Search

Green and highly selective synthesis of ammonia (NH3) via electrochemical reduction reaction of toxic nitrite (NO2−RR) in a neutral electrolyte is a feasible solution for energy and environmental issues. Dual‐nature electrocatalysts combining metal and metal‐derived materials are crucial for enhancing the selectivity parameter and efficacy of this reaction. Here, Pd‐, Pt‐, Ru‐, and Ir‐decorated Co3(PO4)2 (CoPi) composites with a robust metal–support interaction are obtained via the one‐pot pulsed laser ablation in liquid method. Among the designed composites, Ir–CoPi affords ≈100% Faradaic efficiency, mass balance, and selectivity toward NH3 product at sufficiently low potentials. Further, it affords the highest NH3 yield rate of 19.13 mg h−1 cm−2 with 78.1% removal of toxic NO2− with a rate constant kapp = 0.31 mm min−1 under −1.6 V versus Ag/AgCl. In situ experiments and theoretical investigations reveal the underlying mechanisms responsible for this outstanding performance of Ir–CoPi, which can be accredited to the generation of specific active sites on the Ir component. Insights derived from the evolving intermediate reactive species provide new opportunities for large‐scale NH3 production through electrochemical techniques, density functional theory calculations, and the improvement of the corresponding industrial processes. [ABSTRACT FROM AUTHOR]

Zirconium nitride (ZrN) nanoparticles (NPs) can offer appealing plasmonic properties for biomedical applications, but the synthesis of nontoxic, water-dispersible nanoformulations exhibiting plasmonic features in the biotransparency window presents a great challenge. Here, we report the synthesis, by methods of laser ablation, of small ZrN-based NPs, which are unique in combining photothermal heating and near-field enhancement in the transparency window. Depending on the synthesis environment, the formed ZrN-based NPs exhibit plasmonic absorption bands with maxima around 660–670 and 610–630 nm, which are largely red-shifted compared to what is expected from pure ZrN NPs. The observed shift is explained by the inclusion of zirconium oxide ZrOx (1 < x < 2) into NP composition and NP coating by naturally formed ZrOx. We then explored biophotonic applications of ZrN NPs. While pure NPs demonstrate their nontoxicity in vitro, their conjugation with anti-HER1 affibody ZHER1:1907 and subsequent photothermal heating with NIR-I laser cause 100% cancer cell death. In addition, profiting from the field enhancement, we demonstrate bioimaging functionality using a designed surface-enhanced Raman scattering probe based on an NP-conjugated azobenzene-CN-OH molecule as a Raman reporter. Combining a strong photothermal effect and the imaging option, laser-synthesized ZrN/ZrOx NPs promise a major advancement of theranostic modalities based on plasmonic nanomaterials. [ABSTRACT FROM AUTHOR]

Boron-enhanced proton therapy has recently appeared as a promising approach to increase the efficiency of proton therapy on tumor cells, and this modality can further be improved by the use of boron nanoparticles (B NPs) as local sensitizers to achieve enhanced and targeted therapeutic outcomes. However, the mechanisms of tumor cell elimination under boron-enhanced proton therapy still require clarification. Here, we explore possible molecular mechanisms responsible for the enhancement of therapeutic outcomes under boron NP-enhanced proton therapy. Spherical B NPs with a mode size of 25 nm were prepared by methods of pulsed laser ablation in water, followed by their coating by polyethylene glycol to improve their colloidal stability in buffers. Then, we assessed the efficiency of B NPs as sensitizers of cancer cell killing under irradiation with a 160.5 MeV proton beam. Our experiments showed that the combined effect of B NPs and proton irradiation induces an increased level of superoxide anion radical generation, which leads to the depolarization of mitochondria, a drop in their membrane mitochondrial potential, and the development of apoptosis. A comprehensive gene expression analysis (via RT-PCR) confirmed increased overexpression of 52 genes (out of 87 studied) involved in the cell redox status and oxidative stress, compared to 12 genes in the cells irradiated without B NPs. Other possible mechanisms responsible for the B NPs-induced radiosensitizing effect, including one related to the generation of alpha particles, are discussed. The obtained results give a better insight into the processes involved in the boron-induced enhancement of proton therapy and enable one to optimize parameters of proton therapy in order to maximize therapeutic outcomes. [ABSTRACT FROM AUTHOR]

The combination of aqueous electrolysis, either for hydrogen generation or CO2 conversion, with wastewater treatment offers an elegant way to tackle issues associated with our energy transition and the need for clean drinking water. However, it requires an anode capable of doing both the oxidation of the targeted pollutant and the oxygen evolution reaction (OER), as most pollutants are present in too low concentration to be practical for industrial electrolysis. In this study, we focussed on the oxidation of urea on NixFe100-x catalysts. These catalysts were prepared by pulsed laser ablation in liquid, a versatile and green technique to prepare electrocatalysts. Transmission electron microscopy of the nanoparticles indicates the production of monodisperse nanoparticles, with an average diameter increasing from 7.8 ± 2.8 to 19.7 ± 3.9 nm with a higher iron fraction. The composition could be controlled between pure Ni and NiFe bimetallic nanoparticles with up to 56 ± 3% of iron, by controlling the composition of the target. A brief optimisation of the electrode preparation (loading, catalyst-to-carbon ratio) yielded an optimum at about 30 µg/cm2 of catalyst with a catalyst-to-carbon ratio of 20:80. During the electrocatalytic tests, Ni was the best catalyst for urea oxidation, with a maximum peak current of 619 mA/mg. However, Ni75Fe25 was the best OER catalyst, showing a peak current of 1150 mA/mg. The difference increased further during CA at 0.5 V, during which Ni75Fe25 outperformed pure Ni by almost a factor of 3 after 30 min. [ABSTRACT FROM AUTHOR]

Pulsed laser ablation in liquids (PLAL) is a versatile technique to produce high-purity colloidal nanoparticles. Despite considerable recent progress in increasing the productivity of the technique, there is still significant demand for a practical, cost-effective method for upscaling PLAL synthesis. Here we employ and unveil the fundamentals of multi-beam (MB) PLAL. The MB-PLAL upscaling approach can bypass the cavitation bubble, the main limiting factor of PLAL efficiency, by splitting the laser beam into several beams using static diffractive optical elements (DOEs). A multimetallic high-entropy alloy CrFeCoNiMn was used as a model material and the productivity of its nanoparticles in the MB-PLAL setup was investigated and compared with that in the standard single-beam PLAL. We demonstrate that the proposed multi-beam method helps to bypass the cavitation bubble both temporally (lower pulse repetition rates can be used while keeping the optimum processing fluence) and spatially (lower beam scanning speeds are needed) and thus dramatically increases the nanoparticle yield. Time-resolved imaging of the cavitation bubble was performed to correlate the observed production efficiencies with the bubble bypassing. The results suggest that nanoparticle PLAL productivity at the level of g/h can be achieved by the proposed multi-beam strategy using compact kW-class lasers and simple inexpensive scanning systems. [ABSTRACT FROM AUTHOR]

