pH Changes Research Articles

Comprehensive evaluation of fungal-induced corrosion in aluminum alloys by Amorphotheca resinae

Amorphotheca resinae is a fungus that particularly corrodes aeronautical aluminum alloys, leading to economic issues in various industries. This study aims to investigate the effects of this fungus on the corrosion of four different aluminum alloys, namely 2024, 7075, 5083, and 3105, after 25, 50, and 75 days through scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), 3D profilometry, weight loss (%) measurement, energy dispersive spectrometry (EDS), electrochemical impedance (EIS), and pH changes. After 25 days, the 2024 alloy had the highest mycocorrosion rate (1.3417 mpy), while alloy 3105 had an undetectable value on this day. According to the EIS test, the 3105 alloy had the highest level of resistance (1.12 × 105 Ω cm2) to corrosion, while the 2024 alloy was the most susceptible (7138 Ω cm2). The qualitative data from SEM, CLSM, and 3D profilometry also confirmed the quantitative findings where the surface pits on the 2024 alloy were deeper than those of other alloys. Overall, the results showed that the lowest and highest corrosion rates mediated by A. resinae belonged to 3105 and 2024 alloys, respectively. These findings could have significant implications for industries that use aluminum alloys and might help in developing strategies to prevent or control biocorrosion.

Digitalization of Enzyme-Linked Immunosorbent Assay with Graphene Field-Effect Transistors (G-ELISA) for Portable Ferritin Determination.

Herein, we present a novel approach to quantify ferritin based on the integration of an Enzyme-Linked Immunosorbent Assay (ELISA) protocol on a Graphene Field-Effect Transistor (gFET) for bioelectronic immunosensing. The G-ELISA strategy takes advantage of the gFET inherent capability of detecting pH changes for the amplification of ferritin detection using urease as a reporter enzyme, which catalyzes the hydrolysis of urea generating a local pH increment. A portable field-effect transistor reader and electrolyte-gated gFET arrangement are employed, enabling their operation in aqueous conditions at low potentials, which is crucial for effective biological sample detection. The graphene surface is functionalized with monoclonal anti-ferritin antibodies, along with an antifouling agent, to enhance the assay specificity and sensitivity. Markedly, G-ELISA exhibits outstanding sensing performance, reaching a lower limit of detection (LOD) and higher sensitivity in ferritin quantification than unamplified gFETs. Additionally, they offer rapid detection, capable of measuring ferritin concentrations in approximately 50 min. Because of the capacity of transistor miniaturization, our innovative G-ELISA approach holds promise for the portable bioelectronic detection of multiple biomarkers using a small amount of the sample, which would be a great advancement in point-of-care testing.

New insight into process pH regulation on caproate production from waste activated sludge acidogenic fermentation liquid by cathodic electro-fermentation

Cathodic electro-fermentation (CEF) has been proven to enhance the production of caproate from biowaste by improving chain elongation metabolism. However, the impact of process pH control in catholyte to avoid pH changes caused by redox reactions under polarized cathode on chain elongation has been rarely reported. Here the caproate production performances from waste activated sludge acidogenic fermentation liquid were evaluated and compared between different process pHs of 5.5, 6.0, and 6.5 with control group at 0.9 V. Results demonstrated the maximum caproate concentration was reached 4.1 g/L at pH 6.0, which was significantly higher than the 2.7 g/L of the control group, indicating the benefits of pH control on chain elongation metabolism in CEF. Mechanisms analysis revealed that the enhancement of pH regulation was attributed to the enrichment of organic degraders (Pseudomonas) in catholyte and the increased metabolic activity (like acetyl-CoA carboxylase) of chain elongator (Clostridium_sensus_stricto_12) on biofilm. These results were evidenced by the improved release and conversion performance of substrates (especially the amino acids) in catholyte and the enhanced biofilm activity. Hence, this study contributes novel insights to the pH regulation of chain elongation for enhancing caproate production from biowaste by electro-fermentation.

