pH Variation Research Articles

Reactions of Diphenylamine with OH Radicals in the Environment: Theoretical Insights into the Mechanism, Kinetics, Temperature, and pH Effects.

Diphenylamine (DPL) has been widely utilized in industrial chemicals, but its degradation by HO• radicals in the environment has not been fully studied yet. The present study uses quantum chemical calculations to evaluate the reaction of DPL with HO• radicals in atmospheric and aqueous environments. The results showed that, in the atmosphere, the diphenylamine reacted with the HO• radical rapidly, with an overall rate constant of 9.24 × 1011 to 1.34 × 1011 M-1 s-1 and a lifetime of 0.17 to 1.55 h at 253-323 K. The calculated overall rate constant in water (koverall = 1.95 × 1010 M-1 s-1, pH = 3-14) is in excellent agreement with the experimental value (koverall = 1.00 × 1010-1.36 × 1010 M-1 s-1). The HO• + DPL reaction in water could occur following the hydrogen transfer (15.4%), single electron transfer (41.6%), and radical adduct formation (41.7%) mechanisms, clarifying that addition products were not exclusive products. Nevertheless, variations in temperature and pH within aqueous environments had an impact on the mechanisms, kinetics, and degradation products of the reaction of DPL with HO• radicals.

Electrochemical Determination of Tinidazole and Brucine Using Poly (l‐Glutamic Acid) Modified Carbon Nanotube Paste Electrode

AbstractThis study developed an electrochemical method for the selective and sensitive detection of Tinidazole (TZ) by modifying a bare carbon nanotube paste electrode (BCNTPE) with electrochemically polymerized l‐Glutamic acid (P(L‐GA)/MCNTPE). The modified carbon nanotube paste electrode (MCNTPE) achieved optimal detection with an irreversible peak in a 0.2 M phosphate buffer solution (PBS) at pH 3.5. Characterization of both the P(L‐GA)/MCNTPE and BCNTPE was carried out using techniques such as scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and linear sweep voltammetry (LSV). The sensor effectively identified possible interferences from different metals and organic compounds, with scan rate studies indicating that the reaction was controlled by diffusion. The effects of pH and concentration variations were also thoroughly investigated. The active surface area of the P(l‐GA)/MCNTPE and BCNTPE were found to be 0.471 cm2 and 0.217 cm2 respectively. The P(l‐GA)/MCNTPE displayed excellent electrochemical properties, with a limit of detection (LOD) of 0.06 µM and a limit of quantification (LOQ) of 0.2 µM, along with good reproducibility, repeatability, and stability. This study presents a P(l‐GA) MCNTPE that significantly enhances the sensitivity and selectivity for simultaneous detection of TZ and bare carbon nanotube (BCN). The improved electroactive surface area and electron transfer dynamics demonstrate its potential for practical applications in pharmaceutical analysis.

Production of bacteriocin-like inhibitory substance (BLIS) by Staphylococcus spp. isolates from dogs.

In the present study, 39 canine isolates of Staphylococcus spp. were tested for antimicrobial substance (AMS) production. Seven AMS producers were identified, whose products exhibited a non-acidic character and a proteinaceous nature, therefore being considered bacteriocin-like inhibitory substances (BLIS). The producer strains of BLIS P1, P16 and I3 showed a broad spectrum of antimicrobial activity. Human, veterinary and plant pathogens, such as Listeria monocytogenes, Klebsiella pneumoniae, Staphylococcus spp. and Clavibacter michiganensis, were among the inhibited micro-organisms, suggesting the potential biotechnological application of these peptides. MALDI-TOF mass spectrometry and 16S rDNA sequencing identified the producer strains of BLIS P1, P16 and I3 as Staphylococcus pseudintermedius P1, Staphylococcus schleiferi P16 and Staphylococcus pseudintermedius I3. The plasmid profile of these strains suggests that the BLIS production is linked to biosynthetic genes located on plasmids. PCR analyses revealed that BLIS P1, P16 and I3 are different from 11 staphylococcins already described in the literature and that their genomic DNAs do not carry the most prevalent staphylococcal enterotoxin genes. The highest levels of BLIS production were achieved after 18-24h of growth of the producer strains in TSB medium. Moreover, BLIS P1 and I3 exhibited high resistance to temperature and pH variations, and BLIS P16 maintained 100% of its activity in almost all conditions tested. The characteristics associated with BLIS P1, P16 and I3 described in this work encourage further investigation of these substances, in addition to this study being the first report of BLIS production by a strain of S. schleiferi.

