Neutral Solution Research Articles

Plasma-deposited reactive species assisted synthesis of colloidal zinc-oxide nanostructures

A surface-wave microwave discharge is applied to deposit reactive oxygen and nitrogen species (RONS) into the liquid subsequently used as a medium for laser ablation of a Zn metallic target. It is shown that during laser ablation in plasma-treated liquids the H2O2 concentration decreases, while in deionized water (DIW) significant H2O2 is produced. Meanwhile, the pH—initially adjusted by applying reductive metals—increases in the acidic liquids and decreases in the alkaline ones. During months of storage the pH of colloids stabilize around pH 6, which insures the long-term stability of RONS. It is demonstrated that in DIW metallic Zn NPs are created, which gradually oxidize during storage, while in the plasma-treated liquids ZnO NPs are produced with the mean size of 18 nm. In the alkaline plasma-treated liquid the NPs form large aggregates, which slows the dissolution of NPs. In the acidic and neutral solutions besides NPs nanosheets are also formed, which during storage evolve into nanosheet networks as a result of the dissolution of NPs. The band gap of the colloidal ZnO is found to decrease with the formation of aggregates and nanosheet networks. The ZnO NPs ablated in plasma-treated liquids exhibit a high-intensity visible emission covering the green-to-red spectral region. The photoluminescence spectra is dominated by the orange-red emission—previously not detected in the case of laser-ablated ZnO NPs and attributed to the interstitial Zn and oxygen sites—and the yellow emission, which can be attributed to the OH groups on the surface. It is shown that during months of storage, due to the dissolution of NPs and formation of nanosheets, the intensity of the visible emission decreases and shifts to the blue-green spectral region.

Meso-Brominated nitrosylcobinamides: Nitric oxide release and oxidation by dioxygen

This study explores the modification of nitrosylcobinamide, explicitly focusing on meso-bromination, and its impact on the dissociation rate of nitric oxide (NO). meso-Brominated aquahydroxocobinamide was efficiently synthesized from meso-brominated cyanocobalamin via hydrolysis, followed by decyanation step. Its reaction with Angeli’s salt produces meso-brominated nitrosylcobinamide (NOCbi-Br). NOCbi-Br exhibits stability in the presence of dioxygen comparable to that of the unmodified NOCbi in neutral aqueous solutions. However, in the presence of L-histidine the oxidation of NOCbi-Br by dioxygen is significantly slower than unmodified NOCbi, indicating potential differences in ligand affinities. Furthermore, the rate constant for NO release from NOCbi-Br was lower than that of unmodified NOCbi, suggesting that meso-bromination strengthens the Co(II)–NO bond. These findings underscore the utility of meso-modification in tailoring the properties of corrinoids as nitric oxide donors, with potential implications for therapeutic applications.

Al-water reaction generates metastable aluminum cluster ions and their use in advanced oxidation processes

Our previous work indicated that hydroxyl radicals (HO•) exist in the filtrate of Al + acid + H2O2 system. In this work, the behind mechanism was investigated in detail and a new catalyst for advanced oxidation processes (AOPs) was found for the first time. It was revealed that metastable hexacoordinated aluminum cluster ions ([Al(H2O)63+]*), which are produced by Al-water reaction, can be as direct catalyst and decompose H2O2 into HO• in a full pH range (2.5–12.0), and efficiently degrade and mineralize organic pollutants without precipitates. Of course, their catalytic activity in acidic aqueous solution is higher than that in neutral and alkaline solutions. Furthermore, [Al(H2O)63+]* cluster ions have an excellent recyclability and their catalytic efficiency for generating HO• and degrading phenol and bisphenol A (BPA) did not decrease significantly even the cycling number was up to ten. Meanwhile, [Al(H2O)63+]* cluster ions have a long lifetime and can keep their catalytic activity for more than three months under ambient condition. The present finding shows that Al3+ ions can be also as a cost-efficient catalyst for AOP technology.

