Sweep Rate Research Articles

Thiophene Based Self‐Doped Conducting Polymers as Cathode for Aqueous Zinc‐Ion Battery

AbstractSelf‐doping strategy is well‐known for enhanced ion transport in electrode materials. Herein we report self‐doped thiophene‐based conducting polymer (SDTP), where the dopant SO3− groups function as the hanging ion carrier mimicking a ‘pendulum hand’. It synergistically improves the battery performance, ideally mitigating the dissolution and the enhance ion diffusion kinetics. The diffusion coefficient was determined by three different techniques, i. e., electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration technique (GITT), and cyclic voltammetry at different sweep rates. The calculated diffusion coefficient for the SDTP was found to be much better than the neat thiophene polymer (NTP). The material was evaluated as a cathode for an aqueous zinc‐ion battery. The specific capacitance of the NTP was found to be 178 mAh g−1 at 50 mA g−1 current density. It was drastically reduced to 167, 118.2, and 83 mAh g−1 after the 5th, 10th, and 30th respective cycles. The polymer SDTP outperformed with a specific capacity of 274, 208, 159, 127, 108 mAh g−1 at current densities of 50, 100, 200, 300, 400 mA g−1. It exhibited good rate reversibility, and excellent rate stability with ∼99 % Coulombic efficiency in an over 4000 continuous cycles at 50 mA g−1 suggesting wise molecular engineering is necessary to improve battery performance.

Magnetization loops and non-scaling behavior of flux pinning force of Fe1+y Te1−x Se x studied by numerical simulation

The magnetization of type-II superconductors has usually been described using the critical state models (CSMs). However, CSMs do not consider the time-dependent magnetic relaxation. In this work, to study the influence of magnetic relaxation on the magnetic hysteresis loops (MHLs), critical current density J c, and flux pinning force F p, a numerical method proposed by (Qin and Yao 1996 Phys. Rev. B 54 7536) was adopted and extended to the quasi-two-dimensional case. MHLs at different temperatures measured by using applied field with different sweeping rates can be well reproduced. The critical current density after relaxation J s, and F p can also fit the experimental results well. Based on the numerical simulation, the non-scaling behavior of field-dependent normalized pinning force has been proven to be due to the magnetic relaxation. By comparing the normalized pinning force with the Dew-Hughes model, the dominant pinning type in Fe1+y Te0.6Se0.4 has been confirmed to be the volume Δκ pinning. In addition, the second peak effect is found to be related to the flux lattice transition from elastic lattice to plastic lattice (E-P transition).

The prefrontal cortex of the Mexican free-tailed bat is more selective to communication calls than primary auditory cortex.

In this study, we examined the auditory responses of a prefrontal area, the frontal auditory field (FAF), of an echolocating bat (Tadarida brasiliensis) and presented a comparative analysis of the neuronal response properties between the FAF and the primary auditory cortex (A1). We compared single-unit responses from the A1 and the FAF elicited by pure tones, downward frequency-modulated sweeps (dFMs), and species-specific vocalizations. Unlike the A1, FAFs were not frequency tuned. However, progressive increases in dFM sweep rate elicited a systematic increase of response precision, a phenomenon that does not take place in the A1. Call selectivity was higher in the FAF versus A1. We calculated the neuronal spectrotemporal receptive fields (STRFs) and spike-triggered averages (STAs) to predict responses to the communication calls and provide an explanation for the differences in call selectivity between the FAF and A1. In the A1, we found a high correlation between predicted and evoked responses. However, we did not generate reasonable STRFs in the FAF, and the prediction based on the STAs showed lower correlation coefficient than that of the A1. This suggests nonlinear response properties in the FAF that are stronger than the linear response properties in the A1. Stimulating with a call sequence increased call selectivity in the A1, but it remained unchanged in the FAF. These data are consistent with a role for the FAF in assessing distinctive acoustic features downstream of A1, similar to the role proposed for primate ventrolateral prefrontal cortex.NEW & NOTEWORTHY In this study, we examined the neuronal responses of a frontal cortical area in an echolocating bat to behaviorally relevant acoustic stimuli and compared them with those in the primary auditory cortex (A1). In contrast to the A1, neurons in the bat frontal auditory field are not frequency tuned but showed a higher selectivity for social signals such as communication calls. The results presented here indicate that the frontal auditory field may represent an additional processing center for behaviorally relevant sounds.

