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Single-crystal planes are ideal platforms for catalytic research. In this work, rolled copper foils with predominantly (220) planes were used as the starting material. By using temperature gradient annealing, which caused grain recrystallization in the foils, they were transformed to those with (200) planes. In acidic solution, the overpotential of such a foil (10 mA cm−2) was found to be 136 mV lower than that of a similar rolled copper foil. The calculation results show that hollow sites formed on the (200) plane have the highest hydrogen adsorption energy and are active centers for hydrogen evolution. Thus, this work clarifies the catalytic activity of specific sites on the copper surface and demonstrates the critical role of surface engineering in designing catalytic properties.

Alloys based on TiNi are widely used in various fields of technology and medicine. In the present work, we report on preparation of TiNi-alloy based wire with the shape memory effect, which was used for compression clips for surgery. Composition and structure of the wire, and its martensitic and physical-chemical properties were studied using SEM, TEM, optic microscopy, profilometry, mechanical tests, etc. The TiNi alloy was found to consist of B2 and B19' and secondary-phase particles of Ti2Ni, TiNi3 and Ti3Ni4. Its matrix was slightly enriched in Ni (50.3 at. % of Ni). Homogeneous grain structure was revealed (an average grain size of 19±0.3 μm) with equal quantities of grain boundaries of special and general types. Surface oxide layer provide improved biocompatibility and promote adhesion of protein molecules. Overall, the obtained TiNi wire was concluded to exhibit martensitic, physical and mechanical properties suitable for its use as an implant material. The wire was then used for manufacturing compression clips with the shape memory effect and applied in surgery. The medical experiment that involved 46 children demonstrated that the use of such clips in children with double-barreled enterostomies permitted to improve the results of surgical treatment.

Combination of dissimilar materials such as noble metals and common semiconductors within unified nanomaterials holds promise for optoelectronics, catalysis and optical sensing. Meanwhile, difficulty of obtaining such hybrid nanomaterials using common lithography-based techniques stimulates an active search for advanced, inexpensive, and straightforward fabrication methods. Here, we report one-pot one-step synthesis of Ag-decorated Si microspheres via nanosecond laser ablation of monocrystalline silicon in isopropanol containing AgNO3. Laser ablation of bulk silicon creates the suspension of the Si microspheres that host further preferential growth of Ag nanoclusters on their surface upon thermal-induced decomposition of AgNO3 species by subsequently incident laser pulses. The amount of the AgNO3 in the working solution controls the density, morphology, and arrangement of the Ag nanoclusters allowing them to achieve strong and uniform decoration of the Si microsphere surface. Such unique morphology makes Ag-decorated Si microspheres promising for molecular identification based on the surface-enhanced Raman scattering (SERS) effect. In particular, the designed single-particles sensing platform was shown to offer temperature-feedback modality as well as SERS signal enhancement up to 106, allowing reliable detection of the adsorbed molecules and tracing their plasmon-driven catalytic transformations. Considering the ability to control the decoration degree of Si microspheres by Ag nanoclusters via amount of the AgNO3, the developed one-pot easy-to-implement PLAL synthesis holds promise for gram-scale production of high-quality hybrid nanomaterial for various nanophotonics and sensing applications.

So far, poly(L-lactic acid), PLLA nanosheets proved to be promising for wound healing. Such biodegradable materials are easy to prepare, bio-friendly, cost-effective, simple to apply and were shown to protect burn wounds and facilitate their healing. At the same time, certain metal ions are known to be essential for wound healing, which is why this study was motivated by the idea of incorporating PLLA nanosheets with Zn2+ ion containing nanoparticles. Upon being applied on wound, such polymer nanosheets should release Zn2+ ions, which is expected to improve wound healing. The work thus focused on preparing PLLA nanosheets embedded with several kinds of Zn-containing nanoparticles, their characterization and ion-release behavior. ZnCl2 and ZnO nanoparticles were chosen because of their different solubility in water, with the intention to see the dynamics of their Zn2+ ion release in liquid medium with pH around 7.4. Interestingly, the prepared PLLA nanosheets demonstrated quit similar ion release rates, reaching the maximum concentration after about 10 h. This finding implies that such polymer materials can be promising as they are expected to release ions within several hours after their application on skin.