Corrosion behavior and scratch performance of Al-WC nanocomposites

Corrosion behavior and scratch performance of Al-WC nanocomposites with varying wt% of WC are evaluated in this study. Liquid metallurgy-based stir-casting route is used for fabrication of the nanocomposites. Particles are distributed in the matrix as confirmed by EDAX (energy-dispersive X-ray) spectrum and XRD ( X-ray diffraction) analysis. The micro-hardness of nanocomposites increases with the increase of wt% of WC particles. Corrosion behavior is studied under different corrosive environments, viz., neutral, alkaline and acidic solution. Tafel plots and Nyquist plots are obtained under the neutral medium (3.5wt% NaCl aqueous solution), while only Tafel plots are obtained under 0.5M NaOH solution and 0.5M HCl solution. Among all three operating mediums, NaCl solution is the least corrosive for the composite. Corrosion rates under NaOH and HCl medium are high and values are very close to each other. The least amount of reinforcement, 0.5wt% of WC, yields the best corrosion resistance under the neutral solution. The corrosion resistance increases with the amount of reinforcement under alkaline and acidic mediums. From SEM (scanning electron microscope) images of the corroded surfaces, pitting corrosion is observed for Al-0.5%WC composite while exfoliation with deeper cracks is observed for composites with a higher amount of WC. Scratch performance is also evaluated for a load range of 5N to 20N. Scratch resistance increases with increase in wt% of nano-particles. Surfaces after scratching are characterized using optical microscope, SEM, and EDAX spectrum.

Electrochemical detection of hydroquinone as an environmental contaminant using Ga2O3 incorporated ZnO nanomaterial

The primary objective of this research endeavor is to develop a highly sensitive and selective electrochemical sensor for the accurate detection of hydroquinone (HQ), a prevalent environmental contaminant. To achieve this, we employed a novel nanocomposite consisting of Ga2O3-doped ZnO (Ga2O3.ZnO) as the active nanomaterial for fabricating a glassy carbon electrode (GCE). The structure and morphology of the Ga2O3.ZnO nanocomposite were rigorously analyzed using a diverse range of techniques to ensure its suitability as the sensing nanomaterial. This innovative sensor exhibits remarkable capabilities, enabling the detection of HQ across a broad concentration range, spanning from 1 to 11070 µM, in a neutral phosphate buffer solution. It boasts an exceptionally high sensitivity of 1.0229 µA µM−1 cm−2 and an impressive detection limit of 0.063 µM. Thanks to its exceptional sensitivity and specificity, this sensor can precisely quantify HQ levels in real-world samples. Moreover, its outstanding reproducibility, repeatability, and stability establish it as a dependable and resilient choice for HQ determination.

Efficient removal of Oxytetracycline antibiotic from aqueous media using UV/g-C3N4/Fe3O4 photocatalytic process

Residual pharmaceuticals in the environment are a class of emerging pollutants that endanger human health. Tetracycline’s family, including oxytetracycline (OTC), are known as one of the most produced and consumed antibiotics worldwide. The g-C3N4/Fe3O4 nanocomposite with high level of catalytic efficiency features suitable performance in water/ wastewater treatment. Therefore, in the present study, this nanocomposite was applied to remove the oxytetracycline from the aqueous environment. In this research study, g-C3N4/Fe3O4 nanocomposite (serving as catalyst) was initially synthesized by a simple hydrothermal method. The effect of key operating parameters such as initial solution pH, dose of catalyst, contact time and initial concentration of OTC in aqueous solutions was investigated under UV irradiation. In addition, COD and TOC tests, the kinetics and the effect of radical scavengers on the applied photocatalytic process were all evaluated. The maximum removal efficiency of OTC (99.8%) was achieved under the following conditions: neutral solution pH 7; catalyst dose, 0.7 g/L; and an initial OTC concentration of 5 mg/L. The data showed that the kinetics of the reaction followed the first-order model with R2 of 0.9755. The respective COD and TOC efficiency values for the applied photocatalytic process were determined to be 87 and 59%, respectively. In addition, the lowest removal efficiency of OTC was observed in the presence of tert-butanol radical scavengers, and OH radicals played a main role. The UV/g-C3N4/Fe3O4 photocatalytic process proved to be highly efficient for the removal of OTC antibiotic and could be potentially applied for the removal of other pollutants from aqueous solutions.