Ceragenins Prevent the Development of Murine Vaginal Infection Caused by Gardnerella vaginalis

Background/Objectives: Bacterial vaginosis (BV), an infection caused primarily by Gardnerella vaginalis, is the most prevalent vaginal infection. Although BV is often characterized by an asymptomatic course, it can lead to considerable health complications. Currently, BV therapy choices are limited, and available treatments are complicated by concerns about antibiotic resistance. Ceragenins, which together comprise an innovative class of low molecular-weight, cholic acid-based antibacterial agents, have emerged as potential alternatives to conventional treatments. Methods: This study investigates (i) the antibacterial activity of ceragenins against G. vaginalis in in vitro experimental settings at varied pH, and (ii) the effectiveness and anti-inflammatory properties of CSA-13 in a G. vaginalis-induced bacterial vaginosis animal model. Results and Conclusions: We demonstrate that ceragenins, particularly CSA-13, maintain their antibacterial efficacy throughout pH range of 4.5–7, with the highest activity observed at neutral pH (7.0). Additionally, in an animal model, beneficial effects of ceragenins are attributed to anti-inflammatory properties of these compounds, making these compounds promising agents as potential new treatment options against G. vaginalis-associated vaginal infections.

Investigating the self-assembly of pH-sensitive switchable diamine surfactant using sum frequency generation spectroscopy and molecular dynamics simulations.

The responses of the N-alkyl diamine groups to variations in pH affect their conformations and surface activities, making them relevant to applications relying on interfacial interactions, such as controlled emulsification and mineral flotation. An in-depth understanding of interfacial self-assembly is crucial. Herein, a molecular-level study was performed to investigate the adsorption and self-assembly of N-dodecylpropane-1,3-diamine (DPDA) at the air-water (A/W) interface using sum frequency generation (SFG) spectroscopy and molecular dynamics (MD) simulations. The SFG spectra of DPDA, acquired under three pH conditions, suggest that the protonation of the DPDA diamine group influences the alkyl chain arrangement at a varying degree at the A/W interface. Analysis of the di-cationic DPDA SFG spectrum at a low pH showed fewer gauche defects at low concentration, as indicated by the relatively higher intensity ratio (ICH3SS/ICH2SS) of 18.1 ± 0.6. The density profiles from MD simulations at different surface areas per molecule and pH conditions, showing varying degrees of packing, support the observation of gauche defects in SFG. With MD simulation, the radial distribution factor for di-cationic species has the highest probability of forming hydrogen bonds compared to mono-cationic and non-ionic species. These g(r) probability results conform with observations obtained from SFG spectroscopy, where we observed a strong hydrogen bond interaction at low pH conditions with di-cationic species, forming tetrahedrally arranged water molecules at the A/W interface. Overall, comprehensive insights will facilitate the visualization of alkyl diamines and their potential derivatives at the A/W interface, enabling a better understanding of their behavior across various applications.

Theoretical and Experimental Study of the Stability of Thiamethoxam Under Different Environmental Conditions

