence of the magnetic fields on the martensitic transformation temperatures (~ 0.5 K/T). The magnetostriction decrease with temperature under small magnetic fields was discussed, beside an unusual behaviour in the technically saturated domain. This behaviour is based on the coexistence of the ordinary and forced magnetostrictions, the last one increasing faster with the temperature decreasing.
Dye-doped polymer thin films were obtained by spin-coating of 8% polyvinylpyrrolidone (PVP) solutions (in ethanol). Ni or ZnO nanowires were incorporated in Rhodamine 6G doped polymer films (10−4M ...dye concentration). Optical and morphological properties of simple dye-doped polymer films and films containing metallic or semiconducting nanostructures were investigated. Optical microscopy and scanning electron microscopy were used to image the nanowires. The presence of Ni nanowires induces a small shift (2–3nm) to longer wavelengths on the emission band of Rh 6G doped PVP film. The ZnO nanowires' presence was confirmed by X-ray diffraction measurements. An enhancement of the emission of the dye doped polymer is induced by the semiconducting structures.
•Rhodamine 6G doped polyvinylpyrrolidone thin films were obtained by spin-coating.•Ni or ZnO nanowires were incorporated in Rhodamine 6G doped polymer films.•Ni nanowires' presence induces a shift to shorter wavelengths on the emission band.•Enhancement of dye-doped polymer emission induced by the semiconducting structures
Abstract
Three commercial powders of MgB
2
were tested in vitro by MTS and LDH cytotoxicity tests on the HS27 dermal cell line. Depending on powders, the toxicity concentrations were established in ...the range of 8.3–33.2 µg/ml. The powder with the lowest toxicity limit was embedded into polyvinylpyrrolidone (PVP), a biocompatible and biodegradable polymer, for two different concentrations. The self-replenishing MgB
2
-PVP composite materials were coated on substrate materials (plastic foil of the reservoir and silicon tubes) composing a commercial urinary catheter. The influence of the PVP-reference and MgB
2
-PVP novel coatings on the bacterial growth of
Staphylococcus aureus
ATCC 25923,
Enterococcus faecium
DMS 13590,
Escherichia coli
ATCC 25922,
Pseudomonas aeruginosa
ATCC 27853, in planktonic and biofilm state was assessed in vitro at 6, 24, and 48 h of incubation time. The MgB
2
-PVP coatings are efficient both against planktonic microbes and microbial biofilms. Results open promising applications for the use of MgB
2
in the design of anti-infective strategies for different biomedical devices and systems.
Mud and burnt Roman bricks from Romula Badica, P.; Alexandru-Dinu, A.; Grigoroscuta, M. A. ...
Scientific reports,
09/2022, Letnik:
12, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
Sesquipedalian mud and burnt bricks (second to third century AD) were excavated from the Roman city of Romula located in the Lower Danube Region (Olt county, Romania). Along with local ...soils, bricks are investigated by petrographic analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), electron microscopy (SEM/EDX), X-ray microtomography (XRT), thermal analysis (DTA-TG), Mӧssbauer spectroscopy, magnetometry, colorimetry, and mechanical properties assessment. The results correlate well with each other, being useful for conservation/restoration purposes and as reference data for other ceramic materials. Remarkably, our analysis and comparison with literature data indicate possible control and wise optimization by the ancient brickmakers through the recipe, design (size, shape, and micro/macrostructure), and technology of the desired physical–chemical–mechanical properties. We discuss the Roman bricks as materials that can adapt to external factors, similar, to some extent, to modern “smart” or “intelligent” materials. These features can explain their outstanding durability to changes of weather/climate and mechanical load.
ZnO crystallites were grown by electroless deposition on poly(methyl methacrylate) (PMMA) fiber mats prepared by an electrospinning technique. The electroless deposition involves three steps: ...sensitization, activation and deposition, which were performed by subsequently dipping the PMMA fiber mats in the appropriate solutions. After the deposition the PMMA fibers are uniformly coated with ZnO prisms which show hexagonal wurtzite structure and optical signatures (band-gap value and emission bands) typical for this semiconductor. By combining electroless deposition and electrospinning, different semiconductor coated polymer fibers can be obtained for a wide range of applications. Both methods are appropriate for large scale production, being scalable, cheap, efficient and suitable for large-area covering techniques.