The utilization of pulsed laser ablation in liquids (PLALs) for preparing gold nanoparticles (Au NPs) in organic solvents holds immense potential across diverse applications. This study introduces a compact and low-power microchip laser (MCL) system (average power 50 mW; pulse energy 0.5 mJ). Due to its compactness, an MCL is advantageous for easy manipulation in organic laboratories during the production of metal nanoparticles (NPs) for research and development purposes. In this research, poly(N-vinyl-2-pyrrolidone) (PVP) is used as a stabilizing agent for the preparation of Au NPs in organic solvents (CH2Cl2, CHCl3, 2-PrOH, MeCN, DMF, EtOH, NMP, and DMSO). Our experimental results demonstrate that the particle size remains consistent across all the organic solvents. This study explores the productivity of Au NPs in different organic solvents, revealing the necessity of multiple laser pulses to generate Au NPs successfully. This phenomenon, known as the 'incubation effect,' is linked to the lower pulse energy in the experimental condition and the thermal conductivity of the solvents. The findings emphasize the crucial role of solvent properties in determining the Au NPs productivity in PLAL. [ABSTRACT FROM AUTHOR]

The electroreduction of CO2 has been abundantly studied, but little attention has been given to the reaction occurring at the anode of this electrolyzer. Herein, we report one of the rare attempts to investigate the anode and potential reactions that could occur on this electrode during CO2 electrolysis. The electrooxidation of several aqueous pollutants, sulfamethazine (SMT), carbamazepine (CMP), ketamine and acetaminophen (ACE) was investigated at the anode of a CO2 electrolysis cell. Pulsed laser ablation in liquid (PLAL) was used to prepare the catalysts. PLAL is a versatile, environmentally safe technique used to create nanoparticles for electrocatalysis. Herein, bismuth nanoparticles were prepared as the CO2 reduction catalyst, as previously reported. Nickel nanoparticles were used for both the oxygen evolution reaction (OER) and the oxidation of the aqueous pollutants. Transmission electron microscopy (TEM) of the nickel nanoparticles indicates the production of monodisperse nanoparticles, with a 7.8 ± 2.8 nm average diameter. After evaluating the stability of the targeted pollutants, we focused on sulfamethazine, carbamazepine and acetaminophen due to their stability in aqueous environment. Among the various anode catalysts tested, nickel nanoparticles were the most versatile in degrading these pollutants; thus, further measurements were taken with this catalyst. A brief optimization of the degradation conditions (pH and potential) was also done, showing most efficient degradation at pH = 9 and 1.4 V vs Ag/AgCl. Once completed, CO2 reduction was coupled with the oxidation of a matrix of all three pollutants. The results show that the efficiency of the CO2 reduction was mostly unaffected by the combined presence of the pollutants at the anode. Oxidation of the target pharmaceuticals was also comparable to previous tests, reaching 62% for CMP, 53% for SMT and 33% for ACE within 20 min. [ABSTRACT FROM AUTHOR]

Elastomers are highly potential materials for shock absorption, cushioning, and similar applications. However, for most elastomers, poor strength limits their application. Compounding nanoparticles in the polymer matrix have been vastly explored to improve mechanical strength or introduce electrical, thermal, optical, and magnetic properties to the polymer. However, poor dispersion of nanoparticles in polymer mixture has remained a challenge in nanocomposite production. This study presents a unique approach to improving particle dispersion as well as designing ultra-soft, light, cost-effective, and highly compressible nanocomposite elastomers. To this end, magnesium nanoparticles were fabricated by pulsed laser ablation in a non-ionic surfactant (Triton X-100) and the mixture was added to an acrylic base polymer chain to design the nanocomposite elastomer. Various nanocomposites were manufactured using different ratios of surfactant and nanoparticle mixtures. The mechanical and optical properties of the composites were investigated. The nanocomposite containing the largest amount of Triton X-100 and magnesium nanoparticles displayed beyond 50% compressive deformation under only 0.4 MPa load and light absorbance was enhanced in the UV-visible region of the spectra. [ABSTRACT FROM AUTHOR]

Laser synthesis of polyyne molecules C 2 n H 2 (n > 2) in liquid hydrocarbons is a complex process in which intense pulsed radiation decomposes the initial carbon-containing substance (the hydrocarbon solvent itself or the solid carbon particles in a suspension). Notwithstanding the fact that the mechanism of pulsed laser ablation in liquids (PLAL) is widely accepted, the effect of the laser parameters on laser-driven polyyne formation is still not understood in detail. Here, we report a study of the polyyne yield as a function of the laser field intensity and exposure dose. Several carbon-containing liquids, including pure n-hexane, pure ethanol, and graphite powder suspended in ethanol, were treated with tightly focused picosecond IR radiation (wavelength of 1064 nm, pulse duration of 10 ps). The synthesis rate was characterized by UV-vis optical absorption spectroscopy. The yields of the polyynes were found to vary in exact accordance with the value of the absorbed laser energy, following specific nonlinear or linear laws. The influence of the laser intensity on the partial concentration of polyynes in the solution was analyzed. [ABSTRACT FROM AUTHOR]

Ultrapure composite nanostructures combining semiconductor and metallic elements as a result of ultrafast laser processing are important materials for applications in fields where high chemical purity is a crucial point. Such nanocrystals have already demonstrated prospects in plasmonic biosensing by detecting different analytes like dyes and bacteria. However, the structure of the nanocomposites, as well as the control of their properties, are still very challenging due to the significant lack of research in this area. In this paper, the synthesis of silicon–gold nanoparticles was performed using various approaches such as the direct ablation of (i) a gold target immersed in a colloidal solution of silicon nanoparticles and (ii) a silicon wafer immersed in a colloidal solution of plasmonic nanoparticles. The formed nanostructures combine both plasmonic (gold) and paramagnetic (silicon) modalities observed by absorbance and electron paramagnetic resonance spectroscopies, respectively. A significant narrowing of the size distributions of both types of two-element nanocrystals as compared to single-element ones is shown to be independent of the laser fluence. The impact of the laser ablation time on the chemical stability and the concentration of nanoparticles influencing their both optical properties and electrical conductivity was studied. The obtained results are important from a fundamental point of view for a better understanding of the laser-assisted synthesis of semiconductor–metallic nanocomposites and control of their properties for further applications. [ABSTRACT FROM AUTHOR]

Spherical copper oxide nanoparticles (CuO/Cu2O NPs) were synthesized by pulsed laser ablation in liquids (PLAL). The copper target was totally submerged in deionized (DI) water and irradiated by an infrared laser beam at 1064 nm for 30 min. The NPs were then characterized by dynamic light scattering (DLS) and atomic emission spectroscopy (AES) to determine their size distribution and concentration, respectively. The phases of copper oxide were identified by Raman spectroscopy. Then, the antibacterial activity of CuO/Cu2O NPs against foodborne pathogens, such as Salmonella enterica subsp. enterica serotype Typhimurium DT7, Escherichia coli O157:H7, Shigella sonnei ATCC 9290, Yersinia enterocolitica ATCC 27729, Vibrio parahaemolyticus ATCC 49398, Bacillus cereus ATCC 11778, and Listeria monocytogenes EGD, was tested. At a 3 ppm concentration, the CuO/Cu2O NPs exhibited an outstanding antimicrobial effect by killing most bacteria after 5 h incubation at 25 °C. Field emission scanning electron microscope (FESEM) confirmed that the CuO/Cu2O NPs destructed the bacterial cell wall. [ABSTRACT FROM AUTHOR]