PHLIP-fused PD-L1 engages avelumab to elicit NK cytotoxicity under acidic conditions

Natural killer (NK) cells represent key player in immune surveillance to eliminate transformed or malignant cells. One of mechanisms of action of NK cells is antibody-dependent cell-mediated cytotoxicity (ADCC) by recognizing tumor antigens on the surface of cancer cells. However, the heterogeneity of tumor antigens and the scarcity of membrane surface targets significantly restrict this strategy. Recently, we constructed a new cargo by tethering a low pH insertion peptide (pHLIP) to the C terminus of the ectodomain of programed death ligand-1 (PD-L1) and demonstrated its ability to modulate immune responses. Herein, the potential application of PD-L1-pHLIP in cancer therapy was determined. pHLIP tethering had no effect on the binding capacity of PD-L1 protein to an anti-PD-L1 antibody (i.e. avelumab). Association of pHLIP rendered PD-L1 segment display on the surface of cellular membrane in the acidic buffer instead of the neutral solution. Importantly, plate-coated or beads-coupled PD-L1-pHLIP enable robust activation and expression of cytotoxic mediators of NK cells via engaging avelumab. Overall, this work provides proof of concept that recombinant PD-L1 protein decorated on the cellular membrane driven by pHLIP in combination with appropriate monoclonal antibody has potentials to elicit NK cytotoxicity, which may represent a novel and promising therapeutic avenue in cancer.

First Application of Non‐Metallic A2B Type Silicon Corrole Complexes in Electrocatalytic Hydrogen Evolution

AbstractIn this study, we have successfully synthesized two non‐metallic‐based silicon corrole complexes (F10C−Si, F10C−CN−Si) and used them as HER electrocatalysts for the first time. Electrochemical studies indicate the electrocatalytic HER may go via EE‐CEEC (E: electron transfer step, C: chemical step) pathway. Notably, it can be seen that the introduction of electron‐withdrawing cyano group on the meso‐phenyl of the corrole macrocycle may enhance the catalytic activity of silicon corrole complexes. In DMF with TsOH as the proton source, F10C−CN−Si exhibits a turnover frequency (TOF) of 331.48 s−1 and a high catalytic efficiency (C.E) of 1.29. Furthermore, the catalytic prowess of the silicon corrole complexes extends to neutral aqueous solution, with F10C−CN−Si achieving a TOF of 52.72 h−1 at an overpotential of 1188 mV. This study extends the application of non‐metallic‐based silicon corrole molecular catalysts in the electrocatalytic HER field.

An Aqueous All‐Quinone‐Based Redox Flow Battery Employing Neutral Electrolyte

AbstractRedox flow batteries (RFBs) are considered as promising candidates for large‐scale energy storage. However, traditional RFBs based on toxic metal ions have deficiencies in resource utilization and environmental protection. Considering the corrosiveness of acidic and alkaline electrolytes and sustainability of energy storage devices, neutral aqueous organic redox flow batteries (AORFBs) have more development prospects. Herein, an AORFB is reported, using 9,10‐anthraquinone‐2,7‐disulfonic salt (2,7‐AQDS) and 1,4‐dihydroxyphenylsulfonate potassium (HQS) as negative and positive electroactive materials, respectively. It is found that the anions in the neutral solution further affected the solubility and kinetics of the electroactive materials by affecting the hydrogen bond in the solution, and the Na2SO4 solution showed the optimal comprehensive performance. Therefore, an all‐quinone AORFB employing neutral Na2SO4 electrolytes with a cell voltage of 0.9 V is constructed, which presented a capacity utilization of 70.1% and delivered stable cycling performance at 60 mA cm−2. This work designs an innovative neutral all‐quinone AORFB and points out how anions affect the properties of the electrolyte by affecting hydrogen bonds within the solution. These findings open a new avenue for the design and application of neutral all‐organic aqueous RFBs.