•ZnO-coated PMMA fibers were prepared by combining two low cost and scalable techniques: electrospinning and electroless deposition.•PMMA fibers were uniformly coated with ZnO prisms shaped crystallites.•ZnO prisms show a hexagonal wurtzite structure and optical signatures typical for this semiconductor (band-gap value and emission bands).
Composites of magnetite (Fe3O4) nanoparticles dispersed in a polydimethylsiloxane (PDMS) matrix were prepared by a molding process. Two types of samples were obtained by free polymerization with ...randomly dispersed particles and by polymerization in an applied magnetic field. The magnetite nanoparticles were obtained from magnetic micrograins of acicular goethite (α-FeOOH) and spherical hematite (α-Fe2O3), as demonstrated by XRD measurements. The evaluation of morphological and compositional properties of the PDMS:Fe3O4 composites, performed by SEM and EDX, showed that the magnetic particles were uniformly distributed in the polymer matrix. Addition of magnetic dispersions promotes an increase of thermal conductivity compared with pristine PDMS, while further orienting the powders in a magnetic field during the polymerization process induces a decrease of the thermal conductivity compared with the un-oriented samples. The shape of the magnetic dispersions is an important factor, acicular dispersions providing a higher value for thermal conductivity compared with classic commercial powders with almost spherical shapes.
Abstract
Si and Ge nanocrystals in oxides are of a large interest for photo-effect applications due to the fine-tuning of the optical bandgap by quantum confinement in nanocrystals. In this work, ...dense Ge nanocrystals suitable for enhanced photoconduction were fabricated from 60% Ge in TiO
2
amorphous layers by low temperature rapid thermal annealing at 550 °C. An exponential increase of the photocurrent with the applied voltage was observed in coplanar structure of Ge nanocrystals composite films deposited on oxidized Si wafers. The behaviour was explained by field effect control of the Fermi level at the Ge nanocrystals-TiO
2
layer/substrate interfaces. The blue-shift of the absorption gap from bulk Ge value to 1.14 eV was evidenced in both photocurrent spectra and optical reflection-transmission experiments, in good agreement with quantum confinement induced bandgap broadening in Ge nanocrystal with sizes of about 5 nm as found from HRTEM and XRD investigations. A nonmonotonic spectral dependence of the refractive index is associated to the Ge nanocrystals formation. The nanocrystal morphology is also in good agreement with the Coulomb gap hopping mechanism of
T
–1/2
-type explaining the temperature dependence of the dark conduction.
This work involves the synthesis and characterization of Cu2ZnSnS4 (CZTS) layers. The films were prepared on ITO/glass substrate by ecofriendly and simple single-step electrodeposition method ...followed by sulfurization and annealing at 500 °C under Argon flow. By using two different complexing agents, the electrodeposition process can give better results. Therefore, the effect of combining the trisodium citrate - TC to multiple complexing agents (cetyl trimethyl ammonium bromide - CTAB, ethylene diamine tetra acetic acid - EDTA, Boric Acid - BA, Glutamic Acid - GA and Tartaric Acid - TA) is investigated. The characterization of the absorber films was done by X-ray diffraction (XRD) analysis, Raman spectroscopy, Scanning Electron Microscopy and Diffuse Reflectivity. The combination of TC and CTAB is suggested to be the best pair of complexing agents within the combinations used in this work.
•CZTS thin films were synthetized by electrodeposition using different combinations of complexing agents.•A nearly single tetragonal phase was obtained by combining trisodium citrate and cetyltrimethylammonium bromide (CTAB).•The CZTS-CTAB samples have the most homogenous morphology, being compact (without cracks) in the same time.•The band gaps range between 1.39 and 1.55 eV, fulfilling the absorber requirements for photovoltaic cells development.
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