I could not find any about 200nm size. I wanna know what colour is it? why almost all researcher have studied almost 1-110 nm.? predition of colour is different in larger nanoparticles,(maybe since scattering become larger than absorption in large sizes) how?
Silver show surface plasmone resonance (SPR) from 420 to 450nm. Increase in wave length will indicate increase in size and irregularities in shape. Smaller size and spherical shape nanoparticles will give SPR in range of 420 to 430nm.