Changes In Morphology Structure Research Articles

The potential of helichrysum italicum essential oil-infused alginate coatings and film for prolonging the shelf-life of cherry tomatoes

This study aimed to develop edible coatings and films using sodium alginate (1 % Alg) and varying concentrations of Helichrysum italicum essential oil (HIEO) (0.3 % and 0.5 %) for cherry tomato preservation. The treatments consisted of Alg, Alg/0.3 % HIEO, and Alg/0.5 % HIEO. The physico-chemical, mechanical, water vapor permeability, optical, thermal, and antifungal properties of these coatings and films were examined. Scanning electron microscopy and Fourier transform infrared spectroscopy analyses showed that the addition of HIEO resulted in a heterogeneous morphology and slight chemical structural changes in the Alg film. The Alg/0.5 % HIEO films exhibited improved water vapor permeability, antioxidant capacity, ultraviolet light barrier properties, elongation at break, and thermal stability. Additionally, 0.5 % HIEO significantly reduced the mycelial growth of Botrytis cinerea (in vitro), making Alg/0.5 % HIEO the optimal coating. Cherry tomatoes coated with Alg/0.5 % HIEO and stored at 25 °C and 60 % relative humidity for 18 d showed reduced weight loss (5.22 ± 1.45 %) and preserved firmness (6.43 N). This coating also inhibited the Rhizopus stolonifer lesion diameter by 61.36 % (in vivo). In conclusion, Alg/0.5 % HIEO coatings are promising sustainable active packaging solutions for cherry tomato storage applications.

Synthesis, characterization, and application of novel fluorescent sporopollenin for effective detection of mercury (II) ions from aqueous media

In this investigation, a novel environmentally friendly functionalized fluorescent Sp-TAB hybrid material was advanced for the sensitive detection of environmentally polluting Hg(II). The characterization of the synthesized fluorescent Sp-TAB hybrid material using SEM and EDX provided insights into morphological and structural changes in the material's pore structure, while XRD and FT-IR analyses revealed the impact of the prepared material at each stage. Optimal parameters such as temperature, contact time, and pH influencing Hg(II) ion detection were determined. Application of the fluorescent Sp-TAB hybrid material was determined a detection limit (LOD) of 4.87 μM for Hg(II) ions. This study shows the potential of the immobilization-enhanced fluorescent Sp-TAB hybrid material for sensitive Hg(II) ion detection in tap water. Additionally, this study is believed to serve as a model for sensitive and practical detection applications of heavy metals in the future.

Beneficiation of High Sulfur Tertiary Coal of Assam with Burkholderia sp. GR 8-02. An Eco-Friendly Approach Toward Clean Coal Production

The high sulfur content in North-East Indian coal is one of the primary challenges with using it as an energy source. Therefore, the present study uses Burkholderia sp. GR 8-02 to explore coal beneficiation from the Tipong mine (T20 and T60) in Assam (North-East India). Various particle size fractions (−125 to +210 µm, −210 to +250 µm, −250 to +297 µm, −297 to +400 µm and −400 to +500 µm) were treated and subjected to petrographic and chemical analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS), Thermogravimetric analysis (TGA), and Raman spectral analysis. The results revealed a 39.04% and 32.43% reduction in total sulfur for T20 and T60 samples, respectively. The ash content decreased by 19.79% in the T20 coal sample and by 24.52% in the T60 coal samples, with a relative decrease in the mineral matter content of approximately 17.43%. Following beneficiation with Burkholderia sp. GR 8-02, the −125 to +250 µm coal fraction exhibited maximum ash removal. The T20 sample useful heating value increased from 8116 to 8203 kcal/kg and the T60 sample from 8060 to 8210 kcal/kg. X-ray diffraction and FTIR patterns showed mineral phases like quartz, kaolinite, and pyrite. The FTIR spectra indicated altered C-S, SO2, and C=O bonds. The thermal profile showed a 12.54% mass loss difference between untreated and treated coal samples, suggesting lower thermal stability post-treatment without affecting the useful heating value (UHV). The treated coal’s surface leaching and morphological structure changes were investigated using Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS) images. Raman analysis revealed increased carbon crystallinity and molecular structure in treated coal. This study offers an environmentally friendly and efficient approach to clean coal production.

