Bridging Effect Research Articles

Nature-inspired approach for enhancing the fracture performance of 3D printed strain-hardening cementitious composites (3DP-SHCC)

3D printing technology enhances design flexibility, enables the creation of complex geometrical structures, facilitates rapid prototyping, and allows the fabrication of micro- and macroscopic structures. This study investigates the use of 3D concrete printing to create Bouligand structures inspired by mantis shrimp. Bouligand-printed strain-hardening cementitious composites (SHCC) with different pitch angles (15°, 30°, 45°, 60°, 75°, and 90°) are fabricated and compared with traditional parallel-printed and mold-cast SHCC. The fracture behavior of these specimens is investigated through three-point bending tests on notched beams. The results reveal that Bouligand-printed specimens exhibit enhanced flexural strength, fracture energy, and fracture toughness, ranging from 0.97 to 1.29 times, 0.99 to 1.63 times and 0.87 to 1.47 times that of the mold-cast specimens, respectively. Bouligand-printed specimens with a pitch angle of 30° exhibits the highest flexural strength, fracture energy, and fracture toughness. The Bouligand-printed SHCC enhance toughness through the synergistic effects of crack twisting and bridging. A finite element model integrating cohesive elements with the concrete plastic damage model is developed to numerically replicate the experimental process. This study highlights the potential of 3D concrete printing for the fabrication of biomimetic concrete structures with superior fracture performance.

Production and characterization of efficient bioflocculant in high-turbidity drinking water treatment: Identification of flocculation-related genes

Bioflocculants are eco-friendly water treatment agents produced by bioflocculant-producing strains that are valuable in drinking water turbidity removal. The major challenges in the application of bioflocculants include low flocculation efficiency, high production costs, and unclear flocculation-related genes. In this study, Pseudomonas sp. ZC-41 a highly efficient bioflocculant-producing strain, was isolated from activated sludge to produce polysaccharide-based bioflocculant MBF-ZC with 94.12% flocculation efficiency under more economical culture conditions, which can solve the problem of low flocculation efficiency. Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed MBF-ZC contained hydroxyl, carboxyl, and amine groups, crucial for flocculation via adsorption bridging effects as the main flocculation mechanism. The 2393 differentially expressed genes (DEGs) in the transcriptome of strain ZC-41 were classified into five co-expression modules, and the turquoise module was associated with flocculation efficiency and bioflocculant yield. Nineteen flocculation-related genes were identified by combining functional pathways related to sugars. In addition, response surface methodology was optimized to achieve the efficiency of 93.57% for turbidity removal from high-turbidity water by bioflocculant. The results not only provide a solid theoretical foundation to solve the challenges of bioflocculants, but also enrich strategies for high-turbidity drinking water treatment.

Numerical assessment of thermal bridging effects in 3D-printed foam concrete walls

Abstract Integrating smart technology and advanced materials in the construction industry has revolutionized traditional building practices, enhancing efficiency, sustainability, and overall performance. Researchers and professionals in the construction sector have shown significant interest in three-dimensional concrete printing (3DCP) for automating structural engineering tasks. Despite its potential as a sustainable solution to modern construction issues, there is a lack of research on the thermal insulation performance of three-dimensional printed concrete (3DPC) building envelopes, and the potential for integrating foam concrete (FC) to enhance energy efficiency has not yet been studied. This paper presents a numerical analysis examining how different infill geometries affect the thermal performance of 3D-printed foam concrete (3DPFC) lattice envelopes. Six lattice structures were designed with identical thickness, height, length, and comparable insulation areas. The effects of the contact (intersection) area of webs with the interior face shell, webs, and infill rows on the thermal performance of granularly insulated envelopes were studied. The effectiveness of insulation was also established. The findings indicate that the thermal transmittance of 3DPC envelopes correlates directly with the contact area of the webs and the interior surface, with U-values ranging from 0.151 W m2·K to 0.652 W/m2·K. Notably, the absence of direct connections between exterior and interior surfaces enhances insulation efficiency, with double-row structures achieving up to 94% insulation efficiency. However, when there is a direct connection between the two surfaces, the thermal performance of these envelopes is mainly affected by the contact (intersection) area of the webs with the interior face rather than the number of webs. By integrating foam concrete and double-row walls, this study demonstrates an innovative approach to reducing thermal bridging and improving energy performance in 3D-printed construction. The results offer novel insight into optimizing the thermal behavior of 3DPC systems for sustainable building practices.

