Comparison of different strategies for the assembly of gold colloids onto Fe3O4@SiO2 nanocomposite particles

Three strategies were employed for the assembly of gold nanoparticles on silica-coated magnetite particles (SCMPs). In strategy I, citrate-coated gold nanoparticles were attached on the surface of amine-SCMPs. In strategy II, amine-SCMPs were coated with carboxylated gold nanoparticles via amide bond formation. In strategy III, the thiol-SCMPs surface was coated with gold nanoparticles. Among the above examined strategies, coating amine-SCMPs with gold nanoparticles via strategy I resulted in a better coverage and stronger intensity of absorption bands. Furthermore, results obtained through strategy I showed that decreasing the pH of the solution from 7 to 3 leads to a further red-shift of the plasmon absorption peak for the prepared particles. Moreover, the effect of amine-SCMPs’ zeta potential on the coverage with citrate-coated gold nanoparticles was studied. The results revealed that increasing the EDS concentration from 25 to 90 mM results in a higher coverage of gold nanoparticles on the SCMPs surface.