Embedding Heterostructured α‐MnS/MnO Nanoparticles in S‐Doped Carbonaceous Porous Framework as High‐Performance Anode for Lithium‐Ion Batteries

In this work, the synthesis of α-MnS/MnO/S-doped C micro-rod composites via a simple sulfidation process is demonstrated, starting from a Mn-based metal-organic framework. The resulting heterostructured α-MnS/MnO nanoparticles (8±2 nm) are uniformly embedded into the S-doped carbonaceous porous framework with hierarchical micro-/meso-porosity. The combination of structural and compositional characteristics results in the promising electrochemical performance of the as-obtained composites as anode materials for lithium-ion batteries, coupled with high reversible capacity (940 mAh $g^{−1}$ at 0.1 A $g^{−1}$), excellent rate capability as well as long cycling lifespan at high rate of 2.0 A $g^{−1}$ for 2000 cycles with the eventual capacity of ∼300 mAh $g^{−1}$. Importantly, in situ X-ray diffraction studies clearly reveal mechanistic details of the lithium storage mechanism, involving multistep conversion processes upon initial lithiation

Unveiling the Intricate Intercalation Mechanism in Manganese Sesquioxide as Positive Electrode in Aqueous Zn‐Metal Battery

In the family of Zn/manganese oxide batteries with mild aqueous electrolytes, cubic α-Mn$_{2}$O$_{3}$ with bixbyite structure is rarely considered, because of the lack of the tunnel and/or layered structure that are usually believed to be indispensable for the incorporation of Zn ions. In this work, the charge storage mechanism of α-Mn$_{2}$O$_{3}$ is systematically and comprehensively investigated. It is demonstrated that the electrochemically induced irreversible phase transition from α-Mn$_{2}$O$_{3}$ to layered-typed L-Zn$_{x}$MnO$_{2}$, coupled with the dissolution of Mn$^{2+}$ and OH$^{-}$ into the electrolyte, allows for the subsequent reversible de-/intercalation of Zn$^{2+}$. Moreover, it is proven that α-Mn$_{2}$O$_{3}$ is not a host for H$^{+}$. Instead, the MnO$_{2}$ formed from L-Zn$_{x}$MnO$_{2}$ and the Mn^{2+ in the electrolyte upon the initial charge is the host for H$^{+}$. Based on this electrode mechanism, combined with fabricating hierarchically structured mesoporous α-Mn$_{2}$O$_{3}$ microrod array material, an unprecedented rate capability with 103 mAh g−1 at 5.0 A g−1 as well as an appealing stability of 2000 cycles (at 2.0 A g$^{-1}$) with a capacity decay of only ≈0.009% per-cycle are obtained

Direct Imaging of Atomic Permeation Through a Vacancy Defect in the Carbon Lattice

Porous graphene has shown promise as a new generation of selective membrane for sieving atoms, ions and molecules. However, the atomistic mechanisms of permeation through defects in the graphenic lattice are still unclear and remain unobserved in action, at the atomic level. Here, the direct observation of palladium atoms from a nanoparticle passing through a defect in a single-walled carbon nanotube one-by-one has been achieved with atomic resolution in real time, revealing key stages of the atomic permeation. Bonding between the moving atom and dangling bonds around the orifice, immediately before and after passing through the subnano-pore, plays an important role in the process. Curvature of the graphenic lattice crucially defines the direction of permeation from concave to convex side due to a difference in metal-carbon bonding at the curved surfaces as confirmed by density functional theory calculations, demonstrating the potential of porous carbon nanotubes for atom sieving

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Stimulate and image metal-related chemical reactions by aberration-corrected transmission electron microscopy

