A green synthetic route for the production of silver nanoparticles (AgNPs) using five different aqueous plant extracts, namely, Berberis vulgaris, Brassica nigra, Capsella bursa-pastoris, Lavandula angustifolia and Origanum vulgare, was investigated in this study. The present work demonstrates the influence of plant extract composition (antioxidant and total phenolic content) on the size and morphology of the produced AgNPs. The biosynthetic procedure was rapid and simple and was easily monitored via colour changes and ultraviolet and visible (UV-Vis) spectroscopy. Subsequently, measurement of zeta potential (ZP), photon cross-correlation spectroscopy (PCCS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) analysis were employed to characterise the as-synthesised nanoparticles. The XRD investigation confirmed the presence of Ag⁰ in the nanoparticles, and interactions between the bioactive compounds of the plants and the produced AgNPs were evident in the FTIR spectra. TEM indicated that the nanoparticles exhibited a bimodal size distribution, with the smaller particles being spherical and the larger having a truncated octahedron shape. In addition, the antimicrobial activity of the AgNPs was tested against five bacterial strains. All synthesised nanoparticles exhibited enhanced antimicrobial activity at a precursor concentration of 5 mM compared to the control substance, gentamicin sulphate, with the best results observed for AgNPs prepared with B. nigra and L. angustifolia extracts.

Low-temperature hydrothermal epitaxial growth and topochemical conversion (TC) reactions offer unexploited possibilities for the morphological engineering of heterostructural and non-equilibrium shape (photo)catalyst particles. The hydrothermal epitaxial growth of SrTiO₃ on Bi₄Ti₃O₁₂ platelets is studied as a new route for the formation of novel nanoheterostructural SrTiO₃/Bi₄Ti₃O₁₂ platelets at an intermediate stage or (100)-oriented mesocrystalline SrTiO₃ nanoplatelets at the completed stage of the TC reaction. The Bi₄Ti₃O₁₂ platelets act as a source of Ti(OH)₆^2– species and, at the same time, as a substrate for the epitaxial growth of SrTiO₃. The dissolution of the Bi₄Ti₃O₁₂ platelets proceeds faster from the lateral direction, whereas the epitaxial growth of SrTiO₃ occurs on both bismuth-oxide-terminated basal surface planes of the Bi₄Ti₃O₁₂ platelets. In the progress of the TC reaction, the Bi₄Ti₃O₁₂ platelet is replaced from the lateral ends toward the interior by SrTiO₃, while Bi₄Ti₃O₁₂ is preserved in the core of the heterostructural platelet. Without any support from noble-metal doping or cocatalysts, the SrTiO₃/Bi₄Ti₃O₁₂ platelets show stable and 15 times higher photocatalytic H₂ production (1265 μmol·g^–1·h^–1; solar-to-hydrogen (STH) efficiency = 0.19%) than commercial SrTiO₃ nanopowders (81 μmol·g^–1·h^–1; STH = 0.012%) in pH-neutral water/methanol solutions. A plausible Z scheme is proposed to describe the charge-transfer mechanism during the photocatalysis.