The neonicotinoid insecticide thiamethoxam (TMX) is widely applied in agriculture, owing to its high spectrum of target pests. Its frequent use contributed to its accumulation in the environment, mainly in water; therefore, its natural degradation mechanisms are relevant to understand the physicochemical factors that can accelerate its decomposition. So, this study evaluated the stability of TMX against variations in pH, temperature, and exposure time to solar radiation, with the purpose of assessing the natural mechanisms of its degradation in water. Further, simulations of the reaction mechanisms at the molecular level were performed. It was observed that the degradation of TMX in the environment is favored by its exposure to solar radiation for several days and in more acidic pH conditions. However, TMX degradation did not result in reduced ecotoxicity. Basic pH values also help in the degradation of TMX, but by a lower percentage than that in an acid medium. Although exposure of TMX to solar radiation promotes heating of the compound, the isolated effect of thermal energy (temperature) is not sufficient for its degradation. The computer simulations showed the regions with higher electron densities and that the TMX structure is stable, preventing the bonds from breaking with increasing temperature, up to 60 °C. The HO− and H3O+ ions do not interact significantly with the molecule to the point of modifying its structure. With solar radiation, an electron can change to the excited state, contributing to TMX degradation due to a triplet configuration that allows it to react with the ions in the solution. In this way, the present work contributed to jointly present a theoretical and experimental study of the forms of natural degradation of the TMX contaminant.

The Productive and physico-chemical performance at two seasons of the year in trout (oncorhynchus mykiss)

The objective of the research was to evaluate the productive and physicochemical performance of trout (Oncorhynchus mykiss) in two seasons of the year. The months of April-June for the rainy season and July-September for the dry season in the Junín region of Peru were considered. The productive performance variables were: length, live weight, carcass weight and yield; on the other hand, the physicochemical variable (pH, water retention, humidity, ash, ethereal extract and protein). The results indicate that no differences (p>0.05) were found between the rainy and dry seasons for: length (cm), moisture (%), ash (%), ethereal extract (%) and protein (%). On the contrary, differences (p<0.05) were found between the rainy and dry seasons for live weight (g) with 239.37 g and 186.30 g respectively, as well as differences for carcass weight (g) in the rainy (186.30 g) and dry (140.77 g) seasons; likewise, differences were found for carcass yield (%), with 88.17 % and 86.89 % for the rainy and dry seasons, respectively. It is evident that in the rainy season there is an increase in their productive behavior. In terms of physicochemical performance, both seasons do not influence the chemical characteristics

Assessing the mobility of Zn, Pb and Ni during the weathering of Nkana smelter copper slag, Zambia

Mine slag dumps could be point-sources of possible pollutants to the surrounding water and soils. The purpose of this study was to investigate the leaching behavior of zinc, lead and nickel from Nkana copper slag dump of Kitwe in Zambia. To assess the toxicity and hazardous nature of the slag, Bath Leaching EN 12,457–2:2002, Toxicity Characteristic Leaching Procedure (TCLP) and Synthetic Precipitation Leaching Procedure (SPLP) were employed. The results from these techniques revealed that the copper slag was inert in the open or natural environment. Sequential extraction analysis was conducted to analyze the fractionation of the zinc, lead and nickel using a seven-step procedure. The sequential extraction analysis showed that the 3 metals were predominantly present in the residual fraction. The risk assessment code (RAC) showed that zinc and lead's mobility could pose an environmental risk categorized as low risk, with RAC values of 1.31 % and 1.50 %, respectively. Nickel's mobility fell within the no-risk category with a RAC of 0.32 %. Additionally, the effect of pH, particle size and contact time on the release of the 3 metals were investigated. The results showed that the highest concentrations of zinc and nickel were observed for longer period of exposure (>33 days), in acidic environments (pH 2.2 and pH 3.0), for particle size distribution (<75 μm). However, lead leaching was not affected by the variation of pH or particle size distribution but mostly by duration of exposure. X-ray diffraction (XRD) analysis revealed that diopside (CaMgSi2O6) and quartz (SiO2) constitute the primary phases within the sample. It is recommended to limit the exposure of slag material to acidic environments and minimize the fragmentation of the slag into finer particles as these conditions would promote increased release of zinc, lead and nickel to the surrounding environment.

Widening the stimuli-responsiveness of aqueous biphasic systems by changing the ionic liquid cation basicity.

