The cellular response and molecular mechanism of superoxide dismutase interacting with superparamagnetic iron oxide nanoparticles.

This study explored the response of superoxide dismutase (SOD) under superparamagnetic iron oxide nanoparticles (SPIONs)-induced oxidative stress using combined cellular and molecular methods. Results found that SPIONs induced the inhibition of catalase activity, the U-inverted change of SOD activity and the accumulation of reactive oxygen species (ROS), leading to oxidative damage and cytotoxicity. The change of intracellular SOD activity was resulted from the increase of molecular activity induced by directly interacting with SPIONs and ROS-inhibition of activity. The increase of molecular activity could be attributed to the structural and conformational changes of SOD, which were caused by the direct interaction of SOD with SPIONs. The SOD-SPIONs interaction and its interacting mechanism were explored by multi-spectroscopy, isothermal titration calorimetry and zeta potential assays. SOD binds to SPIONs majorly via hydrophobic forces with the involvement of electrostatic forces. SPIONs approximately adsorb 11 units of SOD molecule with the binding affinity of 2.99 × 106 M-1. The binding sites on SOD were located around Tyr residues, whose hydrophilicity increased upon interacting with SPIONs. The binding to SPIONs loosened the peptide chains, changed the secondary structure and reduced the aggregation state of SOD.

Cyclodextrin-based host-guest hierarchical fire retardants: Synthesis and novel strategy to endow polylactic acid fire retardancy and UV resistance.

ß-Cyclodextrin (ß-CD) with a cage-like supramolecular structure possesses the hydrophobic internal ring and external hydroxyl groups, which are beneficial for intramolecular interactions known as "host-guest" chemistry. This study presents a ß-CD-based three-functions-in-one and host-guest fire retardant (ßCD-MOF@Schiff base), which incorporates self-crosslinking Schiff base into its cavity and modification of its surface by metal-organic framework (MOF). With the presence of 5 wt% of ßCD-MOF@Schiff base, the LOI value of PLA composites increased to 29 % and showed 15 %, 17 % and 62 % reductions in peak heat release rate (pHRR), total heat release (THR), and the yield of hazard gas carbon monoxide, respectively. The mode action of FR on fire retardation of PLA showed that the FR promoted the char formation with higher thermal stability and graphitization, and modified the decomposition path of PLA. Additionally, the PLA composites exhibited enhanced UV resistance in the UVA and UVB areas with improved UV absorbance and the UPF values improving and doubling. This work develops a new approach to preparing biodegradable FR, which simultaneously endows fire safety and anti-UV properties for PLA.

Exploiting Waste towards More Sustainable Flame-Retardant Solutions for Polymers: A Review.

The development of sustainable flame retardants is gaining momentum due to their enhanced safety attributes and environmental compatibility. One effective strategy is to use waste materials as a primary source of chemical components, which can help mitigate environmental issues associated with traditional flame retardants. This paper reviews recent research in flame retardancy for waste flame retardants, categorizing them based on waste types like industrial, food, and plant waste. The paper focuses on recent advancements in this area, focusing on their impact on the thermal stability, flame retardancy, smoke suppression, and mechanical properties of polymeric materials. The study also provides a summary of functionalization methodologies used and key factors involved in modifying polymer systems. Finally, their major challenges and prospects for the future are identified.

Mycoheterotrophy in the wood-wide web.

The prevalence and potential functions of common mycorrhizal networks, or the 'wood-wide web', resulting from the simultaneous interaction of mycorrhizal fungi and roots of different neighbouring plants have been increasingly capturing the interest of science and society, sometimes leading to hyperbole and misinterpretation. Several recent reviews conclude that popular claims regarding the widespread nature of these networks in forests and their role in the transfer of resources and information between plants lack evidence. Here we argue that mycoheterotrophic plants associated with ectomycorrhizal or arbuscular mycorrhizal fungi require resource transfer through common mycorrhizal networks and thus are natural evidence for the occurrence and function of these networks, offering a largely overlooked window into this methodologically challenging underground phenomenon. The wide evolutionary and geographic distribution of mycoheterotrophs and their interactions with a broad phylogenetic range of mycorrhizal fungi indicate that common mycorrhizal networks are prevalent, particularly in forests, and result in net carbon transfer among diverse plants through shared mycorrhizal fungi. On the basis of the available scientific evidence, we propose a continuum of carbon transfer options within common mycorrhizal networks, and we discuss how knowledge on the biology of mycoheterotrophic plants can be instrumental for the study of mycorrhizal-mediated transfers between plants.