This paper reports on a facile bottom-up method for the direct integration of a silicon (Si)-magnesium silicide (Mg2Si) heterojunction solar cell (HSC) with a textured rear reflector made of stainless steel (SS). Modified wet chemical etching and post processing of SS substrates resulted in the formation of both a rough surface texture and diffusion barrier layer, consisting of magnetite (Fe3O4) with reduced optical reflection. Then, Si, Mg2Si and CaSi2 layers were stepwise thermally evaporated onto the textured SS surface. No traces of Fe and Cr silicide phases were detected by Raman spectroscopy, confirming effective suppression of impurity diffusion from the SS to the upper layers at least at temperatures required for Si deposition, as well as Mg2Si and CaSi2 formation. The obtained black-SS/Fe3O4/Si/Mg2Si/CaSi2 sample preserved, to some extent, its underlying textured morphology and demonstrated an averaged reflection of 15% over the spectral range of 200–1800 nm, while its prototype HSC possessed a wideband photoresponse with a photoelectric conversion efficiency of 7.5% under AM1.5 illumination. Moreover, Si layers deposited alone onto a black-SS substrate demonstrated competitive antireflection properties compared with black Si (b-Si) obtained by traditional top-down etching approaches, and hybrid b-Si/textured-SS structures with a glue-bonded interlayer.

Using the methods of scanning and transmission electron microscopy, the features of the structural-phase state of a vanadium alloy of the V–Cr–Ta–Zr system after a combined treatment, which consisted in cyclic alternation of thermomechanical and chemical-heat treatments, were studied. The values of yield strength and ductility of the V–Cr–Ta–Zr alloy were determined, depending on the stabilization and test temperatures. It was established that, after the combined treatment, the structural-phase state of the V–Cr–Ta–Zr alloy was composite, in which the joint implementation of dispersion and substructural strengthening ensured the formation of a gradient grain structure with a polygonal state, the elements of which were fixed by nanosized ZrO2 particles characterized by a high thermal stability. Such modification of the microstructure was accompanied by an increase in the high-temperature strength and a shift in the upper limit of the temperature stability interval towards high temperatures, of up to 900 °C. It was assumed that the polygonal state inside the grains contributed to the implementation of cooperative mechanisms of the dislocation–disclination type, which ensured the accommodation of the material in the “high-strength state” under loading.

Currently, catalytic processing of biorenewable raw materials into valuable products attracts more and more attention. In the present work, silica-supported FePO

The study demonstrates a method for controlling not only the phase composition but also the atomic composition of TiNi matrix in porous TiNi-Ti alloys developed for biomedical uses as implants. The alloys were obtained from TiNi powder which was sintered with Ti powder added at as much as 0–10 at%. The structure, phase and chemical composition of the produced TiNi-Ti alloys was investigated with respect to the amount of Ti added into the material. It is shown that in the sintered product containing 5 at% and more of Ti additive, the composition of its TiNi matrix becomes close to equiatomic (with Ti:Ni atomic ratio ~1), and the excessive Ti precipitates as secondary phases Ti2Ni and Ti3Ni4. In parallel, with increase in Ti ad- ditive from 0–10 at%, the structure of the precipitating Ti2Ni type phases changes its morphology from separate spherical or pyramidal precipitates to large dendritic formations. The direct martensitic trans- formation from austenite to martensite in all the samples was found to proceed in two stages and through the R-phase (B2→R→B19′). Thermoresistive analysis demonstrated that TiNi-Ti samples with 5 and more at% of Ti had their characteristic starting temperature of martensite transition stabilizing at ~57 °C (330 K). This implies that the sample with 5 at% of Ti additive exhibited desired martensite transition temperatures, while containing a minimum concentration of secondary-phase precipitates in its matrix which deteriorate its properties. Thus, for the 곙rst time, we show that a very simple preparation approach based on sintering powders of TiNi and Ti is capable of producing porous TiNi-Ti alloys with properties optimized for fabricating bone implants.

Hydrogen is an ideal energy source from the point of view of ecology. The development of efficient technologies for its production with minimum carbon emission is an urgent task for the near future. The solution to this problem is possible via design and preparation of novel revolutionary materials for various processes of water splitting. The unique high-energy laser ablation method is one of promising approaches to prepare such materials. This review summarizes recent advances in the use of laser ablation in liquid phase as a technique for the synthesis of catalysts for hydrogen production. In addition, we also cover similar nanomaterials generated in gas environment and consider laser-produced nanomaterials for hydrogen storage and detection.