Herein we demonstrate the formation of new stimuli-responsive aqueous biphasic systems (ABS), able to respond simultaneously to temperature and pH, or just to one stimulus, therefore allowing the design of more sustainable separation processes. This dual behavior is achieved with ABS formed by mono or dicationic protic ionic liquids as phase-forming components, being defined by the ionic liquid cation chemical structure or its basicity. While ABS comprising monocationic ionic liquids only respond to the effect of temperature, systems comprising dicationic ionic liquids are simultaneously affected by both temperature and pH variations. Dicationic ionic liquids are here identified as the key to unlock a double response to stimuli, which is due to the presence of two pKa values afforded by the cation. The reported findings contribute to increase the customizability of double stimuli-responsive ABS based on ionic liquids, whose development was up to date limited to ionic liquids bearing pH-responsive anions, opening the door towards the development of more sustainable separation processes.

In-situ imaging and time-resolved investigation of local pH in electrocatalytic CO2 reduction

Local pH near the catalyst surface exerts a substantial influence on both catalytic selectivity and activity in electrocatalytic CO2 reduction (CO2RR). While the investigation of local pH remains challenging in the aspect of in-situ imaging and monitoring. In this study, a novel lateral-type surface-enhanced Raman spectroscopy (L-SERS) system with a wide pH testing range from acidic to alkaline, is developed for the in-situ observation of local pH distributions with high spatial and temporal resolution during CO2RR. Excellent in-situ imaging of local pH near the catalyst surface is obtained, showing good consistency with simulation results. Besides, the gradual pH elevation and stabilization can be monitored via this time-resolved local pH investigation. This study presents a direct visualization of local pH distribution and variation at the Nernst layer during CO2RR, providing direct evidence in local pH for the feasibility of acidic electrolyte and offering theoretical guidance for optimizing CO2RR conditions.

Finite Element Analysis of Local pH Variations in Electrolysis with Porous Electrodes, Considering Water Self-Ionization.

A finite element model was developed to simulate ion fluxes and local pH changes within and around porous electrodes during the H2 evolution reaction (HER) in acidic electrolytes. This model is particularly characterized by its ability to simulate scenarios in which the local pH inside and near the cathode exceeds 7, even under bulk acidic conditions (e.g., pH = 1), by considering the self-ionization of water. Steady-state calculations using meshes with an appropriate spatial distribution inside and near the cathode revealed that the relationship between the local pH and the double-layer potential at the interface between the porous catalyst layer and the electrolyte domains changed notably when the local pH exceeded the threshold of 7. By comparing the fluxes of H+ and OH- ions at the interface and using the thickness of the catalyst layer as a variable, we determined that the presence of H+ ions within the pores or the supply of OH- ions from the pores to the interface was responsible for the characteristic change in the local pH observed for the porous electrode. The porous electrode model constructed in this study can potentially serve as a basis that can be extended to a wide range of electrolysis systems, including not only the HER, but also the reduction of CO2, H2O2, and O2, and even oxidation reactions such as the O2 evolution reaction.

Deciphering the Conformations of Glutathione Oxidized Peptide: A Comparative NMR Study in Solution and Solid-State Environments.

Glutathione (GSH) and its oxidized dimer (GSSG) play an important role in living systems as an antioxidant, balancing the presence of reactive oxygen species (ROS). The central thiol (-S-S-) bond in GSSG can undergo free rotation, providing multiple conformations with respect to the S-S bridge. The six titratable sites of GSSG, which are influenced by pH variations, affect these conformations in solution, whereas in solids, additionally crystal packing effects come into play. In view of differing reports about the structure of GSSG in literature, we have here conducted an extensive reexamination of its conformations using NMR, and contrasting results have been obtained for solution and solid state. In solution, the existence of more than one antiparallel orientation of the monomer unit with different hydrogen bonding schemes has been indicated by NOE and amide temperature coefficient results. On the other hand, in the solid-state, a 1H-1H double-quantum (DQ) to 13C single-quantum (SQ) correlation study has confirmed a parallel orientation, consistent with the reported X-ray crystal structure. Experimentally assigned solid-state NMR resonances have been validated using GIPAW calculations incorporated in the Quantum ESPRESSO package.

