Bovine serum albumins (BSA) induced aggregation and separation of gold colloid nanoparticles.

Plasmonic absorption spectrometry has been applied to study the bovine serum albumins (BSA) induced aggregation and separation of gold colloid nanoparticles. When the concentration of the BSA is relative low in the gold colloid, the binding molecules only lead to the dispersive gold nanoparticles aggregate. The formation of the gold nanochain leads to the absorption peak red shift rapidly, and the corresponding limit of the detection can reach to 20 ng/mL. As the concentration of the BSA is too great, the increasing thickness of the coated BSA layer results in the separation of the gold nanochain and then leads to the blue shift of the plasmonic absorption. The physical mechanism based on quasi-static approximation and coupled dipole method has been investigated to illuminate the aggregation dependent plasmonic shifting of bio-coated gold colloids. Gold nanoparticles with larger size and coated by a thin dielectric layer present better potential for biosensing based on the plasmonic response of binding molecules induced aggregation.