Buffering Capacity Research Articles

Maximum exercise capacity: Barcroft revisited in a large population

RATIONALE In 1973, the first exercise test was performed at McMaster University Medical Center to provide a standardized approach to clinical exercise testing, based on Barcroft’s maxim that the maximum capacity to exercise is “the essence of the machine,” emphasizing integration between different mechanisms. The test was incremental ergometer exercise to symptom limited maximum. Physiologic and symptom measurements were made before and during exercise. 46,288 tests were collected and entered into a dataset; unique both in terms of the large number and the physiologic variables collected (skeletal muscle strength, gas transfer capacity, symptoms). OBJECTIVES The objective of this study was to understand CO2 production in relation to oxygen uptake when exercising to maximum capacity. MEASUREMENTS AND MAIN RESULTS Physiologic factors contributing to maximum exercise capacity (Wmax) were skeletal muscle strength, FEV1 (ventilatory capacity) and DLCO (gas transfer capacity). The response of VCO2 in relation to VO2 (RER) showed a lag in CO2 production (related to CO2 storage), which was longer in subjects with higher maximum exercise capacity. This lag was followed by a progressive increase toward W max that reached a maximum value independent of W max. The perceived intensity of leg effort and dyspnea increased in a positively accelerating manner in parallel with increases in CO2 output. CONCLUSION Maximum power in incremental cycling was symptom limited, dependent on muscle (strength, oxidative capacity), together with FEV1. Previous emphasis on oxygen delivery as limiting exercise, irrespective of clinical diagnosis, may be augmented by the perceptual limitation that accompanies, remarkably symmetrically, the adaptation to CO2 removal maintaining homeostasis in muscle (muscle buffering capacity).

Metal Ion-/Proton-Coupled Electron Transfer (MPCET) on ortho-Quinone.

Quinol/quinone equilibria are ubiquitous in nature and find multiple technological applications, most recently in electrical charge storage. Much research has been devoted to proton-coupled electron transfer (PCET) in such systems and to bidentate complexation of ortho-quinol (catechol) ligands with multivalent metal ions but rarely to the interplay of these two reactions. Here, we investigate the impact of a redox-inactive metal ion, as a complexing and charge-compensating agent, on redox processes of catechol in aqueous solutions, that is, in the presence of proton equilibria. We pay separate attention to their thermodynamics and kinetics, which can be regulated by the pH and buffer capacity. As the proton buffer concentration decreases, proton equilibria during catechol PCET are slower to establish, thus kinetically prioritizing the participation of the metal ion rather than the proton in the redox charge compensation. Making use of this kinetic interplay can be a general strategy to conceive organic battery cathodes for proton-free metal-ion aqueous batteries.

Chrysophanol‐Loaded Composites with Xanthan Gum/Polycaprolactone for Drug Release Enhancement

AbstractThis work focused on synthesizing novel chrysophanol‐loaded composites with varied ratios of polycaprolactone/xanthan gum to enhance the release of chrysophanol. The characteristics of the obtained composites were analyzed by infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry, rhermogravimetric analysis and dynamic light scattering methods. The xanthan gum/polycaprolactone/chrysophanol (XPC) composites were obtained in the powdery form with particle sizes ranging from 80–100 nm. The results of hydrophilic and hydrophobic tests of the composites were discussed. Chrysophanol, polycaprolactone and xanthan gum can interact and are compatible to each other. XPC composites exhibit high stability and don't cause the negative effect on cells. Additionally, the chrysophanol release and kinetic model of chrysophanol release from the XPC composites in different pH buffer solutions were investigated and evaluated. Using drug carriers such as xanthan gum and polycaprolactone can enhance the release of chrysophanol in both pH 2.0 and pH 7.4 buffer solutions. In the presence of biopolymers, the distribution ability of chrysophanol in aqueous solutions such as pH 2.0 buffer, pH 7.4 buffer solutions, and 0.9 % NaCl solution was enhanced significantly. This will be favorable for an increase in the absorption of chrysophanol in the human body.

