Mesoporous LDH Metastructure from Multiscale Assembly of Defective Nanodomains by Laser Shock for Oxygen Evolution Reaction.

Laser is a powerful tool for the synthesis of nanomaterials. The intensive laser pulses delivered to materials within nanoseconds allow the formation of novel structures that are inaccessible for conventional methods. Layered double hydroxide (LDH) nanostructures with high porosity, suitable dopants, and rich defects are desirable for catalysts, however, tremendously difficult in a one-pot synthesis. Here it is found that confined laser shock in solvent leads to the formation of nanoreactors which guide the assembly of multiscale LDH building units, larger nanosheets as frame and smaller nanodomains as building blocks. These nanodomains have rich vacancy defects and are interlocked in a high packed density of 1013  cm-2 , leaving rich mesopores across the nanosheets and coral-like morphology. Like the natural coral reef that has multiscale structure to accommodate different marine organisms, the coral-like LDH metastructure provides large surface area and rich active sites for the interaction with guest molecules. Benefiting from the multiscale porous structure and rational dopant, this LDH catalyst exhibits a low overpotential of 220 mV at 10 mA cm-2 for oxygen evolution reaction (OER), standing as one of the best LDH catalysts to date.

Ultrafast Laser Manufacture of Stable, Efficient Ultrafine Noble Metal Catalysts Mediated with MOF Derived High Density Defective Metal Oxides.

Supported metal nanoparticles (MNPs) undergo severe aggregation, especially when the interaction between MNPs and their supports are limited and weak where their performance deteriorates dramatically. This becomes more severe when catalysts are operated under high temperature. Here, it is reported that MNPs including Pt, Au, Rh, and Ru, with sub-2 nm size can be stabilized on densely packed defective CeO2 nanoparticles with sub-5 nm size via strong coupling by direct laser conversion of corresponding metal ions encapsulated cerous metal-organic frameworks (Ce-MOFs). Ce-MOF serves as an ideal dispersion precursor to uniformly encapsulate noble metal ions in their orderly arranged pores. Ultrafast laser vaporization and cooling forms uniform, ultrasmall, well-mixed, and exceptionally dense nanoparticles of metal and metal oxide concurrently. The laser-induced ultrafast reaction (within tens of nanoseconds) facilitates the precipitation of CeO2 nanoparticles with abundant surficial defects. Due to the well-mixed ultrasmall Pt and CeO2 components with strong coupling, this catalyst exhibits exceptionally high stability and activity both at low and high temperatures (170-1100 °C) for CO oxidation in long-term operation, significantly exceeding catalysts prepared by traditional methods. The scalable feature of laser and huge MOF family make it a versatile method for the production of MNP-based nanocomposites in wide applications.

Nanoscale Laser Metallurgy and Patterning in Air Using MOFs.

We report metallurgy on the nanoscale to generate metal nanoparticles and their simultaneous patterning in a single step. This is achieved by the self-reduction of porous metal-organic framework crystals using nanosecond pulsed laser irradiation. Metal nanoparticles of Fe, Co, Ni, Cu, Zn, Cd, In, Bi, and Pb with uniform sizes (controllable between 3 to 200 nm) and gaps (as narrow as 2 nm) are produced by nine different metal-organic frameworks, where atomically dispersed non-noble metal ions are reduced and gathered across the pores. The instant light absorption and cooling at local positions by a laser allows for precise and efficient patterning of metal nanoparticles. This new method is suitable for device fabrication at a speed of 15 mm2 s-1 on glass, consuming only 1.5 W of power. A large variety of metal nanoparticle three-dimensional architectures are demonstrated, among which one architecture exhibits an enhanced plasmonic effect homogeneously across the entire pattern for the detection of molecules at an extremely low concentration (10-12 M). These architectures are extremely stable under air and humidity during production, use, and storage, without altering the oxidation state, for 6 months.

Metal-Organic Frameworks for High Charge-Discharge Rates in Lithium-Sulfur Batteries.

