Bimetallic Coupling Strategy Modulating Electronic Construction to Accelerate Sulfur Redox Reaction Kinetics for High-Energy Flexible Li-S Batteries.

Lithium-sulfur (Li-S) batteries are considered the most promising energy storage battery due to their low cost and high theoretical energy density. However, the low utilization rate of sulfur and slow redox kinetics have seriously limited the development of Li-S batteries. Herein, the electronic state modulation of metal selenides induced by the bi-metallic coupling strategy is reported to enhance the redox reaction kinetics and sulfur utilization, thereby improving the electrochemical performance of Li-S batteries. Theoretical calculations reveal that the electronic structure can be modulated by Ni-Co coupling, thus lowering the conversion barrier of lithium polysulfides (LiPSs) and Li+, and the synergistic interaction between NiCoSe nanoparticles and nitrogen-doped porous carbon (NPC) is facilitating to enhance electron transport and ion transfer kinetics of the NiCoSe@NPC-S electrodes. As a result, the assembled Li-S batteries based on NiCoSe@NPC-S exhibit high capacities (1020 mAh g-1 at 1 C) and stable cycle performance (80.37% capacity retention after 500 cycles). The special structural design and bimetallic coupling strategy promote the batteries working even under lean electrolyte (7.2 µL mg-1) with a high sulfur loading (6.5 mg cm-2). The proposed bimetallic coupling strategy modulating electronic construction with N-doping porous carbon has jointly contributed the good redox reaction kinetics and high sulfur utilization.

Platinum Electrocatalyst Promoting Redox Kinetics of Li2S and Regulating Li2S Nucleation for Lithium-Sulfur Batteries.

The development of lithium-sulfur batteries (LSBs) is impeded by the shuttle effect of polysulfides (LiPSs) and the sluggish nucleation of Li2S. To address these challenges, incorporating electrocatalysts into sulfur host materials represents an effective strategy for promoting polysulfide conversion, in tandem with the rational design of multifunctional sulfur host materials. In this study, Pt nanoparticles are integrated into biomass-derived carbon materials by solution deposition method. Pt, as an electrocatalyst, not only enhances the electrical conductivity of sulfur cathodes and effectively immobilizes LiPSs but also catalyzes the redox reactions of sulfur species bidirectionally. Additionally, Pt helps regulate the 3D deposition and growth of Li2S while reducing the reaction energy barrier. Consequently, this accelerates the conversion of LiPSs in LSBs. Furthermore, the catalytic ability of Pt for the redox reactions of sulfur species, along with its influence on the 3D deposition and growth of Li2S, is elucidated using electrochemical kinetic analyses and classical models of electrochemical deposition. The cathodes exhibit a high initial specific capacity of 1019.1 mAh g-1 at 1 C and a low decay rate of 0.045% over 1500 cycles. This study presents an effective strategy to regulate Li2S nucleation and enhance the kinetics of polysulfide conversion in LSBs.

Enhanced osteointegration and osteogenesis of osteoblast cells by laser-induced surface modification of Ti implants.

Dental and orthopedic implants have become routine medical technologies for tooth replacement and bone fixation. Despite significant progress in implantology, achieving sufficient osseointegration remains a challenge, often leading to implant failure over the long term. Nanotechnology offers the potential to mimic the natural patterns of living tissues, providing a promising platform for tissue engineering and implant surface design. Among the various methods for developing nanostructures, High-Regular Laser-Induced Periodic Surface Structures (HR-LIPSS) techniques stand out for their ability to fabricate highly ordered nanostructures with excellent long-range repeatability and production efficiency. In this study, we utilized an innovative technical approach to generate traditional laser-induced superficial LIPSS nanostructures, followed by detailed surface analysis using classical microscopy and physicochemical methods. Our findings demonstrate for the first time that nanostructured LIPSS surfaces can significantly enhance cell adhesion and proliferation while providing an optimal environment for cell metabolism. Given the high reproducibility, low cost, and potential of HR-LIPSS techniques to support cell growth and differentiation, this novel technology has the potential to impact both the industrial development of new implants and clinical outcomes after implantation.

