Pt Single Atoms Loaded on Thin-Layer TiO2 Electrodes: Electrochemical and Photocatalytic Features.

Recently, the use of Pt in the form of single atoms (SA) has attracted considerable attention to promote the cathodic hydrogen production reaction from water in electrochemical or photocatalytic settings. First, produce suitable electrodes by Pt SA deposition on Direct current (DC)-sputter deposited titania (TiO2) layers on graphene-these electrodes allow to characterization of the electrochemical properties of Pt single atoms and their investigation in high-resolution HAADF-STEM. For Pt SAs loaded on TiO2, electrochemical H2 evolution shows only a very small overpotential. Concurrent with the onset of H2 evolution, agglomeration of the Pt SAs to clusters or nanoparticles (NPs) occurs. Potential cycling can be used to control SA agglomeration to variable-size NPs. The electrochemical activity of the electrode is directly related to the SA surface density (up to reaching the activity level of a plain Pt sheet). In contrast, for photocatalytic H2 generation already a minimum SA density is sufficient to reach control by photogenerated charge carriers. In electrochemical and photocatalytic approaches a typical TOF of ≈100-150 H2 molecules per second per site can be reached. Overall, the work illustrates a straightforward approach for reliable electrochemical and photoelectrochemical investigations of SAs and discusses the extraction of critical electrochemical factors of Pt SAs on titania electrodes.

Rapid determination of uracil in biological fluids at mercury thin film electrode for early detection of potential 5-fluorouracil toxicity due to dihydropyrimidine dehydrogenase deficiency.

Determination of plasma uracil was reported as a method for evaluation of Dihydropyrimidine dehydrogenase (DPD) activity that is highly demanded to ensure the safe administration of 5-fluorouracil (5-FU)-based therapies to cancer patients. This work reports the development of a simple electroanalytical method based on adsorptive stripping square wave voltammetry (AdSWV) at mercury film-coated glassy carbon electrode (MF/GCE) for the highly sensitive determination of uracil in biological fluids that can be used for diagnosis of decreased DPD activity. Due to the formation of the HgII-Uracil complex at the electrode surface, the accuracy of the measurement was not affected by the complicated matrices in biological fluids including human serum, plasma, and urine. The high sensitivity of the developed method results in a low limit of detection (≈1.3 nM) in human plasma samples, falling below the practical cut-off level of 15 ng mL-1 (≈0.14 µM). This threshold concentration is crucial for predicting 5-FU toxicity, as reported in buffer, and ≤1.15% in biological samples), and accuracy (recovery percentage close to 100%).

On the Design, Fabrication, and Characterization of a Novel Thin-Film Electrode Array for Use in Cochlear Implants.

Thin-film electrode arrays (TFEAs) have been developed as an alternative to conventional electrode arrays (CEAs) used in cochlear implants. However, TFEAs produced by microfabrication techniques have not yet been used clinically because their structural and mechanical properties are far from those of CEAs. The aim of this study is to design, fabricate, and investigate the mechanical and tribological behavior and evaluate the performance of different TFEA designs. Finite Element Analysis (FEA) is performed to determine the elastic properties of several designs. A custom-build experimental setup is designed to observe the tribological behavior in different speeds and environments where frictional (lateral) and vertical force (normal force) are measured on a flat surface and within artificial cochlea. According to the FEA results, the maximum stiffness of the CEA is 37.93 mN/mm and 0.363 mN/mm and TFEA-4 has a maximum stiffness of 39.08 mN/mm and 0.306 mN/mm in the longitudinal and transverse axes, respectively. It is shown experimentally that adding a dummy wire to the carrier of the EA enhances both its longitudinal and transverse stiffness, thereby postponing the initiation of dynamic sliding due to the elevated buckling limit. It is also revealed that the type of TFEA support structure affects both normal and frictional forces, as well as the coefficient of friction.

Enhanced Electrochemical Performance in Supercapacitors through KCu-Cy Based Metal-Organic Framework Electrodes.

