Casein mediated synthesis of stabilized metal/metal-oxide nanoparticles with varied surface morphology through pH alteration

Most of the green and biological synthesis of nanoparticles reported is through plants or micro-organisms. A new green, bio-based synthetic method was developed to synthesize metal/metal-oxide nanoparticles with the difference in morphology through a simple one-step method using milk protein casein through pH alteration. Basic pH will lead casein to dissociate the micellar structure and expose its functional groups. This helps the reduction of precursors to form nanoparticles. Further reduction of pH to neutral (6–7) enhances the reformation of micelle with entrapped nanoparticles in it. Casein micelles could synthesize highly fluorescent nanoparticles. We have synthesized Ag, Au, and CuO nanoparticles with the difference in morphology through the same method. These nanoparticles were characterized with UV–visible spectroscopy and XRD to confirm nanoparticle formation. DLS and zeta potential values were taken to know the hydrodynamic diameter and stability of nanoparticles respectively.TEM results revealed the difference in the morphology of Ag, Au, and CuO nanoparticles synthesized through the same route. Photo luminescent spectroscopy studies exhibited the fluorescent nature of the Ag, Au, and CuO nanoparticles. Nanoparticles are found to be stabilized by casein micelles. FTIR spectrum confirmed the production of casein stabilized Ag, Au, and CuO nanoparticles. This is the first synthesis method for the synthesis of different nanoparticles with varied morphology through a single method by changing the precursors only.