Effect of pH of Ganoderma lucidum aqueous extract on green synthesis of silver nanoparticles

Perspective applications of Ag nanoparticles (NPs) stimulate intense research on their affordable synthesis, including green routes. The use of fungi extracts has advantages over other organisms, because of their relatively easy isolation and higher efficiency in a reduction of metal ions and NP formation. Here we report mycosynthesis of AgNPs based on Ganoderma lucidum fruit body extract with different pH values as the bioreducing and stabilising agent. Stable NPs colloids with distinct plasmonic resonance peaking at 408–418 nm are obtained by using photoreduction in a broad pH range (5 to 11). Synthesis efficiency drops only at very acidic conditions, pH = 2.5. The NP size and morphology are studied by dynamic light scattering and scanning electron microscopy. An analysis of FTIR spectra of pure analyte and NP sample indicates that stabilisation of the AgNPs by the components of Ganoderma lucidum extract may take place via forming chemical bonds with the NP surface. These bio-friendly AgNPs are both optically and chemically active, as inferred from surface-enhanced Raman scattering of a standard dye analytes and charge transfer-induced quenching of the photoluminescence of both dye and inorganic NPs, and can be studied for various applications which require direct access to the AgNP surface.