Synergistically Accelerating Adsorption-Electrocataysis of Sulfur Species via Interfacial Built-In Electric Field of SnS2 -MXene Mott-Schottky Heterojunction in Li-S Batteries.

Developing efficient heterojunction electrocatalysts and uncovering their atomic-level interfacial mechanism in promoting sulfur-species adsorption-electrocatalysis are interesting yet challenging in lithium-sulfur batteries (LSBs). Here, multifunctional SnS2 -MXene Mott-Schottky heterojunctions with interfacial built-in electric field (BIEF) are developed, as a model to decipher their BIEF effect for accelerating synergistic adsorption-electrocatalysis of bidirectional sulfur conversion. Theoretical and experimental analysis confirm that because Ti atoms in MXene easily lost electrons, whereas S atoms in SnS2 easily gain electrons, and under Mott-Schottky influence, SnS2 -MXene heterojunction forms the spontaneous BIEF, leading to the electronic flow from MXene to SnS2 , so SnS2 surface easily bonds with more lithium polysulfides. Moreover, the hetero-interface quickly propels abundant Li+ /electron transfer, so greatly lowering Li2 S nucleation/decomposition barrier, promoting bidirectional sulfur conversion. Therefore, S/SnS2 -MXene cathode displays a high reversible capacity (1,188.5 mAh g-1 at 0.2 C) and a stable long-life span with 500 cycles (≈82.7% retention at 1.0 C). Importantly, the thick sulfur cathode (sulfur loading: 8.0 mg cm-2 ) presents a large areal capacity of 7.35 mAh cm-2 at lean electrolyte of 5.0 µL mgs -1 . This work verifies the substantive mechanism that how BIEF optimizes the catalytic performance of heterojunctions and provides an effective strategy for deigning efficient bidirectional Li-S catalysts in LSBs.

Self-Aligned Plasmonic Lithography for Maskless Fabrication of Large-Area Long-Range Ordered 2D Nanostructures.

This paper proposes a one-step maskless 2D nanopatterning approach named self-aligned plasmonic lithography (SPL) by line-shaped ultrafast laser ablation under atmospheric conditions for the first time. Through a theoretical calculation of electric field and experimental verification, we proved that homogeneous interference of laser-excited surface plasmon polaritons (SPPs) can be achieved and used to generate long-range ordered 2D nanostructures in a self-aligned way over a wafer-sized area within several minutes. Moreover, the self-aligned nanostructures can be freely transferred between embossed nanopillars and engraved nanoholes by modulating the excitation intensity of SPPs interference through altering the incident laser energy. The SPL technique exhibits further controllability in the shape, orientation, and period of achievable nanopatterns on a wide range of semiconductors and metals by tuning processing parameters. Nanopatterned films can further act as masks to transfer structures into other bulk materials, as demonstrated in silica.

Metal-Organic Frameworks Functionalized Separators for Lithium-Sulfur Batteries.

Lithium sulfur batteries (LSBs) have attracted tremendous attention owing to their high theoretical specific capacity and specific energy. However, their practical applications are hindered by poor cyclic life, mainly caused by polysulfide shuttling. The development of advanced materials to mitigate the polysulfide shuttling effect is urgently demanded. Metal-organic frameworks (MOFs) have been exploited as multifunctional materials for the decoration of separators owing to their high surface area, structural diversity, tunable pore size, and easy tailor ability. In this review, we aim to present the state-of-the-art MOF-based separators for LSBs. Particular attention is paid to the rational design (pore aperture, metal node, functionality, and dimension) of MOFs with enhanced ability for anchoring polysulfides and facilitating Li+ transportation. Finally, the challenges and perspectives are provided regarding to the future design MOF-based separators for high-performance LSBs.

Mammalian Cell Interaction with Periodic Surface Nanostructures.

