Ultrafast Method Research Articles

Direct ultrafast carrier imaging in a perovskite microlaser with optical coherence microscopy

Nanophotonics is an actively developing field of optics that finds application in various areas, from biosensing to quantum computing. The study of ultrafast modulation of the refractive index Δn is an important task in nanophotonics, since it reveals the features of light–matter interaction inside devices. With the development of active photonic devices such as emitters and modulators, there is a growing need for Δn imaging techniques with both high spatial and high temporal resolutions. Here, we report on an all-optical ultrafast Δn imaging method based on phase-sensitive optical coherence microscopy with a resolution of 1 ps in time and 0.5 µm in space and a sensitivity to Δn down to 10−3RIU. The advantages of the method are demonstrated on emerging nanophotonic devices—perovskite microlasers, in which the ultrafast spatiotemporal dynamics of the refractive index during lasing is quantitatively visualized, illustrating the features of relaxation and diffusion of carriers in perovskites. The developed method allows us to estimate the ultrafast carrier diffusion and relaxation constants simultaneously and to show that the CsPbBr3 perovskite carrier diffusion coefficient is low compared to other semiconductors even during lasing at high carrier densities, which leads to high localization of the generated carrier cloud, and, consequently, to high fluorescence and lasing efficiency. The resulting technique is a versatile method for studying ultrafast carrier transport via Δn imaging, paving an avenue for the applications of optical coherence tomography and microscopy in the research of nanophotonic devices and materials.

Direct and rapid regeneration of spent LiFePO4 cathodes via a high-temperature shock strategy

The requirement for lithium-ion batteries is rising sharply in recent years due to rapid development of electric vehicles and new energy storage. However, this increase in number of lithium-ion batteries also leads to the production of a significant number of spent batteries. Considering the potential environment pollution and waste of resources, it is absolutely imperative to recover these spent lithium-ion batteries. Conventional direct regeneration method always undergoes a slow heating rate and prolonged calcination process, which consume high energy and time. Herein, we presented an efficient, low-cost and ultrafast regeneration strategy for rapid regeneration of the spent LiFePO4 in only 20 s. Compared of traditional method, this ultrafast method consumes less energy and takes shorter time. As a result, the lithium is completely replenished and the structure of LiFePO4 is well repaired, and it demonstrates excellent initial capacity of 152 mAh g−1 at 0.1C. Furthermore, RLFP-800 exhibits a good rate performance and long-cycling stability (400 cycles at 2C without capacity recession). It is expected that this rapid regeneration strategy can be developed for practical spent LiFePO4 regeneration at low cost.

Development of rapid on-site detection of Salmonella Enteritidis, S. Typhimurium, and S. Thompson in food samples using an ultrafast PCR system

The conventional Salmonella serotyping methods are labor intensive and time-consuming; therefore, rapid identification method is needed to detect outbreaks early and prevent their spread. In this study, we developed for the first time a detection method for the rapid and accurate on-site serotyping of Salmonella enterica subsp. enterica serovar Enteritidis, Thompson, and Typhimurium, all of which have epidemiological importance worldwide. This method, which is based on specific marker genes, was constructed with portable equipment and a simple DNA extraction step. For the specific detection of the three serovars, genetic markers obtained via a bioinformatics analysis were selected and showed high specificity for 97 strains. The ultrafast polymerase chain reaction (PCR) showed high linearity (≥0.997) in both pure culture and a spiked food sample, with a detection specificity of 102 colony forming unit (CFU)/ml; these results are consistent with real-time PCR. Moreover, ultrafast PCR was further improved for developing direct ultrafast PCR method for field detection, the entire procedure of which could be completed within 25 min. The test results of an artificially contaminated food sample showed that the three serovars could be detected using the direct ultrafast PCR with a very short (3 h) enrichment step when inoculated at 1 CFU/g. This method exhibited various advantages, such as its ultrafast and labor-saving characteristics, which can be applied to the diagnosis of Salmonella serovar in the field.