Proton therapy is one of the promising radiotherapy modalities for the treatment of deep-seated and unresectable tumors, and its efficiency can further be enhanced by using boron-containing substances. Here, we explore the use of elemental boron (B) nanoparticles (NPs) as sensitizers for proton therapy enhancement. Prepared by methods of pulsed laser ablation in water, the used B NPs had a mean size of 50 nm, while a subsequent functionalization of the NPs by polyethylene glycol improved their colloidal stability in buffers. Laser-synthesized B NPs were efficiently absorbed by MNNG/Hos human osteosarcoma cells and did not demonstrate any remarkable toxicity effects up to concentrations of 100 ppm, as followed from the results of the MTT and clonogenic assay tests. Then, we assessed the efficiency of B NPs as sensitizers of cancer cell death under irradiation by a 160.5 MeV proton beam. The irradiation of MNNG/Hos cells at a dose of 3 Gy in the presence of 80 and 100 ppm of B NPs led to a 2- and 2.7-fold decrease in the number of formed cell colonies compared to control samples irradiated in the absence of NPs. The obtained data unambiguously evidenced the effect of a strong proton therapy enhancement mediated by B NPs. We also found that the proton beam irradiation of B NPs leads to the generation of reactive oxygen species (ROS), which evidences a possible involvement of the non-nuclear mechanism of cancer cell death related to oxidative stress. Offering a series of advantages, including a passive targeting option and the possibility of additional theranostic functionalities based on the intrinsic properties of B NPs (e.g., photothermal therapy or neutron boron capture therapy), the proposed concept promises a major advancement in proton beam-based cancer treatment. [ABSTRACT FROM AUTHOR]

The mechanisms of picosecond pulse laser ablation in liquid are investigated in a series of large-scale atomistic simulations performed for FeNi targets irradiated in a liquid environment by picosecond laser pulses at a broad range of fluences. The simulations reveal the existence of three fluence regimes featuring different dominant mechanisms of material ejection and nanoparticle formation. These are (1) the low fluence regime, where atomic clusters and small nanoparticles form through the evaporation of metal atoms followed by condensation in a low-density region at the front of the ablation plume, (2) the medium fluence regime, where roughening and decomposition of a top part of a transient spongy structure of interconnected liquid regions leads to the formation of large nanoparticles, and (3) the high fluence regime, where the nanoparticles form primarily at the phase separation front propagating through the ablation plume cooled from the supercritical state by expansion against the liquid environment and mixing with the liquid. The generation of the largest nanoparticles is observed in the medium fluence regime, and both the maximum size of the nanoparticles and the energy efficiency of the material conversion into nanoparticles decrease upon transition to the high fluence regime. Some of the nanoparticles experience extreme quench rates and rapidly solidify under conditions of deep undercooling, yielding a population of defect-rich nanoparticles of interest for practical applications. The results of the simulations are mapped to the conditions realized within a laser spot irradiated by a beam with a Gaussian spatial profile, where different ablation regimes are activated simultaneously in different parts of the laser spot. The spatially and time-resolved maps of the transient nonequilibrium states predicted in the simulations provide a comprehensive picture of the ablation dynamics and a solid foundation for interpretation of the results of time-resolved experimental probing of the initial stage of the ablation process. [ABSTRACT FROM AUTHOR]

Ytterbium ferrites are being used in many promising applications, such as visible-light photocatalysis, solar cells, magnetooptic devices, electro-magnetic equipment, etc., due to their fantastic ferroelectric and ferromagnetic properties. However, despite their good magnetic and radiopaque features, the use of ytterbium ferrites as multiplatform contrast agents in magnetic resonance imaging (MRI) and X-ray computed tomography (CT) is still under-developed. This is mainly due to difficulties in obtaining stable and biocompatible aqueous colloidal dispersions of ytterbium ferrite nanoparticles. In order to overcome this limitation, this work explores an eco-friendly method to directly synthesize such dispersions by liquid-assisted pulsed laser ablation of ytterbium ferrite massive targets. First, orthorhombic bulk YbFeO 3 targets were obtained by a reaction-sintering method. Then, colloidal dispersions of nanoparticles were produced directly in both distilled water and ethanol by irradiating the bulk YbFeO 3 targets with high-power infrared nanosecond lasers pulses. A battery of techniques has been used to characterize the as synthesized YbFeO 3 targets and colloidal dispersions of YbFe nanoparticles to determine their composition, structure, magnetic properties, X-ray attenuation potentials, and colloidal properties. Moreover, the biocompatibility of the systems was also analysed by MTT cell viability assay. Results indicated that the use of distilled water as ablation medium yields colloidal dispersions consisted mainly of paramagnetic ytterbium ferrite nanoparticles. Contrarily, the use of ethanol as solvent leads to colloidal dispersions of polycrystalline nanoparticles with both ferromagnetic and paramagnetic behaviour, due to the coexistence, in each nanoparticle, of ytterbium ferrite, ytterbium oxide, and iron oxide crystalline phases. Both colloidal dispersions exhibit also high biocompatibility and suitable X-ray attenuation properties. Moreover, they show bio-safe hydrodynamic sizes (lower than 200 nm) with acceptable overall hydrodynamic polydispersity index values (under 0.4), being stable in water for several weeks. These results pave the way for the future evaluation of Yb–Fe based nanoparticles as multiplatform contrast agents in multimodal MRI and CT imaging. [Display omitted] [ABSTRACT FROM AUTHOR]

Al nanoparticles are of significant interest due to their enhanced energetic properties and applicability in optics, biology, and the energy industry. We demonstrate the synthesis of core–shell Al nanoparticles via pulsed-laser-ablation-in-liquid, which reduces oxide formation and increases their resistance to reactive environments. When a bulk Al target was ablated in an organic solvent (acetone), high purity nanoparticles with a high Al content in the core part were generated. The size of the nanoparticles (6–7 nm) was not significantly changed according to the experimental conditions. However, low laser energy intensity is preferable due to less aggregation of nanoparticles and low impurity content. Amorphous and graphite carbon species were found in the coating of the core–shell Al nanoparticles. In addition, we show evidence of enolates or carboxylates in the coating material, as evidenced via energy dispersive spectroscopy and Fourier-transform infrared spectroscopy. Aging experiments in deionized water revealed that the passivated Al nanoparticles could maintain high purity in the core part and high stability in reactive environments such as water.

• Selenium needle-like structure synthesized by pulsed laser ablation. • Trigonal-selenium needles grown from amorphous-selenium nanoparticles. • Growth achieved within 24 h in Ethanol. Elongated stuctures, needle-like type, of trigonal selenium were synthesized successfully by pulsed laser ablation in ethanol. The aspect-ratio was controlled by tuning the repetition rate of the laser beam from 0.1 kHz to 19.9 kHz. Five minutes irradiation followed up by one day of aging inside the colloid was required to achieve the needle-like structure in ethanol. [ABSTRACT FROM AUTHOR]

Pulsed Laser Ablation in Liquids (PLAL) represents a prominent method for synthesising metallic nanoparticles and nano-alloys. This technique offers the potential precise control over the process and resulting products. However, a comprehensive description of the underlying mechanisms is still necessary to enhance control. Our investigation involved the utilisation of low fluence 6 ns laser pulses on 35 mm ^2 areas of thin films comprising layers of Ag , Pt , and Au to investigate the nano-structures and alloys obtained. The large laser spot produced nano-structures with peculiar morphological characteristics. Their analysis by High-Resolution Transmission Electron Microscopy (HRTEM) confirms that the early stages of the ablation plume play an essential role in the nucleation of nano-structures when the ablating metals have a strong interaction with the fluid, which has surpassed its critical temperature and pressure.