Dynamic 3D hydrogen-bond network in siloxene-water system enables efficient moisture-enabled electricity generation

Utilizing ubiquitous moisture as an energy source for moisture-enabled electric generator (MEG) has emerged as a significant technological frontier. The migration process of protons at the water/solid interface is crucial for understanding the mechanism of moisture-to-electricity conversion and efficient energy harvesting. However, the lack of clarity on this scientific question has hindered the substantive development of MEG. Here, a novel dynamic three-dimensional (3D) hydrogen-bond network between the interface of siloxene layers was designed through water molecule intercalation. The spatial bridging effect of this dynamic 3D hydrogen-bond network, formed on the siloxene layers, enhances the load transfer capability of the siloxene-water system, thereby randomizing the direction of proton hopping. Experimental and theoretical calculations demonstrate that the dynamic 3D hydrogen-bond network constructed within and between the siloxene layers facilitates rapid proton conduction. Kinetic simulations further confirm that the strength of the hydrogen-bond network accelerates proton transport rate. The current density of siloxene under high humidity increases significantly, reaching 22.37 µA cm−2, which is 122 times that under low humidity, as well as the open-circuit voltage reaches 0.73 V. This work contributes to understanding the microscopic mechanisms behind efficient moisture-enabled electricity and provides a fresh perspective for enhancing MEG performance.

Mechanical properties and dynamic compression behaviour of basalt/polypropylene fibre-reinforced high-strength concrete

Concrete is a typical brittle material. Although it has excellent compressive performance, it can be damaged by dynamic loads such as explosions and impacts due to its poor tensile strength and cracking susceptibility. In an attempt to improve the impact resistance of concrete, a ∅100 × 50 split Hopkinson pressure bar was used to carry out impact tests on high-strength concrete (HSC) specimens with different volume contents (0.1%, 0.3% and 0.5%) of basalt fibre (BF) or polypropylene fibre (PPF) under three different impact pressures. The compressive strength, splitting tensile strength, flexural strength and dynamic compression performance of BF/PPF-reinforced HSC (C60) were studied. With an increase in impact pressure, increasing the volume content of fibre significantly improved the impact resistance of the concrete, due to the crack resistance and bridging effects of the fibre. The BF and PPF were found to be sensitive to the strain rate. Within a certain range of strain rate, the relationship between peak stress and strain rate was positively correlated. Dynamic stress–strain curves of concretes with optimal dosages of BF and PPF were obtained through dynamic compression tests.

Flexural behavior of concrete reinforced with micro basalt fibers and BFRP minibars

The use of basalt fibers as the reinforcement for concrete is an effective and eco-friendly solution to improve the ductile behavior and flexural toughness. For this purpose, an experimental investigation was conducted, where the concrete reinforced with micro basalt fibers or BFRP minibars were adopted. The morphologies of micro basalt fibers, straight, twisted and crimped BFRP minibars were analyzed for optimal enhancement effect. Also, the fiber length of 20 mm, 35 mm and 50 mm and fiber volume fraction of 0.5 %, 1 %, 2 % and 3 % were investigated. In addition, stiffer steel and softer polypropylene fibers were introduced to evaluate the effect of fiber modulus on concrete properties. The failure modes, load-deflection curves, fracture energy, flexural toughness and factor analysis were illustrated. The results show that the addition of micro basalt fibers with fiber lengths of 50 mm and volume fraction of 1 % increased the initial cracking strength by 28.8 %. Concrete reinforced with BFRP minibars with 50 mm in length and 1 % in volume fraction, has a flexural toughness ratio of 99.0 % of commercial steel fibers and a flexural toughness index (I5) of 113 % of commercial steel fibers. Based on the parametric analysis, the optimum length of BFRP minibars was 35 mm and the optimum fiber volume fraction was not more than 2 %. The prediction model for stress deflection response with high precision was proposed with regression coefficients ranging from 0.909 to 0.988. It was concluded that micro basalt fibers prevented the generation of microcracks through the bridging effect, whereas macrocracks and deep source cracks generated after concrete cracking were inhibited by BFRP minibars. The understanding of what exactly constitutes an optimal selection of fibers capable of producing maximum flexural properties of concrete was of great significance in engineering applications.

