Potential Cycling Research Articles

Development of electrocatalytic hybrid film based on conducting polypyrrole–heteropolyanion

The investigation focused on integrating heteropolyanions (HPAs) into a polymeric matrix of polypyrrole (PPy), aiming to achieve effective immobilisation for potential electrocatalytic applications. Specifically, the successful immobilization of a Dawson-type mixed addenda HPA, α2 – K8[P2W17V4+O62].10H2O, within conductive PPy films was achieved. These [P2W17V4+O62]-doped PPy films exhibited robust stability at both pH 2 and pH 7 during continuous potential cycling involving the V5+/4+ redox process. However, it was noted that in the negative potential range leading to polymer backbone reduction, the HPA tended to leach out from the film. In terms of catalytic assessments, the [P2W17V4+O62]-dopped PPy films displayed noteworthy electrocatalytic performance in the oxidation of ascorbic acid. Notably, they demonstrated a sensitivity of 8.18 (+/-0.15) μA mM−1 and a limit of detection (LOD) of 1.65 mM at pH 2.0. Furthermore, under neutral conditions, the films exhibited a sensitivity of 6.97 (+/-0.30) μA mM−1 and a LOD of 4.24 mM. Further, endeavours were made to immobilise alternative variations of HPAs, specifically, the crown HPA, K28Li5H7P8W48O184·92H2O, and Cu2+ substituted Krebs HPA, KxNa(10-x)Bi2W20Cu2O70(H2O)6·30H2O (with × ranging from 1 to 10), into PPy films. Initial findings from these attempts are also briefly discussed in this study.

Highly Electroactive Frozen-State Polymerized Polypyrrole Nanostructures for Flexible Supercapacitors.

The polymerization of pyrrole in the frozen state with the presence of organic dyes (methyl orange (MO) and Acid Blue 25 (AB)) has proven to produce polypyrrole (PPy) nanostructures. Herein, we explore the electrochemical properties of PPy prepared under frozen-state conditions (-24 °C) with and without the presence of organic dyes. The electroactivity of PPy prepared with MO and AB significantly increased in all electrolytic media with a capacitance higher than this of the PPy prepared at room temperature. The highest capacitance (1914 F g-1) was obtained for PPy-MO in 0.2 M HCl solution. The impedance spectra of PPy showed a decrease in charge transfer resistance when the dyes were present. This indicates a conductivity increase of PPy. Improved electrochemical stability was observed for PPy, PPy-MO, and PPy-AB prepared at -24 °C, wherein a steady gain of capacitance was maintained during 5000 potential cycling. In addition, a PPy-based supercapacitor device was fabricated to demonstrate the energy storage characteristics of PPy, where it showed good capacitive behavior and stability. Overall, frozen-state polymerized PPy posed an impressive capacitive performance for flexible supercapacitors.

The Impact of Repeating COVID-19 Rapid Antigen Tests on Prevalence Boundary Performance and Missed Diagnoses.

A prevalence boundary (PB) marks the point in prevalence in which the false omission rate, RFO = FN/(TN + FN), exceeds the tolerance limit for missed diagnoses. The objectives were to mathematically analyze rapid antigen test (RAgT) performance, determine why PBs are breeched, and evaluate the merits of testing three times over five days, now required by the US Food and Drug Administration for asymptomatic persons. Equations were derived to compare test performance patterns, calculate PBs, and perform recursive computations. An independent July 2023 FDA-NIH-university-commercial evaluation of RAgTs provided performance data used in theoretical calculations. Tiered sensitivity/specificity comprise the following: tier (1) 90%, 95%; tier (2) 95%, 97.5%; and tier (3) 100%, ≥99%. Repeating a T2 test improves the PB from 44.6% to 95.2% (RFO 5%). In the FDA-NIH-university-commercial evaluation, RAgTs generated a sensitivity of 34.4%, which improved to 55.3% when repeated, and then improved to 68.5% with the third test. With RFO = 5%, PBs are 7.37/10.46/14.22%, respectively. PB analysis suggests that RAgTs should achieve a clinically proven sensitivity of 91.0-91.4%. When prevalence exceeds PBs, missed diagnoses can perpetuate virus transmission. Repeating low-sensitivity RAgTs delays diagnosis. In homes, high-risk settings, and hotspots, PB breaches may prolong contagion, defeat mitigation, facilitate new variants, and transform outbreaks into endemic disease. Molecular diagnostics can help avoid these potential vicious cycles.

