Studying batteries in real time is essential for understanding their operation and degradation mechanisms. Operando methods such as X-ray diffraction, NMR, and electron microscopy provide detailed insights but are costly, complex, and require specialized cell designs, making them impractical for long-term cycling or screening. Here, we propose using operando diffuse reflectance spectroscopy (DRS) to probe battery electrodes as they charge and discharge. This technique measures subtle changes in the reflectance spectrum of battery electrodes caused by electronic structure changes during cycling. By correlating these optical property changes with the state-of-charge of the battery, we can reconstruct a 'second view' of the electrochemistry of the battery. We show that DRS can be used to determine heterogeneity in state-of-charge, study solid state lithium-ion diffusion, uncover the origin of first cycle capacity losses, and study surface limited behaviour. We apply operando DRS to a wide variety of battery materials to show that the proposed method enables the extraction of information that previously was only accessible using methods that are orders of magnitude more expensive.
Electrocatalytic reactions often involve several steps and intermediates, along with changes in the catalyst structure and chemistry under reaction conditions, making their mechanistic understanding very challenging. As a way to extract maximum information about the kinetics, temperature-dependent electrochemistry enables access to the apparent activation energy and pre-exponential factor as a function of the electrochemical bias. Recently, many reactions were shown to exhibit rich structures in their bias-dependent activation parameters, structures which cannot be accounted for by the traditional, single-step Butler-Volmer theory. Here, we study the overpotential-dependent activation parameters of a 2-step microkinetic model featuring an electrochemical adsorption followed by a chemical recombination step. We show that the electrochemical bias drives transitions across several kinetic regimes where the degree of rate control of each step varies. A key finding is that the bias dependent Arrhenius signatures constrain the underlying phase space of intermediate binding and activation enthalpies, even for such a seemingly simple model. From the close fit of our model with our experiments on the oxygen reduction reaction, we find that for a wide overpotential range, one kinetically relevant intermediate - and thus two partially rate determining steps - are controlling the kinetics on platinum and ruthenium nanoparticles. From the fits, we extract the corresponding binding and activation energies along with bias-dependent coverage. We argue that combining temperature dependent electrochemistry with minimalistic micro-kinetic models allows a direct comparison with DFT calculations and operando spectroscopy measurements.
Secondary-sphere control is leveraged to boost cobalt corrole oxygen-evolution catalysis. We install a pendant benzoyl-urea unit on a corrole scaffold to position a hydrogen-bond donor above the metal site. The ligand is obtained via an isolable N-benzoyl-dicyclohexylurea intermediate, converted to the FB corrole, and metalated to Co(III); a pentafluorophenyl analog lacking the urea serves as control. X-ray/time-dependent density functional theory (TD-DFT) show axial pyridine ligation lifts the pendant carbonyl toward the catalytic pocket with reduced saddling. In MeCN, CV features reversible Co (III/II) couples at -0.62 V (urea) and -0.52 V (control) versus FeCp2 +/0, plus ligand-centered oxidations; spectro-electrochemistry/EPR (g iso = 1.9986) confirm a corrole-radical [CoIII(corrole•2-)(py)2]+. Water addition unveils catalytic waves ~1.12V(urea) and 1.21 V (control), versus FeCp2 +/0. Under CPE (1.78 V, vs. Ag/AgCl), the urea-bearing complex delivers 83.9% Faradaic efficiency, TOF 1.19 s-1 (vs. 59.6%, 0.47 s-1 for control); a KIE = 1.3 implicates PCET. DFT supports WNA at a Co-oxyl, [CoIII(corrole•2-)(O•-)(py)], with the pendant carbonyl H-bonding to the incoming H2O (O···H = 1.71 Å), thereby lowering the activation barrier relative to a truncated analog. These results establish benzoyl-urea secondary-sphere engineering as a concise, general strategy to enhance charge utilization and O-O bond formation in cobalt corrole oxygen evolution reaction catalysis.
