A few days ago, the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, the Institute of Chemistry of the Chinese Academy of Sciences and Northeastern University each added a Science.
Dalian Institute of Chemical Physics, Chinese Academy of Sciences
Pre-alignment of non-polar reaction molecules results in large stereokinetic effects due to their weak steering interaction on the way to the reaction barrier. However, experimental limitations in the efficient preparation of permutational molecules hinder the study of spatial effects in hydrogen-containing bimolecular reactions.
On January 12, 2023, Yang Xueming's research group, Zhang Donghui's group, Zhang Zhaojun's research group and Xiao Chunlei's research group of Dalian Institute of Chemical Physics, Chinese Academy of Sciences cooperated to publish a research paper entitled "Stereodynamical control of the H + HD → H2 + D reaction through HD reagent alignment" online in the journal Science, which reported a high-resolution cross-beam study H+ HD(v = 1, j = 2)→ reaction of H2(v ', j ') + D at collision energies of 0.50, 1.20 and 2.07 electron volts, in which vibrationally excited hydrogen deuteride (HD) molecules are prepared in two collision configurations with bonds preferentially parallel arranged and perpendicular to the relative velocities of the collision partners. Significant stereodynamic effects are observed on differential cross-sections. Quantum dynamics calculations show that strong structural interference in the vertical configuration plays an important role in the observed stereodynamic effects.
The fundamental goal of chemical reaction kinetics is to provide a detailed and quantitative understanding of chemical reaction processes and to provide new tools to control the outcome of chemical events beyond traditional methods such as adding a suitable catalyst and changing the temperature or pressure of the reaction mixture. An effective way to control a chemical reaction is to deposit some energy in the reaction coordinates of the reactant to make the desired molecular bond more easily cleaved. Many kinetic studies realize this idea through vibrational excitation of reagent molecules, leading to the discovery and in-depth understanding of bond-selectivity or mode-specific chemistry. In addition to vibration control, the mutual orientation of the collision partners also has a great influence on the results of the chemical reaction. Therefore, by controlling the orientation of colliding molecules, it is possible to promote or hinder the product to reach a specific end state or scattering angle.
For many years, spatial pose control has been used primarily for inelastic and reactive systems of polar molecules. In scattering experiments, many methods have been developed to align or orient molecules, including light pumping, hexapolar selection, and strong orientation. Studies have proposed an elegant theoretical framework to describe spatial effects. Recently, the end-to-side collision of Ar and directional NO has been studied, and it has been demonstrated that the collision results can be controlled by changing the direction of the key axis, in addition, scientists have conducted a series of experiments to explore the effect of steric obstruction on differential cross sections (DCSs) in Cl+CHD3 reactions. The researchers observed a strong steric hindrance effect, suggesting that CHD3's redirection effect to the reaction barrier in this system is not strong due to its nonpolar nature.
Obviously, arranging non-polar reaction molecules can have large spatial effects because they have weak steering interactions on the way to the reaction barrier. H2 is undoubtedly the best candidate for this purpose, as it is both the most widely studied molecule in kinetic experiments and theoretically the easiest to handle. However, until recently, it was difficult to prepare sufficient concentrations of specific quantum state H2 for scattering experiments. The development of Stark-induced adiabatic Raman passage (SARP) technology has not only opened the door to studying the collision dynamics of vibrationally excited H2 molecules by excitation of large concentrations of H2 and its isotopes in specific quantum states, but also made it possible for these molecules to be aligned in spatial dynamics experiments.
It was observed that the angular distribution has a strong stereodynamic preference in inelastic scattering between the arranged HD and D2 molecules at temperatures as low as 1 K, suggesting that weak steering interactions can inhibit reorientation effects and expose more pronounced spatial effects. They also created quantum mechanical double slits by preparing D2 molecules excited by rotational vibrations with coherent coupling shaft directions in a biaxial state, and demonstrated that they act as two slits of a double-slit interferometer that behaves as a strong modulation of the measured angular distribution when inelastically scattered with He atoms. It is highly desirable whether this significant spatial effect can be observed in the simplest chemical reactions involving H2 molecules and understood at the most basic level.
In this study, a fully quantum-resolved cross-molecular beam study of H+HD→H2+D reactions was performed, and the reaction of HD molecules in two preferential states was prepared using a stimulated Raman pumping (SRP) protocol.
The study found that the DCS of the reaction changed dramatically with the orientation of the HD bonding shaft, suggesting that the DCS of the chemical reaction can be effectively controlled.
Figure 1. Schematic diagram of two collision geometries prepared by SRP | Source: Science
Further studies show that the angular distribution of the m = 0 and m = ± 2 channels in HD (v = 1, j = 2) is different, one is backward-dominant and the other is laterally dominant. For the vertical configuration, the angular distribution across the scattering plane is determined by Equation 3, and the interference term is between the m=0 and m=±2 channels. Especially when the collision energies are 1.20 and 2.07 eV, strong constructive interference occurs on both sides, which significantly increases the peak height of both sides. The results show that the goniometric distribution of the vertical configuration is significantly different from that of the parallel configuration, showing a strong stereodynamic effect.