Colloid Mill-Assisted Ultrasonic-Fractional Centrifugal Purification of Low-Grade Attapulgite and Its Modification for Adsorption of Congo Red.

Attapulgite (APT) is widely used in wastewater treatment due to its exceptional adsorption and colloidal properties, as well as its cost-effectiveness and eco-friendliness. However, low-grade APT generally limits its performance. Here, a colloid mill-assisted ultrasonic-fractional centrifugal purification method was developed to refine low-grade APT. This process successfully separated and removed impurity minerals such as quartz and dolomite from the raw ore, resulting in a refined APT purity increase from 16.9% to 60% with a specific surface area of 135.5 m2∙g-1. Further modifying of the refined APT was carried out through the hydrothermal method using varying dosages of cetyltrimethylammonium chloride (CTAC), resulting in the production of four different APT adsorbents denoted as QAPT-n (n = CTAC mole number) ranging from 0.5 to 5 mmol. Using Congo red (CR) as the target pollutant, the QAPT-5 sample exhibited the best adsorption capacity with the maximum quantity of 1652.2 mg∙g-1 in a neutral solution at 30 °C due to the highest surface charge (zeta potential = 8.25 mV). Moreover, the QAPT-5 pellets (~2.0 g adsorbent) shaped by the alginate-assisted molding method removed more than 96% of 200 mL aqueous solution containing 200 mg∙L-1 CR and maintained this efficiency in 10 adsorption-elution cycles, which exhibited the promising practical application.

A comparative study on NH3/H2 and NH3/CH3OH combustion and emission in an optical SI engine

Ammonia is an attractive carbon-free fuel but suffers from poor combustion characteristics and heavy emissions. Green hydrogen and methanol are recognized as the most promising combustion promoters for enhancing ammonia reactivity in pursuit of a carbon–neutral solution. Nonetheless, a comparative study on ammonia combustion and emissions, incorporating hydrogen and methanol enrichment, is currently absent under actual engine conditions. In this work, the combustion performance, visualized flame characteristics, and pollution emissions of ammonia were investigated in an optical engine, allowing for low-level hydrogen and methanol enrichment, specifically at energy ratios of 5%, 10%, and 15%. We have identified the crucial role of hydrogen and methanol enrichment in enhancing various aspects of ammonia engine performance, including thermal efficiency, combustion stability, flame initiation and propagation, and nitrogen-based emissions. Specifically, hydrogen enrichment demonstrates a more pronounced effect on reducing cyclic variations, whereas methanol enrichment exhibits a greater influence on increasing thermal efficiency, manifesting improved controllability in combustion phasing. Combustion visualizations show the contribution of hydrogen enrichment to the formation process of the initial flame kernel, which is reflected as a lower cyclic variation from a macroscopic perspective, and meanwhile, methanol enrichment features a stronger acceleration effect during the turbulent flame propagation process. Furthermore, the quantification of flame response to turbulence is solved and observed much higher effects for NH3/CH3OH blends than for NH3/H2 blends, indicating a distinctly different mechanism of facilitation by methanol enrichment. Regarding nitrogen-based emissions, both hydrogen and methanol enrichment lead to a substantial reduction in NH3 slip and N2O emissions, consistent with observed variations in combustion stability. However, methanol enrichment induces noticeable decreases in NOx emissions, while hydrogen enrichment exhibits an opposing trend. The present study demonstrates the beneficial impacts of hydrogen and methanol enrichment on improving ammonia combustion and emissions, with the underlying reason correlated to flame dynamics and thermochemical interactions.