Evaluation of substrates for optimizing vermicomposting products

The high global market value of fresh mushrooms implies high importance of spent mushroom substrate (SMS) as a by-product that poses environmental challenges, if not properly treated. Reported studies demonstrate the positive effects of SMS on earthworm growth and reproduction, particularly when combined with other substrates such as cow dung (CD). This study utilized SMS and CD as substrates in varying ratios. A total of 375 young non-clitellated Eisenia fetida were randomly assigned to plastic containers, ensuring similar average individual worm weight, and maintained at 50% to 60% moisture. Weekly observations were made on earthworm average weight, cocoon production, and hatchling count. The growth and reproduction of earthworms differed significantly among treatments, with Treatment 3 (T3) (50:50 SMS and CD) showing the highest growth and Treatment 5 (T5) (0:100 SMS and CD) the lowest. Changes in pH, EC, total Kjeldahl nitrogen (TKN), total organic carbon (TOC), C/N ratio, and total available phosphorus (TAP) were observed over the experimental period, indicating dynamic nutrient dynamics within the substrates. The exchangeable potassium decreased with increasing proportions of CD, while the exchangeable sodium content showed variation across treatments. The observed variations can be attributed to differences in initial substrate composition and microbial activity during vermicomposting.

Optimization of ultrasound-assisted enzymatic extraction, chemical constituents, biological activities, and stability of Camellia oleifera fruit shell brown pigments

The need for the use of natural pigments in food manufacturing rises steadily. However, the application of natural pigments is limited by costly production and poor stability. Hence, the brown pigments from Camellia oleifera shells (disposal from tea oil production) were focused on in this study. The enzymatic extraction of Camellia oleifera fruit shell brown pigment (BP-CS) with ultrasound assistance was optimized by Box-Behnken design to cut extraction expenses. The yield of BP-CS was 38.56% under the optimized extraction parameters as extraction time of 77 min, extraction temperature of 64 °C, cellulose concentration of 10 mg/mL and liquid-solid ratio of 20mL/g. Subsequently, for promising no harmful ingredients in BP-CS, all 36 compounds were identified, and the primary constituents were flavonoids (quercitrin, quercetin) and organic acids (D-malic acid, citric acid). Via stability analysis, the brown pigment was pretty stable under heating, pH, and sunlight changes while was impacted by metal ions and redox agent conditions. Additionally, BP-CS was able to scavenge free radicals (DPPH, ABTS, ·OH) and prevent the growth of microorganisms. Moreover, BP-CS could reduce α-amylase and tyrosinase activity, and both quenching mechanisms were static quenching. Overall, this work reveals that BP-CS is a valuable natural pigment, and is anticipated to be employed as a premium-quality pigment additive in the food industry.

A pH-sensitive motif in an outer membrane protein activates bacterial membrane vesicle production

Outer membrane vesicles (OMVs) produced by Gram-negative bacteria have key roles in cell envelope homeostasis, secretion, interbacterial communication, and pathogenesis. The facultative intracellular pathogen Salmonella Typhimurium increases OMV production inside the acidic vacuoles of host cells by changing expression of its outer membrane proteins and modifying the composition of lipid A. However, the molecular mechanisms that translate pH changes into OMV production are not completely understood. Here, we show that the outer membrane protein PagC promotes OMV production through pH-dependent interactions between its extracellular loops and surrounding lipopolysaccharide (LPS). Structural comparisons and mutational studies indicate that a pH-responsive amino acid motif in PagC extracellular loops, containing PagC-specific histidine residues, is crucial for OMV formation. Molecular dynamics simulations suggest that protonation of histidine residues leads to changes in the structure and flexibility of PagC extracellular loops and their interactions with the surrounding LPS, altering membrane curvature. Consistent with that hypothesis, mimicking acidic pH by mutating those histidine residues to lysine increases OMV production. Thus, our findings reveal a mechanism for sensing and responding to environmental pH and for control of membrane dynamics by outer membrane proteins.