The cycle effect quantified: reduced tumour uptake in subsequent cycles of [177Lu]Lu-HA-DOTATATE during peptide receptor radionuclide therapy.

Clear evidence regarding the effect of reduced tumour accumulation in later peptide receptor radionuclide therapy (PRRT) cycles is lacking. Therefore, we aimed to quantify potential cycle effects for patients treated with [177Lu]Lu-HA-DOTATATE using a population pharmacokinetic (PK) modelling approach. A population PK model was developed using imaging data from 48 patients who received multiple cycles of [177Lu]Lu-HA-DOTATATE. The five-compartment model included a central, kidney, spleen, tumour and lumped rest compartment. Tumour volume and continued use of long-acting somatostatin analogues (SSAs) were tested as covariates in the model. In addition, the presence of a cycle effect was evaluated by relating the uptake rate in a specific cycle as a fraction of the (tumour or organ) uptake rate in the first cycle. The final PK model adequately captured observed radioactivity accumulation in kidney, spleen and tumour. A higher tumour volume was identified to increase the tumour uptake rate, where a twofold increase in tumour volume resulted in a 2.3-fold higher uptake rate. Also, continued use of long-acting SSAs significantly reduced the spleen uptake rate (68.4% uptake compared to SSA withdrawal (10.5% RSE)). Lastly, a cycle effect was significantly identified, where tumour uptake rate decreased to 86.9% (5.3% RSE) in the second cycle and even further to 79.7% (5.6% RSE) and 77.6% (6.2% RSE) in the third and fourth cycle, respectively, compared to cycle one. Using a population PK modelling approach, the cycle effect of reduced tumour uptake in subsequent PRRT cycles was quantified. Our findings implied that downregulation of target receptors is probably not the major cause of the cycle effect, due to a plateau in the decrease of tumour uptake in the fourth cycle.

Effects of Catalyst Ink Storage on Polymer Electrolyte Fuel Cells

The shelf-life of catalyst ink for fabricating polymer electrolyte fuel cells (PEFCs) is relevant for large-scale manufacturing with unforeseen production stops. In this study, the storage effects on the physicochemical characteristics of catalyst ink (Pt/C, Nafion, 2-propanol, water) and subsequently manufactured catalyst layers are investigated. Sedimentation analysis showed that catalyst particles are not fully stabilized by charge interaction induced by Nafion. Acetone was found to be an oxidation product, even in freshly prepared ink with platinum catalyzing the reaction. Rotating disk electrode analysis revealed that the electrochemically active surface area is, overall, minimally increased by storage, and the selectivity towards water formation (4-electron pathway) is unharmed within the first 48 h of storage. MEAs prepared from stored ink reach almost the same current density level after conditioning via potential cycling. The open-circuit voltage (OCV) increases due to increased catalyst availability. Scanning electron microscopy and mercury intrusion porosimetry showed that with increasing acetone content, the pore structure becomes finer, with a higher specific surface area. Electrochemical impedance spectroscopy revealed that this results in a more hindered mass transfer but lowered charge transfer resistance. The MEA with the highest OCV and power output and the lowest overall cell resistance was fabricated from catalyst ink stored for a duration of four weeks.

Electronic and Geometric Effects Endow PtRh Jagged Nanowires with Superior Ethanol Oxidation Catalysis.

Complete ethanol oxidation reaction (EOR) in C1 pathway with 12 transferred electrons is highly desirable yet challenging in direct ethanol fuel cells. Herein, PtRh jagged nanowires synthesized via a simple wet-chemical approach exhibit exceptional EOR mass activity of 1.63 A mgPt-1 and specific activity of 4.07mA cm-2 , 3.62-fold and 4.28-folds increments relative to Pt/C, respectively. High proportions of 69.33% and 73.42% of initial activity are also retained after chronoamperometric test (80000 s) and 1500 consecutive potential cycles, respectively. More importantly, it is found that PtRh jagged nanowires possess superb anti-CO poisoning capability. Combining X-ray absorption spectroscopy, X-ray photoelectron spectroscopy as well as density functional theory calculations unveil that the remarkable catalytic activity and CO tolerance stem from both the Rh-induced electronic effect and geometric effect (manifested by shortened Pt─Pt bond length and shrinkage of lattice constants), which facilitates EOR catalysis in C1 pathway and improves reaction kinetics by reducing energy barriers of rate-determining steps (such as *CO → *COOH). The C1 pathway efficiency of PtRh jagged nanowires is further verified by the high intensity of CO2 relative to CH3 COOH/CH3 CHO in infrared reflection absorption spectroscopy.

