One-pot strategy for biomimetic synthesis of zein-conjugated silver sulphide nanospheres in ethanol solution

Water-soluble Ag₂S nanospheres embedded in a zein matrix were successfully synthesised by a simple, controllable protein-assisted method in ethanol solutions. The morphology and size of products were tunable through controlling the concentration of zein. X-ray diffraction and energy-dispersive X-ray spectrum results showed that the obtained samples were a pure monoclinic phase of Ag₂S. The Ag₂S nanoparticles were homogeneously surrounded by protein molecules observed from a high-resolution transmission microscopy image. There was strong chemical interaction between the Ag₂S nanocrystals and the functional groups of zein molecules, which has been confirmed by Fourier transform infrared and thermogravimetry analysis measurements. The band gap of zein-conjugated Ag₂S nanocrystals showed obvious blue shift in ultraviolet-visible spectra compared with bulk materials because of the quantum size effect.