Decreased resonance light scattering of citrate-stabilized gold nanoparticles by chemisorption of mercaptoacetic acid

Citrate-capped gold nanoparticles with different colours and diameters were prepared by the reduction of HAuCl4 using sodium citrate. With increasing the size of gold particles, the plasmon absorption peaks were shifted to longer wavelength and the intensity of resonance light scattering was enhanced. The resonance light scattering of gold nanoparticles in the range of 500–600 nm was quenched by chemisorption of mercaptoacetic acid. Using dielectric coated gold nanosphere model, the probable mechanism of decreasing resonance light scattering was obtained by numerical calculation based on quasi-static theory. The calculation results showed that with the decreasing dielectric constant of nanoshells, the light scattering intensity at 557 nm reduced linearly. The explanation of decreasing resonance light scattering in this paper provided a theoretical foundation for developing highly selective assays using quenched resonance light scattering.