An adaptive and multi-path greedy perimeter stateless routing protocol in flying ad hoc networks

In recent years, flying ad hoc networks (FANET), formed from unmanned aerial vehicles (UAVs), have absorbed the attention of academic and industrial research communities due to their many applications in military and civilian fields. FANETs benefit from unique features, including highly moving UAVs and dynamic topological structure. Therefore, most existing routing protocols, such as the greedy perimeter stateless routing (GPSR), are not compatible with the FANET environment and its specific features. To improve the performance of GPSR in FANET, it is important to address several challenges, namely the selection of the right period for broadcasting hello messages in the network, the selection of the right criteria for selecting the next-hop node, and the improvement of reliability in the data transfer process. In this paper, an adaptive and multi-path greedy perimeter stateless routing (AM-GPSR) protocol is suggested in FANETs. It includes two new strategies, namely adaptive hello strategy and multi-path greedy forwarding strategy. The adaptive hello strategy defines a special hello broadcast period for each UAV according to its speed and error between two estimated and actual positions. Furthermore, the greedy forwarding strategy carries out a filtering operation on candidate nodes and eliminates border UAVs and those that are far from the destination. Then, candidate UAVs are prioritized based on the time to reach the destination and buffer capacity, and UAVs with higher priorities are chosen to send data packets. Finally, AM-GPSR applies a greedy multi-path forwarding strategy to increase reliability in the data transmission process. Lastly, the simulation of AM-GPSR is done via the network simulator version 2 (NS2) to evaluate its performance. This evaluation process includes two different scenarios, i.e. change in the speed of UAVs and change in their communication range. In this process, AM-GPSR is compared with three other methods, namely the aerial greedy geographic routing (AGGR) protocol, the geolocation assisted aeronautical routing protocol (AeroRP), and GPSR. This comparison shows the successful performance of AM-GPSR in terms of delivery success rate, throughput, and delay. Although the control overhead of the proposed method is more than that of AGGR.

In Situ Polymerization for Manufacture of Multifunctional Delivery Systems for Transcellular Delivery of Nucleic Acids.

Electrostatic self-assembly between negatively charged nucleic acids and cationic materials is the basis for the formulation of the delivery systems. Nevertheless, structural disintegration occurs because their colloidal stabilities are frequently insufficient in a hostile biological environment. To overcome the sequential biological barriers encountered during transcellular gene delivery, we attempted to use in situ polymerization onto plasmid DNA (pDNA) with a variety of functional monomers, including N-(3-aminopropyl)methacrylate, (aminopropyl)methacrylamide hydrochloride, 1-vinylimidazole, and 2-methacryloyloxyethylphosphorylcholine and N,N'-bis(acryloyl) cystamine. The covalently linked monomers could polymerize into a network structure on top of pDNA, providing excellent structural stability. Additionally, the significant proton buffering capacity of 1-vinylimidazole is expected to aid in the release of pDNA payloads from acidic and digestive endolysosomes. In addition, the redox-mediated cleavage of the disulfide bond in N,N'-bis(acryloyl)cystamine allows for the selective cleavage of the covalently linked network in the cytosolic microenvironment. This is due to the high intracellular level of glutathione, which promotes the liberation of pDNA payloads in the cell interiors. The proposed polymerization strategies resulted in well-defined nanoscale pDNA delivery systems. Excellent colloidal stabilities were observed, even when incubated in the presence of high concentrations of heparin (10 mg/mL). In contrast, the release of pDNA was confirmed upon incubation in the presence of glutathione, mimicking the intracellular microenvironment. Cell transfection experiments verified their efficient cellular uptake and gene expression activities in the hard-transfected MCF-7 cells. Hence, the polymerization strategy used in the fabrication of covalently linked nonviral gene delivery systems shows promise in creating high-performance gene delivery systems with diverse functions. This could open new avenues in cellular microenvironment engineering.