Nicotine addiction is the main risk factor for the formation and development of chronic obstructive pulmonary disease: A review

The article considers the issue of studying the effect of nicotine dependence on the development of chronic obstructive pulmonary disease, as the main factor in the formation of inflammation mediated through the use of tobacco-containing, as well as alternative tobacco products, not only the epithelium of the bronchi, but also the endothelial cells of large and small vessels. Morphological changes in bronchopulmonary structures lead to pronounced tissue hypoxia, which in turn aggravates the course of the underlying disease, leads to the formation of concomitant pathology in the form of cardiovascular diseases, pathology of blood rheology, increased risks of thrombosis. Without considering the risks of early death in this context, we can say with confidence that a decrease in the level of quality of life and human activity will directly depend on the availability of constant and prolonged use of nicotine-containing products.

Essential oils from Cuminum cyminum and Laurus nobilis and their principal constituents: evaluation of antifungal and antimycotoxigenic potential in Aspergillus species.

The antifungal and antimycotoxigenic activities of the essential oils (EO) from Cuminum cyminum and Laurus nobilis, and their respective principal compounds, cuminaldehyde and 1,8-cineole, were evaluated against fungi of the genus Aspergillus: A.carbonarius, A.niger, A.ochraceus and A.westerdijkiae. The antifungal activity was determined by the contact method and the mycelial growth of the fungi was evaluated. Scanning Electron Microscopic (SEM) images were obtained to suggest modes of action of the compounds analyzed. The antimycotoxigenic activity was determined by HPLC. A.carbonarius was completely inhibited by cumin EO (500 µL L-1), by laurel EO and by cuminaldehyde (5000 µL L-1). The cumin EO (500 µL L-1) completely inhibited the growth of A.niger. All the samples inhibited the mycelial growth of A.ochraceus, especially cumin EO and cuminaldehyde (250 µL L-1). A.westerdijkiae was completely inhibited by cumin EO and cuminaldehyde (1000 µL L-1), by laurel EO and 1,8-cineole (10000 µL L-1). A decrease in the production of ochratoxin A (OTA) was observed post-treatment, except in A. ochraceus, only inhibited by laurel EO. SEM images showed morphological changes in fungal structures and spore inhibition post-treatment. The results confirmed the antifungal and antimycotoxigenic effect of EO and their principal constituents on fungi evaluated.

Swelling-assisted surface grafting strategy for multichannel antifouling membranes: Reconstruction of surface pore structure and applications in microalgae harvesting and blood purification

Membrane fouling remains a major challenge in membrane separation. The modification of hydrophilic membrane surfaces can mitigate irreversible fouling deposition, thereby improving antifouling properties. Effective surface modification strategies are essential techniques for developing highly efficient antifouling membranes. In this work, a swelling-assisted surface grafting strategy was proposed for multichannel antifouling membranes, where various lengths of polyvinylpyrrolidone (PVP) brushes were grafted on the surface of polysulfone membrane using reversible addition-fragmentation chain transfer polymerization. The successful grafting of PVP polymer brushes was confirmed using Fourier transform infrared spectrometer and X-ray Photoelectron Spectroscopy. Changes in membrane morphology and pore structure were observed via scanning electron microscope and atomic force microscope. During the grafting process, the amphiphilic macromolecules formed through grafting were selectively swelled by graft solvent, leading to the formation of mesopores in both the surface layer and sublayer of the membrane, which formed additional water transport channels. The introduction of hydrophilic polymer brushes and the change of pore structure significantly boosted the hydrophilicity and permeability of the membranes. As a result, the water contact angle decreased from 85° to 42°, accompanied by an approximate 3.24-fold increase in pure water flux (PWF). Due to superior hydrophilicity, modified membranes demonstrated exemplary performance in microalgae harvesting, boasting a microalgae retention rate nearing 100 % and low fouling resistance (2.12 × 1012 m−1). In algal filtration experiments, a confocal laser scanning microscope was employed to assess the activity of filtered algae on the membrane surface. The prepared membranes effectively maintained the bioactivity of algae while also achieving a high flux recovery rate (90.7 %) following filtration and cleaning. Furthermore, in blood cell compatibility tests, the modified membranes exhibited resistance to blood cell adhesion and sustained a low hemolysis rate (0.06 %). Overall, this strategy offers unique insights into the fabrication of antifouling surfaces and shows considerable promise for large-scale applications in microalgae harvesting and blood purification.