The utilization of pulsed laser ablation in liquids (PLALs) for preparing gold nanoparticles (Au NPs) in organic solvents holds immense potential across diverse applications. This study introduces a compact and low-power microchip laser (MCL) system (average power 50 mW; pulse energy 0.5 mJ). Due to its compactness, an MCL is advantageous for easy manipulation in organic laboratories during the production of metal nanoparticles (NPs) for research and development purposes. In this research, poly(N-vinyl-2-pyrrolidone) (PVP) is used as a stabilizing agent for the preparation of Au NPs in organic solvents (CH2Cl2, CHCl3, 2-PrOH, MeCN, DMF, EtOH, NMP, and DMSO). Our experimental results demonstrate that the particle size remains consistent across all the organic solvents. This study explores the productivity of Au NPs in different organic solvents, revealing the necessity of multiple laser pulses to generate Au NPs successfully. This phenomenon, known as the ‘incubation effect,’ is linked to the lower pulse energy in the experimental condition and the thermal conductivity of the solvents. The findings emphasize the crucial role of solvent properties in determining the Au NPs productivity in PLAL.

Selenium is a key chemical element used in photovoltaics and energy storage. It has been classified as an energy-critical element by the American Physical Society and the Materials Research Society. As selenium is crucial to develop energetic applications, various techniques have been used to synthesize selenium nanostructures such as wet chemistry, vapor-phase growth, and pulsed laser ablation. Here, for the first time, the nanoneedle morphology is synthesized by a technique different from e-beam lithography. To achieve this, pulsed laser ablation of a bulk selenium target was performed in various organic solvents and irradiated by a nanosecond Nd: YAG laser in the kHz regime for 5 min. The repetition rate of the pulsed laser allows one to tune the aspect ratio, sharpness, and diameter of the nanoneedle. This morphology is suitable for solar cells and photocells in optoelectronics. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of CO2 to formate was investigated in seawater as an alternative electrolyte to the bicarbonate buffer commonly used. Bismuth nanoparticles were prepared by pulsed laser ablation in liquids in ethanol, avoiding the use of toxic reagents or solvents. TEM analysis showed the nanoparticles were monodisperse and had an average number weighted diameter of 13 ± 5 nm. XRD showed that the nanoparticles were metallic which could suggest the presence of a carbon shell on the nanoparticles. However, this potential carbon shell does not appear to interfere with the electrocatalytic activity of the nanoparticles. A stepwise optimization of the catalyst weight fraction, Nafion® content, and loading showed that the best performances were achieved for 90% wt. bismuth nanoparticles on carbon, at a loading of 0.25 mg cm−2 and with 0.24% wt. Nafion®. The electrolysis in seawater showed similar or improved results both in terms of onset potential (− 1 V vs Ag/AgCl) selectivity (81 ± 4%) and activity (− 47 ± 11 mA cm−2) when compared to the reference bicarbonate buffer, demonstrating that seawater is an abundant, affordable alternative to the current buffer. [ABSTRACT FROM AUTHOR]

Transition–metal-doped electrocatalysts are considered as low-cost alternatives of Pt and RuO2 electrocatalysts for large scale electrochemical generations of hydrogen and oxygen, respectively. Although, chemical synthesis, typically adopted to produce these electrocatalysts, is scalable but hazardous by-products and chemical wastes create growing environmental concerns. Here, we developed a single step, single pot, and environmentally friendly physical approach of electric field-assisted pulsed laser ablation in liquid for the synthesis of colloidal solution of pure CuMoO4 (CMO) electrocatalysts. The entire process took few minutes and did not involve or generate any chemical. A pulsed picosecond laser was used to ablate MoS2 target at the solid-liquid interface to generate spatially confined plasma plume. Two parallel electrodes (copper sheets) were mounted around the plasma plume to modulate the plasma parameters, control the reactions at the plasma-liquid interface, and simultaneously inject copper ions from the electrode to the laser-produced plasma (LPP) for the generation of CMO. nanoparticles. Surprisingly, we observed that by varying the applied electric field, we can efficiently control the size, shape, crystallinity, morphology, and composition of as produced CMO nanocomposites and enhance their hydrogen evolution reaction (HER) performance. The characterization results proves that the introduction of applied electric field during the laser ablation process significantly change the morphology of as-prepared nanomaterials, and the shape of these nanomaterials were spherical, spindle and cuboid for MoS2, CuO and CMO respectively. Among all the fabricated electrocatalysts, CMO-60 is the best HER performer in alkaline medium, while MoS2 and CuO nanoparticles were the worse. For CMO-60 sample, only 440 mV overpotential required to reach the current density of 10 mA/cm2 and as well as posess good stability. We found that electrocatalysts produced at a higher electric field have higher contents of copper and oxygen leading to a superior HER activity. The developed approach can be applied for the synthesis of other electrocatalysts for a range of chemical reactions.

Ultrapure composite nanostructures combining semiconductor and metallic elements as a result of ultrafast laser processing are important materials for applications in fields where high chemical purity is a crucial point. Such nanocrystals have already demonstrated prospects in plasmonic biosensing by detecting different analytes like dyes and bacteria. However, the structure of the nanocomposites, as well as the control of their properties, are still very challenging due to the significant lack of research in this area. In this paper, the synthesis of silicon–gold nanoparticles was performed using various approaches such as the direct ablation of (i) a gold target immersed in a colloidal solution of silicon nanoparticles and (ii) a silicon wafer immersed in a colloidal solution of plasmonic nanoparticles. The formed nanostructures combine both plasmonic (gold) and paramagnetic (silicon) modalities observed by absorbance and electron paramagnetic resonance spectroscopies, respectively. A significant narrowing of the size distributions of both types of two-element nanocrystals as compared to single-element ones is shown to be independent of the laser fluence. The impact of the laser ablation time on the chemical stability and the concentration of nanoparticles influencing their both optical properties and electrical conductivity was studied. The obtained results are important from a fundamental point of view for a better understanding of the laser-assisted synthesis of semiconductor–metallic nanocomposites and control of their properties for further applications.

Laser synthesis of polyyne molecules C2nH2 (n > 2) in liquid hydrocarbons is a complex process in which intense pulsed radiation decomposes the initial carbon-containing substance (the hydrocarbon solvent itself or the solid carbon particles in a suspension). Notwithstanding the fact that the mechanism of pulsed laser ablation in liquids (PLAL) is widely accepted, the effect of the laser parameters on laser-driven polyyne formation is still not understood in detail. Here, we report a study of the polyyne yield as a function of the laser field intensity and exposure dose. Several carbon-containing liquids, including pure n-hexane, pure ethanol, and graphite powder suspended in ethanol, were treated with tightly focused picosecond IR radiation (wavelength of 1064 nm, pulse duration of 10 ps). The synthesis rate was characterized by UV-vis optical absorption spectroscopy. The yields of the polyynes were found to vary in exact accordance with the value of the absorbed laser energy, following specific nonlinear or linear laws. The influence of the laser intensity on the partial concentration of polyynes in the solution was analyzed.