Here, we report on the nanopatterning of different aromatic polymer substrates achieved by KrF excimer laser treatment. The conditions for the construction of the laser-induced periodic surface structures, the so-called LIPSS pattern, were established by optimized laser fluence and a number of pulses. The polymer substrates were polyethylene naphthalate (PEN), polyethersulfone (PES), and polystyrene (PS), which were chosen since they are thermally, chemically, and mechanically resistant polymers with high absorption coefficients at the excimer laser wavelength. The surface morphology of the treated substrates was investigated by atomic force microscopy and scanning electron microscopy, and the roughness and effective surface area on the modified samples were determined. Elemental concentration was characterized by energy-dispersive (EDX) analysis, surface chemistry was determined with X-ray photoelectron spectroscopy (XPS). The samples with the formation of LIPSS induced by 10 mJ·cm-2 with 1000, 3000, and 6000 pulses were used for subsequent in vitro cytocompatibility tests using human cells from osteosarcoma (U-2 OS). The LIPSS pattern and its ability of significant cell guidance were confirmed for some of the studied samples. Cell morphology, adhesion, and proliferation were evaluated. The results strongly contribute to the development of novel applications using nanopatterned polymers, e.g., in tissue engineering, cell analysis or in combination with metallization for sensor construction.

Impact of Pre-Patterned Structures on Features of Laser-Induced Periodic Surface Structures.

The efficiency of light coupling to surface plasmon polariton (SPP) represents a very important issue in plasmonics and laser fabrication of topographies in various solids. To illustrate the role of pre-patterned surfaces and impact of laser polarisation in the excitation of electromagnetic modes and periodic pattern formation, Nickel surfaces are irradiated with femtosecond laser pulses of polarisation perpendicular or parallel to the orientation of the pre-pattern ridges. Experimental results indicate that for polarisation parallel to the ridges, laser induced periodic surface structures (LIPSS) are formed perpendicularly to the pre-pattern with a frequency that is independent of the distance between the ridges and periodicities close to the wavelength of the excited SPP. By contrast, for polarisation perpendicular to the pre-pattern, the periodicities of the LIPSS are closely correlated to the distance between the ridges for pre-pattern distance larger than the laser wavelength. The experimental observations are interpreted through a multi-scale physical model in which the impact of the interference of the electromagnetic modes is revealed.

In Vitro Bioactivity and Biocompatibility of Bio-Inspired Ti-6Al-4V Alloy Surfaces Modified by Combined Laser Micro/Nano Structuring.

The bioactivity and biocompatibility play key roles in the success of dental and orthopaedic implants. Although most commercial implant systems use various surface microstructures, the ideal multi-scale topographies capable of controlling osteointegration have not yielded conclusive results. Inspired by both the isotropic adhesion of the skin structures in tree frog toe pads and the anisotropic adhesion of the corrugated ridges on the scales of Morpho butterfly wings, composite micro/nano-structures, including the array of micro-hexagons and oriented nano-ripples on titanium alloy implants, were respectively fabricated by microsecond laser direct writing and femtosecond laser-induced periodic surface structures, to improve cell adherence, alignment and proliferation on implants. The main differences in both the bioactivity in simulated body fluid and the biocompatibility in osteoblastic cell MC3T3 proliferation were measured and analyzed among Ti-6Al-4V samples with smooth surface, micro-hexagons and composite micro/nano-structures, respectively. Of note, bioinspired micro/nano-structures displayed the best bioactivity and biocompatibility after in vitro experiments, and meanwhile, the nano-ripples were able to induce cellular alignment within the micro-hexagons. The reasons for these differences were found in the topographical cues. An innovative functionalization strategy of controlling the osteointegration on titanium alloy implants is proposed using the composite micro/nano-structures, which is meaningful in various regenerative medicine applications and implant fields.

Cell and tissue response to nanotextured Ti6Al4V and Zr implants using high-speed femtosecond laser-induced periodic surface structures.