Explaining the interplay of value creation and value appropriation in strategic alliances: A developmental perspective

AbstractHow firms respectively create and appropriate value by means of alliances are questions that management scholars have considered for several decades. Scholars have identified various factors underlying how alliances create value and how partner firms appropriate such value, respectively. Fewer studies have dealt with how both issues relate, and fewer yet have examined the interplay between value creation and value appropriation as an alliance develops. The purpose of this paper is to organize the extant literature through a theoretically coherent developmental framework that informs research on value creation and value appropriation as distinct but inter‐related phenomena. A systematic review of 234 articles reveals factors associated with value creation, factors driving value appropriation, and, especially, interplay factors that explain potential cycles of value creation and value appropriation within an alliance. We also identify some important themes and theoretical directions for future research. This study thus contributes to alliance research by (1) developing a structured framework that explains not only the respective drivers of value creation and value appropriation, but also how they interplay in alliances; (2) explicating theoretically the specific factors that explain the interplay of value creation and value appropriation in cycles of alliance adaptation; and (3) developing recommendations for the further development of theory, especially for these interplay effects.

A catalase enzyme biosensor for hydrogen peroxide at a poly(safranine T)-ternary deep eutectic solvent and carbon nanotube modified electrode

A new electrochemical enzyme biosensor has been developed to monitor hydrogen peroxide. The sensor uses a multiwalled carbon nanotube modified glassy carbon electrode covered by a poly(safranine T) polymer film prepared by potential cycling electropolymerization in ternary deep eutectic solvent (DES), prepared from choline chloride (ChCl), ethylene glycol (EG) plus malonic acid (MA) or lactic acid (LA) with composition optimization. It is shown that this leads to greater polymer growth and improved film properties compared to binary DES; the process was monitored by an electrochemical quartz crystal microbalance. The best ternary DES composition was found to be 16 % ChCl:MA / 84 % ChCl:EG. Electrochemical characterisation was done by cyclic voltammetry and electrochemical impedance spectroscopy, and the morphology of the synthesized polymer films was examined by scanning electron microscopy. Catalase enzyme was immobilized on the modified electrode and the enzyme biosensor used for measurement of hydrogen peroxide, with a very low detection limit of 34 nM. The selectivity was found to be excellent in relation to common interferents and the biosensor showed very good recovery in peroxide measurements in commercial samples.

Deterministic factors modulating assembly of groundwater microbial community in a nitrogen-contaminated and hydraulically-connected river-lake-floodplain ecosystem

The river-lake-floodplain system (RLFS) undergoes intensive surface-groundwater mass and energy exchanges. Some freshwater lakes are groundwater flow-through systems, serving as sinks for nitrogen (N) entering the lake. Despite the threat of cross-nitrogen contamination, the assembly of the microbial communities in the RLFS was poorly understood. Herein, the distribution, co-occurrence, and assembly pattern of microbial community were investigated in a nitrogen-contaminated and hydraulically-connected RLFS. The results showed that nitrate was widely distributed with greater accumulation on the south than on the north side, and ammonia was accumulated in the groundwater discharge area (estuary and lakeshore). The heterotrophic nitrifying bacteria and aerobic denitrifying bacteria were distributed across the entire area. In estuary and lakeshore with low levels of oxidation-reduction potential (ORP) and high levels of total organic carbon (TOC) and ammonia, dissimilatory nitrate reduction to ammonium (DNRA) bacteria were enriched. The bacterial community had close cooperative relationships, and keystone taxa harbored nitrate reduction potentials. Combined with multivariable statistics and self-organizing map (SOM) results, ammonia, TOC, and ORP acted as drivers in the spatial evolution of the bacterial community, coincidence with the predominant deterministic processes and unique niche breadth for microbial assembly. This study provides novel insight into the traits and assembly of bacterial communities and potential nitrogen cycling capacities in RLFS groundwater.