Co-transport of citrate-modified biochar nanoparticles and released plant-available silicon in saturated porous media: Effect of LMWOAs and solution chemistry

Citrate-modified biochar nanoparticles (CBCNPs) represent a promising amendment with plant-available silicon (PASi) releasing capacity. However, the co-transport behavior with released PASi remain poorly understood. This study investigated their co-transport in saturated porous media under various solution chemistry and low molecular weight organic acids (LMWOAs). Experimental and two-site kinetic model results revealed that higher ionic strength caused favorable aggregation and size-selective, hindering CBCNPs transport. Divalent Ca2+ ions retained CBCNPs more effectively than K+ due to stronger charge screening and cation bridging. The pH buffering capacity of CBCNPs resulted in consistent transport behavior across a broad pH range (4–8). XDLVO calculation clarified the impact mechanisms of IS, ion types and pH on CBCNPs transport. Furthermore, LMWOAs exhibited a time-dependent blocking effect on CBCNPs transport. Oxalic acid (OA) and citric acid (CA) facilitated CBCNPs transport though mechanisms beyond XDLVO, including steric hindrance, competitive adsorption, and surface hydrophilicity. The presence of LMWOAs significantly hindered PASi co-transport, with the inhibitory effect ranked as acetic acid (AA) ≈ CA > OA > absence of organic acids. The inhibition is attributed to the blocking effect and formation of Si-organic acid complexes, as evidenced by breakthrough curves and density functional theory calculations. This study provides novel insights into the co-transport of CBCNPs with released PASi through mutual mechanisms, indicating both potential environmental benefits and risks.

Environmental modulators of algae-bacteria interactions at scale

Interactions between photosynthetic and heterotrophic microbes play a key role in global primary production. Understanding phototroph-heterotroph interactions remains challenging because these microbes reside in chemically complex environments. Here, we leverage a massively parallel droplet microfluidic platform that enables us to interrogate interactions between photosynthetic algae and heterotrophic bacteria in >100,000 communities across ∼525 environmental conditions with varying pH, carbon availability, and phosphorus availability. By developing a statistical framework to dissect interactions in this complex dataset, we reveal that the dependence of algae-bacteria interactions on nutrient availability is strongly modulated by pH and buffering capacity. Furthermore, we show that the chemical identity of the available organic carbon source controls how pH, buffering capacity, and nutrient availability modulate algae-bacteria interactions. Our study reveals the previously underappreciated role of pH in modulating phototroph-heterotroph interactions and provides a framework for thinking about interactions between phototrophs and heterotrophs in more natural contexts.

Forest canopy cover affects microclimate buffering during an extreme heat event

Increasing temperatures and extreme heat episodes have become more common with climate change. While forests are known to buffer increasing temperatures (relative to non-forested areas), whether this buffering is maintained under extreme temperature events is relatively unknown. Here we assess whether forests continue to buffer microclimate (specifically temperatures) during an extreme heat event: the Pacific Northwest (PNW) heat dome in June 2021. We use a combination of ground-based and regional climate data and find that forest understories were 3 °C cooler than a clear-cut area and 4 °C cooler than regional temperatures during the PNW heat dome. By examining forests with different levels of canopy cover we also found that the buffering capacity of forests is greater under denser canopies even under extreme heat events. Additionally, we found vertical variation in thermal buffering, with the greatest amount of buffering at the surface of the forest floor. Overall, our findings suggest that temperate coastal forests, that are known to buffer average temperatures, can also act as microclimate buffers during extreme heat events like the heat dome that occurred in the PNW in 2021. This could be good news for forest dwelling organisms that are sensitive to such extreme heat events.

Sex-dependent responses to acute sodium bicarbonate different dose treatment: A randomized double-blind crossover study