Regulation of sucrose metabolism, sugar transport and pentose phosphate pathway by PacC in apple fruit colonized by Penicillium expansum

A critical transcription factor, PacC, modulates the expression of fungal pH signaling. Although PacC-mediated environmental pH has been reported to regulate the growth and pathogenicity of postharvest pathogens, the involvement of PacC in sucrose metabolism, sugar transport, and the pentose phosphate pathway (PPP) in different zones of decayed fruit remains unclear. Our work showed that the inoculation with a PePacC deletion strain of Penicillium expansum (ΔPePacC) accelerated sucrose catabolism and glucose and fructose accumulation in different zones of apple fruit. This was attributed to an increase in sucrose metabolism enzyme activities and up-regulation of the sugar transporter protein-related gene expression. Moreover, ΔPePacC inoculation increased the PPP-related enzyme activities and the levels of nicotinamide adenine dinucleotide phosphate (NADPH) and NADP+. In conclusion, PacC modulates sucrose metabolism, sugar transport, and the PPP in apple fruit by mediating dynamic changes in environmental pH, thereby enhancing fruit disease resistance.

A novel alkaline pH-responsive ratiometric probe based on hybrid fluorophores and its applications

The current study describes a novel development in the field of chromogenic and ratiometric fluorescence probes designed for pH sensing purposes. Of particular interest is the incorporation of coumarin as the recognition component in this probe, which was synthesized utilizing hybrid fluorophores containing fluorescein and coumarin. This probe exhibited two distinct fluorescence response modes toward changes in pH: a ratiometric fluorescence response at 328 nm excitation and a fluorescence switch-on response at 514 nm excitation. These responses are attributed to the structure changes induced by coumarin hydrolysis in alkaline conditions above a pH of 9, as confirmed through MS and DFT analysis. Furthermore, the practical utility of the probe was effectively evaluated through visual detection on silica gel plates and bio-imaging with Bacillus subtilis, illustrating its potential for the advancement of alkaline pH-responsive fluorescence probes.

Use of pineapple peel for the formulation of cookies and crackers

Food waste occurs worldwide and its highest rate takes place in the fruit and vegetable sector. The industrialization of pineapple fruit generates many agro-industrial residues, which possess significant amounts of fibers, minerals and vitamins. This work aimed to develop cookie and cream cracker formulations enriched with flour from pineapple peel (PPF). Two formulations were produced for each type of biscuit: conventional one and with the adding of 20% PPF. The formulations were evaluated physicochemically/nutritionally (moisture, carbohydrates, fats, proteins, fiber, ash, minerals, pH and acidity) and sensorially (color, aroma, flavor texture, global impression and purchase intent). The addition of PPF promoted changes in pH, acidity, lipids, fibers and minerals. The cookies and crackers produced with 20% PPF may be classified as a source of fiber. The addiction of PPF allowed FCR and FCO to be classified as “high content” for the following minerals: Mg, Cu, Mn and Fe, while FCR may be also classified as “high content” of Ca. The addition of peel did not affect the sensory acceptance of the products and purchase intention. Thus, the addition of PPF to food products formulations is an alternative to the use of pineapple processing residues, since it was used as ingredients on nutritionally enriched.

Generation of Microplastics from Biodegradable Packaging Films Based on PLA, PBS and Their Blend in Freshwater and Seawater.

Biodegradable polymers and their blends have been advised as an eco-sustainable solution; however, the generation of microplastics (MPs) from their degradation in aquatic environments is still not fully grasped. In this study, we investigated the formation of bio-microplastics (BMPs) and the changes in the physicochemical properties of blown packaging films based on polylactic acid (PLA), polybutylene succinate (PBS) and a PBS/PLA 70/30 wt% blend after degradation in different aquatic media. The tests were carried out in two temperature/light conditions to simulate degradation in either warm water, under sunlight exposure (named Warm and Light-W&L), and cold deep water (named Cold and Dark-C&D). The pH changes in the aqueous environments were evaluated, while the formed BMPs were analyzed for their size and shape alongside with variations in polymer crystallinity, surface and mechanical properties. In W&L conditions, for all the films, the hydrolytic degradation led to the reorganization of the polymer crystalline phases, strong embrittlement and an increase in hydrophilicity. The PBS/PLA 70/30 blend exhibited increased resistance to degradation with respect to the neat PLA and PBS films. In C&D conditions, no microparticles were observed up to 12 weeks of degradation.