Cortical and subcortical structural changes in pediatric patients with infratentorial tumors.

This study aimed to detect supratentorial cortical and subcortical morphological changes in pediatric patients with infratentorial tumors. The study included 24 patients aged 4-18 years who were diagnosed with primary infratentorial tumors and 41 age- and gender-matched healthy controls. Synthetic magnetization-prepared rapid gradient echo images of brain magnetic resonance imaging were generated using deep learning algorithms applied to T2-axial images. The cortical thickness, surface area, volume, and local gyrification index (LGI), as well as subcortical gray matter volumes, were automatically calculated. Surface-based morphometry parameters for the patient and control groups were compared using the general linear model, and volumes between subcortical structures were compared using the t-test and Mann-Whitney U test. In the patient group, cortical thinning was observed in the left supramarginal, and cortical thickening was observed in the left caudal middle frontal (CMF), left fusiform, left lateral orbitofrontal, left lingual gyrus, right CMF, right posterior cingulate, and right superior frontal (P < 0.050). The patient group showed a volume reduction in the pars triangularis, paracentral, precentral, and supramarginal gyri of the left hemisphere (P < 0.05). A decreased surface area was observed in the bilateral superior frontal and cingulate gyri (P < 0.05). The patient group exhibited a decreased LGI in the right precentral and superior temporal gyri, left supramarginal, and posterior cingulate gyri and showed an increased volume in the bilateral caudate nucleus and hippocampus, while a volume reduction was observed in the bilateral putamen, pallidum, and amygdala (P < 0.05). The ventricular volume and tumor volume showed a positive correlation with the cortical thickness in the bilateral CMF while demonstrating a negative correlation with areas exhibiting a decreased LGI (P < 0.05). Posterior fossa tumors lead to widespread morphological changes in cortical structures, with the most prominent pattern being hypogyria. This study illuminates the neurological impacts of infratentorial tumors in children, providing a foundation for future therapeutic strategies aimed at mitigating these adverse cortical and subcortical changes and improving patient outcomes.

Ultrasonographic Evaluation of Morphological Changes in Peripheral Nerves after Traumatic Injury and Nerve Repair - A Prospective Study.

Purpose Ultrasound (US) has gained in importance for the visualization of morphological changes of injured nerves. After surgical repair, changes in neural structures are seen over time. The correlation of morphologic changes in US with the corresponding nerve function is uncertain. The aim of this study is to determine a correlation of post-traumatic morphological nerve changes with US and with nerve function after surgery. Materials and Methods This dual-center, prospective cohort study was conducted between 2017 and 2022 and included 20 mixed sensory motor nerve lesions. Patients were followed up clinically (sensitivity, pain, and motor function) with US and electroneuromyography. We determined the US changes of the nerves including the interaction of the tissue after nerve repair and any correlation with nerve function. With US nerve cross-sectional area (CSA), the number of traversing fascicles, hypo-echogenicity, and presence of perineural scar were analyzed. Results 20 lesions (12 median and 8 ulnar nerves) of 18 patients with intraoperatively confirmed nerve injury of at least 50% in the forearm were included. The average CSA was over 20 mm 2 throughout the follow-up period, corresponding to a neuroma in continuity compared to the opposite side (10.75 mm 2 ). Sensibility and motor function at 12 months were 6xS3/4 and 10xM3-5. There was a statistically significant correlation between continuous fascicles on US at 6 months and sensitivity at 12 months. Conclusion This study supports the presence of post-traumatic morphological changes in nerve fibers with US after traumatic injury. Morphological changes in nerve structure after trauma can be detected with US indicating a correlation between continuity of nerve fascicles and development of sensitivity and motor function.

