title: Dense aqueous colloidal gold nanoparticles prepared from highly concentrated precursor solution.
abstract: Gold nanoparticles were fabricated by reduction of highly concentrated Au(III) ions (200 mM) with casein proteins from milk. The gold nanoparticles were converted to nanoparticle-powders after washing and subsequent vacuum drying without aggregation. The nanoparticle-powders completely re-dispersed in aqueous solution, and stable colloidal gold nanoparticles were obtained. UV-vis extinction spectra and dynamic light scattering (DLS) measurements revealed that large assemblies (size, ca. 3 μm) and subaggregates (size, <0.5 μm) composed of gold nanoparticle-casein protein chain-Au(III) ion were dynamically formed and disintegrated over the course of the growth of the gold nanoparticles. Fourier transform infrared (FT-IR) spectra indicated conformational changes of casein proteins induced by the interaction of casein protein-Au(III) ion and -gold nanoparticle. Finally, rapid, one-pot, and highly concentrated synthetic procedures of gold and silver nanoparticle powders protected by casein (mean diameters below 10 nm) were successfully developed using 3-amino-1-propanol aqueous solutions as reaction media. Dense colloidal gold (40 g L(-1)) and silver (22 g L(-1)) nanoparticle aqueous solutions were obtained by re-dispersing the metal nanoparticle powders.
authors.affiliation: Department of Applied Chemistry, Kinki University, 3-4-1 Kowakae, Higashi-osaka, Osaka 577-8502, Japan. soejima@apch.kindai.ac.jp
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Soejima
authors.forename: Seisaku
authors.initials: S
authors.lastname: Oshiro
authors.forename: Yasuji
authors.initials: Y
authors.lastname: Nakatsuji
authors.forename: Seishiro
authors.initials: S
authors.lastname: Ito