Fabrication of boron nitride/copper oxide@multi-walled carbon nanotubes composites for enhancing heat transfer and photothermal conversion of phase change materials

To realize the efficient storage and conversion of solar energy by phase change materials (PCMs), low photothermal conversion efficiency and poor heat transfer performance remain great challenges. Herein, polyethylene glycol (PEG)-based composite PCMs with excellent photothermal conversion performance and exceptional thermal management capability were obtained by using boron nitride/copper oxide@multi-walled carbon nanotubes (BN/CuO@MWCNTs) as the thermal conductive and photothermal conversion enhancement fillers. The results indicate that owing to the bridging effect, the introduction of CuO and MWCNTs on the BN surface can construct additional heat transfer paths, resulting in a high thermal conductivity of up to 2.35 W/(m·K) for the as-prepared PEG/BN/CuO@MWCNTs composite, which is about 9-folds enhancement than pristine PEG. Simultaneously, the supercooling degree of PEG in PEG/BN/CuO@MWCNTs is effectively suppressed due to the synergistic nucleation effect of BN, CuO and MWCNTs. Additionally, the PEG/BN/CuO@MWCNTs composites not only exhibit a high latent-heat capacity of 154.5 J/g and a high photothermal conversion efficiency of 92.2 %, but also show favorable shape stability and durable reliability. This work offers a workable solution for the synergistic enhancement of photothermal conversion and thermal management, which can effectively promote the practical application in solar energy conversion and storage.

Evaluation of basalt fibers and nanoclays to enhance extrudability and buildability of 3D-printing mortars

A study of the rheological and fresh mechanical properties of fly ash-cement 3D printing (3DP) mortars with six types of nanoclays (NC) as rheology modifiers, two sepiolites, three attapulgites and one bentonite, and reinforced with short basalt fibers (BF) was carried out. Fresh mortar properties were evaluated with a flow table test (FTT), cylindrical slump test (CST) and cone-penetration test (CPT) on samples left at rest and stirred before testing. Squeeze test (SQT) was carried out on samples cast-in-the-mold and 3D printed to compare the effects of 3DP on the fresh mechanical behavior. Extrudability was assessed with an electrical barrel extrusion device. NC and BF enhanced mortar cohesion by preventing water drainage and improving material extrudability. NC increased shear yield stress (τ0) over time on samples left at rest, enhancing reversible thixotropy. Besides, NC required larger amounts of superplasticizer, increasing open time windows. Among NC, Sepiolite in powder form showed the best fresh mechanical performance on 3DP samples. BF enhanced extrudability due to the bridging effect but also shows mechanical synergies with some NC. 3DP samples showed lower compressive yield stress and Young modulus evolution over time (σ˙ and Ė) than cast-in-the-mold samples, due to their layered structure.

Empirical Study on the Development of Digital Inclusive Finance on Narrowing the Consumption Gap between Urban and Rural Areas--Taking Shanxi Province as an Example

