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Electrochemical deposition of silicon at room temperature is problematic due to intrinsically low conductivity of the deposits. This study reports the photoelectrochemical (PEC) deposition of silicon (Si) and silicon–carbon (Si–C) layers from an ionic liquid at temperature 40 oC using silicon tetrachloride (SiCl4) as a silicon precursor. Amorphous layers are deposited on p-type silicon (p-Si), p-type gallium arsenide (p-GaAs), and aluminum–copper alloy AA2024. The semi-conductor substrates are activated by white LED illumination, which generated photoelectrons, thereby making the substrate conductive with respect to the cathodic reaction. Photoresponsive-ness of the deposits is proven by the light-induced photocurrents on an optically inactive substrate made of the alloy AA 2024. The proposed method paves the way for the electrochemical modifica-tion of semiconductors and metals with Si and Si–C structures, which are applicable in various fields, such as; batteries, anti-corrosion coatings, photovoltaics, or PEC electrodes for hydrogen production.

International audience; A series of highly flexible and environmentally friendly composites based on polydimethylsiloxane (PDMS) filled with 200 nm size ferroelectric BaTiO3 (BTO) particles at different concentrations (from 7 to 23 vol %) have been fabricated by a simple dispersion method. The dielectric, piezoelectric, and ultrasonic properties have been studied. The ferroelectric state of BTO was confirmed by differential scanning calorimetry and ultrasonic spectroscopy. The addition of BTO into PDMS strongly affects the dielectric properties of the composites. At low temperatures close to 160 K, the PDMS matrix exhibits a dielectric anomaly related to a dynamic glass transition, which shifts to higher temperatures as the BTO content increases due to the strong interaction between polymer chains and nanoparticles. Ultrasonic measurements demonstrate the appearance of a piezoelectricvoltage signal on a thin plate of the composite with the highest available filler concentration (23 vol %) under longitudinal stress applied by a 10 MHz ultrasonic wave. As a result, at room temperature, the detected signal is characterized by output voltage and specific stored energy values of 10 mV and 367.3 MeV/m2, respectively, followed by a further increase with cooling to 35 mV at 150K. The proposed BTO/PDMS composite system is thus a potential candidate for nanogenerators, namely, a simple, flexible, and lead-free device converting high-frequency (10 MHz) mechanical vibrations into electrical voltage.

Bulk polylactic acid (PLA)/multiwall carbon nanotube (MWCNT) composites were prepared and investigated in wide frequency ranges (20 Hz–1 MHz and 24–40 GHz). It was determined that the percolation threshold in bulk PLA/MWCNT composites is close to 0.2 vol.% MWCNT. However, the best microwave dielectric properties and absorption were observed in composites with 3.0–5.0 vol.% MWCNT. Therefore, for future investigations, we selected layered (laminate) polymeric structures with gradual changes in MWCNT concentration from 0.2 to 8.0 vol.% MWCNT. Two approaches to laminate structure designs were examined and compared: a five-layer composite and a nine-layer composite that included four pure PLA middle layers. The addition of MWCNT enhanced the elastic modulus by up to 1.4-fold and tensile strength by up to 1.2-fold, with the best performance achieved at 5.0 vol.% loading. High microwave shielding was observed for these layered PLA/MWCNT structures with a gradient change in MWCNT concentration (up to 26 dB in both transmission and absorption coefficients) in the broad frequency range (from 24 to 40 GHz). Obtained structures are highly anisotropic, and the absorption coefficient is 2–5 dB higher in the direction of MWCNT concentration increase; however, the transmission coefficient is the same in both directions. The properties of microwave absorption are mainly unaffected by the additional polymeric layers. The absorption of the layered structure is greater than the absorption of single-layer composites with an optimal MWCNT concentration of the same thickness. The proposed laminate structure design is promising in the field of efficient electromagnetic shielding.

Multilayered phosphate bonded CoFe2O4–BaTiO3–CoFe2O4 (CBC) and BaTiO3–CoFe2O4–BaTiO3 (BCB) multiferroic structures were formed by means of uniaxial pressing. The dielectric properties were studied in 20 Hz – 1 GHz frequency and 120–500 K temperature ranges. The complex dielectric permittivity is 15–0.17i for CBC and 22–0.04i for BCB, it is temperature- and frequency-independent below 250 K. At higher temperatures, strong dispersion appeared governed by the Maxwell–Wagner relaxation. Such behaviour is determined by the 2–2 connectivity of the sample. The highest direct magnetoelectric coupling coefficient was found for the BaTiO3–CoFe2O4–BaTiO3 structure of 0.2 mVOe–1cm–1.

Surface-enhanced Raman spectroscopy (SERS) substrates fabricated using a repeated laser treatment of thin gold films are demonstrated. The presented SERS substrates consist of the gold nanoparticles, whose density and size depend on the used film thickness and number of treated films. The larger number of the treated gold film layers increases the amount of larger nanoparticles (size >20 nm). However, a large number of small nanoparticles (5–20 nm) in all cases is also observed. The manufactured SERS substrates exhibit a high enhancement factor, which is in the range of 106. The enhancement factor can be increased by adding an additional Au coating on the top of nanoparticles generated from a single gold layer. The demonstrated laser-based fabrication approach of large-scale SERS substrates is simple, reliable, without the use of chemicals for the reduction and stabilization of nanoparticles, and cost-effective.

Here we report the optimization of the fabrication conditions for AuNi bimetallic catalysts supported on self-ordered titania nanotube arrays (AuNi-TiO2ntb). A series of efficient AuNi-TiO2ntb catalysts with small amounts of Au in the range of 1.74 to 15.7 μgAu·cm−2 have been fabricated by anodization, electroless Ni plating, and galvanic displacement techniques. The electrocatalytic activity of the catalysts has been evaluated for BH4− ion oxidation in an alkaline medium using cyclic voltammetry and chronoamperometry. The performance of a NaBH4-H2O2 fuel cell with Ni-TiO2ntb and AuNi-TiO2ntb anode catalysts has been investigated at different temperatures. It was found that the electrocatalytic activity of AuNi-TiO2ntbs catalysts was improved remarkably when the Ni layer of 100 and 400 nm was used for the deposition of Au crystallites. The Ni-TiO2ntb catalyst generates the maximum power density values of ca. 85–121 mW·cm−2 at a temperature of 25–55 °C, whereas the AuNi-TiO2ntb catalysts that have the Au loading of 3.07 and 15.7 μgAu·cm−2 achieve the power density values of ca. 104–147 and 119–170 mW·cm−2, respectively, at a temperature of 25–55 °C.

Performance of a perovskite solar cell is largely influenced by the optoelectronic properties of metal halide perovskite films. Here we study the influence of cesium concentration on morphology, crystal structure, photoluminescence and optical properties of the triple cation perovskite film. Incorporation of small amount (x = 0.1) of cesium cations into Csx(MA0.17FA0.83)1−x Pb(I0.83Br0.17)3 leads to enhanced power conversion efficiency (PCE) of the solar cell resulting mainly from significant rise of the short-current density and the fill factor value. Further increase of Cs concentration (x > 0.1) decreases the film’s phase purity, carrier lifetime and correspondingly reduces PCE of the solar cell. Higher concentration of Cs (x ≥ 0.2) causes phase segregation of the perovskite alongside with formation of Cs-rich regions impeding light absorption.