High-quality graphene has demonstrated remarkable mechanical, thermal, electronic, and optical properties. These features have paved the road for the introduction of graphene into numerous applications such as optoelectronics and energy devices, photodegradation, bioimaging, photodetectors, sensors, and biosensors. Due to this, graphene research has accelerated exponentially, with the aim of reaching a sustainable large-scale production process of high-quality graphene that can produce graphene-based technologies at an industrial scale. There exist numerous routes for graphene fabrication; however, pulsed laser ablation in liquids (PLAL) has emerged as a simple, fast, green, and environmentally friendly method as it does not require the use of toxic chemicals. Moreover, it does not involve the use of expensive vacuum chambers or clean rooms. However, the great advantage of PLAL is its ability to control the size, shape, and structure of the produced nanostructures through the choice of laser parameters and liquid used. Consequently, this review will focus on recent research on the synthesis of graphene nanosheets and graphene quantum dots via PLAL and the effect of experimental parameters such as laser wavelength, pulse width, pulse energy, repetition rate, irradiation time, and liquid media on the produced nanostructures. Moreover, it will discuss extended PLAL techniques which incorporate other methods into PLAL. Finally, different applications that utilize nanostructures produced by PLAL will be highlighted. We hope that this review will provide a useful guide for researchers to further develop the PLAL technique and the fabrication of graphene-based materials. [ABSTRACT FROM AUTHOR]

Owing to a strong photothermal response in the near-IR spectral range and very low toxicity, titanium nitride (TiN) nanoparticles (NPs) synthesized by pulsed laser ablation in liquids (PLAL) present a novel appealing object for photo-induced therapy of cancer, but the properties of these NPs still require detailed investigation. Here, we have elaborated methods of femtosecond laser ablation from the TiN target in a variety of liquid solutions, including acetonitrile, dimethylformamide, acetone, water, and H2O2, to synthesize TiN NPs and clarify the effect of liquid type on the composition and properties of the formed NPs. The ablation in all solvents led to the formation of spherical NPs with a mean size depending on the liquid type, while the composition of the NPs ranged from partly oxidized TiN to almost pure TiO2, which conditioned variations of plasmonic peak in the region of relative tissue transparency (670–700 nm). The degree of NP oxidation depended on the solvent, with much stronger oxidation for NPs prepared in aqueous solutions (especially in H2O2), while the ablation in organic solvents resulted in a partial formation of titanium carbides as by-products. The obtained results contribute to better understanding of the processes in reactive PLAL and can be used to design TiN NPs with desired properties for biomedical applications. [ABSTRACT FROM AUTHOR]

Hybrid multimodal nanoparticles, applicable simultaneously to the noninvasive imaging and therapeutic treatment, are highly demanded for clinical use. Here, Fe-Au core-satellite nanoparticles prepared by the method of pulsed laser ablation in liquids were evaluated as dual magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents and as sensitizers for laser-induced hyperthermia of cancer cells. The biocompatibility of Fe-Au nanoparticles was improved by coating with polyacrylic acid, which provided excellent colloidal stability of nanoparticles with highly negative ζ-potential in water (−38 ± 7 mV) and retained hydrodynamic size (88 ± 20 nm) in a physiological environment. The ferromagnetic iron cores offered great contrast in MRI images with r2 = 11.8 ± 0.8 mM−1 s−1 (at 1 T), while Au satellites showed X-ray attenuation in CT. The intravenous injection of nanoparticles enabled clear tumor border visualization in mice. Plasmonic peak in the Fe-Au hybrids had a tail in the near-infrared region (NIR), allowing them to cause hyperthermia under 808 nm laser exposure. Under NIR irradiation Fe-Au particles provided 24.1 °C/W heating and an IC50 value below 32 µg/mL for three different cancer cell lines. Taken together, these results show that laser synthesized Fe-Au core-satellite nanoparticles are excellent theranostic agents with multimodal imaging and photothermal capabilities. [ABSTRACT FROM AUTHOR]

A highly selective and multifunctional electrocatalyst is constructed by combining a single-phase Ni 3 S 2 obtained via pulsed laser ablation in liquids (PLAL) with different contents of nickel tetraphenylporphyrin (NiTPP) complex. The catalytic performance is assessed in consecutive hydrogen (HER) and oxygen evolution (OER), as well as benzyl alcohol (B.Alc) oxidation reactions (AOR). The optimal NiS-NiTPP10% exhibits the highest activity with overpotentials of 435, 320, and 170 mV, respectively. Moreover, NiS-NiTPP10% favors alcohol oxidation reaction and produces benzoic acid (B.Ac) at a yield rate of 2.23 mM h−1 cm−2 with 100% mass balance, 98.3% Faradaic efficiency (FE), and 99.8% selectivity. Finally, the system with simultaneous H 2 evolution and value-added B.Ac production is successfully employed in a NiS-NiTPP10%||NiS-NiTPP10% electrolyzer, resulting in a high FE of 81% and 99%, and a yield rate of 0.42 and 4.03 mM h−1 cm−2, respectively, at a lower cell voltage of 193 mV than the standard water electrolyzer. The pyrrole rings of NiTPP could act as the terminal for the B.Alc molecule, and the Ni2+/Ni3+ redox pair of Ni 3 S 2 could accelerate the oxidation process. Hence, both Ni 3 S 2 and NiTPP boost the performance of NiS-NiTPP10% via charge-density modulation and strong synergistic effects. [Display omitted] • Pulsed laser-induced Ni 3 S 2 was decorated with nickel tetraphenylporphyrin (NiTPP). • NiS-NiTPP as efficient catalysts for HER, OER, and benzyl alcohol oxidation (AOR). • AOR produces benzoic acid at 2.23 mMh−1cm−2 rate with 99.8% selectivity. • NiS-NiTPP10%||NiS-NiTPP10% electrolyzer for H 2 fuel and benzoic acid production. [ABSTRACT FROM AUTHOR]

One of the most versatile and effective methods to improve LIBS analysis of liquids is Thin Film Microextraction (TFME). This approach generally uses carbon-based adsorbent films to extract analytes from a liquid sample and bind them into a solid matrix, which is ideal for LIBS. In a previous work, we demonstrated the feasibility of TFME supports based on graphene prepared by Pulsed Laser Ablation in Liquid (PLAL) for LIBS analysis. In this paper, we optimized the preparation of such supports for the analysis of heavy metals in aqueous samples (i.e. chromium, lead and nickel), by analyzing both standard solutions and real samples. The feasibility of coupling TFME with NELIBS approach was also exploited. The procedure was applied to the analysis of both mineral water and well water samples. We obtained a standardized procedure for the extraction of three analytes (Pb, Cr and Ni) and estimated LOD values in spiked mineral water of the order of 0.6 mg/L for LIBS and 0.2 mg/L for NELIBS. [Display omitted] • Graphene nano-sheets and silver nanoparticles are prepared by laser ablation. • TFME preparation and extraction procedure optimized using experimental design. • TFME-LIBS and NELIBS performances are tested with stock solutions and simulated real samples. • LODs lower than 1 mg/L are obtained for Ni, Cr and Pb. [ABSTRACT FROM AUTHOR]