Based on the panel data of 11 cities and regions in Shanxi Province from 2011 to 2020, the study empirically investigates the impact of digital financial inclusion on the urban-rural consumption gap in Shanxi Province from the perspective of the overall effect and regional effect of digital financial inclusion development. The study finds that, in general, digital inclusive finance has narrowed the consumption gap between urban and rural residents through the high-quality features of low threshold and accessibility, from the perspective of regional heterogeneity, the uneven development of digital inclusive finance has led to significant differences in its effect on the consumption gap between urban and rural residents among regions, showing the characteristics of a ladder with a high level in the south and a low level in the north, and from the perspective of structural heterogeneity, the structure of digital inclusive finance development also has a significant impact on the consumption gap between urban and rural residents in Shanxi Province. From the perspective of structural heterogeneity, the impact of the development structure of digital inclusive finance on the consumption gap between urban and rural residents in Shanxi Province also varies, with the breadth of coverage bringing better bridging effects than the depth of use, while the degree of digitization creates the problem of digital divide and widens the consumption gap, finally, relevant suggestions are put forward with a view to narrowing the consumption gap between urban and rural areas and promoting the coordinated development of urban and rural areas.

Temperature-dependent R-curve and traction-separation relation in mode-I fracture of GFRP laminates

The R-curve and fiber bridging phenomenon in mode-I fracture of glass-fiber reinforced laminates at different temperatures are investigated in this study, aiming to reveal their changes with temperature. The mode-I fracture experiments are carried out by adopting double cantilever beam (DCB) configuration at −55 ℃, 23 ℃ and 80 ℃. Fiber bridging is observed during the tests. The R-curve and bridging traction are quantitatively analyzed, from which the relationship between the R-curve and fiber bridging phenomenon, and temperature is obtained. It is found that fiber bridging effect is enhanced with the increase of temperature. The bridging traction of specimens tested at 80 ℃ is significantly higher than that at −55 ℃ and 23 ℃. An R-curve model considering both temperature and fiber bridging effects is proposed. In addition, bilinear and tri-linear traction-separation relations (TSLs) are utilized to establish a numerical model for the simulation of delamination growth behavior with the consideration of the temperature-dependent effect on the mechanical properties of composite materials. When using the bilinear TSL, the fiber bridging is considered by integrating the resulted R-curve into finite element model via a user-defined USDFLD subroutine. Effects of initial interface stiffness, interface strength and viscosity coefficient on simulated results are numerically investigated. Finally, applicability of the established numerical models is illustrated by comparisons between the simulations and the test results.

Electro-coagulation pretreatment for improving nanofiltration membrane performance during reclamation of microplastic-contaminated secondary effluent: unexpectedly enhanced membrane fouling and mechanism analysis by MD-DFT simulation

The residue of microplastic in secondary effluent was inevitable with continuous aggravation on nanofiltration membrane fouling. Thus, this study aimed to further evaluate the applicability of electro-coagulation as pretreatment for improving the performance of a nanofiltration-oriented hybrid process during the reclamation of microplastic-contaminated secondary effluent. The electro-coagulation parameters were skillfully optimized and designed for following dynamic nanofiltration experiments. The potential influence of coagulants in different forms as well as their combined effects of microplastics on membrane fouling behaviors and pollutant rejection efficiency was distinguished. Specifically, terminal membrane permeability was reduced by 19% after 0.05 A electro-coagulation, while 0.2 A electro-coagulation almost eliminated the negative effects of microplastics. Mass transfer model analysis excluded the dominance of organic accumulation in the concentration polarization layer on membrane fouling development. Molecular dynamic (MD) simulation and egg-box model demonstrated that humic-Fe network possessed stronger bridging effects and greater porosity. This structure favored the co-deposition of other unlinked bacteria metabolites, which secretion was also facilitated by microplastics as immobilized carriers, on membrane surface. Additionally, density functional theory (DFT) calculation further confirmed that the greater demand for dehydration energy for ferric ions (1124 kcal/mol) inspired the formation of stronger humic-Fe complexes. Besides, residual microplastics in electro-coagulation effluent had different impacts on membrane rejection towards organic and inorganic pollutants, and it depended on the influenced cake-enhanced concentration polarization (CECP) by microplastic affinity with different pollutants.

