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Abstract: Metal–organic frameworks (MOFs) are increasingly deployed in environmental technologies, yet their fate and hazard under realistic multistep exposure scenarios remain poorly constrained. Here, we track hierarchical transformations of nanoscale ZIF-8 (Zeolitic Imidazolate Framework-8) across an exposure cascade spanning atmospheric aging (air and reactive gases O3/NO2), aqueous aging in environmentally and biologically relevant media, and ingestion by the freshwater crustacean Daphnia magna. Synchrotron Zn K-edge X-ray absorption spectroscopy (XAS), micro-X-ray fluorescence (μ-XRF), X-ray photoelectron spectroscopy (XPS), and electron microscopy show that gas-phase exposure produces only minor surface perturbations, whereas aqueous contact drives pronounced medium-dependent restructuring, including nitrogen depletion and oxygen enrichment at the surface and time-resolved dissolved Zn release with chemistry-imposed plateaus. In vivo, Zn speciation diverges from the pristine Zn–N fingerprint; an unexposed endogenous Zn baseline and linear combination fitting (LCF) indicate a mixture of endogenous Zn with transformed Zn pools dominated by O/P/S-type coordination environments. Acute ecotoxicity assay demonstrates strong concentration dependence (48 h immobilization EC50 ≈0.5 μg mL–1), and chronic exposure at 0.10 μg mL–1 reduces cumulative brood production with increased adult mortality over 24 days. Mechanistically, fractionated toxicity assays show that washed aged particles/precipitates and whole aged suspensions are more potent than particle-free filtrates, indicating that particle-associated transformed Zn pools contribute substantially beyond dissolved Zn alone. Together, these results show that ZIF-8 risk emerges from its sequential transformation trajectory rather than its pristine state, motivating tiered aging protocols coupled to in vivo speciation and fractionated hazard testing for MOF safety assessment.

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Abstract: Nanoplastics (NPls) have been recognized as emerging persistent toxic particulates in aquatic environments and their interactions with biota pose growing ecological concerns. Yet, the mechanisms governing their cellular association and resulting toxicity remain poorly resolved because population-level assays obscure the inherent variability among individual cells. Here, we integrate single-cell inductively coupled plasma mass spectrometry (SC-ICP-MS) with Gaussian mixture modelling (GMM) to quantify the dynamic heterogeneous association of Eu-doped polystyrene nanoplastics (Eu-doped NPls) with the model microalga Chlorella vulgaris. The GMM analysis identified distinct subpopulations exhibiting variable particle association that shift dynamically with exposure time and concentration. Across exposures of 5–20 mg L−1, GMM analysis revealed that the majority of microalgal cells (35–65%) belonged to low-association clusters, whereas only a small fraction (0–10%) exhibited high NPls association, with pronounced temporal and concentration-dependent shifts in subpopulation structure. A generalized linear model (GLM) further demonstrated that these high-burden subpopulations disproportionately account for observed growth inhibition, increasing from 12.75% at 5 mg L−1 to 39.34% and 43.05% at 10 and 20 mg L−1, respectively. Synchrotron-based nano X-ray fluorescence (nano-XRF) provided spatial evidence consistent with particle localization within or closely associated with algal cell, while physiological endpoints (chlorophyll-a content, CO2 fixation, ROS, and MDA levels) validated the toxicity trends. This integrative single-cell and unsupervised machine-learning modelling framework provides quantitative evidence that stochastic, heterogeneous interactions underpin NPls toxicity in microalgae. The approach offers a transferable analytical paradigm for elucidating the fate and effects of persistent plastic pollutants in aquatic ecosystems.

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Abstract: Controlling the redox landscape of transition metal oxides is central to advancing their reactivity for heterogeneous catalysis or high-performance gas sensing. Here, we report single Cu atom sites (1.42 wt.%) anchored on Co3O4 nanoparticles (Cu1-Co3O4) that dramatically enhance reactivity and molecular sensing properties of the support at low temperature. The Cu1 are identified by x-ray absorption near edge structure and feature metal–support interaction between the atomically dispersed Cu (mostly in 2+ oxidation state) and Co3O4, as revealed by x-ray photoelectron spectroscopy. The ability of Cu1 to form interfacial Cu–O–Co linkages strongly reduces the temperature of lattice oxygen activation compared to CuO nanoparticles on Co3O4 (CuONP-Co3O4), as demonstrated by temperature-programmed reduction and desorption analyses, in agreement with density functional theory calculations. To demonstrate practical impact, we deploy Cu1-Co3O4 nanoparticles as a chemoresistive sensor for formaldehyde that yields more than an order of magnitude higher response than CuONP-Co3O4 and consistently outperforms state-of-the-art sensors. Formaldehyde is detected down to 5 parts-per-billion at 50% relative humidity and 75°C with excellent selectivity over critical interferents. These results establish a strategy for activating redox-active supports using single-atom isolates of non-noble nature, yielding drastically enhanced and well-defined reactivity to promote low-temperature oxidation reactions and selective analyte sensing.