The research presented in this cumulative thesis focuses on the development of the methodology of low-voltage aberration-corrected high-resolution transmission electron microscopy (LV-ACHRTEM) for stimulating and observing metal involved molecular chemical reactions. The dissertation is based on four peer-reviewed journal articles, which were the result of an interdisciplinary research involving TEM technology, chemistry, catalysis, material science and physics being conducted at the Electron Microscopy Group of Materials Science at Ulm University. In TEM, the interactions between the incident high-energetic electrons and the sample atoms endow scientists with the opportunities to explore the structural and spectral information of materials. For bio-molecules, great advances have been recently demonstrated in cryo-TEM taking advances of direct electron detection and improved data reconstruction techniques. With the development of aberration correctors, atomically-resolved TEM imaging became reality, provided that the interactions between the incident electrons and the sample do not prevent this. Now, for the first time, there is the potential for discovering the atomic structure and dynamic of materials and even single molecules. This gives the opportunity to realize the ultimate target of chemistry: observing and controlling molecular reactions at the atomic level. Nowadays, studying molecule with atomic resolution represents itself one very challenging areas of TEM. Individual molecules including inorganic molecules ([W6I142-]n, fullerene etc.) and organic molecules (ortho-carborane, C3-tribromide etc.), have been investigated by ACTEM for studying their structure and/or dynamics. Although the high-energy incident electrons are unavoidable for TEM experiments, they inevitably can damage the specimen during the experiment. It is the ‘observer effect’ in TEM, which means incident electrons necessarily change the specimen. The damage in TEM includes knock-on damages, radiolysis and heating. Low-voltage transmission electron microscopy, low-dose imaging techniques, and cryo-TEM are the main methods that have been developed for protecting specimens from beam damage. The only possible way to lower the specimen’s knock-on displacement damage threshold is reducing the accelerating voltage of incident electrons. LV-ACHRTEM defined for accelerating voltages lower than 80 kV, becomes the most powerful tool to study the electron-irradiationsensitive materials like graphene, carbon nanotubes and 2D transition metal dichalcogenide, to name a few of them. In this work, transition metal molecules including transition metal clusters contain metal atoms less than 30 and transition metal diatomic molecule are the objects of study for investigating the catalytic performance and dynamics, nucleation process and confirming the existence of metal diatomic molecule. For the LV-ACTEM experiment of transition metal molecules, it is important and necessary to understand how the electron beam affects different molecules through its interactions. Furthermore, the aim is to applying high energy electron beam as a stimulus for driving molecular reactions and simultaneously as a probe for monitoring the reaction with atomic resolution. Furthermore, we may be able to create new structures by manipulations with the electron beam. Combining with the LV-ACHRTEM technology, we utilize the kinetic energy transferred from the incident electron beam to the atoms in the specimen to stimulate and image the metal-related molecular reactions. A single walled carbon nanotube (SWNT) with its properties of excellent electrical and thermal conductivity, atomic thin and tough structure is applied as nano test tube for the encapsulating molecule-level transition metal clusters and Rhenium diatomic molecule [Ⅰ-Ⅳ]. Owing to the good electrical and thermal conductivity of SWNT, the ionization and heating processes caused by inelastic scattering are negligible. The inevitable elastic scattering is the main interaction between the electron beam and our system. The kinetic energy transferred from the incident electron beam to the specimen by elastic scattering are determined by the accelerating voltage and precisely controlled by the dose rate to stimulate the physical and chemical processes with similar threshold energy. Thus, by approach and after careful analysis of time-dependent image series, image calculations and theoretical modelling, the atomic dynamics of the growth of SWNT catalyzed by Re cluster are directly observed [Ⅰ]; the carbon reconstruction reactions catalyzed by 14 kinds of transition metal clusters are imaged with atomic resolution and are semiquantitatively compared [Ⅱ]; the in-situ nucleation of metal nanocrystals are realized and observed which proved the nucleation of metal to undergo the two-step nucleation mechanism [Ⅲ]; the Rhenium diatomic molecule containing alterable multiple bond are discovered [Ⅳ]

Technology for Position Correction of Satellite Precipitation and Contributions to Error Reduction—A Case of the ‘720’ Rainstorm in Henan, China

In July 2021, an extreme precipitation event occurred in Henan, China, causing tremendous damage and deaths; so, it is very important to study the observation technology of extreme precipitation. Surface rain gauge precipitation observations have high accuracy but low resolution and coverage. Satellite remote sensing has high spatial resolution and wide coverage, but has large precipitation accuracy and distribution errors. Therefore, how to merge the above two kinds of precipitation observations effectively to obtain heavy precipitation products with more accurate geographic distributions has become an important but difficult scientific problem. In this paper, a new information fusion method for improving the position accuracy of satellite precipitation estimations is used based on the idea of registration and warping in image processing. The key point is constructing a loss function that includes a term for measuring two information field differences and a term for a warping field constraint. By minimizing the loss function, the purpose of position error correction of quantitative precipitation estimation from FY-4A and Integrated Multisatellite Retrievals of GPM are achieved, respectively, using observations from surface rain gauge stations. The errors of different satellite precipitation products relative to ground stations are compared and analyzed before and after position correction, using the ‘720’ extreme precipitation in Henan, China, as an example. The experimental results show that the final run has the best performance and FY-4A has the worse performance. After position corrections, the precipitation products of the three satellites are improved, among which FY-4A has the largest improvement, IMERG final run has the smallest improvement, and IMERG late run has the best performance and the smallest error. Their mean absolute errors are reduced by 23%, 14%, and 16%, respectively, and their correlation coefficients with rain gauge stations are improved by 63%, 9%, and 16%, respectively. The error decomposition model is used to examine the contributions of each error component to the total error. The results show that the new method improves the precipitation products of GPM primarily in terms of hit bias. However, it does not significantly reduce the hit bias of precipitation products of FY-4A while it reduces the total error by reducing the number of false alarms