In this paper, the effect of femtosecond laser nanotexturing of surfaces of Ti6Al4V and Zr implants on their biological compatibility is presented and discussed. Highly regular and homogeneous nanostructures with sub-micrometer period were imprinted on implant surfaces. Surfaces were morphologically and chemically investigated by SEM and XPS. HDFa cell lines were used for toxicity and cell viability tests, and subcutaneous implantation was applied to characterize tissue response. HDFa proliferation and in vivo experiments evidenced the strong influence of the surface topography compared to the effect of the surface elemental composition (metal or alloy). The effect of protein adsorption from blood plasma on cell proliferation is also discussed.

New aspects of femtosecond laser ablation of Si in water: a material perspective.

We report a study of the role of material's conductivity in determining the morphology of nanoparticles and nanostructures produced by ultrafast laser ablation of solids. Nanoparticles and textured surfaces formed by laser ablation display a wide variation in size and morphology depending on the material. In general, these qualities can be grouped as to material type, insulator, semiconductor, or metal; although each has many other different material properties that make it difficult to identify the critical material factor. In this report, we study these nanoparticle/surface structural characteristics as a function of silicon (Si) resistivity, thus honing-in on this critical parameter and its effects. The results show variations in morphology, optical, and nonlinear properties of Si nanoparticles. The yield of colloidal Si nanoparticles increased with an increase in the conductivity of Si. Laser-induced periodic surface structures formed on ablated substrates are also found to be sensitive to the initial conductivity of the material. Further, the laser ablation of Gamma-irradiated Si has been investigated to verify the influence of altered conductivity on the formation of Si nanoparticles. These observations are interpreted using the basic mechanisms of the laser ablation process in a liquid and its intricate relation with the initial density of states and thermal conductivities of the target material.

Oxygen-vacancy-reinforced perovskites promoting polysulfide conversion for lithium-sulfur batteries.

Lithium-sulfur batteries (LSBs) are considered to be one of the most promising energy storage systems because of the ultrahigh energy density. However, their shuttle effect and slow redox kinetics seriously hinder the development of LSBs. To solve these issues, the perovskite La1-xSrxMnO3-δ (x = 0-0.5) with different oxygen vacancy concentrations were prepared by a facile liquid-phase synthesis and followed by the thermal annealing. The La1-xSrxMnO3-δ can not only anchor lithium polysulfides (LiPSs), but also catalyze the conversion of LiPSs. The detailed kinetic analysis and density functional theory calculations reveal that the optimal level of oxygen vacancies can effectively increase the binding energy between perovskites and LiPSs, and effectively promote the LiPS conversion kinetics. The S/La0.6Sr0.4MnO3-δ cathode with a moderate oxygen vacancy concentration exhibits high rate performance and ultrahigh capacity retention of 93.2% after 150 cycles at 0.1 C, which provides a potential for practical applications of LSBs. This work reveals the application of perovskite materials in the development of advanced LSBs.

Sub-diffraction limited nanogroove fabrication of 30 nm features on diamond films using 800 nm femtosecond laser irradiation.

By controlling the 800 nm fs laser energy and applying an isopropyl alcohol environment, controlled sub-diffraction limited lithography with a characteristic structure of approximately 30 nm was achieved on the surface of diamond films, and diamond gratings with a period of 200 nm were fabricated. The fabrication of single grooves with a feature size of 30 nm demonstrates the potential for patterning periodic or nonperiodic structures, and the fabrication of 200 nm periodic grating structures demonstrates the ability of the technique to withstand laser proximity effects. This enhances the technology of diamond film nanofabrication and broadens its potential applications in areas such as optoelectronics and biology.

Wettability Behaviour of Metal Surfaces after Sequential Nanosecond and Picosecond Laser Texturing.

