Hollow Superstructure In Situ Assembled by Single-Layer Janus Nanospheres toward Electromagnetic Shielding Flame-Retardant Polyurea Composites.

A dodecahedral superstructure consisting of a single layer of Janus spheres containing ZIF-67 nanodots is prepared by in situ polymerization, with ZIF-67 and bio-based phytic acid (PA) as templates and dopants. It is used to improve the flame retardant, electromagnetic (EMI) shielding, and thermal conductivity properties of polyurea (PUA). By adding 5 wt% polyaniline@cobalt phytate-2.0 (PANI@Co-PA-2.0), the peak of heat release rate and the peak of smoke production rate are reduced by 54.9 and 59.9%, respectively. The peak of CO and CO2 production also decreased by 46.2 and 53.1%, respectively. A decrease in the absorption intensity of aliphatic and aromatic volatiles is also observed. The fire safety of PUA is greatly improved. In addition, PUA/PANI@Co-PA-2.0 exhibits an EMI shielding capability of 22.4 dB with the help of reduced graphene oxide, which confirms the possibility of PUA material application in the field of electromagnetic shielding. The 5 wt% filler increases the tensile strength of the PUA matrix to 6.3 MPa, and the composite material obtains good thermal conductivity. This work provides a viable method for the preparation of a flame-retardant, conductive, and electromagnetic refractory PUA substrate.

Joint Exfoliation of MXene by Dimensional Mismatched SiC/ZIF-67 Toward Multifunctional Flame Retardant Thermoplastic Polyurethane.

The single-layer MXene fully demonstrates the advantages of 2D materials, especially catalytic, conductive, and mechanical properties. However, the high energy consumption and low efficiency faced by MXene in the divestiture process are still challenges that need to be solved urgently. In this article, dimension mismatch and collaborative stripping strategies are skillfully combined to easily realize the transformation from multi-layer MXene to single layer. In addition, the functionalized MXene@SiC@polyaniline (MXene@SiC@PANI) nano-hybrid materials are used as fillers to improve the thermal conductivity, flame retardant, and antibacterial properties of thermoplastic polyurethane (TPU). The surface temperature of TPU/MXene@SiC@PANI composites increased from 33.4 °C to 59.8 °C within 10 s. In addition, the antibacterial efficiency of TPU composites against Escherichia coli and Staphylococcus aureus is 69.6% and 88.9%, respectively. Compared with pure TPU, the peak heat release rate and total heat release are reduced by 71.4% and 34.6%, respectively. The flame-retardant mechanism of MXene hybrid materials is systematically discussed. It is worth noting that the introduction of PANI enhances the compatibility between the filler and the polymer, effectively maintaining the mechanical properties of the TPU itself. This work provides a convenient method for the multi-functional practical application of TPU.

COF-Coated Microelectrode for Space-Confined Electrochemical Sensing of Dopamine in Parkinson's Disease Model Mouse Brain.

Parkinson's disease (PD) is a progressive neurodegenerative disorder causing the loss of dopaminergic neurons in the substantia nigra and the drastic depletion of dopamine (DA) in the striatum; thus, DA can act as a marker for PD diagnosis and therapeutic evaluation. However, detecting DA in the brain is not easy because of its low concentration and difficulty in sampling. In this work, we report the fabrication of a covalent organic framework (COF)-modified carbon fiber microelectrode (cCFE) that enables the real-time detection of DA in the mouse brain thanks to the outstanding antibiofouling and antichemical fouling ability, excellent analytical selectivity, and sensitivity offered by the COF modification. In particular, the COF can inhibit the polymerization of DA on the electrode (namely, chemical fouling) by spatially confining the molecular conformation and electrochemical oxidation of DA. The cCFE can stably and continuously work in the mouse brain to detect DA and monitor the variation of its concentration. Furthermore, it was combined with levodopa administration to devise a closed-loop feedback mode for PD diagnosis and therapy, in which the cCFE real-time monitors the concentration of DA in the PD model mouse brain to instruct the dose and injection time of levodopa, allowing a customized medication to improve therapeutic efficacy and meanwhile avoid adverse side effects. This work demonstrates the fascinating properties of a COF in fabricating electrochemical sensors for in vivo bioanalysis. We believe that the COF with structural tunability and diversity will offer enormous promise for selective detection of neurotransmitters in the brain.