We report a new method to promote the conductivities of metal-organic frameworks (MOFs) by 5 to 7 magnitudes, thus their potential in electrochemical applications can be fully revealed. This method combines the polarity and porosity advantages of MOFs with the conductive feature of conductive polymers, in this case, polypyrrole (ppy), to construct ppy-MOF compartments for the confinement of sulfur in Li-S batteries. The performances of these ppy-S-in-MOF electrodes exceed those of their MOF and ppy counterparts, especially at high charge-discharge rates. For the first time, the critical role of ion diffusion to the high rate performance was elucidated by comparing ppy-MOF compartments with different pore geometries. The ppy-S-in-PCN-224 electrode with cross-linked pores and tunnels stood out, with a high capacity of 670 and 440 mAh g-1 at 10.0 C after 200 and 1000 cycles, respectively, representing a new benchmark for long-cycle performance at high rate in Li-S batteries.

MOFs for Ultrahigh Efficiency Pulsed Laser Micropropulsion.

Conventional propellant materials, such as polymers and single metal elements, have long been investigated for their potential in pulsed laser micropropulsion (LMP) technology. However, achieving superior LMP efficiency through physical mixing of these materials remains a significant challenge. This study presents a paradigm shift by introducing porous crystalline polymers, known as metal-organic frameworks (MOFs), as novel propellants in pulsed LMP. MOFs are composed of metal cations and organic ligands that form ordered structures through coordination, eliminating the problem of local hot zones arising from uneven physical mixing encountered in LMP. In direct comparison to conventional polymers and single element targets, MOFs exhibit substantially higher LMP efficiency. By precisely tailoring the metal atom fraction within MOFs, an extraordinary ultrahigh efficiency of 51.15% is achieved in pulsed LMP, surpassing the performance of similar materials previously reported in the literature. This pioneering application of MOFs not only revolutionizes the field of LMP but also opens up new frontiers for MOF utilization in various energy applications.

Oriented Perovskite Film from Laser Recrystallization in Magnetic Field.

The orientation of crystals on the substrate and the presence of defects are critical factors in electro-optic performance. However, technical approaches to guide the orientational crystallization of electro-optical thin films remain challenging. Here, a novel physical method called magnetic-field-assisted pulse laser annealing (MAPLA) for controlling the orientation of perovskite crystals on substrates is reported. By inducing laser recrystallization of perovskite crystals under a magnetic field and with magnetic nanoparticles, the optical and magnetic fields are found to guide the orientational gathering of perovskite units into nanoclusters, resulting in perovskite crystals with preferred lattice orientation in (110) and (220) perpendicular to the substrate. The perovskite crystals obtained by MAPLA exhibit significantly larger grain size and fewer defects compared to those from pulsed laser annealing (PLA) and traditional thermal annealing, resulting in improved carrier lifetime and mobility. Furthermore, MAPLA demonstrates enhanced device performance, increasing responsivity and detectivity by two times, and photocurrent by nearly three orders compared with PLA. The introduction of Fe2 O3 nanoparticles during MAPLA not only improves crystal size and orientation but also significantly enhances long-term stability by preventing Pb2+ reduction. The MAPLA method has great potential for fabricating many electro-optical thin films with desired device properties and stability.

Epidermal Patch with Biomimetic Multistructural Microfluidic Channels for Timeliness Monitoring of Sweat.

Wearable sweat sensors have been developed rapidly in recent years due to the great potential in health monitoring. Developing a convenient manufacturing process and a novel structure to realize timeliness and continuous monitoring of sweat is crucial for the practical application of sweat sensors. Herein, inspired by the striped grooves and granular structures of bamboo leaves, we realized an epidermal patch with biomimetic multilevel structural microfluidic channels for timeliness monitoring of sweat via 3D printing and femtosecond laser processing. The striped grooves and ridges are alternately arranged at the bottom of the microfluidic channels, and the surface of the ridges has rough granular structures. The striped grooves improve the capillary effect in the microchannels by dividing the microchannels, and the granular structures enhance the slip effect of sweat by increasing surface hydrophobicity. The experimental results show that compared with the conventional microfluidic channels, the water collecting rate of the biomimetic microchannels increased by about 60%, which is consistent with the theoretical analysis. The superior sweat-collecting efficiency in the epidermal patch with the biomimetic multistructure enables sensitive, continuous, and stable monitoring of sweat physiological signals. Besides, this work provides new design and manufacturing approaches for other microfluidic applications.