Long-term stability in contact with water of organosilane layers formed by octadecyltrimethoxysilane (ODTMS) on polished aluminum alloy (AA2024) through dip-coating was studied by combining SEM, water contact angle measurements, and X-ray photoelectron spectroscopy. Similar organosilane layers were formed on AA2024 coated with permanganate conversion coating, 1,2-bis(triethoxysilyl)ethane (BTSE) and hydrated SiOx as under-layers, after which their long-term durability was also tested. During immersion in water for about one month, all the samples exhibited a decrease in hydrophobicity, implying the prepared organosilane layer was not stable over time, gradually hydrolyzing and letting water interact with the underlying layer. In parallel, SEM images of one-layer samples taken after immersion showed clear signs of local electrochemical corrosion, while XPS analysis confirmed a loss of silicon from the surface layer. The highest stability over time was demonstrated by a one-layer sample prepared in an ethanol/water bath for 5 min and by a similar ODTMS layer prepared on hydrated MnOx as an under-layer.

Molybdenum sulfide is a very promising catalyst for the photodegradation of organic pollutants in water. Its photocatalytic activity arises from unsaturated sulfur bonds, and it increases with the introduction of structural defects and/or oxygen substitutions. Amorphous molybdenum sulfide (a-MoSxOy) with oxygen substitutions has many active sites, which create favorable conditions for enhanced catalytic activity. Here we present a new approach to the synthesis of a-MoSxOy and demonstrate its high activity in the photodegradation of the dye methylene blue (MB). The MoSxOy was deposited on hexagonal boron oxynitride (h-BNO) nanoflakes by reacting h-BNO, MoCl5, and H2S in dimethylformamide (DMF) at 250 °C. Both X-ray diffraction analysis and high-resolution TEM show the absence of crystalline order in a-MoSxOy. Based on the results of Raman and X-ray photoelectron spectroscopy, as well as analysis by the density functional theory (DFT) method, a chain structure of a-MoSxOy was proposed, consisting of MoS3 clusters with partial substitution of sulfur by oxygen. When a third of the sulfur atoms are replaced with oxygen, the band gap of a-MoSxOy is approximately 1.36 eV, and the valence and conduction bands are 0.74 eV and −0.62 eV, respectively (relative to a standard hydrogen electrode), which satisfies the conditions of photoinduced splitting of water. When illuminated with a mercury lamp, a-MoSxOy/h-BNxOy nanohybrids have a specific mass activity in MB photodegradation of approximately 5.51 mmol g−1 h−1, which is at least four times higher than so far reported values for nonmetal catalysts. The photocatalyst has been shown to be very stable and can be reused.

Molybdenum sulfide is a very promising catalyst for the photodegradation of organic pollutants in water. Its photocatalytic activity arises from unsaturated sulfur bonds, and it increases with the introduction of structural defects and/or oxygen substitutions. Amorphous molybdenum sulfide (a-MoSxOy) with oxygen substitutions has many active sites, which create favorable conditions for enhanced catalytic activity. Here we present a new approach to the synthesis of a-MoSxOy and demonstrate its high activity in the photodegradation of the dye methylene blue (MB). The MoSxOy was deposited on hexagonal boron oxynitride (h-BNO) nanoflakes by reacting h-BNO, MoCl5, and H2S in dimethylformamide (DMF) at 250 °C. Both X-ray diffraction analysis and high-resolution TEM show the absence of crystalline order in a-MoSxOy. Based on the results of Raman and X-ray photoelectron spectroscopy, as well as analysis by the density functional theory (DFT) method, a chain structure of a-MoSxOy was proposed, consisting of MoS3 clusters with partial substitution of sulfur by oxygen. When a third of the sulfur atoms are replaced with oxygen, the band gap of a-MoSxOy is approximately 1.36 eV, and the valence and conduction bands are 0.74 eV and −0.62 eV, respectively (relative to a standard hydrogen electrode), which satisfies the conditions of photoinduced splitting of water. When illuminated with a mercury lamp, a-MoSxOy/h-BNxOy nanohybrids have a specific mass activity in MB photodegradation of approximately 5.51 mmol g−1 h−1, which is at least four times higher than so far reported values for nonmetal catalysts. The photocatalyst has been shown to be very stable and can be reused.