Preparation, characterization, and Co-delivery of cisplatin and doxorubicin-loaded liposomes to enhance anticancer Activities

Ovarian cancer stands as a leading cause of cancer-related deaths among women globally. This malignancy has hindered successful treatment attempts due to its inherent resistance to chemotherapy agents. The utilization of cisplatin and doxorubicin-loaded liposomes emerges as a strategically advantageous approach in the realm of biomedical applications. This strategy holds promise for augmenting drug efficacy, mitigating toxicity, refining pharmacokinetics, and facilitating versatile drug delivery while accommodating combination therapies. In pursuit of scholarly investigations, the eminent databases, including PubMed/MEDLINE, ScienceDirect, Scopus, and Google Scholar, were meticulously scrutinized. Within this study, a nano-liposomal formulation was meticulously designed to serve as a co-delivery system. This system was optimized by varying lipid concentrations, hydration time, and DSPC: cholesterol molar ratios to efficiently encapsulate and load doxorubicin (DOX) and cisplatin (CIS) to overcome drug resistance problems. The Lipo (CIS + DOX) formulation underwent rigorous characterization including dimensions, entrapment efficiencies and drug release kinetics. Notably, the entrapment efficiency of cisplatin and doxorubicin loaded liposomal nanoparticles was an impressive 85.29 ± 1.45 % and 73.62 ± 1.70 %, respectively. Furthermore, Lipo (CIS + DOX) drug release kinetics exhibited pH-dependent properties, with lower drug release rates at physiological pH (7.4) than acidic (pH 5.4). Subsequent cytotoxicity assays revealed the enhanced biocompatibility of dual-drug liposomes with HFF cells compared to free drug combinations. Impressively, CIS and DOX-loaded liposomes induced significant cytotoxicity against A2780 in comparison to free drugs and combinatorial free drugs. Furthermore, the CIS and DOX-loaded liposome showed induced apoptotic potential and cell cycle arrest in A2780 compared to CIS, DOX, and their combination (CIS + DOX). Combining CIS and DOX via liposomal nanoparticles introduces a promising therapeutic avenue for addressing ovarian cancer. These nano-scale carriers hold the potential for attenuating the untoward effects of singular drugs and their attendant toxicities.

Design, synthesis and anticancer evaluation of polymethoxy aurones as potential cell cycle inhibitors

BackgroundCancer is the most fatal disease in humans and the aberrant activity of various cell cycle proteins results in uncontrolled tumor cell proliferation, thus, regulating the cell cycle is an attractive target in cancer therapy. ObjectivesAurone is a naturally occurring active compound with a wide range of biological activities, of which 3, 4, 5-trimethoxyphenyl (TMP) is an important microtubule targeting pharmacophore. Based on the pharmacophore combination principle, we incorporate the TMP pharmacophore into the aurone structure and design a novel polymethoxy derivative that is expected to inhibit tumor cell proliferation through regulating the cell cycle. MethodsBy introducing different substituents on C-4′ and C-3′, a series of new 4, 5, 6-trimethoxy aurone derivatives have been designed and synthesized. DU145, MCF-7 and H1299 cell lines were selected to evaluate their anticancer activity. The compound with the best cytotoxicity was then selected and the anticancer mechanisms were investigated by network pharmacology, flow cytometry, Western blot, and cell heat transfer assay. ADMET prediction evaluated the draggability of aurone derivatives. ResultsAurones 1b and 1c have selective anti-proliferative activity against DU145 cells. Among them, the compound 1c have better cytotoxicity against DU145. Compound 1c could bind the active cavity of CyclinB1/CDK1/CKS complex protein and induced G2/M phase arrest of DU145 cells by regulating the expression of CyclinB1 and p21. Compound 1c satisfies the Lipinski rule, is suitable for the absorption and metabolism index, and has a lower risk of cardiac toxicity. ConclusionsPolymethoxy aurones 1c might function as a CyclinB1/CDK1 inhibitor that deserved to be further developed for the treatment of prostate cancer.

