Fig. 1
Physical characterization of silver nanoparticles (AgNPs) synthesized with Bacillus amyloliquefaciens strain A3. Cell-free culture supernatant (CFCS) was obtained from the culture of strain A3 grown in a nutrient broth for 48 h. AgNP–CFCS is AgNPs produced in the CFCS with 3 mM AgNO3 for 24 h. AgNP-culture is AgNPs produced in the 48-h culture with 3 mM AgNO3 for 24 h. a, b UV–visible spectra of AgNPs. c, d Transmission electron micrographs show spherical and nearly spherical AgNPs. e, f Histograms of the diameter distribution of the AgNP–CFCS and AgNP-culture in the micrographs. g, h X-ray diffraction spectra show the nanoscale size and crystalline nature of AgNPs. The five diffraction peaks (101), (111), (200), (220) and (311) at the respective 2θ degree 32.20° and 32.21°, 37.99° and 38.07°, 46.20° and 46.13°, 67.49° and 67.46°, and 77.14° and 76.71° correspond to the lattice plane values of the face-centered cubic silver. The unassigned peaks (asterisks) at 2θ degree 27.79° and 27.80°, 54.89° and 54.78°, 57.25° and 57.30° may correspond to the biomolecules coating the AgNPs