Elaboration of Thermally Performing Polyurethane Foams, Based on Biopolyols, with Thermal Insulating Applications.

In this work, biobased rigid polyurethane foams (PUFs) were developed with the aim of achieving thermal and fireproofing properties that can compete with those of the commercially available products. First, the synthesis of a biopolyol from a wood residue by means of a scaled-up process with suitable yield and reaction conditions was carried out. This biopolyol was able to substitute completely the synthetic polyols that are typically employed within a polyurethane formulation. Different formulations were developed to assess the effect of two flame retardants, namely, polyhedral oligomeric silsesquioxane (POSS) and amino polyphosphate (APP), in terms of their thermal properties and degradation and their fireproofing mechanism. The structure and the thermal degradation of the different formulations was evaluated via Fourier Transformed Infrared Spectroscopy (FTIR) and thermogravimetric analysis (TGA). Likewise, the performance of the different PUF formulations was studied and compared to that of an industrial PUF. From these results, it can be highlighted that the addition of the flame retardants into the formulation showed an improvement in the results of the UL-94 vertical burning test and the LOI. Moreover, the fireproofing performance of the biobased formulations was comparable to that of the industrial one. In addition to that, it can be remarked that the biobased formulations displayed an excellent performance as thermal insulators (0.02371-0.02149 W·m-1·K-1), which was even slightly higher than that of the industrial one.

Bio-based epoxy vitrimer with inherent excellent flame retardance and recyclability via molecular design.

The development of biobased fire-safe thermosets with recyclability heralds the switch for a transition towards a circular economy. In this framework, we introduced a novel high-performance bio-epoxy vitrimer (named GVD), which was fabricated by forming a crosslinking network between bio-epoxy glycerol triglycidyl ether (Gte), varying amounts of reactive flame-retardant agent 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) (0-7 wt%) and a vanillin-based hardener (VA) with imine bonds. For instance, the epoxy vitrimer GVD5, featuring a DOPO content of 5 wt%, achieved a V-0 rating in the vertical burning test (UL-94) and obtained a limiting oxygen index (LOI) value of 31 %, surpassing the performance of pristine epoxy. Furthermore, the peak heat release rate and total heat release of GVD5 were reduced by 38.2 % and 26.3 %, respectively, compared to pristine epoxy. The GVD vitrimers further demonstrated exceptional reprocessability and recyclability, attributed to the presence of dynamic imine bonds within the topological crosslinking network. Remarkably, the epoxy vitrimers maintained the mechanical properties of the parent epoxy. Therefore, this work provides a facile strategy for fabricating high-performance and multi-functional bio-epoxy thermosets.

Multifunctional polylactic acid sensing fabric based on biomass flame retardants for intelligent fire early-warning.

Today, building materials emit many hazardous gases in the event of a fire, causing great harm to human health and the environment. Therefore, it is of great significance to develop bio-based flame retardant materials and to realize preventive measures to reduce fires or their damage. In this work, we fabricated a novel multifunctional fire early-warning polylactic acid-based fabric (MFR-PBF) by coating MXene nanosheet, phytic acid @ furfurylamine (PA@FA) and ammonium polyphosphate (APP) via an eco-friendly layer-by-layer assembly method. MFR-PBF showed outstanding flame retardancy including a limiting oxygen index value of 35 % and better char formation capacity. More importantly, MFR-PBF exhibited sensitive fire early-warning capability (∼1 s) and excellent cyclic alarm stability (>15 cycles) due to the excellent semiconductor responsiveness (light and heat) and the significant catalytic char formation effect. Moreover, MFR-PBF is comfortable, flexible and strong enough to sew onto firefighter uniform to detect a variety of human motions, which can be monitored in the internet by using a LoRa emitter and a gateway. In addition, the controllable heating performance rendered MFR-PBF as a potential portable heater. This work provides new insights into the preparation and application of intelligent fire early-warning fabrics in the smart fire protection and Internet of Things.