In this study, pulsed laser ablation in liquid (PLAL) was performed to synthesize nanoparticles by irradiating a laser to a target material in a specific solvent. The effect of laser parameters on the size and deviation of nanoparticles was quantitatively analyzed using the design of experiments. The increased laser energy induced rapid plasma expansion, reducing the size of the synthesized nanoparticles. However, when the laser energy exceeds a critical value, the ablation rate was reduced because the primary synthesized nanoparticles absorb the subsequent laser energy. When the laser beam diameter increased, the probability that the vapor atoms or ions collide with each other increased, but the change in the final particle size was minimal because most of the generated particles were fragmented by exposure to subsequent laser beams. The size deviation of the nanoparticles produced by PLAL decreased with increasing laser energy and increasing beam diameter as the effect of the subsequent laser beam became prominent under this process condition. A methodology for determining the process conditions for producing aluminum (Al) nanoparticles with the desired size and minimum deviation was proposed and validated through analysis of variance (ANOVA) and simple mathematical modeling. [ABSTRACT FROM AUTHOR]

• DSSCs, in which TiO 2 is co-sensitized by N719 dye and CdS-QD was fabricated. • Photovoltaic conversion efficiency of 7.1 % was achieved in the new configuration. • This accounts for 33% increase of efficiency compared to usual TiO 2 based DSSC. • Optimum band structures and charge transfers are attributed for this performance. • Band positions and charge transfer mechanisms in co-sensitized DSSC is explained. In this study, a new configuration of dye sensitized solar cells (DSSCs), in which a TiO 2 photoanode is co-sensitized by N719 organic dye and CdSe quantum dots (CdSe-QDs), was fabricated. The photovoltaic performance of the cell, which was co-sensitized with an optimum concentration of CdSe-QDs, was found to be superior to that of the cell with a photoanode sensitized using N719 dye. The superior performance can be attributed to the energy-compatible band structures of the N719 dye molecule and the CdSe-QDs, selective transfer of a significant number of photogenerated electrons from the energy state of the dye molecule to the conduction band (CB) of CdSe-QDs, and improved absorbance of the CdSe-QDs in the visible-light spectrum. This initial inflow of electrons to the dye was found to enrich the subsequent dye-mediated electron transfer to TiO 2 , thus contributing to the enhanced photocurrent in the DSSC. The novel material implemented in this study was based on CdSe-QDs, which were used as a co-sensitizer in the photoanode of the DSSC synthesized by pulsed laser ablation in liquid (PLAL). Morphological, structural, elemental, optical and electrochemical characterizations of the photoanodic materials were conducted; and the photovoltaic characteristics of the fabricated cell were determined. The photovoltaic conversion efficiency of the cell co-sensitized by CdSe-QDs at a certain concentration (1 mg/15 ml of ethanol) and N719 dye was found to be 7.09%, which corresponds to a 37% enhancement of the photovoltaic efficiency when compared with the cell sensitized only by the N719 dye. [ABSTRACT FROM AUTHOR]

In this work, three different Nd:YAG laser radiations (λ = 1064, 532, and 355 nm) were analyzed to obtain BN particles using pulsed laser ablation in liquids (PLALs). The effect of the laser energy in two reaction media (deionized water and acetone) during BN synthesis was analyzed through their structural, optical and photoluminescence properties. XRD patterns show the main reflections of h-BN and the existence of impurity phases that corresponds to c-BN or e-BN structures. The nanosecond laser energy is enough to transform h-BN hybridization from sp2 to sp3 and form new phases. The crystallite sizes (CS) of the h-BN particles grown in deionized water are between 66.4–68.8 nm for the three applied Nd:YAG harmonics. Similar CS were observed in colloidal BN particles fabricated in acetone (66.6–67.8 nm). The combination of the laser energy and reaction media modifies the BN particles morphology from platelets randomly oriented (D.W.) to melting-like structures (acetone). Size and melting degree are modified with the laser energy due to the capacity for plasma confinement of each reaction medium. Raman spectroscopy showed two vibrational modes dependent on the laser wavelength confirming that e-BN and c-BN phases coexist in the h-BN matrix. The formation of these secondary phases and morphological features are responsible of the differences in the optical properties. BN nanocrystals growth in D.W. like colloidal medium can act as UV shielding. Photoluminescence of BN structures (1064 nm) is observed in the range of 300–550 nm with a maximum emission at 3.26 eV. Due to the high structure disorder, the BN structures showed a broad emission with an intense luminescence that remain fairly constant after 48 h; resulting in blue luminescence character. [ABSTRACT FROM AUTHOR]

Cost‐effective, highly efficient and stable non‐noble metal‐based catalysts for the oxygen evolution reaction (OER) are very crucial for energy storage and conversion. Here, an amorphous cobalt nickel phosphate (CoNiPO4), containing a considerable amount of high‐valence Ni3+ species as an efficient electrocatalyst for OER in alkaline solution, is reported. The catalyst was converted from Co‐doped Ni2P through pulsed laser ablation in liquid (PLAL) and exhibits a large specific surface area of 162.5 m2 g−1 and a low overpotential of 238 mV at 10 mA cm−2 with a Tafel slope of 46 mV dec−1, which is much lower than those of commercial RuO2 and IrO2. This work demonstrates that PLAL is a powerful technology for generating amorphous CoNiPO4 with high‐valence Ni3+, thus paving a new way towards highly effective OER catalysts. [ABSTRACT FROM AUTHOR]