The effects of myocardial bridging on two-dimensional myocardial strain during dobutamine stress echocardiography

Myocardial bridging (MB) is a common anatomic variant in coronary arteries with unclear functional significance. We evaluated regional myocardial strain by speckle tracking during dobutamine stress echocardiography (DSE) in patients with MB in the left anterior descending coronary artery (LAD). We studied 11 patients with MB in the LAD and no obstructive coronary artery disease (CAD), 7 patients without MB, but obstructive CAD in the LAD, and 12 controls without MB or obstructive CAD. MB was defined as either > 1 mm (superficial) or > 2 mm (deep) intramyocardial course of the LAD in coronary CT angiography. Regional longitudinal, radial and circumferential strains and strain rates as well as post-systolic strain index (PSI) were measured at rest, peak stress, and early recovery (1 min after stress). Strain parameters during DSE were similar in the myocardium distal to MB and other myocardial regions of the same patients as well as the LAD territory in controls. However, patients with obstructive CAD showed impaired LS and strain rate as well as increased PSI at peak stress. None of the MB was associated with systolic compression in invasive coronary angiography and strain parameters were similar between superficial and deep MB. Stress myocardial blood flow by positron emission tomography correlated with LS and RS at peak stress in the myocardium distal to MB (r = − 0.73, p = 0.03, and r = 0.64, p = 0.04, respectively). Myocardial strain is not reduced during DSE in patients with MB in the LAD and no significant systolic compression.

Tri-source integrated adenosine triphosphate complexed copper ions anchored to boron nitride surfaces for enhancing flame protection of waterborne epoxy coatings

The abundant C, P, and N elements in the structure of adenosine triphosphate (ATP) can act as carbon, acid, and gas sources, and thus can be used as an efficient intumescent flame retardant. Here, a layer of polydopamine (PDA) with polyhydroxyl groups was firstly loaded on the surface of BN to provide a bridging effect for the surface modification of BN. Then, ATP-Cu was immobilized on the BN surface by complexation of ATP with Cu2+, resulting in an efficient inorganic-organic-metal composite flame retardant (BNP@ATP-Cu). This composite flame retardant effectively combined the high barrier effect of BN, the high swelling property of ATP and the catalytic carbon formation activity of Cu2+. The experimental results revealed that the EP loaded with BNP@ATP-Cu showed the lowest backside temperature (171.2 °C), indicating the highest thermal barrier effect. Moreover, BNP@ATP-Cu/EP exhibited the most significant swelling characteristics (22.7 mm, 17.46) and smoke suppression effect (42.8 %). In contrast, the carbon residue of BNP@ATP-Cu/EP (30.8 %) was significantly higher than that of the other coated samples, which was related to the combined effect of BN and ATP-Cu. The above relevant results fully demonstrated the effectiveness of the composite flame retardants in improving the fire resistance of epoxy coatings.

Biomimetic structure-driven high strength and toughness in continuous SiC skeleton-reinforced graphite composites

Graphite-matrix structural composites with excellent mechanical properties and long-term reliability are ungently required in aerospace and nuclear industries. However, the enhancement of graphite-matrix composites by mainstream surface coating techniques or second-phase particle reinforcement is rather limited. Inspired by the structural-functional feature of plant cells, silicon carbide (SiC, cytoderm) coated mesocarbon microbeads (MCMB, cytoplasm) powders were prepared by combustion synthesis (CS), which were then densified via spark plasma sintering (SPS) to obtain the biomimetic cellular-structured SiC-reinforced MCMB (M@SiC) composites. The in-situ formed SiC ‘cytoderm’ ensures good interfacial bonding and contributed to the densification of the composites. Additionally, the continuous SiC skeleton and cellular-structured configuration improved the mechanical properties of M@SiC composites. Owing to the complex crack deflection, branching and bridging effects at the MCMB/SiC interfaces and graphite nanoflakes inside MCMB, the biomimetic M@SiC composite with SiC content of 47 vol% exhibited strengthening and toughening, with flexural strength and fracture toughness of 245 MPa and 3.82 MPa m1/2, respectively. The developed biomimetic graphite-matrix composites with excellent mechanical properties are expected to be applied in reusable spacecrafts and high-temperature gas-cooled reactors.