Antimony Selenide Thin Films by Electrodeposition: Influence of Deposition Conditions and Post‐Deposition Thermal Treatment on Physical and Photoelectrochemical Properties

Herein, Sb2Se3 thin films are obtained by the electrodeposition technique from a single bath on fluorine‐doped tin oxide (FTO) substrates. The electrodeposition conditions such as precursor concentration and applied potential, as well as the annealing temperature, and its influence on the structural, morphological, optical, and photoelectrochemical properties are analyzed. From the cyclic voltammetry measurements, the range of deposition potential is established and from the sweep rate variation, an irreversible and diffusion‐controlled process is assumed. With the chronoamperometric curves, an instantaneous nucleation is concluded. The Se/Sb ratio variation of the precursor solutions demonstrate that the 0.7 ratio is optimal to obtain Sb2Se3 stoichiometric thin films. The conductivity decreases with the increase of the deposition potential, while the highest photosensitivity is obtained with the film deposited at −0.75 V versus the saturated calomel electrode. Regarding the annealing temperature, a compact homogeneous film is obtained in the range from 325 to 425 °C. Therefore, the suitable properties of Sb2Se3 films obtained by electrodeposition and the establishment of optimized deposition conditions for its use in photoelectrochemical cells (PECs) are demonstrated.

Optical frequency domain polarimetry for distributed polarization crosstalk measurement beyond a 110 dB dynamic range

In this Letter, we present optical frequency domain polarimetry (OFDP), a novel, to the best of our knowledge, distributed polarization crosstalk (DPC) measurement method with a dynamic range beyond 110 dB. It is based on swept-wavelength interferometry using a tunable laser source (TLS) and a delay line interferometer (DLI). The ultrahigh dynamic range is achieved by optimizing the sweep rate of the TLS and the optical path difference of the DLI. Using OFDP, we measured polarization crosstalk below –105 dB in a LiNbO3 waveguide modulator for the first time. OFDP will play a significant role in developing and fabricating high-performance polarization devices.

Nano-confinement coating strategy derived Matryoshka-like carbon nanotubes@anatase nanocrystalline@amorphous carbon nanofibers for ultrafast sodium ion storage

Titania is considered to be an attractive candidate as anode for sodium ion batteries due to excellent cycle stability, advanced safety features, and small volume deformation in the charge-discharge process. However, limited by sodium storage mechanism, the fast charge and discharge performance of multi-crystals titania is failed to satisfy the requirements of commercial application. Here, we develop a Matryoshka-like carbon nanotubes@anatase nanocrystalline@amorphous carbon (CNTs@aTiO2@C) nanofibers for ultrafast sodium ion storage. A nano-confinement coating strategy is demonstrated for constructing an intermediate layer assembled by ultrafine nanocrystalline (2-3 nm) of anatase. The synthesized Matryoshka-like nanofibers with diameters of ∼95 nm consists of amorphous carbon outer layer (10-13 nm), anatase nanocrystalline assembled intermediate layer (13-15 nm), and carbon nanotube core. Benefit from the ultra-refinement of anatase nanocrystalline and Matryoshka-like micro-morphology, the proportion of the capacitive-controlled contribution are up to 90.1 %, 90.6%, 91.9 %, 92.3%, and 93.6% with sweep rate increased from 0.2 to 0.4, 0.6, 0.8, and 1.0 mV s−1, thus result in an outstanding reversible specific capacities of ∼120 mA h g−1 with Coulombic efficiency of ∼99.5% after long-life of 10000 cycles at ultrafast rate of 10 A g−1.