This study examines the wettability behaviour of 304 stainless steel (304SS) and Ti-6Al-4V (Ti64) surfaces after sequential nanosecond (ns) and picosecond (ps) laser texturing; in particular, how the multi-scale surface structures created influence the lifecycle of surface hydrophobicity. The effect of different post-process treatments is also examined. Surfaces were analysed using Scanning Electron Microscopy (SEM), a white light interferometer optical profiler, and Energy Dispersive X-ray (EDX) spectroscopy. Wettability was assessed through sessile drop contact angle (CA) measurements, conducted at regular intervals over periods of up to 12 months, while EDX scans monitored elemental chemical changes. The results show that sequential (ns + ps) laser processing produced multi-scale surface texture with laser-induced periodic surface structures (LIPSS). Compared to the ns laser case, the (ns + ps) laser processed surfaces transitioned more rapidly to a hydrophobic state and maintained this property for much longer, especially when the single post-process treatment was ultrasonic cleaning. Some interesting features in CA development over these extended timescales are revealed. For 304SS, hydrophobicity was reached in 1-2 days, with the CA then remaining in the range of 120 to 140° for up to 180 days; whereas the ns laser-processed surfaces took longer to reach hydrophobicity and only maintained the condition for up to 30 days. Similar results were found for the case of Ti64. The findings show that such multi-scale structured metal surfaces can offer relatively stable hydrophobic properties, the lifetime of which can be extended significantly through the appropriate selection of laser process parameters and post-process treatment. The addition of LIPSS appears to help extend the longevity of the hydrophobic property. In seeking to identify other factors influencing wettability, from our EDX results, we observed a significant and steady rate of increase in the carbon content at the surface over the study period.

Advanced micro- & nanostructuring for enhanced biocompatibility of stainless steel by multi-beam and beamshaping technology.

Biocompatibility is one of the key issues for implants, especially in the case of stainless steel with medium to low biocompatibility, which may lead to a lack of osseointegration and consequently to implant failure or rejection. To precisely control preferential cell growth sites and, consequently, the biocompatibility of prosthetic devices, two types of surfaces were analyzed, containing periodic nanogrooves laser induced periodic surface structure (LIPSS) and square-shaped micropillars. For the fast and efficient production of these surfaces, the unique combination of high energy ultrashort pulsed laser system with multi-beam and beamshaping technology was applied, resulting in increased productivity by 526% for micropillars and 14 570% for LIPSS compared to single beam methods.In vitroanalysis revealed that micro and nanostructured surfaces provide a better environment for cell attachment and proliferation compared to untreated ones, showing an increase of up to 496% in the number of cells compared to the reference. Moreover, the combination of LIPSS and micropillars resulted in a precise cell orientation along the periodic microgroove pattern. The combination of these results demonstrates the possibility of mass production of functionalized implants with control over cell organization and growth. Thus, reducing the risk of implant failure due to low biocompatibility.

Frenkel-Poole Mechanism Unveils Black Diamond as Quasi-Epsilon-Near-Zero Surface.

A recent innovation in diamond technology has been the development of the "black diamond" (BD), a material with very high optical absorption generated by processing the diamond surface with a femtosecond laser. In this work, we investigate the optical behavior of the BD samples to prove a near to zero dielectric permittivity in the high electric field condition, where the Frenkel-Poole (FP) effect takes place. Zero-epsilon materials (ENZ), which represent a singularity in optical materials, are expected to lead to remarkable developments in the fields of integrated photonic devices and optical interconnections. Such a result opens the route to the development of BD-based, novel, functional photonic devices.

Laser-Treated Steel Surfaces Gliding on Snow at Different Temperatures.