A coupling numerical model for simulating groundwater uranium removal in coupling device of electric field and PRB

The remediation of groundwater uranium pollution has been successfully researched and implemented. However, the cost-effectiveness remains challenging to evaluate. Numerical modeling presents a potential solution, while the coupling of multi-physics in uranium pollution remediation has been a global challenge. This study developed a multi-physics coupled model to simulate the evolution of groundwater uranium plumes in composite remediation system, which was composed of permeable reactive barrier (PRB) and electrokinetic remediation (EKR). Meanwhile, pH changes are also taken into account. The research revolved around sandbox dynamic migration experiments, where key parameters were measured for model building. Based on this, a mathematical model for achieving multi field coupling has been proposed. Substitute equations were used to unify the calculation of flow field and electric field into the same dimension. The results showed that the pH variations induced by electrolysis propagate towards the center of the electric field. Medium adsorption of uranium reached its peak when the pH was between 4 and 5. The driving force of groundwater flow in the coupled field was about 3.5 times that of electroosmosis, occupying a dominant position. Electric fields can serve as auxiliary means to delay the migration of uranium. Under ensuring the effective operation of the system for 360 days, the system can save 25 % of PRB thickness with the EKR assistance. The model can not only predict evolution of uranium plume in groundwater, but also calculate the performance and lifespan of composite remediation systems, providing guidance and recommendations for the design of real-site remediation systems.

Benchmarking Local pH of Electrocatalysts for Water Electrolysis Using the Rotating Ring-Disk Electrode Technique

Water electrolysis is an important route for production of green hydrogen and remains a field of active research in pursuit of improved electrocatalytic activity and durability. Operating with a near-neutral feed is critical for this technology to be more widely adapted, because it allows the direct use of various water sources and imposes less stringent requirements on the components of the electrochemical cell.During water electrolysis, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) involving protons and hydroxides can experience a significant change in local pH at the surface of the catalyst, especially in near-neutral bulk conditions. This change in local pH is usually dictated by the reaction conditions such as electrolyte composition and mass transport within the system. Notably, there has been an increase in development of catalysts for water electrolysis with the ability to modulate their local pH in recent years. 1–6 However, comparing and quantifying the local pH modulation effects of these catalysts is challenging due to varying experimental techniques and protocols. The rotating ring-disk electrode (RRDE) with a potentiometric pH sensing ring has been presented as a promising and facile tool for in-situ local pH detection. 3,4,7,8 The local pH at the disk is estimated from the ring pH through solving the convective-diffusion equation under the well-defined mass transport conditions of an RRDE system. 8 In this study, we have investigated the local pH of iridium oxide during OER in both unbuffered and buffered electrolytes under near-neutral to alkaline bulk conditions using the RRDE technique. Our results provide benchmarks for future studies on the local pH modulation effects of catalysts and insights into the impact of electrolyte composition on local pH. In combination with mass transport modelling, we further examined the limitations of this technique and provide suggestions for best practices. References X. Liu et al., Appl. Catal. B Environ., 331, 122715 (2023).Z. Li et al., Angew. Chemie Int. Ed., 62, e202217815 (2023).J. Guo et al., Nat. Energy, 8, 264–272 (2023).X. Zheng et al., Nat. Commun. 2023 141, 14, 1–13 (2023).X. Wang, C. Xu, M. Jaroniec, Y. Zheng, and S. Z. Qiao, Nat. Commun. 2019 101, 10, 1–8 (2019).H. Tan et al., Nat. Commun. 2022 131, 13, 1–9 (2022).Y. Yokoyama et al., Chem. Lett., 49, 195–198 (2020).W. J. Albery and E. J. Calvo, J. Chem. SOC., Faraday Trans. 1, 79, 2583–2596 (1983). Figure 1

Unveiling a Multiplexed Sensing System for Advanced Biosensing Applications with Thread-Based Electrochemical Sensors