Figure 2. Experimental and theoretical comparison of product state-resolved DCSs | Source: Science
In general, the preparation of hydrogen-deuterium (HD) molecules by polarimetric stimulated Raman pumping was obtained, and high-quality stereokinetic data of H+HD→H2+D reactions were obtained by using polarized stimulated Raman pumping, and the HD bond shaft was parallel or perpendicular to the H atomic velocity. These measurements show that HD orientation has a significant impact on this most fundamental chemical reaction, and is further supported by good alignment with quantum mechanical calculations. The current work is an important milestone in the field of reaction kinetics.
Institute of Chemistry, Chinese Academy of Sciences
Reproducing ion channel-based neural function using artificial fluid systems has been an ideal goal for neuromorphic computing and biomedical applications.
On January 12, 2023, the Mao Lanqun research group of the Institute of Chemistry, Chinese Academy of Sciences, and Yu Ping's research group cooperated to publish a research paper entitled "Neuromorphic functions with a polyelectrolyte-confined fluidic memristor" online in the journal Science, which studied polyelectrolyte-confined Fluidic memristor, PFM) successfully achieves neuromorphological functions in which restricted polyelectrolyte-ion interactions lead to delayed ion transport, leading to ionic memory effects. The ultra-low power PFM simulates a variety of electrical pulse modes. The fluid properties of PFM make it possible to simulate chemically regulated electrical impulses. What's more, chemical-electrical signal transduction is achieved by a single PFM.
In conclusion, the PFM proposed in this study is universal due to its similar structure to ion channels, and PFM is easy to interface with biological systems, paving the way for the construction of neuromorphic devices with advanced functions by introducing rich chemical designs.
The development of artificial systems with brain-like functions (i.e., neuromorphic devices) is expanding rapidly because of their promising applications in neuromorphic computing, biologically stimulated sensorimotor realization, brain-computer interfaces, and neuroprosthetics. So far, neuromorphic functions with different modes have been implemented and incorporated into applications in various ways, mainly using historically dependent solid-state resistive switching devices. Includes two-terminal memristors and three-terminal transistors. However, most of the neuromorphic functions achieved to date have been based on simulations of electrical impulse patterns using solid-state devices. Simulating biological synapses—especially chemical synapses in solution-based environments—remains very challenging using these solid-state devices. In this regard, fluid-based memristors are well suited for neuromorphic functions in aqueous environments because of its excellent compatibility with biological systems and gives neuromorphic devices more functions by introducing different chemicals.
Previous attempts have shown that ion-based micro- or nanofluidic devices with advanced capabilities [e.g., ion diodes, ion transistors, or ion switches] can be realized by confining the electrolyte to micro- or nanochannels. In addition, by introducing an ionic liquid-electrolyte interface, the nanochannels acquire long-term plasticity. Despite these efforts, achieving neuromorphic function in aqueous media remains a long-term challenge, mainly because strong shielding effects in the aqueous environment greatly impede ion-ion interactions, thereby limiting the formation of memories in fluid-based systems. In 2021, a landmark theoretical model predicted that ionic memory functions could be accomplished with two-dimensional limit channels, which had been experimentally implemented by the same group.
This study reports a polyelectrolyte-constrained fluid memristor (PFM) that can successfully perform a variety of neuromorphological functions, simulating not only electrical impulse patterns but also chemical-electrical signal transduction. Inspired by the design and manufacture of polyimidazolium brushes (PimB), a confined fluidic channel, biochannels that act as natural memristors by controlling ion flux through spatial confinement and molecular recognition.
Figure 1. The conductivity variation of PFM is | Source: Science
Polyimidazole was chosen because of its high charge density, rich chemistry, and ability to recognize different anions. Typically, PimB is grown on the inner walls of glass micro- or nanoparticles through surface-initiated atom transfer radical polymerization. In this way, the fluid is confined by PimB, and under the stimulation of electric fields or chemicals, the establishment of anion concentration equilibrium and charge balance inside and outside PimB lags, resulting in historically dependent ion memory.
Figure 2. Chemical-electrical signal transduction of PFM | Source: Science
Overall, this study proposes nanofluidized ion memristors based on confined polyelectrolyte-ion interactions. Studies have focused on different aspects of neuromorphic engineering, but all have shown precise control of ion transport in water through nanoscale channels. These studies show promising directions for creating neuromorphic functions using highly efficient fluid memristors that can mimic the fundamentals of biological systems.
Northeastern University
From transportation to lightweight design to safe infrastructure, load-bearing materials for mechanical strength and ductility are needed in all sectors. However, a big challenge is to unify the two functions in one material.