Regulating Chemistry Composition on a Crystal Surface by Introducing a Cation Trapping Agent: A Novel Strategy to Tune Moisture Sensitivity of Crystals.

The crystal moisture sensitivity can be tuned by the chemical composition on the crystal surface. Ammonium dinitramide (ADN) crystal is a promising oxidizer for solid propellants. However, its strong moisture sensitivity greatly limits its practical applications. Here, we report a novel strategy to reduce moisture sensitivity by trapping ammonium cations with montmorillonite (MMT) to modulate the chemistry composition on the ADN crystal surface. An extraordinary phenomenon can be found: the crystal surface of the recrystallized ADN with 1% MMT (ADN-1% MMT) is rearranged with more low-surface-energy -NO2 groups (65.84%) and less high-surface-energy NH4+ groups (4.8%). In addition, ADN-1% MMT presents a more homogeneous low surface energy feature with a narrower surface energy distribution. As a result, ADN-1% MMT exhibits a noticeably lower hygroscopicity at 20 °C and 60% RH, which is accordant with the simulated hygroscopicity based on XRD and moisture sensitivity prediction based on surface energy. This study brings out a novel modification idea to adjust crystal moisture sensitivity by tuning the chemistry composition on the crystal surface based on trapping cations.

Potential Difference-Modulated Synthesis of Self-Standing Covalent Organic Framework Membranes at Liquid/Liquid Interfaces.

Covalent organic framework (COF) membranes with tailored functionalities hold great promise in diverse applications, but the key to realize their full advantages of highly ordered pore structures is the development of membrane fabrication approaches. In this work, we report a potential difference-modulated biphasic strategy to fabricate large-area, self-standing COF membranes under ambient conditions. The fabrication was conducted at the polarized water/1,2-dichloroethane (water/DCE) interface, where HCl was dissolved in water as a catalyst and monomers (both amine and aldehyde) were added to DCE. The external polarization of the water/DCE interface by cyclic voltammetry can continuously pump H+ from water to DCE to boost the Schiff base reaction of monomers and the growth of COF membranes. Moreover, the growth process can be real-time-monitored by interfacial double-layer capacitance measurement, and the permeability of COF membranes can be in situ-examined by heterogeneous ion transfer voltammetry. Given that the potential difference across the water/DCE interface can be also facilely modulated by dissolving proper electrolyte ions in two phases, the fabrication of large-area COF membranes is made possible in beakers. Using this strategy and different monomers, three types of centimeter-scale, free-standing COF membranes with tunable pore size and surface functionality were prepared, and their defect-free structure was proved by the molecular permeance and ultrafiltration test. We believe that this biphasic strategy offers a controllable and scalable way to fabricate COF membranes and sheds light on development of novel self-supporting membranes with unique functions.

Study on Interaction between Propargyl-Terminated Polybutadiene and Plasticizers Based on Simulation and Experiments.

Molecular dynamics (MD) simulation and experimental methods are used to explore the interaction between the propargyl-terminated polybutadiene (PTPB) binder and plasticizers bis(2,2-dinitropropyl) formal/acetal (BDNPF/A) and dioctyl sebacate (DOS). Flory-Huggins parameters, radial distribution functions, and binding energies between PTPB and plasticizers are calculated using MD simulations. The solubility parameters of PTPB and the plasticizers are calculated by both MD and group contribution method. The mesoscopic dynamics (MesoDyn) is used to simulate the meso-morphology of PTPB and plasticizer blends by converting the results of MD simulation into MesoDyn simulation parameters. The results of simulations and calculations show that PTPB has better compatibility with DOS than with BDNPF/A, and DOS is more suitable as a plasticizer for PTPB. The results of dynamic rheological experiments show that BDNPF/A has little effect on the dynamic viscosity of PTPB, and DOS can significantly reduce the dynamic viscosity of PTPB and has better plasticizing effect on PTPB. Differential scanning calorimetry and dynamic mechanical analysis tests indicate that the DOS and PTPB blend has only one glass transition temperature, while the PTPB and BDNPF/A blend has two glass transition temperatures. Both simulations and experimental results show that the PTPB binder have better compatibility with DOS than with BDNPF/A, and DOS has better plasticization effects on the PTPB binder.