Three bismuth silicate-based photocatalysts (composites of Bi2SiO5 and Bi12SiO20) prepared via the hydro-/solvothermal approach were studied using electrochemical methods. The characteristic parameters of semiconductors, such as flat band potential, donor density, and mobility of their charge carriers, were obtained and compared with the materials’ photocatalytic activity. An attempt was made to study the effect of solution components on the semiconductor/liquid interface (SLI). In particular, the Mott–Schottky characterization was made in a common model electrolyte (Na2SO4) and with the addition of glycerol as a model organic compound for photocatalysis. Thus, a medium close to those in photocatalytic experiments was simulated, at least within the limits allowed by electrochemical measurements. Zeta-potential measurements and electrochemical impedance spectroscopy were used to reveal the processes taking place at the SLI. It was found that the medium in which measurements were carried out dramatically impacted the results. The flat band potential values (Efb) obtained via the Mott–Schottky technique were shown to differ significantly depending on the solution used in the experiment, which is explained by different processes taking place at the SLI. A strong influence of specific adsorption of commonly used sulfate ions and neutral molecules on the measured values of Efb was shown.

Here, we present the single-step laser-assisted fabrication of anti-reflective hierarchical surface textures on silicon locally functionalized with a photoluminescent (PL) molecular nanolayer. Using femtosecond-laser ablation of commercial crystalline Si wafers placed under a layer of a solution containing rhodamine 6G (R6G) a triethoxysilyl derivative, we fabricated ordered arrays of microconical protrusions with self-organized nanoscale surface morphology. At the same time, the laser-induced temperature increase facilitated surface activation and local binding of the R6G derivative to the as-fabricated nanotextured surface. The produced dual-scale surface textures showed remarkable broadband (visible to near-IR) light-absorbing properties with an averaged reflectivity of around 1%, and the capping molecular nanolayer demonstrated a strongly enhanced PL yield. By performing a pH sensing test using the produced nanotextured substrate, we confirmed the retention of sensory properties of the molecules attached to the surface and validated the potential applicability of the high-performing liquid-assisted laser processing as a key technology for the development of innovative multifunctional sensing devices in which the textured substrate (e.g., ultra-black semiconductor) plays a dual role as a support and PL signal amplifier.

Amorphous silicon (&alpha, Si) film present an inexpensive and promising material for optoelectronic and nanophotonic applications. Its basic optical and optoelectronic properties are known to be improved via phase transition from amorphous to polycrystalline phase. Infrared femtosecond laser radiation can be considered to be a promising nondestructive and facile way to drive uniform in-depth and lateral crystallization of &alpha, Si films that are typically opaque in UV-visible spectral range. However, so far only a few studies reported on use of near-IR radiation for laser-induced crystallization of &alpha, Si providing less information regarding optical properties of the resultant polycrystalline Si films demonstrating rather high surface roughness. The present work demonstrates efficient and gentle single-pass crystallization of &alpha, Si films induced by their direct irradiation with near-IR femtosecond laser pulses coming at sub-MHz repetition rate. Comprehensive analysis of morphology and composition of laser-annealed films by atomic-force microscopy, optical, micro-Raman and energy-dispersive X-ray spectroscopy, as well as numerical modeling of optical spectra, confirmed efficient crystallization of &alpha, Si and high-quality of the obtained films. Moreover, we highlight localized laser-induced crystallization of &alpha, Si as a promising way for optical information encryption, anti-counterfeiting and fabrication of micro-optical elements.

Different methods (the wetness impregnation of Ag and Pd precursors dissolved in water or acetonitrile solution, and the double solvent impregnation technique) were employed to immobilize Ag&ndash, Pd nanoparticles (NPs) into the pores of the microporous zirconium-based metal-organic framework known as UiO-66. The obtained materials were characterized by using nitrogen adsorption-desorption at &minus, 196 &deg, C, powder X-ray diffraction, UV-Vis diffusion reflectance spectroscopy, and transition electron microscopy measurements. Special attention was paid to the acid and redox properties of the obtained materials, which were studied by using temperature-programmed desorption of ammonia (TPD-NH3) and temperature-programmed reduction (TPR-H2) methods. The use of a drying procedure prior to reduction was found to result in metallic NPs which, most likely, formed on the external surface and were larger than corresponding voids of the metal-organic framework. The formation of Ag&ndash, Pd alloy or monometallic Ag and Pd depended on the nature of both metal precursors and the impregnation solvent used. Catalytic activity of the AgPd/UiO-66 materials in propylene glycol oxidation was found to be a result of synergistic interaction between the components in AgPd alloyed NPs immobilized in the pore space and on the external surface of UiO-66. The key factor for consistent transformation of propylene glycol into lactic acid was the proximity between redox and acid-base species.