The miniaturization and portability of electrochemical sensing devices play a crucial role in a wide range of applications, including medical diagnostics, environmental monitoring, and point-of-care testing. Integrating a pseudo-reference electrode addresses challenges linked to traditional counterparts, ensuring enhanced portability and miniaturization without performance compromise. Our research delves into the significance of this innovation, emphasizing its impact on signal stability, reproducibility, and overall sensor reliability. The tailored pseudo-reference for compact electrochemical devices contributes to a highly efficient, cost-effective, and user-friendly design, ideal for point-of-care diagnostics and field applications. This work showcases the design, implementation, and performance evaluation of a portable electrochemical sensing system with a pseudo-reference-integrated readout circuit, improving reliability under diverse operating conditions. In the proposed research, we present the design and implementation of a dual-channel configurable multiplexed sensing platform utilizing thread-based electrochemical sensors for continuous potentiometric and amperometric measurements.For the pH sensor, the fabrication process initiates with the cleaning (using isopropyl alcohol) and subsequent plasma treatment of polysorb sutures. The cleaned sutures undergo multiple coatings (4 cycles) with conductive carbon ink, followed by baking at 60°C for 30 to 35 minutes to ensure uniform conductivity. Carbon-coated (CC) sutures undergo electrochemical pre-treatment in a solution of 0.50 M H2SO4 and 0.10 M KCl, followed by electrodeposition with polyaniline (PANI) using potentiometric deposition at 0.80 V in the presence of 0.50 M aniline in a solution containing 1.0 M H2SO4. An insulating polymer layer of 5% polyurethane (PU) is applied at the sensor's center, leaving ends exposed for electrical connections and subsequent hydrogel coating for real sample analysis. The O2 sensor fabrication involves cleaning silver-coated threads, coating with dielectric ink for a sensing region, and UV curing. Two identical threads serve as the cathode and anode, with an intentionally longer anode region as a common reference for the pH sensor. This comprehensive approach contributes to developing a versatile and efficient sensing system for multiplexed measurements, showcasing potential applications in diverse environments.The measurement system includes a signal conditioning circuit (denoted as analog front-end or AFE in Fig. 1) comprising a trans-impedance amplifier (TIA) and an op-amp in the unity-gain configuration: the former is used to convert the current into voltage which originates from the oxygen sensor whereas the latter is used to read out the open-circuit voltage (OCV) for the pH sensor. The outputs of the TIA and the voltage buffer are sequentially selected using a 2:1 multiplexer with a control bit (SEL) before digitizing using an analog-to-digital converter (ADC). There is also a digital-to-analog converter (DAC) generating a bias voltage (VBIAS) of 0.55V for the oxygen sensor as the oxygen electrode requires a certain potential to maximize the dynamic range of the current measurement. The microcontroller handles digital signal processing, which can be connected to a computer for data storage and visualization. The operation of the sensor multiplexing system is validated in standard buffer solutions and gel mediums with different pH and O2 concentrations. The proposed setup demonstrated a sensitivity of ~65 mV/pH for the pH sensor (n=3), and 0.6621 nA/mgL-1 for the O2 sensor (n=3) in a gel medium with common ions and electrolytes. The sensor results were validated against commercial oxygen and pH probes for the same solutions. The developed sensing platform and sensor can precisely monitor and track changes in pH and O2 levels within less than 2 minutes for repeated cycles. This architecture has the potential for extending the low-power multiplexed sensing to multiple biomarkers with an increased number of sensors for ingestible devices, wearable sensing, and cellular agriculture applications. KEYWORDS: Multiplexed sensing, pseudo-reference, pH and oxygen monitoring, miniaturized circuit, thread-based electrochemical sensor Figure 1