Co-electrolysis of CO2 and nitrate offers a sustainable route to organic amines but suffers from a kinetic mismatch between C-N coupling and hydrogenation steps under static conditions. This mismatch is challenging to address through conventional catalyst design and therefore limits both efficiency and selectivity. Here, we introduce a pulsed strategy that orthogonally decouples these steps by alternating optimized potentials. Pulses at less reductive potentials suppress hydrogenation and thus favor oxime formation, whereas more reductive potentials promote hydrogenation to amines. Using cobalt phthalocyanines, this approach triples the reaction rate and doubles the selectivity for methylamine compared to static methods, and also enables the formation of higher amines. In situ studies and density functional theory calculations reveal that a more reductive pulse accelerates hydrogenation, promoting a multielectron cascade through intermediates. Retrosynthetic analysis and product distribution trends further support a sequential coupling-hydrogenation pathway from methylhydroxylamine/methylamine to higher amines. This work offers a framework for steering multistep C-N bond formation and shows how dynamic electrochemistry can turn waste-derived carbon and nitrogen into valuable products.
During the past decade, emerging studies using electrochemistry and nanoscale imaging have demonstrated that partial exocytotic release is prevailing in neuroendocrine cell models. However, due to complicated structure and culture process, few studies have been carried out using neurons, especially human neurons. Here, dopamine (DA) release from individual vesicles and DA content stored within vesicles were quantified from induced pluripotent stem cell-derived DA neurons with electrochemical techniques. The results indicate that around 61% of the total vesicular DA content is released from these neurons during exocytosis. The vesicular content quantified in DA neurons is significantly higher than that in undifferentiated neural progenitor cells, owing to the increased appearance of dense-core vesicles that are able to store more DA molecules than the clear vesicles. When the neurons are differentiated with BAY-K8644, which stimulates neuronal maturation as well as DA release, the release fraction rises to 91%. The use of BAY-K8644 can be considered as chronic stimulation and leads to similar effects on exocytosis as repetitive stimulation, which triggers short-term plasticity. This study demonstrates partial release in DA transmission in human neurons and provides a link between neuronal maturation and the formation of plasticity. Furthermore, this work suggests that the fraction of release in exocytosis at human neurons may be a factor in determining plasticity.
Precise cancer diagnosis boosts survival rates, but liquid biopsy struggles to identify the tumor histotype from a single blood draw. We propose a Homologous Adhesion Identification (HAI) method that enables specific recognition between tumor extracellular vesicles (tEVs) and homologous tumor cell membrane-coated silica microsphere (TMS). The functionalized TMS exhibits an effective HAI property with high binding strength, speed, and biospecificity between tEVs and TMS, and their similar membrane structures facilitate efficient, rapid, and selective cancer diagnosis. The HAI method can effectively distinguish extracellular vesicles from normal and tumor sources and from different tumor histotypes and subtypes using just 10 μL of serum. It is versatile with replaceable cell membranes and lanthanide ions and supports diverse detection techniques like fluorescence, ultraviolet-visible spectrophotometry, electrochemistry, and electrochemiluminescence (ECL), with a minimum detection limit of 10 tEVs/mL. It accurately differentiates healthy and tumor blood samples in five animal models and shows significant potential for rapid cancer classification and therapeutic monitoring in clinical serum testing, both pre- and postoperatively.
Norepinephrine (NE) in the peripheral nervous system plays crucial roles in regulating peripheral organs in health and disease. However, the spatiotemporal dynamics of sympathetic NE release and its underlying mechanisms remain poorly characterized due to technical challenges. Here, we developed and validated a Slice ElectroChemistry (SEC) method to record sympathetic NE release in heart slices with combined super-resolution and high sensitivity at 1 μm × 1 ms × 1 nM as in patch-clamp recordings. By using the SEC method, we revealed the increased NE release, impaired NE reuptake, increased releasable NE-vesicle pool, and impaired vesicle recycling of sympathetic nerves in the heart of transverse aortic constriction-induced heart failure (HF) mouse model, and defined the increased expression of Cav2.2 calcium channel as a central mechanism mediating the facilitation of NE release and thus the pathogenesis of HF, clarifying a longstanding puzzle about the kinetic changes of cardiac sympathetic NE release in HF. Beyond the heart, SEC enables NE release recording in other peripheral organs and human tissues, providing a robust toolset to investigate sympathetic NE dynamics across diverse pathophysiological conditions.
