Synthesis of silver nanoparticles using Bacillus velezensis M3-7 lipopeptides: Enhanced antifungal activity and potential use as a biocontrol agent against Fusarium crown rot disease of wheat seedlings

Bacillus velezensis M3-7 is a hyperactive mutant, 12-fold improved in its antifungal activity, obtained during a previous study from the wild strain BLB371 after a combination of random mutagenesis and medium component optimization. This study explores the use of this mutant in synthesizing silver nanoparticles (Ag-NPs) for the control of Fusarium crown rot disease (FCR) in wheat seedlings. LC-MS/MS analysis proved that both strains co-produced different families of lipopeptides and that mutagenesis caused the hyper-production of iturin A C14 and C15, the liberation of iturin A C10 and C12, and the inhibition of fengycin release. Our aim was a further improvement in the antifungal activity of the wild strain and the mutant M3-7 in order to control Fusarium crown rot disease (FCR) in wheat seedlings. Therefore, a nanotechnology approach was adopted, and different lipopeptide concentrations produced by the wild strain and the mutant M3-7 were used as capping agents to synthesize silver nanoparticles (Ag-NPs) with enhanced antifungal activity. Ag-NPs formed using 3 mg·mL−1 of the mutant lipopeptides were found to exhibit a good distribution, improved antifungal activity, a promising potential to be used as a biofortified agent for seed germination, and an effective compound to control FCR in wheat seedlings.This work was supported by grants from the Tunisian Ministry of Higher Education and Scientific Research. This research was supported in part by the Centre for Sustainable Development, Qatar University. TEM analysis was accomplished in the Central Laboratories unit, Qatar University. Open Access funding provided by the Qatar National Library

The effect of graphene on the activation energy of grain growth for the nanocrystalline thermoelectric n-type Bi2Te2.7Se0.3

Even though bismuth telluride is frequently produced by mechanical alloying for thermoelectric materials, no data has been published addressing the thermal behavior and activation energy of the milled n-type Bi2Te2.7Se0.3 powders. This paper studies the activation energy of grain growth for the nanocrystalline n-type Bi2Te2.7Se0.3 and two graphene-Bi2Te2.7Se0.3 composites with different graphene concentrations (0.05 and 0.5 wt.%). Grain size and structural analyses of these samples have been carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal stability of the three samples is investigated by incorporating differential scanning calorimetry data with the Kissinger model. The activation energy of the pristine Bi2Te2.7Se0.3 alloy is found to be 268 kJ/mol. For the composite samples, a lower graphene weight percentage (0.05 wt.%) increased the activation energy to 270 kJ/mol. In contrast, higher amounts of graphene (0.5 wt.%) reduced the activation energy significantly to 254 kJ/mol. The observed effect is found to be directly related to graphene’s exfoliation in the bismuth telluride matrix. These results offer a better understanding of the thermal behavior of the nanocrystalline pristine n-type Bi2Te2.7Se0.3 and the influence of graphene nanofiller on the thermal stability of the bismuth telluride nanocomposites.Other Information Published in: Emergent Materials License: https://creativecommons.org/licenses/by/4.0See article on publisher's website: http://dx.doi.org/10.1007/s42247-022-00416-5</p