Tree peony (Paeonia suffruticosa Andr.) is a popular cut flower among ornamental plants. However, its short vase life severely hinders the production and application of cut tree peony flowers. To extend the postharvest longevity and improve the horticultural value, silver nanoparticles (Ag-NPs) was applied for reducing bacterial proliferation and xylem blockage in cut tree peony flowers in vitro and in vivo. Ag-NPs was synthesized with the leaf extract of Eucommia ulmoides and characterized. The Ag-NPs aqueous solution showed inhibitory activity against bacterial populations isolated from stem ends of cut tree peony ‘Luoyang Hong’ in vitro. The minimum inhibitory concentration (MIC) was 10 mg L⁻¹. Compared with the control, pretreatments with Ag-NPs aqueous solution at 5 and 10 mg L⁻¹ for 24 h increased flower diameter, relative fresh weight (RFW), and water balance of tree peony ‘Luoyang Hong’ flowers. Additionally, malondialdehyde (MDA) and H₂O₂ content in pretreated petals were lower than the control during the vase life. The activities of superoxide dismutase (SOD) and catalase (CAT) in pretreated petals were lower than that of the control at the early vase stage and higher at the late vase life. Furthermore, pretreatments with Ag-NPs aqueous solution at 10 mg L⁻¹ for 24 h could reduce bacterial proliferation in the xylem vessels on the stem ends by confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM). Overall, pretreatments with green synthesized Ag-NPs aqueous solution effectively reduced bacteria-induced xylem blockage of cut tree peony, resulting in improved water uptake, extended vase life, and enhanced postharvest quality. Therefore, this technique can be used as a promising postharvest technology in the cut flower industry.

In this paper, a novel S-scheme CuS/Bi₅O₇I heterojunction was successfully constructed using a two-step approach comprising the alkaline hydrothermal method and the adsorption–deposition method, and it consisted of Bi₅O₇I microrods with CuS particles covering the surface. The photocatalytic antibacterial effects on Escherichia coli (E. coli) were systematically examined with visible light exposure. The results suggested that the 3%-CuS/Bi₅O₇I composite showed the optimal antibacterial activity, completely inactivating E. coli (5 × 10⁸ cfu/mL) in 180 min of irradiation. Moreover, the bacterial inactivation process was scientifically described. •O₂⁻ and h⁺ were the major active species for the inactivation of the bacteria. In the early stages, SOD and CAT initiated the protection system to avoid the oxidative destruction of the active species. Unfortunately, the antioxidant protection system was overwhelmed thereafter, which led to the destruction of the cell membrane, as evidenced by the microstructure changes in E. coli cells. Subsequently, the leakage of intracellular components including K⁺, proteins, and DNA resulted in the unavoidable death of E. coli. Due to the construction of the S-scheme heterojunction, the CuS/Bi₅O₇I composite displayed the boosted visible light harvesting, the high-efficiency separation of photogenerated electrons and holes, and a great redox capacity, contributing to an outstanding photocatalytic disinfection performance. This work offers a new opportunity for S-scheme Bi₅O₇I-based heterojunctions with potential application in water disinfection.

The widespread application of nanoparticles (NPs) in agriculture has not only enhanced the efficiency of agrochemical use but also introduced environmental pollution, potentially impacting human health through absorption and accumulation in edible plants. The purpose of this study was to evaluate the toxic effects and ecological risks of Cu₂O nanoparticles (nCu₂O) in the life cycle of soybean, and to provide a theoretical basis for the safe application of NPs in agriculture. Soybeans were grown in natural soil modified with nCu₂O, bulk cuprous oxide (bCu₂O) and copper sulfate (CuSO₄) at concentrations of 0, 50, 200, and 800 mg/kg. Samples and grains from treated soybeans were collected at the flowering, podding, and seed-filling stages for analysis. The results indicated that treatments with nCu₂O, bCu₂O, and Cu²⁺ reduced the chlorophyll content in soybean leaves, thereby affecting photosynthesis. Significant reductions were observed in the net photosynthetic rate (Pn), the transpiration rate (Tr), stomatal conductance (Gs), the quantum yield of photosystem II (Y(II)), photochemical quenching (qP), and the electron transport rate (ETR) at high concentrations. However, the toxicity of nCu₂O to photosynthesis recovers as the plant grows. Almost all treatments increased the levels of antioxidant enzymes (SOD, POD, CAT) and reduced oxidative stress. In the nCu₂O and bCu₂O treatments, grain protein content was significantly reduced, while fat and water content increased. Phosphorus (P) content decreased, whereas sulfur (S), potassium (K), magnesium (Mg) and calcium (Ca) contents increased. The accumulation of copper in plants followed the order nCu₂O > bCu₂O > Cu²⁺, with the bCu₂O treatment being slightly more toxic than the nCu₂O treatment, and both being more toxic than the Cu²⁺ treatment. The above data indicated that nCu₂O had a dose-dependent effect, which significantly inhibited soybean growth and changed grain quality at high concentrations.

Z-scheme Bi₂MoO₆/Bi₅O₇I heterojunction was constructed by an in situ solvothermal method, which was composed of Bi₂MoO₆ nanosheets growing on the surface of Bi₅O₇I microrods. The antibacterial activities under illumination towards Escherichia coli (E. coli) were investigated. The Bi₂MoO₆/Bi₅O₇I composites exhibited more outstanding antibacterial performance than pure Bi₂MoO₆ and Bi₅O₇I, and the E. coli (10⁸ cfu/mL) was completely inactivated by BM/BI-3 under 90 min irradiation. Additionally, the experiment of adding scavengers revealed that h⁺, •O₂⁻ and •OH played an important role in the E. coli inactivation process. The E. coli cell membrane was damaged by the oxidation of h⁺, •O₂⁻ and •OH, and the intracellular components (K⁺, DNA) subsequently released, which ultimately triggered the apoptosis of the E. coli cell. The enhanced antibacterial performance of Bi₂MoO₆/Bi₅O₇I heterojunction is due to the formation of Z-scheme heterojunction with the effective charge transfer via the well-contacted interface of Bi₂MoO₆ and Bi₅O₇I. This study provides useful guidance on how to construct Bi₅O₇I-based heterojunction for water disinfection with abundant solar energy.