In the realm of electronics and electric energy storage, the convergence of organic and metallic materials has yielded promising outcomes. In this study, we introduce a novel metal-organic polymer synthesized from Cyamelurate and copper (KCu-Cy) and explore its application as an electrode for a supercapacitor. This material was pressed onto a stainless-steel grid as a thin film and synthesized on nickel foam. Comprehensive characterization was carried out to confirm the synthesis, ensure phase purity, and investigate atomic interactions. Single Crystal X-ray Diffraction (SCXRD) and Powder X-ray Diffraction (PXRD) analyses verified the synthesis and phase purity, shedding light on atomic arrangements. Fourier Transform Infrared Spectroscopy (FTIR) analyses provided insights into characteristic peaks within the material. Thermal Gravimetric Analysis (TGA) gauged stability and durability. Electrochemical performance was assessed through cyclic voltammetry. Notably, the nickel-supported electrodes, devoid of binders, exhibited exceptional specific capacity, reaching 1210.89 F/g at a scan rate of 5 mV/s, in contrast to 363.73 F/g for the pressed thin film on the stainless-steel grid, which incorporated a conductive agent and binder. Cu-Cy displayed impressive cyclization resistance, with a capacity retention of 90 % even after 11000 cycles. These findings underline the promise of Cu-Cy as a high-performance electrode material for supercapacitors, particularly in binder-free configurations, and suggest its potential in advanced energy storage applications.

A simple and fast flow injection amperometry for the determination of methimazole in pharmaceutical preparations using an unmodified boron-doped diamond electrode.

In this work, an automated flow injection analysis (FIA) connected to a boron-doped diamond electrode (BDDE) was originally developed for the analysis of methimazole in pharmaceutical preparations. At a modification-free BDDE, methimazole was easilly oxidized. For the analysis of the mechanisms occurring at the electrode surface, cyclic voltammetry was employed to evaluate the impact of fundamental experimental parameters, such as pH and scan rate, on the BDDE response. For the quantitative detection, the FIA amperometric approach was constructed and used as a fast and sensitive method. The suggested approach provided a broad linear range of 0.5-50 µmol/L and a low detection limit of 10 nmol/L (signal-to-noise ratio = 3). Furthermore, the BDDE was successfully utilized to quantify methimazole in genuine samples from a variety of medicines, and its performance remained steady after more than 50 tests. The findings of amperometric measurements exhibit excellent repeatability, with relative standard deviations of less than 3.9 and 4.7 % for intra-day and inter-day, respectively. The findings indicated that, compared with traditional approaches, the suggested method has the following advantages: quick analysis time, simplicity, highly sensitive output, and no need for complicated operational processes.

Microfluidic Electrochemical Glucose Biosensor with In Situ Enzyme Immobilization.

The development and characterization of a microfluidic electrochemical glucose biosensor are presented herein. The transducer part is based on thin-film metal electrodes on a glass substrate. The biological recognition element of the biosensor is the pyrroloquinoline quinone-glucose dehydrogenase (PQQ-GdhB) enzyme, selectively in situ immobilized via microcontact printing of a mixed self-assembling monolayer (SAM) on a gold working electrode, while the microfluidic part of the device comprises microchannel and microfluidic connections formed in a polydimethylsiloxane (PDMS) elastomer. The electrode properties throughout all steps of biosensor construction and the biosensor response to glucose concentration and analyte flow rate were characterized by cyclic voltammetry and chronoamperometry. A measurement range of up to 10 mM in glucose concentration with a linear range up to 200 µM was determined. A detection limit of 30 µM in glucose concentration was obtained. Respective biosensor sensitivities of 0.79 nA/µM/mm2 and 0.61 nA/µM/mm2 were estimated with and without a flow at 20 µL/min. The developed approach of in situ enzyme immobilization can find a wide number of applications in the development of microfluidic biosensors, offering a path towards continuous and time-independent detection.

ToF-SIMS Li Depth Profiling of Pure and Methylated Amorphous Silicon Electrodes After Their Partial Lithiation.