Investigation of Ageing Methods on Gas Diffusion Layers for HT-PEMFC Application

Gas diffusion layers (GDLs) are commonly used materials for polymer electrolyte membrane fuel cell (PEMFC) applications. Key role of the GDL is the distribution of reaction gases evenly from the bipolar plate to the catalyst layer and enabling the removal of product water. Especially challenging are elevated temperatures and acidic conditions for materials applied in high temperature (HT) PEMFCs. In this work, ex-situ ageing tests on GDLs were performed. First, the GDLs were aged in an electrochemical set-up in concentrated phosphoric acid (PA) at temperatures up to 160 °C. After ageing, the GDLs were analysed regarding their morphology and changes in elemental composition. The results show lower impact after ageing at constant potentials of 0.1 V, 0.8 V and OCV but a significant effect of increasing temperature and higher potential of 1.2 V as well as potential cycling. This is confirmed by morphological analysis.

Biogeographic distribution, assembly processes and potential nutrient cycling functions of myxobacteria communities in typical agricultural soils in China

Predatory myxobacteria are important soil micropredators with the potential to regulate soil microbial community structure and ecosystem function. However, the biogeographic distribution patterns, assembly processes, and potential nutrient cycling functions of myxobacteria communities in typical agricultural soils in China are still poorly understood. High-throughput sequencing, phylogenetic zero modeling, and the multi-nutrient cycling index were used to assess the biogeographic distribution, assembly processes, and soil ecosystem functions of predation myxobacteria communities in typical agricultural soils of six long-term fertilization ecological experimental stations. The results demonstrated a hump-shaped distribution of myxobacteria α-diversity along the latitudinal gradient and significant differences in myxobacteria β-diversity in typical agricultural soils (P < 0.05). Bacterial richness, soil organic carbon, and pH were the most important predictors of myxobacteria α-diversity, whereas geographic factors and soil pH were the most significant ecological predictors of myxobacteria β-diversity. Myxobacteria community assembly is dominated by deterministic processes, especially homogeneous selection, primarily driven by soil pH and bacterial richness. In addition, we revealed the ecological significance of myxobacteria communities in typical agricultural soil microbial networks and the potential link between myxobacteria communities and soil nutrient cycling. These findings enhance our understanding of the biogeographic distribution, community assembly, ecological predictors, and relationships with soil nutrient cycling of myxobacteria communities in typical agricultural soils, paving the way for a more predictive understanding of the effect of predatory myxobacteria communities on soil ecosystem function, which is essential for the development of sustainable agriculture.

Modifying electronic and physical properties of Fe-NSC catalyst for oxygen reduction reaction via sulfur doping process

The primary challenge in the large-scale production of metal-air batteries or fuel cells is the high cost of Pt, which is used in the oxygen reduction reaction. To address this issue, we synthesized non-precious metal catalysts by doping Fe, N, and S in various sequences. X-ray diffraction and Raman spectroscopy proved that these catalysts had a higher degree of graphitization than carbon black. While the Fe3C phase was found in the catalyst without S, it was absent in all Fe-NSC catalysts. Imaging and X-ray absorption near edge structure (XANES) studies showed atomically dispersed Fe metal in the S-doped non-precious metal catalysts. X-ray photoelectron spectroscopy (XPS) and XANES reveal that the active site concentrations, inactive Fe-S bond, and oxidation number of the Fe species vary according to the N and S doping sequences. Fe-NSC-1 showed fast kinetics and high selectivity, with an onset potential of 0.96 V. Even after 10,000 potential cycles between 0.6 and 1.0 V, the half-wave potential for Fe-NSC-1 decreased by only 3%. Additionally, the Fe-NSC-1 catalyst showed a negligible decrease in current density during the methanol tolerance tests. Overall, this study found that the doping sequence plays a vital role in enhancing the electrochemical performance and stability of these catalysts under suitable operating conditions by influencing their chemical and electronic structures.