Second-Harmonic Response in Magnetic Nodal-Line Semimetal Fe3GeTe2

We experimentally investigate second-harmonic transverse voltage response to ac electrical current for a magnetic nodal-line semimetal Fe3GeTe2 (FGT). For zero magnetic field, the observed second-harmonic voltage behaves as a square of the longitudinal current, as it should be expected for nonlinear Hall effect. The magnetic field behavior is found to be sophisticated: while the first-harmonic response shows the known anomalous Hall hysteresis in FGT, the second-harmonic Hall voltage is characterized by the pronounced high-field hysteresis and flat (B-independent) region with curves touching at low fields. The high-field hysteresis strongly depends on the magnetic field sweep rate, so it reflects some slow relaxation process. For the lowest rates, it is also accomplished by multiple crossing points. Similar shape of the second-harmonic hysteresis is known for skyrmion spin textures in nonlinear optics. Since skyrmions have been demonstrated for FGT by direct visualization techniques, we can connect the observed high-field relaxation with deformation of the skyrmion lattice. Thus, the second-harmonic Hall voltage response can be regarded as a tool to detect spin textures in transport experiments.

Surface Nanostructure Effects on Dopamine Adsorption and Electrochemistry on Glassy Carbon Electrodes.

Dopamine (DA) adsorption and electron-transfer kinetics are strongly sensitive to the structure and composition of carbon electrodes. Activation of carbon surfaces is a popular method to improve DA detection, but the role of carbon structural features on DA behavior remains uncertain. Herein, we use scanning electrochemical cell microscopy (SECCM) for local anodization of glassy carbon (GC) electrodes in acid media followed by electrochemical imaging of DA adsorption and electrochemistry covering both unmodified and anodized GC regions of the same electrode. Electrochemical measurements of adsorbed DA involve the delivery of DA from the SECCM meniscus (30 μM) for 1 s periods followed by voltammetric analysis at a reasonable sweep rate (47 V s–1). This general approach reduces effects from interelectrode variability and allows for considerable numbers of measurements and statistical analysis of electrochemical data sets. Localized electrode activity is correlated to surface structure and chemistry by a range of characterization techniques. Anodization enhances DA electron-transfer kinetics and provides more sites for adsorption (higher specific surface area). A consequence is that adsorption takes longer to approach completion on the anodized surface. In fact, normalizing DA surface coverage by the electrochemical surface area (ECSA) reveals that adsorption is less extensive on anodized surfaces compared to as-prepared GC on the same time scale. Thus, ECSA, which has often been overlooked when calculating DA surface coverage on carbon electrodes, even where different activation methods would be expected to result in different surface roughness and nanostructure, is an important consideration. Lower graphitic and higher oxygen content on anodized GC also suggest that oxygen-containing functional groups do not necessarily enhance DA adsorption and may have the opposite effect. This work further demonstrates SECCM as a powerful technique for revealing surface structure–function relationships and correlations at heterogeneous electrodes.

Error revising of blade tip-timing parameter identification caused by frequency sweep rate

Blade tip-timing (BTT) is a rotating blade vibration measurement technology. It is a universal and effective method to acquire blade tip displacement data by frequency sweep and identify vibration parameters by single-parameter method. However, when the frequency sweep rate is too large, the vibration parameters obtained by single-parameter method will have large errors because the transient response cannot be immediately attenuated. For this problem, a dimensionless frequency sweep parameter is introduced, and two methods are proposed in this paper. When the engine order is known, an improved single-parameter method is proposed. For the unknown engine order, a revised method of vibration parameters is proposed. The effectiveness of the proposed two methods has been verified by simulation and experiment data. The results showed that when the frequency sweep parameter is between 0.3 and 15, the improved method and the revised method both significantly improve the vibration parameter identification accuracy.

Deepening into the charge storage mechanisms and electrochemical performance of TiO2 hollandite for sodium-ion batteries