Pure (a-Si:H) and methylated [a-Si0.95(CH3)0.05:H] amorphous silicon thin films were analyzed by time-of-flight secondary ion mass spectrometry after partial lithiation. Depth profiling gives insights into the lithiation mechanism of the material, enabling us to study the detailed biphasic process in the first lithiation process. Lithiation induces swelling and roughening of the active layer. In both a-Si:H and a-Si0.95(CH3)0.05:H, no measurable Li diffusion was observed after stopping current-induced lithiation. After applying the same lithiation charges, distinct Li profiles were observed for these two materials. Unlike a-Si:H, the Li concentration drops slowly from the heavily lithiated region to the non-lithiated region in a-Si0.95(CH3)0.05:H. This apparent progressive transition between the lithiated and lithium-free regions is attributed to the presence of nanovoids inside the material. When their concentration is high enough, these nanovoids constitute favorable quasi-percolating paths for lithium during the first lithiation. A specific model was developed to simulate the Li depth profiles, fully supporting this hypothesis.

Physical Vapor Deposition in Solid-State Battery Development: From Materials to Devices.

This review discusses the contribution of physical vapor deposition (PVD) processes to the development of electrochemical energy storage systems with emphasis on solid-state batteries. A brief overview of different PVD technologies and details highlighting the utility of PVD for the fabrication and characterization of individual battery materials are provided. In this context, the key methods that have been developed for the fabrication of solid electrolytes and active electrode materials with well-defined properties are described, and demonstrations of how these techniques facilitate the in-depth understanding of fundamental material properties and interfacial phenomena as well as the development of new materials are provided. Beyond the discussion of single components and interfaces, the progress on the device scale is also presented. State-of-the-art solid-state batteries, both academic and commercial types, are assessed in view of energy and power density as well as long-term stability. Finally, recent efforts to improve the power and energy density through the development of 3D-structured cells and the investigation of bulk cells are discussed.

Development of flexible electrochemical impedance spectroscopy-based biosensing platform for rapid screening of SARS-CoV-2 inhibitors.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters the cells through the binding of its spike protein (S-protein) to the cell surface-expressing angiotensin-converting enzyme 2 (ACE2). Thus, inhibition of S-protein-ACE2 binding may impede SARS-CoV-2 cell entry and attenuate the progression of Coronavirus disease 2019 (COVID-19). In this study, an electrochemical impedance spectroscopy-based biosensing platform consisting of a recombinant ACE2-coated palladium nano-thin-film electrode as the core sensing element was fabricated for the screening of potential inhibitors against S-protein-ACE2 binding. The platform could detect interference of small analytes against S-protein-ACE2 binding at low analyte concentration and small volume (0.1 µg/mL and ~1 µL, estimated total analyte consumption < 4 pg) within 21 min. Thus, a few potential inhibitors of S-protein-ACE2 binding were identified. This includes (2S,3aS,6aS)-1-((S)-N-((S)-1-Carboxy-3-phenylpropyl)alanyl)tetrahydrocyclopenta[b] pyrrole-2-carboxylic acid (ramiprilat) and (2S,3aS,7aS)-1-[(2S)-2-[[(2S)-1-Carboxybutyl]amino]propanoyl]-2,3,3a,4,5,6,7,7a-octahydroindole-2-carboxylic acid (perindoprilat) that reduced the binding affinity of S-protein to ACE2 by 72% and 67%; and SARS-CoV-2 in vitro infectivity to the ACE2-expressing human oral cavity squamous carcinoma cells (OEC-M1) by 36.4 and 20.1%, respectively, compared to the PBS control. These findings demonstrated the usefulness of the developed biosensing platform for the rapid screening of modulators for S-protein-ACE2 binding.

Chemically Roughened, Sputtered Au Films with Trace-Loaded Manganese Oxide for both On-Chip and Off-Chip High Frequency Supercapacitors.

