Amphiphilic poly(organosiloxane) nanospheres as nanoreactors for the synthesis of topologically trapped gold, silver, and palladium colloids

Amphiphilic poly(organosiloxane) nanospheres with different core-shell architectures are employed as passive nanoreactors for the synthesis of noble metal colloids. The amphiphilic poly(organosiloxane) nanospheres, which have diameters between 15 and 40 nm, possess a hydrophilic interior and a hydrophobic shell. Dispersed in organic solvents such as toluene, it has been achieved to transfer hydrophilic noble metal salts through the solvent into the nanospheres by either liquid-liquid or solid-liquid phase transfer. Subsequently, reduction of the noble metal salt with lithium triethylborohydride led to the formation of 2-5 nm sized noble metal colloids. If the network density of the shell of the poly(organosiloxane) nanospheres is small enough, the colloids are topologically trapped inside the nanospheres and stabilized against aggregation. By employing hydrogen tetrachloroaurate(III), silver nitrate, or palladium(II) chloride, it was possible to synthesize topologically trapped gold, silver, or palladium colloids, respectively. The number, the size, and the stability of the colloids depend mainly on (i) the kind of phase transfer chosen, (ii) the amount of hydrophilic groups in the poly(organosiloxane) nanospheres, and (iii) the architecture of the poly(organosiloxane) nanospheres.