Tailored Catalysis Inducing Exceptionally Fire-Safe and Mechanically Reinforced Epoxy at An Ultralow Loading.

An unconventional P/N/Si-free fire safety of epoxy at an ultralow loading with a significantly improved mechanical robustness and toughness via a mere nanocomposite technique is a great challenge. To achieve the goal, a proof of concept is proposed associated with a hierarchical manipulation of catalysis-tailored FexSy ultrathin nanosheets on organic-layered double hydroxide (LDH-DBS@FexSy) toward the formation of porous piling structure via a self-sacrificing conversion of metal-organic framework. A sufficient characterization certified the targeted architecture and composition. A P/N/Si-free ultralow loading of 2 wt % LDH-DBS@FexSy (i.e., 0.6 wt % FexSy) imparted epoxy with UL-94 V-0 rating, a 36.1% reduction of peak heat release rate, as well as a pronounced fire-protection feature. A systematic contrastive investigation evidenced a time-dependent fire-shielding effect induced by a featured catalysis-tailored ultrafast charring behavior at the interface of epoxy and LDH nanosheets. Intriguingly, the tensile strength, impact strength, and flexural strength were simultaneously enhanced by 62.2, 185.4, and 62.9%, respectively, with a 0.6 wt % incorporation of FexSy hierarchy on the basis of a "root-soil"-inspired interfacial "interlocking" structure. In perspective, an integrated manipulation of an interface catalysis-tailored ultrafast charring and hierarchical "interlocking" construction offer an effective balance of the fire safety, mechanical robustness, and toughness of polymers.

Metabarcoding read abundances of orchid mycorrhizal fungi are correlated to copy numbers estimated using ddPCR.

Quantifying the abundances of fungi is key to understanding natural variation in mycorrhizal communities in relation to plant ecophysiology and environmental heterogeneity. High-throughput metabarcoding approaches have transformed our ability to characterize and compare complex mycorrhizal communities. However, it remains unclear how well metabarcoding read counts correlate with actual read abundances in the sample, potentially limiting their use as a proxy for species abundances. Here, we use droplet digital PCR (ddPCR) to evaluate the reliability of ITS2 metabarcoding data for quantitative assessments of mycorrhizal communities in the orchid species Neottia ovata sampled at multiple sites. We performed specific ddPCR assays for eight families of orchid mycorrhizal fungi and compared the results with read counts obtained from metabarcoding. Our results demonstrate a significant correlation between DNA copy numbers measured by ddPCR assays and metabarcoding read counts of major mycorrhizal partners of N. ovata, highlighting the usefulness of metabarcoding for quantifying the abundance of orchid mycorrhizal fungi. Yet, the levels of correlation between the two methods and the numbers of false zero values varied across fungal families, which warrants cautious evaluation of the reliability of low-abundance families. This study underscores the potential of metabarcoding data for more quantitative analyses of mycorrhizal communities and presents practical workflows for metabarcoding and ddPCR to achieve a more comprehensive understanding of orchid mycorrhizal communities.

Size-focused conservation may fail to protect the world's oldest trees.