An ultra-fast method for designing holographic phase shifting surfaces

Holographic phase-shifting surfaces (PSSs) have been proven to offer a cost-effective solution for enabling passive arrays to mechanically steer their beams toward desired directions. However, even though the principle of operation of PSSs is straightforward, designing a PSS is very challenging, because it involves an extremely high computational time, which in turn limits their usage and development. Notably, traditional design approaches of PSSs, with N number of layers that have M different variations of conductive patches, need M^N full-wave simulations to be properly characterized. To address these challenges that are associated with the design of PSSs and reduce the needed computational effort, we present here a semi-numerical approach that enables the efficient design of holographic PSSs. Specifically, by representing an N-layer PSS unit-cell as N cascaded networks, where each network represents one layer of the PSS that has M different designs of sub-wavelength resonators, we only need to conduct N times M full-wave simulations to collect all the required data needed to analyze the performance of the PSS. In turn, by utilizing the multiplication property of ABCD parameters we can evaluate very efficiently all the M^N different combinations that characterize our PSS. To validate the accuracy of our design methodology, a 1-D beam steerable antenna system is designed that is comprised of a circularly polarized holographic metasurface antenna (HMA) and a hybrid PSS, both operating at 30 GHz. Comparisons between our semi-numerical results, full-wave simulations, and measurements demonstrate an angular error of less than 0.7^{circ }.

Ultrafast pulse duration measurement method of near-infrared pulses for a broad range of wavelengths using two-photon absorption in a liquid and fluorescent dye solution.

A novel characterization method to measure the pulse duration of ultrafast near-IR pulses is introduced, which uses simple tabletop optics, is relatively inexpensive, and is expected to work in a broad wavelength range. Our diagnostic tool quantitatively characterizes the laser pulse duration of any near-IR wavelength assuming a Gaussian pulse shape with a linear chirp. We negatively prechirp near-IR pulses with a home-built broadband pulse compressor (BPC) and send this prechirped beam through a cell filled with a low-molar solution of a fluorescent dye in a liquid. After two-photon absorption, this dye fluoresces in the visible, and we record this visible signal as a function of the propagation distance in the liquid cell. We calibrate the group velocity dispersion (GVD) of our home-built BPC device against the known GVD of the compressor of our 800nm laser and confirm this value using geometric considerations. Now knowing the GVD of BPC and the recorded visible signal for various amounts of negative chirp, let us extract the smallest pulse duration of the near-IR pulse from this visible signal. As a useful corollary, our analysis also enables the direct measurement of the GVD for liquids and the indirect measurement of the absorption coefficient for liquids in the near-IR range, in contrast to indirect GVD measurements that rely on methods such as the double derivative of the refractive index.

A novel ultrafast laser ablation fracture polishing method to simultaneously smoothing and improving the surface quality of Al2O3 ceramics with high roughness

Al2O3 ceramics are widely used in industry due to their excellent mechanical and physical properties. However, microcracks, voids and high surface roughness (Sa) on the surface of Al2O3 ceramic parts produced in conventional industrial or additive manufacturing have been one of the technical bottlenecks limiting their high-performance applications. In this paper, a novel method of ultrafast laser ablation fracture polishing (ULAFP) of Al2O3 ceramic parts is proposed for improving the surface quality and enhancing the mechanical properties of the polished surfaces. The ULAFP method is developed with an ultrafast laser, which can be set up as a picosecond (PS) or a femtosecond (FS) laser. The PS laser is used to form a remelting layer on the surface to eliminate surface void defects. Combining laser ablation and laser thermal stress-induced crack extension effects, the FS laser is used to rapidly remove the remelted layer and obtain a surface free of crack defects and finally implement FS laser layer-wise ablation to achieve smoother surface finish. The FS laser energy density is controlled at a critical state close to the ablation threshold of the material to avoid surface defects. This ULAFP can reduce the surface roughness (Sa5.254 μm) polishing of Al2O3 ceramics to 0.80 μm, while controlling the total ablation depth of the polishing process to below 100 μm maintaining the dimensional accuracy of the part and dramatically improving the mechanical properties of the polished surface. Compared with the original surface, the hardness and elastic modulus of the polished surface improved by 104.6% and 63.9%, respectively.

