In this work, we successfully synthesized Cr 3+ doped ZnO nanoparticles using a sol-gel method, and elucidated how Cr 3+ dopant is critical for enhancing photocatalytic activity. The nature of the point defect analyzed by electron spin resonance (ESR), and photoluminescence (PL) emission revealed the role of the Cr 3+ dopant. When introducing Cr 3+ ions in ZnO, the PL emission intensity decreased, indicating a reduction of the radiative recombination rate due to the heterojunction formation between the dopant and the host. The Cr 3+ doped ZnO nanostructures showed that the typical ESR signal with g-factor value ∼1.96 was completely passivated, indicating the diffusion of electrons near the conduction band into the dopant ions. The doped Cr 3+ ion acts as an electron trap in the ZnO crystal described as3 2The mechanism for enhancing the photocatalytic activity of heterogeneous ZnO:Cr 3+ was proposed in respect of point defect evolution through the manner of Cr 3+ doping. As a result, the photocatalytic efficiency investigated by measuring methylene blue degradation under 210 min of direct sunlight irradiation reached 93.5% for 1 at % Cr 3+ doped ZnO, which was significantly improved compared to 59.8% of the pure ZnO.
Anthracnose disease caused by Colletotrichum spp. makes heavy losses for post-harvest mangoes of Cat Hoa Loc variety during storage, packaging, and transportation. The synthetic fungicides are commonly used to control the disease, but they are not safe for consumers’ health and environment. This study was aimed to investigate the use of essential oils (EOs) as the safe alternative control. Pathogen was isolated from the infected Cat Hoa Loc mangoes and identified by morphology and DNA sequencing of the ITS region. Six EOs (cinnamon, basil, lemongrass, peppermint, coriander, and orange) were chemically analyzed by GC–MS. The antifungal activity of EOs was studied in vitro and in vivo. The results showed that the isolated pathogen was Colletotrichum acutatum. Cinnamon, basil, and lemongrass EOs effectively inhibited the growth of C. acutatum in descending order of cinnamon, basil, and lemongrass. However, they (except basil oil) severely damaged fruit peels. The antifungal activity was closely related to the main compounds of EOs. Basil EOs effectively controlled anthracnose development on Cat Hoa Loc mangoes artificially infected with C. acutatum, and its effectiveness was comparable to that of fungicide treatment. Consequently, basil EOs can be used as a biocide to control anthracnose on post-harvest Cat Hoa Loc mangoes.
Lichens are a promising source of good anticancer agents. However the study on their bioactivities remains limited, especially in Vietnam. In this study, three extracts of lichen Usnea undulata Stirt. including n‐hexane, acetone and methanol were investigated for their cytotoxic activity on two human cancer cell lines (MCF‐7, NCI‐H460) and normal fibroblasts by sulforhodamine B (SRB) assay. The results showed that the n‐hexane extract exhibited the highest inhibition activity with IC50 5.26±0.13 μg/mL for MCF‐7 and 6.83±0.64 μg/mL for NCI‐H460, followed by acetone extract with IC50 66.44±1.37 μg/mL and 92.14±1.49 μg/mL, respectively. The methanol extract possessed weak cytotoxic effect against MCF‐7 and NCI‐H460 (IC50 values more than 100 μg/mL). The n‐hexane extract demonstrated interesting activity particularly on MCF‐7 as good selectivity index was recorded (SI > 3). The phytochemical study on n‐hexane and acetone extracts led to the isolation of four compounds including usnic acid (1), methyl orsellinate (2), methyl β‐orsellinate (3), 7‐hydroxyl‐5‐methoxy‐6‐methylphtalide (4) in which compound (4) was isolated the first time in such species. Their structures were elucidated by NMR analysis and compared with literature data.
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