ObjectivesThis study quantified blood bicarbonate (HCO3−) kinetics and gastrointestinal upset to determine the gender-related ergogenic potential of sodium bicarbonate (0.15-, 0.25- and 0.35 gSB·kgFat-free mass (FFM)–1) in high intensity functional training. DesignDouble-blind randomized placebo-controlled crossover. MethodsThirty female and male athletes performed two bouts of the Wingate Anaerobic Test (WAnTPRE-HIFT and WAnTPOST-HIFT) interspaced with two 3-min bouts of Wall Balls and Burpees 120min after ingestion of three sodium bicarbonate doses. Blood HCO3− was determined pre-ingestion, after supplementation and before/post exercise. Gastrointestinal upset was evaluated 120min post-ingestion. Control (CTRL) measurements were performed. ResultsThere were significant gender×treatment interactions for: changes in blood HCO3− at 60min post-ingestion (p=0.014; η2p=0.104; at 0.15gSB·kgFFM−1 males experienced higher increase than females); peak power (p=0.015; η2p=0.103) and average power (p=0.005; η2p=0.124) during WAnTPOST-HIFT, and changes in peak power between the Wingate Anaerobic Test bouts (p=0.049; η2p=0.081). Sodium bicarbonate compared to PLA had no significant impact on Wall Balls and Burpees performance. The dose of 0.35gSB·kgFFM−1 resulted in higher less severe gastrointestinal symptoms compared to CTRL and 0.15gSB·kgFFM−1 (p=0.001; W=0.178); and higher total gastrointestinal upset compared to CTRL, PLA and 0.15gSB·kgFFM−1 (p<0.001; W=0.323). ConclusionsThere were dose- and gender-related differences in extracellular buffering capacity and ergogenic potential of sodium bicarbonate. The study suggested a detrimental impact of gastrointestinal upset on performance.

Differences in the growth, acidification, and proteolytic activities of Lactobacillus helveticus, Lactobacillus delbrueckii subsp. bulgaricus, and Streptococcus thermophilus in camel and cow milk fermentation

This study investigates low-fat camel milk and cow milk fermentation behavior by Lactobacillus helveticus, Lactobacillus delbrueckii subsp. bulgaricus, and Streptococcus thermophilus at 28, 35, and 42 °C. Bacterial counts, titratable acidity (TA%), pH, lactose, lactic acid, and proteolysis were followed for 96 h. Temperature and bacteria highly affected all these parameters (p < 0.001) while milk type affected bacterial counts and degree of proteolysis and lactose (p < 0.001), pH, and lactic acid (p < 0.01) but did not affect TA (%). Fermented camel and cow milk products showed similar negative correlations between TA (%) and pH suggesting comparable buffering capacities. In both fermented products, the behavior of L. helveticus was more comparable to that of S. thermophilus than L. bulgaricus. Principal component analysis (PCA) showed a negative correlation between bacterial growth and the degree of proteolysis. The results of this study provided insights into the complex dynamics of bacterial interactions with different milk substrates.

Effects of a pH-Regulating Emollient Cream in Mild Atopic Dermatitis Patients with Moderate Localized Lesions

Introduction: Increased skin pH values in patients with atopic dermatitis (AD) contribute to poor antimicrobial and permeability barrier functions of the skin. In practice, the majority of topical preparations available for dry skin conditions do not provide sufficient pH and buffering capacity for maintaining optimum skin surface conditions. To address this issue, we tested a novel zinc lactobionate preparation to determine whether the regular application would lower skin surface pH, and in doing so improve the condition of lesional skin. Methods: The assessment for local severity of AD was done with the Scoring Atopic Dermatitis Index (SCORAD) and skin dryness was assessed by capacitance measurement. Results: The results showed that the test product lowered skin pH and improved AD skin lesions from moderate to mild during 2 weeks of application. In the treated area a lowered pH of about 0.85 units was found. Together with the lowering of pH, the local SCORAD significantly improved from 8.3 on average down to 4.0, while in the untreated area, only a slight improvement (from 8.2 to 6.4) was found. Conclusion: Synergistic effects of the test product’s pH lowering and emollient properties might explain the observed improvements in clinical signs of AD and further research against a comparator would allow the specific contribution of pH modulation to these improvements to be unambiguously isolated.