Ultrafast room-temperature activation of nickel foams as highly efficient electrocatalysts

Nickel foams (NF) are widely used electrode substrates that are associated with a wide range of industrial chains and large economic benefits. However, the pristine Ni foams usually possess poor electrochemical activities with dense passivation layers. Herein, an ultra-fast method for activating raw Ni foam was developed by soaking the Ni foam in a formulation solution of thiourea and I2/KI at room temperature for just a few minutes. In the solution, I3− (I2 + I−) acts as an oxidizer to accelerate the formation of Ni2+, while the hydrolysis of thiourea provides a weakly acidic environment and sulfur ions for formation of superficial layer NiS with I doping. The activated Ni foam has a fluffy nanosheet structure and the activity, characterized by the integrated Ni2+/Ni3+ peak area is enhanced by more than 100 times. The activated electrode exhibits high performance towards urea oxidation reaction (UOR) in alkaline electrolytes, delivering a current density of 100 mA cm−2 at only 1.44 V (vs. RHE, reversible hydrogen electrode). The in situ Raman spectroscopy identifies NiOOH as the catalytically active species for urea oxidation and in situ differential electrochemical mass spectrometry (DEMS) isotope tracking experiment reveals an intramolecular N-N bond coupling mechanism during the UOR. The developed activation method is easy to scale up for preparing large-area electrode and the catalytic activity is extended to oxidation of other organic molecules. This work presents a novel ultrafast one-step surface engineering strategy for activating Ni foams into high-performance electrocatalysts.

An Ultra-Fast and Green LC-MS Method for Quantitative Analysis of Aesculin and Aesculetin in Cortex Fraxini

This study aims to develop a fast and eco-friendly liquid chromatography–mass spectrometry (LC-MS) method for the determination of aesculin and aesculetin in Cortex Fraxini. Ultrapure water was used as the solvent during the microwave-assisted extraction process to prepare the Cortex Fraxini sample. This extraction method reduces the cost of the harmful solvent (only ultrapure water was used) and microwave extraction time (1 min). The LC separation was conducted using an Agilent InfinityLab Poroshell 120 EC-C18 column (2.1 mm × 30 mm, 2.7 µm) with a mobile phase consisting of 0.1% formic acid and acetonitrile (90:10, v/v) at a flow rate of 0.6 mL/min. Isocratic elution was employed, and the analytes were detected by MS. Through careful optimization and selection of LC-MS conditions, the analysis time was reduced to 1 min, demonstrating the method’s efficiency. The developed method was validated and exhibited excellent specificity, linearity, limit, precision, accuracy, and stability in quantifying aesculin and aesculetin in the Cortex Fraxini samples. The analysis result revealed the presence of aesculin (ranging from 3.55 to 18.8 mg/g) and aesculetin (ranging from 1.01 to 16.2 mg/g) in all ten batches of Cortex Fraxini samples. Compared to the reported LC methods, this approach substantially reduces the total analysis time and requires a minuscule volume of organic solvents. An “Analytical Eco-Scale” assessment was used to evaluate the different assay methods of Cortex Fraxini. The current LC-MS method scored an impressive 90; it was better than the other four reports’ LC methods. Thus, the developed LC-MS method is rapid and green, which is helpful for the quality evaluation of Cortex Fraxini.

Surface-wave-sustained plasma synthesis of graphene@Fe–Si nanoparticles for lithium-ion battery anodes

Silicon encapsulated in conductive layers has proven to be an excellent method for retaining the high capacity of silicon in lithium-ion batteries (LIBs) throughout cycling. This study presents an ultra-fast, single-step, and scalable method for synthesizing graphene@Fe–Si nanoparticles via an atmospheric pressure surface-wave-sustained plasma. The verification of the synthesized nanoparticles, encompassing graphene cladding and silicon nanoparticles encapsulated in iron, was conducted through energy-dispersive x-ray spectroscopy mapping, line scanning in the transmission electron microscopy mode, and high-resolution transmission electron microscopy. Additionally, Raman spectroscopy corroborated the identity of the cladding as graphene. This study provides a viable strategy for the industrial production of anode materials for high-performance LIBs.