With the goal of substituting a hard metallic material for the soft Ultra High Molecular Weight Polyethylene (UHMWPE) presently used to make the bases of skis for alpine skiing, we used two non-thermodynamic equilibrium surface treatments with ultra-short (7-8 ps) laser pulses to modify the surface of square plates (50 × 50 mm2) made of austenitic stainless steel AISI 301H. By irradiating with linearly polarized pulses, we obtained Laser Induced Periodic Surface Structures (LIPSS). By laser machining, we produced a laser engraving on the surface. Both treatments produce a surface pattern parallel to one side of the sample. For both treatments, we measured with a dedicated snow tribometer the friction coefficient µ on compacted snow at different temperatures (-10 °C; -5 °C; -3 °C) for a gliding speed range between 1 and 6.1 ms-1. We compared the obtained µ values with those of untreated AISI 301H plates and of stone grinded, waxed UHMWPE plates. At the highest temperature (-3 °C), near the snow melting point, untreated AISI 301H shows the largest µ value (0.09), much higher than that of UHMWPE (0.04). Laser treatments on AISI 301H gave lower µ values approaching UHMWPE. We studied how the surface pattern disposition, with respect to the gliding direction of the sample on snow, affects the µ trend. For LIPSS with pattern, orientation perpendicular to the gliding direction on snow µ (0.05) is comparable with that of UHMWPE. We performed field tests on snow at high temperature (from -0.5 to 0 °C) using full-size skis equipped with bases made of the same materials used for the laboratory tests. We observed a moderate difference in performance between the untreated and the LIPSS treated bases; both performed worse than UHMWPE. Waxing improved the performance of all bases, especially LIPSS treated.

Surface Nanotexturing of Boron-Doped Diamond Films by Ultrashort Laser Pulses.

Polycrystalline boron-doped diamond (BDD) films were surface nanotextured by femtosecond pulsed laser irradiation (100 fs duration, 800 nm wavelength, 1.44 J cm-2 single pulse fluence) to analyse the evolution of induced alterations on the surface morphology and structural properties. The aim was to identify the occurrence of laser-induced periodic surface structures (LIPSS) as a function of the number of pulses released on the unit area. Micro-Raman spectroscopy pointed out an increase in the graphite surface content of the films following the laser irradiation due to the formation of ordered carbon sites with respect to the pristine sample. SEM and AFM surface morphology studies allowed the determination of two different types of surface patterning: narrow but highly irregular ripples without a definite spatial periodicity or long-range order for irradiations with relatively low accumulated fluences (<14.4 J cm-2) and coarse but highly regular LIPSS with a spatial periodicity of approximately 630 nm ± 30 nm for higher fluences up to 230.4 J cm-2.

Dynamics and Processes on Laser-Irradiated Surfaces.

The modification of solid surfaces via the impacts of intense laser pulses and the dynamics of the relevant processes are reviewed. We start with rather weak interactions on dielectric materials, based on non-linear absorption across the bandgap and resulting in low-level local effects like electron and individual ion emission. The role of such locally induced defects in the cumulative effect of incubation, i.e., the increase in efficiency with the increasing number of laser pulses, is addressed. At higher excitation density levels, due to easier laser-material coupling and higher laser fluence, the energy dissipation is considerable, leading to lattice destabilization, surface relaxation, ablation, and surface modification (e.g., laser-induced periodic surface structures). Finally, a short list of possible applications, namely in the field of wettability, is presented.

Effect of Femtosecond Laser-Irradiated Titanium Plates on Enhanced Antibacterial Activity and Preservation of Bacteriophage Stability.

Titanium (Ti) is widely recognized for its exceptional properties and compatibility with medical applications. In our study, we successfully formed laser-induced periodic surface structures (LIPSS) on Ti plates with a periodicity of 520-740 nm and a height range of 150-250 nm. To investigate the morphology and chemical composition of these surfaces, we employed various techniques, including field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Additionally, we utilized a drop-shape analyzer to determine the wetting properties of the surfaces. To evaluate the antibacterial activity, we followed the ISO 22196:2011 standard, utilizing reference bacterial cultures of Gram-positive Staphylococcus aureus (ATCC 25923) and Gram-negative Escherichia coli (ATCC 25922). The results revealed enhanced antibacterial properties against Staphylococcus aureus by more than 99% and Escherichia coli by more than 80% in comparison with non-irradiated Ti. Furthermore, we conducted experiments using the Escherichia coli bacteriophage T4 (ATCC 11303-B4) and the bacterial host Escherichia coli (ATCC 11303) to investigate the impact of Ti plates on the stability of the bacteriophage. Overall, our findings highlight the potential of LIPSS on Ti plates for achieving enhanced antibacterial activity against common bacterial strains while maintaining the stability of bacteriophages.