2D-MoS 2 nanostructures are attractive co-catalysts for photocatalytic hydrogen evolution due to their suitable water reduction potentials and high stability. However, the catalytic activity of MoS 2 is greatly limited by the catalytically inert basal planes. Doping of transition-metal ions into MoS 2 structure is an effective way to activating the basal planes. To this end, the formation of size-controlled metal nanocrystals with clean surface and mono dispersed nature is a current challenge. Here we utilized pulsed laser ablation in liquid approach to generate high purity size controlled cobalt nanocrystal by adjusting the laser fluences and systematically evaluate the effect of cobalt nanocrystals size and concentration on MoS 2 to activate the basal planes. A set of Co-MoS 2 /CdS nanorods with different cobalt size were examined, and an optimal cobalt size of 3.1 nm was obtained. The optimized CdS/Co-MoS 2 nanocomposite showed a very high H 2 production rate (275 mmol h−1 g−1) with outstanding stability. To the best of our knowledge, this is the best performance reported for CdS/MoS 2 based nanocomposites. The remarkable hydrogen evolution rate and stability may be due to reduced recombination rate and greatly increased density of catalytic active sites which is determined by photoluminescence and impedance spectroscopy. Finally, we believe that the strategies applied in the present study to form robust photocatalysts and its utilization in solar driven hydrogen production would inspire the development of other low-cost photocatalysts for renewable fuel production. Unlabelled Image • Size controlled cobalt nanocrystals doped MoS 2 ultrathin nanosheets on CdS nanorods were constructed. • A synthesized nanohybrid showed high activity for H 2 production under sunlight irradiation. • Co-MoS 2 component acted as efficient photo-charge separator and migrator. • A very high H 2 production rate (275 mmol h−1 g−1) with outstanding stability was noticed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanoparticles (NP) with demanded properties can be produced due to Pulsed Laser Ablation in Liquids (PLAL). • There are two main mechanisms of NPs production that are sensitive to irradiation conditions. • There are such laser processing regimes that allow for manipulation with the mechanisms of laser ablation. • Activation of the appropriate mechanism of PLAL allows for formation of NPs with controllable size characteristics. Pulsed Laser Ablation in Liquids (PLAL) manifested itself as a powerful tool for the synthesis of nanoparticles (NPs) from a variety of materials of high demand in biomedicine. The mechanisms and regimes of nanostructures formation, however, still require clarification in order to better control the final NPs characteristics. Here, we present a numerical study of femtosecond laser-ablative production of metal (gold) NPs in water ambient using an advanced atomistic continuum approach, combining the Molecular Dynamics (MD) and Two Temperature Model into the frames of a single MD-TTM computational method. The model describes non-equilibrium laser-induced phase transitions at atomic level and accounts for the effect of free carriers in continuum. With the MD-TTM model we investigated the effect of slight porosity arising due to a partial overlap of laser craters during the scanning of laser beam over the target surface under a high repetition rate of laser pulses. For that purpose, we perform a simulation of 270 fs laser pulse interaction with solid and porous gold targets at the incident fluence of 2.5 J/cm2. The obtained results revealed the manifestation of different regimes of ablation and different yield of the obtained NPs. The simulation results are compared with the corresponding experimental data. We found that depending on the scanning speed the ablation can follow thermal and spallation mechanisms of the material ejection, which are responsible for the appearance of fine and course populations of NPs correspondingly. In the case of clean target's surface ablation, when at high scanning speed of 3840 mm/s each pulse hits a fresh area, the material ejection is governed by both mechanisms, which leads to the appearance of bimodal population of NPs. Alternatively, a moderate scanning speed of 840 mm/s results in a partial overlap of the sequential laser spots on the surface and generated slight porosity removes the accumulation of laser-induced stresses. The spallation mechanism of the material ejection is therefore suppressed, which results in generation of a monomodal fine population of NPs with a 20 times larger yield. The obtained data are of importance to predict and control size characteristics of laser-synthesized nanomaterials. [ABSTRACT FROM AUTHOR]

Herein, we report the fabrication and characterization of novel polycaprolactone (PCL)-based nanofibers functionalized with bare (ligand-free) titanium nitride (TiN) nanoparticles (NPs) for tissue engineering applications. Nanofibers were prepared by a newly developed protocol based on the electrospinning of PCL solutions together with TiN NPs synthesized by femtosecond laser ablation in acetone. The generated hybrid nanofibers were characterised using spectroscopy, microscopy, and thermal analysis techniques. As shown by scanning electron microscopy measurements, the fabricated electrospun nanofibers had uniform morphology, while their diameter varied between 0.403 ± 0.230 µm and 1.1 ± 0.15 µm by optimising electrospinning solutions and parameters. Thermal analysis measurements demonstrated that the inclusion of TiN NPs in nanofibers led to slight variation in mass degradation initiation and phase change behaviour (Tm). In vitro viability tests using the incubation of 3T3 fibroblast cells in a nanofiber-based matrix did not reveal any adverse effects, confirming the biocompatibility of hybrid nanofiber structures. The generated hybrid nanofibers functionalized with plasmonic TiN NPs are promising for the development of smart scaffold for tissue engineering platforms and open up new avenues for theranostic applications.

Owing to strong plasmonic absorption and excellent biocompatibility, gold nanostructures are among best candidates for photoacoustic bioimaging and photothermal therapy, but such applications require ultrapure Au-based nanoformulations of complex geometry (core-shells, nanorods) in order to shift the absorption band toward the region of relative tissue transparency (650–1000 nm). Here, we present a methodology for the fabrication of Si@Au core-satellite nanostructures, comprising of a Si core covered with small Au nanoparticles (NP), based on laser ablative synthesis of Si and Au NPs in water/ethanol solutions, followed by a chemical modification of the Si NPs by 3-aminopropyltrimethoxysilane (APTMS) and their subsequent decoration by the Au NPs. We show that the formed core-satellites have a red-shifted plasmonic absorption feature compared to that of pure Au NPs (520 nm), with the position of the peak depending on APTMS amount, water−ethanol solvent percentage and Si−Au volume ratio. As an example, even relatively small 40-nm core-satellites (34 nm Si core + 4 nm Au shell) provided a much red shifted peak centered around 610 nm and having a large tail over 700 nm. The generation of the plasmonic peak is confirmed by modeling of Si@Au core-shells of relevant parameters via Mie theory. Being relatively small and exempt of any toxic impurity due to ultraclean laser synthesis, the Si@Au core-satellites promise a major advancement of imaging and phototherapy modalities based on plasmonic properties of nanomaterials.

Modern trends in optical bioimaging require novel nanoproducts combining high image contrast with efficient treatment capabilities. Silicon nanoparticles are a wide class of nanoobjects with tunable optical properties, which has potential as contrasting agents for fluorescence imaging and optical coherence tomography. In this paper we report on developing a novel technique for fabricating silicon nanoparticles by means of picosecond laser ablation of porous silicon films and silicon nanowire arrays in water and ethanol. Structural and optical properties of these particles were studied using scanning electron and atomic force microscopy, Raman scattering, spectrophotometry, fluorescence, and optical coherence tomography measurements. The essential features of the fabricated silicon nanoparticles are sizes smaller than 100 nm and crystalline phase presence. Effective fluorescence and light scattering of the laser-ablated silicon nanoparticles in the visible and near infrared ranges opens new prospects of their employment as contrasting agents in biophotonics, which was confirmed by pilot experiments on optical imaging.

Graphical abstract Highlights • Realization of the first laser-based proton exchange membrane fuel cell. • Higher long-time stability in electrochemistry than a commercial FC catalyst. • Laser-based PEMFC shows 20% higher mass-specific power density in a real fuel cell application. • Particle dissolution and corrosion effects after an aging process are proved. Abstract For the first time, surfactant-free platinum nanoparticles (Pt-NPs) prepared by pulsed laser ablation in liquids were employed in a real proton exchange membrane fuel cell (PEMFC). Laser-generated Pt-NPs show a larger size in comparison to a commercial Pt/C catalyst, being 6.6 nm for the laser-based and 3.8 nm for the reference, respectively. The laser-based Pt/C electrocatalyst was synthesized by colloidal deposition of laser-generated Pt-NPs onto carbonic Vulcan as support. The durability tests showed a much better stability of the laser-based catalyst in the electrochemical active surface area (ECSA) with an ECSA retention of 88% of its initial area. This better durability is probably caused by a reduced Pt dissolution rate which is higher for the reference catalyst containing NPs smaller than 3 nm. The occurrence of Pt dissolution is further indicated by X-ray photoelectron spectroscopy (XPS) of the electrodes after electrocatalytic testing showing no Pt signal in case of the reference catalyst. Performance tests of both PEMFC show a 20% higher mass-specific power density for the laser-based proton exchange membrane fuel cell. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Laser-generated ligand-free Pt nanoparticles as benchmarking catalyst. • Homogeneous particle distribution on almost defect-free gas phase synthesized graphene. • Graphene supported Pt nanoparticles show enhanced stability during ORR. • Improved stability is tentatively attributed to better corrosion resistance. Abstract Ligand-free platinum nanoparticles were prepared by pulsed laser ablation in liquids (PLAL) and employed as a benchmarking catalyst to evaluate the durability of a new gas-phase synthesized graphene support in oxygen reduction conditions. Raman measurements showed that the graphene, as compared to Vulcan, was almost defect free. Transmission electron microscopy and initial electrochemically active surface area measurements confirmed good dispersion of the catalysts on both supports. During durability tests, graphene supported Pt nanoparticles showed much better ECSA retention (75% on graphene as compared to 38% on Vulcan), ultimately retaining a higher ECSA than a commercial sample subjected to the same procedure. [ABSTRACT FROM AUTHOR]