Investigation of crack propagation behavior on shales with different inclination based on ultra-fast time resolution method

The layer structures of shale greatly influence its crack propagation behavior. Nevertheless, the correlation between crack extension rates and mechanical parameters has not been well studied, especially, the relationship between the energy release rate and crack propagation rates. Consequently, there are unresolved issues regarding the effects of layer structure on the propagation of cracks in shale. In this paper, a series of three-point compressive loading tests were conducted on seven groups of shale semi-circular bend (SCB) samples with an inclination angle of 0°-90°. The entire fracture process was captured using the ultrafast time-resolution method with a resolution capability of up to 15 picoseconds. In addition, fracture surface information was obtained by a high-precision laser three-dimensional scanning system, and this information was utilized to categorize crack propagation behaviors, such as propagation along weak planes, intermittent penetration, and deflection penetration. Furthermore, a quantitative relationship was established between the energy-release rate and crack propagation rate, based on the first law of thermodynamics and the maximum energy release rate (MERR) criteria proposed by Griffith. The experimental results showed that there is a linear relationship between the energy-release rate and the propagation rate, which meets well with the established relationship. The experimental results indicated that symmetric loading does not result in significant angle localization during crack initiation. This suggests that crack propagation behavior in shale is a reflection of the interplay between energy-release rates and fracture resistance. Finally, this study evaluated the influence of the bedding angle on dissipated energy, and absorbed energy.

Improving Photovoltaic MPPT Performance through PSO Dynamic Swarm Size Reduction

Efficient energy extraction in photovoltaic (PV) systems relies on the effective implementation of Maximum Power Point Tracking (MPPT) techniques. Conventional MPPT techniques often suffer from slow convergence speeds and suboptimal tracking performance, particularly under dynamic variations of environmental conditions. Smart optimization algorithms (SOA) using metaheuristic optimization algorithms can avoid these limitations inherent in conventional MPPT methods. The problem of slow convergence of the SOA is avoided in this paper using a novel strategy called Swarm Size Reduction (SSR) utilized with a Particle Swarm Optimization (PSO) algorithm, specifically designed to achieve short convergence time (CT) while maintaining exceptional tracking accuracy. The novelty of the proposed MPPT method introduced in this paper is the dynamic reduction of the swarm size of the PSO for improved performance of the MPPT of the PV systems. This adaptive reduction approach allows the algorithm to efficiently explore the solution space of PV systems and rapidly exploit it to identify the global maximum power point (GMPP) even under fast fluctuations of uneven solar irradiance and temperature. This pioneering ultra-fast MPPT method represents a significant advancement in PV system efficiency and promotes the wider adoption of solar energy as a reliable and sustainable power source. The results obtained from this proposed strategy are compared with several optimization algorithms to validate its superiority. This study aimed to use SSR with different swarm sizes and then find the optimum swarm size for the MPPT system to find the lowest CT. The output accentuates the exceptional performance of this innovative method, achieving a time reduction of as much as 75% when compared with the conventional PSO technique, with the optimal swarm size determined to be six.

Selective adsorption of acetylene over carbon dioxide on glycine functionalized HKUST-1 with enhanced moisture stability

HKUST-1 is one of the most widely studied Metal-Organic Frameworks and is known for strong acetylene adsorption performance. However, it suffers from poor stability and lower working capacity after moisture exposure. To address this issue, we comparatively apply pristine HKUST-1 and glycine functionalized HKUST-1. They were prepared by a well-known low energy-consuming hydroxy double salt method. The ultrafast synthetic method was applied to obtain HKUST-1-ultrafast (HKUST-1-UF) and one glycine per three Cu sites was added HKUST-1 (HKUST-1-UF-GLY0.3). An adsorption study of C2H2 on the HKUST-1-UF and HKUST-1-UF-GLY0.3 shows that the introduction of glycine as the secondary binding unit increased the C2H2 uptake performance compared to that of bare HKUST-1. An evaluation of stability against moisture exhibits that the structural stability of HKUST-1-UF-GLY0.3 is enhanced compared to HKUST-1-UF. Further, in a breakthrough experiment using an equimolar C2H2/CO2 gas mixture, HKUST-1-UF-GLY0.3 exhibits a longer breakthrough time compared to HKUST-1-UF after thermal pre-treatment, or even pre-humidifying (RH 60% and RH 80%) overnight. The adsorbents can be repeatedly used as a C2H2 adsorbent over CO2.