Comparison of passive and manual chlorination in small piped water networks in rural Ghana: Technical performance, ease-of-use, and cost

Chlorination is the most common water treatment method globally and leads to proven health benefits. Yet, many rural water supplies in low-income settings are unchlorinated, exposing consumers to waterborne diseases. Insufficient technical and financial capacity of water suppliers in low-resource settings are common barriers to more widespread chlorination. We conducted a case study of two approaches to chlorinate small piped water supplies− passive (inline) chlorination and manual chlorination− and compared their technical performance, ease-of-use, and costs in rural Ghana. Based on 685 water quality measurements across two piped networks over three months, both methods provided adequate free chlorine residuals (i.e., 0.2–2.0 mg/L) most of the time (71% for manual chlorination and 86% for passive chlorination). Follow-up measurements five months later revealed a decline in chlorine levels with the manual approach (47% in the target range) and an increase with the passive (inline) approach (100% in the target range). We observed large fluctuations in chlorine levels over time, particularly with inline chlorination, that pH, temperature, conductivity, and turbidity variations did not fully explain. Temporal changes in chlorine demand and/or inconsistently implemented protocols possibly contributed to these fluctuations. Inline chlorination scored higher for ease-of-use (85%) than manual chlorination (70%) but was less financially viable: it represented an 11% increase in operational expenses, compared to 4% for manual chlorination. Initial equipment and installation cost approximately 6,000 USD for inline chlorination and about 260 USD for manual chlorination. Our results highlight the tradeoffs between passive (inline) and manual chlorination. Although less favorable for ease-of-use, manual chlorination is more viable financially and can achieve comparable performance with strict dosing protocol adherence, suggesting this approach deserves similar consideration as passive chlorination when evaluating options for low-resource settings. Both methods are susceptible to changes in operator behaviors and require external oversight plus support for troubleshooting and recalibration.

Comparative treatment of textile dye wastewater with chemical coagulants and bacterial exopolysaccharides

Traces of chemical coagulants, such as alum, commonly used in wastewater treatment, remain in the water effluent and also result in secondary sludge that is difficult to treat. On the other hand, Extracellular Polymeric Substances (EPS) are safer and can be used as alternative bio flocculants. A study was hence done to compare the effectiveness of the treatment of Reactive Black 5 (RB5) textile wastewater with chemical coagulants and bacterial EPS. The jar test method was used to treat the wastewater with Alum and Polyferrous Sulphate (PFS) at varied pH (2–10) and respective dose concentrations. EPS was produced by bacteria isolated from cotton gin trash soil collected from Kitui ginnery in Kenya. EPS treatment was done at 30 °C for 72 h. EPS-producing bacteria isolates were identified by molecular analysis. The chemically and EPS-treated wastewater was analyzed for color, Total Dissolved Solids (TDS), and Chemical Oxygen Demand (COD). Respective color and TDS removal capacity by PFS and alum were (86.1% and 42.18%) and (85.1% and 69%) at their optimal conditions of (pH 7 and 100 mg/L) and (pH 7 and 140 mg/L). Similarly, PFS and alum reduced COD by 27.25% and 26.65%. Respective dye removal by YEAK2 −5 and YEPD K2 −2 EPS was 69.1% and 85.7%. However, YEPD K2 −2 and YEAK2 −5 EPS caused a respective rise of TDS by 40.14% and 67.17%. The respective reduction of COD by YEPD K2 −2 and YEAK2 −5 EPS was 56.25% and 54.24%. The chemically and EPS-treated wastewater met the National Environment Management Authority (NEMA) limits. The YEPD K2 −2 and YEAK2 −5 isolates were both identified as Bacillus sp. GC–MS and FTIR analysis results indicated that the two EPS were heteropolysaccharides composed of different sugar derivatives and hydroxyl as the main functional group. The results for treatment of the dye wastewater by Alum, PFS, and EPS were therefore comparable. The bacterial EPS bio flocculants can therefore serve as effective and cleaner substitutes to the alum and PFS chemical coagulants.