The electrochemical performance of TiO2 hollandite, TiO2(H), obtained by complete K+ ion extraction of the bronze K0.2TiO2 is investigated. TiO2 develops a fairly stable capacity of 106 mAh g–1 after 300 cycles at C/8 (42 mA g–1) and maintains 100 mAh g–1 after 600 cycles. At high current rate (2C, 671 mA g–1) 55 mAh g–1 is still maintained. Cycling produces nanosizing of the TiO2 electrode (to 200–300 nm) by electrochemical milling but cyclic voltammetry at different sweep rates indicates that diffusive controlled faradic contribution to the total capacity of TiO2(H) due to Na insertion is significant even at high current. However, participation of pseudocapacitive charge storage is unveiled. The voltage profile resembles in fact that of pseudocapacitive materials with no clear evidence of a constant voltage region. Operando XRD confirmed the lowering of symmetry from tetragonal I4/m to monoclinic I2/m upon sodiation with a relatively narrow two-phase region different from other long plateaus of typical battery materials. Cyclic voltammetry clearly indicates that the two peaks (centered at 1.25 and 0.5 V on reduction) correspond to diffusion-limited faradic processes. Thus, it can be said that hollandite TiO2 is a battery-like material, but for which kinetics is not limited by a biphasic transformation. Instead, kinetics is limited mainly by slow diffusion in single phases with variable composition (continuous variation of voltage vs. capacity) that are formed upon Na+ intercalation into the tunnels. The limited diffusion at high sweep rate favors the dominance of pseudocapacitance (charge transfer at the surface). A comparison with the bronze K0.2TiO2 reveals the importance of potassium in the electrochemical properties and the nature of the different physicochemical processes of both compounds.Sodium ion diffusion coefficient in TiO2(H), 2.6 · 10–13 cm2 s–1, is several orders of magnitude higher than that of TiO2 rutile and anatase, however it does not provide a fast intercalation into the tunnels to consider it a pseudocapacitive intercalation material.

Structure and electrical behavior of silicon nanowires prepared by MACE process

We report on the structure and electrical characteristics of silicon nanowire arrays prepared by metal assisted chemical etching (MACE) method, investigated by cross-sectional scanning electron microscopy (SEM) and high resolution X-ray diffraction (HR-XRD) methods. SEM micrographs show arrays of merged parallel nanowires, with lengths of 700 nm and 1000 nm, resulted after 1.5 min and 5 min etching time, respectively. X-ray reciprocal space maps (RSMs) around Si (004) reciprocal lattice point indicate the presence of 0D structural defects rather than of extended defects. The photoluminescence spectra exhibit emission bands at 1.70 eV and 1.61 eV, with intensity significantly higher in the case of longer wires and associated with the more defected surface. The transient photoluminescence spectroscopy reveals average lifetime of 60 ôs and 111 ôs for the two SiNW arrays, which correlate with a larger density of defects states in the latest case. The I-V characteristics of the nanowires, show a memristive behavior with the applied voltage sweep rate in the range 5–0.32V/s. We attribute this behavior to trap states which control the carrier concentration, and model this effect using an equivalent circuit. Photogeneration processes under excitation wavelengths in visible domain, 405 nm - 650 nm, and under light intensity in the range 20–100 mW/cm2 provided a further insight into the trap states.