Novel Ultra-Fast Liquid Chromatography Method for Simultaneous Quantification of Metformin Hydrochloride and Remogliflozin Etabonate

An advanced formulation having remogliflozin etabonate (REM) and metformin hydrochloride (MET) for the treatment of diabetes was recently approved. However, there hasn't been any information reported on a UFLC technique for simultaneously quantifying both active substances. Therefore, aim of the study was the development of an ultra-fast isocratic liquid chromatography method for quantification of MET and REM in API and dosage form. The reversed phase-UFLC method was developed with a very short run time of only 3 min with no interference due to blank. The compounds were separated using Shimadzu Sim-pack XR ODS (75 mm × 3 mm, 2.2 μ) column with mobile phase consisting of buffer (0.1% phosphoric acid):acetonitrile (30:70). The developed method was validated as per ICH-Q2(R1). The linearity was established in the range of 0.01-125 ppm and 0.01-25 ppm for MET and REM, respectively. The average assay was found 99.4% for MET and 99.1% for REM. The accuracy was observed 98.29-99.49% for MET and 98.39-99.73% for REM. The proposed method is very fast and simple however precise and accurate. This method is very useful for regular quality control laboratory to quantify MET and REM in API and dosages forms.

Photoinduced Ultrafast Phase Transition in Bilayer CrI3.

In two-dimensional magnets, the ultrafast photoexcited method represents a low-power and high-speed method of switching magnetic states. Bilayer CrI3 (BLC) is an ideal platform for studying ultrafast photoinduced magnetic phase transitions due to its stacking-dependent magnetic properties. Here, by using time-dependent density functional theory, we explore the photoexcitation phase transition in BLC from the R- to M-stacked phase. This process is found to be induced by electron-phonon interactions. The activated Ag and Bg phonon modes in the xy direction drive the horizontal relative displacements between the layers. The activated Ag mode in the z direction leads to a transition potential reduction. Furthermore, this phase transition can invert the sign of the interlayer spin interaction, indicating a photoinduced transition from ferromagnet to antiferromagnet. This investigation has profound implications for magnetic phase engineering strategies.

Fast joule heating synthesis of NiCoFeCrMo high-entropy alloy embedded in graphene for water oxidation

High-entropy alloys (HEAs) are considered as considerable candidate for electrocatalytic water splitting. The main holdback locates in fabricating well-defined HEAs with moderate electronic structure and uncovering the structural evolution during the reaction process. Herein, we successfully synthesized NiCoFeCrMo HEA-nps by an ultrafast joule heating method for highly efficient oxygen evolution reaction (OER). The optimal graphene incorporated NiCoFeCrMo HEA nanoparticles (HEA-nps) exhibits finely distributed nanoparticles with average size of 17.49 nm and uniformly distribution of all the five elements, which displays the outstanding OER performance with a low onset potential and only requires the 260 mV (vs RHE) to achieve the current density of 10 mA cm−2. X-ray absorption fine structure (XAFS) demonstrates that the high valence Cr and Mo can directly regulate the local structure of HEA-nps, which significantly promoted the intrinsic activity of high active species. This work not only provides a design strategy related to the high valence elements injection for HEAs, but also uncovers the structural evolution of HEAs during OER process.

In Vivo Metabolic Imaging of [1-13 C]Pyruvate-d3 Hyperpolarized By Reversible Exchange With Parahydrogen.

Metabolic magnetic resonance imaging (MRI) using hyperpolarized (HP) pyruvate is becoming a non-invasive technique for diagnosing, staging, and monitoring response to treatment in cancer and other diseases. The clinically established method for producing HP pyruvate, dissolution dynamic nuclear polarization, however, is rather complex and slow. Signal Amplification By Reversible Exchange (SABRE) is an ultra-fast and low-cost method based on fast chemical exchange. Here, for the first time, we demonstrate not only in vivo utility, but also metabolic MRI with SABRE. We present a novel routine to produce aqueous HP [1-13 C]pyruvate-d3 for injection in 6 minutes. The injected solution was sterile, non-toxic, pH neutral and contained ≈30 mM [1-13 C]pyruvate-d3 polarized to ≈11 % (residual 250 mM methanol and 20 μM catalyst). It was obtained by rapid solvent evaporation and metal filtering, which we detail in this manuscript. This achievement makes HP pyruvate MRI available to a wide biomedical community for fast metabolic imaging of living organisms.

NiCo-MOF Nanospheres Created by the Ultra-Fast Microwave Method for Use in High-Performance Supercapacitors.

