RESUMO
In this article, the supernatant of the soil-borne pathogen Bacillus mn14 was used as the catalyst for the synthesis of AgNPs. The antibacterial and antifungal activity of Bs-AgNPs was evaluated, in which S. viridans and R. solani showed susceptibility at 70 µL and 100 µL concentrations. Enzyme properties of the isolates, according to minimal inhibitory action and a growth-enhancing hormone-indole acetic acid (IAA) study of the isolates, were expressed in TLC as a purple color with an Rf value of 0.7. UV/Vis spectroscopy revealed the presence of small-sized AgNPs, with a surface plasmon resonance (SPR) peak at 450 nm. The particle size analyzer identified the average diameter of the particles as 40.2 nm. The X-ray diffraction study confirmed the crystalline nature and face-centered cubic type of the silver nanoparticle. Scanning electron microscopy characterized the globular, small, round shape of the silver nanoparticle. AFM revealed the two-dimensional topology of the silver nanoparticle with a characteristic size ranging around 50 nm. Confocal microscopy showed the cell-wall disruption of S. viridans treated with Bs-AgNPs. High-content screening and compound microscopy revealed the destruction of mycelia of R. solani after exposure to Bs-AgNPs. Furthermore, the Bs-AgNPs cured sheath blight disease by reducing lesion length and enhancing root and shoot length in Oryza sativa seeds. This soil-borne pathogen Bacillus-mediated synthesis approach of AgNPs appears to be cost-efficient, ecofriendly, and farmer-friendly, representing an easy way of providing valuable nutritious edibles in the future.
RESUMO
Nanosized mesoporous CuMgAl ternary oxide catalysts were prepared by thermal decomposition of CuMgAl-layered double hydroxides at 500 °C with nominal Cu/Mg/Al ratios of 1:1:1 (Cu-LDH-I), 1.5:0.5:1 (Cu-LDH-II), and 2:0:1 (Cu-LDH-III). The synthesized catalysts were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, CO2-TPD, and N2 physisorption analysis techniques. The catalytic activity of the synthesized materials was investigated for the Henry reaction between nitromethane and numerous aldehyde derivatives under ultrasonic irradiation. The three CuMgAl ternary oxide catalysts exhibited a high catalytic activity, forming nitro alcohol products with 100% atom economy. The CuMgAl-I catalyst derived from Cu-LDH-I offered high turnover frequencies (TOFs in the synthesis of all of the nitro alcohols in shorter reaction times). The superior catalytic activity of the CuMgAl-I sample is attributed to the synergistic effect between the physicochemical properties of the catalysts and ultrasonic irradiation. The HRTEM analysis of the used CuMgAl-I catalyst revealed the evidence for the cavitation collapse, which causes localized deformation and surface erosion. Moreover, the synthesized catalysts also exhibited robust sustainable activity that resisted deactivation over repeated usage. The present example of ultrasonic-assisted catalyzed organic synthesis represents a novel strategy for the solvent-free green synthesis of nitro-alcohols by the Henry reaction with 100% atom economy.
RESUMO
Two advances in the development of a one-pot method to prepare silver nanoparticles (AgNPs) using the Tollens' reagent are described. First, a template-directed process of AgNP synthesis using resorcinol triazole ligands bearing two pendent galactose sugars is shown. Second, the conversion of these AgNPs into SERS nanotags is demonstrated using malachite green isothiocyanate as the Raman reporter molecule.