High frequency supercapacitors (HFSCs) are promising in alternating current line filtering and adaptable storage of high-frequency pulse electrical energy. Herein, we report a facile yet integrated-circuit-compatible fabrication of HFSC electrodes by combining chemical roughening of the sputtered metal (Au) films and in situ trace loading of a pseudocapacitive material (MnO x ). The developed electrode fabrication route is versatile for different substrates, and is described with the application paradigms of both on-chip (with Si/SiO2 substrate) and off-chip (without Si/SiO2 substrate, with Ti substrate as an example in this study) HFSCs. With Au/MnO x films on Si/SiO2 substrates as the working electrodes, the derived on-chip HFSC displayed satisfactory performance in high frequency applications (i.e., an areal capacitance of 131.7 µF cm-2, a phase angle of -78°, and a RC time constant of 0.27 ms, at 120 Hz).

Recent Developments of the Solution-Processable and Highly Conductive Polyaniline Composites for Optical and Electrochemical Applications.

Solution-processable conducting polymers (CPs) are an effective means for producing thin-film electrodes with tunable thickness, and excellent electrical, electrochemical, and optical properties. Especially, solution-processable polyaniline (PANI) composites have drawn a great deal of interest due to of their ease of film-forming, high conductivity up to 103 S/cm, excellent redox behaviors, processability, and scalability. In this review, basic principles, fabrication methods, and applications of solution-processable PANI composites will be discussed. In addition, recent researches on the PANI-based electrodes for solar cells (SCs), electrochromic (EC) windows, thermoelectric (TE) materials, supercapacitors, sensors, antennas, electromagnetic interference (EMI) shielding, organic field-effect transistors (OFETs), and anti-corrosion coatings will be discussed. The presented examples in this review will offer new insights in the design and fabrication of high-performance electrodes from the PANI composite solutions for the development of thin-film electrodes for state-of-art applications.

Preparation of Low-Resistance and Residue-free ITO Films for Large-scale 3D Displays.

The large-sized naked-eye three-dimensional (3D) display is a critical device in the real-time topographic survey for deep-sea scientific research. As a core component, the low-impedance transparent conductive indium tin oxide (ITO) thin-film electrode lacks a reliable industrial preparation method. In the 3D display, the grating element with a low-resistance ITO film electrode should have a good binocular parallax to drive the display favorably. However, an increase in the ITO film temperature during deposition may induce its crystallization, and its etching residue may cause a short circuit between the ITO electrodes and abnormal display operation. In this work, we propose a simple and straightforward technique to produce amorphous thin ITO films by controlling the water vapor flow rate during the deposition process. The obtained ITO amorphous thick film (300 nm) can be etched without leaving residues on the display surface, ensuring vivid display performance of the 3D display. A field test employing the 3D display, consisting of a 3D parallax barrier and a two-dimensional (2D) display, does not exhibit a short-circuit phenomenon caused by residues encountered in previous devices. This work makes the 3D display applicable for the real-time topographic survey on the basis of both satisfying the nonetching residue and the decrease of the resistance value.

In Situ Observation of the Insulator-To-Metal Transition and Nonequilibrium Phase Transition for Li1-xCoO2 Films with Preferred (003) Orientation Nanorods.

It is notoriously difficult to distinguish the stoichiometric LiCoO2 (LCO) with a O3-I structure from its lithium defective O3-II phase because of their similar crystal symmetry. Interestingly, moreover, the O3-II phase shows metallic conductivity, whereas the O3-I phase is an electronic insulator. How to effectively reveal the intrinsic mechanism of the conductivity difference and nonequilibrium phase transition induced by the lithium deintercalation is of vital importance for its practical application and development. Based on the developed technology of in situ peak force tunneling atomic force microscopy (PF-TUNA) in liquids, the phase transition from O3-I to O3-II and consequent insulator-to-metal transition of LCO thin-film electrodes with preferred (003) orientation nanorods designed and prepared via magnetron sputtering were observed under an organic electrolyte for the first time in this work. Then, studying the post-mortem LCO thin-film electrode by using ex situ time-dependent XRD and conductive atomic force microscopy, we find the phase relaxation of LCO electrodes after the nonequilibrium deintercalation, further proving the differences of the electronic conductivity and work function between the O3-I and O3-II phases. Moreover, X-ray absorption spectroscopy results indicate that the oxidation of Co ions and the increasing of O 2p-Co 3d hybridization in the O3-II phase lead to electrical conductivity improvement in Li1-xCoO2. Simultaneously, it is found that the nonequilibrium deintercalation at a high charging rate can result in phase-transition hysteresis and the O3-I/O3-II coexistence at the charging end, which is explained well by an ionic blockade model with an antiphase boundary. At last, this work strongly suggests that PF-TUNA can be used to reveal the unconventional phenomena on the solid/liquid interfaces.