Kinetic features and mechanism of scorodite formation via multivalent iron source from arsenic-bearing solution

Arsenic-bearing wastes from non-ferrous metallurgy exhibit poor stability during long-term storage, and are transferred as pollutants to the atmosphere and groundwater, thereby, threatening human health and ecological security. Immobilising arsenic as scorodite crystals via a multivalent iron source (Fe(OH)3-FeSO4·7 H2O) is one effective approach for controlling arsenic pollution. However, the kinetic features and mechanisms of this method have not yet been revealed, thereby, necessitating further research. Herein, the kinetics of scorodite generation influenced by the initial pH, Fe/As ratio, Fe(III)/Fe(II) ratio, and reaction temperature were investigated. Prominent features included variations in the minimum pH, oxidation–reduction potential (ORP) platform, Fe/As ratio (1.0), and the delay or advance of scorodite generation. The complicated mechanism of scorodite formation can be divided into coordinated polymerisation, acidic Fe(OH)3 dissolution, polymer oxidation, Fe(II) oxidation, and scorodite crystallisation. The fast coordinated polymerisation of precursors ([Fe(H2O)4(H2AsO4)]nn+) in stage I resulted in a decrease in pH; Fe(OH)3@scorodite and Fe(H2O)2AsO4 basic units were formed via the oxidation of ionic Fe(III) in stage II. Furthermore, regular octahedral scorodite was generated from two sources: the crystallisation of Fe(H2O)2AsO4 basic units and Ostwald ripening of flaky scorodite from Fe(III)–As(V) precipitates at stage III. The Fe(II) in the polymers was mainly oxidised by ferric ions generated from the oxidation of ferrous ions via dissolved O2 from the oxygen gas. Fe(II) ions as carriers for transferring electrons from O2 to polymers. Scorodite formation was controlled by the oxidation of Fe(II) by oxygen gas. Overall, this study provides guidance for the effective immobilisation of arsenic wastes into scorodite via multivalent iron sources to eliminate arsenic pollution.

Are pools created when restoring extracted peatlands biogeochemically similar to natural peatland pools?

In the last 25 years, several degraded peatlands in eastern Canada have been restored toward their natural structure. Pools are common in natural peatlands and are important habitats for unique flora and fauna. Because of their ecological value, pools have been created in some restored peatland sites. Nevertheless, the biogeochemistry of created pools in a restoration context has seldom been studied. The objective of our study is to characterize the biogeochemistry of created pools from restored peatlands and compare them with natural pools along a chronosequence since their creation. We measured different biogeochemical variables (pH, concentrations of nitrogen (N), phosphorus (P), dissolved organic carbon (DOC), dissolved organic matter (DOM), base cations-calcium (Ca), sodium (Na), magnesium (Mg), and potassium (K)-and dissolved gases-methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O)-) in 61 pools distributed over seven peatlands in eastern Canada. The sites represent a range of conditions, from natural to restored peatlands with pools ranging from 3 to 22 years old. Created and natural pools had distinctive biogeochemistry, with created pools being generally less acidic (pH >5) and 2.5 times more concentrated in nutrients (N and P) than in natural pools. DOC, N, P, dissolved gases, and base cations concentrations were lower in natural pools than in created pools, and varied between created sites. The oldest created pools (age >17 years) tend to approach the biogeochemical characteristics of natural pools, indicating that created pools may, over time, provide habitats with similar conditions to natural pools. A return of created pools to a natural pool-like biogeochemistry could thus inform on the success of peatland restoration.

Impact of Plastic Mulching on Soil Properties and Heavy Metal Dynamics in Agricultural Systems: A Case Study from Manikganj, Bangladesh

This research study examines the impact of different types and sizes of plastics on various soil properties. Clay loam soil samples were collected from Paril village, Manikganj district, Bangladesh, and subjected to plastic incubation experiments. The plastics underwent 180 days of intense ultraviolet (UV) radiation to simulate natural sunlight degradation. The soil samples were mixed with three types of plastics (P1, P2, P3) and two sizes (1mm, 10mm) in individual pots, with and without the addition of zinc sulfate. The soil properties, including pH, total dissolved solids (TDS), available zinc, cation exchange capacity (CEC), nitrogen content, and total phosphorus, were analyzed using various techniques. The results indicate significant variations in pH and TDS values influenced by plastic size and type. The available zinc content differed among plastic types, and plastic size affected CEC values. Nitrogen content was influenced by plastic size, with smaller particles having a greater impact. Total phosphorus content varied with different plastic types. These findings contribute to our understanding of the potential effects of plastics on soil properties and highlight the need for further investigation into the underlying mechanisms.