Nanosecond Laser Confined Bismuth Moiety with Tunable Structures on Graphene for Carbon Dioxide Reduction.

Substrate-supported catalysts with atomically dispersed metal centers are promising for driving the carbon dioxide reduction reaction (CO2RR) to produce value-added chemicals; however, regulating the size of exposed catalysts and optimizing their coordination chemistry remain challenging. In this study, we have devised a simple and versatile high-energy pulsed laser method for the enrichment of a Bi "single atom" (SA) with a controlled first coordination sphere on a time scale of nanoseconds. We identify the mechanistic bifurcation routes over a Bi SA that selectively produce either formate or syngas when bound to C or N atoms, respectively. In particular, C-stabilized Bi (Bi-C) exhibits a maximum formate partial current density of -29.3 mA cm-2 alongside a TOF value of 2.64 s-1 at -1.05 V vs RHE, representing one of the best SA-based candidates for CO2-to-formate conversion. Our results demonstrate that the switchable selectivity arises from the different coupling states and metal-support interactions between the central Bi atom and adjacent atoms, which modify the hybridizations between the Bi center and *OCHO/*COOH intermediates, alter the energy barriers of the rate-determining steps, and ultimately trigger the branched reaction pathways after CO2 adsorption. This work demonstrates a practical and universal ultrafast laser approach to a wide range of metal-substrate materials for tailoring the fine structures and catalytic properties of the supported catalysts and provides atomic-level insights into the mechanisms of the CO2RR on ligand-modified Bi SAs, with potential applications in various fields.

Vanadium Dioxide-Based Terahertz Metamaterial Devices Switchable between Transmission and Absorption.

Terahertz metamaterial plays a significant role in the development of imaging, sensing, and communications. The function of conventional terahertz metamaterials was fixed after fabrication. They can only achieve a single function and do not have adjustable characteristics, which greatly limits the scalability and practical application of metamaterial. Here, we propose a vanadium dioxide-based terahertz metamaterial device, which is switchable between being a transmitter and an absorber. The transmission and absorption characteristics and temperature tunable properties of phase change metamaterials in the terahertz band were investigated. As the temperature of vanadium dioxide is varied between 20 °C and 80 °C, the device can switch between transmission and quad-band resonance absorption at the terahertz frequency range, with a high transmission rate of over 80% and a peak absorbance of 98.3%, respectively. In addition, when the device acts as an absorber, the proposed metamaterial device is tunable, and the modulation amplitude can reach 94.3%; while the device is used as a transmissive device, the modulation amplitude of the transmission peak at 81%. The results indicate that the proposed metamaterial device can promote the applications of terahertz devices, such as switching, modulation, and sensing.

Nanoalloy libraries from laser-induced thermionic emission reduction.

Nanoalloys, especially high-entropy nanoalloys (HENAs) that contain equal stoichiometric metallic elements in each nanoparticle, are widely used in vast applications. Currently, the synthesis of HENAs is challenged by slow reaction kinetics that leads to phase segregation, sophisticated pretreatment of precursors, and inert conditions that preclude scalable fabrication of HENAs. Here, we report direct conversion of metal salts to ultrafine HENAs on carbonaceous support by nanosecond pulsed laser under atmospheric conditions. Because of the unique laser-induced thermionic emission and etch on carbon, the reduced metal elements were gathered to ultrafine HENAs and stabilized by defective carbon support. This scalable, facile, and low-cost method overcomes the immiscible issue and can produce various HENAs uniformly with a size of 1 to 3 nanometers and metal elements up to 11 with productivity up to 7 grams per hour. One of the senary HENAs exhibited excellent catalytic performance in oxygen reduction reaction, manifesting great potential in practical applications.

Bionic Optical Leaf for Photoreduction of CO2 from Noble Metal Atom Mediated Graphene Nanobubble Arrays.

