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Tantalum-doped ZnO structures (ZnO:Ta) were synthesized, and some of their characteristics were studied. ZnO material was deposited on silicon substrates by using a hot filament chemical vapor deposition (HFCVD) reactor. The raw materials were a pellet made of a mixture of ZnO and Ta2O5 powders, and molecular hydrogen was used as a reactant gas. The percentage of tantalum varied from 0 to 500 mg by varying the percentages of tantalum oxide in the mixture of the pellet source, by holding a fixed amount of 500 mg of ZnO in all experiments. X-ray diffractograms confirmed the presence of zinc oxide in the wurtzite phase, and metallic zinc with a hexagonal structure, and no other phase was detected. Displacements to lower angles of reflection peaks, compared with those from samples without doping, were interpreted as the inclusion of the Ta atoms in the matrix of the ZnO. This fact was confirmed by energy dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD) measurements. From scanning electron microscopy (SEM) images from undoped samples, mostly micro-sized semi-spherical structures were seen, while doped samples displayed a trend to grow as nanocrystalline rods. The presence of tantalum during the synthesis affected the growth direction. Green photoluminescence was observed by the naked eye when Ta-doped samples were illuminated by ultraviolet radiation and confirmed by photoluminescence (PL) spectra. The PL intensity on the Ta-doped ZnO increased from those undoped samples up to eight times.

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Dyssodia decipiens is one of the seven recognized species within the Dyssodia genus, which has economic and social relevance in Mexico. Herein, we report on the volatile characterization and pharmacological activity of D. decipiens. The essential oils (2017-2019) contained verbenone (30.8-60.9 %), limonene (5.6-35.5 %), βcaryophyllene (7.8-19.8 %) and linalool (4.5-12.4 %) as major constituents along the studied years. Antifungal properties were probed on Candida albicans ATCC 90028, ATCC 10231 (fluconazole resistant) and five clinical isolates (IS1-IS5). Flower essential oils had the best anti-C. albicans activity (MIC 59.2-93.5 μg mL À 1), and limonene (MIC 125.5-188.4 μg mL À 1) and β-caryophyllene (MIC 104.3-184.2 μg mL À 1) were involved in this effect. SEM examination revealed that D. decipiens essential oils produced an evident lysis on the fungus. Mosquito repellent activity was demonstrated on Aedes aegypti, a vector of dengue, chikungunya and zika viruses. The repellent activity of leaf essential oils (20 %) was effective within 1-5 h post-treatment (> 90 %) and it was stronger (p < 0.01) than that of commercial DEET. The evaluation of the four major volatiles (10 % each) produced similar results to those of essential oils. Finally, leaf essential oils showed a moderate antiproliferative activity on the lines OVCAR-3 (LD 50 56.5-85.7 μg mL À 1), and verbenone (LD 50 65.3 μg mL À 1) and β-caryophyllene (LD 50 43.6 μg mL À 1) were linked to this effect.

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