Amorphous silicon (α-Si) film present an inexpensive and promising material for optoelectronic and nanophotonic applications. Its basic optical and optoelectronic properties are known to be improved via phase transition from amorphous to polycrystalline phase. Infrared femtosecond laser radiation can be considered as a promising nondestructive and facile way to drive uniform in-depth and lateral crystallization of α-Si films that are typically opaque in UV-visible spectral range. However, so far only a few studies reported on utilization of near-IR radiation for laser-induced crystallization of α-Si providing no information regarding optical properties of the resultant polycrystalline Si films. The present work demonstrates efficient and gentle single-pass crystallization of α-Si films induced by their direct irradiation with near-IR femtosecond laser pulses coming at sub-MHz repetition rate. Comprehensive analysis of morphology and composition of laser-annealed films by atomic-force microscopy, optical, micro-Raman and energy-dispersive X-ray spectroscopy, as well as numerical modeling of optical spectra, confirmed efficient crystallization of α-Si and high-quality of the obtained films. Moreover, we highlight localized laser-driven crystallization of α-Si as a promising way for optical information encryption, anti-counterfeiting and fabrication of micro-optical elements.

This study reports the differences in toxic action between cadmium sulfide (CdS) and zinc sulfide (ZnS) nanoparticles (NPs) prepared by recently developed xanthate-mediated method. The aquatic toxicity of the synthesized NPs on four marine microalgae species was explored. Growth rate, esterase activity, membrane potential, and morphological changes of microalgae cells were evaluated using flow cytometry and optical microscopy. CdS and ZnS NPs demonstrated similar level of general toxicity and growth-rate inhibition to all used microalgae species, except the red algae P. purpureum. More specifically, CdS NPs caused higher inhibition of growth rate for C. muelleri and P. purpureum, while ZnS NPs were more toxic for A. ussuriensis and H. akashiwo species. Our findings suggest that the sensitivity of different microalgae species to CdS and ZnS NPs depends on the chemical composition of NPs and their ability to interact with the components of microalgal cell-wall. The red microalga was highly resistant to ZnS NPs most likely due to the presence of phycoerythrin proteins in the outer membrane bound Zn2+ cations defending their cells from further toxic influence. The treatment with CdS NPs caused morphological changes and biochemical disorder in all tested microalgae species. The toxicity of CdS NPs is based on their higher photoactivity under visible light irradiation and lower dissociation in water, which allows them to generate more reactive oxygen species and create a higher risk of oxidative stress to aquatic organisms. The results of this study contribute to our understanding of the parameters affecting the aquatic toxicity of semiconductor NPs and provide a basis for further investigations.

Mixed oxides of Zn and Sn are of interest for gas sensing and diverse optoelectronic applications, and therefore new approaches to prepare such nanomaterials are anticipated. This study reports, for the first time, on the use of laser ablation in liquid applied to a Sn-Zn alloy and describes obtained products. Core@shell Sn@SnO and ZnO nanoparticles are shown to be produced by millisecond pulsed laser upon ablating eutectic Sn-Zn alloy in water. The as-prepared materials were found to contain surface hydroxide layers which were dehydrated to SnOx and ZnO when higher laser energy fluence was applied or when the products were post-treated at 200C in air. The morphology, shape and size distribution, phase and chemical composition of prepared nanoparticles were studied as a function of laser parameters used during their preparation. Increase in pulse energy was found to result in fabrication of finer particles. It was found that while both metallic Sn and SnOx were presented in the product, zinc was always oxidized to its oxide ZnO. In addition, when properly annealed, the produced nanomaterial demonstrated gas sensing response towards ammonia at room temperature.

Having a wide range of applications, bismuth silicate-based materials (BSO) attract attention of numerous researchers. Typically, they are synthesized either from active chemicals or through high-energy impact on their precursors. The present work is the first report on BSO-based nanomaterials prepared via laser processing in liquid phase in which the following two-step scheme was realized: (1) Individual colloids of Bi- and Si-based nanoparticles were obtained via ablating their metallic targets in distilled water and then mixed; (2) Post-treatment of the mixed colloid was performed with the same laser beam as in stage (1). The products obtained after drying of non-treated and post-treated mixed colloids (denoted as samples BSO and BSO_hν, respectively) were carefully characterized using a set of microscopic, spectroscopic and electrochemical analyses, after which their photocatalytic performance in presence of model organic dye (rhodamine B) and phenol was tested. The additional laser treatment was found to lead to active interaction between Bi- and Si-containing species and stimulated formation of phases with Bi-O-Si bonds. The post-irradiated sample BSO_hν showed improved stability and catalytic performance, thus opening avenues for wider use of laser processing in liquids as a method allowing for preparation of nanostructures with complex chemical composition.