Ultrasonic-assisted fabrication of thin-film electrochemical detector of H2O2 based on ferrocene-functionalized silver cluster.

A novel ferrocene-functionalized silver cluster (FcAgCs) has been designed and synthesized with the assistant of ultrasound treatment and fully characterized by single crystal spectroscopy, IR, UV-Vis, XRD, TGA, NMR, CV and elemental analyses. Ultrasound synthesis method facilitates and accelerates synthesis of this amazing structure and plays a vital role in the synthesis of this special cluster. Single-crystal X-ray analysis reveal that the cluster can be described as a cationic [(dppf)2Ag4(CCtBu)2(CH3OH)2]2+ (dppf = 1,1'-bis(diphenylphosphino)ferrocene) species consisted of four rhombic silver atom and two isolated BF4- counter anions. Thermal stability greater than 200 °C and solution CV results show that the title cluster is sufficiently stable and suitable for the fabricating of FcAgCs/ITO thin-films and exploring as electrochemical responding materials. Based on its properties, we use it to prepare thin-films on ITO substrate by spin coating method. Verification of synthesis, thickness, uniformity and stability of the fabricated FcAgCs/ITO thin-films were characterized and confirmed by UV, XRD, SEM and the scotch tape adhesion peel test. Moreover, we use this FcAgCs/ITO thin-film electrode as thin-film electrochemical detector which shows sensitive and quick response in the detection of H2O2.

Comprehensive Understanding of Cathodic and Anodic Polarization Effects on Stability of Nanoscale Oxygen Electrode for Reversible Solid Oxide Cells.

Degradation of oxygen electrode in reversible solid oxide cells operating in both electrolysis and fuel-cell modes is a critical issue that should be tackled. However, origins and mechanisms thereof have been diversely suggested mainly due to the difficulty in precise analysis of microstructural/compositional changes of porous electrode, which is a typical form in solid oxide cells. In this study, we investigate the degradation phenomena of oxygen electrode under electrolysis and fuel-cell long-term operations for 540 h, respectively, using a geometrically well-defined, nanoscale La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) dense film with a thickness of ∼70 nm. Based on assessments of electrochemical properties and analyses of microstructural and compositional changes after long-term operations, we suggest consolidated degradation mechanisms of oxygen electrode, including the phenomena of kinetic demixing/decomposition of LSCF, which is not readily observable in the typical porous-structured electrode.

Study of the Carrier-Aided Thin Film Electrode Array Design for Cochlear Insertion.

The micro-fabricated thin film electrode array (TFEA) has been a promising design for cochlear implants (CIs) because of its cost-effectiveness and fabrication precision. The latest polymer-based cochlear TFEAs have faced difficulties for cochlear insertion due to the lack of structural stiffness. To stiffen the TFEA, dissolvable stiffening materials, TFEAs with different structures, and TFEAs with commercial CIs as carriers have been invested. In this work, the concept of enhancing a Parylene TFEA with Kapton tape as a simpler carrier for cochlear insertion has been proved to be feasible. The bending stiffness of the Kapton-aided TFEA was characterized with an analytical model, a finite element model, and a cantilever bending experiment, respectively. While the Kapton tape increased the bending stiffness of the Parylene TFEA by 10³ times, the 6-µm-thick TFEA with a similar Young's modulus, as a polyimide, in turn significantly increased the bending stiffness of the 170-µm-thick Kapton carrier by 60%. This result indicated that even the TFEA is ultra-flexible and that its bending stiffness should not be neglected in the design or selection of its carrier.

