Yong Cai

Atomic-scale regulation of photogenerated electrons remains a central challenge in reductive photocatalysis because highly reductive electrons are intrinsically prone to rapid recombination and spatial delocalization. Although crystal-facet engineering and defect modulation have independently improved photocatalytic performance, their synergistic coupling in governing electron accumulation and carrier kinetics remains poorly understood. Here, we report a facet-defect coupling strategy that enables spatially confined electron accumulation in ZnIn ₂ S ₄ through preferential exposure of high-index {102} facets. Density functional theory calculations reveal that the {102} facets simultaneously have a more negative conduction band minimum and intrinsically lower sulfur vacancy formation energy than conventional {110} facets, thereby coupling enhanced reduction thermodynamics with spontaneous defect generation. Guided by these predictions, an ethanol-glycerol–mediated solvothermal strategy was developed to stabilize the high-energy {102} facets via surface-energy regulation. Combined crystallographic, spectroscopic, and ultrafast transient absorption analyses demonstrate that the facet-induced sulfur vacancies act as long-lived electron-trapping centers, promoting electron localization, suppressing charge recombination, and prolonging carrier lifetime. As a result, the engineered ZnIn ₂ S ₄ exhibits substantially enhanced catalytic activity across representative multielectron transformations, including H ₂ O ₂ photosynthesis, H ₂ evolution, Cr(VI)/U(VI) reduction, and perfluoroalkyl substance defluorination. This work establishes facet-defect coupling as a general strategy for regulating electron accumulation and carrier behavior to advance reductive photocatalysis at the atomic scale.

Sample preservation is a prerequisite for the authenticity and reliability of analytical data on environmental organic/inorganic pollutants in water samples, as it directly determines the accuracy of subsequent qualitative and quantitative analysis. Despite its widespread use in routine environmental monitoring, the conventional protocol of “bottle sampling and cryopreservation” cannot eliminate the “spatiotemporal discontinuity” between sampling and laboratory pretreatment. Accordingly, this protocol suffers from inherent shortcomings, including analyte adsorption on container walls as well as biotic and abiotic transformations (e.g., microbial degradation and photodegradation) during transportation and storage, all of which introduce nonnegligible analytical biases. On-site solid-phase extraction (SPE) has emerged as a powerful alternative to tackle these challenges in sample pretreatment and preservation, integrating versatile performance, including selective enrichment, phase transfer, speciation stabilization, and matrix removal processes. On-site SPE, therefore, represents a shift from laboratory-based enrichment toward preservation-oriented field sampling and pretreatment of environmental contaminants. This review systematically elaborates the fundamental principles, technical approaches, and latest applications of on-site SPE for organic/inorganic pollutants in environmental water matrices, critically discusses its merits and limitations across diverse field scenarios, and highlights emerging perspectives for further advancing its capabilities in environmental monitoring.

Arsenic (As) and antimony (Sb) are toxic metalloids whose biogeochemical cycles are strongly influenced by carbon (C), nitrogen (N), and sulfur (S) through microbially mediated coupled transformations. However, the mechanistic basis of these coupled processes remains poorly understood. In this Review, we synthesize current advances in the interconnected cycling and elucidate their thermodynamic and ecological foundations. Redox-sensitive As, Sb, C, N, and S species serve as electron donors and acceptors in microbial respiratory chains, and the combination of their redox half-reactions results in the coupled cycles. A redox-ladder framework delineates the theoretical electron flow and thermodynamically feasible coupling combinations. Many combinations have been observed in the environments-for instance, NO3– reduction to N2 coupled with As(III)/Sb(III) oxidation. Their realization also depends on microorganisms harboring key genes (e.g., aioA and arrA). The redox-ladder further predicts novel coupling processes, such as As(III)/Sb(III) oxidation coupled to N2O reduction to N2. We finally emphasize the need for quantitative biogeochemical models within global change scenarios. By integrating bioenergetic principles with microbial ecology, this Review provides a new conceptual framework for uncovering the linkages among elemental cycles, deepening our understanding of the mechanisms and environmental implications of As/Sb biogeochemical cycling coupled with macronutrients.

Coastal estuarine wetlands are vulnerable to river overflows and tidal inputs, yet their roles in mercury (Hg) cycling remain unclear, especially regarding soil Hg distribution, neurotoxic methylmercury (MeHg) production, and plant accumulation. This study investigated the spatial patterns and transfer of total Hg (THg) and MeHg in soils and plants of the Yellow River Estuary wetland (YREW). Soil THg (14.6 ± 6.09 ng/g) decreased from the river bank and coast toward wetland interiors, consistent with the weakening influence of Yellow River discharge and Bohai Sea tidal inputs. Soil MeHg (0.0837 ± 0.0521 ng/g) showed a broadly similar spatial pattern but was likely influenced by external inputs and in situ Hg methylation. Tidal-influenced soils exhibited higher MeHg/THg ratios (0.715–0.944%, commonly representing Hg methylation) compared to river-dominated soils (0.389–0.397%), probably suggesting relatively greater MeHg production and/or accumulation under stronger tidal influence. Moreover, plant THg and MeHg accumulation varied among species and broadly corresponded to soil Hg patterns, suggesting that river–sea interactions may influence plant Hg accumulation through soil-derived uptake and species-specific transfer. Suaeda salsa exhibited higher bioconcentration and transfer factors than Spartina alterniflora and Phragmites australis, indicating stronger Hg accumulation and root-to-aboveground translocation.

Aqueous interfaces, such as those formed at the surface of microdroplets, can spontaneously generate reactive species, driving the critical redox reactions. This raises a pivotal question: could such laboratory-observed interfacial phenomena be integrated into our broader understanding of pollutant transformation and transport dynamics? In this perspective, we discuss this issue in the context of climate warming and changes in hydrological processes, focusing on how these environmental changes may alter the occurrence, composition, and reaction conditions of aqueous interfaces. Notably, aqueous interfaces may represent a previously underrecognized factor influencing the fate and transport of global pollutants, such as mercury. Bridging laboratory findings with field observations will be essential for linking microscale interfacial chemistry to macroscale environmental outcomes, ultimately improving predictive models of global pollutant cycling in a warming world.

The air-water interface of aqueous microdroplets enables the spontaneous generation of hydroxyl radicals (·OH). However, the environmental fate and effect of these primary oxidants in complex, ion-rich media such as seawater remains uncharted. Here, we discover that the interface of seawater microdroplets sustains a radical cascade, which markedly amplifies their oxidative power beyond that of pure water microdroplets. Spontaneously produced ·OH at the interface quickly engages in synergistic reactions with abundant bromide and bicarbonate ions, initiating a network of secondary radicals, including reactive bromine (·Br) and carbonate (·CO₃^-) species. The coexistence and interconversion within this self-sustaining interfacial cycle are demonstrated through radical trapping and spectroscopic methods. To assess the environmental implications of this process, we have quantified its role in the dark oxidation of gaseous elemental mercury. Our findings advance the understanding from mere interfacial oxidant generation to the radical networks by specific ions, offering a novel framework for predicting chemical reactivity in environmental aqueous microdroplets.