Additional file 1 of Suitability of visual cues for freezing of gait in patients with idiopathic Parkinson’s disease: a case–control pilot study

Additional File 1: A document file with additional tables

Investigating the Kinetic Effect on Structural Evolution of Li_<i>x</i>Ni_0.8Co_0.15Al_0.05O₂ Cathode Materials during the Initial Charge/Discharge

In this work, we investigate the structural evolution and reaction kinetics of Li_<i>x</i>Ni_0.8Co_0.15Al_0.05O₂ (NCA) cathode materials induced by the initial charge/discharge as a function of the state of charge (SOC 50 and 90%) and C-rates (0.1–10C), with a combination of high-resolution transmission electron microscopy (HRTEM) imaging, selected area electron diffraction (SAED), and electron energy loss spectroscopy (EELS). During initial charging, the effects of C-rates on the structural modifications of NCA cathode materials are strongly dependent on how much the lithium is extracted from the pristine NCA. The structural modifications become more substantial as the extent of the charge increases, particularly at higher C-rates. In the highly delithiated state (90% SOC), even the particles charged at the same C-rate show significant variations in the degree of the structural modifications. The changes in the crystallographic and electronic structures at the subsurface scales, which were induced by the initial charging to 90% SOC at the rate of 0.1C, are nearly recovered during the initial discharge, except for the NCA discharged at the rate of 10C. To quantify the extent of the irreversible phase transition at the nanoscale, we have utilized HRTEM imaging and scanning transmission electron microscopy (STEM)–EELS line scanning techniques, which enable us to draw complementary results. This comparative analysis provides valuable information that is useful not only for obtaining a complete understanding of the mechanisms by which the degradation is initiated, but also for improving and designing Ni-rich layered cathode materials with better charging and discharging kinetics

Structural Evolution of Li_<i>x</i>Ni_<i>y</i>Mn_<i>z</i>Co_1‑y‑zO₂ Cathode Materials during High-Rate Charge and Discharge

Ni-rich lithium transition metal oxides have received significant attention due to their high capacities and rate capabilities determined via theoretical calculations. Although the structural properties of these materials are strongly correlated with the electrochemical performance, their structural stability during the high-rate electrochemical reactions has not been fully evaluated yet. In this work, transmission electron microscopy is used to investigate the crystallographic and electronic structural modifications of Ni-based cathode materials at a high charge/discharge rate of 10 C. It is found that the high-rate electrochemical reactions induce structural inhomogeneity near the surface of Ni-rich cathode materials, which limits Li transport and reduces their capacities. This study establishes a correlation between the high-rate electrochemical performance of the Ni-based materials and their structural evolution, which can provide profound insights for designing novel cathode materials having both high energy and power densities

Investigation of Thermal Stability of P2–Na_<i>x</i>CoO₂ Cathode Materials for Sodium Ion Batteries Using Real-Time Electron Microscopy

Here, we take advantage of <i>in situ</i> transmission electron microscopy (TEM) to investigate the thermal stability of P2-type Na_<i>x</i>CoO₂ cathode materials for sodium ion batteries, which are promising candidates for next-generation lithium ion batteries. A double-tilt TEM heating holder was used to directly characterize the changes in the morphology and the crystallographic and electronic structures of the materials with increase in temperature. The electron diffraction patterns and the electron energy loss spectra demonstrated the presence of cobalt oxides (Co₃O₄, CoO) and even metallic cobalt (Co) at higher temperatures as a result of reduction of Co ions and loss of oxygen. The bright-field TEM images revealed that the surface of Na_<i>x</i>CoO₂ becomes porous at high temperatures. Higher cutoff voltages result in degrading thermal stability of Na_<i>x</i>CoO₂. The observations herein provide a valuable insight that thermal stability is one of the important factors to be considered in addition to the electrochemical properties when developing new electrode materials for novel battery systems

Improving the Stability of High-Performance Multilayer MoS₂ Field-Effect Transistors

In this study, we propose a method for improving the stability of multilayer MoS₂ field-effect transistors (FETs) by O₂ plasma treatment and Al₂O₃ passivation while sustaining the high performance of bulk MoS₂ FET. The MoS₂ FETs were exposed to O₂ plasma for 30 s before Al₂O₃ encapsulation to achieve a relatively small hysteresis and high electrical performance. A MoO<i>_x</i> layer formed during the plasma treatment was found between MoS₂ and the top passivation layer. The MoO<i>_x</i> interlayer prevents the generation of excess electron carriers in the channel, owing to Al₂O₃ passivation, thereby minimizing the shift in the threshold voltage (<i>V</i>_th) and increase of the off-current leakage. However, prolonged exposure of the MoS₂ surface to O₂ plasma (90 and 120 s) was found to introduce excess oxygen into the MoO<i>_x</i> interlayer, leading to more pronounced hysteresis and a high off-current. The stable MoS₂ FETs were also subjected to gate-bias stress tests under different conditions. The MoS₂ transistors exhibited negligible decline in performance under positive bias stress, positive bias illumination stress, and negative bias stress, but large negative shifts in <i>V</i>_th were observed under negative bias illumination stress, which is attributed to the presence of sulfur vacancies. This simple approach can be applied to other transition metal dichalcogenide materials to understand their FET properties and reliability, and the resulting high-performance hysteresis-free MoS₂ transistors are expected to open up new opportunities for the development of sophisticated electronic applications

Evolution in Catalyst Morphology Leads to Carbon Nanotube Growth Termination

A mechanism by which catalyst deactivation occurs during vertically aligned single-walled carbon nanotube (SWNT) growth is demonstrated. We have used both quantitative measurements of nanotube growth rates and ex situ and in situ transmission electron microscopy observations to show that termination of carbon nanotube (CNT) array growth can be intrinsically linked to evolution of the catalyst morphology. Specifically, we find that a combination of both Ostwald ripening and subsequent subsurface diffusion leads to loss of the Fe catalyst, and through direct observations, we correlate this with nanotube growth termination. These observations indicate that careful design of the catalyst and its support − as well as the interaction between the two − is required to maximize nanotube yields