Preparation and Characterization of Organic-Inorganic Hybrid Macrocyclic Compounds: Cyclic Ladder-like Polyphenylsilsesquioxanes.

Organic-inorganic hybrid macrocyclic compounds, cyclic polyphenylsilsesquioxanes (cyc-PSQs), have been synthesized through hydrolysis and condensation reactions of phenyltrichlorosilane. Structural characterization has revealed that cyc-PSQs consist of a closed-ring double-chain siloxane inorganic backbone bearing organic phenyl groups. The cyc-PSQ molecules have been simulated and structurally optimized using the Forcite tool as implemented in Materials Studio. Structurally optimized cyc-PSQs are highly symmetrical and regular with high stereoregularity, consistent with the dimensions of their experimentally derived structures. Thermogravimetric analysis showed that these macrocyclic compounds have excellent thermal stability. In addition to these perfectly structured compounds, macrocyclic compounds with the same ring ladder structure but bearing an additional Si-OH group, cyc-PSQs-OH, have also been synthesized. A possible mechanism for the formation of the closed-ring molecular structures of cyc-PSQs and cyc-PSQs-OH is proposed.

Nitric oxide contributes to minerals absorption, proton pumps and hormone equilibrium under cadmium excess in Trifolium repens L. plants.

Nitric oxide (NO) is a stress-signaling molecule in plants that mediates a wide range of physiological processes and responses to metal toxicity. In this work, various NO modulators (NO donor: SNP; NO scavenger: cPTIO; NO synthase inhibitor: l-NAME; and SNP analogs: sodium nitrite/nitrate and sodium ferrocyanide) were investigated to determine the role of NO in Trifolium repens L. plants exposed to Cd. Cd (100µM) markedly reduced biomass, NO production and chlorophyll (Chl a, Chl b and total Chl) concentration but stimulated reactive oxygen species (ROS) and Cd accumulation in plants. SNP (50µM) substantially attenuated growth inhibition, reduced hydrogen peroxide (H2O2) and malonyldialdehyde (MDA) levels, stimulated ROS-scavenging enzymes/agents, and mitigated the H(+)-ATPase inhibition in proton pumps. Interestingly, SNP considerably up-regulated the levels of jasmonic acid (JA) and proline in plant tissues but down-regulated the levels of ethylene (ET) in both shoots and roots and the level of salicylic acid (SA) in roots only, which might be related to the elevated NO synthesis. Additionally, SNP (25-200µM) regulated mineral absorption and, particularly at 50µM, significantly enhanced the uptake of shoot magnesium (Mg) and copper (Cu) and of root calcium (Ca), Mg and iron (Fe). Nevertheless, the effects of SNP on plant growth were reversed by cPTIO and l-NAME, suggesting that the protective effect of SNP might be associated with NO synthesis in vivo. Moreover, SNP analogs did not display roles similar to that of SNP. These results indicated that NO depleted Cd toxicity by eliminating oxidative damage, enhancing minerals absorption, regulating proton pumps, and maintaining hormone equilibrium.

Gold-Catalyzed C(sp3)-C(sp2) Suzuki-Miyaura Coupling Reaction.

A gold-catalyzed C(sp3)-C(sp2) Suzuki-Miyaura coupling reaction facilitated by ligand-enabled Au(I)/Au(III) redox catalysis was developed. The cross-coupling of alkyl organometallics was first realized in the redox catalytic cycle in gold chemistry, without the use of external oxidants. This gold-catalyzed C(sp3)-C(sp2) coupling reaction allows a variety of alkyl chain and useful methyl trifluoroborates to react with aryl and vinyl iodides under very mild conditions, which provides a new reactivity pattern for challenging couplings with alkyl organometallics.