Electrooxidation of Platinum

Platinum is an important catalyst widely used in energy conversion and storage, especially in the hydrogen-oxygen polymer electrolyte membrane fuel cell, where it is used at the anode and cathode1. However, potential excursions can lead to surface oxidation and reduction, which restructures the surface and can lower the efficiency of the catalyst and lead to dissolution2. Platinum atoms leave their original lattice sites during oxidation. Surface X-ray diffraction (SXRD) has determined that on Pt(111) the initial stage of Pt extraction is in a place-exchange process, in which the Pt atom moves directly above its original site, which is now occupied by an oxygen atom3. However, on Pt(100) recent work by our team has shown that the initial oxidation gives a “stripe” structure comprising 1D chains of raised Pt and oxygen atoms4.Presented here is an analysis of combined simultaneous SXRD and electrochemistry data for Pt(111) and Pt(100) oxidation in HClO4 and H2SO4. The correlation between the charge transfer and Pt extraction processes is investigated by in-situ cyclic voltammetry, potential step, and potential sweep-hold measurements.The prior structural analysis from a complete set of crystal truncation rods is used find calibration curves for the X-ray intensity of selected anti-Bragg reflections as a function of the coverages θPE of different types of extracted Pt atoms. Integration of charge during electrochemical measurements was converted to electrons passed per surface Pt atoms, to give a notional “electron coverage” θe. In this way, simultaneous measurement of intensity with current during the selected potential program can be converted to θe vs θPE curves. The slopes of these curves are compared with suggested stoichiometric reactions, based on the known SXRD-determined structures. There is some uncertainty insofar as SXRD cannot distinguish O from OH, but we are able to estimate Pt oxidation states. On Pt(111), the electron-transfer and Pt extraction coverage ratios vary with sweep rate, indicating that the rates of adsorption and extraction are kinetically determined and changing during the first oxidation peak. On Pt(100), the stripe structure and stoichiometry suggest a Pt(II) oxide component in the initial stages.We thank other team members involved in various phases of this work: Natalie Stubb (University of Victoria), Valentin Briega-Martos, Daniel Sandbeck (Forschungszentrum Jülich GmbH), Martin Ruge, Ole Fehrs (Kiel University), Federico Calle-Vallejo (Universistat de Barcelona), and the ID31 beamline staff at ESRF. Financial support from NSERC and DFG is appreciated.Reference R. Stamenkovic, D. Strmcnik, P. P. Lopes, N. M. Markovic, Energy and fuels from electrochemical interfaces, Nature materials, 16 (2017) 57-69.J. Sandbeck, O. Brummel, K. J. Mayrhofer, J. Libuda, I. Katsounaros, S. Cherevko, Dissolution of platinum single crystals in acidic medium, ChemPhysChem, 20 (2019) 2997.Drnec, M. Ruge, F. Reikowski, B. Rahn, F. Carlà, R. Felici, J. Stettner, O.M. Magnussen, D.A. Harrington, Initial stages of Pt(111) Electrooxidation: Dynamic and Structural Studies by Surface X-ray Diffraction, Electrochim. Acta, 224 (2017) 220-227.Fuchs, J. Drnec, F. Calle-Vallejo, N. Stubb, D. J. Sandbeck, M. Ruge, S. Cherevko, D. A. Harrington, O. M. Magnussen, Structure dependency of the atomic-scale mechanisms of platinum electro-oxidation and dissolution, Nature Catalysis, 3 (2020) 754-761.

(Digital Presentation) Capacitive Properties of Electrodes Based on Fto Covered By Silver Nanowires