The reduction of CO2 to useful chemicals by solar irradiation has been of great interest in recent years to tackle the greenhouse effect. Compared with inorganic metal oxide particles, carbonaceous materials, such as graphene, are excellent in light absorption; however, they lack in activity and selectivity because of the challenge to manipulate the band gap and optimize the electron-hole separation, which drives the photoreduction process. In this work, inspired by the delicate natural plant leaf structure, we fabricated orderly stacked graphene nanobubble arrays with nitrogen dopant for the coordination of noble metal atoms to mimic the natural photoreduction process in plant leaves. This graphene metamaterial not only mimics the optical structure of leaf cells, which scatter and absorb light efficiently, but also drives the CO2 reduction via nitrogen coordinated metal atoms as the chlorophyll does in plants. Our characterizations show that the band gap of nitrogen-doped graphene could be precisely tailored via substitution with different noble metal atoms on the doped site. The noble atoms coordinated on the doped site of graphene metamaterial not only enlarge the light absorption volume but also maximize the utilization of noble metals. The bionic optical leaf metamaterial coordinated with Au atoms exhibits high CO productivity up to 11.14 mmol gcat-1 h-1 and selectivity to 95%, standing as one of the best catalysts among the carbonaceous and metal-based catalysts reported to date. This catalyst also maintained a high performance at low temperatures, manifesting potential applications of this bionic catalyst at polar regions to reduce greenhouse gases.

3D MOF Nanoarchitecture Membrane via Ultrafast Laser Nanoforging.

Metal-organic framework (MOF) crystals are useful in a vast area of applications because of their unique chemical and physical properties. Manufacturing of an integrated MOF membrane with 3D nanoarchitectures on the surface is especially important for their applications. However, as MOF crystals usually exist as powdery crystals, fabrication of their large area, monolithic, and high-resolution patterns is challenging. Here, it is found that isolated MOF nanocrystals could be directly converted to a monolithic MOF film with designed 3D nanoarchitectures/patterns via an ultrafast laser induced nanoforging without binders. During the nanosecond laser shock, the voids among MOF nanocrystals are eliminated due to the surface amorphization effect, which allows the fusing of the MOF nanocrystals on the grain boundaries, leading to the formation of a dense film while preserving the nature of the pristine MOF. The high strain rate by laser enhances formability of MOFs and overcomes their brittleness to generate arbitrary 3D nanoarchitectures with feature sizes down to 100 nm and high productivity up to 80 cm2 min-1 . These 3D MOF nanoarchitectures also exhibit boosted mechanical strength up to 100% compared with their powdery particles. This method is facile and low-cost and could potentially be used in various fields, such as devices, separation, and biochemical applications.

Magnetically Aligned Ultrafine Cobalt Embedded 3D Porous Carbon Metamaterial by One-Step Ultrafast Laser Direct Writing.

Spatial manipulation of nanoparticles (NPs) in a controlled manner is critical for the fabrication of 3D hybrid materials with unique functions. However, traditional fabrication methods such as electron-beam lithography and stereolithography are usually costly and time-consuming, precluding their production on a large scale. Herein, for the first time the ultrafast laser direct writing is combined with external magnetic field (MF) to massively produce graphene-coated ultrafine cobalt nanoparticles supported on 3D porous carbon using metal-organic framework crystals as precursors (5 × 5 cm2 with 10 s). The MF-confined picosecond laser scribing not only reduces the metal ions rapidly but also aligns the NPs in ultrafine and evenly distributed order (from 7.82 ± 2.37 to 3.80 ± 0.84 nm). ≈400% increment of N-Q species within N compositionis also found as the result of the special MF-induced laser plasma plume. (). The importance of MF is further exmined by electrochemical water-splitting tests. Significant overpotential improvements of 90 and 150 mV for oxygen evolution reaction and hydrogen evolution reaction are observed, respectively, owing to the MF-induced alignment of the NPs and controlled elemental compositions. This work provides a general bottom-up approach for the synthesis of metamaterials with high outputs yet a simple setup.

Multivariate MOFs for laser writing of alloy nanoparticle patterns.

We report three methods for the synthesis of alloy nanoparticles by a laser in air, where three types of MOF precursors are used. Multivariate MOFs, containing different metals in the single crystal backbone, provide continuous tuning of the metal content and excellent uniformity of metal dispersion.

A Single-Atomic Noble Metal Enclosed Defective MOF via Cryogenic UV Photoreduction for CO Oxidation with Ultrahigh Efficiency and Stability.

