The application of C/S particles as nanotags in immunoassays or immunoSERS applications depends on their SERS activity. At the single-particle level, the structure of the particles, besides their material and size, determines their SERS intensities. In the case of Au/Au core/satellite particles, singleparticle brightness is achieved. At the ensemble level, the SERS brightness of synthesized C/S colloids, which contains a mixture of C/S particles and monomeric AuNP, also depends on the amount of unbound and SERS-inactive satellite particles contaminating the colloid.