Old trees are irreplaceable natural resources that provide multifaceted benefits to humans. Current conservation strategies focus primarily on large-sized trees that were often considered old. However, some studies have demonstrated that small trees can be more than thousands of years old, suggesting that conventional size-focused perceptions may hamper the efficiency of current conservation strategies for old trees. Here, we compiled paired age and diameter data using tree-ring records sampled from 121,918 trees from 269 species around the world to detect whether tree size is a strong predictor of age for old trees and whether the spatial distribution of small old trees differs from that of large old trees. We found that tree size was a weak predictor of age for old trees, and diameter explained only 10% of the total age variance of old trees. Unlike large-sized trees that are mainly in warm, wet environments and protected, small old trees are predominantly in cold, dry environments and mostly unprotected, indicating that size-focused conservation failed to protect some of the oldest trees. To conserve old trees, comprehensive old-tree recognition systems are needed that consider not only tree size but also age and external characteristics. Protected areas designed for small old trees are urgently needed.

Bio-based chitosan-based film as a bifunctional fire-warning and humidity sensor.

Early fire detection is an efficient method to mitigate disastrous fire loss. However, developing smart low-temperature fire-warning sensors that better diminish fire hazards, especially those caused by household appliances, is still challenging. Herein, a salts-modified chitosan (salts-modified CS) based sensor with integrated fire-warning and humidity-monitoring capability is proposed using an easy assembling method. This sensor can respond to temperatures as low as 50 °C and a flame within 2 s quickly and detect relative humidity (RH) range above 50 % at 50 °C and 75 °C sensitively. This system can be reusable for multiple ignitions and works in high-humidity environments (>50 %). Furthermore, the comparison between different salts-modified CS films is carried out to elucidate the mechanism of the formation of electric current under the joint driven by temperature and humidity. Moreover, real-time temperature and RH monitoring can be achieved with a wireless transmission section. This design shows a promising approach for multifunctional CS-based sensors and paves a path to developing a new generation of smart fire-warning detectors.

Highly efficient metal-organic framework based intumescent poly(L-lactic acid) towards fire safety, ignition delay and UV resistance.

Developing multifunctional biodegradable PLA with ignition delay, high efficient fire retardancy, and UV resistance properties is a challenging task owing to its high flammability, and mutually exclusive phenomenon between the latter two properties. In this work, we report a superior efficient synergistic action combining piperazine pyrophosphate (PAPP) and a Co based metal-organic framework (ZIF-67). Results illustrated that with merely 0.06 wt% ZIF-67, intumescent PLA containing 4.96 wt% PAPP reached UL-94 V0 rating. The PLA/4.9PAPP/0.1MOF sample possessed a limiting oxygen index (LOI) value at 33 %, exhibited a 28 % reduction in peak heat release rate (pHRR) and a 67 % increase in fire propagation index (FPI). Moreover, the presence MOF delayed the ignition time of PLA by 12 s due to the highly porous structure of MOF and its chemical heat-sink performance. Insightful reaction to fire mechanism in the condensed phase via TG-FTIR and Raman revealed that a crack free protective intumescent char layer with higher graphitization degree was formed, which effectively enhanced the barrier effect and minimize the heat and fuel transfer. In addition, the UV resistance of PLA composites is enhanced, remaining at and below 5 % transmittance in the UVA and UVB areas. This work provides a green production way of multifunctional degradable materials and broadens their application fields.

Recent Progress on Multifunctional Thermally Conductive Epoxy Composite.

In last years, the requirements for materials and devices have increased exponentially. Greater competitiveness; cost and weight reduction for structural materials; greater power density for electronic devices; higher design versatility; materials customizing and tailoring; lower energy consumption during the manufacturing, transport, and use; among others, are some of the most common market demands. A higher operational efficiency together with long service life claimed. Particularly, high thermally conductive in epoxy resins is an important requirement for numerous applications, including energy and electrical and electronic industry. Over time, these materials have evolved from traditional single-function to multifunctional materials to satisfy the increasing demands of applications. Considering the complex application contexts, this review aims to provide insight into the present state of the art and future challenges of thermally conductive epoxy composites with various functionalities. Firstly, the basic theory of thermally conductive epoxy composites is summarized. Secondly, the review provides a comprehensive description of five types of multifunctional thermally conductive epoxy composites, including their fabrication methods and specific behavior. Furthermore, the key technical problems are proposed, and the major challenges to developing multifunctional thermally conductive epoxy composites are presented. Ultimately, the purpose of this review is to provide guidance and inspiration for the development of multifunctional thermally conductive epoxy composites to meet the increasing demands of the next generation of materials.

