Obtaining the heterogeneous conformation of small proteins is important for understanding their biological role, but it is still challenging. Here, we developed a multi-tilt nanoparticle-aided ...cryo-electron microscopy sampling (MT-NACS) technique that enables the observation of heterogeneous conformations of small proteins and applied it to calmodulin. By imaging the proteins labeled by two gold nanoparticles at multiple tilt angles and analyzing the projected positions of the nanoparticles, the distributions of 3D interparticle distances were obtained. From the measured distance distributions, the conformational changes associated with Ca2+ binding and salt concentration were determined. MT-NACS was also used to track the structural change accompanied by the interaction between amyloid-beta and calmodulin, which has never been observed experimentally. This work offers an alternative platform for studying the functional flexibility of small proteins.
Controlling the electrochemical CO2 reduction process for multicarbon production is challenging. Ethanol is typically produced with lower selectivity compared to ethylene. In addition, ill-defined ...catalytic active sites and elusive mechanisms of C–C coupling further hinder the enhancement of ethanol generation. Here, we carefully regulated the quantity of the Cu atoms and deposited them onto a Ag inverse-opal structure (AgIOs) using the pulse-electrodeposition method. Subnanometer Cu clusters demonstrated a 2.5 times higher Faradaic efficiency for ethanol production compared to that for ethylene at −1.05 V vs RHE. Conversely, as the size of Cu increased to nanometers, ethylene became the dominant product. Excessive adsorption of CO on Cu clusters, which migrates from the Ag surface, is attributed to the improved ethanol production. Abundant Ag/Cu boundaries and adjacent spacing between Ag and Cu clusters may enhance the surface migration of CO. In contrast, the preferential site-selective CO adsorption on large Cu nanoparticles is associated with solution-mediated CO migration. Operando shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) revealed a high coverage of the CO on the Cu clusters. The initial intermediate *OCCOH by C–C coupling appeared for both Cu clusters and nanoparticles. However, Cu clusters accommodated more carbonaceous intermediates, highlighting the critical role of CO and intermediate coverages on Cu in ethanol production.
Atomic electron tomography (AET) has become a powerful tool for atomic-scale structural characterization in three and four dimensions. It provides the ability to correlate structures and properties ...of materials at the single-atom level. With recent advances in data acquisition methods, iterative three-dimensional (3D) reconstruction algorithms, and post-processing methods, AET can now determine 3D atomic coordinates and chemical species with sub-Angstrom precision, and reveal their atomic-scale time evolution during dynamical processes. In this work, we review the recent experimental and algorithmic developments of AET and highlight several groundbreaking experiments, which include pinpointing the 3D atom positions and chemical order/disorder in technologically relevant materials and capturing how atoms rearrange during early nucleation at four-dimensional atomic resolution.
Highways for Spins
The spins efficiently move on the highways formed by two topological nodal lines in Fe3GaTe2. The brighter, upward, and large arrows indicate the presence of strongly correlated ...states that can preserve the spins traveling on the highways. In the cover image, Yeongkwan Kim, Myung Joon Han, Heejun Yang, and co‐workers express the flat nodal lines in Fe3GaTe2 by the two straight ways for spins, and the spins' moving on the highways is observed as exceptionally the high anomalous Hall effect in Fe3GaTe2. More details can be found in article number 2402040.
Metastable phases-kinetically favoured structures-are ubiquitous in nature
. Rather than forming thermodynamically stable ground-state structures, crystals grown from high-energy precursors often ...initially adopt metastable structures depending on the initial conditions, such as temperature, pressure or crystal size
. As the crystals grow further, they typically undergo a series of transformations from metastable phases to lower-energy and ultimately energetically stable phases
. Metastable phases sometimes exhibit superior physicochemical properties and, hence, the discovery and synthesis of new metastable phases are promising avenues for innovations in materials science
. However, the search for metastable materials has mainly been heuristic, performed on the basis of experiences, intuition or even speculative predictions, namely 'rules of thumb'. This limitation necessitates the advent of a new paradigm to discover new metastable phases based on rational design. Such a design rule is embodied in the discovery of a metastable hexagonal close-packed (hcp) palladium hydride (PdH
) synthesized in a liquid cell transmission electron microscope. The metastable hcp structure is stabilized through a unique interplay between the precursor concentrations in the solution: a sufficient supply of hydrogen (H) favours the hcp structure on the subnanometre scale, and an insufficient supply of Pd inhibits further growth and subsequent transition towards the thermodynamically stable face-centred cubic structure. These findings provide thermodynamic insights into metastability engineering strategies that can be deployed to discover new metastable phases.
Abstract Resistive switching devices have been regarded as a promising candidate of multi-bit memristors for synaptic applications. The key functionality of the memristors is to realize multiple ...non-volatile conductance states with high precision. However, the variation of device conductance inevitably causes the state-overlap issue, limiting the number of available states. The insufficient number of states and the resultant inaccurate weight quantization are bottlenecks in developing practical memristors. Herein, we demonstrate a resistive switching device based on Pt/LaAlO3/SrTiO3(Pt/LAO/STO) heterostructures, which is suitable for multi-level memristive applications. By redistributing the surface oxygen vacancies, we precisely control the tunneling of two-dimensional electron gas (2DEG) through the ultrathin LAO barrier, achieving multiple and tunable conductance states (over 27) in a non-volatile way. To further improve the multi-level switching performance, we propose a variance-aware weight quantization (VAQ) method. Our simulation studies verify that the VAQ effectively reduces the state-overlap issue of the resistive switching device. We also find that the VAQ states can better represent the normal-like data distribution and, thus, significantly improve the computing accuracy of the device. Our results provide valuable insight into developing high-precision multi-bit memristors based on complex oxide heterostructures for neuromorphic applications.
Topological quantum phases are largely understood in weakly correlated systems, which have identified various quantum phenomena, such as the spin Hall effect, protected transport of helical fermions, ...and topological superconductivity. Robust ferromagnetic order in correlated topological materials particularly attracts attention, as it can provide a versatile platform for novel quantum devices. Here, a singular Hall response arising from a unique band structure of flat topological nodal lines in combination with electron correlation in a van der Waals ferromagnetic semimetal, Fe3GaTe2, with a high Curie temperature of Tc = 347 K is reported. High anomalous Hall conductivity violating the conventional scaling, resistivity upturn at low temperature, and a large Sommerfeld coefficient are observed in Fe3GaTe2, which implies heavy fermion features in this ferromagnetic topological material. The scanning tunneling microscopy, circular dichroism in angle‐resolved photoemission spectroscopy, and theoretical calculations support the original electronic features of the material. Thus, low‐dimensional Fe3GaTe2 with electronic correlation, topology, and room‐temperature ferromagnetic order appears to be a promising candidate for robust quantum devices.
A singular Hall response arising from a unique band structure of flat topological nodal lines in combination with electron correlation in a layered room‐temperature ferromagnet, Fe3GaTe2 is reported. Exceptionally high anomalous Hall conductivity violating the conventional scaling, resistivity upturn at low temperatures, and a large Sommerfeld coefficient of Fe3GaTe2 imply heavy fermion features in the ferromagnetic topological material.