C-H Functionalization of Poly(ethylene oxide) - Embracing Functionality, Degradability, and Molecular Delivery.

This study presents an organocatalytic C-H functionalization approach for postpolymerization modification (PPM) of poly(ethylene oxide) (PEO). Most of PEO PPM is previously processed at the end hydroxy group, but recent advances in C-H functionalization open a way to modify the backbone position. Structurally diverse carboxylic acids are attached to PEO through a cascade process of radical generation by peroxide and oxidation to oxocarbenium by tertiary butylammonium iodide. Attaching carboxylic acids yields a series of functionalize PEO with acetal units (2-5 mol%) in a backbone, which is not accessible via conventional copolymerization of epoxides. The optimized conditions minimizes the uncontrolled degradation or crosslinking from the highly reactive radical and oxocarbenium intermediate. The newly introduced acetal units bring degradability of PEO as well as delivery of carboxylic acid molecules. Hydrolysis studies with high molecular weight functionalization PEO (Mn = 13.0kgmol-1) confirm the steady release of fragmented PEO (Mn ∼ 2.0kgmol-1) and carboxylic acid over days and the process rate is not sensitive to pH variation between pH 5 and 9. The presented method offers a versatile and efficient way to modify PEO with potential energy and medical applications.

Using the Herschel-Bulkley Consistency Index to Characterise Complex Biopolymer Systems-The Effect of Screening.

The use of the consistency index, as determined from fitting rheological data to the Herschel-Bulkley model, is described such that it may yield systematic trends that allow a very convenient description of the dissipative flow properties of linear and branched (bio)polymers in general, both in molecular and weakly associated supramolecular solutions. The effects of charge-mediated interactions by the systematic variation of the ionic strength and hydrogen bonding by a systematic variation in pH, using levels that are frequently encountered in systems used in practice, is investigated. These effects are then captured using the associated changes in the intrinsic viscosity to highlight the above-mentioned trends, while it also acts as an internal standard to describe the data in a concise form. The trends are successfully captured up to 100 times the polymer coil overlap and 100,000 times the solvent viscosity (or consistency index). These results therefore enable the rapid characterization of biopolymer systems of which the morphology remains unknown and may continue to remain unknown due to the wide-ranging monomer diversity and a lack of regularity in the structure, while the macromolecular coil size may be determined readily.

Green synthesis of Oscimum Sanctum mediated silver nanoparticles to fabricate sensors for hydrogen peroxide detection

In this study, silver nanoparticles (Ag NPs) of an average size of ∼15 nm have been produced using the green synthesis technique with Oscimum Sanctum leaf extract. Further, these nanoparticles have been used to prepare electrodes for electrochemical sensors to monitor hydrogen peroxide. Hydrogen peroxide sensors have many applications in different sectors, such as medical, agriculture, and industry. The optical and structural characteristics of the Ag NPs have been investigated by UV–visible absorption spectroscopy and XRD patterns. Particle size, shape, and morphology of as-synthesized Ag NPs have been analyzed using transmission and scanning electron microscopic techniques. These nanoparticles were deposited onto an indium-tin-oxide glass substrate using the electrophoretic technique, which was used as an electrode to assess the electro-oxidation of Ag NPs by cyclic voltammetry. The sensitivity of the sensor has been estimated to be 4.16 µA/mM-cm2. The limit of detection of the sensor is estimated to be 40 µM within the linear range of 5–28 mM. The lattice parameter, interplanar spacing, and crystallite size of Ag NPs have been quantified and estimated against pH variation.