Polyazine nanoparticles as anchors of PQQ glucose dehydrogenase for its most efficient bioelectrocatalysis

We report on the drop-cast production of glucose biosensors based on the most efficient bioelectrocatalysis by pyrroloquinoline quinone dependent glucose dehydrogenase (PQQ GDH). To orient the enzyme upon immobilization we suggest using poly(Methylene Green) (p(MG)) nanoparticles acting as anchors. Synthesis of polymeric anchors has been carried out in course of Methylene Green electropolymerization, which allowed to tune polymer-to-monomer ratio in the drop-cast mixtures varying the monomer concentration and applying different number of potential sweep cycles. Except for elimination of electrochemical step for the electrode modification, opening the prospects for mass-production, the use of drop-cast enzyme anchors provides advantageous characteristics of the resulting biosensors. Catalytic current of PQQ GDH immobilized over p(MG) nanoparticles obtained in optimal conditions is increased only 2–2.5 times after addition of the freely diffusing mediator. Obviously, the lowest ratio of mediated-to-reagentless current points to the most efficient bioelectrocatalysis. The obtained ratio is 2.5 times lower than that for biosensors based on electropolymerized p(MG) films and practically an order of magnitude lower than that for the best reagentless sensors based on PQQ GDH immobilized over conductive nanomaterials. The achieved most efficient bioelectrocatalysis provides high sensitivity of the elaborated biosensors even at 0.0 V potential, which allows to operate them in power generation mode and control relative sweat glucose variation as a tool for non-invasive diabetes monitoring.

Tailoring hierarchically porous nanoarchitectured N-doped carbon decorated with FeIIN4 moiety and encapsulated Fe/Fe3C nanoparticles as a synergistic catalyst for ORR in Zn-air battery

Rational designing and exploiting non-noble metal electrocatalysts with desirable nanoarchitecture and abundant active sites are crucial but challenging requirements for the development of fuel cells and Zn-air batteries (ZABs). Herein, a highly efficient carbonous hybrid is developed using a facile and effective synthesis strategy via template-assisted and optimized post-pyrolysis processes. The optimized electrocatalyst (denoted as Fe@NC-700) has extremely large specific surface area (1262.8 m2 g–1), and presents a desirable hierarchically porous nanoarchitecture, including plenty micro-/meso-pores, which endows the catalyst with the enhanced mass transfer for the reaction species. More importantly, Fe@NC-700 possesses not only numerous FeIIN4 moiety uniformly dispersed in N-doped carbon matrix, but also encapsulated Fe/Fe3C nanoparticles, synergistically boosting the electrocatalytic activity towards oxygen reduction reaction (ORR) verified by density functional theory (DFT) calculation. Due to the beneficial microstructure and rich active sites, the catalyst has a positive half-wave potential (E1/2) of 0.865 V for ORR in alkaline electrolyte, intrinsic 4e– reaction path and robust stability (only 14 mV negative shift of E1/2 after 10,000 potential cycles), outperforming the Pt/C. Impressively, the aqueous and quasi-solid-state primary ZABs assembled with Fe@NC-700 as cathode catalyst demonstrate superior discharge performance and excellent durability, holding promising potential in practical application of energy conversion devices.

Surface-optimized carbon nanocages with tailorable atomic Fe-N4 sites to boost oxygen reduction in long stable zinc-air battery

High-efficiency and durable precious-metals-free electrocatalysts for oxygen reduction (ORR) are crucial to Zn-air battery (ZAB). Herein, a molten salt-assisted pyrolysis is reported to construct fully open carbon nanocages with highly atomically dispersed Fe-N4 sites (Fe-SA/NC) as air cathode. The chemical etching in pyrolysis can induce such highly active surface structure with abundant surface Fe anchoring sites and regulate the uncoordinated pyridinic nitrogen. The theoretical investigations reveal that engineering the adjacent uncoordinated pyridinic nitrogen can efficiently modulate the charge distribution and lower d-band center position of FeN4, thus reducing the dissociation energy of intermediate OH*. The Fe-SA/NC exhibit outstanding catalytic activity with 0.905 V (vs. RHE) half-wave potential and excellent cycling stability, surpassing commercial Pt/C and most reported M-N-C catalysts. The ZAB with the Fe-SA/NC as air cathode delivers a high power density of 240 mW cm−2, large specific capacity (815 mAh g−1) and long-term durability over 1050 h. This work highlights the rational design and fabrication of efficient M-N-C single-atom catalysts from the point of view of both morphological engineering and local coordination chemistry.