Pyrite from acid mine drainage promotes the removal of antibiotic resistance genes and mobile genetic elements in karst watershed with abundant calcium carbonate

More information is needed to fully comprehend how acid mine drainage (AMD) affects the phototransformation of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in karst water and sewage-irrigated farmland soil with abundant carbonate rocks (CaCO3) due to increasing pollution of AMD formed from pyrite (FeS2). The results showed FeS2 accelerated the inactivation of ARB with an inactivation of 8.7 log. Notably, extracellular and intracellular ARGs and mobile genetic elements (MGEs) also experienced rapid degradation. Additionally, the pH of the solution buffered by CaCO3 significantly influenced the photo-inactivation of ARB. The Fe2+ in neutral solution was present in Fe(II) coordination with strong reducing potential and played a crucial role in generating •OH (7.0 μM), which caused severe damage to ARB, ARGs, and MGEs. The •OH induced by photo-Fenton of FeS2 posed pressure to ARB, promoting oxidative stress response and increasing generation of reactive oxygen species (ROS), ultimately damaging cell membranes, proteins and DNA. Moreover, FeS2 contributed to a decrease in MIC of ARB from 24 mg/L to 4 mg/L. These findings highlight the importance of AMD in influencing karst water and sewage-irrigated farmland soil ecosystems. They are also critical in advancing the utilization of FeS2 to inactivate pathogenic bacteria.

Enhancing output current in degradable flexible piezoelectric nanogenerators through internal electrode construction

Conventional piezoelectric nanogenerators (PNGs) face challenges in terms of degradation and reusability, which have negative environmental implications. On the other hand, biocompatible and degradable piezoelectric materials often exhibit lower piezoelectric response. In this study, potassium sodium niobate (KNN) powder and the biodegradable polymer poly(ε-caprolactone) (PCL) were used to fabricate piezoelectric composite films through solution casting. By constructing staggered electrodes, the total polarized charges quantity is increased, achieving a larger current output. The three-unit PNG (3-PNG) based on the composite film with 15 wt% KNN powder, reaches a maximum output current of 0.85 μA, which exhibits higher charging efficiency compared to 1-PNG. Moreover, the prepared 3-PNG can effectively harvest mechanical energy from human activities and maintain a stable output after 10,000 cycles of bending and releasing. The film exhibits complete degradation when exposed to acidic, neutral, and alkaline solutions. This research provides a promising option for environmentally friendly piezoelectric materials selected and output performance enhanced through optimized structural designs, making them more suitable for practical applications.

The effect of ions on liquid-solid interface investigated by charge sensitive direct current droplet-based electricity generator

The contact electrification (CE) between DI water and SiO2 or fluorinated polymer has been proven to be mainly due to electron transfer, which is significantly influenced by ions in solution. However, how these ions in water affect the charge transfer at the liquid-solid (L-S) interface is still unresolved, especially for the already charged friction layer. Here, a direct current droplet-based electricity generator (DC-DEG) which is sensitive to the change of charge transfer at the L-S interface is adopted to detect the effects of ions in the neutral salt solution on the charged PTFE surface. The distribution of ions on the charged L-S interface (the change of electric potential on the solid surface) and its effects on the output of DC-DEGs have been studied. The results indicate that the charge transfer of droplets and then the output of DC-DEGs are closely related to the concentrations of salt solutions. Anions can enhance the surface potential of PTFE due to their adsorptions on PFTE while cations can reduce it due to their screen effect. At low ionic concentrations, the surface potential enhancement caused by anion adsorption is larger than that surface potential reduction caused by screen effect from cations. At high ionic concentrations, the electrostatic screen effect of cations increases a lot to weaken the surface potential and reducing the charge separation of droplets induced by electrostatic induction (EI). This work explains the redistribution process of ions at the L-S interface and also provides a clever solution for improving the electrical output performance of DEGs.