Hybrids of semiconductor nanomaterials often demonstrate properties that are superior to those of their components. In this study, we prepared hybrid nanomaterials of TiO2 and ZnO, which are among the most actively studied semiconductors, by means of millisecond-pulsed laser and analyzed how their morphology, particle size, and surface composition depend on preparation conditions. A series of nanomaterials were obtained via sequentially ablating Zn and Ti metal plates (in different sequences) in water, while laser pulses of lower (2.0 J/pulse) and higher (5.0 J/pulse) energy were applied. The properties of laser-produced hybrid TiO2-ZnO nanomaterials were shown to be governed by experimental conditions such as laser pulse width, pulse peak power, and reaction media (either pure water or colloid with nanoparticles). The morphology revealed nanospheres of TiO2 that decorate nanorods of ZnO or flower-like aggregates of zinc oxide. Intriguingly, after extended ablation time, titania was found to be self-doped with Ti3+ and Ti2+ ions, and the contribution of lower oxidation states of titanium could be controlled by the applied laser pulse energy. The physicochemical characteristics of hybrid nanomaterials were compared with pure ZnO and TiO2 prepared under the same laser conditions.

We report an easy-to-implement device for surface-enhanced Raman scattering (SERS)-based detection of various analytes dissolved in water droplets at trace concentrations. The device combines an analyte-enrichment system and SERS-active sensor site, both produced via inexpensive and high-performance direct femtosecond (fs)-laser printing. Fabricated on a surface of water-repellent polytetrafluoroethylene substrate as an arrangement of micropillars, the analyte-enrichment system supports evaporating water droplet in the Cassie&ndash, Baxter superhydrophobic state, thus ensuring delivery of the dissolved analyte molecules towards the hydrophilic SERS-active site. The efficient pre-concentration of the analyte onto the sensor site based on densely arranged spiky plasmonic nanotextures results in its subsequent label-free identification by means of SERS spectroscopy. Using the proposed device, we demonstrate reliable SERS-based fingerprinting of various analytes, including common organic dyes and medical drugs at ppb concentrations. The proposed device is believed to find applications in various areas, including label-free environmental monitoring, medical diagnostics, and forensics.

In this paper, we report a new, simple method for the synthesis of CdS and ZnS nanoparticles (NPs) prepared in a basic aqueous medium using metal xanthate as the sulfur source. The structure, morphology, size distribution, optical band gap, and photocatalytic properties of the newly obtained nanomaterials were investigated by UV-Vis spectroscopy, X-ray diffraction, and transmission electron microscopy. The results show that both CdS and ZnS crystallized in cubic phase and formed NPs with average sizes of 7.0 and 4.2 nm for CdS and ZnS, respectively. A blue shift of UV-Vis absorbance band and higher energy band gap values were observed for both materials in comparison with their bulk counterparts, which is in accordance with the quantum confinement effect. The as-prepared nanomaterials were tested in visible-light driven photocatalytic decomposition of methylene blue (MB). After irradiation for 180 min, the degradation rate of MB with a concentration of 8 &times, 10&minus, 6 mol/L mixed with a photocatalyst (CdS or ZnS, both 10 mg in 100 mL solution of MB) was found to be 72% and 61%, respectively. The CdS NPs showed better photocatalytic activity than ZnS, which could be explained by their lower energy band gap and thus the ability to absorb light more efficiently when activated by visible-light irradiation.

Engineering surface structure of catalysts is an efficient way towards high catalytic performance. Here, we report on the synthesis of regular iridium nanospheres (Ir NSs), with abundant atomic steps prepared by a laser ablation technique. Atomic steps, consisting of one-atom level covering the surface of such Ir NSs, were observed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The prepared Ir NSs exhibited remarkably enhanced activity both for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in acidic medium. As a bifunctional catalyst for overall water splitting, they achieved a cell voltage of 1.535 V @ 10 mA/cm2, which is much lower than that of Pt/C-Ir/C couple (1.630 V @ 10 mA/cm2).