Metal-organic frameworks-through the use of creative synthetic designs-could produce MOF materials with excellent porosity, stability, particle microstructures, and conductivity, and their inherent characteristics-including their porosity and controllable structure-may result in an immense number of prospects for energy storage. In this paper, a nanosphere-like NiCo-MOF was effectively manufactured via an ultra-fast microwave technique. Additionally, the ideal synthesis conditions of the NiCo-MOF were investigated by adjusting the microwave output power and microwave reaction time. Under the reaction conditions of a 600 W microwave and a 210 s microwave reaction time, the NiCo-MOF exhibited an excellent capacitance of 1348 F/g at a current density of 1 A/g and an 86.1% capacity retention rate at 10 A/g. In addition, self-assembled NiCo-MOF/AC asymmetric capacitors showed a splendid energy density of 46.6 Wh/kg and a power density of 8000 W/kg.

Ultrafast Antisolvent Growth of Single-Crystal CsPbBr3 Microcavity for Whispering-Gallery-Mode Lasing.

In recent years, all-inorganic cesium lead bromide (CsPbBr3) perovskites have garnered considerable attention for their prospective applications in green photonics and optoelectronic devices. However, the development of efficient and economical methods to obtain high-quality micron-sized single-crystalline CsPbBr3 microplatelets (MPs) has become a challenge. Here, we report the synthesis of CsPbBr3 MPs on Si/SiO2 substrate by optimizing the ultrafast antisolvent method (FAS). This technique is able to produce well-dispersed, uniformly sized, and morphologically regular tetragonal phase single crystals, which can give strong green emission at room temperature, with excellent stability and excitonic character. Moreover, the crystals demonstrated lasing with a whispering gallery mode with a low threshold. These results suggest that the single-crystalline CsPbBr3 MPs synthesized by this method are of high optical quality, holding vast potential for future applications in photonic devices.

Potential of Negative-Ion-Mode Proteomics: An MS1-Only Approach.

Current proteomics approaches rely almost exclusively on using the positive ionization mode, resulting in inefficient ionization of many acidic peptides. This study investigates protein identification efficiency in the negative ionization mode using the DirectMS1 method. DirectMS1 is an ultrafast data acquisition method based on accurate peptide mass measurements and predicted retention times. Our method achieves the highest rate of protein identification in the negative ion mode to date, identifying over 1000 proteins in a human cell line at a 1% false discovery rate. This is accomplished using a single-shot 10 min separation gradient, comparable to lengthy MS/MS-based analyses. Optimizing separation and experimental conditions was achieved by utilizing mobile buffers containing 2.5 mM imidazole and 3% isopropanol. The study emphasized the complementary nature of data obtained in positive and negative ion modes. Combining the results from all replicates in both polarities increased the number of identified proteins to 1774. Additionally, we analyzed the method's efficiency using different proteases for protein digestion. Among the four studied proteases (LysC, GluC, AspN, and trypsin), trypsin and LysC demonstrated the highest protein identification yield. This suggests that digestion procedures utilized in positive-mode proteomics can be effectively applied in the negative ion mode. Data are deposited to ProteomeXchange: PXD040583.

Constructing bimetallic heterostructure as anodes for sodium storage with superior stability and high capacity

Heterostructure materials hold promise as future-generation anodes for sodium-based energy storage. However, the complexity and time-intensity of heterojunction fabrication processes limit their large-scale application. This study utilizes an ultrafast, one-step microwave process to successfully design and fabricate bimetallic selenides heterojunction nanoparticles, anchored on a three-dimensional porous carbon substrate (NiSe2–SnSe2/C). The in-situ formation of NiSe2–SnSe2 heterostructure optimizes sodium ion adsorption and transfer, which facilitates reaction kinetics and subsequently improves both the rate capability and cycle life. The NiSe2–SnSe2/C electrodes demonstrate a high-rate capability (719.8 mAh g−1 at 0.1 A g−1, and 667.9 mAh g−1 after a 50-fold increase in current density to 5 A g−1), maintaining high stability even after 10,000 cycles at 5 A g−1. The impact of the NiSe2–SnSe2 heterostructure on reaction kinetics was examined using density functional theory. The NiSe2–SnSe2/C anode, when coupled with the Na3V2(PO4)3 cathode in a full battery, demonstrated an impressive energy density of 155 Wh kg−1. This work exemplifies an ultrafast synthetic method for constructing heterostructure materials having great rate, high capacity and strong stability for sodium storage, making them promising candidates for large-scale energy storage applications.