Effect of Electrolyte Composition over CO2 Reduction

The rapid utilization of fossil fuels escorted by an excess of CO2 emissions has led to global energy and environmental crisis. Therefore, the necessity for a clean, renewable and sustainable source of energy is a growing concern for the present and future society. In this regard, economically viable CO2 reduction would be a critical turnover in research, as it has the potential to fulfil a substantial need for clean energy. However, even though many efforts have been done in this field, there is still room for improvements concerning efficiency, material stability, and catalytic enhancement in regard of kinetics and selectivity. Herein, we provide the experimental proof for enhancement of the CO2 reduction efficiency and selectivity from the SEI (semiconductor-electrolyte interface) side through the use of carbonates, borates, sulphates and alkali cations as the electrolyte as well as an overview of the latest developments on Cu2O based PEC CO2 reduction for solar fuel production. Cu2O is a low-cost semiconductor and one of the most promising candidates for PEC CO2RR. However, its stability and performance is still unsatisfactory, thus the CO2 reduction products vary from one investigated system to another, such as: CH3OH, CO, HCOOH, CH3COOH, and CH3CH2OH. Moreover, the instability of Cu2O causes it, to be rarely used for the routine CO2 reduction reaction. In this paper, we use a very facile electrodeposition method, which offers a high level of reproducibility and the possibility of using a new electrode in each experiment, in order to focus our efforts on following the phenomena occurring in the double layer during the photocatalytic run. In this way, we were able to correlate the final CO2RR performance with a reorganization of the cations and anions near the photocatalyst surface. It is shown in the literature that factors such as: carbonate concentration, local pH, the presence of alkali metal cations, the geometry of the anionic group, CO2 solubility, conductivity, as well as pH changes along with the number of H+ in the electrolyte, play a significant role in regulating the partial CO2RR current. In this paper, we would like to shed new light on the influence of the electrolyte composition, cation-anion interaction and local reaction environment around the catalyst on the performance of CO2RR. We found out that the specific interaction between the alkali cation and the anionic group of particular geometry contributes to the formation of a kind of a “rigid layer” within the double diffusion, close to the photocatalyst surface layer, which accounts more for an apparent CO2RR current than the decrease in the finite Warburg element, which is a central key parameter for the diffusion coefficient values. The effectiveness of the strength of the cation-anion interaction in the formation of the “rigid layer” around the photocatalyst surface is found to increase the PEC CO2RR performance. Elucidating this mechanism provides useful information for creating further experimental design and the new pathways for addressing highly efficient PEC CO2RR systems. The authors have noticed a significant knowledge gap in the existing literature, as no prior publications have delved into the concurrent and combined impact of both cations and anions on PEC CO2RR. In this pioneering publication, we present the inaugural investigation of this this intricate phenomenon.

Magnetic Field Mapping-Based Battery Management System (BMS) for Lead Acid Application

Lead Acid Batteries (LAB) are a widely used technology in Energy Storage Systems (ESS) due to their abundant and low-cost materials, non-flammable water-based electrolyte, and high recyclability rate. The main applications for LABs are in mobility, data centers, and telecommunications. According to the Consortium of Battery Innovation (CBI), the market for lead acid batteries is projected to increase 150 GWh between 2025 and 2030. Therefore, it is fundamental to identify emerging failure modes in LABs in ESS systems to reduce battery degradation and to extend the use life.An important failure mode in flooded LABs is acid stratification. This research explores H+ concentration changes in H2SO4 (sulfuric acid) electrolyte as a correlation of acid stratification. The objective is to develop a non-invasive, non-destructive, and accurate real-time battery monitoring system. The Magnetic Field Probing (MFP) technique, popular in the medical imaging field, shows a promising solution for ESS performance evaluation. This technique can measure induced magnetic field changes based on variation in H+ concentration in the cell during cycling. See Figure. 1 (a). MFP provides early onset notification of stratification in flooded LABs with capability to discern other failure modes in non-flooded lead batteries.A set of experimental trials measured pH and magnetic field variation of H2SO4 electrolyte. See Figure. 1 (a). The preliminary results demonstrated changes in electrolyte pH due to possible stratification. See Figure. 1 (b). A correlation between the output voltage resulting from the interaction of the induced magnetic field and the changes in the electrolyte concentration was found. See Figure 1(c) The optimal AC input frequency maximizes the induced magnetic field response. The value found for optimal AC input frequency was 32kHz, which depends on the physical properties of the magnetic field inductors (air core solenoid coils). The experimental results showed and concluded that the induced magnetic field across the tested cell is also inversely proportional to the distance between coils attached to the cell.Further research involves the use of magneto-resistors to establish a magnetic field mapping in lead acid cells as they are being cycled. Magnetic field response is measured while lead acid cells are cycled from 100% to 20% state of charge range. In the future, this study will provide insights and findings to model and predict cell stratification in lead acid cells with electrochemical computational simulations.Keywords: Energy storage systems, lead acid batteries, acid stratification, magnetic field, non-invasive method Figure 1

Enabling Rhenium Electrodeposition in Water-in-Salt Electrolytes through Isolated Anodic Reactions

