APTES modification is conventionally carried out in alcohols for greater control over the silanisation process, however, we find that the produced colloidosomes degrade when placed in or-ganic solvents (see Text S2, Figure ). We therefore carry out the asymmetric APTES modification of the SiO 2 microparticles in water , and use a large excess of APTES to account for losses from self-condensation reactions. We note that the primary objective here is the presence of amine groups for copper complexation on the SiO 2 surface, and thus a smooth monolayer coverage of APTES molecules is of lesser import. To remove excess APTES, weakly attached particles, and any potential side-products from the APTES modification process, the APTES modified colloidosomes are then filtered and washed extensively with twice-distilled water. The colloidosomes are then dispersed in chloroform before filtration to remove the protecting wax masks (Figure ). Finally, the asymmetrically APTES-modified SiO 2 particles are plated with Pt as described previously to obtain Pt-SiO 2 Janus particles (Figures ).