Novel insights into orchid mycorrhiza functioning from stable isotope signatures of fungal pelotons.

Stable isotope signatures of fungal sporocarps have been instrumental in identifying carbon gains of chlorophyllous orchids from a fungal source. Yet, not all mycorrhizal fungi produce macroscopic sporocarps and frequently fungi of different taxa occur in parallel in orchid roots. To overcome this obstacle, we investigated stable isotope signatures of fungal pelotons extracted from orchid roots and compared these data to the respective orchid and reference plant tissues. Anoectochilus sandvicensis and Epipactis palustris represented specialized or unspecialized rhizoctonia-associated orchids. Epipactis atrorubens and Epipactis leptochila are orchids considered ectomycorrhiza-associated with different preferences for Basidio- and Ascomycota. 13 C enrichment of rhizoctonia pelotons was minor compared with plant tissues and significantly lower than enrichments of pelotons from ectomycorrhizal Epipactis species. 15 N values of pelotons from E. leptochila and E. atrorubens showed similar patterns as known for respective sporocarps of ectomycorrhizal Ascomycota and Basidiomycota, however, with an offset towards lower 15 N enrichments and nitrogen concentrations. Our results suggest an explicit fungal nutrition source of orchids associated with ectomycorrhizal fungi, whereas the low 13 C enrichment in rhizoctonia-associated orchids and fungal pelotons hamper the detection of carbon gains from fungal partners. 15 N isotopic pattern of orchids further suggests a selective transfer of 15 N-enriched protein-nitrogen into orchids.

Metal-organic framework-derived bird's nest-like capsules for phosphorous small molecules towards flame retardant polyurea composites.

The loading treatment of phosphorus flame retardants can mitigate their migration and plasticization effect. However, designing suitable carriers has remained a great challenge. Herein, two kinds of Co-based isomers, namely cobalt-cobalt layered double hydroxides (CoCo-LDH) and cobalt basic carbonate (CBC), were synthesized by employing ZIF-67 as a self-template, assemblied into two different nanostructures namely multi-yolk@shell CBC@CoCo-LDH (m-CBC@LDH) and solid CBC nanoparticles by facilely tuning the reaction time, which were employed as carriers, respectively. Subsequently, triphenyl phosphate (TPP)-loaded m-CBC@LDH (m-CBC-P@LDH) was prepared using TPP as the guest. The m-CBC@LDH with high specific surface area and hollow structure exhibited up to more than 30% of TPP loading. The peak of heat release rate and total heat release of polyurea composite blended with 5 wt% m-CBC-P@LDH reduced by 41.7% and 20.6% respectively, and the mechanical properties were less damaged. This work complements a feasible approach for preparation of metal-organic frameworks-derived flame retardant carriers.

All-Fabric Triboelectric Nanogenerator (AF-TENG) Smart Face Mask: Remote Long-Rate Breathing Monitoring and Apnea Alarm.

Since the beginning of the COVID-19 pandemic, the use of face masks has become not only mandatory in several countries but also an acceptable approach for combating the pandemic. In the quest for designing an effective and useful face mask, triboelectric nanogenerators (TENGs) have been recently proposed. Novel functionalities are provided with the use of TENGs in face masks due to the induced triboelectrification generated by the exhaled and inhaled breath, allowing their use as an energy sensor. Nonetheless, within the face mask, the presence of nontextile plastics or other common triboelectric (TE) materials can be undesired. Herein, we propose the use of an all-fabric TENG (AF-TENG) with the use of high molecular weight polyethylene (UHMWPE) and cotton fabric as negative and positive triboelectric layers, respectively. With these materials, it is possible to detect the breathing of the patient, which in the case of not detecting a signal over a few minutes can trigger an alarm locally, providing valuable time. Also, in this article, we have sent breathing signals locally and remotely to distances up to 20 km via Wi-Fi and LoRa, the same as warning signals in the case of detecting anomalies. This work reveals the use of TENGs in smart face masks as an important tool to be used in difficult epidemiological periods to the general public, bringing much more comfort and relaxation to patients and elderly in today's society, and based on pristine eco-friendly materials.