HISTOCHEMICAL AND IMMUNOHISTOCHEMICAL FEATURES OF DIFFERENTIATED TROPHOBLAST IN CHORIONIC VILLI OF THE PLACENTA IN PRETERM LABOR

The importance of studying the histochemical and immunohistochemical features of the diff erentiated trophoblast in chorionic villi of the placenta in preterm labor is determined by the threatening nature of this condition for both mother and fetus, as well as its high prevalence and serious consequences for the health of both. The understanding of the damage to the trophoblast of chorionic villi in the placenta can be expanded by histochemical and immunohistochemical methods, which allow the assessment of the concentration of specifi c marker molecules in one way or another.Objective. To determine certain histochemical and immunohistochemical characteristics of proteins in the trophoblast of theintermediate and terminal chorionic villi of the placenta in preterm labor.Material and Methods. The obtained material (30 placentas from preterm deliveries and 30 placentas from normalpregnancies) was fi xed for 20-24 hours in 10 % neutral formalin solution buff ered in Lilly’s phosphate buff er. After tissue removal, the placental tissue was dehydrated in an ascending ethanol series and embedded in paraffi n at a temperature of approximately 58 °C. Serial histologic sections were cut at 5.0 μm thickness using an MS-2 sliding microtome. After deparaffi nization, histological sections were stained with hematoxylin and eosin, histochemical methods for total protein with bromophenol blue according to Bonhéme, and immunohistochemical techniques according to the manufacturer’s protocols (Dako, Denmark). In particular, immunohistochemical reactions were performed with monoclonal antibodies against trophoblast hormone- placental lactogen and placental alkaline phosphatase. Visualization of primary antibodies was performed using the Dako polymer visualization system with diaminobenzidine as chromogen (resulting in brown staining of the sites of studied antigens). In addition to the descriptive method of histopathologic research, computer morphometry of digital microphotographs of histologic sections was performed using a Delta Optical Evolution 100 microscope and an Olympus SP550UZ digital camera. Digital copies of the images were processed using a legitimate copy of the ImageJ v1.52f computer program developed for histometric studies (National Institutes of Health, USA). Specifi cally, the evaluation of staining intensity (optical density) was performed on digital microphotographs using the method of computer microdensitometry. For this purpose, a microprobe method was used to obtain a computer brightness value in an 8-bit analysis system with 256 gray levels – from black (0) to white (255).The obtained values were then transformed into relative optical density values (r.OD) by logarithmic transformation (naturallogarithm method). The relative optical density value ranges from 0 (absolute transparency of the object) to 1 (absolute opacity of the object). The obtained digital data were processed using statistical analysis methods. A legitimate copy of the statistical analysis computer program PAST v4.14 was used, with a preliminary check for normal distribution using the Shapiro- Wilk test. Since, according to this test, the hypothesis of normal distribution was not rejected for the statistical samples studied (at p=0.05), parametric methods of statistical analysis were applied: calculation of the mean and its standard error, Student’s t-test (two-tailed, unpaired). In addition, the non-parametric Mann- Whitney test was used for the reliability of the conclusions. The research was conducted as part of the scientifi c research project «Preservation and Restoration of Reproductive Health in Women and Girls with Obstetric and Gynecological Pathology» at the Department of Obstetrics and Gynecology of Bukovinian State Medical University (state registration number 0121U110020, duration 2021-2025).Results. Microscopic examination of histological sections stained with hematoxylin and eosin did not reveal any diff erencesin the structure of chorionic villus trophoblast in the placenta of preterm labor compared to normal pregnancy. However,histochemical and immunohistochemical methods of investigation revealed a number of features in the trophoblast of chorionic villi, where fundamental events related to substance exchange occur – intermediate immature, intermediate mature, terminal villi, including terminal «specialized villi».Conclusions. According to the obtained histochemical and immunohistochemical data, in preterm labor, compared to normalpregnancy, no changes are observed in the trophoblast of intermediate immature villi, while in intermediate mature and terminal villi, there is a decrease in histochemical staining for total protein and immunohistochemical staining for specifi c trophoblast proteins – placental lactogen hormone and placental alkaline phosphatase enzyme.