Networks formed with silver nanowires (AgNW) are considered an alternative to conventional transparent conductive oxides – FTO, ITO, AZO, and IZO [1]. Moreover, the AgNW films as flexible support with high conductivity are successfully used. At the same time, the AgNW films can be applied as new electrochemically-active material. It has to be noted that silver-based materials are widely used in the positive electrode of silver-zinc secondary batteries [2]. Following the aforementioned, the AgNW films have a great potential in forming electrodes for transparent flexible micro-batteries. The current work is dedicated to the issues of the AgNW film capacity formed by the spin-coating method.The formation of the films was carried out on the glass substrates covered by fluorine-doped tin oxide (FTO glass). The surface resistivity of the substrate was ≤10 Ohm/sq (China, Zhuhai Kaivo Optoelectronic Technology Co. Ltd). Before coating, the substrates were treated in several steps. First, the substrates were rubbed with Na2SO4 paste. This was followed by rinsing with running and distilled water, as well as treatment in 96% ethanol under sonication (60 W, 41.5 kHz). The formation of the AgNW films on FTO glass was performed by dropping of few drops on the substrate at different speeds from 0 to 5000 rpm. The rotation speed was measured by laser tachometer UT373 (UNI-T, China). After the forming of the AgNW films, they were dried at room temperature and stored in a dark and dry place before use. For the formation of the AgNW films, the solution in isopropanol with a concentration of 5mg/mL was used (China, commercial source). The parameters of AgNW were an average length of 30µm, and an average diameter of 100 nm. For comparison of electrochemical properties, a silver wire with a diameter of 1.25 mm was used.For electrochemical measurements we used potentiostat MTech SPG-500L (Ukraine, [0; +1000 mV] vs NHE with sweep rate 1 or 5 mV/s), potentiostat for EIS Palmsens 4 (Netherlands, Step 5 mV, frequency 100 000 – 0.1 Hz) for cyclic voltammetry. Ag|AgCl electrode was employed as a reference electrode. 0.1 M KOH solution was used for Ag and AgNW electrodes cycling.To estimate the morphology of the AgNW films, an optical microscope (OSEELANG, China) with a camera (Belona, China) and a scanning electron microscope (REM-106I, Ukraine) were used.A comparison of cyclic voltammetry curves of the AgNW film deposited at 1000 rpm and pure silver showed sharp differences – Figure. The position, shape, and changing of peaks differed for nanosized and macro-sized silver.It has to be noted that the forming of relatively transparent films requires small AgNW solution volumes. In this case, the mass of the AgNW films on FTO glass especially at high rotating speeds was insufficient for measuring. To find a way of measuring the AgNW film's weight, a series of experiments were carried out where the relation between detectable mass and electrochemical capacity of the electrode was found. During these experiments, the films with a mass from 0.2 to 0.7 mg were formed using the application of several AgNW solution drops without rotating. The plot of the AgNW mass vs capacity derived from cyclic voltammetry curves was linear and can be expressed by the formula C=k*m, where, C is the capacitance of the AgNW film, k is the experimental coefficient and m is the mass of the AgNW film. Further, this dependence was used for the definition of mass for the AgNW films formed at high rotating speeds.The efficiency of oxidizing and reducing the AgNW films during cathodic and anodic processes was estimated at 26 % of the theoretical one. In addition, according to the scanning electron microscopy images, most of the nanosized wires were split into multiple fragments. Conclusions Dependence between the AgNW films' capacities and their mass has been found, which can be used for AgNW mass estimation not detectable by balance.The efficiency of the AgNW films’ cycling has been estimated, which is 26% of the theoretical one.It has been shown that during cycling, silver nanowires split into multiple fragments. Acknowledgment The authors express their gratitude to the National Scholarship Program of the Slovak Republic and assistance in the program realization to the Slovak Academic Information Agency. References Sharma, N., Nair, N. M., Nagasarvari, G. et al (2022). A review of silver nanowire-based composites for flexible electronic applications. Flexible and Printed Electronics, 7(1).Jeong, J., Lee, J. -W., & Shin, H.-C. (2021). Unique electrochemical behavior of a silver–zinc secondary battery at high rates and low temperatures. Electrochimica Acta, 396. Figure 1

Redox Reactions of Isolated Ferrocene Derivatives Observed By Electrochemical Scanning Tunneling Microscope

Redox reactions on electrode surfaces have been widely applied to fundamental technologies such as energy conversion and storage, metal refining, and electronics. Recently, it has become clear that local structures at the single-atom and single-molecule level affect the efficiency and selectivity of redox reactions [1]. EC-STM, a combination of scanning tunneling microscopy (STM) and electrochemical (EC) measurements, allows direct observation of electrochemical interfaces with high spatial resolution [2], and we aimed to observe the redox reactions of single molecules using this technique. As a target molecule, ferrocene (Fc) was coupled to a tripodal base molecule [3], which was known to form an ordered self-assembled monolayer (SAM) on a gold electrode. By preparing mixed SAM with the molecules with and without Fc moieties, we could stably deposit Fc species on the Au (111) electrode in an isolated and dispersed state, which enables us to observe clear changes in the EC-STM images upon the redox reaction of the single Fc derivative. A mixture of 8,13-trimercaptotriptycene (Trip) and its Fc derivative (Fc-Trip) was deposited on an Au(111) electrode (the molecules were provided by the Fukushima Lab., Chemical Biology Laboratory, Tokyo Institute of Technology, and the Suzuki Lab., Graduate School of Science, Hokkaido University). Cyclic voltammetry (CV) was performed with a potentiostat (HZ-7000, Hokuto Denko) at a sweep rate of 100 mV/s in 0.1 M HClO4 solution. STM measurements were performed using an MS-10 STM (Bruker), controlled by a NanoScope V (Bruker). A Pt/Ir wire coated with Apiezon wax was used as a probe in the home-made electrochemical cell. The sample potential (Esample) was varied from 0.2 V (vs Ag/AgCl) to 0.4 V while the potential difference between the tip and the sample was kept at 0.3 V.The CV results are shown in Fig. 1 (a), where the peak originating from the redox reactions of Fc-Trip is observed (dotted line is only for Trip), indicating that the redox potential of Fc-Trip is ~0.3 V. Since the full width at half maximum of the peak is about 0.1 V, Fc-Trip do not interact with each other and are considered to be isolated and dispersed on the Au(111) electrode [4]. Corresponding EC-STM images are shown in Fig. 1 (c)-(e). While the bright spots derived from Fc-Trip are observed at Esample = 0.2 V (the tip potential Etip is 0.5 V), as indicated by white circles, the bright spots almost disappeared at Esample = 0.4 V (Etip = 0.7 V). We confirmed that the change of the height is reversible with respect to the applied potentials, as shown in Fig. 1(c) and 1(e). The height of the bright spot in the EC-STM image reflects the electron transfer rate through the redox molecule between the tip and the sample. When the sample potential is set to 0.2 V, Fc-Trip is formally in the reduced state, but the electrons are readily transferred to the tip regulated at 0.5 V. On the other hand, when the sample potential is set to settle the oxidized state (0.4 V), the molecule cannot pass electrons to the high potential tip. Therefore, in the case of Fig. 1(d), the current between the tip and the sample is not increased with the presence of the Fc moiety, leading to the apparent disappearance of spots. We noticed that some bright spots did not disappear at Esample = 0.4 V (an arrow in Fig. 1(d)), which suggests that there is heterogeneity in the redox reactivity. In the future, we plan to investigate the heterogeneity by combining spectroscopic techniques with the EC-STM measurement.[1] J. H. K. Pfisterer et al., Nature , 74, 549 (2017)[2] Y. Yokota et al., J. Phys. Chem. C, 111, 7561 (2007)[3] F. Ishiwari et al., J. Am. Chem. Soc., 141, 5995 (2019)[4] C. E. D. Chidsey et al., J. Am. Chem. Soc., 112, 4301 (1990) Figure 1