We demonstrate a multi-purpose plasmonic sensor based on a nanovoid array fabricated via inexpensive and highly-reproducible direct femtosecond laser patterning of thin glass-supported Au films. The proposed nanovoid array exhibits near-IR surface plasmon (SP) resonances, which can be excited under normal incidence and optimised for specific applications by tailoring the array periodicity, as well as the nanovoid geometric shape. The fabricated SP sensor offers competitive sensitivity of &asymp, 1600 nm/RIU at a figure of merit of 12 in bulk refractive index tests, as well as allows for identification of gases and ultra-thin analyte layers, making the sensor particularly useful for common bioassay experiments. Moreover, isolated nanovoids support strong electromagnetic field enhancement at lattice SP resonance wavelength, allowing for label-free molecular identification via surface-enhanced vibration spectroscopy.

The present paper deals with studying the surface morphology of commercially pure (cp) Ti Gr-2 and Ti6Al4V treated by a picosecond laser and with determining the optimal technological parameters for fabricating cavities with a regular shape and a depth of about 10 μm. The surfaces of disk-shaped samples were treated by a commercial picosecond laser with a power of 0.2 W, 0.5 W and 1 W and a number of pulses between 1,000 and 20,000. The samples’ surface was investigated by SEM and a non-contact 3D surface profiler. The technological parameters were optimized by regression analysis using the QStatLab software. It was found that after laser treatment with the lowest values of the above parameters only the surface roughness changed in the case of cp-Ti, while its Ti6Al4V counterpart had a “melted zone” with a 5.5-μm depth. Raising the values of the regime parameters mainly led to an increased cavity depth on the cp-Ti surface, while those on Ti6Al4V increased in all dimensions. The surface roughness of both materials was higher after the laser treatment and grew bigger as the laser power and the number of pulses were increased. The optimal technological parameters for treatment of cp-Ti and Ti6Al4V were found. The results obtained can be used for picosecond laser texturing of titanium surfaces using linear or dimple types of patterns.

Zinc-air fuel cells (ZAFCs) present a promising energy source with a competing potential with the lithium-ion battery and even with proton-exchange membrane fuel cells (PEMFCs) for applications in next generation electrified transport and energy storage. The regeneration of zinc is essential for developing the next-generation, i.e., electrochemically rechargeable ZAFCs. This review aims to provide a comprehensive view on both theoretical and industrial platforms already built hitherto, with focus on electrode materials, electrode and electrolyte additives, solution chemistry, zinc deposition reaction mechanisms and kinetics, and electrochemical zinc regeneration systems. The related technological challenges and their possible solutions are described and discussed. A summary of important R&D patents published within the recent 10 years is also presented.

Porous ceramic materials of SiC were synthesized from carbon matrices obtained via pyrolysis of natural cork as precursor. We propose a method for the fabrication of complex-shaped porous ceramic hardware consisting of separate parts prepared from natural cork. It is demonstrated that the thickness of the carbon-matrix walls can be increased through their impregnation with Bakelite phenolic glue solution followed by pyrolysis. This decreases the material's porosity and can be used as a way to modify its mechanical and thermal characteristics. Both the carbon matrices (resulted from the pyrolysis step) and the resultant SiC ceramics are shown to be pseudomorphous to the structure of initial cork. Depending on the synthesis temperature, 3C-SiC, 6H-SiC, or a mixture of these polytypes, could be obtained. By varying the mass ratio of initial carbon and silicon components, stoichiometric SiC or SiC:C:Si, SiC:C, and SiC:Si ceramics could be produced. The structure, as well as chemical and phase composition of the prepared materials were studied by means of Raman spectroscopy and scanning electron microscopy.

These days, composite materials based on polymers and inorganic nanoparticles (NPs) are widely used in optoelectronics and biomedicine. In this work, composite membranes of polylactic acid and ZnO NPs containing 5&ndash, 40 wt.% of the latter NPs were produced by means of electrospinning. For the first time, polymer material loaded with up to 40 wt.% of ZnO NPs (produced via laser ablation in air and having non-modified surface) was used to prepare fiber-based composite membranes. The morphology, phase composition, mechanical, spectral and antibacterial properties of the membranes were tested by a set of analytical techniques including SEM, XRD, FTIR, UV-vis, and photoluminescence spectroscopy. Antibacterial activity of the materials was evaluated following standard procedures (ISO 20743:2013) and using S. aureus and E. coli bacteria. It is shown that incorporation of 5&ndash, 10 wt.% of NPs led to improved mechanical properties of the composite membranes, while further increase of ZnO content up to 20 wt.% and above resulted in their noticeable deterioration. At the same time, the antibacterial properties of ZnO-rich membranes were more pronounced, which is explained by a larger number of surface-exposed ZnO NPs, in addition to those embedded into the bulk of fiber material.