Noble metal single-atom catalysts (SACs) can provide maximized interaction with the reactants and tunable electronic structure dictated by the coordinated support, thus enabling unprecedented high activity at a reduced noble metal cost. However, the practical utilization of SACs that enabled heterogeneous catalysis has the bottlenecks in high manufacturing cost, low catalytic efficiency, and low atomic utilization of metals due to poor porosity of supporting structures, low affinity between SACs and supports, and high-temperature synthesis involved. A scalable and low-energy consumption synthesis of SACs strongly coordinated with an atomically designed 3D nanostructure is needed to realize higher catalytic efficiency and atomic utilization efficiency. Here, a facile synthesis strategy is developed by applying low-cost cerous MOF (Ce-MOF) with tailored defects across the porous and crystalline structure. SACs (Pt) synthesized by cryogenic photoreduction can be enclosed at the defects in Ce-MOF. Due to the uniform dispersion and the unique electronic hybridization with Ce-MOF, the conjugated catalyst with a low weight content of 0.12 wt % exhibited 100% conversion of CO at a low temperature of 150 °C, consuming only 10% of Pt required by state-of-the-art catalysts operating under the same conditions, standing as the most effective catalyst reported to date.

A laser metallurgy route for the batch preparation of mm-scale 3D silver/graphite heteronanoclusters in air.

We report a batch preparation of mm-scale 3D Ag hetero-nanoclusters which exhibit an excellent surface plasmon resonance ability via facile laser metallurgy. Under laser irradiation, the porous AgI-based coordination network crystals were instantly converted into 3D graphite-encapsulated Ag hetero-nanoclusters with uniform sizes and gaps in several seconds. The obtained hetero-nanoclusters exhibited superior 3D confocal laser energy utilization compared with the other 0D, 1D and 2D SERS substrates, solving the bottleneck caused by laser focusing deviation in the SERS active depth. The mass-produced SERS devices were ultra-sensitive for the detection of life and industrial organic pollutants in terms of low detection and enriched capacity.

Three-Dimensional Hierarchical Constructs of MOF-on-Reduced Graphene Oxide for Lithium-Sulfur Batteries.

A three-dimensional (3D) hierarchical MOF-on-reduced graphene oxide (MOF-on-rGO) compartment was successfully synthesized through an in situ reduced and combined process. The unique properties of the MOF-on-rGO compartment combining the polarity and porous features of MOFs with the high conductivity of rGO make it an ideal candidate as a sulfur host in lithium-sulfur (Li-S) batteries. A high initial discharge capacity of 1250 mAh g-1 at a current density of 0.1 C (1.0 C=1675 mAh g-1 ) was reached using the MOF-on-rGO based electrode. At the rate of 1.0 C, a high specific capacity of 601 mAh g-1 was still maintained after 400 discharge-charge cycles, which could be ascribed to the synergistic effect between MOFs and rGO. Both the hierarchical structures of rGO and the polar pore environment of MOF retard the diffusion and migration of soluble polysulfide, contributing to a stable cycling performance. Moreover, the spongy-layered rGO can buffer the volume expansion and contraction changes, thus supplying stable structures for Li-S batteries.

Facile Synthesis of Uniform Metal Carbide Nanoparticles from Metal-Organic Frameworks by Laser Metallurgy.

We report the fast and efficient conversion of metal-organic frameworks (MOFs) to phase pure transition-metal carbide (TMC) nanoparticles with uniform size using laser as the energy source, consuming only 6 W power. Nanoparticles of HfC, ZrC, TiC, V8C7, α-MoC, Cr3C2, and FeCx with homogeneous sizes (varied between 6 and 20 nm) were successfully produced, among which HfC and ZrC nanoparticles were obtained, for the first time, with sizes less than 10 nm and in the pure phase. This method was operated directly in air, in stark contrast to traditional furnace heating and laser spray methods, where a protective atmosphere is required. The use of MOFs allowed us to precisely tune the composition of TMC nanoparticles by dialing in the right type and desirable amounts of organic linkers. FeCx nanoparticles doped with various percentages of nitrogen atoms were synthesized for the Fischer-Tropsch reaction without any pretreatment or activation. Extremely high iron time of yield (FTY) values were observed, 415 and 550 µmol gFe-1 s-1 (with addition of K), in a 40 h test without any decay in performance. A high olefin to paraffin ratio was achieved for C2 to C11 products, where the ratio for C3 was higher than 10.