Perfluorosulfonic Acid (PFSA)/Polytetrafluoroethylene (PTFE) copolymer and cation-exchange membranes were used to elongate the use water-in-salt electrolytes for rhenium electrodeposition. Water-in-salt electrolytes are a common technique used to minimize the amount of free water in solution by including high concentrations of salts, thus solvating the water molecules and lowering activity of the solution. This expands the electrochemical window in which deposition is possible and minimizes unnecessary hydrogen evolution reactions (HER) in the electrodeposition system by reducing available protons.Lithium chlorine (LiCl) is a common salt for this purpose due to low costs. However, in the LiCl electrolyte, the necessary oxygen evolution reaction (OER) competes with chlorine evolution, which increases water activity and is visually identifiable with a color change from clear to yellow. When chloride ions are depleted, further deposition is no longer possible, and the electrolyte breaks down.A solution to this issue is using membranes to isolate the anode and cathode, thus preventing the chlorine evolution reaction from occurring. Since rhenium is a system with a small electrochemical window, possible oxide intermediates, and an overpotential for hydrogen evolution, the system requires the use of a stable water-in-salt electrolyte for elongated deposition.In this experiment, three membranes were examined to compare the impact on rhenium depositions in an H-cell. To compare the impact of each membrane, the change of pH of the DI side of the H-cell was monitored across time alongside the volume changes on both sides of the H-cell as a function of time due to LiCl inclusion. The quality and thicknesses of the coatings was examined by SEM as well as the impact on the morphologies of the rhenium of the deposits between each of the membranes.

Highly selective and sensitive potentiometric determination of favipiravir in COVID-19 antiviral drug formulations

In this study, a novel all-solid-state electrochemical sensor based on favipiravir-tetraphenylborate (FAV-TPB) electroactive material was developed and reported for FAV’s highly selective and sensitive potentiometric determination in COVID-19 antiviral drug formulations. All-solid-state FAV selective sensor was fabricated by mixing and properly pressing FAV-TPB, graphite (G), multi-walled carbon nanotube (MWCNT), and paraffin oil (PO). In order to obtain the best sensor response, the sensor component ratios were optimized. The most satisfying response characteristics was obtained with the sensor composition FAV-TPB:G:MWCNT:PO in the ratio 32.5:42.5:5:20 (w/w %). The developed sensor displayed a wide linear near-Nernstian response to FAV over the concentration of 1.0 × 10−6 − 1.0 × 10−1 molL−1 with a slope of 53.6 ± 1.4 mV (R2 = 0.9997). The detection limits of the sensor was calculated as 6.0 × 10−7 molL−1, respectively. The dynamic response time of the sensor was 7 s, and the sensor exhibited fairly reproducible potentiometric responses. In the pH range of 6.0–8.0, the sensor’s potential response was not affected by the pH change of the test solutions. The improved sensor had a wide temperature tolerance, and its response remained unchanged in the 10–40 ℃ temperature range. The interference effect of some chemical and biological species was evaluated by the matched potential method and separate solution method. The sensor worked stable for 12 weeks without any considerable change in its potential response. The analytical applications of the sensor were successfully carried out with the potentiometric titration of FAV with sodium tetraphenylborate solution and also the direct determination of favipiravir in COVID-19 antiviral drug formulations.