Electrodeposited multiphase Sb, SbSn, Cu2Sb composite with superior chemical buffering as negative electrode for lithium-ion batteries: Effect of composition on lithiation behavior of Sb-Sn-Cu alloys

Antimony-tin ternary alloys outperform graphite as negative electrodes for lithium-ion batteries, offering significantly higher gravimetric and volumetric capacities. These alloys, conductive without additives, can be electrodeposited without binders, enhancing cell design and capacity. Based on bath composition, Sn-rich or Sb-rich SbSnCu ternary alloys can be synthesized which undergoes active-active-inactive chemical buffering during lithiation. The Sb-rich alloys show better stress buffering due to more lithiation/delithiation peaks and better use of lithium-inactive copper. This study finds Sb-rich alloys exhibit superior structural stability and electrochemical performance, delivering 374 mAh g−1 at 200 mA g−1 after 100 cycles, while Sn-rich alloys show substantial capacity fading, retaining only 113 mAh g−1. The Sb-rich alloy maintains structural integrity, losing only 20 % capacity over the last 80 cycles, compared to 48 % loss in capacity during the 50–80th cycles in Sn-rich alloys.

Assessment of Chronic Malnutrition and Its Correlation With Oral Health Status in Children Aged Three to Six Years in Jabalpur District, India: An Epidemiological Study.

This study aims to examine the correlation of chronic malnutrition with the oral health status of children aged three to six years. A total of 400 children were selected and divided into four groups based on z-scores. For evaluation of oral health status, teeth were examined for dental caries using the decayed, missing, and filled permanent teeth (DMFT) scores. Salivary samples were collected to measure salivary flow rate (SFR), pH, and salivary buffering capacity (SBC). Teeth were also visualized to detect the presence or absence of enamel hypoplasia. The data obtained was statistically analyzed (p<0.05). A total of 400 children participated and were also categorized into mild, moderate, and severe obesity according to the z-scores. The mean DMFT scores among adequately nourished children were 2.4086; with severely malnourished and severely obese children, the mean values were found to be 1.0652 and 1.4286, respectively. The mean SFR among children with adequate nutrition was 1.0366, and the mean flow rate among children with severe malnutrition and obesity was 0.5348 and 0.4036, respectively. The mean salivary pH among children with adequate nutrition was 7.1295, and the mean values for participants with severe malnutrition and severe obesity were found to be 6.4772 and 7.6521, respectively. The mean SBC among children with adequate nutrition was found to be 4.4861; for severely malnourished children and those with severe obesity, the values were 3.2472 and 2.8332, respectively. There was an absence of enamel hypoplasia in children with adequate nutrition, whereas a total of five participants with severe malnutrition and three children with severe obesity were found to have hypoplastic lesions, respectively. Malnutrition exerts a negative impact on the overall oral health of children. It is critical to diagnose the effects of malnutrition on children's oral environments in order to provide appropriate treatment and enhance their quality of life.

The structural assessment for concrete structure on the onset of cracking with respect to steel corrosion

The present study concerns structural behaviour of a marine bridge in terms of cracking exposed to a seawater environment under the risk of chloride-induced corrosion with the axial loading. In the modelling process, the corrosion propagation was expressed into the rust formation on the steel surface, while the axial load was given 5–30 % to the compressive strength of concrete. The interfacial gap between steel and concrete was taken 10 µm, imposing the buffering capacity against a build-up of the rust at the steel-concrete interface. As a result, it was found that the tensile damage produced the cracking on the surface of concrete with a minimal corrosion of steel, which was further developed into the inner concrete depth with increasing corrosion formation. Also, an increase in the axial load resulted in an increase in the surface cracking at a given rust formation. At the steel-concrete interface, the cracking was much affected by the compressive deformation arising from a build-up of rust, as being limited in the vicinity in the interfacial zone, presumably due to the limited rust formation. A combination of steel corrosion and axial loading imposes the accelerated cracking of concrete structure then to rapidly deteriorate its serviceability.

Effects of water chemistry on corrosion and plugging in the copper heat exchangers of water-cooled generators in power plants

Corrosion and plugging of hollow copper conductors in water-cooled generators can cause system failures, such as flow restrictions and forced unit outages. Although both neutral water chemistry (NWC) and slightly alkaline water chemistry (SAWC) have been proposed as solutions, field operations show that NWC frequently suffers from system failures, while SAWC demonstrates high reliability. The scientific basis for this phenomenon has not been well understood. In this paper, the thermodynamics of NWC and SAWC were established to compare their tendencies toward copper corrosion and plugging. SAWC keeps copper in a stable CuO passivation region, exhibiting a superior buffer capacity against CO2 inleakage and the temperature rise of the cooling water. This buffer capacity is further enhanced by increasing the degree of the slight-alkalization. Under the SAWC with a pH value of 9.0 at 298.15 K, the concentration of the dissolved copper species is extremely low, and the positive temperature coefficient of CuO solubility prevents the accumulation of copper corrosion products in high-temperature regions. In contrast, NWC is susceptible to corrosion and plugging due to its poor buffer capacity. This study provides new insights into the effects of water chemistry on copper corrosion and plugging from a thermodynamic perspective, offering a sound theoretical basis for field operations.