Highlights • Laser-synthesized hard ceramic particles tested for high-pressure applications. • Huge potential of nano- and submicrometer spheres as additives in lubricants. • High impact of particle size and morphology on wear and fatigue failure on the tooth flank. Abstract The lubricant is a central element in the transmission design. It primarily separates the two contact partners through a pressure-induced solidification in the lubrication gap, thus enabling the operation of heavily loaded sliding-rolling contacts. On the one hand, the quality and properties of a lubricant depend on the base oils, which differ by their viscosity and process-technological parameters. The addition of particulate additives gives the lubricants further functional properties that are not contained in the base oil. In this study, the influence of laser-synthesized yttria-stabilized zirconia nano- or submicrometer spheres as dispersed functional elements in the lubricant is studied, and their impact on wear and fatigue on the tooth flank is investigated. The work includes systematic investigations on the influence of the particle's shape and size by running tests on a FZG gear test rig. Finally, the potential of the laser-generated particles as a lubricant additive is evaluated in a first conclusion. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Silver nanoparticles synthesized using laser ablation synthesis in isopropanol, in absence of additional capping agents, were found to be stable with respect to both aggregation and silver oxidation over several months. The rationale for this extreme stability of metal nanoparticles suspended in organic solvents was challenging. On the basis of theoretical considerations and basic experiments it is proposed that the stabilization of silver nanoparticles involves the formation of an organic coating generated by the interaction of isopropanol molecules with the pulsed, high-energy laser beam. This coating prevents, on the one hand, any chemical reaction on colloidal nanoparticles (e.g. silver oxidation); on the other hand, the presence of the organic shell with a nature akin to that of the organic solvent led to weaker Van der Walls interactions between approaching nanoparticles enabling a larger stability than for naked metallic nanoparticles. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) were synthesized by pulsed laser ablation in liquids technique (PLAL) using the laser parameter: irradiation time, power source and wavelength of nanosecond laser pulses. Nanocomposite films of poly (n-vinyl carbazole) (PVK) doped with synthesized AgNPs were prepared using casting method. Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) had been used to investigate the Spectroscopic and thermal characterizations of the prepared PVK/Ag nanocomposites samples. The IR spectra illustrated that there is a combination between PVK matrix and silver nanoparticles. Also, itillustrated that the band at 3052 cm−1 of PVK was shifted towards higher wavenumber by about (15-25) cm−1 at the time of irradiation 40 min, power 570 mW and wavelength 532 nm. SEM detected the existence of Ag nanoparticles that leading to changes in morphology of the surface. The thermodynamic parameters: activation energy E*, entropyΔS*, enthalpy ΔH* and Gibbs free energy ΔG* that obtained from TG data in second decomposition step according to Coat’s-Redfern model were helpful in assigning the bond strength, ordering and thermal stability of the investigated samples. It was found the joint effect of both elevated temperature and coordination of Ag nanoparticles in PVK matrix were responsible for weakening and strengthening of the composite system. [ABSTRACT FROM AUTHOR]

Abstract The modification of selective laser sintering (SLS) powder materials by nanoadditives offers the possibility to adapt the powder properties to the laser sintering process or the resulting part properties. To avoid agglomeration of the nanofiller, a new approach in which surfactant-free laser-generated colloidal nanoparticles are adsorbed onto the polymer surface directly in an aqueous solution is demonstrated. Based on this novel approach, polyamide 12 (PA12) powders are decorated with metal and oxide nanoparticles and processed via SLS. Electron microscopy and confocal laser scanning imaging are utilized to analyze the dispersion of the filler. [ABSTRACT FROM AUTHOR]

Abstract A new route for the synthesis of powder composites suitable for processing with laser additive manufacturing is demonstrated. The powder composites, consisting of micrometer-sized stainless steel powder, homogenously decorated with nano-scaled Y 2 O 3 powder particles, are manufactured by laser processing of colloids and electrostatic deposition. Consolidated by laser metal deposition and selective laser melting, the resulting specimens show superior mechanical properties at elevated temperatures, caused by the nano-sized, homogenously distributed dispersoids. [ABSTRACT FROM AUTHOR]

Ag/SiO x nanopowders were obtained from Ag and Si/SiO 2 colloids synthesized via pulsed laser ablation in water. The resulting composite powder was annealed at different temperatures in the region of 100–900 °C. The composition and structure of the obtained materials were studied. The interaction between silica and silver species taking place during composite formation was investigated. A stabilization of Ag nanoparticles in mixed colloids due to their interaction with soluble silicon oxide compounds was found. It was also revealed that the contact between silver and Si/SiO 2 particles resulted in the decrease of the temperature at which the formation of additional oxygen-deficient centres occurs in the silica structure. New types of defects, namely 3-membered cycles and non-bridging oxygen groups, appeared as a result of Ag and Si/SiO 2 surface interaction at 700 °C. Thus, silver nanoparticles facilitated the formation of defects in the structure of SiO 2 . [ABSTRACT FROM AUTHOR]

For a known material, the size distribution of a nanoparticle colloid is a crucial parameter that defines its properties. However, measured size distributions are not easy to interpret as one has to consider weighting (e.g. by light absorption, scattering intensity, volume, surface, number) and the way size information was gained. The radius of a suspended nanoparticle can be given as e.g. sphere equivalent, hydrodynamic, Feret or radius of gyration. In this study, gold nanoparticles in water are synthesized by pulsed-laser ablation (LAL) and fragmentation (LFL) in liquids and characterized by various techniques (scanning transmission electron microscopy (STEM), small-angle X-ray scattering (SAXS), analytical disc centrifugation (ADC), dynamic light scattering (DLS) and UV–vis spectroscopy with Mie-Gans Theory) to study the comparability of different analytical techniques and determine the method that is preferable for a given task related to laser-generated nanoparticles. In particular, laser-generated colloids are known to be bimodal and/or polydisperse, but bimodality is sometimes not analytically resolved in literature. In addition, frequently reported small size shifts of the primary particle mode around 10 nm needs evaluation of its statistical significance related to the analytical method. Closely related to earlier studies on SAXS, different colloids in defined proportions are mixed and their size as a function of the nominal mixing ratio is analyzed. It is found that the derived particle size is independent of the nominal mixing ratio if the colloid size fractions do not overlap considerably. Conversely, the obtained size for colloids with overlapping size fractions strongly depends on the nominal mixing ratio since most methods cannot distinguish between such fractions. Overall, SAXS and ADC are very accurate methods for particle size analysis. Further, the ability of different methods to determine the nominal mixing ratio of sizes fractions is studied experimentally. [ABSTRACT FROM AUTHOR]