Photodegradation Processes and Weathering Products of Microfibers in Aquatic Environments.

Microplastics, particularly microfibers (MFs), pose a significant threat to the environment. Despite their widespread presence, the photochemical reactivity, weathering products, and environmental fate of MFs remain poorly understood. To address this knowledge gap, photodegradation experiments were conducted on three prevalent MFs: polyester (POL), nylon (NYL), and acrylic (ACR), to elucidate their degradation pathways, changes in surface morphology and polymer structure, and chemical and colloidal characterization of weathering products during photochemical degradation of MFs. The results showed that concentrations of dissolved organic carbon, chromophoric dissolved organic matter (DOM), and fluorescent components consistently increased during weathering, exhibiting a continuous release of DOM. Scanning electron microscopy and Raman spectroscopy revealed changes in the surface morphology and polymer spectra of the MFs. During the weathering experiments, DOM aromaticity (SUVA254) decreased, while spectral slope increased, indicating concurrent DOM release and degradation of aromatic components. The released DOM or nanoplastics were negatively charged with sizes between 128 and 374 nm. The production rate constants of DOM or the photochemical reactivity of MFs followed the order ACR > NYL ≥ POL, consistent with their differences in chemical structures. These findings provide an improved understanding of the photochemical reactivity, degradation pathways, weathering products, and environmental fate of microfibers in the environment.

CuxS films as photoelectrodes for visible-light water splitting

Copper sulfides are appealing semiconductors for optoelectronics applications requiring visible-light activity, such as solar water splitting, due to their relatively low band gaps and earth-abundance. This study investigates the effect of deposition conditions, including substrate temperature and background gas pressure, on the characteristics and photoelectrochemical performance of copper sulfide (CuxS) films grown by pulsed laser deposition (PLD) on Si (100) substrates. The results reveal that varying the deposition parameters influences the crystalline phases, morphology, and optoelectronic properties of the films. For deposition at room temperature, the films exhibited covellite CuS phase, while elevated deposition temperatures (250 °C and 500 °C) led to the formation of Cu1.8S and Cu2S phases, resulting in narrowing of the band gap, with the increased temperature also enhancing the film crystallinity and surface roughness. As a result of the changes in film morphology and crystal structure, photocurrent density magnitudes increased with higher deposition temperatures, reaching 0.747 mA/cm2 at −0.8 V for films deposited at 500 °C under vacuum, at least an order of magnitude higher than reported in comparable previous studies of the photoelectrochemical performance of CuxS. Background gas pressure only slightly affected the photocurrent density, with changes in photoactivity also correlating with changes in film roughness and band gap. The results demonstrate the good visible-light activity and behavior of CuxS as a stand-alone photoelectrode material, with tunability based on the fabrication conditions, suggesting their potential use in photoelectrochemical and other solar energy conversion applications.

Effects of Low-Temperature Stress on Physiological Characteristics and Microstructure of Stems and Leaves of Pinus massoniana L.

Pinus massoniana L. is one of the most important conifer species in southern China and is the mainstay of the forest ecosystem and timber production, yet low temperatures limit its growth and geographical distribution. This study used 30-day-old seedlings from families of varying cold-tolerance to examine the morphological traits of needles and stems, chlorophyll fluorescence characteristics, protective enzymes, and changes in starch and lignin under different low-temperature stresses in an artificial climate chamber. The results showed that the seedlings of Pinus massoniana exhibited changes in phenotypic morphology and tissue structure under low-temperature stress. Physiological and biochemical indexes such as protective enzymes, osmoregulatory substances, starch, and lignin responded to low-temperature stress. The cold-tolerant family increased soluble sugars, starch grain, and lignin content as well as peroxidase activity, and decreased malondialdehyde content by increasing the levels of actual photochemical efficiency (ΦPSII), electron transport rate (ETR), and photochemical quenching (qP) to improve the cold tolerance ability. This study provides a reference for the selection and breeding of cold-tolerant genetic resources of Pinus massoniana and the mechanism of cold-tolerance, as well as the analysis of the mechanism of adaptation of Pinus massoniana in different climatic regions of China.

