Preparation and optical properties of silver nanoparticles in R-phycoerythrin,a protein matrix

Ag⁺ chemisorption by R-phycoerythrin in an aqueous solution is shown to lead to the formation of silver nanoparticles, without the need for a reductant of Ag⁺. According to electron-microscopic results, most of the nanoparticles are elongated, (3 ± 0.5) × (6 ± 2) nm in dimensions. Also present are cubic Ag crystallites 22.5 nm in size (standard deviation of ±5.9 nm) and aggregates 53 × 48 nm in dimensions (standard deviation of ±8.8 × 8 nm). The absorption spectrum of the Ag nanoparticles in R-phycoerythrin is typical of small nanoparticles. Their fluorescence spectrum shows peaks of individual nanoparticles (450 nm) and fractal aggregates (630 and 670 nm). The fluorescence intensity of the Ag nanoparticles and their aggregates is an order of magnitude higher in comparison with other matrices.