A finite element analysis method for random fiber-aggregate 3D mesoscale concrete based on the crack bridging law

Mesoscale modeling is an emerging analytical method that can be used to study fiber-reinforced concrete. However, fine fibers with micrometer diameters are distributed in millions in a standard specimen, so it is impossible to establish a mesoscale model and further analyze it, which severely limits the investigation of the reinforcement mechanism of fine fibers on concrete. This paper efficiently established a highly applicable mesoscale analytical model for random fiber-polyhedral aggregate concrete in Abaqus software based on a comprehensive examination of the crack bridging law and the supplementation of the fiber spacing theory, combined with the improvement of the algorithms of aggregate generation, fiber arrangement, and the judgment of the fiber-aggregate contact by the secondary development method of Python, as well as the matrix-dual arrangement method. Additionally, basalt fiber concrete and mortar specimens were prepared and tested, and the parameters of the model were calibrated to verify the model's authenticity. The result shows that the method proposed in this paper can accurately and efficiently perform mesoscale concrete analysis with fine fibers. In the peak load stage, the fiber has the strongest alleviation effect (Δ = 0.033) on the matrix damage, 10 times that of the crack initiation stage (Δ = 0.003). With the development of damage, fiber stress increases gradually from the crack initiation stage (0.68 σfu), and the growth rate (41.53 %) is the largest at the peak load stage (σfu), which reveals the complex dynamic bridging effect of fiber on the matrix. This investigation proposes a novel and broad applicability methodology for the finite element analysis of fiber-reinforced aggregate mesoscale concrete.

Effect of Damping on the Identification of Bridge Properties Using Vehicle Scanning Methods.

Vehicle scanning methods are gaining popularity because of their ability to identify modal properties of several bridges with only one instrumentation setup, and several methods have been proposed in the last decade. In the numerical models used to develop and validate such methods, bridge damping is often overlooked, and its impact on the efficacy of vehicle scanning methods remains unknown. The present article addresses this knowledge gap by systematically investigating the effects of bridge damping on the efficacy of vehicle scanning methods in identifying the modal properties of bridges. For this, acceleration responses obtained from a numerical model of a bridge and vehicle are used. Four different scenarios are considered where vehicle damping, presence of road roughness, and traffic on the bridge are varied. Bridge damping is modeled using mass-proportional, stiffness-proportional, and Rayleigh damping models. The impacts of ignoring bridge damping or considering one of these damping models on the modal frequencies and mode shapes identified using the vehicle response are investigated by comparing the results. The outcomes of the numerical analysis show that ignoring bridge damping in vehicle scanning applications can significantly increase the efficacy of these methods. They also show that the identifiability of the bridge frequencies and bridge mode shapes from the vehicle response decreases significantly when bridge damping is considered. Further, the damping model used impacts which bridge modes can be identified because different damping models provide different modal damping ratios for each mode. The results highlight the importance of correctly simulating damping behavior of bridges, which is often ignored, to be able to correctly evaluate the efficacy of vehicle scanning methods, and they provide an important stepping stone for future studies in this field.

Improved Liver Intravital Microscopic Imaging Using a Film-Assisted Stabilization Method.

Intravital microscopy (IVM) is a valuable method for biomedical characterization of dynamic processes, which has been applied to many fields such as neuroscience, oncology, and immunology. During IVM, vibration suppression is a major challenge due to the inevitable respiration and heartbeat from live animals. In this study, taking liver IVM as an example, we have unraveled the vibration inhibition effect of liquid bridges by studying the friction characteristics of a moist surface on the mouse liver. We confirmed the presence of liquid bridges on the liver through fluorescence imaging, which can provide microscale and nondestructive liquid connections between adjacent surfaces. Liquid bridges were constructed to sufficiently stabilize the liver after abdominal dissection by covering it with a polymer film, taking advantage of the high adhesion properties of liquid bridges. We further prototyped a microscope-integrated vibration-damping device with adjustable film tension to simplify the sample preparation procedure, which remarkably decreased the liver vibration. In practical application scenarios, we observed the process of liposome phagocytosis by liver Kupffer cells with significantly improved image and video quality. Collectively, our method not only provided a feasible solution to vibration suppression in the field of IVM, but also has the potential to be applied to vibration damping of precision instruments or other fields that require nondestructive ″soft″ vibration damping.