Ginsenoside Rg1 ameliorates cerebral ischemia-reperfusion injury by regulating Pink1/ Parkin-mediated mitochondrial autophagy and inhibiting microglia NLRP3 activation

ObjectiveThis study aimed to further elucidate the mechanism of ginsenoside Rg1 in the treatment of cerebral ischemia-reperfusion. MethodsIn this study, we observed the apoptosis of RM cells (microglia) after oxygen-glucose deprivation/reoxygenation (OGD/R) modeling before and after Rg1 administration, changes in mitochondrial membrane potential, changes in the content of Reactive oxygen species (ROS) and inflammatory vesicles NLR Family Pyrin Domain Containing 3 (NLRP3), and the expression levels of autophagy-related proteins, inflammatory factors, and apoptosis proteins. We further examined the pathomorphological changes in brain tissue, neuronal damage, changes in mitochondrial morphology and mitochondrial structure, and the autophagy-related proteins, inflammatory factors, and apoptosis proteins expression levels in CI/RI rats before and after administration of Rg1 in vivo experiments. ResultsIn vitro experiments showed that Rg1 induced mitochondrial autophagy, decreased mitochondrial membrane potential, and reduced ROS content thereby inhibiting NLRP3 activation, decreasing secretion of inflammatory factors and RM cell apoptosis by regulating the PTEN induced putative kinase 1(Pink1) /Parkin signaling pathway. In vivo experiments showed that Rg1 induced mitochondrial autophagy, inhibited NLRP3 activation, improved inflammatory response, and reduced apoptosis by regulating the Pink1/Parkin signaling pathway, and Rg1 significantly reduced the area of cerebral infarcts, improved the pathological state of brain tissue, and attenuated the neuronal damage, thus improving cerebral ischemia/reperfusion injury in rats. ConclusionOur results suggest that ginsenoside Rg1 can ameliorate cerebral ischemia-reperfusion injury by modulating Pink1/ Parkin-mediated mitochondrial autophagy in microglia and inhibiting microglial NLRP3 activation.

Real-Time Monitoring of Electrochemical Reactions in All-Solid-State Lithium Batteries by Simultaneous Grazing-Incidence Small-Angle/Wide-Angle X-Ray Scattering

Polyethylene oxide (PEO)-based composite electrolytes (PCEs) are considered as the promising candidates for next generation lithium metal batteries due to its high safety, easy fabrication and good electrochemical stability. However, the material suffers from low conductivity and high crystallinity of the ethylene oxide (EO) chain, which inhibits its commercialization. Therefore, it is crucial to understand the electrochemcial process as well as Li+ transfer pathway within PEO-based batteries. Using operando grazing-incidence small-angle and wide-angle X-ray scattering (GISAXS and GIWAXS) in Li||Cu cell framework, we find that the electrochemical reaction within the PCE is highly correlated with the evolution of the buried morphology and crystalline structure evolution of the PCE. This two irreversible reactions, PEO-Li+ reduction and TFSI- decomposition, cause changes in both the crystalline structure and morphology of the PCE. In addition, the reversible Li plating/stripping process alters the inner morphology, especially the PEO-LiTFSI domain radius, rather than causing crystalline structure changes. This work provides a new path to monitor a working battery in real time, thereby enabling detailed understanding of electrochemically-induced changes of the microscopic morphology and crystalline structure of PCE, which is essential for developing high transferable and interface stable PCE-based lithium metal batteries. Figure 1

Toward Sustainable Olefins: Electroreduction of CO2 to Multi-Carbon Olefins Using Trimetallic Cu-Rich Catalysts