Visualization of ex vivo rabbit olfactory mucosa and foramina with three-dimensional optical coherence tomography

There is increasing interest in developing a minimally invasive imaging modality to safely evaluate dynamic microscopic changes of the olfactory mucosa and cribriform foramina. Herein, we utilized three-dimensional (3D) optical coherence tomography (OCT) to characterize the ex vivo stratified substructure of olfactory mucosa in rabbits and create 3D reconstructed images of olfactory foramina. Olfactory mucosa and cribriform plates from four New Zealand White rabbits were dissected and imaged using two swept-source OCT systems: (1) 1.3-µm (μm) center wavelength, 100-nm bandwidth, 200-kHz sweep rate, and (2) 1.7-μm center wavelength, 120-nm bandwidth, 90-kHz sweep rate. Volumetric OCT images were compiled to create a 3D reconstruction of the cribriform plate. The ability of OCT to distinguish the olfactory mucosa substructure and foramina was compared to histology. To estimate imaging penetration depth of each system, the first-order exponential decays of depth-resolved intensity were calculated and compared using a paired t-test. Three-dimensional OCT depicted the stratified layered structures within the olfactory mucosa correlating with histology. The epithelium and lamina propria were measured to be 32μm and 107μm in 1.3-μm OCT compared to 30μm and 105μm in histology. Olfactory foramina were visualized via 3D reconstruction. The 1.7-μm system provided greater depth penetration compared to the 1.3-μm system, allowing for improved foramina visualization. We have shown that OCT can be used to image non-pathologic olfactory mucosa and foramina. Implications for this work include diagnostic and therapeutic potentials for neurorhinological and neurodegenerative diseases.

BiO 2-x Nanosheets with Surface Electron Localizations for Efficient Electrocatalytic CO 2 Reduction to Formate

BiO _2-x Nanosheets with Surface Electron Localizations for Efficient Electrocatalytic CO ₂ Reduction to Formate

Poly (Bromocresol purple) incorporated pencil graphite electrode for concurrent determination of serotonin and levodopa in presence of L-Tryptophan: A voltammetric study