Alleviation of volatile fatty acids inhibition in anaerobic digestion of swine manure with nano-bubble water supplementation

Nano-bubble water (NBW) was applied to anaerobic digestion (AD) to alleviate volatile fatty acids (VFAs) inhibition, improve the buffering capacity and CH4 production in this work. Results indicated that NBW accelerated the consumption of VFAs and prevented inhibition due to VFAs accumulation. Additionally, NBW facilitated a rapid increase in partial alkalinity (PA) and total alkalinity (TA) as well as a corresponding rapid decrease in intermediate alkalinity (IA)/PA and VFA/TA, thereby improving buffering capacity and alleviating VFAs inhibition. Moreover, CH4 production improved by more than 12.2% by NBW. Similarly, the activities of the extracellular hydrolases and coenzyme F420 increased. Besides, NBW increased the abundance of microbial community and strengthened the metabolic pathways of hydrogenotrophic methanogens, which could be the intrinsic mechanism by which NBW alleviated VFAs inhibition, improved system stability, and increased CH4 production. This study demonstrates that NBW supplementation can be an effective method for mitigating frequent VFAs inhibition.

VMT/ACP/Dextran composite nanosheets against dental caries through promoting mineralization of dentin tubules, pH buffering, and antibacterial

Dental caries is a worldwide public healthcare concern, and is closely related to the acidic environment that caused by bacterial decomposition of food. In this study, a two-step ion exchange liquid-phase stripping method was applied to strip out vermiculite (VMT) nanosheets, then amorphous calcium phosphate (ACP) and dextran were inserted between the VMT nanosheets interlayer to obtain a composite two-dimension nanosheets (VMT/ACP/Dextran). VMT/ACP/Dextran composite nanosheets exhibited excellent biocompatibility and could provide exogenous Ca2+and PO43− from ACP, provide SiO44−, Mg2+, Fe2+ and obtain buffering pH and antibacterial properties from VMT, as well as improve suspension stability and targeting Streptococcus mutans through glucan. The in vitro study showed that the composite materials could promote the mineralization and sealing of dentin tubules by releasing active ions, buffer pH 4.5 (a value close to the pH in the dental plaque environment) to pH 6.6–7.1 (values close to the pH in human saliva) through ion exchange, and exert antibacterial effects by targeting Streptococcus mutans and exerting oxidase like and peroxidase like activities to produce reactive oxygen species (ROS). The in vivo animal study showed that daily cleaning teeth using VMT/ACP/Dextran composite nanosheets could effectively reduce the incidence rate and severity of dental caries in rats. Taking together, the developed VMT/ACP/Dextran composite nanosheets, which integrated the excellent properties of VMT, ACP and dextran, can effectively prevent dental caries through a combination of factors such as buffering acids, antibacterial properties, and promoting calcification, and may be used as an active ingredient for daily oral hygiene or filling materials to prevent and treat dental caries.

Anodische H2O2‐Erzeugung in Elektrolyten auf Karbonatbasis – Mechanistische Erkenntnisse Mittels Elektrochemischer Rastermikroskopie