Recent Advances on Early-Stage Fire-Warning Systems: Mechanism, Performance, and Perspective.

Early-stage fire-warning systems (EFWSs) have attracted significant attention owing to their superiority in detecting fire situations occurring in the pre-combustion process. Substantial progress on EFWSs has been achieved recently, and they have presented a considerable possibility for more evacuation time to control constant unintentional fire hazards in our daily life. This review mainly makes a comprehensive summary of the current EFWSs, including the working mechanisms and their performance. According to the different working mechanisms, fire alarms can be classified into graphene oxide-based fire alarms, semiconductor-based fire alarms, thermoelectric-based fire alarms, and fire alarms on other working mechanisms. Finally, the challenge and prospect for EFWSs are briefly provided by comparing the art of state of fire alarms. This work can propose a more comprehensive understanding of EFWSs and a guideline for the cutting-edge development direction of EFWSs for readers.

ZIF-67 In Situ Grown on Attapulgite: A Flame Retardant Synergist for Ethylene Vinyl Acetate/Magnesium Hydroxide Composites.

ZIF-67@ATP was prepared by the in situ growth of the zeolite imidazole frame (ZIF-67) on the surface of attapulgite (ATP). The structure and surface morphology of ZIF-67@ATP were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Different mass fractions of ATP and ZIF-67@ATP were added to ethylene vinyl acetate (EVA)/magnesium hydroxide (MH) composites as flame retardant synergists. The flame retardancy of EVA composites was evaluated by the limiting oxygen index (LOI) test, UL-94 test and cone calorimeter test. Composites containing 3 wt% of ZIF-67@ATP reached an LOI value of 43% and a V-0 rating in the UL-94 test, and the ignition time of the composite increased from 38 s to 56 s. The tensile strength and impact strength of the composites did not change significantly, but the elongation at break increased greatly. Typically, for composites containing 4 wt% of ZIF-67@ATP, the elongation at break of the composites increased from 69.5% to 522.2% compared to the samples without the synergist. This study provides novel insights into the application of attapulgite in the field of flame retardant polymer materials.

Synergistic Effect of Cerium Oxide for Improving the Fire-Retardant, Mechanical and Ultraviolet-Blocking Properties of EVA/Magnesium Hydroxide Composites.

Rare earth oxide particles have received important attention in recent years, and due to the wide diversity of promising applications, the need for this kind of material is predicted to expand as the requirements to use the current resources become more demanding. In this work, cerium oxide (CeO2) was introduced into ethylene-vinyl acetate (EVA)/magnesium hydroxide (MDH) composites for enhancing the flame retardancy, mechanical properties and anti-ultraviolet aging performance. The target EVA/MDH/CeO2 composites were prepared by extrusion and injection molding, and the effects of the addition of the CeO2 were explored by thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), limiting oxygen index (LOI), UL-94, cone calorimetry test, and anti-ultraviolet aging test. Typically, the incorporation of the CeO2 allows a significant increase of the elongation at break and Young's modulus compared with EVA/MDH by 52.25% and 6.85%, respectively. The pHRR remarkably decreased from 490.6 kW/m2 for EVA/MDH to 354.4 kW/m2 for EVA/MDH/CeO2 composite. It was found that the CeO2 presents excellent synergism with MDH in the composites for the anti-UV properties in terms of mechanical properties preservation. Notably, the combination of CeO2 with MDH is a novel and simple method to improve the filler-polymer interaction and dispersion, which resulted in the improvement of the mechanical properties, flame retardancy and the anti-ultraviolet aging performance of the composites.