Synthesis of Sulfonated Phenylsilsesquioxanes Guided by Machine Learning.

Sulfonated octaphenylsilsesquioxane (SPOSS) has garnered significant interest due to its unique structural properties of containing the -SO3H group and its wide range of applications. This study introduces a novel approach to the synthesis of SPOSS, leveraging machine learning algorithms to explore new recipes and achieve higher -SO3H functionality. The focus was on synthesizing SPOSS with 2, 4, 6, and 8-SO3H functional groups on the phenyl group, marked as SPOSS-2, SPOSS-4, SPOSS-6, and SPOSS-8, respectively. The successful synthesis of SPOSS-8 was achieved by 5 training outputs based on the recipes of 21 sets of low-functionality (<4) SPOSS. The structure of SPOSS was confirmed using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and time-of-flight mass spectrometry (MALDI-TOF MS). Machine learning analysis revealed that K2SO4 is an important additive to improve the functionality of SPOSS. A synthetic mechanism was proposed and validated that K2SO4 participated in the reaction to generate sulfur trioxide (SO3), a sulfonating agent with high reactivity. SPOSS shows thermal stability superior to octaphenylsilsesquioxane (OPS) according to thermogravimetric analysis (TGA) and TG-FTIR.

Photosensitized Reductive Elimination of Gold(III) to Enable Esterification of Aryl Iodides with Carboxylic Acids.

Compared to the well-established transition metal-catalyzed cross-coupling reactions, Au(I)/Au(III)-catalyzed cross-coupling reactions have lagged behind. Despite some advancements, achieving gold-catalyzed C-O coupling with carboxylic acids via an Au(III) carboxylate intermediate remains challenging due to the thermal unfavorability of the critical reductive elimination step. Here, we present the first photosensitized reductive elimination of gold(III) to enable esterification of aryl iodides with carboxylic acids. In the presence of a (P, N)-gold(I) catalyst and a photosensitizer benzophenone under blue LED irradiation, esterification derivatives were obtained from aryl iodides with both aryl and alkyl (1°, 2°, 3°) carboxylic acids. Mechanistic and modeling studies support that energy transfer (EnT) from a photosensitizer produces an excited-state gold(III) complex that couples aryl iodides with carboxylic acids. This photoinduced energy-transfer strategy has been applied in several other photosensitized gold catalysis reactions, indicating its potential for further applications.

Base-assisted transmetalation enables gold-catalyzed oxidative Sonogashira coupling reaction.

The traditional transition metal catalyzed neutral C(sp)-C(sp2) cross-coupling reaction between a nucleophile and an electrophile is a key technique for the formation of carbon-carbon bonds. Herein, we present a general gold-catalyzed oxidative Sonogashira cross-coupling of arylboronic acids and terminal arylalkynes at room temperature with excellent functional-group tolerance and good chemoselectivity. Moreover, our mechanistic studies suggested a third pathway involving a base-assisted transmetalation between the gold(I) catalyst and aryl boronic acid might predominate in our reaction conditions, rather than the previously assumed oxidation of the gold(I) complex or deprotonation of alkynes.

Dual function of carboxymethyl cellulose scaffold: A one-stone-two-birds strategy to prepare double-layer hollow ZIF-67 derivates for flame retardant epoxy composites.

Aluminum hypophosphite (AHP) has been used as a flame retardant for a long time. Previous studies about AHP employed in flame retardant materials mostly focus on coating, modification, and complex system. It is valuable to explore simple experimental steps to prepare nano hybrids with AHP and metal-organic frameworks (MOFs). We found acidic substances could etch zeolitic imidazolate framework-67 (ZIF-67) to obtain MOF derivatives. Unfortunately, AHP and ZIF-67 could not directly form a hybrid. Therefore, carboxymethylcellulose (CMC) is introduced as a dual function layer (buffer and support). The CMC resists the complete conversion of ZIF-67 etched by phosphoric acid to amorphous cobalt phosphate hydrate (ACP). Meanwhile, CMC containing hydroxyl groups combines with AHP through electrostatic interaction and coordination bonds. A double-layer hollow MOF derivative is synthesized through this one-stone-two-birds strategy. Due to multiple flame retardant elements and unique nanostructure, this MOF derivative endows epoxy (EP) resin with excellent flame retardancy. With 2.0 wt% addition, the peak heat release rate (pHRR) and total heat release (THR) of EP/AHP/ACP@CMC are decreased by 47.8 and 21.0 %, respectively. This study proposes a novel scheme that converts AHP into MOF derivatives as high-performance FRs.