Determination of Trace ZnⅡ, CdⅡ and PbⅡ Metal Ions Using In-situ Bismuth-modified Boron Doped Diamond Electrode / 分析化学

Bismuth modified boron doped diamond (BDD) film electrode was employed for simultaneous determination of trace ZnⅡ,CdⅡand PbⅡby anodic stripping voltammetry.BiⅢwas simultaneously in-situ deposited on bismuth modified boron doped diamond electrode with ZnⅡ,CdⅡ and PbⅡ by pre-concentration.In the presence of BiⅢ,the sensitivity for determination of ZnⅡ,CdⅡ and PbⅡ was remarkably enhanced.Influence factors such as bismuth concentration,boron doped concentrations of BDD electrode,pH,preconcentration potential were investigated and optimized.Under the optimal conditions,the stripping peak currents increased linearly with the increasing concentration of ZnⅡ,CdⅡ and PbⅡ in the range of 10-300 μg/L.The limit of detection was 0.56 μg/L for ZnⅡ,0.32 μg/L for CdⅡand 0.75 μg/L for PbⅡ (S/N=3),respectively.The interference experiments showed that common ions had little influence on the determination except CuⅡ.In addition,the developed electrode displayed a good repeatability.The method was successfully applied to determination of ZnⅡ,CdⅡ and PbⅡ in real water samples with the standard addition recoveries of 92.0%-114.0%.

Amorphous and Crystalline Vanadium Oxides as High-Energy and High-Power Cathodes for Three-Dimensional Thin-Film Lithium Ion Batteries.

Flexible wearable electronics and on-chip energy storage for wireless sensors drive rechargeable batteries toward thin-film lithium ion batteries. To enable more charge storage on a given surface, higher energy density materials are required, while faster energy storage and release can be obtained by going to thinner films. Vanadium oxides have been examined as cathodes in classical and thin-film lithium ion batteries for decades, but amorphous vanadium oxide thin films have been mostly discarded. Here, we investigate the use of atomic layer deposition, which enables electrode deposition on complex three-dimensional (3D) battery architectures, to obtain both amorphous and crystalline VO2 and V2O5, and we evaluate their thin-film cathode performance. Very high volumetric capacities are found, alongside excellent kinetics and good cycling stability. Better kinetics and higher volumetric capacities were observed for the amorphous vanadium oxides compared to their crystalline counterparts. The conformal deposition of these vanadium oxides on silicon micropillar structures is demonstrated. This study shows the promising potential of these atomic layer deposited vanadium oxides as cathodes for 3D all-solid-state thin-film lithium ion batteries.

Operando Measurement of Solid Electrolyte Interphase Formation at Working Electrode of Li-Ion Battery by Time-Slicing Neutron Reflectometry.

We report the first operando measurement of solid electrolyte interphase (SEI) formation at an electrode using in situ neutron reflectometry. The results revealed the growth of the SEI and intercalation of ions during the charge reaction. Furthermore, we propose a way of evaluating the charge used for the SEI formation.

Fabrication and Characterization of Thin Film Nickel Hydroxide Electrodes for Micropower Applications.

The utilization of micropower sources is attractive in portable microfluidic devices where only low-power densities and energy contents are required. In this work, we report on the microfabrication of patterned α-Ni(OH)2 films on glass substrates which can be used for rechargeable microbatteries as well as for microcapacitors. A multilayer deposition technique is developed based on e-beam evaporation, ultraviolet lithography, and electroplating/electrodeposition which creates thin-film electrodes that are patterned with arrays of micropillars. The morphology and the structure of the patterned electrode films are characterized by employing field emission scanning electron microscopy. The chemical (elemental) composition is investigated by using X-ray diffraction and X-ray photoelectron spectroscopy. Finally, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge measurements are used to evaluate the electrochemical performance of the patterned thin film electrodes compared to patternless electrodes. We observe that patterning of the electrodes results in significantly improved stability and, thus, longer endurance while good electrochemical performance is maintained.