In the present investigation, the new electrochemical sensor was established based on the electropolymerisation of Bromocresol purple on pencil graphite electrode for the sensitive detection of serotonin(5-HT) and Levodopa(LD) in assistance with L- Tryptophan(TRP). The morphological characterisation of developed working electrode was done by Scanning Electron Microscope(SEM). The modified sensor presents admirable electrocatalytic performance towards specific and selective examination of 5-HT, LD and TRP at 0.2 M Phosphate buffer solution of physiological pH having the speed rate of 50 mV/s using cyclic voltammetric(CV) and differential pulse voltammetric(DPV) methods. The distinct experimental conditions like impact of supporting electrolyte, dissimilar concentration and varied sweep rates were optimised to accomplish a better peak current. The designed sensor effectually lowers the detection limits of 5-HT (0.49 μM) and LD (2.3 μM) and it is easy to fabricate, disposable, highly stable and applicable to practical analysis of bioactive molecules.

Charging processes of Na4Mn9O18 electrode in aqueous electrolyte

Recent trends in electrochemical energy storage –the renewed interest in aqueous electrolytes, the development of nanostructured and/or hybridized materials, the advent of unconventional systems– call for detailed analyses of charging processes. We address this issue in studying a sodium manganese oxide (Na4Mn9O18, NMO) electrode in aqueous environment. Charge storage is examined by cyclic voltammetry (CV) in a wide range of sweep rate (ν) and by equivalent circuit modelling of the electrode impedance response. Voltammetry shows that, with increasing ν, the insertion process evolves from a quasi-equilibrium behavior (ν ≤ 0.1 mV s–1) towards a diffusion controlled regime overlapping with capacitive charging (ν ≥ 0.2 mV s–1), and culminates at even higher rate (ν > 2 mV s–1) in mixed mass transport ohmic control. Impedance analysis permits to discriminate the varying character of charge storage, revealing the low frequency dominance of faradaic insertion and the rising contribution of pseudocapacitive and double layer charging at higher frequency. We show that the frequency decomposition of charging mechanisms obtained by this analysis can be reconciled with the CV analysis. For further clarification of the above analysis in particular, and as a relevant aspect of the NMO behavior in general, we evaluate the chemical diffusion coefficient of Na-ion as a function of potential.

The multiple synthesis of 2D layered MXene Ti3C2Tx/Ag/Cu composites with enhanced electrochemical properties

The reactive groups present on the surface of two-dimensional layered Ti3C2Tx materials confer natural superiority to self-assembly compared to other two-dimensional materials. The Ti3C2Tx/Ag/Cu composites are prepared using the unique direct reduction and high adsorption capacity possessed by Ti3C2Tx. The Ag NPs and Cu NPs growing between the Ti3C2Tx layers act as supports to prevent the occurrence of defects such as aggregation and collapse of the structure. Meanwhile, the layer spacing of Ti3C2Tx increases, thus exposing more active sites and accelerating the diffusion ability of ions in the electrolyte. The Ag NPs and Cu NPs on the surface of Ti3C2Tx and at the edges of the layers combine with each other to form the multi-channel, short distance conductive path, which effectively improves the electron transfer efficiency. The capacitance contribution of Ti3C2Tx/Ag/Cu composites reaches 74% at high sweep rates. The Ti3C2Tx/Ag/Cu composites can be considered as electrode materials for batteries and capacitors with low internal resistance(0.662 Ω), high electrical conductivity and stable chemical properties.

Threshold voltage instability and hysteresis in gamma-rays irradiated 4H-SiC junction field effect transistors

High dose irradiation effects of gamma-rays up to 17 MGy (H2O) on 4H-SiC junction field effect transistors (JFETs) were investigated. Due to the irradiation, gradual positive threshold voltage (Vth) shift as high as 0.5 V and continuous decrease in transconductance gm were observed. In addition, Vth instability and hysteresis appeared for the irradiated JFETs when the gate voltage (VG) sweep direction, sweep interval, i.e., averaged sweeping rate, sweep range, and delay time were changed. Increase of VG interval attributed to positive Vth shift for both forward and reverse directions, whereas narrowing of sweep range and increase of delay time resulting in a more noticeable negative shift of Vth for the reverse direction. Such Vth hysteresis indicates that capture and release of carriers predominantly took place via hole traps formed around the gate region due to high dose gamma-ray irradiation.