The effect of the irrigation solutions on dentin organic components: Pilot study

INTRODUCTION. Tooth decay and its complications are prevalent dental issues among adults. Endodontic treatment is the standard of care for complicated caries, specifically pulpitis and periodontitis. Endodontic irrigants, which are placed in the root canal lumen for a specific duration, can affect the intracanal dentin structure (organic and inorganic substances) in various ways. The use of polyhexanide-based antiseptic products in endodontics is a promising idea to overcome microbial resistance and minimize microbial-related endodontic treatment failures.AIM. The aim of this study is to investigate the qualitative impact of standard irrigation solutions and a polyhexanide-based composition on the collagen matrix of dentin.MATERIALS AND METHODS. The study investigated the effect of nine solutions on the dentin of the tooth root. Twelve intact maxillary third molars extracted for orthodontic reasons were taken for the study. The teeth were fixed in a 10% neutral formalin solution for at least one day and were decalcinated. 5–10 μm thick sample sections were made and stained with picrosirius (Picrosirius Red, Biovitrum, Russia) before being examined under polarized light. The histological slice was analyzed using a Carl Zeiss (Germany) software and hardware complex based on ZEN v3.0 and light microscope Axioimager M.1. All microphotos were loaded into the Fiji distribution program of ImageJ for microscopy pixel classification.RESULTS. Upon analysis of the diagrams, it appears that there is a lower amount and density of stained dentin collagen array after exposure to sodium hypochlorite solutions of 3% and 1.5%, as well as polyhexanide.CONCLUSIONS. The data obtained from the histogram analyzer of samples stained with picrosirius suggests that polyhexanide may have a qualitative effect on the organic structure of hard tissues, particularly collagen.

Ultra-sensitive fluorescent biosensor for multiple bacteria detection based on CDs/QDs@ZIF-8 and microfluidic fluidized bed.

An ultra-sensitive fluorescent biosensor based on CDs/QDs@ZIF-8 and microfluidic fluidized bed was developed for rapid and ultra-sensitive detection of multiple target bacteria. The zeolitic imidazolate frameworks (ZIF-8) act as the carrier to encapsulate three kinds of fluorescence signal molecules from the CDs/QDs@ZIF-8 signal amplification system. Besides, three kinds of target pathogenic bacteria were automatically, continuously, and circularly captured by the magnetic nanoparticles (MNPs) in the microfluidic fluidized bed. The neutral Na2EDTA solution was the first time reported to not only dissolve the ZIF-8 frameworks from the MNPs-bacteria-CDs/QDs@ZIF-8 sandwich complexes, but also release the CDs/QDs from sandwich complexes with no loss of fluorescence signal. Due to the advantages of signal amplification and automated sample pretreatment, the proposed fluorescent biosensor can simultaneously detect Escherichia coli O157:H7, Salmonella paratyphi A, and Salmonella paratyphi B as low as 101CFU/mL within 1.5h, respectively. The mean recovery in spiked milk samples can reach 99.18%, verifying the applicability of this biosensor in detecting multiple bacteria in real samples.

Insight into pyrrolizidine alkaloids degradation and the chemical structures of their degradation products using ultra high performance liquid chromatography and Q-Exactive Orbitrap mass spectrometry

Pyrrolizidine alkaloids (PAs), released into the environment by donor plants, are absorbed by crops or transported by animals, posing a global food safety concern. Photolysis is an effective way to eliminate harmful substances in the environment or food. Photolysis happens as PAs move among plants, environment and crops. In this study, we first investigated the photolysis and hydrolysis of 15 PAs and identified their degradation products via ultra-high performance liquid chromatography and Q-Exactive Orbitrap mass spectrometry. PAs were degraded under UV radiation but minimally affected by visible light from a xenon lamp, and solvent pH had little impact on their photolysis. PAs were stable in neutral and acidic solutions but degraded by 50% within 24hours in alkaline conditions. The degradation products of PAs were mainly PAs/PANOs isomers and some minor byproducts. Cytotoxicity and computational analysis revealed isomers had similar toxicity, with minor products being less toxic. This study is a precursor for revealing the potential PAs degradation dynamics in the environment and food products, providing a reference for systematic evaluations of potential health and ecological risks of their degradation products. Environmental ImplicationPyrrolizidine alkaloids (PAs) are considered as emerging organic pollutants, posing risks to environment and food. This study first unveiled photodegradation patterns of PAs. PAs degraded slowly under acidic and neutral conditions but rapidly under alkaline conditions with UV radiation. UHPLC-Q-Exactive Orbitrap MS was employed to dissect photodegradation products. Furthermore, a slight reduction in the toxicity of PAs was observed after prolonged photodegradation. This work contributed to understanding the degradation dynamics of PAs in environment and food, offering insights for future comprehensive assessments of the health and ecological risks associated with PAs.