A Gas-Steamed Route to Mesoporous Open Metal-Organic Framework Cages Enhancing Flame Retardancy and Smoke Suppression of Polyurea.

Up to now, metal-organic frameworks (MOFs) with open nanostructures have shown outstanding capabilities in trapping smoke particles compared to the original MOFs. However, only a few MOF-based strategies have been reported to synthesize hierarchical porous cages thus far, which are mainly restricted to environmentally unfriendly wet-chemical liquid methods. Herein, as a proof-of-concept, a gas-steamed metal-organic framework approach was designed to fabricate a series of cheeselike open cages with hierarchical porosity. Briefly, zeolitic imidazolate framework-67 (ZIF-67) and phytic acid were employed as precursor and etchant, respectively. Abandoning the conventional wet-chemical method, the coordination bond of ZIF-67 was cleaved by acidic steam, forming an open framework with a high specific surface area and a hierarchical porous structure. The universality of this method was also confirmed by the selection of different etchants. Impressively, they also show outstanding fume-toxic adsorption capability and labyrinth effects based on abundant and complex porous channels. At only 5 wt % loading, Co3O4@open ZIF-67 cage-2 (Co3O4@OZC-2) imparted polyurea (PUA) composites with a 21.2% limiting oxygen index, and the peak of heat release rate, total heat release, and total smoke production were reduced by around 37.5, 25.5, and 40.4%, respectively, compared to neat PUA. This work will shed light on the advanced structural design of polymer composites with high fire safety, especially smoke suppression performance, so as to obtain more feasible applications.

Silicon Hybrid EPDM Composite with High Thermal Protection Performance.

The effects of octaphenylsilsesquioxane (OPS), fumed silica, and silica aerogel on the thermal insulation properties of ethylene propylene diene monomer (EPDM) rubber were studied. On this basis, two kinds of fillers with good performances were selected to study the thermal insulation of an EPDM full-formula system. The results show that the addition of fumed silica or silica aerogel had a positive effect on the thermal insulation performance of EPDM rubber and its composite. A 30 wt% silica aerogel can be well dispersed in the EPDM rubber system and with a lower thermal conductivity compared with fumed silica. EPDM composite with 23.4 wt% fumed silica can produce more char residues at 1000 °C than at 500 °C in a burn-through test and formed the compact and porous char at 1000 °C, which had a lowest thermal conductivity. EPDM composite with fumed silica cannot be burned through 1000 °C burning, and comparison with silica aerogel revealed that it achieved the lowest back temperature and had a temperature of 388 °C after 800 s.

Enhancing char formation of flame retardant epoxy composites: Onigiri-like ZIF-67 modification with carboxymethyl ß-cyclodextrin crosslinking.

To enhance char formation of flame retardant epoxy (EP) composites, carboxymethyl ß-cyclodextrin (CM-ß-CD) is employed as an etchant for or ZIF-67 derivatives. In the early stage, etching plays a dominant role. The mismatch in size between CM-ß-CD opening and ZIF-67 pore leads to the stacking of carboxyl cobalt complexes on the shell. When the reaction time is prolonged, crosslinking occurs between carboxyl and hydroxyl groups. Crosslinked CM-ß-CD weakens and eventually stops the etching process. Triethyl phosphate (TEP), an additive to improve flame retardancy, is also absorbed on the shell in this one-pot synthesis. Herin, the synthesis of metal-organic framework (MOF) derivatives can impart multiple functions to MOF. This novel nanohybrid significantly improved flame retardancy of EP composites with only 2.0 wt% loading. The peak heat release rate (pHRR) and total smoke production (TSP) were reduced by 54.8 and 46.9%, respectively. The integrated multi-element system resulted in an expanded and reinforced char layer. This study proposes a simple and precise method for controlling the structure of MOF-carbohydrate hybrids through competition between chemical reactions.