Differences in the electrochemical behavior of Vulcan XC-72 carbon black and glassy carbon after prolonged potential cycling

The electrochemical characteristics of a carbon carrier play an important role in catalyst investigations. The evolution of the electrochemical characteristics of Vulcan XC-72 carbon black and a glassy carbon disk electrode was studied under prolonged electrochemical action. The electrochemical action was performed by repeated application of a sawtooth periodic potential to the electrodes in the range from 0.05 to 1 V vs. RHE and back at a scan rate of 50 mV/s. The EDL charging current, the cyclic current–voltage curves, the equilibrium electrode potential, and the dissolved oxygen reduction current in potentiostatic mode at 0.05 V vs. RHE were recorded periodically. Carbon black was characterized by helium pycnometry, SEM, TEM, X-ray diffraction, and Raman spectroscopy. The currents on the carbon black were several orders of magnitude higher than those on the glassy carbon. The differences in the dynamics of electrochemical characteristics are discussed.

Ex Vivo Electrochemical Monitoring of Cholinergic Signaling in the Mouse Colon Using an Enzyme-Based Biosensor.

Cholinergic signaling, i.e., neurotransmission mediated by acetylcholine, is involved in a host of physiological processes, including learning and memory. Cholinergic dysfunction is commonly associated with neurodegenerative diseases, including Alzheimer's disease. In the gut, acetylcholine acts as an excitatory neuromuscular signaler to mediate smooth muscle contraction, which facilitates peristaltic propulsion. Gastrointestinal dysfunction has also been associated with Alzheimer's disease. This research focuses on the preparation of an electrochemical enzyme-based biosensor to monitor cholinergic signaling in the gut and its application for measuring electrically stimulated acetylcholine release in the mouse colon ex vivo. The biosensors were prepared by platinizing Pt microelectrodes through potential cycling in a potassium hexachloroplatinate (IV) solution to roughen the electrode surface and improve adhesion of the multienzyme film. These electrodes were then modified with a permselective poly(m-phenylenediamine) polymer film, which blocks electroactive interferents from reaching the underlying substrate while remaining permeable to small molecules like H2O2. A multienzyme film containing choline oxidase and acetylcholinesterase was then drop-cast on these modified electrodes. The sensor responds to acetylcholine and choline through the enzymatic production of H2O2, which is electrochemically oxidized to produce an increase in current with increasing acetylcholine or choline concentration. Important figures of merit include a sensitivity of 190 ± 10 mA mol-1 L cm-2, a limit of detection of 0.8 μmol L-1, and a batch reproducibility of 6.1% relative standard deviation at room temperature. These sensors were used to detect electrically stimulated acetylcholine release from mouse myenteric ganglia in the presence and absence of tetrodotoxin and neostigmine, an acetylcholinesterase inhibitor.

PtZn nanoparticles supported on porous nitrogen-doped carbon nanofibers as highly stable electrocatalysts for oxygen reduction reaction

The oxygen reduction reaction (ORR) electrocatalytic activity of Pt-based catalysts can be significantly improved by supporting Pt and its alloy nanoparticles (NPs) on a porous carbon support with large surface area. However, such catalysts are often obtained by constructing porous carbon support followed by depositing Pt and its alloy NPs inside the pores, in which the migration and agglomeration of Pt NPs are inevitable under harsh operating conditions owing to the relatively weak interaction between NPs and carbon support. Here we develop a facile electrospinning strategy to in-situ prepare small-sized PtZn NPs supported on porous nitrogen-doped carbon nanofibers. Electrochemical results demonstrate that the as-prepared PtZn alloy catalyst exhibits excellent initial ORR activity with a half-wave potential (E1/2) of 0.911 ​V versus reversible hydrogen electrode (vs. RHE) and enhanced durability with only decreasing 11 ​mV after 30,000 potential cycles, compared to a more significant drop of 24 ​mV in E1/2 of Pt/C catalysts (after 10,000 potential cycling). Such a desirable performance is ascribed to the created triple-phase reaction boundary assisted by the evaporation of Zn and strengthened interaction between nanoparticles and the carbon support, inhibiting the migration and aggregation of NPs during the ORR.