AbstractFür die anodische H2O2‐Bildung kann die Elektrolytzusammensetzung den Reaktionsweg in Richtung einer erhöhten Produktbildung lenken. Frühere Untersuchungen zur Optimierung der Elektrolytzusammensetzung haben gezeigt, dass die Auswirkungen des molaren Anteils der Karbonatspezies für verschiedene Anodenmaterialien unterschiedlich sind, und daher gibt es weiterhin Kontroversen über die Reaktionswege und die an der H2O2‐Bildung beteiligten Spezies. In Anbetracht der Tatsache, dass die Wasseroxidation zur Freisetzung von Protonen in der Anodenmikroumgebung führt, würde die entsprechende Ansäuerung eine Gleichgewichtsverschiebung zwischen den Karbonatspezies bewirken, was wiederum den Reaktionsweg modulieren könnte. Wir haben die Veränderungen im Anteil der Karbonatspezies in der Nähe einer arbeitenden Anode bestimmt, indem wir lokale pH‐Messungen mit einer Au‐Nanoelektrode, die mittels elektrochemischer Scherkraft‐Rastermikroskopie (SECM) in unmittelbarer Nähe einer sich in Betrieb befindlichen Anode positioniert war, durchgeführt haben. Es konnte bestätigt werden, dass die wichtigste anionische Spezies an der Grenzfläche HCO3− ist, und zwar bei Potentialen, bei denen H2O2 bevorzugt gebildet wird, unabhängig vom pH‐Wert im Volumen der Lösung. Die gleichzeitige Verwendung einer Au−Pt‐Doppelmikroelektrode in Generator‐Kollektor‐SECM‐Messungen zeigt, dass die lokale HCO3−Konzentration insgesamt durch den Oxidationsstrom, die Pufferkapazität und den pH‐Wert des Elektrolyten bestimmt wird.

Anodic H2O2 Generation in Carbonate-Based Electrolytes-Mechanistic Insight from Scanning Electrochemical Microscopy.

For the anodic H2O2 generation, it has been shown that the electrolyte composition can steer the reaction pathway toward increased H2O2 generation. Previous efforts made on composition optimization found that the impact of the molar fraction of carbonate species varies for different anodes, and therefore, controversies remain concerning the reaction pathways as well as the species involved in H2O2 formation. Considering that water oxidation results in the liberation of protons within the anode microenvironment, the corresponding acidification would cause an equilibrium shift between carbonate species, which in turn may modulate the reaction pathway. We determined the changes in the fraction of carbonate species in the vicinity of an anode by performing local pH measurements using a Au nanoelectrode positioned in close proximity to an operating anode by shear-force scanning electrochemical microscopy (SECM). It could be confirmed that the main anionic species at the interface is HCO3 -, at potentials where H2O2 is preferentially formed, regardless of the pH value in the bulk. The simultaneous use of a Au-Pt double barrel microelectrode in generator-collector SECM measurements demonstrates that the local HCO3 - concentration is collectively determined by the oxidation current, buffer capacity, and bulk pH of the electrolyte.

Coadsorption mechanisms of copper and sulfamethoxazole by functionalized cellulose: A kinetic and DFT study

In order to address the issue of compound pollution from heavy metals and antibiotics in aquatic environments, multibranched functionalized cellulose materials (DACS) with abundant adsorption affinity groups (such as amino, carboxyl and imine groups) were prepared by oxidation, etherification and grafting. The maximum adsorption capacities of DACS for copper (Cu) and sulfamethoxazole (SMZ) were 42.27 and 117.92 mg/g, respectively. In addition, its excellent pH buffering capacity, resistance to coexisting interfering substances and great regeneration performance of up to 91 % after 5 cycles. In the coadsorption experiment, the multibranched structure strengthened the bridge effect during the coadsorption process, and weakened the inhibition of SMZ adsorption caused by competition. Kinetic models and error functions analysis showed that PNO model and F&S model were the most consistent with the adsorption process, and the limiting step of adsorption was the external diffusion of Cu and SMZ around the surface of DACS. Moreover, the density functional theory (DFT) was used to quantitatively calculate the adsorption binding energy of multiple sites on DACS, and clarified the adsorption tendency of DACS as electron donors for Cu and as acceptor for SMZ. In addition, the binding energy of sequential adsorption was greater than that of single and binary adsorption, and the binding stability of SMZ was significantly increased in sequential adsorption for the increasing of binding energy. The electron exchange process in the adsorption showed that SMZ played a bridging role in the binary adsorption, while Cu was the main reaction part of the complex adsorption.