Structure of Metal-Organic Frameworks Eco-Modulated by Acid-Base Balance toward Biobased Flame Retardant in Polyurea Composites.

Biobased-functionalized metal-organic frameworks (Bio-FUN-MOFs) stand out from the crowd of candidates in the flame-retardant field due to their multipathway flame-retardant mechanisms and green synthesis processes. However, exploring and designing Bio-FUN-MOFs tend to counteract the problem of compromising the flame-retardant advantages of MOFs themselves, which inevitably results in a waste of resources. Herein, a strategy in which MOFs are ecologically regulated through acid-base balance is presented for controllable preparation of Bio-FUN-MOFs by two birds with one stone, i.e., higher flame-retardant element loading and retention of more MOF structures. Specifically, the buffer layer is created on the periphery of ZIF-67 by weak etching of biobased alkali arginine to resist the excessive etching of ZIF-67 by phytic acid when loading phosphorus source and to preserve the integrity of internal crystals as much as possible. As a proof of concept, ZIF-67 was almost completely etched out by phytic acid in the absence of arginine. The arginine and phytic acid-functionalized ZIF-67 with yolk@shell structure (ZIF@Arg-Co-PA) obtained by this strategy, as a biobased flame retardant, reduces fire hazards for polyurea composites. At only 5 wt % loading, ZIF@Arg-Co-PA imparted polyurea composites with a limiting oxygen index of 23.2%, and the peaks of heat release rate, total heat release, and total smoke production were reduced by 43.8, 32.3, and 34.3%, respectively, compared to neat polyurea. Additionally, the prepared polyurea composites have acceptable mechanical properties. This work will shed light on the advanced structural design of polymer composites with excellent fire safety, especially environmentally friendly and efficient biobased MOF flame retardants.

Synchronous modification of ZIF-67 with cyclomatrix polyphosphazene coating for efficient flame retardancy and mechanical reinforcement of epoxy resin.

Cyclomatrix polyphosphazenes have attracted widespread attention in the field of polymer flame retardancy. Nevertheless, the optimal manifestation of their distinctive structural attributes and flame-retardant properties necessitates a judicious selection of condensation monomers and synergistic templates during the fabrication of polyphosphazene flame retardants. In our previous studies, it was discovered that when ZIF-67 is functionalized with polyphosphazene, the by-product HCl from phosphazene polycondensation causes etching on ZIF-67. Based on this "synchronous etching" effect, a series of hybrid materials comprising cyclomatrix polyphosphazene and ZIF-67, denoted as ZIF-67@PDS (PDS, poly-(cyclotriphosphazene-co-4,4'-diaminodiphenyl sulfone)), ZIF-67@PBS (PBS, poly-(cyclotriphosphazene-co-Bisphenol A)), and ZIF-67@PZS (PZS, poly-(cyclotriphosphazene-co-4,4'-sulfonyldiphenol)), was synthesized utilizing DDS (4,4'-diaminodiphenyl sulfone), BPA (Bisphenol A), and BPS (4,4'-sulfonyldiphenol) monomers as precursors, respectively. Upon the incorporation of 2.0 wt.% of ZIF-67@PDS, ZIF-67@PBS, and ZIF-67@PZS, the flame retardant and mechanical characteristics of EP composites exhibited marked enhancement. The unique structural characteristics of hybrid and the synergistic effects of Co-P-N contribute to the improvement of comprehensive properties. Compared with pure EP, EP/ZIF-67@PZS has the best enhancement effect, and its pHRR, THR, and TSP decreased by 34.0%, 30.0%, and 40.5%, respectively. In terms of mechanical strength, ZIF-67@PZS also increases the flexural strength of EP by 37.42%. Relying on the "synchronous etching" effect, this study explores and verifies the effective combination of ZIF-67 and different types of polyphosphazenes, and obtains a series of ZIF-67-derived cyclomatrix polyphosphazene hybrids with different morphologies and properties in one step. It provides a new idea and strategy for the simultaneous modification of polyphosphazene materials and the preparation of multifunctional flame retardants in the future.