The sustainable conversion of carbon monoxide (CO2) into value-added chemicals via electrochemical methods, powered by renewable electricity, is considered as a promising approach to meet the global energy demand and close the anthropogenic carbon cycle. However, this technology is in the early stage of development, particularly in the production of multi-carbon (C2+) hydrocarbons due to well-studied thermodynamic and kinetic barriers. To overcome these challenges, developing a catalyst with high activity and selectivity is crucial to minimize energy input and maximize the effectiveness of C2+ products formation.In this work, we will present our recent advancement on developing non-precious tri-metallic catalysts with copper-rich surface synthesized by our developed atomically controllable and environmentally friendly synthesis method. The developed nanostructured tri-metallic electrocatalysts by this method show remarkable selectivity and activity in the electrochemical conversion of CO2 to olefins. In particular, our electrochemical results show an overall C2+ olefine Faradaic efficiency (FE%) of 69% more specifically 58% ethylene and 11% propylene at a current density of -112 mA/cm² under applied potential of -2.8 V in an anion exchange membrane (AEM) electrolyzer. To gain a better understanding of the catalytic performance and find a structural-performance relationships for the developed materials, we performed several physicochemical and electrochemical characterization experiments, including X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS). We will discuss morphology and atomic structure changes of the developed materials under realistic conditions, with a specific focus on understanding how different trimetallic interfaces influence selectivity and activity in the electrochemical CO2 reduction reaction (eCO2RR).

Morphological changes and luminescence of Escherichia coli in contact with Mn2O3 and Co3O4 ultrafine particles as components of a mineral feed additive.

The spread of antibiotic resistance and mineral depletion in soils encourages an intensive search for highly effective and environmentally safe bactericidal agents and sources of macro- and micro-elements. The most profitable solution would combine both the described tasks. Ultrafine particles (UFPs) have this functionality. Thus, this study aimed to analyze the bioluminescence and external morphological changes of Escherichia coli cells after contact with M2O3 and Co3O4 UFPs at effective concentrations (ECs). The antibiotic properties of the studied samples were determined on a multifunctional microplate analyzer TECAN Infinite F200 (Tecan Austria GmbH, Austria) by fixing the luminescence value of the bacterial strain E. coli K12 TG11 (Ecolum, NVO Immunotech Closed Joint Stock Company, Russia). Morphological changes in the cell structure were evaluated using a Certus Standard EG-5000 atomic force microscope equipped with NSPEC software (Nano Scan Technology LLC, Russia). The obtained results indicate high bactericidal properties of Co3O4 and Mn2O3 UFPs (EC50 at 3.1 × 10-5 and 1.9 × 10-3 mol/L, respectively) due to the degradation of the cell wall, pathological increase in size, disruption of septic processes, and loss of cytoplasmic contents. The prospects for the environmentally safe use of ultrafine materials are outlined. The limits of the dosages of Co3O4 and Mn2O3 UFPs recommended for further study in vitro and in vivo in feeding farm animals are established (no more than 4.9 × 10-4 mol/L for Mn2O3 UFPs and 1.5 × 10-5 mol/L for Co3O4 UFPs). The limitation of the work is the lack of experiments to determine the mechanisms of the toxic effect of UFP on bacteria, protein structures, and DNA and oxidative stress, which is planned to be performed in the future together with in situ and in vivo studies on animals.

Evaluation of the Relationship Between Osteoarthritis and Morphological Changes in the Joint Structures in Temporomandibular Disorders By Cone Beam Computed Tomography

Evaluation of the Relationship Between Osteoarthritis and Morphological Changes in the Joint Structures in Temporomandibular Disorders By Cone Beam Computed Tomography

Hydrolysis of Babool wood biomass using carbocation scavengers assisted ionic liquid pretreatment for the production of sugars and furfurals

The present study highlights the performance of carbocation scavengers for the pretreatment of hardwood biomass followed by the production of bio-based products. The behaviour of different carbocation scavengers namely; 2-Napthol, 4 Hydroxybenzoic acid, Vanillic acid, Catechol, Hydroquinone, Resorcinol and Phenol and their mitigating effect on the rate of hydrolysis was explored under different operating conditions. All the carbocation scavengers show significant changes in the crystallinity index leading to distinct morphological and physiochemical changes in the biomass structure. Results revealed that the addition of carbocation scavengers not only reduces the inhibitory effect of structured lignin but also enhances the accessibility of cellulose and hemicellulose and facilitates the production of sugars and 5-Hydroxymethyl Furfural. Maximum 5-HMF yield was observed using 2-Napthol at an optimised concentration of 2 wt% (1.5 mL) at 190 °C in 60 min. Further, to evaluate the effect of acetyl groups, biomass deacetylation was also performed. The highest deacetylation effect was observed at 170 °C and showed ∼73% and ∼94% reduction in the holocellulosic content in 60 min. The proposed study develops a sustainable and viable route to suppress the inhibitory effect of lignin with the utilization of carbocation scavengers and enhances biomass digestibility that favours the production of bio-based chemicals.