Calcium-ion batteries (CIBs) offer several advantages. CIBs are viable alternatives to lithium-based battery systems owing to the natural abundance, low cost, and high volumetric capacity of calcium. However, their development has been severely constrained by electrolyte instability and water sensitivity. We conducted a systematic examination of Ca(ClO4)2 and Ca(PF6)2 electrolytes, focusing on low-cost salt production, solvent selection, and stringent dehydration procedures. Acetonitrile (ACN) was the ideal solvent for high salt solubility and reversible Ca2+ electrochemistry, while carbonate solvents failed rapidly. We found that even a small amount of moisture in the electrolyte significantly affected the electrochemical performance. This study improved the dehydration process by using 3 Å molecular sieve (MS3A) and vacuum drying to reduce moisture to ppm levels, stabilizing the electrolyte. Prussian blue (PB) half cells exhibited reversible capacities of up to ≈95 mAh g-1, whereas PB-hard carbon full cells utilizing dried Ca(ClO4)2 showed stable cycling over 240 cycles with a Coulombic efficiency of ≈99% and capacity loss of only ≈17%. This study establishes a moisture-controlled electrolyte as a critical enabler for practical CIBs.
Catechol offers switchable adhesion in response to electrochemical redox reaction. However, electrochemistry requires water for effective proton transport, but water weakens adhesive performance. Here, we incorporate proton and electron conducting elements (sulfonic acid-containing monomer and multiwalled carbon nanotube, respectively) into a water-free catechol-based adhesive to create a high-strength adhesive that is also susceptible to electrochemical control. These additions increase the proton and electrical conductivity by over 100-fold. The adhesive also exhibits elevated lap shear adhesion strength (4.6 MPa) to metal substrates and outperforms a commercial epoxy glue. Under mild electrical stimulation (9 V), the adhesive strength decreases by over 90%. X-ray photon spectroscopy confirms the deactivation of the adhesive is achieved by catechol oxidation to its poorly adhesive quinone form. When the adhesive is used to create two adjacent adhesive joints connected by a single metallic substrate, the adhesive can be selectively deactivated without affecting neighboring joint. These results present a promising approach for switchable adhesives with high adhesive performance and precise electrical control.
Single-atom nanozymes (SANs) with atomically dispersed metal sites show great potential in small biomolecule detection. This review first summarizes SAN synthesis (wet chemistry, atomic layer deposition, etc.), structural features (tunable coordination, metal-carrier interactions), and catalytic mechanisms (synergistic effects, d-band modulation). Afterwards, this review focuses on the applications of SANs in detecting small biomolecules, including glucose, glutathione, uric acid, ascorbic acid, hydrogen peroxide, and dopamine via colorimetry, fluorescence, and electrochemistry. Challenges such as matrix interference and stability, along with future directions in flexible electronics and clinical translation, are discussed, aiming to advance SAN-based detection technologies.
Ruthenium(II) catalysis is characterized by a remarkable diversity in C-H activation; however, compared to other transition metals, enantioselective C-H activations continue to be underdeveloped. Meanwhile, organic electrosynthesis has attracted considerable attention in recent years as a sustainable alternative to traditional redox approaches. Herein, we disclose an unprecedented electrochemistry-enabled ruthenium(II)-catalyzed enantioselective C-H activation strategy to provide versatile access to atroposelective indoles as well as chiral spiroazoles. This approach combines the redox flexibility of ruthenium with the sustainable nature of molecular electrosynthesis, delivering the desired products in high chemical yields with excellent enantioselectivities, thereby paving the way for sustainable asymmetric syntheses.
The rational design of electrode materials (e.g., electrocatalysts) requires nanoscale insights into surface structure-activity relationships, yet such understanding remains incomplete and is generally out-of-reach with conventional macroscopic electrochemical characterization. In this work, scanning electrochemical cell microscopy (SECCM) is employed to directly compare inner- and outer-sphere redox activity on bilayer molybdenum disulfide (MoS2) crystals. Using the hydrogen evolution reaction (HER) as an inner-sphere benchmark and [Ru-(NH3)6]3+/2+ as a model outer-sphere probe, contrasting layer-dependent electrochemical behavior is observed on bilayer 3R MoS2. High-resolution activity maps reveal the expected attenuation of HER kinetics with increasing layer thickness, attributable to hindered through-plane conductivity and increased electron tunnelling barriers, alongside nanoscale "hotspots" consistent with defect-mediated activity. In stark contrast, the [Ru-(NH3)6]3+/2+ couple is more facile and electrochemically reversible on the upper layer of bilayer 3R MoS2, despite increased electron tunnelling distances. This unexpected response highlights the influence of interfacial electronic structure (e.g., Fermi level pinning and screening effects) and demonstrates that outer-sphere redox mediators can yield misleading indications of "metal-like" behavior for 2D semiconductors. This correlative multimicroscopic approach (i.e., SECCM combined with colocated conductive atomic force microscopy and scanning electron microscopy) provides insight into layer-dependent electrochemistry in 2D semiconductors and underscores the need for caution when employing conventional redox probes as proxies for conductivity or redox activity.