The shifting pattern of CO2 source sink in a subtropical urbanizing lightly eutrophic lake.

Globally, numerous freshwater lakes exist, and rapid urbanization has impacted carbon biogeochemical cycling at the interface where water meets air in these bodies. However, there is still a limited understanding of CO2 absorption/emission in eutrophic urbanizing lakes. This study therefore involved biweekly in-situ monitoring to evaluate fluctuations in the partial pressure (pCO2) and flux (fCO2) of CO2 and associated parameters from January to September 2020 (7:00-17:00 CST) in an urbanizing lake in southwestern China. Our study revealed that during the daylight hours of the 11 sampling days, both pCO2 and fCO2 consistently demonstrated decreasing trends from the early morning period to the late afternoon period, with notable increases on May 7th and August 15th, respectively. Interestingly, unlike our previous findings, an nonsignificant difference (p > 0.05) in mean pCO2 and fCO2 was observed between the morning period and the afternoon period (n = 22). Furthermore, the mean pCO2 in January (~105 µatm; n = 4) and April (133-212 µatm; n = 8) was below the typical atmospheric CO2 level (C-sink), while that in the other months surpassed 410 µatm (C-source), although the average values (n = 44) of pCO2 and fCO2 were 960 ± 841 µatm and 57 ± 85 mmol m-2 h-1, respectively. Moreover, the pCO2 concentration was significantly greater in summer (May to August, locally reaching 1087 µatm) than in spring (January to April at 112 µatm), indicating a seasonal shift between the C-sink (spring) and the C-source (summer). In addition, a significant positive correlation in pCO2/fCO2 with chlorophyll-a/nitrate but a negative correlation in dissolved oxygen and total phosphorus were recorded, suggesting that photosynthesis and respiration were identified as the main drivers of CO2 absorption/emissions, while changes in nitrate and phosphorus may be attributed to urbanization. Overall, our investigations indicated that this lightly eutrophic lake demonstrated a distinct shifting pattern of CO2 source-sink variability at daily and seasonal scales.

Effect of Brucea javanica Oil on the Toxicity of ß-Cypermethrin Emulsifiable Concentrate Formulation.

Enhancing the performance of traditional pesticide formulations by improving their leaf surface wetting capabilities is a crucial approach for maximizing the pesticide efficiency. This study develops an emulsifiable concentrate (EC) of 4.5% ß-cypermethrin containing Brucea javanica oil (BJO). The incorporation of BJO aims to improve the leaf-wetting properties of the EC formulation and enhance its insecticidal effectiveness. The droplet size and emulsion characteristics of ß-CYP EC emulsion with varying concentrations of the emulsifier were evaluated, and changes after incorporating BJO were assessed to develop the optimal formulation. A comprehensive comparison was conducted among commercial 4.5% ß-cypermethrin EC (ß-CYP EC-1), 4.5% ß-cypermethrin EC with BJO (ß-CYP EC-2), and 4.5% ß-cypermethrin EC without BJO (ß-CYP EC-3). This comparison encompassed various factors including storage stability, insecticidal activity, cytotoxicity, and wetting performance on cabbage leaves. The results indicated that the ideal emulsifier concentration was 15% emulsifier 0201B. ß-CYP EC-2 demonstrated superior wetting properties on cabbage leaves (the wetting performance of ß-CYP EC-2 emulsion on cabbage leaves is 2.60 times that of the ß-CYP EC-1 emulsion), heightened insecticidal activity against the third larvae of Plutella xylostella [diamondback moth (DBM)] [the insecticidal activity of the ß-CYP EC-2 emulsion against the third larvae of DBM is 1.93 times that of the ß-CYP EC-1 emulsion (12 h)], and more obvious inhibitory effects on the proliferation of DBM embryo cells than the other tested formulations. These findings have significant implications for advancing pest control strategies and promoting sustainable and effective agricultural practices.