On January 12, 2023, the research group of Yuan Guo, Li Linlin, and Dierk Rolf Raabe of the Max Planck Institute of the German Max Planck Society Iron and Steel Research Institute collaborated to publish a research paper entitled "Ductile 2-GPa steels with hierarchical substructure" online in the journal Science, which showed that ordinary medium manganese steel can be processed into tensile strength > with a uniform elongation of > 20%. 2.2 Gipascal. This requires a combination of multiple lateral forging, cryogenic treatment and tempering steps. A layered microstructure consisting of layered and double-topological martensite and finely dispersed retained austenite simultaneously activates multiple microscopic mechanisms to enhance and ductilize materials. Dislocation, slip and progressive deformation in well-organized martensite stimulate phase transitions to work synergistically to produce high ductility.
In conclusion, the nanostructure design strategy proposed by the study can produce ductile steels with a strength of 2 billion pascals that have attractive compositions and have the potential for large-scale industrial production.
Bulk metal materials and ductility, as well as lean and sustainable chemical composition, are necessary for lightweighting and safety in transportation, buildings and infrastructure. However, in most metallic materials, the increase in strength comes at the expense of ductility, showing a strength-ductility trade-off. This limits the workability and damage tolerance of high-strength alloys, which are necessary for machining and application. Martensitic aging steel is a typical ultra-high strength alloy with a strength of 2GPa, the highest strength of almost all structural metals and alloys produced in large volumes. The strength of martensitic aging steels comes from martensitic matrix and nanometer-sized fine intermetallic phases that have a small lattice mismatch with adjacent lattices that can strengthen the alloy without sacrificing ductility. Metastable austenite can be introduced into a martensitic matrix, using the phase transition induced plasticity (TRIP) effect to synchronously strengthen and ductilize this high-strength steel. The disadvantage of these methods is the use of expensive and strategically limited alloying elements such as Co, Ni, Mo, or Ti, which compromises the sustainability of these alloys so that the increase in ductility remains limited.
Recently, high-density martensitic dislocations have been shown to be effective in improving yield strength through dislocation forest hardening and ductility by sliding of moving dislocations in deformed and partitioned (D&P) steels. In addition, the chemical discontinuity inside austenite as the chemical boundary of medium manganese steel can effectively improve the strength and ductility, and even improve the resistance of steel to hydrogen embrittlement. The introduction of chemical boundaries creates submicron regions with variable austenite stability, forcing martensite into extremely fine martensite-austenite microstructures and enhancing the TRIP effect. With this dislocation and chemical boundary-based engineering strategy, steel with uniform elongation above 15% and tensile strength levels up to 2 GPa can be produced. However, these steels show a wide range of Lüders strips or Portevin-Le Châtelier strips. These are zigzag deformation patterns created by inhomogeneous plastic flow mechanisms, resulting in undesirable deformation inhomogeneity. In addition, the processing steps required to manufacture these steels, including hot rolling, hot rolling, cold rolling, and rapid heating, are quite complex, resulting in low production efficiency and high costs. Therefore, the search for malleable, sustainable, and cost-effective 2-GPa steels is an unsolved problem in itself.
Martensite is the main structural component of all these ultra-high strength steels and is often topologically arranged in an unordered manner, that is, does not follow any topological design or shape criteria. The supersaturation of the interstitial carbon causes its layered structure and quadrangular deformation, giving it high strength, but also brittleness. However, the topological ordered arrangement of martensite helps to convert brittleness into ductility. For example, in steels with layered martensite or prismatic martensite, strength, ductility, and toughness can be significantly improved by layering at specific locations along grain boundaries or phase boundaries.
In particular, interface alignment can play a key role in the malleability of these types of microstructures. In addition, martensite with good orientation and topological arrangement can achieve high interface and body plasticity.
Figure 1. Microstructure evolution of Fe-7.4Mn-0.34C- 1Si-0.2V steel | Source: Science
With all these structural advantages in mind, the study developed a simple and efficient forging route followed by deep cryogenic treatment and tempering to achieve these topological features of medium manganese steel with a bland composition. The hierarchy of materials includes a well-organized martensite structure and a metastable austenite formed in a refined prism-shaped parent austenite. The term "well-organized" refers to a doubly topological arrangement of martensite (0° and 40 to 50°), as explained below. These layered nanostructured steels have tensile strength values of 2.0 to 2.4 GPa, uniform elongation of 18 to 25%, and total elongation of 24 to 30%.
Figure 2. Deformation structure of Fe-7.4Mn-0.34C-1Si-0.2V steel | Source: Science
Overall, the study found that a high-strength steel composed of iron, manganese, silicon, carbon, and vanadium can be made with different processing strategies. The combination of forging, cryogenic treatment and tempering creates an alloy with very high strength while having good ductility and formability. This strategy should be the choice of other steel components.
Paper Link:
[1] https://www.science.org/doi/10.1126/science.ade7471
[2] https://www.science.org/doi/10.1126/science.adc9150
[3] https://www.science.org/doi/10.1126/science.add7857
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