(Invited) Graphene Oxide As an Additive for Ni-Fe Electrodeposition

In contrast to graphene, graphene oxide (GO) is readily disperse in aqueous electrolytes and can be reduced along with nickel and iron metal ions. While others had incorporated graphene in Ni-Fe deposits, no previous studies have addressed the role of GO particles on metal deposition. Ni-Fe is characterized by the anomalous codeposition behavior where there is a tendency of more Fe to be deposited than Ni even though there is an excess of Ni ions in the electrolyte. This behavior has been modeled assuming adsorbed intermediates. Here, the influence of GO on the deposit composition, structure and anomalous codeposition effect is investigated. The deposits were galvanostatically electrodeposited from a boric acid-sulfamate electrolyte at pH 2 containing commercial graphene oxide platelets. Two different cell configurations were examined:1) a rotating cylinder electrode (RCE) and 2) a copper mesh. The rotating cylinder as a working electrode was used in order to investigate mass transport. The copper mesh working electrode was placed in close contact to a flat bottom pH probe in order to examine the local pH change. The addition of GO to the electrolyte had an effect on the deposit composition and the local pH change (Fig 1). The deposit composition had either more Ni or remained the same compared to an electrolyte without GO on the RCE electrode at electrode rotation rates of 372 and 1000 rpm (Fig 1 (a) and (b)). The larger Ni content in the deposit was due to an enhanced Ni partial current density in the presence of GO. The local pH during the deposition on the mesh electrode with vigorous electrolyte stirring increased the local pH (Fig 1(c)). The composition behavior is similar to the results from the RCEs, with higher Ni content in the presence of GO. The local pH increase when GO was present is considered a factor that drives the enhanced Ni content, that may be a consequence of changes in adsorbed hydrogen. GO was not incorporated into the deposit; however, it had a dramatic effect on the morphology. There was less micro-cracks when GO was present in the electrolyte suggesting less adsorbed hydrogen. Thus, GO influenced the adsorbed intermediates making the electrodeposition less anomalous and having less cracks. Acknowledgement: This work was supported in part by the AESF Foundation. Figure 1. The influence of GO in the electrolyte during Ni-Fe electrodeposition (a) composition on a RCE, rotating rate (a) 372, (b)1000 rpm and (c) local pH measurements on a mesh electrode under vigorous stirring, 30 mA/cm2. Figure 1

Intelligent Biopolymer-Based Films: Promising New Solutions for Food Packaging Applications.

The development of biopolymer-based films represents a promising direction in the packaging industry that responds to stringent needs for sustainability, reducing the ecological impact. Traditional fossil-derived polymers present major concerns because of their long decomposition time and their significant contribution to the pollution of the environment. On the contrary, biopolymers such as chitosan, PVA, and PLA offer viable alternatives. This study aimed to obtain an innovative pH indicator for smart packaging using a synthetic non-toxic anthocyanin analogue dye incorporated in bio-based films to indicate meat freshness and quality. The pH-responsive color-changing properties of the dye make it suitable for developing intelligent films to monitor food freshness. The obtained polymeric films were characterized by FT-IR and UV-VIS spectroscopy, and their thermal properties were assessed using thermogravimetric methods. Moisture content, swelling capacity, and water solubility of the polymeric films were also evaluated. The sensitivity of the biopolymer-flavylium composite films to pH variations was studied in the pH range of 2 to 12 and noticeable color variations were observed, allowing the monitoring of the meat's quality damage through pH changes. The pH-responsive films were applied directly on the surface or in the proximity of pork and chicken meat samples, to evaluate their colorimetric response to fresh and spoilt meat. This study can be the starting point for creating more durable packaging solutions leading to a circular economy.

Role of Ammonia in Aerosol Liquid Water, pH, and Secondary Inorganic Aerosols Formation at an Ammonia-rich City in Changzhou

Ammonia （NH3） is an important alkaline reactive nitrogen, which, as a precursor of fine particulate matter, raises public health issues. In this study, online NH3, SO2, NO2, PM2.5, and its water-soluble inorganic ions were detected to deduce the influence of NH3 on aerosol liquid water content （AWC） and aerosol pH, including the formation of water-soluble secondary ions in PM2.5 in winter in Changzhou, an ammonia-rich city in the Yangtze River Delta area in winter. The results showed that NH4+ mainly existed in the form of NH4NO3 and （NH4）2SO4, and the remaining NH4+ existed as NH4Cl. Owing to the NH3-NH4+ buffer system, the aerosol pH values were found at 4.2 ± 0.4, which was positively correlated with the NH3 content. The aerosol pH value variation narrowed with the increase in PM2.5 concentration and tended to be between 4 to 5. AWC increased exponentially with the increase in humidity and SNA content, among which NH4NO3, （NH4）2SO4, and NH4Cl contributed 58.5%, 18.4%, and 8.3%, respectively, due to their hygroscopicity. Aerosol pH, AWC, and NH3-NH4+ conversion promoted the gas-to-particle conversion of SO2 and NO2. In Changzhou, rich NH3-NH4+ were found to maintain relatively high pH values, push up AWC, and promote the heterogeneous reaction of SO2, whereas NO3- generation was dominated by a homogeneous reaction, which was accelerated by NH3. According to the simulation results, relatively noticeable changes in aerosol pH and AWC could be found by the reduction of up to 30% of NH3.