Electrochemiluminescence (ECL) imaging has emerged as a highly sensitive and spatially resolved bioanalytical technique that bridges electrochemical control and optical microscopy. With its unique surface-confined emission, minimal background noise, and tunable activation, ECL imaging offers distinct advantages over fluorescence and chemiluminescence, especially for cellular and single-particle analysis. In this review, advanced strategies and wireless, multiplexed, and high-throughput bioimaging platforms, such as bipolar electrochemistry, single-electrode electrochemical system, and multielectrode array are summarized. Applications of ECL imaging methods in the single-cell analysis, nanoparticle electrocatalysis studies, intracellular and in vivo detection, and high-resolution bioassays are described in detail. This review has comprehensively outlined recent progress in these advanced technologies and presenting some emerging tools such as miniaturized devices, wireless energy transmission, and next-generation materials driving the transformation of ECL imaging into a robust platform for diagnostics and research. This work has not only summarized past progress but also explored future breakthroughs in precision diagnostics and electrochemical microscopy.
Knowledge of the reaction rate constants can be vital in understanding electrochemical reaction mechanisms and their rate-determining processes. Although first-principles methods, such as density functional theory (DFT), provide valuable insight into reaction free energies and rate constants, they commonly use idealized assumptions. As a different approach, this study demonstrates the estimation of rate constants from electrochemical data. Specifically, this study estimates rate constants from electrochemical impedance spectroscopy (EIS) data of the oxygen evolution reaction (OER) with a hematite Fe2O3 anode often used in photoelectrochemical cells. Unlike the common approach of equivalent circuit fitting with resistances and capacitances, the electrochemistry of the OER in this work is represented by a microkinetic model and physicochemical quantities. The estimated rate constants directly correspond to the OER reaction steps, and a single set of rate constants is obtained that is optimized for multiple potentials simultaneously. The estimation is conducted using maximum likelihood estimation. The effectiveness of the estimation method is shown using synthetic measurements first; intermediate species coverages are simulated as well. Then, the rate constants are estimated directly from experimental EIS measurements. Though accuracy is currently limited due to the model that does not account for all processes at the interface, such as, for example, diffusive transport, the estimated rate constants do represent the experimental interface and are perfectly suited for kinetic analysis and systematic parameter studies of the electrochemical system. Additionally, this approach enables analyses of differences between electrode materials, validation of models, and prediction of electrochemical data of different material systems, which is time-consuming and costly to obtain experimentally. This research demonstrates how combining potential- and frequency-dependent EIS experiments with microkinetic modeling enables the estimation of reaction rates and intermediate species coverages, aiding in identifying reaction mechanisms directly from experiments.
Deep eutectic solvents (DESs) are 21st century solvents composed entirely of hydrogen bond donors and acceptors, which form a eutectic solvent having a significantly lower melting point than its individual components. Due to their tunable nature, DESs are widely employed for applications in electrochemistry, nanotechnology, catalysis and synthesis but their intrinsic electron transfer behaviour is largely unexplored. In order to characterize electron transfer in DESs, steady state reductive emission quenching measurements were performed using tris(2,2'-bipyridine)ruthenium(II), [Ru(bpy)3]2+, with a series of quenchers in several different volumetric compositions of ethaline (choline chloride:ethylene glycol) and water. Using Stern-Volmer analysis, rate constant (kq) values for excited state quenching were calculated and compared with diffusion limited rate constant (kD) data. Finally, the electron transfer data were further analyzed by fitting to Rehm-Weller and Marcus theory models in order to provide a theoretical framework for understanding and predicting electron transfer kinetics.