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Abstract: Carbon monoxide is one of the most hazardous pollutants in automotive gas exhaust emissions due to its severe impact on the human body and environment. There are many methods for CO removal, including adsorption, methanation, and catalytic oxidation. Catalyst oxidation has been considered the most efficient technique for CO removal. Although CO oxidation has received extensive attention in past decades, achieving high activity and stability at both engine working and cold starting temperatures is still challenging. Noble metal catalysts generally exhibit excellent catalytic activity in high-temperature regions. However, it still suffers from several obstacles, such as over-absorption of CO in low-temperature regions for Pt-based catalysts. Therefore, researchers still focus on seeking alternative candidates for noble metals due to their high cost and low availability, promising non-noble metals including manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu) receive increasing attention due to their high catalytic activity and stability. Many forms of catalysts have been studied exclusively, such as metal catalysts, metal oxide catalysts, supported catalysts, zeolite, and carbon-based catalysts. Supported catalysts with available metal surface area and unique metal-support interfacial perimeter play pivotal roles in heterogeneous catalysis across various industrial applications. Depending on the size of supported active metal, supported metal catalysts can be categorized into particle, cluster, and single-atom catalysts. Among these, single-atom catalysts (SACs) with relatively specific active structures offer prominent advantages in optimizing catalytic activity and product selectivity, leading to an increasing interest in this research area. In recent years, the catalytic performance of SACs has been largely improved through some reported methods including adjusting coordination number, doping heterogeneous atoms, modulating support anchoring sites, and so on. Despite these advancements, it has always been ignored that with the change of the catalyst synthetic process as well as the metal-support interaction (MSI), supported active sites may appear at different positions in catalyst supports, especially at surface or subsurface, thus exhibiting distinct different catalytic behaviour with surrounding molecules. However, the isolated metal site-related location effect is very difficult to deeply explore, because the complexity of catalyst synthesis, combined with the absence of a metal atom location descriptor, poses significant obstacles to achieving precise control over the location of active metal. Herein, we first proposed an electronic metal-support-carbon interaction (EMSCI), which provides a complete picture of the mass and electron flow and expands on the traditional electronic metal-support interactions (EMSI) concept. Furthermore, we reported an exception of EMSI where the interaction between support and metal is not necessary to achieve a high catalytic activity in the CO oxidation reaction, especially in low-temperature regions. The reducibility of CeO2 is investigated by Ce L3 and M4,5 edge NEXAFS, it is confirmed that CeO2 cannot be reduced even under the reductive conditions. Moreover, the location-dependent Cu species have been investigated which are formed during the hydrothermal process using both ex situ and in situ X-ray techniques. The CO oxidation activity shows a positive relation to the percentage of Cu(CO)+ species detected during the reaction. Such behaviour resembles the intrinsic catalytic activity of a true Cu(CO)+ single site, in which the support is completely inactive. This unique phenomenon provides a new scope of understanding metal support interaction and a pathway to optimizing single-atom catalyst performance and catalyst design.

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Abstract: 99Tc is a long-lived radioactive fission product whose subsurface mobility is governed by redox conditions. Under oxic conditions, soluble Tc(VII)O4– is mobile, whereas under reducing conditions, poorly soluble Tc(IV) phases limit transport. Microcosm studies have frequently reported TcO2-like solids and, less consistently, Tc(IV)-sulfides. The stability of Tc(IV)-sulfides under environmentally relevant conditions remains unclear. Here, we used flowing sediment columns representative of the Sellafield subsurface to examine Tc speciation and stability over ∼1 year. Under reducing conditions, >90% of added TcO4– (400 μg) was retained under both Fe(III)- and sulfate-reducing conditions. X-ray absorption spectroscopy showed TcO2-like phases dominated in Fe(III)-reducing columns, while Tc(IV)-sulfides dominated after sustained sulfate reduction. Sequential extractions indicated that Tc in sulfidic sediments was more recalcitrant (≤23% released by weak acids) than in Fe(III)-reducing systems (∼60% released). With oxic groundwater pumping, effluent Tc sourced from the sediments rose rapidly. Over 160 days, the sulfidic columns remobilized ∼25% of their Tc inventory compared to ∼50% in Fe(III)-reducing columns. The Tc(IV)-sulfides also gradually oxidized to form TcO2 phases. While Tc(IV)-sulfides may enhance Tc retention under reducing conditions, TcO2 phases more likely govern 99Tc mobility during long-term redox cycling. Our findings provide new constraints for modeling Tc fate at contaminated sites and in radioactive waste disposal.