Degradation Behaviors of Polylactic Acid, Polyglycolic Acid, and Their Copolymer Films in Simulated Marine Environments.

Poly(lactic acid) (PLA) and poly(glycolic acid) (PGA) are extensively studied biodegradable polymers. However, the degradation behavior of their copolymer, poly(lactic-co-glycolic acid) (PLGA), in marine environments has not yet been confirmed. In this study, the changes in macroscopic and microscopic morphology, thermal properties, aggregation, and chemical structure of PLA, PGA, PLGA-85, and PLGA-75 (with 85% and 75% LA content) in simulated marine environments were investigated. Results revealed that degradation occurred through hydrolysis of ester bonds, and the degradation rate of PGA was faster than that of PLA. The amorphous region degraded preferentially over the crystalline region, leading to cleavage-induced crystallization and decreased thermal stability of PLA, PLGA-85, and PLGA-75. The crystal structures of PLGAs were similar to those of PLA, and the higher GA content, the faster was the degradation rate. This study provides a deeper understanding of the seawater degradation behaviors of PLA, PGA, and their copolymers, and provides guidance for the preparation of materials with controllable degradation performance.

Biodegradation behavior of poly (glycolic acid) (PGA) and poly (butylene adipate-co-terephthalate) (PBAT) blend films in simulation marine environment

Polyglycolic acid (PGA) and poly (butylene adipate-co-terephthalate) (PBAT), as widely applied biodegradable polymers, the degradation behavior of their blends in marine environments has not been proven. This study investigated the changes of macroscopic and microscopic morphology, thermal properties, crystalline and chemical structure, degradation rate of PGA/PBAT blends with different ratios in the simulation marine environment containing sediments and marine organisms. The results showed that degradation primarily occurred due to ester bond breakage, and PGA exhibited a faster degradation rate than PBAT films. The amorphous region degraded more rapidly than the crystalline region, and the thermal stability of the materials decreased. The degradation of PGA and PBAT blends followed their respective single degradation laws and the compatibility of blend samples decreased after degradation. The degradation rate of the samples was obtained by measuring the biochemical oxygen demand, which indicated that a higher PGA content could result in a faster degradation rate for PGA/PBAT films. This study provides an efficient method for constructing materials with controlled biodegradability.

Defect engineering of copper-doped mesoporous manganese dioxide nanoflowers for enhancing electrocatalytic detection of hydrogen peroxide

Birnessite-type δ-MnO2 nanoflowers doped with copper ions (Cu-MnO2) can enhance the catalytic performance of MnO2-based catalysts for efficient electrochemical sensing of H2O2. There are no significant changes in the surface morphology and lattice structure of bulk MnO2 after Cu doping via engineered cation exchange. The catalytic Cu species are effectively incorporated into the tunnel entrance of δ-MnO2, the Mn site in the MnO6 octahedron, and surface defects. The Cu doping enhances the electrical and ionic conductivities, and generates numerous Mn3+ defects, oxygen vacancies, and Cu+/Cu2+ redox sites. Thus, the Cu doping facilitates the transport and adsorption of more H2O2 molecules to the catalytic sites, significantly increasing the catalytic rate. In contrast, pristine MnO2 exhibits negligible catalytic performance for H2O2 reduction because of its slow catalytic kinetics and low electrical conductivity. The Cu-MnO2 catalyst exhibits higher sensitivity (105.7 μA·mM−1·cm−2), a lower detection limit (0.6 μM), and a broader linear range (0.005 ∼ 4.2 mM) compared to pristine δ-MnO2.