The practical deployment of rechargeable aluminum-ion batteries (AIBs) is hindered by the absence of electrolytes that concurrently offer low cost, efficient ion transport, and stable interfacial electrochemistry. While hydrated deep eutectic electrolytes (HEEs) present a promising avenue, their advancement has been limited by high viscosity and poorly controlled interfacial reactions. This work establishing anion engineering, rather than solely focusing on ligand modulation, as a critical yet previously underappreciated design strategy. We systematically elucidate how the identity of the anion governs the coordination architecture within an ethylene glycol (EG)-based HEE. Crucially, the NO3 - anion induces the formation of a homogeneous, inner‑sphere Al3+ solvation complex, which simultaneously reduces the dynamic viscosity, improves interfacial wettability, and elevates the cathodic stability limit. This tailored solvation structure lowers the desolvation energy barrier. As a result, the NO3 -‑HEE enables exceptional aluminum anode reversibility, evidenced by a high exchange current density and stable, dendrite‑free plating/stripping over 400 h. Full cells coupled with a CuHCF cathode deliver a specific capacity of ∼123 mAh·g-1 and demonstrate outstanding capacity retention over 500 cycles. This study provides a foundational anion‑centric design principle for next‑generation, high‑performance eutectic electrolytes.
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Herein, the electrochemical SRN1 reaction between various thianthrenium salts and β-dicarbonyl compounds and analogues was reported. This rare example of electrochemical functionalization of thianthrenium salts allowed the formation of the arylated products in moderate to good yields. The reaction was applied to various thianthrenium salts having electron withdrawing groups and β-dicarbonyl compounds. The study of the reaction mechanism confirmed a reduction of the electro-poor thianthrenium salts followed by their reaction with the putative enolate species as formal nucleophile, according to a SRN1 mechanism.
We herein propose a smart tripedal DNA walking nanomachine based on the nanostructure transition of DNA triangular prism (TPDNA), which performs satisfactorily for highly sensitive analysis of miRNA biomarkers. Split DNAzyme sequences are integrated in the TPDNA with suppressed activity. With target sequence-mediated catalytic hairpin assembly, TPDNA structural transformation relives the blockage and the triple active DNAzyme units function as the driver of the DNA nanomachine. In addition, the triplex-forming track on the surface of electrode suffers the cleavage reaction and the declined signal is utilized to indicate the level of target miRNA. The track can be further regenerated by simply changing pH conditions, improving the stability and reducing the cost. Excellent performances are well validated and the feasibilities in complex biological samples are also demonstrated. This strategy integrates the advantages of DNA dynamic nanomachine and DNA structural transition, which holds great potential for nucleic acid-based studies and clinical diagnostics.
Background/Objectives: Modern dentistry focuses on the ongoing development of digital alternative technologies and the study of the properties of these innovative materials is deemed essential. Therefore, the objectives of this study were to evaluate the optical and surface characteristics of six computer-aided design/Computer-Aided Manufacturing (CAD-CAM) dental materials, both subtractive and additive, in relation to in vitro degradation. Methods: CAD-CAM dental materials, subtractively processed (Vita Enamic, Cerasmart, Brilliant and Tetric) and additively manufactured (Saremco Crowntec and Voco C&B), were prepared to standard dimensions of 14 × 10 × 1 mm, with baseline measurements taken prior to, and after, the degradation procedures, consisting of immersion in an ADA-recommended staining broth, artificial aging (thermocycling), and the combined effects of staining and in vitro aging. Additionally, two different surface treatments were investigated (polished and glazed). Results: The poorest color stability was observed for Tetric glazed specimens (mean value 25.585) subjected to staining, while the best performance was recorded for Brilliant polished Control (average value of 0.781). The staining procedure produced the most pronounced color changes. Surface treatment did not significantly affect color stability, and surface roughness was not influenced by either the degradation method or the surface treatment (p > 0.05). Atomic Force Microscopy (AFM) evaluation revealed superior performance of the glazed surfaces, characterized by lower nanoroughness values compared with polished surfaces and a smoother surface appearance. Conclusions: The staining potential of staining broth was demonstrated in this study, with the highest values recorded after the staining procedures. In addition, the influence of artificial aging alone and artificial aging combined with staining was investigated, providing relevant results for a better clinical approach. Moreover, surface treatment demonstrated reliability and therefore clinical applicability.