Effect of TiO2/Fe2O3 nanopowder synthesis method on visible light photocatalytic degradation of reactive blue dye

Water pollution and scarcity of clean water are major issues of concern globally. In this study, titanium dioxide (TiO2) photocatalyst doped with ferric oxide (Fe2O3) was used to degrade reactive blue dye (171) using sunlight irradiation. Two approaches were employed to synthesize the photocatalyst: synthesis of ferric oxide and titanium precursor through ultrasonic-assisted sol-gel method and using iron (III) nitrate nonahydrate with commercial titanium dioxide. The photocatalysts were characterized using FTIR Spectroscopy, SEM, XRD analyses, and UVDRS to determine their chemical composition, morphology, crystallinity, and light absorption, respectively. The effect of contaminant concentration (1–3 ppm), solution pH and photocatalyst type on the degradation efficiency was studied. Doping enabled visible light absorption as confirmed by the UVDRS analysis. Solar photocatalytic degradation resulted in complete (100 % removal) of the dye within 2 h under solar irradiation for all concentrations of the dye studied. Furthermore, the photocatalysts exhibited superior performance in both neutral and acidic solutions compared to basic ones. After four cycles, the dye removal efficiency has decreased by less than 15 % for all the photocatalysts confirming the significant activity and high stability of the nanocomposite. The increased dye photodegradation efficacy of Fe2O3 doped TiO2 under sunlight irradiation is attributed to the narrowing of the photocatalyst's bandgap from 3.76 eV (in pure TiO2) to 2.83 eV. This narrowing of the bandgap enhances the absorption of visible light from sunlight, thus making this photocatalyst effective under sunlight and eliminating the use of electricity which is a requirement for ultraviolet photocatalysis.

Aqueous pH influence on the electrocatalytic hydrogen evolution reaction with carbon nanotube-supported diiron dithiolato compound

Biomimetic chemistry on structure, function and external environment of [FeFe]-hydrogenases for hydrogen evolution reaction (HER) has shown a promising way to develop non-precious metal electrocatalysts for H2 production in the current Pt-dominated HER system. Herein, three new diiron dithiolato compounds [{(μ-SCH2)2N(C6H4CH2CO2R)}Fe2(CO)6] (R = H (1), C6H4CHO-p (2), and C6H4Me-m (3)) were first prepared and identified as a library of [FeFe]-hydrogenase models in this work. Subsequently, the as-prepared diiron molecule 2 can be covalently attached onto carbon nanotubes (CNTs), resulting in the obtainment of target CNT-supported [FeFe]-hydrogenase model labeling as covalent hybrid 2Fe2S-f-CNT. Notably, the electrocatalytic HER performance and stability of the resulted hybrid 2Fe2S-f-CNT immobilized respectively on a gassy carbon (GC) electrode are systematically studied and compared in 0.1 M KOH (pH = 13), 0.1 M phosphate buffer (pH = 7), and 0.05 M H2SO4 (pH = 1) aqueous solutions by various spectroscopic and electrochemical techniques. The result has shown that the higher electrocatalytic HER activity is observed in alkaline solution (pH = 13) relative to neutral and acidic solutions (pH = 7, 1), being attributed to the different electrochemical HER processes of diiron cluster in wide pH aqueous media as revealed by post operando analysis.