Pencil drawn meter bridge

Abstract This study investigates the application of a Wheatstone bridge, specifically through the utilization of a meter bridge constructed on chart paper using pencil graphite. Employing the Wheatstone bridge principle, this study aims to achieve precise measurements of an unknown resistance. Results indicate an error margin between measured and calculated values of less than 10%, highlighting the efficiency and accuracy of this approach. The demonstrated effectiveness of the meter bridge serves as an educational resource, particularly beneficial for K-12 students, providing practical understanding and hands-on experience with the meter bridge concept. This research contributes to enhancing STEAM education by offering a tangible and accessible tool for teaching electrical circuit principles.

TiO2-loaded phosphogypsum-modified biochar for the removal of ofloxacin and Cu2+: Performance, mechanisms, and toxicity assessment

The combined contamination of antibiotics and heavy metals usually occurs in aquaculture wastewater and has high ecological toxicity. Currently, most research only focuses on the removal of a single heavy metal or antibiotics, and there is little research on the simultaneous removal of both. Therefore, to effectively treat them, this study prepared TiO2-loaded phosphogypsum-modified biochar (TYBC450) for adsorption and photocatalytic removal of ofloxacin (OFL) and copper (Cu2+). The removal performance and mechanisms of OFL and Cu2+ were explored, and their ecological toxicity was assessed through zebrafish acute toxicity experiments. The results suggested a synergistic effect between OFL and Cu2+. The adsorption efficiencies of TYBC450 for OFL and Cu2+ were 88.16% and 90.87% (the adsorption capacities were 1.75 and 3.65 mg/g, respectively). Bridging, precipitation, and complexation effects were the main co-adsorption mechanisms. The photocatalytic efficiencies of OFL and Cu2+ were 91.23% and 72.09% (the rate constants were 0.0101 and 0.0045 min-1, respectively). OFL acted as a hole-trapping agent, while Cu2+ acted as an electron acceptor, hindering the combination of e- and h+. There were 12 intermediates in the OFL degradation process, which had lower toxicity than the mother organism. Both the cyclic regeneration and actual aquaculture wastewater application tests indicated that TYBC450 had potential application prospects.

Molecular modeling to elucidate the dynamic interaction process and aggregation mechanism between natural organic matters and nanoplastics

The interactions of nanoplastics (NPs) with natural organic materials (NOMs) dominate the environmental fate of both substances and the organic carbon cycle. Their binding and aggregation mechanisms at the molecular level remain elusive due to the high structural complexity of NOMs and aged NPs. Molecular modeling was used to understand the detailed dynamic interaction mechanism between NOMs and NPs. Advanced humic acid models were used, and three types of NPs, i.e., polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS), were investigated. Molecular dynamics (MD) simulations revealed the geometrical change of the spontaneous formation of NOMs-NPs supramolecular assemblies. The results showed that pristine NPs initially tend to aggregate homogeneously due to their hydrophobic nature, and then NOM fragments are bound to the formed NP aggregates mainly by vdW interaction. Homo- and hetero-aggregation between NOMs and aged NPs occur simultaneously through various mechanisms, including intermolecular forces and Ca2+ bridging effect, eventually resulting in a mixture of supramolecular structures. Density functional theory calculations were employed to characterize the surface properties and reactivity of the NP monomers. The molecular polarity indices for unaged PE, PS, and PVC were 3.1, 8.5, and 22.2 ​kcal/mol, respectively, which increased to 43.2, 51.6, and 42.2 ​kcal/mol for aged NPs, respectively, indicating the increase in polarity after aging. The vdW and electrostatic potentials of NP monomers were visualized. These results clarified the fundamental aggregation processes, and mechanisms between NPs and NOMs, providing a complete molecular picture of the interactions of nanoparticles in the natural aquatic environment.