Existence of a Lower Critical Radius for Incorporation of Silica Particles into Zinc during Electro-codeposition

Recently, it was shown that the surface modification of silica particles with -SH functional groups enables their electro-codeposition with zinc. Here, however, we report that no incorporation into Zn can be observed for such modified particles with diameters of <100 nm, while incorporation is possible for particles with diameters of 225 nm and larger. Furthermore, when silica particles are functionalized with mixtures of -SH and -Cl functional groups, which affect the interface energy at the particle/metal interface differently but have similar interfacial energies for the particle/electrolyte interface, it is found that, for successful incorporation of the particles, a minimum amount of -SH functional groups is needed. An explanation for these observations has been derived based on energetic considerations regarding the interfaces involved in the process.