Here, we demonstrate a simple direct maskless laser-based approach for fabrication of back-reflector-coupled plasmonic nanorings arrays. The approach is based on delicate ablation of an upper metal film of a metal-insulator-metal (MIM) sandwich with donut-shaped laser pulses followed by argon ion-beam polishing. After being excited with a radially polarized beam, the as-prepared MIM configuration of the nanorings permitted to realize efficient nanofocusing of constructively interfering plasmonic waves excited in the gap area between the nanoring and back-reflector mirror. For optimized geometric parameters of such MIM structure, substantial enhancement of the electromagnetic near-fields at the center of the ring within a single focal spot with the size of 0.37$\lambda^{2}$ can be achieved, which is confirmed by Finite Difference Time Domain (FDTD) calculations, as well as by detection of enhanced PL signal from adsorbed organic dye molecules. The simple large-scale and cost-efficient fabrication procedure used, along with relatively good tolerance to excitation beam misalignment, make the proposed structures promising for realization of various nanophotonic and biosensing platforms that utilize cylindrical vector beam as a pump source., Comment: 7 pages, 3 figures

We developed a simple and efficient process, laser heating of nickel powder in ethanol, to produce carbon-encapsulated nickel microspheres. Long-pulse-width laser heated nickel powder suspended in pure ethanol into liquid droplets. In turn, the latter droplets became sphere-like, pyrolyzed surrounding ethanol and dissolved the produced carbon atoms. Because of their lower solubility in solid nickel, excess carbon atoms were then expelled from the metal core after solidification, thus forming graphite-like shells on the laser-modified Ni spheres. Hence, after pyrolysis the transformation of carbon was found to follow the dissolution-precipitation mechanism. The produced carbon-encapsulated nickel microspheres exhibited higher oxidation resistance compared with the initial nickel powder, while keeping their magnetic properties essentially unchanged.

Highly sensitive and selective detection of volatile organic compounds (VOCs) with fast response time is imperative based on safety requirements, yet often remains a challenge. Herein, we propose an effective solution, preparing a novel gas sensor comprised of amorphous nanoflake arrays (a-NFAs) with specific surface groups. The sensor was produced via an extremely simple process in which a-NFAs of CdO were deposited directly onto an interdigital electrode immersed in a chemical bath under ambient conditions. Upon exposure to a widely used VOC, diethyl ether (DEE), the sensor exhibits excellent performance, more specifically, the quickest response, lowest detection limit and highest selectivity ever reported for DEE as a target gas. The superior gas-sensing properties of the prepared a-NFAs are found to arise from their open trumpet-shaped morphology, defect-rich amorphous nature, and surface CO groups.

ZnO nanomaterials with controlled size, shape and surface chemistry are required for applications in diverse areas, such as optoelectronics, photocatalysis, biomedicine and so on. Here, we report on ZnO nanostructures with rod-like and spherical shapes prepared via laser ablation in liquid using a laser with millisecond-long pulses. By changing laser parameters (such as pulse width and peak power), the size or aspect ratio of such nanostructures could be tuned. The surface chemistry and defects of the products were also strongly affected by applied laser conditions. The preparation of different structures is explained by the intense heating of liquid media caused by millisecond-long pulses and secondary irradiation of already-formed nanostructures.

We report on a 100-fold capacitance increase in MoS2-based supercapacitors achieved via optimizing the in-plane 1T-2H phase hybridization of the monolayers. Chemically exfoliated MoS2 monolayers were annealed at low temperature to tune their 1T content from 2% to 60%. The obtained hybridization states were confirmed by X-ray photoelectron and Raman spectroscopies. After optimizing the hybridization degree, the electrode based on MoS2 monolayers with 40% of the 1T phase exhibited outstanding performance with a resistance as low as 0.68 kΩ sq−1, specific capacitance of 366.9 F g−1, and retention ratio of 92.2% after 1000 cycles at current densities of 0.5 A g−1.